chardbox03
15+ Year Contributor
- 69
- 4
- Feb 26, 2010
-
Lake Orion,
Michigan
I pulled this information from
Stealth 316 - Turbocharger Compressor Flow Maps
ENJOY!!!
Turbocharger's operate as an exhaust driven method of increasing Intake air flow. They differ in one way from superchargers as they do not require a direct mechanical connection to the engine. So, you don't have to worry about snapped blower belts!
The basic operation of a turbocharger can be explained as thus: The exhaust gasses exit the combustion chamber into the header and then enter the turbine housing. When engine speed & load is high enough the exhaust gas hits the turbine with enough momentum to start spinning it. Rapid expansion of the exhaust gasses create a vortex air flow which spins the turbine in excess of 100,000 RPM's. The turbine wheel (the hot wheel) is attached by a shaft to the intake compressor wheel (the cold wheel). When the turbine wheel is sufficiently spinning the compressor wheel spins & draws in fresh air. Air exits under pressure through the rest of the induction system into the cylinders.
The components that make up a turbocharger are:
Housing - Contains the bearings, shaft, turbine seal assembly, compressor seal assembly & lubrication passages. Some Turbo's may also have a coolant passage. This is the part usually right next to the Header.
Compressor Wheel - Located in the Housing in the Intake airstream. Driven by the Turbine Wheel. Has curved fins opposite of the turbine wheel. Air is drawn into the center and forced outward by centrifugal force. THIS AIRFLOW IS WHAT CAUSES BOOST!!!
Turbine Wheel - Located in the housing in the exhaust gas stream. Torque generated by the Turbine Wheel spins the Compressor Wheel. It has curved fins opposite of the compressor wheel that when exhaust gasses hit the fins create a vortex airflow which spin the wheel which spins the Compressor Wheel for BOOST!
The Shaft - Attaches the Turbine Wheel & Compressor Wheel. The shaft is supported by free-floating bearings which are lubricated by engine oil.
Wastegate Valve - Located in Turbine Wheel exhaust airstream. The valve is actuated by manifold BOOST pressure. It is closed when the Turbo is actuated, so that maximum exhaust energy is directed to the Turbine Wheel. The valve opens to allow a certain amount of exhaust gas to to bypass the Turbine Wheel once desired air pressure is reached. The Wastegate Valve can be summed up as - Flow of exhaust reaching Turbine decreases-This reduces Turbine/Compressor speed-Valve stabilizes turbo air pressure-Valve helps prevent detonation (Bad)
Intercooler - Cools air compressed by Turbo before it enters the combustion chamber. This makes the Air intake charge more dense, Denser air contains more Oxygen, More Power! Making air cooler & denser increases horsepower and it helps to resist detonation.
Compressor Bypass Valve - In the CBV the pressurized air is rerouted to the Compressor inlet for reuse. The CBV is actuated under positive vacuum conditions & is closed shut when positive BOOST pressure is reached in the manifold. When going through the gears on your Volvo, a short-lived vacuum condition is created & the CBV opens to direct the pressurized air back to the Turbo in inlet. CBV's are an O.E.M. part that can be found on all Bosch-K & LH-Jet E.F.I. systems.
Those are the basic components of the Turbocharger system.
Fun Stuff -
Boost Controllers come in 2 types -
Manual Boost Controller - Uses an operator adjusted gate valve to control the Boost pressure acting upon the Wastegate. By adjusting the pressure available to the Wastegate, more or less intake BOOST pressure can be generated.
Electronic Boost Controller - Uses a solenoid actuated by a control module that relies on either the vehicle's existing manifold pressure sensor or it can use an auxiliary one. The solenoid controls BOOST pressure acting upon the Wastegate. The controller can be programmed for more than one BOOST level on some units.
Blow-Off Valve - Reduces pressure in the Intake when the throttle is released, preventing air ducting from blowing apart and protecting the Compressor Wheel from Surge. The valve is actuated by a High vacuum signal from behind the closed throttle. This is the component that makes the "whoosh" sound on a turbocharged vehicle.
