fuel pressure regulator choices ( specifically Magnafuel )

November 23, 2021, 10:26 AM

sc4087

Anybody have any issues running pretty strong combos on their small 2 port regulator? web site claims small regulator is only good for 750 hp, large regulator for over 1000 ? I have one car plumbed with a large 2 port, one with a small 2 port, one with an old BG 4 port and heck even my TD car is plumbed with an old school holley 12-803 regulator and I fail to see any issues with any of them no matter which combo we put in any particular car. Any where from 1050 to 1400 combos. I'm putting an older car back together with all new stuff and was going to buy the smaller one because of the mounting and price difference.

November 23, 2021, 10:39 AM

1320racer

Magnafuel 2 port regulator #MP-9833-BLK feeding 1300HP via two -6an lines

November 23, 2021, 10:44 AM

NC3x58

For what it's worth, we have been using a Holley 12-843 Billet unit with -10AN inlet and two -8AN oulets. Have one -8 line running to a fuel log and have used it on a 1025hp 565 running gas and a 900hp 572 running alcohol and it feeds it just fine using a PS500 pump and A2000 on two separate cars, both running 16V batteries. We went with this regulator as it has the larger orifices for the volume of fuel needed, and on the nitrous side we use the smaller 12-841 Billet unit with both on a Magnafuel log with a -10AN feed line to feed the fuel side and have never had an issue with these regulators.

November 23, 2021, 10:50 AM

sc4087

MP-9633 vs MP-9833 is my question

November 23, 2021, 10:54 AM

NC3x58

MP-9833 would be my choice.. Unless it's just a backhalf doorcar running a sbc and making less than 700hp, even then, consider the larger one for upgrades down the road etc.

November 23, 2021, 11:02 AM

1320racer

The only difference is the outlet size, 9633 is -6 and 9833 is -8

November 23, 2021, 12:43 PM

369dragster

I run the same set up as Ed, except it's mounted to a Magna fuel log with a little holley for the nitrous.

November 23, 2021, 01:11 PM

Al Alguire

I prefer the Weldon stuff myself. The carb regulator requires no tools to set it.

November 23, 2021, 01:33 PM

TonyB6255

quote:
Originally posted by 1320racer:
The only difference is the outlet size, 9633 is -6 and 9833 is -8

Not true, the diaphragm is larger on the 9833. When I was at Sunset earlier this year we took them both apart to compare. Magnafuel tech told Joe at Sunset the 9633 diaphragm will begin to flutter with high fuel volumes.

November 23, 2021, 02:06 PM

CURTIS REED

quote:
Originally posted by TonyB6255:
quote:
Originally posted by 1320racer:
The only difference is the outlet size, 9633 is -6 and 9833 is -8

Not true, the diaphragm is larger on the 9833. When I was at Sunset earlier this year we took them both apart to compare. Magnafuel tech told Joe at Sunset the 9633 diaphragm will begin to flutter with high fuel volumes.

Did you check to see if the 9833 had a larger orifice?

November 23, 2021, 02:07 PM

1320racer

You’ve taken both apart, I haven’t but aren’t they the same size? If so how can one have a larger diaphragm?

November 23, 2021, 02:18 PM

CURTIS REED

They appear to be different overall size by the pic on Magnafuel's site.

November 23, 2021, 02:23 PM

sc4087

They are different size. I've run them both on typical dragster setups running in the 4.40-4.70 range and they both seem fine to me. Magnafuels website states the 9633 is good for 750 plus hp. and the 9833 is good for 1650 plus. Well, 750 plus how much? Don't need 1650 hp regulator. Hence my original question

November 23, 2021, 04:28 PM

TonyB6255

quote:
Originally posted by 1320racer:
You’ve taken both apart, I haven’t but aren’t they the same size? If so how can one have a larger diaphragm?

When you set them side by side the 9833 is larger, but not by much.

