Will Walbro 255 over run a MSD AFPR?

[tom04841]

Just what the title says. Input please

 

[tom04841]

Anyone?

 

[ChicksDigBoost]

I would guess your taking about there boost FPR. You would have to get there flow rates for it and see if it can handle the flow of the 255.

 

[tom04841]

Their site said it flows 9.2-10.5 gallons/hr

 

[steve]

1 gallon = 3.7854118 liters

So if your correct on the flow rate that will only handle about 40 lph.

Steve

 

[bwhughey]

I believe that the MSD rating is a MINIMUM flow for the regulator, not the maximum. Otherwise, the numbers wouldn't make sense. If you interpret the numbers on the MSD website any other way, then their own fuel pump on the same page would over-run their own regulator just below it.

I'd bet they're saying that your fuel pump has to deliver at least 10 gallons per hour at 45 PSI for their FPR to work properly. Which, frankly, would be an easy feat for any EFI-rated fuel pump unless it was broken. ;-)

The stock DSM pump is about 26 gallons per hour at 12 volts.

That said, I've never over-run a stock Mitsu FPR with two different Walbro 255 HPs (341) in my 1G. That's about 67 gallons per hour. So the MSG would work fine, IMHO.

Regards,

Brad

 

[99gst_racer]

What is MSD's part number?

 

[tom04841]

I just called the MSD Tech Rep, and he said at 36-45 psi, the regulator will flow 9.2-10.5 gal/hr. He said the Walbro 255 i have will not overrun this afpr.

If my math is correct then, 9.2-10.5 gal/hr at 36-45 psi, would flow 580-660cc/min

Works for me since i want to upgrade to atleast 550's


Oh yeah, the MSD part # for this is 2222

 

[99gst_racer]

Oh yeah, the MSD part # for this is 2222

Interesting find. I never knew MSD was selling this. How do you plan to connect the regulator with the rail? This has a barbed fitting instead of AN fittings, so I was just curious about your plan of attack.

Also, please consider posting a tech write-up for this and maybe even a product review on it. This would be an extremely affordable solution for people that are overrunning their stock regulator.

 

[tom04841]

i have a fuel rail adapter that has a hose barb. So all i need is sone fuel injection line and some clamps. I'll do a review and write up once i get it in, which will probably be a month or so.

One more thing i need to double check on.

Base fp should be set to @ 38-39psi (with vac off). Now if i wanted to be cheap and hold off on the 550's, couldn't i bump up the base fuel pressure to @ 58psi?

New fuel pressure: square root of 58 = 7.615
Original fuel pressure: square root of 38 = 6.164
Then divide the new fuel pressure square root sum by the original.
7.615 / 6.164 = 1.235
Then multiply this total by the size of the injector.
1.235 x 450cc= 555.75cc

And yes, i have an SAFC to compensate if my math is correct.

 

[pneumo]

Some of your math is correct. The part about raising your fuel pressure is good. 58psi will make your 450's act like 555's.

The part where you say that 9.2-10.5 gal/hr flows 580-660cc is off by a factor of 4 since you have 4 injectors.
4x555=2220cc/min
=2.22L/min
=133.2Lph
=35.19Gph

Just FYI, raising fuel pressure will narrow the spray pattern of the injectors. I've played around with this a little and found that it doesn't seem to make any difference at WOT, but idle and part throttle cruising isn't as smooth.