Hey all,

I just did my pulley swap/tune/O/R x-pipe yesterday and although the results are amazing (beat a C6 Z06 from a third gear roll on the autobahn until 140mph), I have noticed that at initial WOT in any gear, boost reads 14psi, then around 4-4,500rpm, psi drops down to 5-9ish psi. and stays that way until redline. It sounds like I am hearing a bypassing sound but I can't be sure. I will be datalogging tonight to see if something pops out. I am just wondering if anyone else has seen this issue?? Is the belt possibly slipping?? Do I need to adjust the idler pulley (it's a Metco unit, I bought the kit through Lethal Performance)?? Any/all thoughts & advice would be appreciated! I will be trying to call some places tomorrow for insight. Thanks gang!!
-Chris

Hey all,

I just did my pulley swap/tune/O/R x-pipe yesterday and although the results are amazing (beat a C6 Z06 from a third gear roll on the autobahn until 140mph), I have noticed that at initial WOT in any gear, boost reads 14psi, then around 4-4,500rpm, psi drops down to 5-9ish psi. and stays that way until redline. It sounds like I am hearing a bypassing sound but I can't be sure. I will be datalogging tonight to see if something pops out. I am just wondering if anyone else has seen this issue?? Is the belt possibly slipping?? Do I need to adjust the idler pulley (it's a Metco unit, I bought the kit through Lethal Performance)?? Any/all thoughts & advice would be appreciated! I will be trying to call some places tomorrow for insight. Thanks gang!!
-Chris
Yes, your belt could be slipping, or the Eaton could simply be maxed out on how much boost it could deliver at that RPM.

I also seen that my boost peaks as soon as I hit WOT, but drops from 15psi-11psi as the engine goes from 4-6k rpm and I have a 2.3L TVS. My guess is that to keep 15 psi up to redline I would need to add a pulley, or swap out to a larger blower.

Your Eaton is not "maxed out".

Either you have belt slippage or you're dealing with a high level of heat soak and the computer is pulling a bunch of timing at X load.

bj

Sure your not starting to spin and the Advance Trac is taking over?
Have you tried turning off the Advanced Trac, not just the Traction control ?
I havent paid much attention to mine, to busy watching the road.
I do know when the Advance Trac is off it's a whole new beast!

Yes, your belt could be slipping, or the Eaton could simply be maxed out on how much boost it could deliver at that RPM.

I also seen that my boost peaks as soon as I hit WOT, but drops from 15psi-11psi as the engine goes from 4-6k rpm and I have a 2.3L TVS. My guess is that to keep 15 psi up to redline I would need to add a pulley, or swap out to a larger blower.
Mine does the same thing...boost varies from 12-15psi depending on atmospheric conditions. Also, don't trust the stock boost gauge. It's an inferred value from the pcm, not true boost.

how old is your belt?

check for dust near the blower snout pulley - that is a tell tale sign of slip

Your Eaton is not "maxed out".

Either you have belt slippage or you're dealing with a high level of heat soak and the computer is pulling a bunch of timing at X load.

bj

BJ - in your example, how would that affect boost? power of course, but pulling timing doesn't change the blower RPM

Mine does the same thing...boost varies from 12-15psi depending on atmospheric conditions. Also, don't trust the stock boost gauge. It's an inferred value from the pcm, not true boost.

In October I'm going to have a dyno pull so I'm going to try to find out what's really going on.

My guess is that the stock Eaton, and even the TVS can't pump enough to keep the boost up at the higher RPM. Smaller displacement superchargers become inefficient as they spin near their design limits. It's why you get more power with the same boost level using a larger displacement blower.

how old is your belt?

check for dust near the blower snout pulley - that is a tell tale sign of slip



BJ - in your example, how would that affect boost? power of course, but pulling timing doesn't change the blower RPM

It won't. I was either:

(a) Loaded
(b) Tired
(c) Talking out my ass
(d) Didn't read it fully and typed before I fully comprehended
(e) All of the above

I'll pick (d) since I was attempting to read and respond on my "not so smart" phone.

bj

:rofl::rofl:

ok, fair enough

Hey guys, just wanted to give an update...

turns out, it was not a belt slip issue. I relocated the idler, and no change. So I called Lethal, got in touch with John Lund and he sent me a revised tune. Turns out I'm the second known GT500 owner who had this issue. Well, after the revised tune was loaded, WOW this thing runs crazy faster...14psi all the way to redline now :) 180mph is no longer an issue hahaha Thanks for all the help though guys!!!

Good deal.

Wow, that's interesting it was the tune parameters. Glad you got it sorted out and the first GT500 with the problem took care of the research for you!!! :)