Spark Plug comments

[cornholio]

03 Cobra, ported, LT's, all the bolt on's. 500+ rwhp.

Currently using TR 6's.

Last dyno, the car bottomed out the air fuel mix at under 10.0. Just at the tail end of the run it just started to register on the dyno. Obviously pig rich and I am loosing quite a bit of power (still did 490).

I checked the plugs and they are very white on the contact(s). This is the first fuel injected car that I have ever modified and I was expecting a dark colored plug in regards to the dyno stating that it was running so rich.

I have my new tune in hand with 5% fuel removed to adjust for the dyno results.

Should I be looking for a darker plug to correspond with the a/f mixture on the dyno, or is the light colored plug normal even with the low a/f mixture?

I took a couple of pic's of one of the plugs. I will e-mail to an "expert" or to someone who can post them for me on this thread.

Thanks for any help.

 

[cornholio]

t

 

[01vert]

dont bother with the plugs, get a reading on a dyno for the AF. With the AF that low be careful you dont wash out the rings. I would get another pull at a different shop and check to make sure the first AF was correct and not a bad af read.

Blowing black smoke? any other signs of pig rich? Is the car catted or catless? running the cats long that rich can burn them up. Assuming you are catless since the LTs.

 

[quick01snake]

might have better luck in the terminator section...LOL

 

[Nazman]

dont bother with the plugs, get a reading on a dyno for the AF.

I have to respectfully disagree.

Reading the plugs (when done correctly) its one of the best tuning tools available.

IOT CORRECTLY read the plugs you must shut down the car IMEDIATELY after a WOT run. Any coasting/idle after that it will give you an incorrect reading.

That white I bet it was the coasting to slow down the dyno wheels, and then some idle after the fact.

When off trottle condition occurs after a WOT run, the EEC will turn the injectors off or near off, causing an imediate lean condition. Then, at idle, when tune correctly the EEC will target (with the reading of the O2s) a 14:6:1 and the actual AF will be somewhere around there (.3-.5 point around usually leaner).

Do a 4th gear WOT run, at the very end of the run just shut the car down and coast to a stop. Pull a plug or 2 imediately after the run.

You will need a spark plug reading tool IOT do it correctly (speciall when looking for detonation).

Also, read the ground strap heat marking as well. This is very usefull when running Nitrous systems. This will tell you ALOT on your combustion temp and along with a good WB O2 sensor be able to tune your car to perfection.

That is how I do mine!

Naz

 

[cornholio]

No black smoke. No Cats. The plugs were pulled after normal driving, not following any WOT run.

As previously stated, all of my other mod cars were carb, not fuel injected/computer controlled. In the old days (carbed) if your car was running rich at WOT, it was also running rich at idle. Your point is well taken in regards to checking the plugs after a WOT run. I could see how the computer leans out the AF at idle or normal driving thus affecting the color of the plug.

The DYNO is up to date and should be accurate.

The whole problem came after I installed the LT's. Prior to the LT's, the car was tuned and running great and the AF was right on. After the installation of the LT's, the rich condition appeared. My tuner has since told me that he believed that it is because the O2 sensors are in a diff position with the LT's, thus telling the computer to dump more fuel.

I will be heading to the dyno this week and installing the programmer/new tune just to watch it on the dyno and make sure everything is alright.

 

[Nazman]

No black smoke. No Cats. The plugs were pulled after normal driving, not following any WOT run.

As previously stated, all of my other mod cars were carb, not fuel injected/computer controlled. In the old days (carbed) if your car was running rich at WOT, it was also running rich at idle. Your point is well taken in regards to checking the plugs after a WOT run. I could see how the computer leans out the AF at idle or normal driving thus affecting the color of the plug.

The DYNO is up to date and should be accurate.

The whole problem came after I installed the LT's. Prior to the LT's, the car was tuned and running great and the AF was right on. After the installation of the LT's, the rich condition appeared. My tuner has since told me that he believed that it is because the O2 sensors are in a diff position with the LT's, thus telling the computer to dump more fuel.

I will be heading to the dyno this week and installing the programmer/new tune just to watch it on the dyno and make sure everything is alright.

The point I was making about the WB on the dyno its that when the readings are taken at the tail pipe the AFR will read LEANER o/a .3-.5 of a point than when taken at the header/or before the crosover on a X or H-pipe where the reading will reflect a more accurate reading.

The LTs will make your vehicle run richer, and a re-tune should take place. Also, if you are running O2 Sensor extensions on your LTs you need to adjust the delay on the O2s to compensate on for this.

Naz

 

[01vert]

Naz, thanks for the respectful disagreement, thats why I like this board. Most people here dont jump down eachother's throat over a difference of opinion.
I agree with plugs being good IF you can pull right after a run but most nowadays can't blast then immediately pull over and pull a plug, except on a dyno. Pulling to the side of the road now can be an invite to an accident from some asshat rubbernecking or having a LEO check you out. Dunno if this is correct but seemed like I could read plugs on my old carbed 351 easy but the plugs on my other cars always come out white or close to it. May have been due to being younger and living in the sticks where it was no biggie to run hard on really quiet roads.

Again, listen to Naz on the plugs (and other stuff) as he is one of the best voices on this board