boost sensing fuel regulator

[hbhallett]

I have a 454 BBC installed in a Hallett 19' jet boat. The engine has a 4 bolt main, forged steel crank, forged aluminum pistons, LS6 heads with matching Edelbrock Performer RPM cam and intake manifold. I recently acquired a Procharger kit
and am in the process of finalizing the fuel plumbing.
My current fuel system uses a Clay Smith performance mechanical pump. The Clay Smith "Power Pumper" 1300 HP Fuel Pump surpasses any known mechanical fuel pump on the market today for efficiency and reliability. This pump will supply 14-16 PSI fuel pressure and pump 140 GHP (gallons per hour), freeflow, through their specially designed 6 valve body. This massive flow will easily handle the largest size Dominator carburetors, on gas or alcohol (per Clay Smith)
Two fuel tanks are plumbed to a T fitting and they ultimately get to the inlet of
the fuel pump via 3/8" braided stainless hose. Out of the pump the fuel travels to a Performance Products billet filter and then up to the carb hat where two bulkhead "T"s supply fuel to the carburetor inlets. Next the fuel travels out from the last T to a fitting which has a fuel pressure gauge and then finally, to an Aeromotive (p/n 13301) regulator side inlet. All other side regulator inlets are plugged and the bottom is connected to a return line back to the fuel tank.
I've noticed that at the fuel pressure gauge I have approximately 12 lbs. of fuel pressure at idle(which I think is too much). In order to reduce the pressure at the carb/gauge I presume that I should tighten / turn clockwise the adjustment screw? When I did this last night it seemed to reduce the fuel pressure by about 1 lb. but the engine appeared to be running lean so I turned it back.
I've also noticed that as I increase the throttle and spool up the turbo, the regulator appears to be static and not increasing the fuel pressure up as one would expect with a boost sensing regulator.
The boost sensing line comes from a small fitting at the carb enclosure hat and that line runs directly to the regulator 1/8" nipple?
I inquired with Aeromotive about whether this as described the proper location for fuel regulator or should I have your regulator located ahead of the carburetor inlets (again currently
the regulator is plumbed in the line after the carb inlets)? They responded that this should work as described but now I'm having second thoughts???
Any insight would be appreciated as I really don't want to melt a piston. Thanks

[Jim B.]

Hey hbhallet, I can't quite picture how your fuel system is plumbed from what you described but I will try to give some personal advise from my experiences. First of all, you said your running 3/8"(-6) braided hose throughout the system. I think 3/8"(-6) is not not going to give you enough volume, and I think many will agree. It may be fine for a stock or near motor engine but certianly not for a high performance motor. I would run 3/8 line from each tank into a Y block and run 1/2(-8) from there to the pump. Your regulator should be mounted INLINE and as close to the carb or carbs as possible. Also remember that you need to monitor the fuel pressure when the engine is UNDERLOAD, as it will give you true pressure drop. If you want a bypass install it between the pump and regulator.

[hbhallett]

Thanks JimB-- Another question for you - Should the mechanical pump be altered to sense the boost? For example, should the boost sense line also be plumbed to the fuel pump diaphragm displacing the atmosphere that the fuel pump diaphragm would normally sense?

[Jim B.]

hbhallett, I have not heard of a mechanical fuel pump being altered in that way. The only thing I've heard of is a boost referenced regulator. I don't think it's necessary to alter the fuel pump in any way. As long as the pump delivers enough volume via 1/2"(-8) fuelline and maintains fuel pressure underload you should have no worries. You should message infomanic on this forum. He is very knowledgable and I'm sure that he could add some insight...Good Luck
Jim B.

[hbhallett]

oh wise one info- any thoughts on my system? By the way the regulator is inline, although at the end of the circuit, where it either prevents or enables overflow to the return line back to the tank.
Thanks INFO!!!

[Mr.curious]

Hbhallet, Why do you want to increase your fuel pressure under boost?Are you blowing threw your carb or running injection after the blower? I am currently running the same fuel pump on a holly 850. I am drawing threw the carb so i dont need more pressure under boost. but I am running -10 fuel line to pump then -8 line to holy regulator. The regulator is next to carb and I am using the regulator as my tee which then drops down to -6 line to each float bowl. I am running 7 psi with big needle and seats. at wide open throttel 11 psi of boost (aprox 850 hp)my fuel pressure is droping down to about 4 psi. Ken B.