Bad Stuff -
Turbo Lag - The time required to bring the turbo up to a speed where it can function effectively is called turbo lag. This is noticed as a hesitation in throttle response when coming off idle. This is symptomatic of the time taken for the exhaust system driving the turbine to come to high pressure and for the turbine rotor to overcome its rotational inertia and reach the speed necessary to supply boost pressure. The directly-driven compressor in a supercharger does not suffer this problem. On light loads or at low RPM a turbocharger supplies less boost and the engine is less efficient than a supercharged engine. Lag can be reduced by lowering the rotational inertia of the turbine, for example by using lighter parts to allow the spool-up to happen more quickly. Ceramic turbines are a big help in this direction. Unfortunately, their relative fragility limits the maximum boost they can supply. Another way to reduce lag is to change the aspect ratio of the turbine by reducing the diameter and increasing the gas-flow path-length. Increasing the upper-deck air pressure and improving the wastegate response helps but there are cost increases and reliability disadvantages that car manufacturers are not happy about. Lag is also reduced by using a foil bearing rather than a conventional oil bearing. This reduces friction and contributes to faster acceleration of the turbo's rotating assembly. Variable-nozzle turbochargers eliminate lag. Lag can be reduced with the use of multiple turbochargers. Another common method of equalizing turbo lag is to have the turbine wheel "clipped", or to reduce the surface area of the turbine wheel's rotating blades. By clipping a minute portion off the tip of each blade of the turbine wheel, less restriction is imposed upon the escaping exhaust gases. This imparts less impedance onto the flow of exhaust gases at low RPM, allowing the vehicle to retain more of its low-end torque, but also pushes the effective boost RPM to a slightly higher level. The amount of turbine wheel clipping is highly application-specific. Turbine clipping is measured and specified in degrees. Lag is not to be confused with the boost threshold; however, many publications still make this basic mistake. The boost threshold of a turbo system describes the minimum engine RPM during full-throttle operation at which there is sufficient exhaust flow to the turbo to allow it to generate significant amounts of boost[citation needed]. Newer turbocharger and engine developments have caused boost thresholds to steadily decline to where day-to-day use feels perfectly natural. Putting your foot down at 1200 engine RPM and having no boost until 2000 engine RPM is an example of boost threshold and not lag. If lag was experienced in this situation, the RPM would either not start to rise for a short period of time after the throttle was increased, or increase slowly for a few seconds and then suddenly build up at a greater rate as the turbo become effective. However, the term lag is used erroneously for boost threshold by many manufacturers themselves. Electrical boosting ("E-boosting") is a new technology under development; it uses a high speed electrical motor to drive the turbocharger to speed before exhaust gases are available. The electric motor is about an inch long.
Race cars often utilize an Anti-Lag System to completely eliminate lag at the cost of reduced turbocharger life. On modern diesel engines, this problem is virtually eliminated by utilizing a variable geometry turbocharger.
Damage - Turbochargers can be damaged by dirty or ineffective oil, and most manufacturers recommend more frequent oil changes for turbocharged engines. Many owners and some companies recommend using synthetic oils, which tend to flow more readily when cold and do not break down as quickly as conventional oils. Because the turbocharger will heat when running, many recommend letting the engine idle for one to three minutes before shutting off the engine if the turbocharger was used shortly before stopping (most manufacturers specify a 10-second period of idling before switching off to ensure the turbocharger is running at its idle speed to prevent damage to the bearings when the oil supply is cut off). This lets the turbo rotating assembly cool from the lower exhaust gas temperatures, and ensures that oil is supplied to the turbocharger while the turbine housing and exhaust manifold are still very hot; otherwise coking of the lubricating oil trapped in the unit may occur when the heat soaks into the bearings, causing rapid bearing wear and failure when the car is restarted. Even small particles of burnt oil will accumulate and lead to choking the oil supply and failure. This problem is less pronounced in diesel engines, due to the lower exhaust temperatures and generally slower engine speeds. A turbo timer can keep an engine running for a pre-specified period of time, to automatically provide this cool-down period. Oil coking is also eliminated by foil bearings. A more complex and problematic protective barrier against oil coking is the use of watercooled bearing cartridges. The water boils in the cartridge when the engine is shut off and forms a natural recirculation to drain away the heat. Nevertheless, it is not a good idea to shut the engine off while the turbo and manifold are still glowing. In custom applications utilizing tubular headers rather than cast iron manifolds, the need for a cooldown period is reduced because the lighter headers store much less heat than heavy cast iron manifolds. Turbochargers can also suffer bearing damage and premature failure due to throttle blipping right before shutdown. This may cause the turbo to continue spinning after the engine has shutdown and oil pressure has dropped.
Some Turbocharger differences -
TD04-09B. The stock turbo is sized nicely for the stock motor and the stock fuel system. It is too small for a modified engine.
TD04-13G. This turbo is sold by MHI as the Mitsubishi Sport Turbo Upgrade. This is an excellent turbo for a stock engine. For a modified engine, this turbo will run out of flow at higher RPM - about 17-18 psi boost max at 7000 RPM.
TD04H-15G. This turbo is as large as you want to go with a stock engine. The engine really should be modified to use this turbo. It has good coverage of demand lines (modified engine) but, for the more-demanding driver, it will fall short at the highest flow levels at the highest engine speeds - about 21-23 psi boost max at 7000 RPM. There is little advantage to increasing engine redline to 8000 rpm or above with this turbo because there is only marginally more flow at those engine speeds.
TD04H-16T. This compressor is used in the TD04HL turbo and can be mated to a TD04 turbine housing. It has good coverage of demand lines, almost as good as the 15G. It should be capable of slightly higher pressure ratios at mid RPM and a few more cfm at high rpm. There is little advantage to increasing engine redline to 8000 rpm or above with this turbo because there is only marginally more flow at those engine speeds.
TD04H-18T. This compressor from a Volvo TD04HL turbo is mated to a TD04 turbine. Inappropriate for a stock engine, it has decent demand line coverage for a modified engine. There could be some spool up or surge problems for high boost at low RPM. There is little advantage to increasing engine redline to 8000 rpm or above with this turbo because there is only marginally more flow at those engine speeds.
