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drewbe 06-19-2006 11:54 PM

Supercharged Fuel problems
First time posting, I have BDs 1071 blower with dual 1050 holleys. We have a magnafuel 500 pump with a bypass to the tank, we installed a magafuel regulator with the boost reference and the car pops and black smokes at the line, fuel pressure is set at 6.5 and at full throttle we get 13 psi of boost which is 19.5. I disconnect the boost reference, set the pressure to 8.5 and it launches, nothing hard, but then runs out of steam, it is looking for more fuel.

We tried to run a return line regualtor with boost reference and cap off the pump, it takes the regulator pressure (6.5) and makes this the line pressure, so now I am really out of fuel.

I have read some people do not run the boost reference but some do. Can help would be helpful.


poncho62 06-20-2006 03:50 AM

moving to engine forum

Tech @ BG 06-20-2006 06:54 AM

It sounds like you have either some plumbing issues, or carburetion issues. You need to first check with Magnafuel to see how they want you to plumb the system. On a roots style supercharger you would not boost reference the fuel pressure regulator since the carburetors are above the supercharger and only see atmospheric pressure. Boost referencing is normally only done on carbureted applications when you vary the incoming air pressure to the carburetor such as in a turbo or centrifugal supercharged application. On an application like this normally you'd like to maintain between 6.5 and 7.5 psi through your entire run.

nitro_baller4692 06-20-2006 08:18 AM

just a thought.if possible in a run look at fuel pressure at wot(wide open throtle).

drewbe 06-20-2006 10:10 AM

I will try and run the car with out the Boost Reference to see what happens. The engine builder is telling me to utilize it, but two other of my friend are not running it.

Tech @ BG 06-20-2006 10:12 AM

Who built the engine?

drewbe 06-20-2006 10:13 AM

ERD in Canada

x007 06-20-2006 11:18 AM

As techBg tell, You dont need boost reference at all !
put your pressure at 6.5 and that's it, problem fixed..

Boost reference is for blownthru or turbo engine! ie: procharger/vortech/paxton etc..

drewbe 06-20-2006 12:06 PM

Thanks for the advice, We will set it and run. I will let you know.

thanks again

camaroman7d 06-20-2006 07:57 PM

The guys are telling you correctly. Your carbs can't take 19psi of fuel pressure, that's why you were getting the black smoke and poor running engine. You may want to set your fuel pressure a little higher than 6.5 psi, do a little experimenting and see what works best. No boost reference needed.

drewbe 06-20-2006 08:02 PM

Thanks, I have a bypass at the pump and a regulator without a return line. I have been told 100 different ways. Any recommendations?


Tech @ BG 06-21-2006 06:24 AM

If you're running a Magnafuel system, you should check with them to see how they want it plumbed to work properly in your application.

drewbe 07-09-2006 09:27 PM

Okay ran the car with 8 1/2 psi fuel pressue, no boost reference. Off the line the car never hit the wheelie bars, 1000ft mark it broke up. Checked the plugs lean. Added jet, still lean, added more jet, still lean. 92 primary 96 secondarys still lean. Now for the trick question, we have a base timing of 32degrees and have a boost retard for the timing that is set at 1 1/2 Does anyone run a MSD boost retard? Should we just throw it in the garbage and set the timing at 29degrees


Rick WI 07-09-2006 10:59 PM

Your Dominator can take 10PSI of fuel pressure, that's where we run our big nitrous motors. You have to confirm that fuel pressure is being maintained through the whole pass. Maybe you have but I might have missed it.

A good way to burn up a boosted motor is way too much timing. If your running 13 PSI I'd dial out at least that much timing under boost. 29, no matter what, is way too much in my opinion. Under boost the combustion process will be MUCH faster. 1.5 degress of timing taken out is not a heck of a lot.

I would assume your running decent heads if your base is 32.

Hopefully you plumbed this with -10 hose? We would normally run a bypass back to the cell from the reg versus deadhead the reg on an applicaton like this. But I think you first need to verify fuel pressure all the way down the track.

drewbe 07-11-2006 06:13 PM

Thanks for the information. We have dart heads, #10 line throughout. We are going to verify fuel is constant on sunday. Just checked the rest of the plugs and they are all white on top and half way down light yellow.

Sorry for the confusion, we have the dial to take out 1 1/2 degress per pound of boost after 2 pounds. So thats a lot of timing out of the car.

thanks again

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