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 High Boost - Could it be my exhaust?

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1998 Riv
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PostSubject: High Boost - Could it be my exhaust?   Tue Aug 19, 2008 4:14 pm

Made time to do a quick scan a few days ago, and with my 3.8 pulley back on the car due to KR issues, I saw boost as high as almost 9 psi! A stock pulley shouldn't be getting that high. Some W-body guys I know suggested my exhaust could be the reason for my KR, seeing as my boost #'s are that high on a stock pulley. At WOT I mostly saw ZERO KR. KR started at about 30% TPS, and went away just after I hit 100% TPS, and stayed at zero until I let off the gas around 95mph.

Here's the scan I logged:

http://www.scandepot.net/viewscan.php?pk=5282
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Chicken
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PostSubject: Re: High Boost - Could it be my exhaust?   Tue Aug 19, 2008 4:17 pm

Dave are your IAT Temps really that high?
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1998 Riv
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PostSubject: Re: High Boost - Could it be my exhaust?   Tue Aug 19, 2008 4:21 pm

It was a hot and humid day, I had to drive a slow 10-15 minutes in town before heading a couple miles out of town where I could make a run. No time for it to cool down, as I was on my way back to work at noon. So yes, that was actual IAT during that run.

On Sunday I added DEI Cool Tape heat reflective tape to my SS intake tube, and I could see how much faster the IAT dropped on the hwy, but in town it still gets pretty warm.
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PostSubject: Re: High Boost - Could it be my exhaust?   Tue Aug 19, 2008 4:25 pm

BTW, my exhaust consists of the stock rear manifold, 3" Hogan DP, 3" hi flow Magnaflow cat, stock resonator, and stock the rest of the way back. I'm wondering if the res on back could be an issue. Running a STOCK pulley, I wouldn't think so, but... I've opened up the intake side with the FWI, coated Plog on the front, maybe I need to work farther back on the exhaust.
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PostSubject: Re: High Boost - Could it be my exhaust?   Tue Aug 19, 2008 4:27 pm

I wish we had a local tuning shop like Intense that could spend some time on a tune. Yes I have a PT, but No Time to learn to use it, and actually put it to use. I suspect if I changed the timing tables back to stock, much of my KR would disappear.
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PostSubject: Re: High Boost - Could it be my exhaust?   Tue Aug 19, 2008 4:31 pm

I think that would be the first thing I would try
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PostSubject: Re: High Boost - Could it be my exhaust?   Tue Aug 19, 2008 4:54 pm

I've also read 2 opinions on the need to skew injectors when running a Plog. Could also be a component of the problem. But, I also had some KR before doing the Plog install.
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PostSubject: Re: High Boost - Could it be my exhaust?   Tue Aug 19, 2008 5:26 pm

We know you had a KR problem before the FWI. I think bringing in more air through the intake throws your tune out of wack, and KR will rise. It looks like you're running lean with O2 numbers in the 905 range, and LTFT locked at 7.8 during WOT. That's bad stuff. The IAT being that high is also not good. I've seen KR in 1st gear after sitting idle for a minute on hot days, then it goes away after IAT comes down. I will not run WOT if AIT is over 100 F.

I had a problem with KR creeping up on me slowly over time. The new injectors solved the problem for me. I know it's a bit of money, but as long as you're running lean, this isn't going to get any better. Sounds like it's getting a bit worse.

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'98 SC Riviera 268k miles 298 HP/370 TQ 0-60: 5.79s ET: 13.97 @ 99.28 4087 lb 20.1 avg MPG Nelson Ledges Lap: 1:30
3.4" pulley AL104 plugs 180 t-stat FWI w/K&N 1.9:1 rockers OR pushrods LS6 valve springs SLP headers ZZP fuel rails
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PostSubject: Re: High Boost - Could it be my exhaust?   Tue Aug 19, 2008 6:27 pm

I doubt its your exhaust unless you have a clogged cat. I have less exhaust mods with more intake mods and i don't have any KR issues( anymore). If i were you i'd set your timing back to stock and go from there. The fact that you don't have KR at WOT is also a bit curious as well.


Last edited by TonySmooth89 on Tue Aug 19, 2008 7:00 pm; edited 2 times in total
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PostSubject: Re: High Boost - Could it be my exhaust?   Tue Aug 19, 2008 6:43 pm

Yes, that is interesting. why no KR when the boost starts to build? Strange indeed. BTW, I think your extra boost PSI comes from the FWI. I picked up a lb when I installed mine.

_________________
'98 SC Riviera 268k miles 298 HP/370 TQ 0-60: 5.79s ET: 13.97 @ 99.28 4087 lb 20.1 avg MPG Nelson Ledges Lap: 1:30
3.4" pulley AL104 plugs 180 t-stat FWI w/K&N 1.9:1 rockers OR pushrods LS6 valve springs SLP headers ZZP fuel rails
KYB GR2 struts MaxAir shocks Addco sway bars UMI bushings GM STB Enkei 18" EV5s w/ Dunlop DZ101s F-body calipers
EBC bluestuff/Hawk HP plus SS lines Brembo slotted discs DHP tuned Aeroforce Hidden Hitch


'05 GTO 49k miles 0-60: 4.8s 16.9 avg MPG Nelson Ledges Lap: 1:26
Because fun
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PostSubject: Re: High Boost - Could it be my exhaust?   Tue Aug 19, 2008 11:34 pm

Cat was new last spring, can't be clogged.

Maybe KR is zero at WOT because so much timing has already been pulled???

I was scanning in "gauge" mode also before logging, and on MILD acceleration from 65-70 mph, in OD, had a few degrees of KR show up.

I have some time off in Sept, but I need to devote most all of it to my 68 GS projects. But I will try to work in a day or 2 to play with the PT. Maybe I can figure out how to reset my timing tables to stock.
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PostSubject: Re: High Boost - Could it be my exhaust?   Tue Aug 19, 2008 11:37 pm

1998 Riv wrote:
Cat was new last spring, can't be clogged.

Maybe KR is zero at WOT because so much timing has already been pulled???

I was scanning in "gauge" mode also before logging, and on MILD acceleration from 65-70 mph, in OD, had a few degrees of KR show up.

I have some time off in Sept, but I need to devote most all of it to my 68 GS projects. But I will try to work in a day or 2 to play with the PT. Maybe I can figure out how to reset my timing tables to stock.

Simple , just go to open calibration file and open your bin , go down to calibration data , click on spark , then left click on good fuel spark and slide over to import , and then the menu will extend to say stock data and hit that. Save and reflash.
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PostSubject: Re: High Boost - Could it be my exhaust?   Tue Aug 19, 2008 11:54 pm

Hey Tony, thanks for the detailed info. I know it's not complicated once you know your way around this thing. Problem here, is I've done nothing more than getting the PT hooked up, set up, and scanned for a couple minutes, LAST year. That's ALL I've done in the nearly a year that I've owned my PT. I had high hopes of learning the ropes this spring/summer, but it just hasn't been possible. I have the tuning notebook, the table modifier, and the new scanning software all on my HD, where they've been untouched.
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PostSubject: Re: High Boost - Could it be my exhaust?   Wed Aug 20, 2008 1:31 am

dang dude..... that whack.... your KNOCK is in the middle of first than NO knock at the top of first THAN you see 5* on the downshift when you let off the gas, which is normal
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