Fuel Accumulator......

[Jim Nilsen]

I have been getting ready to put my accusump in for my oil system and jus t got done fixing my fuel problem for the most part and had the question come to mind as to why not have a fuel accumulator?

With the parts they have for the oil system you could do prctically the same thing with a few checkvalves and and the accumulator. I figure with the fuel pressures our pumps put out it would be easy to accumulate at least a quart or more of fuel under the higher pressure and when the pump loses pressure the acumulator would take up the slack until the pump came back up to pressure. the tech has been around for a long time and the need is finally here with the cars we have.

What do you think?

[Vegas69]

I don't think it's a bad idea even though it's just a band aid. I'd rather spend the money on fixing the baffling my self.

[GetMore]

The (possible) problem is that now you have high pressure fuel contained somewhere that can spray out at the wrong time. A surge tank is a better idea, mostly because it doesn't hold any pressure. Yes, it involves another pump, more wiring, and more hose and fittings, but technically it is safer.
BTW, you would run a low pressure, but high volume pump at the tank, and those are usually self-priming, so they are less sensitive to being run dry.

What I'd like to see is one of the things OEMs are using, but not much info is out there about. As I understand it, for fuel tanks that have some kind of obstruction in the middle they will use a venturi "pump". It takes high pressure fuel bled off from somewhere, and shoots it into a tapered nozzle that is submerged in fuel. The taper is wider on the pickup end, and narrower at the end that leads into the tube toward the other half of the tank that has the fuel pump. That high pressure fuel pulls the other fuel into the tube with it, so you will get more fuel running up the tube than you supplied to the venturi. If you install one of these in each rear corner of the tank and have a little baffling near the pump you should never have to worry about fuel starvation on the track.

[CarlC]

The problem with an accumulator is that the output fuel pressure would not be linear. Engines need a constant fuel pressure to operate correctly.

Jason, those are usually referred to as fuel modules. All of them have a venturi pump and an equalization valve, even those with no obstructions. The venturi pump is needed to keep the module full even when the fuel level in the tank is very low. This is critical for long pump life since the fuel is what cools the pump.

Applications like C6 and late model CTS-V have secondary tanks in which the module uses a venturi pump to draw fuel from them.

[Jim Nilsen]

I was thinking the same about the pressure differential being a problem too ,but if you put the accumulator on the front side of the regulator you would have as much as 60 psi and the regulator down at 45 leaving you 15 psi to work with in the process of the timing of events. most fuel starvation problems in a corner don't last only seconds.

I really don't know the cost of the new setups like they use on the Vettes and the Cadillacs but I have heard it is expensive, how expensive is yet to be determined by most of us. Mark Stielow is the only one I know of who would know that cost.

As far as it being a band aid is up for debate since any system that solves the problem and is reliable would be much more rated as a solid fix instead of a band aid.

Most of all it is just a thought up for debate and research and as far as cost it may be as expensive or more yet it could be less?

I do know that the fix I just did to my system held up in the corners with less than 1/8 of a tank of fuel. The corners were not as long as the turns at Road America like the carousel but it did work like I wanted it to. I now know if I have more than 1/2 of a tank of fuel I should have absolutely no problems but we will see when the real corners happen.

It is interesting to hear the opinions and the experiences that make the problem go away and we all need to make this problem go away. Right now it seems that there are still a lot of problems with the systems we have and for a company to come out with a solution like accusump did for oiling problems would make it so people can depend on a system and know the cost up front. With the cost of a good fuel cell or modified stock tank or what ever you choose being so expensive it makes it hard on a guy with a budget to plan. The accumulator would in effect be an add on like the Accusump possibly making it less costly and less fabrication for some. In the long run for the weekend autoxer or track day guy a bandaid is all they really need.

So lets keep the debate going until we can have a solution we can all count on when we spend the $$$$$$

[CarlC]

Won't work. If the regulator is set at 45psi then the pump is never pushing more than that. Hence, the accumulator will only get to 45psi. This means that fuel pressure will only go down from there.

Several aftermarket EFI systems will only accommodate +/-10% fueling changes from the table values even in closed loop. That's a fine line to live with, and then throw in fuel pressure fluctuations, and your pistons might not be too happy.

Carburetors with mechanical engine pumps are easier in that there is a reserve built in. The line from the tank to the pump acts as a reserve, plus the volume of the bowls. I never had a problem at the track with carburetors. EFI is another story.

What corner pickups did you use?

Todd,

How much HP is your engine making, and what fuel tank/cell do you have?

[Vegas69]

Hey Carl,
My engine makes 666hp and it's just a Ricks carb tank. I can get away with murder compared to you guys. :1st:

[CarlC]

How nice. The number of the beast!

[Vegas69]

She's a beast alright....:)
https://static1.pt-content.com/images/pt/2010/05/ZL1DynoGraph_0001-1.jpg

[jeff s]

For Ultima GTR and CanAm track cars we use a low pressure fuel pump to a reservoir. Then the high pressure pump pulls from the reservoir. It never starves for fuel until completely empty. baffles in the tank dont cure it completely. Even Corvettes starve during hard cornering when you get down to 3/8 tank or so.

[John Wright]

She's a beast alright....:)

I love how flat the TQ curve(or lack of curve) is.....a stump puller from 3500 on up and it hardly falls off at all. That should be a killer pulling up out of the corners.

[Vegas69]

Thanks, I ran the road race at RTTC in 3rd gear. Never shifted! I just found that it wasn't needed and brought on excess tire spin. Those 50 to 110mph pulls were a blast. :yum:

[Jim Nilsen]

Thanks, I ran the road race at RTTC in 3rd gear. Never shifted! I just found that it wasn't needed and brought on excess tire spin. Those 50 to 110mph pulls were a blast. :yum:

I too was in 3rd gear at Road America most of the time and it drove the instructor crazy, I made it into 4th gear when I got comfortable but the car just pulled better in 3rd and other than the big main straight away 100 mph was more than enough for my brakes to keep up with. The faster you go the harder it is to stop for some ungodly reason,LOL.

When the instructor drove he found out why. The range of speed in 3rd was something he hadn't encountered and when it was all done he wished he had a car with gear ratios like mine. If the car had been sorted out better 3rd and 4th would be all you needed, he wanted me to go to 5th several times but didn't realize that 5th would take him to 150mph + and there is no room for that with only 350 to 400 hp.

Another thing that made me laugh is that he told me it wasn't a drag race and I should ease into the throttle instead of putting it to the floor. I guess he never heard that a road race is just a drag race from one corner to the other,LOL. Maybe if you enough power to spin the tires in any gear you rol into it but when you only have 350 hp you need to put it to the floor as asap to keep up or stay out of the way. It is easy to become a road block when you don't have as much power as everyone else no matter how good you take the corners.

[Jim Nilsen]

Won't work. If the regulator is set at 45psi then the pump is never pushing more than that. Hence, the accumulator will only get to 45psi. This means that fuel pressure will only go down from there.

Several aftermarket EFI systems will only accommodate +/-10% fueling changes from the table values even in closed loop. That's a fine line to live with, and then throw in fuel pressure fluctuations, and your pistons might not be too happy.

Carburetors with mechanical engine pumps are easier in that there is a reserve built in. The line from the tank to the pump acts as a reserve, plus the volume of the bowls. I never had a problem at the track with carburetors. EFI is another story.

What corner pickups did you use?

Todd,

How much HP is your engine making, and what fuel tank/cell do you have?


It all depends on what side the regulator is on to the accumulator.
From my experience with accumulators you always have a higher pressure pump and the accumulator is always at a higher pressure than the down side of the regulator, especially if it was a bypass regultor to keep the volume up. The accumulators I have worked with were fed by air pumps and they tend to pulse so bad that with out the accumulators you would not have a consistent pressure to the regulator. With an electric or hydraulic pump the pressure is more consistent we usually didn't need an accumulator. The accumulator would still work the same and when you needed to go from one tank or batch to another while filling you would have the accumulator to make sure you didn't have any fluctuations in the fill line.

The big drawback to an accumulator is space and weight.

The good thing about this whole thread is that it is bringing more out about fuel systems in general that still needs to be discussed.

I like the sound of the low pressure pump from a big tank to feed the small one like Jeff uses in the Ultimas. We just need to get a list of parts and prices to make it easier to do without a lot of guesswork and research. Tanks that are simple are not as costly as baffled tanks and I have enough room for two tanks of the right propotion and then the other side of all this is for someone to make a divided tank, not baffled but divided to make strapping then in a lot easier.

For now I am happy to just be able to go below half a tank of fuel and not run out. Having to drive into a town to fill up before every time out on the track is a pain.

For those that want to know, my tank is a circle track cell and had the pickup in the right rear and when you go to a track with mostly right hand turns you really have problems. I had totally forgot that my pickup tube was there after 10 years of waiting to get my car on the road, the pickup tube went in at the front right hand corner. Yea I know it was a dumb mistake but it is much better now and we will see how good at Gingerman.

I think we can all safely say that the accumulator is not going to be the way to go but I wanted to hear others thoughts since it makes us think and from that other problems and solutions come.