TD04H-19T. This compressor is used in the TD04HL turbo and can be mated to a TD04 turbine housing. Demand line coverage is excellent for a modified engine. Coverage is better than the TD04H-18T, however, efficiency is generally not as good. This compressor could potentialy allow 24-25 psi boost from 3000 to 8000 RPM with the right exhaust housing and engine modifications. At 7000 RPM, about 450 cfm should be available at 25 psi boost, and about 475 cfm at 8000 RPM at about 24 psi boost. This compressor would be an excellent choice for the 3000GT/Stealth 3.0 L twin-turbo modified engines.
TD05H-14B. This stock turbo from 1st generation 2.0 L single-turbo DSM cars has excellent coverage of demand lines for the 3000GT/Stealth 3.0 L twin-turbo modified engines. At 7000 RPM ~400 cfm effective VAF should be attainable at 20 psi boost and ~450 cfm at 25 psi boost. At 8000 RPM, almost 500 cfm should be available at about 25 psi of boost. The compressor efficiency is considerably less than some of the other turbos that flow similarly at in the upper RPM ranges. A different exhaust manifold is required for the TD05H turbine.
TD05H-14G. The coverage of engine demand lines is similar to that of the TD04-15G. A different exhaust manifold is required for the TD05H turbine. There is little advantage to increasing engine redline to 8000 rpm or above with this turbo because there is only marginally more flow at those engine speeds.
TD05H-16G small wheel. This turbo is a common upgrade for the DSM engine. Demand-line coverage is adequate but shows no advantage over the TD04-15G. A different exhaust manifold is required for the TD05H turbine.
TD05H-16G large wheel. This is another common upgrade choice for the DSM cars. The larger 16G wheel is also found in the TD06H housing. In the TD05H housing, efficiency decreases slightly but flow increases favorably for very high boost levels in our engine. At 5000 to 8000 RPM and above, this turbo offers the highest boost levels and so highest flow levels. Real 500 cfm effective VAF should be attainable with this compressor. Only the TD05H-14B comes close to this performance. A different exhaust manifold is required for the TD05H turbine.
TD05HR-16G6. This is a new upgrade choice for the DSM cars. This turbo is used in the Mitsubishi Lancer Evolution IV to VIII. I think this same wheel is used in the Evo III (but cast in mirror image?), which uses a standard TD05H-7cm2 turbine housing. The TD05HR turbine rotates reverse (the "R" in the designation) of the standard TD05H and has a twin-scroll design. The compressor inducer is a little larger (0.01") than the "big" 16G. So is this the "biggest" 16G? Max flow is better than the 16G "large wheel". Efficiency is much better than the 16G "large wheel". At 5000 to 8000 RPM and above, this turbo offers very high boost levels and so very high flow levels. Real 530 cfm effective VAF should be attainable with this compressor. A different exhaust manifold is required for the TD05H turbine.
TD05H-18G. This flow map is my speculation based on horizontally squeezing and vertically stretching a MHI 20G map. The 16G-large, 18G, and 20G compressor wheels all share the same 2.680" exducer diameter and differ in trim (and perhaps blade design): 50 trim for the 16G-large, 55 trim for the 18G and 60 trim for the 20G. In wheel "families" like this (same exducer size) higher trim usually means more flow and often lower maximum pressure ratio. Sometimes the higher trim wheel may have a bit less maximum efficiency than the lower trim wheel, such as seen in the Garrett T3 series (compare 50-trim and 60-trim wheels). So to make this map I reduced the 20G flow some and increased the maximum PR some. All "G" maps are somewhat similar in appearance so I think this speculative map may be a reasonable guess as to the MHI 18G performance. Coverage of demand lines is not as good as the 14B and 16G-large, but better than with the 20G. However, efficiency is probably better than either of the other 3 wheels. The intersection of the demand lines with the surge line indicates that 20 psi boost may not be reached till about 5500 rpm. This compressor would be good for applications where the engine is in kept in the upper rpm ranges, especially if redline is increased to 8000 rpm or more. A different exhaust manifold is required for the TD05H turbine.
TD06H-20G. This flow map is for the 20G wheel in the TD06H housing. As such it is sized too large for our engines. Flow map coverage of demand lines is poor. Perhaps when installed in the TD05H housing flow map coverage improves. Compare the 16G-large flow maps in the "Raw" section above for the TD05H and TD06H housings. Notice that the 16G-large in the TD05H housing has lost some efficiency. However, the character of the pattern has changed to improve demand line coverage and to produce higher maximum pressure ratios. A different exhaust manifold is required for the TD05H turbine.
T3 60-Trim. This Garrett compressor and housing is mated to a TD04 exhaust housing in the GT368SX turbo (sold by GT PRO). The GT368SX may also use the T3 Super 60-Trim (the flow maps are very similar). Coverage of demand lines is good overall with very good coverage at the highest RPM, even up to 8000+. Real 450-500 cfm effective VAF should be attainable with this turbo. There could be some spool up or surge problems for high boost at low RPM.