November 23, 2021, 04:31 PM

TonyB6255

quote:
Originally posted by sc4087:
They are different size. I've run them both on typical dragster setups running in the 4.40-4.70 range and they both seem fine to me. Magnafuels website states the 9633 is good for 750 plus hp. and the 9833 is good for 1650 plus. Well, 750 plus how much? Don't need 1650 hp regulator. Hence my original question

When I was at Sunset's shop we had that same question. Joe Jolly called them and said the way it appears is the 9633 is good from 750-1650 and the 9833 is good for more than 1650.

He confirmed that the 9633 should only be used up to 750hp because of the smaller diaphragm having a tendency to flutter and lose fuel pressure down track when fuel volume is high.

November 23, 2021, 04:43 PM

sc4087

quote:
Originally posted by TonyB6255:

He confirmed that the 9633 should only be used up to 750hp because of the smaller diaphragm having a tendency to flutter and lose fuel pressure down track when fuel volume is high.

I need somebody smarter than me to convince me that a fuel pump putting out 500 GPMS @ 25 psi then regulated down to 7-8 psi can run out of volume and cause a regulator to " flutter " down track. None of our engines that we all use can handle 25 psi @ wide open throttle so if the so called " little regulator " can handle the pressure at idle when it would be most likely to overpower it and make it flutter I don't see it failing @ wide open throttle? Like I said I run my top dragster car with 3 kits on the same fuel pump and 3 holley 12-803 old school regulators with zero issues. Just asking, maybe there is a liquid, volume, flow expert amongst us?

November 23, 2021, 05:07 PM

TonyB6255

quote:
Originally posted by sc4087:
quote:
Originally posted by TonyB6255:

He confirmed that the 9633 should only be used up to 750hp because of the smaller diaphragm having a tendency to flutter and lose fuel pressure down track when fuel volume is high.

I need somebody smarter than me to convince me that a fuel pump putting out 500 GPMS @ 25 psi then regulated down to 7-8 psi can run out of volume and cause a regulator to " flutter " down track. None of our engines that we all use can handle 25 psi @ wide open throttle so if the so called " little regulator " can handle the pressure at idle when it would be most likely to overpower it and make it flutter I don't see it failing @ wide open throttle? Like I said I run my top dragster car with 3 kits on the same fuel pump and 3 holley 12-803 old school regulators with zero issues. Just asking, maybe there is a liquid, volume, flow expert amongst us?

My thoughts were the same as yours and I had bought the 9633. How this tear down and phone call happened was while racing at Holly Springs earlier this year, my 632 9* headed engine went dead lean down track. I was driving around my opponent at half track and then suddenly I wasn't. I had the 9633 on there because of the description on Magna Fuel site.

Fuel pressure dropped to like 2 lbs. The only thing that we could find was the 9633 regulator so we called Magna Fuel tech line. Joe had a 9833 there so we tore them both down side by side. The only real difference was the size of the diaphragm and like Ed said the outlet size.

November 23, 2021, 07:20 PM

1320racer

All I know is the 9833 works without issue, it was on my car from day 1 and I have a spare if it shyts the bed.

November 23, 2021, 07:54 PM

green1

quote:
Originally posted by sc4087:
[QUOTE]Originally posted by TonyB6255:

He confirmed that the 9633 should only be used up to 750hp because of the smaller diaphragm having a tendency to flutter and lose fuel pressure down track when fuel volume is high.[
I need somebody smarter than me to convince me that a fuel pump putting out 500 GPMS @ 25 psi then regulated down to 7-8 psi can run out of volume and cause a regulator to " flutter " down track. None of our engines that we all use can handle 25 psi @ wide open throttle so if the so called " little regulator " can handle the pressure at idle when it would be most likely to overpower it and make it flutter I don't see it failing @ wide open throttle? Like I said I run my top dragster car with 3 kits on the same fuel pump and 3 holley 12-803 old school regulators with zero issues. Just asking, maybe there is a liquid, volume, flow expert amongst us?

The pump isn’t running out of volume the diagram in regulator just starts fluttering shutting off fuel flow momentary causing low volume. One way to test is to remove your fuel lines from carb and pump straight into a jug and see how much you get. I think I have been told a gallon of gas in 20 seconds is good. This test is testing your system as installed.