"Car runs better at part throttle..."

[S10xGN]

Hi All,

I've heard that line a bunch of times, and my little truck feels the same way sometimes. I've got a "theory" on (maybe) why this happens: At part-throttle, the ECM is NOT yet in P.E. mode (> 3.00 on TPS?) thus, the motor is seeing a little "leaner" mix than at full-throttle. If this is the case, would further chip tuning be in order?

TIA!

 

[TurboDave]

Originally posted by S10xGN
Hi All,

I've heard that line a bunch of times, and my little truck feels the same way sometimes. I've got a "theory" on (maybe) why this happens: At part-throttle, the ECM is NOT yet in P.E. mode (> 3.00 on TPS?) thus, the motor is seeing a little "leaner" mix than at full-throttle. If this is the case, would further chip tuning be in order?

TIA!

Interesting theory, and maybe somewhat true, but there's one problem.
You're into PE WAY BEFORE you think you are. Certainly way lower than 3.00v tps!! The primary factor for getting into PE is not TPS but rather LV8. The minimum LV8 threshold for PE is only 160. You can hit that just pulling away from a traffic light. The TPS can overide the LV8 threshold but not until 45% tps. It's moot because you're already in PE by that time (or should be).

However, PE fueling is much lower at TPS levels below 45% than it is else where so your "leaner" theory holds some water.

Most of it just depends on how well the PE curves are built in a given chip as to how it "feels" part throttle vs. WOT

 

[S10xGN]

Thanks, Dave - I wasn't sure at what point the PE was triggered by TPS and I did NOT know about the LV8 pushing PE... Is there somewhere I can read up on the finer points of our ECM's logic?

 

[TurboDave]

There's a couple of places:

http://www.gnttype.org/techarea/ecmsensors/ecmpage.html

http://www.gnttype.org/techarea/chips/chippage.html

Hope that helps. Awful lot of stuff to sift through though.

 

[turboost]

I have the same problem.

My car has always felt this way with my current setup and my previous with 36lb inj and Thrasher chips. At part throttle with 12lbs of boost feels stronger than full throttle with 20lbs (no joke). I have never felt a top end pull with this car except when I used a shot of nitrous. My traps are in the consistent 103-106 with 20lbs of boost. The car only makes up 21 mph after the 1/8. Is this a computer problem somewhere or a mechanical problem.

 

[turboost]

double post

 

[BlackBeauty]

I have felt that with my previous two cars, both happening to be turbo cars. They feel faster at part throttle when I floor it above 45mph or so. Even if the car is running leaner at part throttle, it is still not delivering full power.
It may be psychological, maybe because at WOT, you can hear the car straining so much, but it's harder to accelerate when you're at higher speeds... how can I explain this? Ok, an example is how Turboost told us he only gains 21mph after the 1/8th mi. But at part throttle, you aren't expecting a lot of power, but your expectations are exceeded.
...or maybe I just need new valve springs.