Fuel delivery under high acceleration

I took the Blazer out Sunday night to finally bed in the break pads.  My frist hard stop did quite the job clearing my fuel system and starving both the pump and motor.  This is quite frustrating since I replaced my stock system (when the pump went) with an external pump and fuel cell to help alleviate this problem.  At the time (and still) I couldn't find much useful information on setting up a fuel system (cell, pump, pickups, baffles, lines, etc).  I'm hoping somebody here has experience or can help develop some experience since we all want to be able to drive our trucks hard without having to worry about fuel getting to our motors.

Currently I have a summit "drag" tank with the rear sump and open cell foam.  My fuel pump is on the frame rail about in the middle of the truck.  I don't have any baffles in the tank and I just routed the fuel line as conveniant.  I'm not sure if the size of the line will make a big difference in delivering consistant fuel under hard braking or turning, but I'm running 1/2" line from my tank to the pump and stock line from there to the filter to the motor.

I'm going to start browsing around the next few days probably starting at protouring.com, but would appreciate input from others too.  I'm thinking I need to add some sort of fuel pickup in several places in the cell and may need to run a different cell design with baffles and open cell foam.  Also thinking it would be better to have the pump closer and below the tank level too.

How much fuel was in the cell?  The drag cell would be the first place I would look at.  The rear sump isn't all that condusive to decel or lateral movements.

Later, Doug

I know it was due to fuel slosh and that this design isn't conducive at all to acceleration other than forward.  I'm just not certain where to go from here.  There is very limited information that I have found on the internet.

This is the best discussion I have found so far.

http://www.pro-touring.com/forum/showthread.php?t=54716&page=3

And really points to one off designs being the best solution out there without dropping an extra large lump of money on a fuel safe cell.

ok, first things first.

how much fuel in the tank?
did thi happen first stop, or all stops?
return or returnless?
fuel pressure?

i know holley used to make a spider pickup for tanks. it eas efectively a multiple hose assembly with little pucks that acted as pickup and weight points, alsong with filter material. you may be able to do this in your cell. redrill the cell for a fitting with some material on the inside. run a hose from that to a couple of T fittings. run hoses to different sections of cell. install foam to weight the hoses down, as well as reduce slosh. see if that works. should be able tpo get the foam from RCI or ATI, and the hoses made at a hydraulic shop.

think of it kinda like the spider injector on the old CPI 4.3, only inreverse.

i know also that fuel level plays a role in this. on our 88 vette TT car, if we run less tham 1/4 tank, we suck the fuel system dry. on my s10 on track, i gotta run above 2/3rds.

you said that this is an ongoing problem with fuel starvation under braking. could it be that ypou have an intermittant electrical short under braking, causing loss of voltaege to fuel pump?

michael

There wasn't much fuel in the tank.  Maybe 3-4 gallons (about a quarter).
Only happened on the hard stop.  I drove it through the neighborhood to get to the road I started doing my bed in on.  No problems in "normal" driving.
Return from the motor
Don't have a gauge for the pressure, but from my experience in the past there was little to none at the pump after this happened.

I already have foam in the tank, so weighing down the pucks wouldn't be a problem.  Do you have a link to the holley system or discussion on it?  Wouldn't be too hard to hook something up to the second output on the back to set this up.  It is already a bulkhead fitting meaning there are threads on the insde too.  I Have read of filters that close up when they are dry.  That may be one way to avoid getting air in the pickups that have no fuel.

I checked the electrical connections when I got home, but was pretty sure that wasn't the problem.  The pump sounded like it does when it isn't pumping fuel.  I've got a lot of experience with that to say the least. 

i saw the product in a magazine years ago. more than i care to admit to.

i couldnt find it on the holley site, nor any reference in google. so it must have never cought on. ill keep looking, but im not feeling hopful.

how is the cell mounted? level at ride hight? or is it angled forward lsightly?

michale

FOUND IT!!!!!!!

http://www.who-sells-it.com/cy/holley-performance-products-inc-2055/fuel-pumps-9347/page-20-fullsize.html

It's not mounted very well and I think angled forward compared to the ground.  One of those projects you do more ignorantly and quickly than you'd like to admit. 

the mounting being "not very good" is kinda scary. you probably wanna fix that.

also, level is a necessity. the sump being at the rear of the tank is not perfect. if anything, you want the tank either level to the ground at ride attitude, or angled rearward a hair.

also, check the foam. some of the cheaper foams have been known to break up a little and clog the pickups.

have you checked out that link? i think that fixing your mounting and running a full tank will solve 99% of the problem. but that does not solve the low fuel slosh problem. also, there may not be enough foam in the tank. which would contribute to the issues.

on our race car i believe we have a 'cup' where the retun always flows into, and the 'cup' is where fuel is pumped from.

the mounting being "not very good" is kinda scary. you probably wanna fix that.

also, level is a necessity. the sump being at the rear of the tank is not perfect. if anything, you want the tank either level to the ground at ride attitude, or angled rearward a hair.

also, check the foam. some of the cheaper foams have been known to break up a little and clog the pickups.

have you checked out that link? i think that fixing your mounting and running a full tank will solve 99% of the problem. but that does not solve the low fuel slosh problem. also, there may not be enough foam in the tank. which would contribute to the issues.