IHI RHF55. This is a ball bearing turbo made by IHI and used on Subaru rally cars. Coverage of demand lines is excellent at lower RPM, but the flow limits suggest it may be lacking at higher RPM. I've never seen one used on our cars, and actual performance may be better than the flow limits suggest at higher RPM. A different exhaust manifold is required for the IHI turbine. If somebody has seen one on a VOLVO P.M. me a picture.
GT28RS 62-Trim. This is Garrett's "Disco Potato". I had originally thought this turbo's nickname came from the shape of its compressor flow map. Now that manifolds are being made to accept Garrett turbo flanges, the new ball bearing GT series turbos from Garrett can be considered as viable upgrade options for our engines. And the "Disco Potato" would make a good choice. While it cannot reach the lofty pressure ratios of the GT35 48-trim, it should hold 25 psi boost from 5500 to 8000 rpm and has better demand line coverage than the GT35 48-trim. This compressor wheel is similar in size to the T3 60-trim compressor wheel.
GT35 48-Trim 71-mm. According to my best information, this Garrett GT35 48-trim compressor wheel in a Garrett T04B housing (with a ball bearing CHRA) is mated to a MHI TD05 7cm2 exhaust housing in the "GT30R" turbo sold by AAM. Coverage of demand lines is good from 5000 RPM and above. Efficiency is excellent where demand lines fall on the flow map. This turbo has the highest maximum PR of any shown here (GT42s excluded), capable of 3.4 PR (about 34 psi boost before pressure losses are accounted for). Over 500 cfm effective VAF should be attainable with this turbo at 8000+ engine RPM. Spool up could be a little slow (5 psi boost at 3000 RPM and 10 psi boost at 4000 RPM). However, 20 psi boost should be available at 5000 RPM, and almost 30 psi boost at 6000 RPM. This may be an excellent drag and high-performance street turbo.
GT35 52-Trim 76-mm. The GT35 48-trim 71-mm is a better choice because it has better demand line coverage and efficiency than the 52-trim wheel. Spool up should be faster with the 48-trim. The GT35 52-trim 76-mm, like the MHI 20G, is an example of a compressor than can work for our engines, and sometimes quite well under drag-race conditions, but is sized too large for everyday driving and boost levels. There are other turbos that have similar maximum flow in our engines (500-550 cfm each turbo) that have better demand line coverage and so are better suited for everyday driving where flow levels rarely exceed 400-450 cfm.
T4 46-Trim. This Garrett compressor is better suited for 2.0-2.5 L engines. It might be OK for drag race and 8000+ engine RPM use. The GT35 48 Trim, GT28RS 62 Trim, or even the TD05-14B would be better choices.
(Thanks to Mr. Lucius of Stealth fame for the Turbo differences)
badvlvo wanted a Holset list so here goes. First here is how to read a Holset tag -
(A) Assembly Number
Assembly Number for the turbocharger is the most useful number for service purposes.
(B) Serial Number
Serial Number is unique to your turbocharger. This number can be used to identify which turbocharger you have.
(C) Part Number
Part Number is the number given to the turbocharger by the engine manufacturer. This number will be in all the engine manufacturers' books. There may be more than one Part Number for each Assembly Number (A).
(D) Turbocharger Type
Turbocharger Type describes the model or frame size of your Holset turbocharger.
Some quick little things about Holset turbo's -
Holset turbo's are designed to handle HIGH RPM's, it should also be noted that Holset's make an incredible amount of BOOST. They sky is the limit with Holset turbo's. An H1C & HX35 have the exact same turbine wheels. As does the H1E & HX40. The X in HX signifies it being a divorced housing (split housing) turbo an HY is single entry. The biggest differences were that the older turbos rarely came with internal wastegates where the later HX series were more wastegated than not (mostly on the HX35) the HX also have the ported shroud compressor covers (aka "anti surge" housings). The 16cm and up housings were never offered with a wastegate. Another thing to know is HX35, HX40 etc. is a frame size. Much like Garrett with their T3, T4, T6 designations. There could be several different compressor wheel options offered within that frame size. this is most common with the H1E & HX40. The most sought after HX40 is the 6 blade compressor wheel which is commonly found on the VOLVO HX40's it flows quite a bit more than the standard 7 or 8 blade wheels.
The Holset Turbo models are - H1C, H1E, H2C, H2D, H2E, HX30, HX35, HX40, HX50, HX55, HX60W, HX80 & HX82.
The easiest way to get Holset turbo's cheap is...go to your local pick-a-part find a Turbo diesel Dodge and yank it. Here is a handy little guide from Adam to find them.
H1C - The H1C turbo was used from 1989-1993. They have a BOOST range of 15-25 PSI. The wastegates range from 17-22 PSI.
WH1C - The WH1C turbo was used for 1 year. 1994. It has a BOOST range of 15-18 PSI, with a wastegate PSI of 17.
HX35W - The HX35W is the longest-lived Holset Turbo. It was used from 1994 until well...you can still find them in some Dodges. It has a BOOST range of 15-23 PSI. The wastegate ranges from 17-26 PSI.
HY35W - Another 1 year only turbo. This one deserves a special merit for the fact that it has a 9 sq. cm. Turbine Housing! That is tiny folks! It has a max BOOST of 20.5 PSI. The wastegate is set at 23 PSI.
