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Lots & Lots of KR- 98 GTP

1FastGP

1FastGP

New member
Just to start off I think this may be false knock because there is no way this motor should still be in one piece.

Basic run down it has Speed Daddy headers, no cat, MPS 3.4, 180 T-Stat, Thrasher CAI, and an old school 3800 performance tune.

Now for the knock:
Warmer Weather(70-80F)- 6-7 degrees of knock with timing between 6 and 8
Half throttle pull nets about 2-4 degrees

And now for the kicker:
Winter(35F)- 13.8 degrees of knock with WOT timing at 5

After the winter reading I don't see how it still runs so maybe it's false but regardless I need ideas as to what may be causing it or if it is in the tune. Added notes: fuel trims on torque stay negative no matter how many times I've reset computer and the car was decently abused before I bought it. Any help is greatly appreciated
 


ever run it with no sc belt? take the belt off, run it wot, if you got kr still somethings hitting. no kr the blower bearings could be bad.

also rev it in park, scan for kr, if you see kr the blower is bad.
 
Never thought to run it with no belt I will do that later ltft is about -7

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this is where having a wideband would come in handy, -7 is really rich and could be causing a lot of your kr. if you had an HP Tuner or dhp you could pull some fuel from the wot cells and see if that works.

if you knew what your air fuel ratio was we could more definitively say if that was causing your kr.
 


don't forget that some of those cheap Flex joints that have the braided inner liner that can separate and reduce the diameter down to less than 2 inches and create exhaust back-pressure. Make sure you do not have abnormally high boost readings for your pulley size
 
So I took the belt off and it runs 21 degrees of timing with 0 knock so I think I'm going to buy a stock pulley and have good timing without knock. On a side note I unhooked the battery for awhile and now the fuel trims are hanging at 0.8 at wot with 3 degrees of knock

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you reset the trims, so they are all over till they learn. 21 degrees is likely way to much timing for your mods. pulley up for sure.

was this tune for your car? or you bought it used? if used, is it for the same year as your car?
 
The tune is for the car it's the pcm I bought it with. It was part of a thrasher stage kit 3800 performance used to sale so it came with the airbox and was supposed to come with a pulley but somewhere between now and 1998 that disappeared

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if you could get the timing dropped to 17-18 i bet you'd enjoy the tune much more. i know of one guy in NC with a dhp, no idea if you guys are close or not tho. he might not even charge you for just a flash. you know if hes not tuning it really. be done all of 15 minutes time.
 


I think I'm going to put a stock pulley back on and see how the KR is, something tells me the power difference between a 3.4 with 6 degrees of timing and a 3.8 with 21 degrees aren't going to feel drastically different. If it still knocks I'll be back here and try to track down the other NC guy
 
when you see that low timing thats because the kr knocked it down there. every degree of kr drops the timing 2 degrees. you can see that math right there in front of you,

i talked to that guy in NC says hes about 1.5 hrs away. not to bad of a drive really.
 
Oh yeah I know how the kr makes the timing go to crap but do you think a stock pulley would run alright with the tune I have now. I have one somewhere in my humongous pile of GP parts, if it's not quick enough for my likings I may grab the 3.4 and head to that guy

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its just to much timing even on a stock pulley. if you have a stock pcm still toss that in, you'll be much better off.
 
I do have a stock 98 pcm I'll swap that in with the 3.8 and report back at some point in the next week

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leave the 3.4 on there with the stock pcm. it will run better still. stock timing is olny 15-16 wot.

with my mod list im only at 17º wot timing. drops to 16 after 5200.
 
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