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-   -   Thought on Headers (http://zr1.net/forum/showthread.php?t=3487)

XfireZ51 06-11-2007 07:15 PM
Re: Thought on Headers
 
Quote:
Originally Posted by mrzzzr1
How do I contact Mark?
mr zr,

Any pics of the headers from PFE? Do they have a website and what was the cost if I could ask? As for the exhaust popping, you may want to check for air leaks. Also, invoking DFCO and DE routines in ECM will cut down amount of gas on decel. What year is your Z?

Jeffvette 06-11-2007 07:32 PM
Re: Thought on Headers
 
Quote:
Originally Posted by mrzzzr1
I have one additonal thing to mention > I get a some backfire sounds when I downshift. My mechanic says the backfire is due to the air pump being hooked up and a lot of raw gas going into the exhaust when I am downshifting. He says he can disable the air pump but is concerned about setting a trouble code in the engine computer.
You need a better mechanic or one who is more in tune with LT5's. The air pump only works upon vehicle start up. it ingests air into the manifolds to help get the cats up to temp. You can unplug the air pump with no drawbacks. The back fire is caused by excess fuel not being burned off in the combustion process.

XfireZ51 06-11-2007 10:35 PM
Re: Thought on Headers
 
Quote:
Originally Posted by Jeffvette
...The back fire is caused by excess fuel not being burned off in the combustion process.
Yes but there's air entering the system to light the unburned fuel.


mrzr,

Where do you hear the popping? From the rear or under the car?

Jeffvette 06-12-2007 01:50 AM
Re: Thought on Headers
 
Quote:
Originally Posted by XfireZ51
Yes but there's air entering the system to light the unburned fuel.


mrzr,

Where do you hear the popping? From the rear or under the car?
And it's not coming from the air pump. Haibeck has figured out where to fix this in prom tuning.

mrzzzr1 06-12-2007 03:51 AM
Re: Thought on Headers
 
No pics of the headers and I bought them 5-6 years ago and bought the last set they had laying in storage. They looked just like the stock headers minus the cats.

Price then including install was $900.

PFE stand for Performance Fabrication Engineering and they fab custom exhausts and also install aftermarket exhausts.

What is the recommed way to disconnect the air pump if I should opt to do it?

mrzzzr1 06-12-2007 04:04 AM
Re: Thought on Headers
 
I plan to contact Mark Haibeck re doing the fix to my prom. Thanks for the suggestion.

As for where is the backfire occurring it is inside the exhaust sys. I tend to downshift a lot when braking so my driving style may be a contibuting factor.
I have spotted flames coming out of the exhaust tips in an autocross when my son drove the car. The last leg before stopping was a short accelleration followed by a pylon garage with a sudden stop. So, when he did a quick accel followed by immediate brake the excess fuel ignited and shot flames out of both sides exh tips.
I want to elimiate this though and it probably isn't good for the exh sys either.

jonszr1 06-12-2007 09:16 AM
Re: Thought on Headers
 
call mark he can do it .you will have to send him your prom

tpepmeie 06-12-2007 06:53 PM
Re: Thought on Headers
 
This backfiring is caused by the DFCO (decell fuel cutoff) settings in the stock calibration. The settings call for extreme timing retard when the DFCO is active. The retarded timing, combined with any residual fuel in the cylinders cause the popping.

SImple fix is to disable the DFCO. Second fix is to lessen the spark retard setting.

todd

XfireZ51 06-12-2007 09:42 PM
Re: Thought on Headers
 
Quote:
Originally Posted by mrzzzr1
I plan to contact Mark Haibeck re doing the fix to my prom. Thanks for the suggestion.

As for where is the backfire occurring it is inside the exhaust sys. I tend to downshift a lot when braking so my driving style may be a contibuting factor.
I have spotted flames coming out of the exhaust tips in an autocross when my son drove the car. The last leg before stopping was a short accelleration followed by a pylon garage with a sudden stop. So, when he did a quick accel followed by immediate brake the excess fuel ignited and shot flames out of both sides exh tips.
I want to elimiate this though and it probably isn't good for the exh sys either.
Jeffvette,

Agreed its not coming from airpump.

mrzzr1,

I wrestled with this issue for sometime on my 84. Played with the cal removing fuel with DFCO and DE routines, bumping lower MAP timing etc. Turns out I had a rear muffler/pipe interface that was leaking. Thought it was tight. Needed new clamp. No more popping. :thumbsup:

Nick 06-14-2007 07:35 PM
Re: Thought on Headers
 
Quote:
Originally Posted by Jeffvette
And it's not coming from the air pump. Haibeck has figured out where to fix this in prom tuning.
He fixed it on my chip, and it works great. :thumbsup:


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