Hope this helped!!!
Stealth 316 - Turbocharger Compressor Flow Maps
ENJOY!!!
Turbocharger's operate as an exhaust driven method of increasing Intake air flow. They differ in one way from superchargers as they do not require a direct mechanical connection to the engine. So, you don't have to worry about snapped blower belts!
The basic operation of a turbocharger can be explained as thus: The exhaust gasses exit the combustion chamber into the header and then enter the turbine housing. When engine speed & load is high enough the exhaust gas hits the turbine with enough momentum to start spinning it. Rapid expansion of the exhaust gasses create a vortex air flow which spins the turbine in excess of 100,000 RPM's. The turbine wheel (the hot wheel) is attached by a shaft to the intake compressor wheel (the cold wheel). When the turbine wheel is sufficiently spinning the compressor wheel spins & draws in fresh air. Air exits under pressure through the rest of the induction system into the cylinders.
The components that make up a turbocharger are:
Housing - Contains the bearings, shaft, turbine seal assembly, compressor seal assembly & lubrication passages. Some Turbo's may also have a coolant passage. This is the part usually right next to the Header.
Compressor Wheel - Located in the Housing in the Intake airstream. Driven by the Turbine Wheel. Has curved fins opposite of the turbine wheel. Air is drawn into the center and forced outward by centrifugal force. THIS AIRFLOW IS WHAT CAUSES BOOST!!!
Turbine Wheel - Located in the housing in the exhaust gas stream. Torque generated by the Turbine Wheel spins the Compressor Wheel. It has curved fins opposite of the compressor wheel that when exhaust gasses hit the fins create a vortex airflow which spin the wheel which spins the Compressor Wheel for BOOST!
The Shaft - Attaches the Turbine Wheel & Compressor Wheel. The shaft is supported by free-floating bearings which are lubricated by engine oil.
Wastegate Valve - Located in Turbine Wheel exhaust airstream. The valve is actuated by manifold BOOST pressure. It is closed when the Turbo is actuated, so that maximum exhaust energy is directed to the Turbine Wheel. The valve opens to allow a certain amount of exhaust gas to to bypass the Turbine Wheel once desired air pressure is reached. The Wastegate Valve can be summed up as - Flow of exhaust reaching Turbine decreases-This reduces Turbine/Compressor speed-Valve stabilizes turbo air pressure-Valve helps prevent detonation (Bad)
Intercooler - Cools air compressed by Turbo before it enters the combustion chamber. This makes the Air intake charge more dense, Denser air contains more Oxygen, More Power! Making air cooler & denser increases horsepower and it helps to resist detonation.
Compressor Bypass Valve - In the CBV the pressurized air is rerouted to the Compressor inlet for reuse. The CBV is actuated under positive vacuum conditions & is closed shut when positive BOOST pressure is reached in the manifold. When going through the gears on your Volvo, a short-lived vacuum condition is created & the CBV opens to direct the pressurized air back to the Turbo in inlet. CBV's are an O.E.M. part that can be found on all Bosch-K & LH-Jet E.F.I. systems.
Those are the basic components of the Turbocharger system.
Fun Stuff -
Boost Controllers come in 2 types -
Manual Boost Controller - Uses an operator adjusted gate valve to control the Boost pressure acting upon the Wastegate. By adjusting the pressure available to the Wastegate, more or less intake BOOST pressure can be generated.
Electronic Boost Controller - Uses a solenoid actuated by a control module that relies on either the vehicle's existing manifold pressure sensor or it can use an auxiliary one. The solenoid controls BOOST pressure acting upon the Wastegate. The controller can be programmed for more than one BOOST level on some units.
Blow-Off Valve - Reduces pressure in the Intake when the throttle is released, preventing air ducting from blowing apart and protecting the Compressor Wheel from Surge. The valve is actuated by a High vacuum signal from behind the closed throttle. This is the component that makes the "whoosh" sound on a turbocharged vehicle.
