HPCR fuel system.........

[krabman]

It would seem to do the opposite for me. I give it a little extra time for clutch release during shifts for the rpms to drop so that I dont get the major herky jerky ride while going thruough the gears that I get if I shift more quickly. If anything Im guessing I lose a little bit in terms of milage or emmisions from the lost momentum/ lower rpm that I end up at after the shift is complete. I have talked about this to a few other 03 owners and they said they give it the extra time during shifts also so Im not the only one.

 

[RSnaith]

They are definitely a different beast to drive. Using lower RPM shift points (say under 1700), I have to do what you're saying: slow down the shifting. At higher RPMs, I find that my boost doesn't drop off as much as my 01, however I also find that I need to be getting on throttle a hair before fulling releasing the clutch. This prevents the jerking you're talking about. It also goes against my nature, as I was taught to stay off the doggone throttle until the clutch pedal is released

 

[V6power87]

Keith,



When is a fueling box going to be out for the '03's?





Also thanks for giving me the grand tour of your guy's shop in November... . the white truck was a blast to ride in!!

(I had the Buick GN on the trailer if you don't remember me)

 

[KLockliear]

V6power87, yeah, I remember you. How did your race weekend turn out? Anyway, we should have a production box available in the next month or so for the 03's.



On the other question, the small HY derived turbo on the '03 causes very high drive pressure even in stock form. This means that when you get off the throttle after being in boost, there is still enough pressure to keep the turbo spinned up for a bit, which means boost while you're off throttle. Since the truck is very dependent on MAP for it's fueling as well, it will continue to fuel more than needed for an idle rpm since it's still seeing boost. This only gets worse when adding a box which is more sensitive to MAP for throttle response. Luckily, the turbo and airbox are very restrictive, and changing to the bigger turbo and a less restrictive airbox drop the drive pressure dramatically and remove this little glitch.

 

[V6power87]

Keith... . The buick went it's all time fastest et & mph, 11. 21 @120



Not bad for a stock V6, with just bolt- ons. Up here at sea level that might be an 11. 0 something.



I will come see you guy's this november when I come back down. Take care!!

 

[RSnaith]

Originally posted by KLockliear

which means boost while you're off throttle. Since the truck is very dependent on MAP for it's fueling as well, it will continue to fuel more than needed for an idle rpm since it's still seeing boost.

So they quit using throttle position as in input into the fueling levels? Weird, thats just asking for a runaway.

 

[KLockliear]

I said it was very dependent on MAP, not that they are no longer using TPS.

 

[RSnaith]

Originally posted by KLockliear

I said it was very dependent on MAP, not that they are no longer using TPS.

Okay, so now we're back to why they've programmed it like this. They could have simply cut the fuel back earlier as the TPS signal drops, as eventually this does happen. Its like they ignore the TPS for a couple heartbeats. I find it unlikely that they've introduced a bug of this nature into the program (not beyond belief, but difficult to believe), so that means they had to have a reason, and that simply leads us back to emissions control, clutch saving, or some other reason.