24 replies to this topic

[LUV MY RT]

        The A/F on my car has all of a sudden starting rich. Both street & race tune. Street tune normally 11.5-11.6. Race tune 11.8-11.9. Now running 10.0-10.2 on both tunes. Nothing has been done to the car to cause the change. Here are some things I have checked. I put in a new wide band sensor & calibrated it.No change. Talked to Speedy & he suggested check the cats. I have JBA shorty headers & JBA hi flow cats. Sure enough the cat on the passenger side was coming apart on inside. I gutted both the cats on the mid pipes thinking problem was solved. Run a WOT data log & still rich. I checked base fuel pressure setting on the Fore regulator & it was high @ 68 psi. I backed it off to 58 psi ran another WOT log & A/F came up to 10.6-10.7. Not sure what base setting needs to be. It has always set on 58psi since fuel system was put in car 4 years ago. It is a return system by the way. I have sent data logs to Mike@OST. He has done the tuning on my car & he is also confused as to why the A/F is rich without any changes being made on the car. He said nothing has changed in the tunes from going over the logs that I have sent him. My motor is Arrington 392 stroker with Vortech  S/C running 13.2 lbs of boost. Any suggestions or ideas to my problem.

[Hemi31]

How old are thw fuel lines and are they rubber or teflon inside?

[LUV MY RT]

How old are thw fuel lines and are they rubber or teflon inside?

   Eric, they are teflon & they were put on 4 years ago with the fuel system.

[srt5939]

did you change the air filter? maybe it's clogged

[Hemi31]

Ok....not the lines. How does it run part throttle?

[Hemituner]

        The A/F on my car has all of a sudden starting rich. Both street & race tune. Street tune normally 11.5-11.6. Race tune 11.8-11.9. Now running 10.0-10.2 on both tunes. Nothing has been done to the car to cause the change. Here are some things I have checked. I put in a new wide band sensor & calibrated it.No change. Talked to Speedy & he suggested check the cats. I have JBA shorty headers & JBA hi flow cats. Sure enough the cat on the passenger side was coming apart on inside. I gutted both the cats on the mid pipes thinking problem was solved. Run a WOT data log & still rich. I checked base fuel pressure setting on the Fore regulator & it was high @ 68 psi. I backed it off to 58 psi ran another WOT log & A/F came up to 10.6-10.7. Not sure what base setting needs to be. It has always set on 58psi since fuel system was put in car 4 years ago. It is a return system by the way. I have sent data logs to Mike@OST. He has done the tuning on my car & he is also confused as to why the A/F is rich without any changes being made on the car. He said nothing has changed in the tunes from going over the logs that I have sent him. My motor is Arrington 392 stroker with Vortech  S/C running 13.2 lbs of boost. Any suggestions or ideas to my problem.

Its a hard question to answer with no logs. If I had to guess from experience you have a modifier kicking in. The VVT PCM's are tricky and still missing some parameters in CMR

Hope this helps

AJ

[LUV MY RT]

did you change the air filter? maybe it's clogged

   Cleaned air filter. I thought of that also

Ok....not the lines. How does it run part throttle?

    Car runs great just getting a rich A/F reading. No black smoke & spark plugs look good.

[toofart]

Up the boost!

[LUV MY RT]

Up the boost!

   That is a good idea. My wife likes the sound of that.

[srt5939]

send AJ a log he can fix anything. He the real deal.

[YLWJKT]

Is your belt slipping? If you're losing boost it can make you run rich.

[Speedy]

I have been helping Greg trouble shoot.  We don't think it's tune related because he had been running on this tune for quite some time and the AFR was dead nuts perfect at 11.6 give or take at tick.  We noticed the rich condition at the end of the season on his track tune.  He then tested his street tune to find it was rich as well so we're thinking it has to be something mechanical.  My first instinct was the fuel pressure regulator got moved somehow but we didn't wanna make a change unless we were sure so I suggested a new O2 wideband sensor so we knew the readings were right.  I suggested to data log fuel trims to see how those look but I've not seen that log yet. 

 

He did find one collapsed cat as he stated, which I thought bingo....but gutting them didn't fix it either.  What do most people set their FPR at on a return system?  58psi at idle sound right?

[srt5939]

yep 58 sounds good

[Jerseyboy]

58 without the vacuum hose connected if its boost referenced.

 

J

[LUV MY RT]

58 without the vacuum hose connected if its boost referenced.

 

J

    It was at 68psi with the vacuum line off. I lowered to 58 psi. Its a Fore regulator. Boost referenced.

[LUV MY RT]

Is your belt slipping? If you're losing boost it can make you run rich.

    Not losing any boost. The pulley on the front of the jack plate has been coated. I would have to ask Mike Doban what we put on it. Carbonite I think. The 2 other pulleys are cog pulleys. No slippage

[Jerseyboy]

It was at 68psi with the vacuum line off. I lowered to 58 psi. Its a Fore regulator. Boost referenced.

If it was tuned at 68 and you lowered it to 58 you could have high positive adapts. The pcm will carry a positive adapt into wot if it's above a threshold. Easy way to tell is the long term adapts stay positive when you go wot. They should be 0 if the tune is right.

J

[Speedy]

I'm thinking it was tuned at 58 and somehow the set sure loosened over time or something messed with the reg.

Greg send me a new log with a couple mins of cruising and a wot hit.

[ostmike]

This is a strange one. No positive fuel adapts at WOT (ST or LT). The fuel curve looks smooth but for some reason 1 point richer.

I even compared the injector PW vs. RPM and boost from the dyno logs when the car was tuned to the current logs and they are relatively close.

 

As far as the "correct" fuel pressure there is certainly wiggle room here. However, if the pressure has changed since the dyno tune it will impact the current fueling.

 

I generally set the fuel pressure at the factory setting (58psi with the vacuum/boost reference disconnected) but have tuned cars at various pressures if the owner has a preferred setting. Most of the injector flow ratings are measured at 43.5psi where many car manufactures run the fuel pressure and we can certainly run our cars there or higher/lower when running a FPR.

 

Greg and Jay did their due diligence in troubleshooting so I modified the tune based on the recent logs. Greg will just need to keep a close eye on the AF gauge in the future.

[us1champ]

stupid question and just trying to help

 

any chance the a/f guage went bad? or going bad?  did anyone try changing the guage as well besides just the sensor?

 

also i am confused how the fuel regulator can change if it has never been messed with since install?  is there a chance that it is went bad or going bad?

 

just shooting from the hip.