[hbhallett]

Mr. Curious -
Thanks for the reply; I am running a blow thru system. In my perfect world I would like to see the fuel gauge pressure at idle (and at 0 boost) at about 5-7lbs. As I apply more boost the fuel pressure would go up accordingly (i.e. fuel pump static pressure at 6lbs with 0 boost / 7 lbs fuel gauge reading at 1 lb of boost / 8 lbs of fuel pressure at the gauge with 2 lbs of boost etc.....). As I understand if the fuel pressure doesn't rise at a linear rate with the boost a lean condition exists and could result in detonation and damaged parts.
I'm thinking of changing my system to something similar as yours; fuel pump to filter to regulator between the two bulkhead T's with the return plumbed back to the tank.
Nevertheless thanks for your reply!

[flat broke]

put those filters on the suction side of a mechanical pump. Those pumps do not like to see the additional restriction of the filters.
Though I'm not running a blown motor, my setup goes as follows, -8 out of the tanks to the water seperator/filters, -8 to the fuel valve, then more -8 to the Clay Smith pump (1/2" fittings on the pump), -8 to the regulator, and then -8 to each carb inlet. I'm able to hold 6.5 lbs at WOT for sustained periods of time, but I'm also not making the HP that you are.
Good luck, BTW you can always call George at Clay Smith to get his take on how to setup his pumps. I think hed' sh*t a brick though if he heard you were going to drill into one of them for referencing
Chris

[Infomaniac]

Sounds like you are possibly trying to use a normal regulator as a bypass regulator.
The way it sounds like it is plumbed is for use with a bypass type of regulator. My favorite design.
The aeromotive boost ref regulators I have seen are supposed to be in the line between the pump and carb. (not my favorite set up).
If it is a regular inline type regulator it is just trying to regulate the presure in the return line.
You can boost ref the pump. Airplane carbs are plumbed like that. I would be very careful if you choose to try that.
Blow through set ups tend to need a boost ref regulator because the float chamber is seeing boost pressure and the fuel pressure has to be several pounds more than that to get in the bowl.
Blow through deals are hell to tune when you start really running some boost.
The carb meters fuel due to the difference in pressure between the air pressure in the float chamber and the air pressure in the venturi. The greater the difference - the more fuel flows from the carb. Blow through deals tend to equalize those pressures and thus fuel flow from the carb slows - leans the thing out - and you can guess what happens next.
Folks try and fatten the thing way up - it is way rich all of the time except when it starts making boost and then leans out.
Getting carried away here.
Check your regulator and make sure it is supposed to be a bypass type. Turning the adjustment clockwise should increase the fuel pressure on any type of regulator. 1/2 inch line minimum also all the way to where it splits to each end of the carb. 3/8 is OK there.
[ September 17, 2003, 05:31 AM: Message edited by: Infomaniac ]

[hbhallett]

Thanks Info - your insight is always appreciated. By the wy it is a bypass style regulator (aeromotive 13301). Is it possible that the regulator is too small for the pump and cannot handle the flow capacity (140 gph) that the pump provides.
As mentioned earlier I've considered changing the fuel line routing to end up with the following;
tanks - pump - filter - regulator (at the carb enclosure) - carb and finally routing the return at the regulator back to the tank. This would result in a more conventional approach.
I currently have the system routed more in line with fuel injection routing where it goes something like this; tanks - pump - filter - carb -then the regulator where the supply line deadends and then a return to the tanks supporting the bypass design of the regulator.
My thought was that the regulator at the end would always assure that plenty of fuel would be in the carbs (a more conservative approach) but for whatever reason I continue to have 12lbs of fuel pressure even though I adjusted the regulator (turned clockwise) and noticed that it actually went down to 11lbs. Strange but true.
I guess I should have purhcased one of your engines complete and then I would be relaxing and drinking beer rather than going through a remedial class in Fuel Plumbing 101.
Thanks Info
The current setup is