Do you have a stock exhaust? Neither of those three cars have the same turbo, intake pipe, or exhaust and the X is a whole different engine, the MR Has a different head design/cam profile. So they are bound to sound different... What exactally is the problem.

How are you measuring exhaust flow? Thrse are all apples to oranges to pears

UrbanSmoker said:

Do you have a stock exhaust? Neither of those three cars have the same turbo, intake pipe, or exhaust and the X is a whole different engine, the MR Has a different head design/cam profile. So they are bound to sound different... What exactally is the problem.

How are you measuring exhaust flow? Thrse are all apples to oranges to pears

Click to expand...

You could not have read anything I typed......
I am talking exhaust flow at IDLE - FLOW, not sound. At idle with ~3" exhaust on all 3 cars at the same rpm, it ABSOLUTELY is apples to apples (2L, 800 rpm, turbo, 3" exhaust, no cats on all cars).

Do you have a wideband installed on the car? If so what is it doing when you have the off idle stumble?

Unless you have measured the cfm, and temp of the exhaust gas, there is no way to judge it's flow accurately. If there is a straight exhaust on the dsm the exhaust gasses are probably hotter coming out of the tail pipe, making the volume higher for a given mass.

donniekak said:

Do you have a wideband installed on the car? If so what is it doing when you have the off idle stumble?

Unless you have measured the cfm, and temp of the exhaust gas, there is no way to judge it's flow accurately. If there is a straight exhaust on the dsm the exhaust gasses are probably hotter coming out of the tail pipe, making the volume higher for a given mass.

Click to expand...

Both Evo 9 and DSM have 3" TBE no cat - should be little difference in flow restriction.... Off idle, the car goes rich based on wideband and evoscan, but it is not 100% reproducible - sometimes it does not go below ~12:1.

I too am curious as to how you know the exhaust flow is roughly twice. Are you just comparing the MAF sensor readings? It's seems crazy that the dsm could be consuming twice as much air as the other 2 at the same rpm and throttle position.

mjdarg said:

I too am curious as to how you know the exhaust flow is roughly twice. Are you just comparing the MAF sensor readings? It's seems crazy that the dsm could be consuming twice as much air as the other 2 at the same rpm and throttle position.

Click to expand...

GSX MAF is ~70hz compared to ~43hz on the evo ix at 750 - 800 rpm using evoscan (I have black box ecu in GSX).

The MAF's are quite different, hence the different Hz counts. You can look up the comp curves and once factored decide if there really if that much difference in airflow or if it's just the two measuring devices.

So the only method you used to measure and compare exhaust flow has been looking at the Hz count of different generation/models of airflow sensors at idle rpm?

curt-s said:

So the only method you used to measure and compare exhaust flow has been looking at the Hz count of different generation/models of airflow sensors at idle rpm?

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The Hz count on the 2g has increased from the low 40's to 70's with no apparent reason(s). Also, WRT comparing the maf counts of the Evo 9, Evo 10, and 2g at IDLE, the voltage (or Hz) to flow calibration doesn't factor in - all 3 motors should be moving very close to the same amount of air at idle, and there are many, many evoscan logs showing low 40's hz for all of these motors at idle.

My issue is the 2g is moving 70 hz at idle, which is about 2x 'normal'. The flow from the exhaust confirms this. Although no one here will understand this technology, I have employed a Fluke vanometer/pitot tube to attempt to measure relative flow between the 2g and Evo9 (the 10 has dual exhaust and I'm not drilling a hole in it before the split), but the actual value from each car is meaningless because I have not engineered the pitot tube to the pipe size. That stated, the relative difference between the 2 cars IS meaningful since I used the same pitot tube on both cars, hence my ~2x difference in flow.

All three cars are from different time periods with different turbos and different maf tech, it's still not apples to apples

Might as well be comparing "flow" of your mitsus to a Honda of same mods 3" tbe etc, right? Should all be flowing the same? No, different motors. Different metering systems. Like i said before before you called me a kid living in my parents basement or what ever. ( you obviously know nothing to be making such statements)

The dsm had a different head design then the evo9 mivec, and a different turbo, and the X has a completely different motor, different turbo again, and a different maf. I think your over analyzing your problem. The turbo size alone will make a difference in exhaust flow you should see how much more exhaust was being pushed out of my old hx40 vs the stock t25 (obvious major size difference) i didn't have a way to measure but it was visually noticeably more exhaust exiting the car. Your cars are all about 16g size BUT they are not all 16g's. a better apple to apple if your actually concerned is to find a other 2g DSM with similar mods and compare to that, maybe swap mafs. Or stop relying on the maf all together as a metering device for flow, Sounds like a bad maf throwing off your tune and if it's not that you have other issues going on.

Point im making though is You just gotta stop comparing different cars with different factory hp outputs/ efficiencies just because they are also a 2.0 with the same size exhaust.

patkelley said:

The Hz count on the 2g has increased from the low 40's to 70's with no apparent reason(s). Also, WRT comparing the maf counts of the Evo 9, Evo 10, and 2g at IDLE, the voltage (or Hz) to flow calibration doesn't factor in - all 3 motors should be moving very close to the same amount of air at idle, and there are many, many evoscan logs showing low 40's hz for all of these motors at idle.

