01 Berger SS IIX black gunk out tailpipe question??

[daytonajim]

I'm getting a lot of black gunk (unused gas, I think) out the tailpipes on my 01 SS IIX Berger Camaro.

If you go to this link you can see it on the ground behind teh car. Iwt was warmed up & driven 20 miles first.

http://www.youtube.com/watch?v=hyxYhUxu_oY

The trunk & back bumper are full of black gunk everytime I drive the car.

Does anyone have any ideas?

Matt Murphy is not returning my calls or e-mails so I'm hoping someone can help me out.


Thanks Jim Smith 715-529-0898

[lozanoa11]

running rich probaly. no code?

[Phantom409]

Where do you find time to drive all those cars

How long has it been like that?
Seems rich to me.

[WMCC_Alan_Jr]

I'm getting a lot of black gunk (unused gas, I think) out the tailpipes on my 01 SS IIX Berger Camaro.

If you go to this link you can see it on the ground behind teh car. Iwt was warmed up & driven 20 miles first.

http://www.youtube.com/watch?v=hyxYhUxu_oY

The trunk & back bumper are full of black gunk everytime I drive the car.

Does anyone have any ideas?

Matt Murphy is not returning my calls or e-mails so I'm hoping someone can help me out.


Thanks Jim Smith 715-529-0898

have you tried calling him later in the evening?? he's normally up later in the day and all night...

[WMCC SSLS1]

Jim e-mailed me for some input so I thought I would post here to help others……Here comes another short novel (not knowing your EFI knowledge) so go grab a beer before reading……


Jim, I wouldn’t be too worried about it, the black gunk is somewhat “normal” for the higher HP GMMG cars as they are tuned “Safely” to protect your investment IMO (and them). A nuisance, yes, a problem, not really. The temperature and humidity will affect the amount of condensation you get from the tail pipes thus how much “gunk” sprays out the exhaust onto the ground. I always drive my SS a few miles and then stop to wipe the SLP CME exhaust tips to keep them looking good. (The WMCC crew likes to rib me about it too!) Once the exhaust is up to temp then the gunk stops for me.

Your car (under normal highway driving,) is trying to achieve the same 14.7:1-15:1 air fuel ratio for best fuel economy whether you have a 100hp 4 cyl or a 475hp V8. This is because GM (under low load situations) uses the same heated oxygen sensors to sniff the exhaust and adjust the fuel injector pulse width regulating your engine’s AFR (air fuel ratio). This is called “Closed Loop Mode” where the oxygen sensors are being monitored by the computer and have an effect on the base tune affecting your crusing AFR. But under heavy engine load (hard acceleration) this AFR is too lean to safely protect your engine and produce maximum HP.

Under heavy throttle your computer shifts from economy mode (Closed Loop) to PE (often called Performance Enhancement mode) and adjusts the injector pulse width to richen the AFR. The computer goes into “Open Loop Mode” where it ignores the oxygen sensors altogether and references data from within the tune to achieve a richer fuel mixture. It also references the LTFT (Long Term Fuel Trims) and other tables but that is another topic.

Within tuning software there are tables that affect the AFR when your car is in PE mode (under heavy load/acceleration). These tables from the factory are usually on the rich side to protect your engine. These are also some of the tables (along with timing tables) that are often modified to increase your engine performance. From what I have seen on the higher HP GMMG cars they will command for a very rich AFR under heavy acceleration contributing to the black soot buildup within the exhaust, thus leading to increased “Black Gunk” as you put it. You may have noticed black soot coming from the exhaust pipes under heavy acceleration on these cars indicating the rich condition.

Often tuners shoot for around 12.9:1 to 13.0:1 AFR for maximum HP (naturally aspirated) under heavy acceleration load. But this might be on the “edge” of a safe tune so many will tune a car slightly richer for safety giving up a few HP.

For reference a stock 2002 SS has a much richer commanded AFR (in PE mode) of around 11.4:1 in the upper RPM limits.

A GMMG Phase I 380hp car is typically commanded to a leaner 12.0:1 AFR making more HP (along with other computer changes)

My Father’s GMMG Phase IIx tune commands a very rich 10.32:1 AFR.

I have seen a 600hp Phase III 427 ZL1 commanding 10.45:1 AFR

So it is my guess that these “rich” commanded AFRs (while under PE mode) exaggerate the black gunk issue. Theoretically you could adjust the PE commanded AFR leaner to reduce the soot and gain some HP but without using a wide band oxygen sensor I wouldn’t recommend it. Notice the numbers I listed are “Commanded” AFRs not “Actual” AFRs as the actual measured AFR while the car is going down the road may differ from the Commanded AFR of the tune. Without a wide band you would never know for sure and would not want to adjust the tune too lean and smoke your motor. Though I do think their tunes do have room for improvements.

Also note that dyno tunes (as GMMG does) are often tuned a little rich as the actual AFR measured on a dyno can differ from what you would measure on the street. Most dynos do not apply as much of a load to the engine as the weight and rolling resistance the car itself does when out on the street, thus the AFR is usually set a little rich to protect the engine in real life situations.

Do you have a GMMG Dyno chart that lists the AFR under Dyno testing? If so what is the measured AFR on it? That will tell you the truth as to how it was tuned under acceleration.

Another note relating to the Power Tour is that in parts of the country Premium Gas is only 91 octane, and Dad’s Phase IIx engine doesn’t like it very much due to the increased compression ratio. We ran into this on the Power Tour in Arkansas I believe where Dad drove easily until he could get some 93 octane gas in the next state. So you may not want to change the tune before Power Tour as it is on the “Safe” side being overly rich which will help with lesser fuels you may encounter on your travels.

