WOT Tuning

[XfireZ51]

With the recent results I've gotten at the track and on the dyno, I have started looking for ways I can optimize tune for WOT. I heard about doing "plug cuts" before but never took the time. This time I did. Very revealing.
Looks like its running "a bit" rich and that I have some fuel to take out. Next step is hooking up my ZT-2 at the collector. My suspicion is that the WB at the dyno is on the lean side because its at the tailpipe. Using my WB at the collector should give me a more accurate reading. Attached
is a pic of an NGK BKR7E plug on the left and an AC Delco 41-602 on the right.

[Paul Workman]

Originally Posted by XfireZ51

With the recent results I've gotten at the track and on the dyno, I have started looking for ways I can optimize tune for WOT. I heard about doing "plug cuts" before but never took the time. This time I did. Very revealing.
Looks like its running "a bit" rich and that I have some fuel to take out. Next step is hooking up my ZT-2 at the collector. My suspicion is that the WB at the dyno is on the lean side because its at the tailpipe. Using my WB at the collector should give me a more accurate reading. Attached
is a pic of an NGK BKR7E plug on the left and an AC Delco 41-602 on the right.

Interesting. I've never cut plugs before, but am very familiar w/ the concept of reading plugs. So...a Q for U:

Were either of those plugs pulled immediately after a WOT run, or was there a period of normal (closed loop) fueling and/or a shut-down and cool down and a restart? Point is, plug reading to determine fuel rich/lean, etc, is pretty quickly compromised by conditions outside those being tested - hence my question.

P.

[XfireZ51]

Paul,

The answer is that neither were pulled immediately after a run and then shutdown. However, as you look at the porcelain, there are 3 regions. Closest to the tip being idle, mid-section indicates cruise, and the bottom is WOT and therefore the need for the plug cut. Ideally, the bottom should have a wispy tan look to it. I may try to borrow my wife's tool for examining childrens ears. That supposed to work too but I had these plugs laying around and thought I'd give it a shot. After the track, I decided to try a plug one step hotter but I still need to pull fuel out of the WOT zone of the VE MAP.

[Paul Workman]

Originally Posted by XfireZ51

Paul,

The answer is that neither were pulled immediately after a run and then shutdown. However, as you look at the porcelain, there are 3 regions. Closest to the tip being idle, mid-section indicates cruise, and the bottom is WOT and therefore the need for the plug cut. Ideally, the bottom should have a wispy tan look to it. I may try to borrow my wife's tool for examining childrens ears. That supposed to work too but I had these plugs laying around and thought I'd give it a shot. After the track, I decided to try a plug one step hotter but I still need to pull fuel out of the WOT zone of the VE MAP.

I use an 8x eye loupe, but I'm too cheep to start cutting my platinum plugs, I guess

Anywayz, mebby ya need to have a spare plug or two and shut 'er down at the trap and coast into the turnout area. That way the results won't be compromised.

A quick read some may find interesting:

http://www.dragstuff.com/techarticle...ark-plugs.html

P.

[XfireZ51]

Originally Posted by Paul Workman

I use an 8x eye loupe, but I'm too cheep to start cutting my platinum plugs, I guess

Anywayz, mebby ya need to have a spare plug or two and shut 'er down at the trap and coast into the turnout area. That way the results won't be compromised.

A quick read some may find interesting:

http://www.dragstuff.com/techarticle...ark-plugs.html

P.

Paul,

As much as I would like to do that, I am more concerned with removing and tightening plugs on hot aluminum cylinder heads. Very few places where I could go thru that cycle around here so a certain amount of contamination is unavoidable.
BTW, that was one of the articles I read on plug reading. One of the reasons I got the NGK BKR plugs is that they were less expensive but provided the heat range I was looking to test. Once satisfied that I have the right heat range, I can then move up to a Platinum or Iridium equivalent.

[Bob G]

Thats what anti sieze is for I use it on the pro stocks every pass
Bob

[Starman]

Guys, as I recall the LT-5 is programmed for a 12:1 fuel/air ratio with the secondary injectors on. It will be faster if you lean it out (ideal stochiometric ratio for gas is 14:1), but it is programmed rich to protect against detonation. Let's face it, the 90-92 cars have 2nd generation ECMs and only read every 25 RPM. With Speed Density control and batch fired injectors there is not much to work with here. You can detonate the hell out of the car without it responding enough to prevent it, just on a bad tank of gas.

The 93 up cars have the P8 ECM that read every RPM. I've often thought that there would be more driveability there but have not found anyone that has made the change.

[Paul Workman]

Originally Posted by Starman

Guys, as I recall the LT-5 is programmed for a 12:1 fuel/air ratio with the secondary injectors on. It will be faster if you lean it out (ideal stochiometric ratio for gas is 14:1), but it is programmed rich to protect against detonation. Let's face it, the 90-92 cars have 2nd generation ECMs and only read every 25 RPM. With Speed Density control and batch fired injectors there is not much to work with here. You can detonate the hell out of the car without it responding enough to prevent it, just on a bad tank of gas.

The 93 up cars have the P8 ECM that read every RPM. I've often thought that there would be more driveability there but have not found anyone that has made the change.

Not to pick a nit, but I double checked and the LT5 injectors (according to my sources) are sequentially fired, unlike the L98. That notion is supported by the fact there are individual (ECM) injector control leads on the Zs - not "ganged" (L98s, etc) for what it's worth.

P.

[XfireZ51]

Here's the latest on my playing around with spark plug heat range.

First .jpeg shows ground strap heat range indication. Yoou can see that the color changes near or at the gs bend.

Second .jpeg shows the fire ring at base of porcelain. The plugs are (left to right),
BKR6E, AC 41-602, BKR7E, TR55XI. Looks like there's more fuel to take out at top end but I'll need to monitor KR and AFR using my WB. However, it tends to confirm that my suspicion is that the WB, at the tailpipe, used by the dyno operator is reporting lean.

[mrand]

Originally Posted by Starman

Guys, as I recall the LT-5 is programmed for a 12:1 fuel/air ratio with the secondary injectors on. It will be faster if you lean it out (ideal stochiometric ratio for gas is 14:1), but it is programmed rich to protect against detonation. Let's face it, the 90-92 cars have 2nd generation ECMs and only read every 25 RPM. With Speed Density control and batch fired injectors there is not much to work with here. You can detonate the hell out of the car without it responding enough to prevent it, just on a bad tank of gas.

The 93 up cars have the P8 ECM that read every RPM. I've often thought that there would be more driveability there but have not found anyone that has made the change.

I'm sorry to say that, regarding LT5 applications, there isn't much correct in this quoted post.

"Ideal stochiometric ratio" describes a chemically balanced mixture - it has nothing to do with best performance. Leaning out the AFR of a performance engine at WOT to anything approaching 14:1 is a recipe for disaster.
Has has been pointed out, the LT5 injectors are not batched fired.
The computer runs plenty fast to respond to rpm changes. The post makes it sound like the computer sits around and once every 25 rpms does something. That isn't correct. And while a bad tank of gas could cause a little detonation, there is a knock sensor which will prevent "detonating the hell out of the car." And really - do people get "bad" tanks of gas any more? Lastly, the computer used in 1993 was not noticeably different than the one used in previous years.

Marc