I just installed a new "tuned" PFC from SR Motorsports and I have noticed a very subtle pulsing feeling while the car is warming up. I only notice it under 4000 RPM under steady throttle. It seems to subside when the car warms up.

I am planning to take the car to a shop to fine-tune it on a dyno with a wideband, but I was wondering what could cause this? Does this sound like too much/too little fuel or more of an ignition timing issue...or is this description to vague. Is there anything I can try before I take it to the dyno?

I am running:
Stock Engine/Twin Turbos
M2 Large Intercooler
M2 Intake
3" downpipe
Bonez Hi Flow Cat
Kakimoto Titanium Exhaust

Thanks,

J

 

do you have the commander? If so, go to the etc section, then settings and turn the O2 feedback loop off and see if that does away with it. Ray's map does nothing in the vaccum/low boost side and only changes are seen in the med to heavy load and rpm. I got ripped by him on the same thing. Hell, I bet it's the same map he sold me with different mods.

Tim

 

Yeah. I have the commander. I'll try turning off the O2 feedback loop tomorrow and see if there are any changes.

Thanks,

J

 

It worked. The car runs great now at all speeds.

Now the question is, should I keep the feedback loop off or have the computer re-tuned so I can turn it back on. I am not too concerned about fuel efficiency, as it is pretty bad. I just want to be sure I am not hurting anything by keeping it off.

- J

 

Keep closed loop turned off and lean out your low load cruise areas of the maps as much as possible for smooth motor operation, this will yield better mpg. I was able to tune cruise to leaner than 16:1 AFR and keep the motor running smooth. You may need to richen the fuel enrichment settings for throttle tip-in after you lean out the maps. Tune the idle similarly, no wide band needed for the above but it does help speed it up a bit and you see the actual AFRs.

Most tuners never look at these areas, takes time and makes no power. Does keep the plugs clean and it helps mpg. Customer needs to know what he's paying for and what he's not getting when a tuner charges a left ******** for a couple of hours tuning.

 

I've been leaning out my cruise areas and have gotten some areas into the 15:1's with no problem. However, my tip in is absolutely horrendous now. How high should I have to go with the accelleration enrichenment? I moved them all the way up to like 75 and still couldn't tell it was making any difference. At the time I was running 850cc primaries and secondaries.

 

I'm interested in this too.

 

This is what I had for Accelerate Injector (mS):

5000 7.5 1.0
4000 7.5 1.0
3000 8.0 1.5
2000 8.0 1.8
1000 8.5 2.0

 

Thanks for the reply. I'll give that a try on the way home......

On a side note, what is the second number exactly? I realize it's decay but haven't been able to find out if increasing that causes a shorter or longer "squirt" given a constant first number.