Another "help me" with my combo thread...

[Tom87GN]

I am a long-time member of TB.com and have searched many topics just like this one. I seem to be stuck in a rut with my GN which should be running better times with the mods that I have done.

In my signature below you will see what I've done. The 12.06 timeslip seems to be a mirage, since I've only been able to get the car to run this time once! Since then, the closest I've been to it is around the 12.40's at 106-107 MPH.

I seem to be losing MPH but my short times are still consistently in the 1.8's and high 1.7's.

I'm looking for some advise as to what I should look for as my culprit to keeping me from running in the 11's.

It should be known that my GN has always had a problem with running lean at the top end, no matter if I'm running Joe Lubrant chips or if I'm running Red Armstrong chips (usually rich I'm told). The 02's will drop into the 750's and 740's and sometimes even lower at the big end.

 

[V6POWER]

Have you upgraded the fuel system?

 

[Tom87GN]

Shoot...I need to fix my signature again! Sorry about that. I've got a hotwired Walbro 307 in there right now. I've got a 340 sitting on the shelf awaiting installation.

 

[Kip]

Tom, What are you using for a scan tool? Have you ever checked to make sure that there is no kink in you fuel delivery line anywhere?
Take care, Kip

 

[Tom87GN]

Originally posted by Kip
Tom, What are you using for a scan tool? Have you ever checked to make sure that there is no kink in you fuel delivery line anywhere?
Take care, Kip

Kip, I'm using both Turbolink and I have a Scanmaster. My car has always knocked a fair amount at WOT (3-7 degrees usually, sometimes more) even with the alcohol kit running. Some times it won't knock a bit and run great. I know that these cars are bitchy, I've owned this one for almost 8 years now.

As far as the fuel delivery lines, I've not checked them from the tank connection to the motor yet. I need to get her up in the air and take a look see at the fuel lines.

 

[DCVING 6]

Originally posted by Tom87GN
Kip, I'm using both Turbolink and I have a Scanmaster. My car has always knocked a fair amount at WOT (3-7 degrees usually, sometimes more) even with the alcohol kit running. Some times it won't knock a bit and run great. QUOTE]

Is it pulling timing out?

 

[Tom87GN]

Originally posted by DCVING 6
Is it pulling timing out?

I may be misunderstanding your question. If the car is knocking and the scan tool shows retard in degrees, that's pulling timing out correct?

 

[DCVING 6]

Yea, if it's knocking, it will be pulling timing out which will slow down the car. Put some 116 in and see if the knock is real or not.

Also, depending upon your base fuel pressure and amount of boost your running, you may have that 307 maxed out. May need to swap in that 340 you've got.

Have you ever replaced the valve springs? If they are worn out, the car will lose MPH on the top end.

 

[Tom87GN]

O.K. This is good that I'm talking through this with you guys. This helps me figure out where I am with the combo again.

I have run race gas through this car several times. If I put 111 Leaded in the tank (not a mix, straight race gas) the motor will not knock but I still don't get the MPH required by my mods.

As far as valve springs go, the motor has had old-style LT1 springs on it since 2000 or 2001. I have not pulled the cam or observed the rockers moving with the motor running to tell if there is a cam lobe gone, but there has never been any metal in the oil or in the pan.

The best pass the car made in September of this year was a 12.42 @ 106. I used to get 109 MPH out of it. I thought I was close to the 11 threshold with the 12.06, but that was over a year ago and I haven't been close to that number since then.

 

[V6POWER]

What fuel pressure regulator are you using? I had a bad BGC adjustable one that would show an increase in pressure as I turned the screw but I later discovered that it was not flowing the volume that it should. This was causing me to have high knock and also to lean out at higher rpm's.

 

[gmpower6]

Pull that damn motor out and go through it LOL. Your car is weird should be alot faster then it is. When i drove it seem to lose a few rpm on top. Maybe springs and a cam lobe starting to go?

You have all winter to do this and you know what i am doing this winter HMMMMMM.

later Dog

 

[Tom87GN]

Originally posted by gmpower6
You have all winter to do this and you know what i am doing this winter HMMMMMM.

later Dog

O.K. man.....bring your pillow. I'm ready to find the problem!!! I'll supply the beverages.

What I want to be able to do is come up with a list of things that I need to investigate further. Here's what I've got so far:

1. Check fuel feed line for kinks
2. Possible problem with Walbro 307 pump (might be maxing out)
3. Possible problem with adjustable fuel pressure regulator
4. Valve springs
5. Possible cam lobe going bad
6. Reset cam sensor (my own idea)

gmpower6 is right....I've got all winter to find the problem areas.

 

[Danster]

Could it be that maybe your PTE 70mm plenum may be hurting your performance? I have come across some threads that mentioned the addition of the 70mm plenum hurt the performance of the car.

I don't know so I'm just throwing it out there!

Dannyo

 

[Tom87GN]

Originally posted by Danster
Could it be that maybe your PTE 70mm plenum may be hurting your performance? I have come across some threads that mentioned the addition of the 70mm plenum hurt the performance of the car. Dannyo

I have often wondered if I screwed the intake characteristics up with the addition of the 70MM plenum. I've got a stocker that I can throw back on there and just may try this option if other ideas don't work out. Thanks for the reply Dannyo!

 

[SPOOLFOOL2]

Could the stock maf be maxed out? Do you have a scan tool to check? Do you have a fuel presure gage that you can mount outside the hood? Your fuel presure should rise one pound for every pound of boost.

 

[broke1]

Turn the boost DOWN till you get zero knock and work your way up slowly.Your alky pump could be bad.Id also get a newer chip and do a full spring cleaning(gnttype.org)

 

[Tom87GN]

Originally posted by SPOOLFOOL2
Could the stock maf be maxed out? Do you have a scan tool to check? Do you have a fuel presure gage that you can mount outside the hood? Your fuel presure should rise one pound for every pound of boost.

Got those issues covered. Sorry, I didn't have those items listed in my signature (they are now). I've got an LT1 MAF sensor with the translator plus. I installed these items this past summer and they did not affect how the car ran any.

I also have an externally mounted fuel pressure gauge that I have verified the fuel pressure on. It rises the correct 1 pound per each psi of boost.