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2001 special edition gtp issues-need some input

F

fst

New member
Helping and posting for a friend. 2001 special edition gtp with stock pulley and dhp 1.5 tune with a mild custom tune i had done. Car has cai, 3"dp, stock manis, u-bend delete.
Has ported gen 3 m90 that gets around 9-10psi. Currently gets constant 2-3* kr.

So far he has changed/added the following:
255 walbro fp with rewire
Fuel filter
Injectors
Fpr
Plugs/wires
Hi speed fp relay pin 85 bent

Tested fuel pressure:
Idle is ~45psi and drops to steady 40psi
At wot is constant 57-58psi

Checked for vac leaks but found zero. Idle vac is ~17-22inHg

We're both boggled. Only thing left is swap pcm with a 2000 gtp PCM from a local.

He has a zzp afc 1.2 and adding 2% didn't change the amount of kr or fuel pressure at wot.

edited: buddies car is a 2001 and added he removed the u-bend and that it's a special edition
 
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Re: 2000 gtp issues-need some input

most canned tunes are set to 18 degrees wot timing, that might be to much.

could be a beat up stream o2 sensor, scan it, see if its voltage moves fast up and down.
 
Re: 2000 gtp issues-need some input

and i cant see him making 9-10 psi on a ported gen 3 w/stock pulley. porting lowers boost. 5-7 is more like it for sure if hes got headers. 8 would be tops with stock manifolds still.
 
Re: 2000 gtp issues-need some input

He's scanning via torque app which is pretty good at scanning parameters. I think his timing is either 17 or 18 like you stated. He's about 400-500 above sea level fwiw. The scan showed today max 9.1psi.
 
Re: 2000 gtp issues-need some input

maybe the map sensor is bad? thats higher then normal. headers? if not maybe the cats clogged up?

just headers drops the boost to 5 psi on a stock pulley. factory they only put out 7-8 psi.
 
Re: 2000 gtp issues-need some input

He's running a hiflo zzp 3" dp
He cleaned the maf but i dont think he replaced it
 


Re: 2000 gtp issues-need some input

Will, i would lower the timing but i sold my dhp and now have hp tuners. Also he has a afc 1.2, wouldn't he be able to increase fuel to compensate running the current timing? Or his mods aren't sufficient enough to run that amount?
 
Re: 2000 gtp issues-need some input

also while idling fuel pressure's at steady 40psi and when I unhook the vac line off the FPR, it'll jump to 50psi which tells me the FPR is working.

cruising fuel pressure is between 40-45psi with light throttle.

edit- was thinking about if he should swap the pcm and see if it still gets KR?
 
Re: 2000 gtp issues-need some input

I'm missing the question... Is it you are confused as to the 2-3* of knock? With no real supporting mods other than 3" DP?
I'd say, 2-3* is great...

why are you fixated on fueling? What octane are you running?

no way 9-10lbs boost on stock pulley, just sayin...
 
Re: 2000 gtp issues-need some input

im confused on the fuel pressure and the constant KR. for the fuel pressure part, if commanding more fuel (via AFC) wouldn't fuel pressure at WOT increase and not stay constant at 57psi at WOT? which leads into my 2nd part of the constant KR, if fueling is added to quench and compensate KR, wouldn't the number lower then to 1-2*?

the scan recorded 9.1psi as max which is what the pcm is reading which is coming the map sensor. my friend's using 92/93 octane. I understand every car is different based on mods, but if able to adjust fueling, even near stock, I would think it would lower the KR to zero.

what's the likelihood of a clogged exhaust manifolds? I hardly hear that but thought I'd ask.

edit-and no u-bend which I added in the original post.
 


Do you even know what the real time AFR is?

Adding fuel can cause more knock, the same way less fuel can cause knock.

The Mini AFC has nothing to do with fuel pressure, it will not increase the pressure. All that thing does is fudge the numbers the MAF is reading. Fuel pressure is going to remain the same, the MAF is an airflow table that control fueling, the more airflow coming in the more fuel it's going to tell the injectors to squirt.
 
no idea on actual AFR, no wideband. makes sense about the mini afc wouldn't increase fuel pressure.

he's going to scan the O2 NB volts and see how they are in the meantime.
 
Fuel pressure is pump related and constant... When adjusting fueling you're changing the pulse width/time the injectors actually stay open, that's it. Unless there's something wrong with FPR, how are you measuring FP?

I believe you're chasing ghosts and you aren't going to be able to completely eliminate knock based upon your mods and lack of tuning information, ie, wideband. Torque is good, but not what you want to be using to tell you what's going on if you're going to adjust tune!

Biggest restrictions are Ubend and Exhaust Manifold, you've done 1/2. Headers will certainly drop a few degrees of knock. Add rockers to let it breathe a bit better and you'll take off a degree or two with that as well. You have HP Tuner and can't adjust timing?

Honestly though, I wouldn't worry about 1-2* if knock unless everything else in the tune was to the edge!
 


^I edited my post based on my friends mod list. it the only restriction currently are the stock exhaust manifolds. I tuned his pcm when I had my powertuner (sold it now). unless he's willing to pay $100 to open up his vin then yes, I can tune and lower the timing. that's the last resort. im trying to figure out what all else I may be missing that's causing him the 2-3* of KR.
 
to much timing to not have headers, headers will fix him up asap im sure. and let him drop to a 3.4 if he wants to.

unlocking his vin would be cheaper if hes not into modding any further. or lets face it, if he does want to mod further as well. 100 bucks is well spent money.
 
fst said:
^I edited my post based on my friends mod list. it the only restriction currently are the stock exhaust manifolds. I tuned his pcm when I had my powertuner (sold it now). unless he's willing to pay $100 to open up his vin then yes, I can tune and lower the timing. that's the last resort. im trying to figure out what all else I may be missing that's causing him the 2-3* of KR.
Click to expand...

You're trying to fix things with ways they can't be fixed! Tell you friend he's gotta pay to play, no way around it, or put it back stock and call it a day! Like I said, a few * if knock isn't the end of the world. My stock GTP would get 8-10* of knock...

So like mentioned, either way to tune it. Or put physical elements in place to help alleviate the knock. Open breathing and exhaust... Headers are and should be the #1 MOD anyone does to an engine if modding! Or find used high ratio rockers... Last thing is to buy a octane enhancer like Torco, but that cost keeps coming back every tankful, lol...

Cheap/Fast/Reliable
Tell you friend to pick two, any and only two! That's all...
Want it cheap, if fast, it won't be reliable!
Want it cheap and reliable, it won't be fast!
Want it fast and reliable, it isn't cheap!
 
i was thinking how much meth would do for a car with stock exhaust manifolds still, i was thinking a 3.2 maybe. once again, you need a tuner to run meth.
 
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