It's not going to fall off, but if I were to do it again I'd do it much differently.  The fuel cell mounting/placement is one of the main factors that has driven me to do a full back half on my new frame.  That is why I'm exploring this now rather than when I'm half way through building it.

Foam had some intial breakup, but I haven't seen large quantities in the filter in 6 months.

I checked the link and think I will go with those pickups initially and design the frame to accept a larger cell if I decide to replace it in the future.  Putting one in each corner and pulling from the sump as well should provide plenty of fuel under any condition.  I also think I'll run a sump tank similar to what Ryo mentioned.  Sump tank will have a low pressure/high volume pump feeding from the main tank.  It will recieve the return from the fuel rail and will also have an overflow back to the main tank as well.  Capacity will be 1 or 2 gallons and being small fuel slosh won't effect it nearly as much.

Foam is shit, after a year or so you will go through filters non stop. Look up "fuel safe". You may get an idea for road racing baffles. I'm going to build doors on piano hinges for the Blazer tank going in my truck.

You could build a sump in the tank but I can't explain it. I can bust out the colored pencils if you like...

Foam is shit, after a year or so you will go through filters non stop. Look up "fuel safe". You may get an idea for road racing baffles. I'm going to build doors on piano hinges for the Blazer tank going in my truck.

You could build a sump in the tank but I can't explain it. I can bust out the colored pencils if you like...

I've looked at fuel safe before ($$$$), but can't find any information on how they baffle or design their tanks.  I'd build an in tank sump, but my cell is plastic.  Not exactly the most conducive to that.  A seperate sump tank would be easiest to add to my current setup financially and practically.  I've had the foam in the cell for two summers of driving now and it's only gotten better.  I'm crossing my fingers it stays that way, but I'll be in there this winter to check on it anyway.

To: The Wife. lol. I love your plates. Ive been doing stock car racing for a long time. we had a similar problem. what we did is, replaced all the foam in the tank but also formatted it so that the pick up was retained in a good spot for us. Which was the right rear of the cell. another thing i would consider is, hard cornering and braking most of the time doesn't usually mean hard accelleration at the same time, but, i think you should consider putting a baffle or a similar feul filter on the return line and keep fuel in the return line a little more restricted.   kinda the same as an FMU for low buck forced air builds.

To: The Wife. lol. I love your plates. Ive been doing stock car racing for a long time. we had a similar problem. what we did is, replaced all the foam in the tank but also formatted it so that the pick up was retained in a good spot for us. Which was the right rear of the cell. another thing i would consider is, hard cornering and braking most of the time doesn't usually mean hard accelleration at the same time, but, i think you should consider putting a baffle or a similar feul filter on the return line and keep fuel in the return line a little more restricted.   kinda the same as an FMU for low buck forced air builds.

haha thanks.  I've been tossing around some ideas for my long bed 1st gen, but haven't had any that stick currently.  Which reminds me I need to register both the trucks tonight.  Crud.

In essence blocking off the return would raise the fuel pressure right?  Or are we just trying to reduce the volume that passes to the return to increase the reserve?  What I'm imagining with the multiple pickups is similar to what you did with the stock car except I'm doing it in 4 places?  Good to get some input from someone with race experience too.

To: The Wife. lol. I love your plates. Ive been doing stock car racing for a long time. we had a similar problem. what we did is, replaced all the foam in the tank but also formatted it so that the pick up was retained in a good spot for us. Which was the right rear of the cell. another thing i would consider is, hard cornering and braking most of the time doesn't usually mean hard accelleration at the same time, but, i think you should consider putting a baffle or a similar feul filter on the return line and keep fuel in the return line a little more restricted.   kinda the same as an FMU for low buck forced air builds.

haha thanks.  I've been tossing around some ideas for my long bed 1st gen, but haven't had any that stick currently.  Which reminds me I need to register both the trucks tonight.  Crud.

In essence blocking off the return would raise the fuel pressure right?  Or are we just trying to reduce the volume that passes to the return to increase the reserve?  What I'm imagining with the multiple pickups is similar to what you did with the stock car except I'm doing it in 4 places?  Good to get some input from someone with race experience too.

Yeah an fmu is vacuum operated and works like a blow off or waist gate. when it senses less vacuum it closes the return line to the tank to keep all the fuel pressure in the rail. i was looking into an sts turbo set up and when i was researching what it would involve, i came across that little nuggett.

As an update:  I filled the tank up well and had no issues this time.  Was much lower than I thought...  Still want to figure out how to get the most out of the tank, but that was the problem this time.