Hope that helps a little, Greg

[kammi10]

and out of freaking no where here comes greg... good info by the way

[zmanrc]

and out of freaking no where here comes greg...

Hahaha ........ I had told Jim that if he couldn't reach GMMG that Greg would be a good person to ask about the issue.

[WMCC AL]

[quote=WMCC SSLS1;420051] so go grab a beer before reading……
quote]


Thanks, I was thirsty........................

[daytonajim]

You're awesome!

Thanks for all the help Greg. I think I'm on the right track.

I'll have a pal who has been a Chevy mechanic (for over 30 years) set the AFR.

I'll need to give him the suggested IIX number for the Power Tour run & where I might want it set after the PT.

Again, you are a lifesaver.

I finally talked to Matt Murphy today & he wasn't sure.

Have a great day.

Jim Smith

Jim e-mailed me for some input so I thought I would post here to help others……Here comes another short novel (not knowing your EFI knowledge) so go grab a beer before reading……


Jim, I wouldn’t be too worried about it, the black gunk is somewhat “normal” for the higher HP GMMG cars as they are tuned “Safely” to protect your investment IMO (and them). A nuisance, yes, a problem, not really. The temperature and humidity will affect the amount of condensation you get from the tail pipes thus how much “gunk” sprays out the exhaust onto the ground. I always drive my SS a few miles and then stop to wipe the SLP CME exhaust tips to keep them looking good. (The WMCC crew likes to rib me about it too!) Once the exhaust is up to temp then the gunk stops for me.

Your car (under normal highway driving,) is trying to achieve the same 14.7:1-15:1 air fuel ratio for best fuel economy whether you have a 100hp 4 cyl or a 475hp V8. This is because GM (under low load situations) uses the same heated oxygen sensors to sniff the exhaust and adjust the fuel injector pulse width regulating your engine’s AFR (air fuel ratio). This is called “Closed Loop Mode” where the oxygen sensors are being monitored by the computer and have an effect on the base tune affecting your crusing AFR. But under heavy engine load (hard acceleration) this AFR is too lean to safely protect your engine and produce maximum HP.

Under heavy throttle your computer shifts from economy mode (Closed Loop) to PE (often called Performance Enhancement mode) and adjusts the injector pulse width to richen the AFR. The computer goes into “Open Loop Mode” where it ignores the oxygen sensors altogether and references data from within the tune to achieve a richer fuel mixture. It also references the LTFT (Long Term Fuel Trims) and other tables but that is another topic.

Within tuning software there are tables that affect the AFR when your car is in PE mode (under heavy load/acceleration). These tables from the factory are usually on the rich side to protect your engine. These are also some of the tables (along with timing tables) that are often modified to increase your engine performance. From what I have seen on the higher HP GMMG cars they will command for a very rich AFR under heavy acceleration contributing to the black soot buildup within the exhaust, thus leading to increased “Black Gunk” as you put it. You may have noticed black soot coming from the exhaust pipes under heavy acceleration on these cars indicating the rich condition.

Often tuners shoot for around 12.9:1 to 13.0:1 AFR for maximum HP (naturally aspirated) under heavy acceleration load. But this might be on the “edge” of a safe tune so many will tune a car slightly richer for safety giving up a few HP.

For reference a stock 2002 SS has a much richer commanded AFR (in PE mode) of around 11.4:1 in the upper RPM limits.

A GMMG Phase I 380hp car is typically commanded to a leaner 12.0:1 AFR making more HP (along with other computer changes)

My Father’s GMMG Phase IIx tune commands a very rich 10.32:1 AFR.

I have seen a 600hp Phase III 427 ZL1 commanding 10.45:1 AFR

So it is my guess that these “rich” commanded AFRs (while under PE mode) exaggerate the black gunk issue. Theoretically you could adjust the PE commanded AFR leaner to reduce the soot and gain some HP but without using a wide band oxygen sensor I wouldn’t recommend it. Notice the numbers I listed are “Commanded” AFRs not “Actual” AFRs as the actual measured AFR while the car is going down the road may differ from the Commanded AFR of the tune. Without a wide band you would never know for sure and would not want to adjust the tune too lean and smoke your motor. Though I do think their tunes do have room for improvements.

Also note that dyno tunes (as GMMG does) are often tuned a little rich as the actual AFR measured on a dyno can differ from what you would measure on the street. Most dynos do not apply as much of a load to the engine as the weight and rolling resistance the car itself does when out on the street, thus the AFR is usually set a little rich to protect the engine in real life situations.

Do you have a GMMG Dyno chart that lists the AFR under Dyno testing? If so what is the measured AFR on it? That will tell you the truth as to how it was tuned under acceleration.

Another note relating to the Power Tour is that in parts of the country Premium Gas is only 91 octane, and Dad’s Phase IIx engine doesn’t like it very much due to the increased compression ratio. We ran into this on the Power Tour in Arkansas I believe where Dad drove easily until he could get some 93 octane gas in the next state. So you may not want to change the tune before Power Tour as it is on the “Safe” side being overly rich which will help with lesser fuels you may encounter on your travels.

Hope that helps a little, Greg

[WMCC Doug]

I finally talked to Matt Murphy today & he wasn't sure.

Was Matt able to help with your Berger HRE and SS information quest?

[daytonajim]

No on the HRE request

Matt was busy & we had a bad connection. I never got to ask the question. I'll ask him at a later time.

Was Matt able to help with your Berger HRE and SS information quest?

[daytonajim]

Matt

Matt was real busy & I didn't get to ask about the HRE cars.