MSefi.com read only forum (Jan.15,2018)

I'm putting a megasquirt on my mopar 360 running a chevy TBI system. I have a pump here that flows a max of 8psi / 100gph.

I need to run around 20psi to get the desired 100lb/hr for the injectors.

I figure since the inlet/outlet is so big on the pump that the PSI would increase with the small fuel line???

Or what is a good pump thats not going to cost me alot to use??

thanks

it is this pump here: http://store.summitracing.com/partdetai ... toview=sku

Im running this Holley. I have heard others complain about the noise of electric pumps. I can only hear it when you first turn the key on. I cant hear it at all with the motor running even when I listen for it. I have stock mufflers so the car is not unusually loud. My 05 dodge and 97 chevy I can easily hear them if you stand outside the car so its not just my bad hearing.

Specifications for 12-927:
# For use with Throttle Body or Multi-Point Fuel Injection
# Supports forced induction
# 60 GPH flow @ 15 PSI (at 13.5 volts)
# 258 PPH flow @ 15 PSI (at 13.5 volts)
# 3.5 amp current draw @ 15 PSI
# 43 GPH flow @ 45 PSI (at 13.5 volts)
# 180 PPH flow @ 45 PSI(at 13.5 volts)
# 8 amp current draw @ 45 PSI
# Supports Throttle Body injection up to 400 HP

I mounted mine to the flange on the tank with 'beam clamps' from my local home store. Not sure if mopars have the same flange.

You might try this one:
http://www.jegs.com/p/MSD/752083/10002/-1/10307
You'd need a FPR, but I think you'll need one anyway.
As far as the pressure increasing with smaller line size; I think the PSI rating is with the lines "full" of fuel. In other words, the pump is only capable of 8 PSI, regardless of line size.
Just my 2cents.

so the one i linked to will not work? Since that puts out under the needed 20psi??

Correct. It will not work.

Ok thanks fellas!

I looked at the MSD pump and it looks like it would do the job. Now next question, whats a good regulator to run with a return fuel system??

I used one of the cheap MSD ones - they're rebadged Bosch units that are about as cheap as most OEM regulators I've seen.

awsome thanks! i'll have to check for it.... do you have a part number off the top of your head? if not i'll search

Do the stock TBI units have a regulator you could scavenge?

They do, but wouldn't comming from 45psi from the pump to 20at the tbi cause it to brake??? i figured youd have to step it down, than step it down again????

I think the stock GM one is almost the same as the holley one I have and the regulator is built into the body. The holley one you have to pick a plug out of the cover so you can adjust it, not sure if thats the same on the gm one. The pump I posted is what I am running on my holley. I dont remember the range on mine but 20 was possible, I think I ended up running around 14. One thing to watch is the size of your return line, I think they say you should have no more than 3 psi at idle. Any more and you need to slow down your pump (which could cause you to starve at WOT) or get a larger return line.

Do you have the larger 454 TB?
Which injectors do you have?
Is your engine really built? Like high comp, nasty cam, and expecting to turn high R's? If its just slightly over stock I would think you would be fine with the regular GM TB and the larger injectors and not have to worry about boosting the fuel pressure. I have heard that the GM injectors dont respond well to higher pressure and also tend to leak. Im running the equivalent of the 454 one on a 500 and as far as I can tell I am no where near the limits of anything. I have too much throttle response that I hope to mellow out with timing control. In my car its rare to get it over 3K and I doubt it would spin much over 4 in its current state. My motor is not what I would call 'built', its just 'updated'.

its a mopar 360 bored to a 365. Hyperutectic flat top pistons, extreme comp cam hyd. flat tappet, around 10:1 compression, headers

so its a little built.