Bad Stuff -
Turbo Lag - The time required to bring the turbo up to a speed where it can function effectively is called turbo lag. This is noticed as a hesitation in throttle response when coming off idle. This is symptomatic of the time taken for the exhaust system driving the turbine to come to high pressure and for the turbine rotor to overcome its rotational inertia and reach the speed necessary to supply boost pressure. The directly-driven compressor in a supercharger does not suffer this problem. On light loads or at low RPM a turbocharger supplies less boost and the engine is less efficient than a supercharged engine. Lag can be reduced by lowering the rotational inertia of the turbine, for example by using lighter parts to allow the spool-up to happen more quickly. Ceramic turbines are a big help in this direction. Unfortunately, their relative fragility limits the maximum boost they can supply. Another way to reduce lag is to change the aspect ratio of the turbine by reducing the diameter and increasing the gas-flow path-length. Increasing the upper-deck air pressure and improving the wastegate response helps but there are cost increases and reliability disadvantages that car manufacturers are not happy about. Lag is also reduced by using a foil bearing rather than a conventional oil bearing. This reduces friction and contributes to faster acceleration of the turbo's rotating assembly. Variable-nozzle turbochargers eliminate lag. Lag can be reduced with the use of multiple turbochargers. Another common method of equalizing turbo lag is to have the turbine wheel "clipped", or to reduce the surface area of the turbine wheel's rotating blades. By clipping a minute portion off the tip of each blade of the turbine wheel, less restriction is imposed upon the escaping exhaust gases. This imparts less impedance onto the flow of exhaust gases at low RPM, allowing the vehicle to retain more of its low-end torque, but also pushes the effective boost RPM to a slightly higher level. The amount of turbine wheel clipping is highly application-specific. Turbine clipping is measured and specified in degrees. Lag is not to be confused with the boost threshold; however, many publications still make this basic mistake. The boost threshold of a turbo system describes the minimum engine RPM during full-throttle operation at which there is sufficient exhaust flow to the turbo to allow it to generate significant amounts of boost[citation needed]. Newer turbocharger and engine developments have caused boost thresholds to steadily decline to where day-to-day use feels perfectly natural. Putting your foot down at 1200 engine RPM and having no boost until 2000 engine RPM is an example of boost threshold and not lag. If lag was experienced in this situation, the RPM would either not start to rise for a short period of time after the throttle was increased, or increase slowly for a few seconds and then suddenly build up at a greater rate as the turbo become effective. However, the term lag is used erroneously for boost threshold by many manufacturers themselves. Electrical boosting ("E-boosting") is a new technology under development; it uses a high speed electrical motor to drive the turbocharger to speed before exhaust gases are available. The electric motor is about an inch long.
Race cars often utilize an Anti-Lag System to completely eliminate lag at the cost of reduced turbocharger life. On modern diesel engines, this problem is virtually eliminated by utilizing a variable geometry turbocharger.
Damage - Turbochargers can be damaged by dirty or ineffective oil, and most manufacturers recommend more frequent oil changes for turbocharged engines. Many owners and some companies recommend using synthetic oils, which tend to flow more readily when cold and do not break down as quickly as conventional oils. Because the turbocharger will heat when running, many recommend letting the engine idle for one to three minutes before shutting off the engine if the turbocharger was used shortly before stopping (most manufacturers specify a 10-second period of idling before switching off to ensure the turbocharger is running at its idle speed to prevent damage to the bearings when the oil supply is cut off). This lets the turbo rotating assembly cool from the lower exhaust gas temperatures, and ensures that oil is supplied to the turbocharger while the turbine housing and exhaust manifold are still very hot; otherwise coking of the lubricating oil trapped in the unit may occur when the heat soaks into the bearings, causing rapid bearing wear and failure when the car is restarted. Even small particles of burnt oil will accumulate and lead to choking the oil supply and failure. This problem is less pronounced in diesel engines, due to the lower exhaust temperatures and generally slower engine speeds. A turbo timer can keep an engine running for a pre-specified period of time, to automatically provide this cool-down period. Oil coking is also eliminated by foil bearings. A more complex and problematic protective barrier against oil coking is the use of watercooled bearing cartridges. The water boils in the cartridge when the engine is shut off and forms a natural recirculation to drain away the heat. Nevertheless, it is not a good idea to shut the engine off while the turbo and manifold are still glowing. In custom applications utilizing tubular headers rather than cast iron manifolds, the need for a cooldown period is reduced because the lighter headers store much less heat than heavy cast iron manifolds. Turbochargers can also suffer bearing damage and premature failure due to throttle blipping right before shutdown. This may cause the turbo to continue spinning after the engine has shutdown and oil pressure has dropped.
Some Turbocharger differences -
TD04-09B. The stock turbo is sized nicely for the stock motor and the stock fuel system. It is too small for a modified engine.
TD04-13G. This turbo is sold by MHI as the Mitsubishi Sport Turbo Upgrade. This is an excellent turbo for a stock engine. For a modified engine, this turbo will run out of flow at higher RPM - about 17-18 psi boost max at 7000 RPM.
TD04H-15G. This turbo is as large as you want to go with a stock engine. The engine really should be modified to use this turbo. It has good coverage of demand lines (modified engine) but, for the more-demanding driver, it will fall short at the highest flow levels at the highest engine speeds - about 21-23 psi boost max at 7000 RPM. There is little advantage to increasing engine redline to 8000 rpm or above with this turbo because there is only marginally more flow at those engine speeds.
TD04H-16T. This compressor is used in the TD04HL turbo and can be mated to a TD04 turbine housing. It has good coverage of demand lines, almost as good as the 15G. It should be capable of slightly higher pressure ratios at mid RPM and a few more cfm at high rpm. There is little advantage to increasing engine redline to 8000 rpm or above with this turbo because there is only marginally more flow at those engine speeds.
TD04H-18T. This compressor from a Volvo TD04HL turbo is mated to a TD04 turbine. Inappropriate for a stock engine, it has decent demand line coverage for a modified engine. There could be some spool up or surge problems for high boost at low RPM. There is little advantage to increasing engine redline to 8000 rpm or above with this turbo because there is only marginally more flow at those engine speeds.