Click to expand...

I think you missed the point, just like with your pitot tube the vortexes created in the MAFs (what a karman MAF counts) are different due to the cross section and bypass areas. With exactly the same mass flow rate the two sensors are going to deliver different MAF Hz counts. You have to normalize the values like the ECU does before comparing them. Once you do so I'm expecting the actual flow to be close assuming the VE of the two engines to close at the same RPM.

patkelley said:

The Hz count on the 2g has increased from the low 40's to 70's with no apparent reason(s). Also, WRT comparing the maf counts of the Evo 9, Evo 10, and 2g at IDLE, the voltage (or Hz) to flow calibration doesn't factor in - all 3 motors should be moving very close to the same amount of air at idle, and there are many, many evoscan logs showing low 40's hz for all of these motors at idle.

My issue is the 2g is moving 70 hz at idle, which is about 2x 'normal'. The flow from the exhaust confirms this. Although no one here will understand this technology, I have employed a Fluke vanometer/pitot tube to attempt to measure relative flow between the 2g and Evo9 (the 10 has dual exhaust and I'm not drilling a hole in it before the split), but the actual value from each car is meaningless because I have not engineered the pitot tube to the pipe size. That stated, the relative difference between the 2 cars IS meaningful since I used the same pitot tube on both cars, hence my ~2x difference in flow.

Click to expand...

Be careful what you assume people do or do not know around here, or that they've not read what you've written, especially when you're asking for assistance. Otherwise the answers you get will be "it's magic."

The only way for the flow to increase at the same rpm is if the engine is loaded. An example would be the difference between an automatic in neutral, or in gear. A head gasket will not make exhaust gas volume increase, unless you are dumping water into the combustion process, and have steam coming out of the exhaust, this will be visible.

It sounds like you have a tuning issue with the car.

I second the don't assume what people do or do not know. We have some very educated people here of all ages. I agree with donnie, sounds like tuning. You have some issues....as stated in the first post. Why don't you tell us what those issue are?

pauleyman said:

I second the don't assume what people do or do not know. We have some very educated people here of all ages. I agree with donnie, sounds like tuning. You have some issues....as stated in the first post. Why don't you tell us what those issue are?

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I wish I agreed with you, but replies here clearly indicate otherwise....I'll leave it at that and only wish that folks who knew what they were talking about would reply.

For example, no one questioned ISC/TPS/TB conditions which are the only way air moves into the motor at idle. Air volume at idle (with verified correct mechanical TB adjustment) ONLY comes from the IDLE circuits. Load, cams, turbo, and even exhaust will have little to no effect (remember, at IDLE). Low vacuum should produce lower idle flow (less suction = less flow). I have lower vacuum (~13" at 750 rpm) and MORE flow. Also, (again at idle) my wideband reads ~15, so the ECU is fueling for the increased airflow and my in use fuel trim is below 1.0 (evoscan) so there is little/no unmetered air fouling the system. I can guarantee that it is NOT a tuning problem as I use this setup with 2 evos (the DSM is my kid's car). The ISC tested OK (pins 1-2, 2-3, 4-5, 5-6), and the TPS tests good and was adjusted correctly - I understand that if the TPS is off a bit it will tell the ecu that the throttle is not closed which can activate (open) ISC and thereby raise airflow.

I asked about HG because I have seen cars with combustion breeches do very funny things at idle. Also, combustion leakage (rings, HG or exhaust - intake valve leaks are different) will require more airflow to meet ECU idle RPM setting, but usually results in bad wideband readings (can be rich or lean).

My gut is that I have blowby or exhaust valve(s) sealing problem or maybe a HG breech between 2 cylinders.

As to other issues with performance, when the car won't idle right it's hard to evaluate the rest. It has an intermittent stumble just off idle (and will read lean or rich in the stumble, but mostly rich), but pulls great above that. Also runs slightly warmer than I'd like (220 - 230 deg), but I'd bet that's from a crappy water pump done by PO with Conti timing belt right before we bought the car.

phew thank the flying spaghetti monster I read it first here that nobody thus far knows what they're talking about before I accepted advice from pauleyman, urbansmoker, donniekak, or steve.

patkelley said:

I wish I agreed with you, but replies here clearly indicate otherwise....I'll leave it at that and only wish that folks who knew what they were talking about would reply.