What kind of RPM's do you expect to be running? If you are expecting to spend much time much over say around 4500 the stock chev 5.7 stuff may be a bit thin and you may want to look for the larger 454 stuff, the Holley upgrade for the GM's, or an old Projection like I have and dump the analog ecu. The 454 one and the 670 holley 2bbls were rated for around 300 HP which is got to be the range you are in. I think the stock 5.7's were lucky to be 200-225. Holley also makes/ made some 4bbls that can be had cheap on craigs list and ebay used. There are some smaller ones along with the 'big' one that was rated 900cfm and had 4 85lb hr injectors. I think that one would be tough to get to idle well on most engines. I have one but have not messed with it yet. Its hard to get a good idle with the 2 85's I have now but my motor is fairly close to stock and should idle nice and smooth around 500 rpm in gear. If you have a more aggressive cam you may not be trying to idle that low anyway and the larger injectors and or higher pressures may not be a problem for you. The larger the injector is the slower is is to respond to open and close commands (just because of the physical size of the valve I assume) so you run into a problem getting large injectors to open and close fast enough to dump a small amount of fuel at idle. Thats a reason to go to multiport, more smaller injectors that dont have to operate over as great of range so the result is better control.

Maybe starting with the GM one would be good to get things figured out but you may end up going with one of the many fancy 4bbl TBI's that are out there now. Many of them use the Bosch style multiport injectors. There is even a few people that make them that have covers over the injectors so they look just like a big old holley double pumper.

73Eldo: I think my rev limit is set to 5,500k rite now with my MSD6-AL box. When I do drive up the sand dunes or through a mud pit, the RPMs will be high.

As for using a 454 tbi, I have thought about it. However I have done the math and it shows the 350 tbi will flow more than i actually need. The injectors I need will be 100lb/hr. So using 454 80lb/hr injectors boosted to 20psi, i will achive this.

Like you said, It will provide me with a good starting point. I'm lucky enough that my dad works for ford and does the calibrations on the cars, focus, fusion, now brazilian cars. He knows how to do all the math and can calibrate my jeep with his eyes closed

Plato2k5 wrote:They do, but wouldn't comming from 45psi from the pump to 20at the tbi cause it to brake??? i figured youd have to step it down, than step it down again????

That is no problem at all - two regulators in tandem is actually more problematic. The fuel pressure is only going to be what your regulator allows it to be, no more. So if the TBI unit has a 20 psi bypass type regulator, you will have 20 psi through the whole supply line (not counting the slight pressure drop down the line). Just because a pump is rated for 80 psi doesn't mean it is putting out 80 psi.

ok so if i purhcase that MSD pump, I will not have to regulate the fuel flow as the fuel pressure regulator on the tbi unit itself will regulate it down to what i need?? I just have to adjust it to 20psi, throw a gauge on it, check it and call it good without any worries?? Than whatever is left, will be sent down the return line.

I've never messed with this stuff thats why the 100 questions. I would just like to do this ONCE and have it done rite.

thanks everyone!

Now you got it. If you have only 100 questions, then you are doing pretty good.
I'm glad I could help someone else.....ask away.

One thing to realize about pumps is that they do NOT create pressure, the restrictions in the system create the pressure.

A pump creates FLOW, and is rated for the flow volume it can make in the face of the restriction the system will create. This will actually be a plottable curve, as flow will vary with pressure. A pump will also have a max pressure rating, above which point the integrity of the pump is in jeopardy.

Meaning, take a pump rated at 40 GPH @ 10 PSI, run it at free flow into a bucket, and it could conceivably flow more than 40 GPH. However, it might only flow 20GPH in a system with a higher restriction. Fuel pumps aren't used solely for free flow, so the sellers should put a pressure rating to it also. Sometimes you can find the flow vs pressure curves for these pumps, but that's more of an exception than the rule. Usually we get lucky and find a pump that specs more flow than we require at the system pressure we intend to have -- and we buy a pump based on that one point of the curve.

So, looking at Summit's webpage for the original pump in question:
It lists that pump to have a freeflow of 100GPH and a max rating of 8 PSI. It really doesn't give us the info we need. At 8psi that thing might only flow 30 GPH... What we can infer from that listing is that the 8PSI max means it is intended for a carbureted application.

The MSD pump that was already mentioned has a curve on the MSD website. I have used that pump in a water injection system and have had no problems (although it has low hours on it).
http://www.msdignition.com/fuel_7.htm

great info.

When i saw that 8psi rating, i figured it was for a carb.

I think i'm just gonna go with the MSD pump. The price is in my budget. I have already spent TOOO MUCH ON THE JEEP