Fuel Pump Speed Control - PWM

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Turbo6inKY

Active Member
Happy to report I installed this tonight, and it works like a charm. Started on the first crank. Just using the duty cycle map from your instructions until it gets warmer and I can get to a track for some better testing, but I'm excited. I was seeing some pretty stupid fuel temps last summer.

I made a PnP harness that splices into my RaceTronix pump hotwire kit. The only wire I had to run was the single conductor up to the evap solenoid connector. It took longer to tuck that wire into the hotwire harness than to install the rest of it.

Thanks! for the instructions!
 
T

Turbo6inKY

Active Member
And here's the results. A short jaunt in the car before the controller (bright white) and after (gray). You can see in the same amount of time, the oversized pump put almost 12 degrees of temperature into the fuel.

Afterwards throttling it to 60% with the PWM controller when MAP was at 100kpa or less, it's effectively flat.

1642040133253.png
 
TexasT

TexasT

Member
Good info . I'm looking at doing a pwn setup with a dw400 to run e85. The dorman relay with the heat sink I'm guessing needs to be mounted where it will get some airflow to cool it. Might this be in the behind grille on the core support or just on the fender liner?

Thanks for any input
 
ShaunKris

ShaunKris

Well-Known Member
EricM said:
Here in updated article on setting up speed control for your fuel pump, if you have a large pump that needs to be slowed down at idle or low load.

Updated Oct. 2021

Click the following link:

Click to expand...
Hi Eric great info here, when would you say you have an oversized pump? For example I just installed a 450lph pump in my car with a racetronix fuel line kit and a motion raceworks flex-fuel bypass. It's a hot-air car with 60lb injectors. I am installing the ECUGN as well as the new Digital dash from DDEFI.com. Richard Holdner did a test on fuel temps and discovered that it doesn't change anything really as far as the tune goes but I get why you wouldn't want to increase temps ANYWHERE. I guess the question is how do you determine the return line size for any given fuel pump..
 
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EricM

EricM

Administrator
Staff member
As long as you can adjust fuel pressure at idle to be in the 38-43psi area vac line off, and then it drops 5psi or so with vac line on, then you should be fine. In general, on the Buicks, anything much over 255LPH will likely require a bigger fuel return line, or you won't be able properly control fuel pressure at idle.
 
ShaunKris

ShaunKris

Well-Known Member
EricM said:
As long as you can adjust fuel pressure at idle to be in the 38-43psi area vac line off, and then it drops 5psi or so with vac line on, then you should be fine. In general, on the Buicks, anything much over 255LPH will likely require a bigger fuel return line, or you won't be able properly control fuel pressure at idle.
Click to expand...
Ok good to know, I do have the #6 return line so that's probably good for now. Thanks!!
 
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