Help with turbo after install

[SLOWKID]

My car is pretty much stock. I Had a 14 b turbo on it but it was shot. i got a 16g turbo the install went fine sounds and runs good till i hit about 4k at wot then it feels likes fuel cut.before the new turbo everthing ran fine. I am a newbie so please help. I know i have a bad exhaust leak at the flex section,getting new exhaust friday. i don't think its a boost leak. what could cause this and what sould i do to fix it.
thanks
slowkid

 

[turbosax2]

My car is pretty much stock. I Had a 14 b turbo on it but it was shot. i got a 16g turbo the install went fine sounds and runs good till i hit about 4k at wot then it feels likes fuel cut.before the new turbo everthing ran fine. I am a newbie so please help. I know i have a bad exhaust leak at the flex section,getting new exhaust friday. i don't think its a boost leak. what could cause this and what sould i do to fix it.
thanks
slowkid

Why don't you think it's a boost leak? Do a boost leak test to be sure.

 

[SLOWKID]

I did do a boost leak test. i'm still running on stock boost. could the new turbo increase my stock boost

 

[Splitpi]

And the results of the boost leak test are...? How is the vacuum line ran to the wastegate?

 

[sd_ff22]

A boost leak test is the first thing you should do anytime you mess with your turbo and intercooler setup.
best to be safe.
plus its just smart to do.

 

[VPrime]

Your mods in your profile dont say any thing about fuel.. If your running a 16g on stock fuel system... thats your problem.

 

[forcefed 95]

Do you have an aftermarket boost gauge. If so what does it read when you expirence your problem. Cause you are more than likly getting mad boost creep with the 16g and full 3in exhaust. This would cause you hit fuel cut depending on how your boost creeps to. Just a thought.

 

[CrazyGSX]

you need to up grade your fuel pump, Fuel Injectors and Regulator. then get your self a fuel computer

 

[Splitpi]

I'm running a 16G with stock fuel and 3" exhaust, with no issues. The issues result because of exceeding stock boost levels (which results in more air flow from the turbo and produce more power). The OP needs to explain his setup more. But at stock boost on a 16G, 14b or T25 it isn't an issue... and I mean ~9 to 11 psi.

 

[sd_ff22]

I'm running a 16G with stock fuel and 3" exhaust, with no issues. The issues result because of exceeding stock boost levels (which results in more air flow from the turbo and produce more power). The OP needs to explain his setup more. But at stock boost on a 16G, 14b or T25 it isn't an issue... and I mean ~9 to 11 psi.

Just be careful there bro.
you may think you are having no issues but anytime you add more air than the system thinks you are adding, you will run lean.
you might be within the realm of the stock injectors at a low boost level, but it will be dangerous at higher rpms under load.
Just fyi.

 

[BoostFrenzy]

I did do a boost leak test. i'm still running on stock boost. could the new turbo increase my stock boost

You need to turn down your boost if you are still on stock fuel. It doesn't matter if it is stock boost pressure because the turbo is larger. So say 12psi on a 14b and 12psi on a 16g, the latter needing much more fuel because of the increased amount of air.

Its really simple actually. Think of it like this: If you have a 20oz. bottle and a 1 liter bottle pressurized with air to 12psi, which one will have more air in it? (of course the larger 1 liter bottle).

So either upgrade your fuel system to support its current boost level, or turn down the boost to compensate for its larger size.

 

[Splitpi]

Just be careful there bro.
you may think you are having no issues but anytime you add more air than the system thinks you are adding, you will run lean.
you might be within the realm of the stock injectors at a low boost level, but it will be dangerous at higher rpms under load.
Just fyi.

Not really.

9.5 psi of boost equates to ~ 1.6 to 1.8 pressure ratio or ~25.3 to 21.4 psia at the manifold (Map) depending on intercooling loss and atmosphere.

Using Wa = (Map x Ve x N/2 x Vd)/ (R*(460+Tm)) where:
Wa = Air Flow in lb/min
Ve = Volumetric Efficiency
N = RPM's
Vd = Displacement in CI
R = 639.6 constant
Tm = Intake Manifold Temp

and plugging in values I know (for worst case on a 16G, i.e. I ramped the turbine to far right choke line of the map):

Wa = (25.3 x 0.68 x 7000/2 x 122) / (639.6 x (460 + 92)) = 7,346,108 / 353,059.2 = 20.8 lb/min

Calculating for estimated HP:

hp = Wa / (A/F x BSFC/60) = 20.8 / (10.5 x 0.55 /60) = 216 hp at the crank.
Assumptions:
My BSFC is 0.55, this varies from engine to engine. You need to dyno your car and measure the fuel usage to calculate it more accurately as its lbs of fuel per horspower hour. But generally turbo engines are in the neighborhood of 0.50 to 0.60 according to Garrett.

Air Fuel Ratio (A/F) is assumed to be leaned out from the stock pig rich to ~10.5 when under full boost. Most people like to state 11:1 is ideal, but 10.5:1 is richer than that and being conservative.

With as high as 245.2 hp at the crank under ideal Ve of 0.77 (which is not attainable from the any of these turbo at 1.6 to 1.8 pressure ratio and 23.6 lb/min psia or 341.6 CFM (amount of airflow necessary for 245.2 hp)).

Thats pretty much stock. And my DSMLink reports similarly with the Injector Duty Cycle.

On a side note: Can anyone shed light on the Injector calculations involving 1:1 matching AFPR to Boost pressure. Meaning that at 9.5 psi of boost (above atmosphere) on a static 43.5 psi fuel pressure, the actual fuel pressure should be 53 psi at that boost level... correct?

So If I take the equation:

hp = ((injector size)*(Number of Injectors)*0.8)/(BSFC)

and factor in the increased fuel pressure do to matching boost pressure:

hp = ((sqrt((New Pressure) / (Old Pressure)) * (injector size)) * (Number of Injectors) *.0.8) / (BSFC)

Is that correct to compensate?

 

[CrazyGSX]

ok for the turbo to be at stock boost it will be ok. you need to always look at you psi boost gauge to make sure your under the right boost levels. when you step on the gas herd you see you my have to much boost. you would need to port out your exhaust 02 housing or but a bigger one. every one seems to do this then they buy a evo 16g. and then reset you boost controller.

 

[Splitpi]

ok for the turbo to be at stock boost it will be ok. you need to always look at you psi boost gauge to make sure your under the right boost levels. when you step on the gas herd you see you my have to much boost. you would need to port out your exhaust 02 housing or but a bigger one. every one seems to do this then they buy a evo 16g. and then reset you boost controller.

Sage advice. Always port if possible. Gasket match the Exhaust manifold where it meets the head as well as where it matches the turbo. A Evo 3 16G has a larger exhaust gas inlet than a 1G or even a 2G exhaust manifold. So to make true use of it, port the exhaust manifold to match the turbo's size. Then on the exhaust exit side of the turbo is the O2 housing. Port that to match to the turbo to O2 housing gasket. Pay particular attention to increasing the size of the WasteGate passage.

Increasing the Wastegate passage size by porting it will allow the wastegate to flow more exhaust gasses through the passage rather than through the turbine, this will help combat boost spike. Particularly on a 3" exhaust. My car doesn't have boost creep with my ported O2 housing and 3" exhaust on a big 16G. My greddy boost gauge has peek hold and it hits rock solid and stays at its maximum. Of course though, I'm only running 9.5 psi and this may change at a higher boost level due to increased exhaust gasses.

Moral of the story is that porting is practically free to do, if you have access to a decent air compressor. It just requires a few hours of your time.