The web description for “Fuel Injection Racing Secrets” is currently in revision for a 2nd edition. Please notify us if you have any problems viewing or ordering this book.

I had an interesting email exchange with a very knowledgabel and astute racer that I thought I would share. I’m happy to see he noticed the differences:

I noticed an error in the “Superchargers for IHRA” article…

“One way of looking at where all of that power came from is to look at the
displacement of the blower. The 6-71 displaces a little over 400 ci per
revolution (6 x 71 ci).”
(more…)

Received this email from a knowledgeable racer:

Crew of an A-Fuel car (nitro)
Bought all your books. Excellent reading.
However, my calculated AFR number gives unreal value. How can I make this applicable to nitro?

(more…)

Question: Different racers get different boost readings (more…)

QUESTION: Do any of your books help in areas of tuning with using O2 sensors? I am needing some what of a baseline for a good tuneup using the correct nozzles, pills to help with getting the most or should I say most consistent in drag race ET’s. Of course everything being the same.

Thanks for replying, R. in Texas

Hi R in Texas,
Thanks for your inquiry. Our Jetting for Racing Mechanical Fuel Injection … book has info on O2 sensors including accuracy limits.

REPEATABILITY VS ACCURACY: O2 sensors are a great tool, however, the accuracy (especially for methanol or ethanol) and repeatability may be issues. Accuracy is less of an issue if they are repeatable. (more…)

Message: in your fuel injection book, you show a vacuum gauge with a telltale,
do you know where to obtain one of these gauges? KS

It is not a vacuum gage but a pressure gage. You probably
want a 0-200 psi, liquid filled, tattle tale gage. (more…)

Question: Effect of lowering blower overdrive?? More or less power?
Bob?s answer: A trend now is gearing the blower to the racetrack. That is done with rear end gearing, tire size, shift point, and blower overdrive. Adjustment of any of those will change the speed attained by the blower at the end of the drag race or the straightaway.
(more…)

Question: Can we put an 8-71 blower on a high output, normally aspirated Big Block V-8 with very high compression ratio (15 to 1)?
Answer: The detonation can be controlled with enrichment and air to fuel ratio control, theoretically regardless of the compression ratio. However, I am not sure about the mechanical strength of the components.? With that real high compression using a blower and a wedge head, the power stroke starts on one side of the dome. If you are using short skirt pistons or pistons that are not full circumference at or below the wrist pin (typical of normally aspirated high output engines), you may have a problem with skirt deflection, breaking a piston, or galling it. An 8-71 Roots blower, at 10% overdrive, theoretically pumps the same amount of air as an engine approaching 900 cubic inches. The math for that is in Fuel Injection Racing Secrets. Stuffing that amount of air into your BB engine gets a lot of boost and loading. FYI; Our book 5000 Horsepower on Methanol provides information about actual compression ratio with supercharging including simple math on how to determine it.

Question: How did you dial in your mechanical fuel injection setup for bracket racing?
Answer: Our tune-up is set up to be in a linear range. That is when we increase the shift point, our ET is proportionately lower. When we lower our shift point, our ET is proportionately higher.? That is a result of many characteristics from our combination, some intentional and some accidental.

I recall a setup many years ago that was not linear. If you raised the shift point beyond a certain point, you slowed down. The cylinder heads were small and acted as the limiting factor in the combination.

The subject of linear is an extensive one. Keeping everything moderate is a good step in that direction: moderate timing, launch point, shift point, and fuel enrichment. In our case, we know what our air to fuel ratio is from jet area and air calculations from Fuel Injection Racing Secrets. We know our rich air to fuel ratio limit and our lean air to fuel ratio limit and we keep in the middle. It is difficult to get there without record keeping and some calculations or data measurements. And we found that method to be very repeatable year after year after year. And once we found it, we race in that range and never had to recalculate or find it again.

Question: We want to race with a Roots blower. There are standard Roots blower bottom openings, and there are smaller ones. Some with a small pie shape towards the front. What is the influence from the size of blower output opening
(more…)