TD04H-19T. This compressor is used in the TD04HL turbo and can be mated to a TD04 turbine housing. Demand line coverage is excellent for a modified engine. Coverage is better than the TD04H-18T, however, efficiency is generally not as good. This compressor could potentialy allow 24-25 psi boost from 3000 to 8000 RPM with the right exhaust housing and engine modifications. At 7000 RPM, about 450 cfm should be available at 25 psi boost, and about 475 cfm at 8000 RPM at about 24 psi boost. This compressor would be an excellent choice for the 3000GT/Stealth 3.0 L twin-turbo modified engines.
TD05H-14B. This stock turbo from 1st generation 2.0 L single-turbo DSM cars has excellent coverage of demand lines for the 3000GT/Stealth 3.0 L twin-turbo modified engines. At 7000 RPM ~400 cfm effective VAF should be attainable at 20 psi boost and ~450 cfm at 25 psi boost. At 8000 RPM, almost 500 cfm should be available at about 25 psi of boost. The compressor efficiency is considerably less than some of the other turbos that flow similarly at in the upper RPM ranges. A different exhaust manifold is required for the TD05H turbine.
TD05H-14G. The coverage of engine demand lines is similar to that of the TD04-15G. A different exhaust manifold is required for the TD05H turbine. There is little advantage to increasing engine redline to 8000 rpm or above with this turbo because there is only marginally more flow at those engine speeds.
TD05H-16G small wheel. This turbo is a common upgrade for the DSM engine. Demand-line coverage is adequate but shows no advantage over the TD04-15G. A different exhaust manifold is required for the TD05H turbine.
TD05H-16G large wheel. This is another common upgrade choice for the DSM cars. The larger 16G wheel is also found in the TD06H housing. In the TD05H housing, efficiency decreases slightly but flow increases favorably for very high boost levels in our engine. At 5000 to 8000 RPM and above, this turbo offers the highest boost levels and so highest flow levels. Real 500 cfm effective VAF should be attainable with this compressor. Only the TD05H-14B comes close to this performance. A different exhaust manifold is required for the TD05H turbine.
TD05HR-16G6. This is a new upgrade choice for the DSM cars. This turbo is used in the Mitsubishi Lancer Evolution IV to VIII. I think this same wheel is used in the Evo III (but cast in mirror image?), which uses a standard TD05H-7cm2 turbine housing. The TD05HR turbine rotates reverse (the "R" in the designation) of the standard TD05H and has a twin-scroll design. The compressor inducer is a little larger (0.01") than the "big" 16G. So is this the "biggest" 16G? Max flow is better than the 16G "large wheel". Efficiency is much better than the 16G "large wheel". At 5000 to 8000 RPM and above, this turbo offers very high boost levels and so very high flow levels. Real 530 cfm effective VAF should be attainable with this compressor. A different exhaust manifold is required for the TD05H turbine.
TD05H-18G. This flow map is my speculation based on horizontally squeezing and vertically stretching a MHI 20G map. The 16G-large, 18G, and 20G compressor wheels all share the same 2.680" exducer diameter and differ in trim (and perhaps blade design): 50 trim for the 16G-large, 55 trim for the 18G and 60 trim for the 20G. In wheel "families" like this (same exducer size) higher trim usually means more flow and often lower maximum pressure ratio. Sometimes the higher trim wheel may have a bit less maximum efficiency than the lower trim wheel, such as seen in the Garrett T3 series (compare 50-trim and 60-trim wheels). So to make this map I reduced the 20G flow some and increased the maximum PR some. All "G" maps are somewhat similar in appearance so I think this speculative map may be a reasonable guess as to the MHI 18G performance. Coverage of demand lines is not as good as the 14B and 16G-large, but better than with the 20G. However, efficiency is probably better than either of the other 3 wheels. The intersection of the demand lines with the surge line indicates that 20 psi boost may not be reached till about 5500 rpm. This compressor would be good for applications where the engine is in kept in the upper rpm ranges, especially if redline is increased to 8000 rpm or more. A different exhaust manifold is required for the TD05H turbine.
TD06H-20G. This flow map is for the 20G wheel in the TD06H housing. As such it is sized too large for our engines. Flow map coverage of demand lines is poor. Perhaps when installed in the TD05H housing flow map coverage improves. Compare the 16G-large flow maps in the "Raw" section above for the TD05H and TD06H housings. Notice that the 16G-large in the TD05H housing has lost some efficiency. However, the character of the pattern has changed to improve demand line coverage and to produce higher maximum pressure ratios. A different exhaust manifold is required for the TD05H turbine.
T3 60-Trim. This Garrett compressor and housing is mated to a TD04 exhaust housing in the GT368SX turbo (sold by GT PRO). The GT368SX may also use the T3 Super 60-Trim (the flow maps are very similar). Coverage of demand lines is good overall with very good coverage at the highest RPM, even up to 8000+. Real 450-500 cfm effective VAF should be attainable with this turbo. There could be some spool up or surge problems for high boost at low RPM.
IHI RHF55. This is a ball bearing turbo made by IHI and used on Subaru rally cars. Coverage of demand lines is excellent at lower RPM, but the flow limits suggest it may be lacking at higher RPM. I've never seen one used on our cars, and actual performance may be better than the flow limits suggest at higher RPM. A different exhaust manifold is required for the IHI turbine. If somebody has seen one on a VOLVO P.M. me a picture.