For example, no one questioned ISC/TPS/TB conditions which are the only way air moves into the motor at idle. Air volume at idle (with verified correct mechanical TB adjustment) ONLY comes from the IDLE circuits. Load, cams, turbo, and even exhaust will have little to no effect (remember, at IDLE). Low vacuum should produce lower idle flow (less suction = less flow). I have lower vacuum (~13" at 750 rpm) and MORE flow. Also, (again at idle) my wideband reads ~15, so the ECU is fueling for the increased airflow and my in use fuel trim is below 1.0 (evoscan) so there is little/no unmetered air fouling the system. I can guarantee that it is NOT a tuning problem as I use this setup with 2 evos (the DSM is my kid's car). The ISC tested OK (pins 1-2, 2-3, 4-5, 5-6), and the TPS tests good and was adjusted correctly - I understand that if the TPS is off a bit it will tell the ecu that the throttle is not closed which can activate (open) ISC and thereby raise airflow.

I asked about HG because I have seen cars with combustion breeches do very funny things at idle. Also, combustion leakage (rings, HG or exhaust - intake valve leaks are different) will require more airflow to meet ECU idle RPM setting, but usually results in bad wideband readings (can be rich or lean).

My gut is that I have blowby or exhaust valve(s) sealing problem or maybe a HG breech between 2 cylinders.

As to other issues with performance, when the car won't idle right it's hard to evaluate the rest. It has an intermittent stumble just off idle (and will read lean or rich in the stumble, but mostly rich), but pulls great above that. Also runs slightly warmer than I'd like (220 - 230 deg), but I'd bet that's from a crappy water pump done by PO with Conti timing belt right before we bought the car.

Click to expand...

Have you done a compression, and leak down test? What isc position are you logging, and what is your tps reading?
If for some reason the isc was stuck open allowing more air to bypass the throttle body you would have the infamous bouncing idle, where the idle would raise to 1500 rpms, and fuel cut back down, cycling back and forth.

What is your injector scaling and latency? Have you done any maf compensation tuning?

Also cams, and cam timing have a great effect on idle air usage, and fueling.

Aside from the maf readings a lower compression engine, with less thermal efficiency will have a higher exhaust volume for the same exhaust mass flow due to the lower thermal efficiency. This is why lower compression spools turbos faster.

patkelley said:

I wish I agreed with you, but replies here clearly indicate otherwise....I'll leave it at that and only wish that folks who knew what they were talking about would reply.

For example, no one questioned ISC/TPS/TB conditions which are the only way air moves into the motor at idle. Air volume at idle (with verified correct mechanical TB adjustment) ONLY comes from the IDLE circuits. Load, cams, turbo, and even exhaust will have little to no effect (remember, at IDLE). Low vacuum should produce lower idle flow (less suction = less flow). I have lower vacuum (~13" at 750 rpm) and MORE flow. Also, (again at idle) my wideband reads ~15, so the ECU is fueling for the increased airflow and my in use fuel trim is below 1.0 (evoscan) so there is little/no unmetered air fouling the system. I can guarantee that it is NOT a tuning problem as I use this setup with 2 evos (the DSM is my kid's car). The ISC tested OK (pins 1-2, 2-3, 4-5, 5-6), and the TPS tests good and was adjusted correctly - I understand that if the TPS is off a bit it will tell the ecu that the throttle is not closed which can activate (open) ISC and thereby raise airflow.

I asked about HG because I have seen cars with combustion breeches do very funny things at idle. Also, combustion leakage (rings, HG or exhaust - intake valve leaks are different) will require more airflow to meet ECU idle RPM setting, but usually results in bad wideband readings (can be rich or lean).

My gut is that I have blowby or exhaust valve(s) sealing problem or maybe a HG breech between 2 cylinders.

As to other issues with performance, when the car won't idle right it's hard to evaluate the rest. It has an intermittent stumble just off idle (and will read lean or rich in the stumble, but mostly rich), but pulls great above that. Also runs slightly warmer than I'd like (220 - 230 deg), but I'd bet that's from a crappy water pump done by PO with Conti timing belt right before we bought the car.

Click to expand...

If you suspect a leaking HG, excessive blowby, a crappy water pump, or a slew of other mechanical issues you've mentioned, why the hell are you looking at MAF HZ counts and exhaust flow anyways? Even if your MAF gave you an accurate representation of how your engine was actually running, it would just show you what a crappy running engine should look like. It's moot data, IMO.

Do what everyone else does when they suspect mechanical issues are present:
-Pressure test the cooling system
-Perform compression and leakdown tests when/where required
-Perform a BLT

Keep it simple, and I bet you'd be surprised what you fix.

Also, take 5 minutes of your time and update your profile. I don't know how you expect to get good advice when we know nothing about the car we are trying to help you diagnose.

Regarding basic mechanical tests - cooling system holds pressure at 20 psi, leakdown was ~10-12% on all 4 cyl (short block has 160K, I has head rebuilt in Jan.), and compression was ~140*(tests all done in June). Also no CEL or other codes. I repeated pressure test and leakdown on Sun just to confirm - still holds coolant pressure at 20 psi, but leakdown was erratic with ~25% leakage on 2 and 3, which I could not get to improve with oil or a plug in adjacent cyl. Also noticed air escaping thru exhaust on all 4 cyl which upset me since head was rebuild in Dec. and has <500 miles on it. Pulled the head and found vertical scoring on walls of 2 and 3, so the motor came out today: