chris-m

took my ls1 kit car to the dyno today (hub pack). car made 404bhp and 390ft/lb at the hubs which i was pleased about, but i also hit a few snags.

the fuel pump or regulator started playing up later on, and we were seeing less than 6psi at the carb bowl on a full throttle run. the fuel system is an aeromotive billet alloy pump/filter and reg, supposedly good for almost double my power, so i need to see what went worng this weekend with a strip down.

also i have an Edelbrock/msd ignition unit, the basic one with 6 timing pills. with anything other than pill no 1 we were getting det, so the 404bhp was made with the most basic pill no1.

engine is a stock ls1 bottom end and heads with a 220/220 cam (very tame lift). demon 750 carb, gm performance inlet, 3" exhausts.

i think the car should make more power with proper timing advance so is it worth junking the 6 pill version for the fully programmable version? we tried Uk 95 octane fuel (detonation and 370bhp @ hubs) and then 98 octane shell optimax. (no det, 404bhp)
I was led to believe on the msd forums that the msd box should cope with UK 95 octane fuel ok, but obviously not, as anything other than timing pill 1 resulted in lots of det.

AFR was around 13.6:1 wot, so could do with being a little richer yet, but ran out of dyno time, so another trip required. engine survived ok and made a nice smooth power plot at least!

anyone any thoughts on this ignition/det problem with the basic msd unit?

Skele4door

iTrader: (1)

Did you check the fuel filter to make sure it isn't clogged? Even though you started with all new components there might have been some junk in them.

chris-m

thats tomorrows plan i reckon, fuel filter and hoses off to check no crap got through. i made all the hoses up myself with braided and fittings etc, and blew them out with comp air before fitting them, but something may be in there.

someone suggested the float needles may be too small/restricted?
float bowls start at top line on glass, by 6k revs its at the lowest line and a lot of foamy fuel visible. should the bowls drop that much? fuel gauge was shoing 6psi at all times tho, but float level dropped during run.

Shawn MacAnanny

iTrader: (12)

So you dynoed the engine out of the car? Or it was in the car through the drivetrain? The 750 carb is too big from everything i've read and been told. Even with a set of ported heads i'm still being told only run a 650 carb that 750 is over kill for this engine.

What fuel pump are you running? I know i had around a 50gph fuel pump for my 780 carb and it wouldnt keep up. I swapped out for a holley 97gph for this engine. What size lines and such? After checking the fuel filter unthread your fittings going into the fuel pump. If you're using a holly they have a screen right on the inlet side of the pump to stop any debris from the lines.

You shouldnt be getting detonation with that setup. I am going with the MSD setup with a 3 bar MAP sensor so i can program my own timing curve. I'm also running two widebands, one in each header so i can tune and diagnose cylinder bank problems.

chris-m

hi there
the engine is in the car, the dyno is a hub pack type that bolts to the rear wheel hubs and takes direct power readings there, rather than getting wheelspin issues etc. 401bhp @ hubs and the operator estimated maybe 440bhp flywheel, so its not doing too bad on a mild cam and timing pill no1.

the fuel system was over-specified (i hoped) to cope, ie Aeromotive A1000 pump (300+gph), -10 from tank to billet filter, -8 from pump to regulator (aeromotive) and 2 x -6 hoses out to the float bowls.
the pump has a direct -8 outlet to the tank return, which i had to reduce down at the tank end to a -6 fitting. i checked the filter and drained the tank yesterday, all ok, filter was clean. no other filters i know of in the system, and its a barry grant demon 750cfm carb. the fuel system should be good, i did however suspect the pump wasnt sounding great for some reason, the note it makes changes in pitch. also i took the regulator to bits and think that may have been the fault, as it was sticking. all the parts are brand new tho!.

i'm going to get the pump looked at just in case and get a new regulator and then refit it all, now i know the lines and filter are good.

the det issue is related to the msd unit and our uk fuel, it looks like the uk95 octane isnt as good as your pump gas for det control. i may have to invest in the proper fully mappable MSD ignition box also, as the carb guy has had this same det problem before on a uk car with the msd 6 pill timing box, even on the lowest setting no1 it detted.

the fuelling was still lean (13.6 to 13.8:1) afr, which wouldnt have heped i guess with the bit of det. the carb guy has a lot of experience tuning v8s on carbs, and said the 750cfm would be ideal if jetted right, he just couldnt get it rich despite jumping loads of jet sizes up, indicating a fuelling issue.

any more ideas anyone?

chris-m

also to add, we watched the main float bowl on WOT and its dropping from the top line in the sight glass to the bottom line by the time it hits 6000rpm. i pointed this out as it also looked like the fuel was bubbling/foaming in the sight glass as it hit high revs.
is this normal, or should the fuel level in the bowl stay near the start position a bit more?

forcd ind

iTrader: (7)

the first thing i would ck is the voltage to the pump-depending on where your pump/battery is located, and the alternator wire size, you could have insuf. voltage to the pump-aeromotive recms. a #10 from the tank to the pump, #8 return-the fact that you have control over the fuel press at idle, i dont think your return is restricted-the foaming could be too much heat in the carb, but usually on a return system not a problem-their are bottom feeding needle and seats that i use on the procharged motors that are sup. to help prevent some foaming-i have made over 700 RWHP with an a1000 pump, so one working properly should do it-B/G carbs have been known to take some riching up-your AFR'S dont seem to be too far off though

Old Geezer

iTrader: (3)

"the pump has a direct -8 outlet to the tank return". Can you explain how this is plumbed?
Also, does the tank have sufficient venting?
The foaming fuel, the noisey pump, all indicate to me that the pump is cavitating.
Filtering should a 2 point process.
1 w/ at least a 40 micron before the pump, and a 10 micron after. Is this the way it's set up?
Use of a 10 micron before the pump can/will cause cavitation.

chris-m

ok cheers for this, some more bits to think about now. I can check the voltage at the pump easily enough. its wired off its own 25A rated supply and i believe the pump draws 9amps if i remember. its something to check tho, altho i have heard people moan about the noise of those pumps anyway.

the fuel pump body has its own return outlet machined into it, with a -8 AN outlet to -8 hose, from there direct to the top of the tank return inlet. i had to adapt down to a -6 at that end as the tank outlet was slightly smaller than the pump return, but again i've been told a -6 would suffice anyway, so its a slight restriction only at the tank fitting really. the pump is sat 12" from the tank anyway so the return is very short.

i already checked the tank vent which is directly beneath the filler cap, and is approx 1/4" diameter and open to atmosphere.

i will check the size of the mesh fuel filter, again its a big billet alloy Aeromotive one with a stainless cleanable internal filter. i took that out and it was clean as a whistle. i've had all the hoses off and blew them thro, no probs there, and the tank outlet isnt blocked feeding the pump.

my only thought at the minute is the fuel regulator isnt upto the job, its a billet aeromotive type with -8 in and -6 out x 2, that or the pump is faulty and not making enough flow.

should i not be getting any foaming in the primary bowl at all, or is some expected ? it builds up above 4k revs and by 6k revs the sight glass is about obscured by foaming fuel.? the level has by then dropped from the top line to the bottom line and is just visible among the foamy fuel.

if i knew that shouldnt ever happen it would point to the pump or regulator not allowing enough flow thro at peak revs. if i should see continuous fuel in the sight glass and no foam it would make sense i suppose?

Old Geezer

iTrader: (3)

"the fuel pump body has its own return outlet machined into it, with a -8 AN outlet to -8 hose, from there direct to the top of the tank return inlet. i had to adapt down to a -6 at that end as the tank outlet was slightly smaller than the pump return, but again i've been told a -6 would suffice anyway, so its a slight restriction only at the tank fitting really."

?? Is the regulator at the engine??
If so, the open return located to the pump, will just dump flow back into the tank.
Dumping that much fuel right back next to the pickup can/will result in foaming, and overheated fuel being delivered to the engine.
How about a drawing, showing how this is plumbed??

chris-m

not got a drawing but might have a picture that shows it. its a mid engined rwd kit car, so the ls1 is right up against the bulkhead behind me, with the tank buried in below my back and the engine itself. the pump is at floor level, and the return at the top of the tank, but aeration is something i hadnt considered. the car is based on an ls engine tho and they have an efi ls7 running 600+bhp so i suspect the tank/plumbing arrangements should be ok. not many of them have been done on ls and carb tho, so i'm on my own to some extent. the tank is internally baffled with foam (i already checked its not blocking the outlet and return tho).


the regulator is mounted on the bulkhead higher up than the return level, and is only 12-15" from the float bowls so the pipe work is short. no return from the regulator as its direct return at the pump body. pump churns out 22-25psi max and the reg was set at 6psi. the guy i bought the pump/reg/filter from was confident it would support 600bhp easy, maybe more, so i shouldnt have any problems in theory. :-(


whats your thoughts on this sight glass issue? should i expect it to drop on a wot dyno run from top level to lowest, with some foaming visible? i'm not experienced with carbd v8s at all tbh.

Old Geezer

iTrader: (3)

"no return from the regulator as its direct return at the pump body. pump churns out 22-25psi max and the reg was set at 6psi."

So if I understand this:You are under the impression that the pump has a relief in it, and it's set at 22-25psi? The A1000 does not have an internal relief in it. It requires an external regulator.pt# 13204, for carbs, and has a return line port on the bottom.http://www.aeromotiveinc.com/product...sub=2&prod=165
Should the pump be plumbed w/ a return line B4 the regulator, the fuel would go thru the return line, and back into the tank. The carb would starve.
If the system is working correctly, the fuel should not be full of foam, nor should the float levels drop.
If it were my setup, I'd run the return line from the regulator, and plug that line from the pump. As it is now, all you have, is a massive fuel leak, that the pump cannot overcome.
But, that's just my $.02..

chris-m

hi again. i misread the pump info actually, its very similar to the A1000, but its a carb specific Aeromotive one, which is set up to give 17-25psi out of the pump to the external carb regulator, and the pump has an inbuilt relief spring return port that directs excess fuel back to tank once the float bowls etc are full. its the same size pump body as the A1000 and flows 350gph, so obviously should do the job. the carb regulator is a 3 port, ie one -8 in and 2x -6 out and again rated at good for 600+bhp supposedly (if it works right). we had that set to give 6.5psi to the float bowls, but the foaming/level dropping was noticed in the primary bowl.

sounds like i shouldnt have seen any level drop at all, and therefore the problem must be at the pump or external regulator.

Old Geezer

iTrader: (3)

OK. A new "ball game"..
There are 2 pumps: the S/S[11203] and the H/O [11029]
The 09 is internally set to put out 7psi, so I have to assume you have the H/O, with the higher op pressure.
There are 2 regs: 13201, and 13205. 1 has a return, the other none.
The H/O pump will run without a reg.
Since you have a seperate reg, I'd guess you have the S/S pump.
Bottom line:
The pump is messed up, the internal regulator is messed up, the pump pickup is located such that you are picking up return fuel, and pumping bubbles..
I'd start w/ deadheading the pump outlet to a gauge,[AFTER the return line] and see if you really have the pressure you say the pump is capable of producing. I'd adapt the gauge to the feed line, just before the regulator.

chris-m

i have the pump which puts out 17-25psi at the pump body, and a regulator with no return, so i hope that makes sense? the carb reg was set to 6-7psi, and the pump is kicking out about 20psi.
however the fuel return is direct above the tank outlet, altho at a gap of approx 15" higher up the tank. i think this could indeed draw bubbles back into the pump should the tank level be low as the fuel drops back in from the return. however, this tank design is used on all the kit cars from my manufacturer and works on on them (most are efi tho but have return to same spot).
i wonder if the pump itself is playing up as you suggest. i'll get a pair of fuel gauges hooked up, one to the pump outlet looking for 20psi and one at the carb regulator looking for 6psi.
the cheap gauge i got with the regulator is useless, not very accurate at all, we had to use the dyno guys autometer gauge with a remote line hooked up to get an accurate reading at the reg.

chris-m

double checked in the tank tonight, the return is about 18" above the outlet and not direct in line, its about an inch or two to the side, the tank is also baffled with foam inside it well below the return, so that should help prevent the fuel splashing directly ontop of the outlet. i made sure no foam was stopping the return or outlet flow tho.

still looking like pump and/or regulator so sending em back to supplier for test/checking.