Single channel O2

[Bob Pagano]

Hay Mike, You hooked up with one of the best out here. Ed really knows his stuff. Looking forward to you getting after it !

[Michael Beard]

Question: Would your "proper" target A/F ratio possibly be different in ohrrendously different conditions? 4600' and a vapor pressure over .90 this weekend, and it seemed like it went lean when I tried to take enough fuel out of it to get the A/F close to where I had the car running decent at MIR.

Also, when I do get around to doing the "pit driving" tuning with some mufflers on the car, what kind of A/F do you look for in comparison to your WOT A/F? Still much leaner? Seems like the example programs have it up in the 15's at low rpms?

[Ed Wright]

Driving on the return road and pits should be 140.0-1 to 14.5-1 to keep the plugs clean. Leaner usually makes them run warmer. Mike is happy at 14.0-1. Decelleration, 15-1 is usually OK. You can see all kinds of crap on tuning message boards.
You just have to test in different air to find what air/fuel yous likes. Mine likes about the same all the time. I can't say what a Dodge with that manifold would like. Renting the track in different weather is helpful.
Good luck, Ed

[Michael Beard]

I take a boatload of fuel out of it yesterday at low rpm through launch rpm, and a little in the burnout area of the fuel map. Went a smidge too far right at launch rpm on the first run, but just a little tweak got it to leave cleanly again.

Going back over notes, I'm having to run this thing richer now than I did last month, just to get it to go down the track. If I take any fuel away from it, it quits making power (never pops like being too lean with a carb -- it just noses over.) A/F around 11-11.5 during most of the run, a couple spots in 2nd or 3rd gear where it gets into the low 12's, but now I've noticed a couple of rich spikes (10+, not prolonged, just at a singular point on the data log, one in 2nd gear, one in high gear... only did it the last couple runs)

Something I've noticed from day 1 is that the rpm doesn't come up smoothly, and it seems more pronounced now as time goes by. It'll have just an instant of a drop of as much as 300 rpm here and there... fluttering off and on. Shows up more in the data log than what you can feel in the car. This weekend, at least with the borrowed 4-hole spacer, even at idle it was moving around.... 1000rpm for a second or two, drop to 600 for a second or two, then back up, back down, etc.

Theory: bad injector? One or more injectors not working properly, causing the intermittent rpm surge, which has me richening up the whole system too much trying to compensate for poor or surging flow on just 1-2 cylinders, then being down on power when I try to lean it out?

We're going to try to do some kind of injector test tomorrow.

[Ed Wright]

Michael, find a local shop with a bench top injector cleaning and flow testing set up. Number your injectors when you pull them. Scribe the cylinder numbers on the injectors because the cleaning fluid often removes numbers written with a Sharpie. Have them flow test them before and after cleaning, recording each injector's flow rate. Most shops just want to clean them first, they will charge you extra to flow them both ways, but that's the only way you will know. It shouldn't want to run best with air/fuel in the elevens. Mine likes mid twelves. Some like low 13s.
Good luck

[Adger Smith]

Micahel,
In this hot humid weather when you see a little area of the curve being rich. don't try to lean that area out. leave it rich and hit that part of the map with a little timing. See if the engine combo likes that. Some do some don't. It might make a little steam out of the humid air. :~) Oh! Watch the egt's in that rpm range. They should go down a few degrees when you hit it with timing. That is because the heat stays in the chamber, not in the ex pipe.

[Michael Beard]

Been running 38deg, except for down low, had it at 32deg (3000-5400rpm)to get it to hook previously. With the CalTracs (plus being down on power), had absolutely zero hook issues this weekend, and bumped the timing up to 38deg across the board.... only worth .01-.02. Even started putting clicks in the shocks, and the car shrugged its shoulders.

But even in much better air, similar deal... try to lean it out at all, and it noses over by 12.5:1 at best.

[Adger Smith]

The fuel and timing go hand in hand. Watch the EGT's when working the fuel and timing. Usually, as you lean the engine it will want less timing to make power. When you have it fat it usually takes more timing to light the mixture because there is less air (O2) around the fuel. Same goes for more vapor pressure. It displaces the o2. As an example I'll try to post a PM I got from a racer I was helping tune in bad air. oops, Sorry already deleted the exchange.

[Altronics]

O2Alert features single or dual widbands plus RPM and Battery voltage standard. Has Auxially inputs for EGT, Drive shaft RPM, and Pressure/Temperature/ voltage.

Data can be read back on screen or comes with software to download to a computer and graph/overlay.


THis system also features automatic recording capability, so that there is NO user interaction required to start recording. You can sit in the lanes for hours and then make your run and do not need to remember to push a button!

Also features AFR average which is very useful in determining what tune up change has effected performance. In carbed applications fuel slosh can cause fluctuations in AFR. I like to be able to look and the entire run and see not only what the AFR is a specific points but more important what the average AFR is.

Also, This is a CONTINGENCY item!

See our website for more info www.altronicsinc.com/pages/o2alert.html

[Michael Beard]

First thing we did today was physically check the timing at the balancer, and lo and behold, it was reading around 30 degrees, not 38! It's more than a little disconcerting to me that it could've moved that much in the first place, but it sure does explain the car running like a pig lately. It's a FAST Dual-Sync distributor. We went through the setup procedure again, checked it against the timing light, and tweaked to match. We marked it before going through setup again, and you can see the distributor is definitely in a different position than it was.

Just goes to show you can't overlook the basics, even if it "shouldn't" have happened. Hindsight, Sherlock Holmes, Occum's Razor, etc, etc.... I'm sure I'll have to punch the fuel map around a bit again now, but feels good to have actually found and corrected something that is a definite problem.