GT28RS 62-Trim. This is Garrett's "Disco Potato". I had originally thought this turbo's nickname came from the shape of its compressor flow map. Now that manifolds are being made to accept Garrett turbo flanges, the new ball bearing GT series turbos from Garrett can be considered as viable upgrade options for our engines. And the "Disco Potato" would make a good choice. While it cannot reach the lofty pressure ratios of the GT35 48-trim, it should hold 25 psi boost from 5500 to 8000 rpm and has better demand line coverage than the GT35 48-trim. This compressor wheel is similar in size to the T3 60-trim compressor wheel.
GT35 48-Trim 71-mm. According to my best information, this Garrett GT35 48-trim compressor wheel in a Garrett T04B housing (with a ball bearing CHRA) is mated to a MHI TD05 7cm2 exhaust housing in the "GT30R" turbo sold by AAM. Coverage of demand lines is good from 5000 RPM and above. Efficiency is excellent where demand lines fall on the flow map. This turbo has the highest maximum PR of any shown here (GT42s excluded), capable of 3.4 PR (about 34 psi boost before pressure losses are accounted for). Over 500 cfm effective VAF should be attainable with this turbo at 8000+ engine RPM. Spool up could be a little slow (5 psi boost at 3000 RPM and 10 psi boost at 4000 RPM). However, 20 psi boost should be available at 5000 RPM, and almost 30 psi boost at 6000 RPM. This may be an excellent drag and high-performance street turbo.
GT35 52-Trim 76-mm. The GT35 48-trim 71-mm is a better choice because it has better demand line coverage and efficiency than the 52-trim wheel. Spool up should be faster with the 48-trim. The GT35 52-trim 76-mm, like the MHI 20G, is an example of a compressor than can work for our engines, and sometimes quite well under drag-race conditions, but is sized too large for everyday driving and boost levels. There are other turbos that have similar maximum flow in our engines (500-550 cfm each turbo) that have better demand line coverage and so are better suited for everyday driving where flow levels rarely exceed 400-450 cfm.
T4 46-Trim. This Garrett compressor is better suited for 2.0-2.5 L engines. It might be OK for drag race and 8000+ engine RPM use. The GT35 48 Trim, GT28RS 62 Trim, or even the TD05-14B would be better choices.
(Thanks to Mr. Lucius of Stealth fame for the Turbo differences)
badvlvo wanted a Holset list so here goes. First here is how to read a Holset tag -
(A) Assembly Number
Assembly Number for the turbocharger is the most useful number for service purposes.
(B) Serial Number
Serial Number is unique to your turbocharger. This number can be used to identify which turbocharger you have.
(C) Part Number
Part Number is the number given to the turbocharger by the engine manufacturer. This number will be in all the engine manufacturers' books. There may be more than one Part Number for each Assembly Number (A).
(D) Turbocharger Type
Turbocharger Type describes the model or frame size of your Holset turbocharger.
Some quick little things about Holset turbo's -
Holset turbo's are designed to handle HIGH RPM's, it should also be noted that Holset's make an incredible amount of BOOST. They sky is the limit with Holset turbo's. An H1C & HX35 have the exact same turbine wheels. As does the H1E & HX40. The X in HX signifies it being a divorced housing (split housing) turbo an HY is single entry. The biggest differences were that the older turbos rarely came with internal wastegates where the later HX series were more wastegated than not (mostly on the HX35) the HX also have the ported shroud compressor covers (aka "anti surge" housings). The 16cm and up housings were never offered with a wastegate. Another thing to know is HX35, HX40 etc. is a frame size. Much like Garrett with their T3, T4, T6 designations. There could be several different compressor wheel options offered within that frame size. this is most common with the H1E & HX40. The most sought after HX40 is the 6 blade compressor wheel which is commonly found on the VOLVO HX40's it flows quite a bit more than the standard 7 or 8 blade wheels.
The Holset Turbo models are - H1C, H1E, H2C, H2D, H2E, HX30, HX35, HX40, HX50, HX55, HX60W, HX80 & HX82.
The easiest way to get Holset turbo's cheap is...go to your local pick-a-part find a Turbo diesel Dodge and yank it. Here is a handy little guide from Adam to find them.
H1C - The H1C turbo was used from 1989-1993. They have a BOOST range of 15-25 PSI. The wastegates range from 17-22 PSI.
WH1C - The WH1C turbo was used for 1 year. 1994. It has a BOOST range of 15-18 PSI, with a wastegate PSI of 17.
HX35W - The HX35W is the longest-lived Holset Turbo. It was used from 1994 until well...you can still find them in some Dodges. It has a BOOST range of 15-23 PSI. The wastegate ranges from 17-26 PSI.
HY35W - Another 1 year only turbo. This one deserves a special merit for the fact that it has a 9 sq. cm. Turbine Housing! That is tiny folks! It has a max BOOST of 20.5 PSI. The wastegate is set at 23 PSI.
Hope this helped!!!
