by Dave Koehler


Hi Dave - Mad Coater here,

I occasionally run a Crower injected Alky RED [newly retired on 10/1/03 = less play time $$$, but it’s my test bed, so off I must race] to test my latest coating blends and/or mechanical inventions.

I’ve been experimenting with O2 sensors as a better way to tune for overall fuel mixture. EGT sensors are nice for cylinder to cylinder reference [helps when the nozzles can be fine tuned], but I’m thinking that a good Lambda sensor could help the OVERALL tuneup and final bypass pill setting(s).

We’ve been building and refining our own O2 sensor kits for a year now - seems to work pretty well on both gasoline and Alky. What are your thoughts on this type of sensor feedback?

Bruce T. Corneto
[The Mad Coater]
Occidental, CA


The five wire heated sensors will work in the rich A/F range that race cars run in. This is particularly useful for nitrous, blowers and mechanical injection combos that have, by their nature, excess fuel to deal with. As much as I like some of the high tech stuff that has come along, this is one of those things I have not tried. Here is my take on this.

I question that if we know the A/F going down track, how many more opening and closing poppets, solenoids, timers and relays will we need to make use of this information. It’s a good news/bad news kind of thing.

The Up Side:

When used in conjunction with egt sensors the lambda sensors can allow you to determine whether a high EGT is due to being too lean or is being generated by too much fuel burning in the pipes. This may or may not be easier, time wise, than the poor mans Lambda meter, the spark plug and ET slip, but one does get a number to look at and ponder plus the cool factor is way up there.

The Down Side:

Due to the costs of this technology a racer is limited to using these with collector headers and you still need two sensors plus an interface to your data logger. Zoomie headers are pretty much out of the picture at this point because just reading one or two cylinders will probably confuse more than clear up the overall picture.

The Far Side:

I don’t think there is any question these can be used along with plug reading, EGTs and ET slips to make tuning decisions that much easier ... or more confusing. While I may never get around to trying this it is certainly a viable tool that bears study. I just don’t know if the time has come for it to be considered a “must have” necessity on a drag car.
OK, my answer was ulterior motivated. I will ask you to write an article on this subject along with your real world experiences and observations and submit it to DRO. The editor loves tech articles and you may convince me to spend more of the kids’ college money.
Have a safe race

Dave Koehler



Thanks for the informative response to my first question. I have a follow-up. By factoring in the inlet air temp you can derive a corrected EGT, which is quite lower than the actual reading. Which temp is more important to tuning? My “gut” feeling is that no matter what the factored EGT reading is (usually 100-200 degrees lower), the actual EGT temp is what the exhaust valve and the rest of the exhaust system (and turbo) is subjected to and you should be tuning based upon that. How do these two temps relate to each other?

Also, when changing from a 1 bar to a 2 bar MAP sensor, should the kpa readings stay the same? When the ignition is turned on (without the car running) the MAP sensor will read the atmospheric pressure. Since both read a 0-5V signal and you have now doubled the range, should the 2 bar have a higher reading than the 1 bar at the same pressure?

Tom Drake

Drake Coatings Inc.



Interesting. I never gave something like this a thought. I know just enough about the electronic side of EFI to be dangerous, but the end game is the same. I would use the exhaust egt for cyl to cyl adjustments. Once you know what the engine likes, you can see if there is any correlation between the inlet and the exhaust temps that is useful.

Question 2: As I see it, a 2 bar MAP just allows higher boost pressure (29 lbs.) to be used and measured. If the new sensor also reads 0-5V, then a parameter has to be changed in the software so that it knows that it now reads 0-29 lbs. or whatever type of number you need to see. It is normally input as a millivolts figure. At least that’s the way sensors and software I deal with works.

Have a safe race,

Dave Koehler

To contact Dave Koehler write fuel@dragracingonline.com


Previous Stories

Fuel for Thought — 5/7/04
Dave Koehler answers your nitrous & fuel-injection related questions

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