Re-tune needed after installing Racetronix fuel pump?
Thread Starter
Racer
Joined: Feb 2005
Posts: 332
Likes: 22
From: Georgia
Re-tune needed after installing Racetronix fuel pump?
Just finished installing a Racetronix fuel pump and wiring kit on my heads/cam ‘02 C5. This kit uses the Walbro 255 pump. It’s running around 480 RWHP, and the stock fuel pump finally died suddenly.
Will I need a retune with the new, more powerful fuel pump or will the regulator handle the pressure, reduce it, maintain the required pressure for optimum performance? Thanks for any insights.
Will I need a retune with the new, more powerful fuel pump or will the regulator handle the pressure, reduce it, maintain the required pressure for optimum performance? Thanks for any insights.
Last edited by Meta; Feb 15, 2026 at 11:06 PM.
Pro
Joined: Jan 2001
Posts: 649
Likes: 347
From: San Jose CA
Shouldn't matter. The fuel pressure regulator keeps pressure consistent, fuel injectors will only flow as much fuel as they are programmed to.
You've added a larger hose behind the sprayer, but the sprayer doesn't change.
You've added a larger hose behind the sprayer, but the sprayer doesn't change.
Melting Slicks
Joined: Dec 2018
Posts: 2,663
Likes: 1,389
From: Orange County, CA
If there is a chance the original fuel pump wasn't keeping up at higher power levels and thus dropping pressure, then I will disagree with the other posters. Since these cars don't have a wideband O2 sensor they can't monitor AFR beyond part-throttle, and it's possible you could be running rich with the new pump if the old pump was providing insufficient pressure at higher power levels and less than the new pump.
I'd say just try it out with the new pump and (assuming you don't have a wideband) check for symptoms which could suggest it's running rich.
I'd say just try it out with the new pump and (assuming you don't have a wideband) check for symptoms which could suggest it's running rich.
Thread Starter
Racer
Joined: Feb 2005
Posts: 332
Likes: 22
From: Georgia
Thanks for the insights, confirming what I’d hoped, that I’d probably be fine without a new tune. The old pump wasn’t struggling to keep up as far as performance, maintaining pressure, it just died suddenly, wouldn’t start one morning. In fact, I do have a wide band installed on the car and will monitor A/F ratios. It’s good to be OCD sometimes.
Drifting
Joined: Nov 2017
Posts: 1,392
Likes: 303
I agree that this shouldn't require any tuning.
And I agree with confirming that your AFR doesn't change at full power.
If it gets richer then it's possible that the current tune was compensating for a weak pump.
But it's also possible that the pump weakened after the original tune, and until recently it was running leaner than intended at full power.
The only way to know which would be to monitor knock.
If it's not knocking, I wouldn't change anything.
And I agree with confirming that your AFR doesn't change at full power.
If it gets richer then it's possible that the current tune was compensating for a weak pump.
But it's also possible that the pump weakened after the original tune, and until recently it was running leaner than intended at full power.
The only way to know which would be to monitor knock.
If it's not knocking, I wouldn't change anything.
