Welcome to Bob’s Blog! This is where Bob will post tips, tricks, and experiences he has with other racers. Check back often to read what Bob has been up to.


Friday, December 2nd, 2022

Developed from and tech info in our fuel injection publications

Fuel Pump Sizer (Pump Loop)

Sunday, November 13th, 2022

A common trend in some motorsports classes that run mechanical fuel injection is to run a bigger replacement fuel pump than previously used.  One common example is drag racing blown alcohol.  For an engine combination making just above 2,000 horsepower, about 11 GPM of methanol fuel is needed at 8,000 RPM.  Several fuel pump manufacturers have pump sizes that range around 12.5 GPM that were traditionally used for this power level.  Further information about the proper amount of fuel to the engine with mechanical fuel injection is throughout our publications.



Many racers are now replacing these pumps with bigger pumps.  Common sizes are 15 and 17 GPM pumps.  These can be equipped with a fuel pump sizer (pump loop).  That is an added fuel bypass usually connected at the fuel pump outlet, going back to the fuel tank or fuel line feeding the pump.

It is usually equipped with a jet restriction and a poppet.

That added bypass sizes down the fuel pump output, back to the needed value.



Examining one combination:

>> the setup with a 12.5 GPM pump supplies 11 GPM without a pump loop.

>> The same setup, with a 15 GPM pump and a 0.070 inch diameter pump loop jet supplies the same amount of fuel.

>> The same setup, with a 17 GPM pump and a 0.121 inch diameter pump loop jet supplies the same amount of fuel.

These setups were determined using our ProCalc fuel injection calculator and customer interaction.

All would make the same power level.  All would be tuned with the same nozzles and main bypass jetting changes for air density changes.  Spark plug readings would be the same.



The purpose of the poppet is to force all the fuel to the engine during starting.  Then it opens under pressure to reduce the fuel pump output to the engine.  The poppet size should be a low pressure such as 5 psi.



We saw setups with pump loop poppets up to 50 psi.

While this also works for starting assistance, the pump loop will not open until the fuel system gets to 50 psi.  That can be as high as several thousand engine RPM.  Operating the engine below that RPM becomes complex with that burden.

The engine is drunk rich until the pump loop opens.


At the Texas Motorplex this weekend?

Thursday, October 6th, 2022

Bob of will be in Texas this weekend at the Funny Car Chaos finals at the Texas Motorplex. He’ll be walking around wearing a hat. If you see him, stop and say hi!

Methanol Safety Tips

Friday, July 15th, 2022

Methanol fuel is very popular in motorsports.  It is common in drag, circle, and boat racing for example.  It is readily available and reasonable in price.  It has favorable properties as a racing fuel such as wide tuning window and good tolerance to high compression or high boost.  However, it is a hazardous organic compound in vapor or liquid states as well as in mixtures with other liquids.  That hazard is misunderstood by many who race with it.

Methanol Safety Information Source

Screen shots are provided from our tech manual, 5000 Horsepower on Methanol, to illustrate some of the safety issues: (more…)

Team Boddie @ Sacramento Raceway July 15 & 16, 2022 event announcement

Thursday, July 14th, 2022

Team Boddie promod drag racing; again at Sacramento Raceway. on Sat & Sun, July 15-16, 2022.

Air Density / Density Altitude / Grains of Water for racing engine tuning from ADO

Air density, track MAP LOCATION:

Air Density METRIC units, MAP LOCATION:

Air density FORECAST:

HISTORICAL air density example: &

Sacramento Raceway (916) 363 2653

Team Boddie website link

Motorcycle Drag Racing at Sacramento Raceway, California

Saturday, May 21st, 2022

Unlimited to street bikes drag racing with various other events for a weekend event.

Unlimiteds include blown nitro harley, blown nitro japanese, nitro harley, …

weather forecast by the hour:

Fine Tuning Article

Thursday, May 19th, 2022

Our latest air density tuning article:

Subtle Variations Can Make a Big Difference in a Racer’s Tune-up

FI High Speed Bypass

Sunday, March 20th, 2022

Our latest article all about the high speed bypass:

High Speed Bypass: Greater Control in Mechanical Fuel Injection Racing