MM Racing

iTrader: (6)

I am trying to figure out why my car has been feeing so flat as of late. The temps went up here in Chicago and now my car seems to chug from 15in/hg to 1-2 psi of boost. Here is a log of a second gear pull. It seems to clear up after 3000rpms. Makes me thiink it is a bit lean on the high octane map. Your opinions are welcome.

Thanks

elhalisf

iTrader: (171)

hmmm, i dont see anything unsual. the engine seems to be getting a lot of advance timing, and the O2 sensor shows that it is in closed loop operation. since it is in closed loop, it has nothing to do with the octane maps. maybe its a case or base gas, or you have a small boost leak.

MalibuJack

iTrader: (5)

Air density (especialy in closed loop) Have an impact on how the car feels.. 20psi on a really hot day, is less dense than 20psi on a very cold day...

I notice the difference in part throttle performance back in the day when I drove in the morning the car would feel amazing, then driving home in the afternoon, the car felt weaker.. The only real difference was the temps outside were much higher later in the afternoon..

You need to do two logging runs, one in the early morning when its cooler, and another at the time you think it feels weakest (Hottest part of the day?) I'll bet your MAF readings are lower and air temps are higher.. Everything else being equal, those two things can have a pretty large impact on the way the car feels..

MM Racing

iTrader: (6)

Yes I understand the physics and thermo of what is going on. I guess I should have been more clear. The WOT does not seem to be an issue, it is more and open loop problem, part throttle acceleration feels flat and occasionaly I see a couple of knock hits pop up and then once it hits 3K everything clears up. I bought some race gas this morning to see if the knock counts were timing or fuel related and they seem to still be present. I have a couple of ticking lifters that I am going to replace to see if that solves the false knock.

I guess I am just not sure if this is a HKS 272 side affect or if I can tune it out. I haven't seen anyone post a map of a car with 272's on it.

Thanks Jack for taking the time to look through the log.

DynoFlash

iTrader: (91)

The people who are seeing so called "knock counts" on partial throttle crusing - those are drive train noise - gear lash and etc

As for the feeling of a flat "mid range" - I think what you are saying is that the car has a flat throttle response in areas of partial TPS position which IMHO is normal in a turbo charged car

People have to realize that OFF boost these cars have very little power and the difference between one TPS angle and the other as far a s power is marginal and not something that will mkick you in the *** like on a V8 N/A car

MalibuJack

iTrader: (5)

Yeah, I understand what you meant.. Closed loop part throttle driving will bite you when your not in boost.. the stock turbo is much better than a big turbo when your driving off boost since at highway speeds, your really only a bit of throttle away from boost.. I do lean-spool my car at very low loads, and also do alittle playing with timing at part throttle low load (low to no boost) along the lines of N/A type tuning, but as a result I increase exhaust volume a bit which speeds up spool a little..

The 272's straight up have just enough overlap to have an impact doing the kind of driving your describing, but it can be worked around with tuning....

Think bout it this way.. without the turbo, this engine probably makes about 160hp/tq and thats what you mostly feel when your off-boost..

MM Racing

iTrader: (6)

I had a 91 GSX so I am familiar with the off boost lack of power. Looks like I will either be picking up some cam gears or will be screwing around with the low load timing curves. Thanks again Jack.