Byron Today

[LGAFF]

Pete,

When you say 118-120...is that one Drag radials or Street tires?


LGAFF
92 ZR1
#234

[jonszr1]

pete , so you are running the stk fueling.? after porting myinj housings and plenum, my air fuel on the dyno went to 13.9 to 1. how do you combat the lean condition/ my car detonated like crazy on the first dyno run. which was why corey took 2 deg of timming out over 4500 and added fuel to get the air fuel down to 12.8-12-9 to 1.

[jonszr1]

paul , my modds are as follows , jeal headers ,fidanza flywheel, corey henderson ported inj housings and plenum, as well as prom tune , 410 gears, z industries reverse air cleaner,flowmaster exhaust .car trapped 117.5 best with this set up , them had spin tec custom do a exhaust for me and it now trapps 118.5-120

[Paul Workman]

Originally Posted by Pete

Paul,with a good ported top end (plenum & IH's) headers and good flowing exhaust our Z's run 118-120 MPH.
Even with ported heads and stock cams i would not mess with the feul tables.

Pete

Interesting. You are a Z guru, so I weigh your words heavily. However, being our Zs use derived AF (via MAP sensor) vs. a direct reading visa vis MAF sensors, the ECMs don't know exactly what the change in air flow is after porting, etc. It still determines it by indirect method; calculates air volume based on the MAP, temp, etc, etc and then refers to the on-board tables. So, if a particular LT5 (mine) was on the edge of lean w/o the added air provided by porting, etc, then the additional flow could be trouble...or at least I'm concerned (in my case - see AF graph from recent dyno run (below)).



Soooo..... Among other things, I would like to veer away from that 14.0:1 A/F ratio before doing the top end and headers. After looking at the graph, what thoughts come to mind?

P.

[-=Jeff=-]

I have a comment..

on that dyno run where was the Wideband O2 placed? I will assume tail pipe, if that is the case, don't you also have Cats? I am pretty sure the Wideband may not be as accurate as you think after the exhaust goes through the cats..

[jonszr1]

Originally Posted by LGAFF

Pete,

When you say 118-120...is that one Drag radials or Street tires?


LGAFF
92 ZR1
#234

mine was done on et street drag radials run at 22 lbs .

[jonszr1]

videos on u tube that show some of the actual runs are under bradley taylors zr1 at famoso

[XfireZ51]

Originally Posted by Pete

...Even with ported heads and stock cams i would not mess with the feul tables.

Pete

I found the need to modify both the VE and SA tables.

[XfireZ51]

Originally Posted by Pete
Paul,with a good ported top end (plenum & IH's) headers and good flowing exhaust our Z's run 118-120 MPH.
Even with ported heads and stock cams i would not mess with the feul tables.

Pete

Originally Posted by XfireZ51

I found the need to modify both the VE and SA tables.

Originally Posted by -=Jeff=-

I have a comment..

on that dyno run where was the Wideband O2 placed? I will assume tail pipe, if that is the case, don't you also have Cats? I am pretty sure the Wideband may not be as accurate as you think after the exhaust goes through the cats..

Jeff,

That along with the plug cuts I did led me to believe that even tho my dyno run showed a 12.8-.9 AFR at WOT, I decided to try "leaning" out the A/F at the top. The way to check AFR is to have the WB located at the collector and prior to the cats.

[Pete]

Paul,definately something wrong there,i would put the WB before the CATS and take it from there,also the some dyno WB's could be way off.
Most all stock LT5's get a little fat around peak torque and leanout at the top but your #'s are way off.
I would try another dyno or WB.

Recently i dyno'd with tailpipe WB and collector WB between both WB's there was .5-.7 differance at the collector it was showing me
12.3-12.8 at the tailpipe it was showing higher 12.8-13.5
Now which one do i believe?
I chose a happy medium.
I played with AFR's and to my suprise anywhere between 12.5-13.2 i did not see any gains, believe me i tried.
I like to be a little fat 12.5 at around peak torque a bit leaner 13.1 at the top.

I will have to dig up some of my old dyno sheets.

I was running 118-120MPH on GS-C's (ported intake,headers,old B&B) but would need a clutch after a day at the track.
I notice if you get good traction MPH goes up.

If you guys are going to the track with street radials and are looking to run consistent ET's/MPH you'll be pulling your hair out.

I know of a 350ci ported everything,headers good flowing exhaust,stock cams making good power with stock VE tables running 122-123 MPH in circles of course on DR's.

I bet if you guys put DR's on your cars they will run more consistent and good MPH.

If i get the time i would love to take on project ZR-1 start from scratch i.e. Jeffs ZR-1 from stock to headers/good flowing exhuast to ported intake then ported heads (stock cams).
Jeff,of course you would have to pay for dyno's gaskets/parts etc.
What do you say Jeff,that would make for a good article.


Pete