Ideal surge tank design for DSM road racing

[Ludachris]

If we could have a surge tank designed for our cars, what would be the ideal dimensions, specs, mounting points, etc? I would imagine for weight distribution we'd want it mounted in the rear next to the stock tank.

I ask because we have a couple vendors who could create one for us if we can just come up with the ideal specs. Let's discuss this.

 

[turbosax2]

Here are some good links.

Surge Tank Location, Installation and Design [Archive] - RX7Club.com
Tech Page
http://us1.webpublications.com.au/static/images/articles/i15/1576_2mg.jpg
FC3S Pro v2.0:# Mods - Fuel Surge Tank System




Mounting points and exact dimensions will of course depend on the car, but here are some basic design points.


Made of aluminum
Roughly 1/4 gallon capacity
Tank much taller than is wide to allow any trapped air to rise to the top so it does not enter the high pressure pump (either use 2.5" or 3" tubing to make surge tank)
3 bungs near top of surge tank
-1 for feed from stock tank (bung preferably welded at angle to reduce air mixed with fuel, like this)
-1 for overflow return to stock tank
-1 for return from fuel rail (bung preferably welded at angle to reduce air mixed with fuel, like this)
1 (or 2 for dual pumps) bung on bottom of tank to high pressure pump(s)
All bungs -10an so user can pick what fittings to use to match their size line without necking down

 

[tsiboosted]

I did a little searching and came up with these 2 designs. The first one is similar to the one Eric posted in that it is cylinder in shape. It is roughly 11" tall and 4" in diameter and can hold right around 1/2 gallon of fuel.

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And I found another one that holds roughly the same amount of fuel but is a box design. Measuring 5.5"T, 5"W, 5"L. It comes with some fittings.

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[cioc]

I personally like the round design the best, making sure the feed line from the main tank enters at an angle to create a "swirling" effect. Putting something in the rear right side of the car would be the best for balancing. What would be really cool is to be able to swap my in tank Walbro for the stocker and somehow mount the Walbro in the surge tank...unless there is a way to use the Walbro externally. I'm thinking a little bigger than a quarter of a gallon would be needed but I can be persuaded.

 

[tsiboosted]

I personally like the round design the best, making sure the feed line from the main tank enters at an angle to create a "swirling" effect. Putting something in the rear right side of the car would be the best for balancing. What would be really cool is to be able to swap my in tank Walbro for the stocker and somehow mount the Walbro in the surge tank...unless there is a way to use the Walbro externally. I'm thinking a little bigger than a quarter of a gallon would be needed but I can be persuaded.

Yeah, I agree with you on the round design as well. Just throwing some other ideas I saw out there on the table. The ones I found seem to hold right around 1/2 a gallon of fuel. So that would be good enough I think.

 

[turbosax2]

I'm thinking a little bigger than a quarter of a gallon would be needed but I can be persuaded.

One of the links I posted did the math. I didn't really look it over or do the math for a dsm scenario, but here it is.

(1 liter = about .25 gallons)

You need to figure out how much fuel you're be using "worse case", and then back out the capacity of the surge tank from the differential flow between the two fuel pumps.

It's sounds harder than it really is - it's just tedious math.

This is just a rough calculation and example...

Popular 550 + 1600 fuel injector combo...
Datalog the pulsewidth at WOT, and this will give you "worse case" fuel consumption.
Just as an example, we'll go 70%...
Approximate fuel flow - 1100 + 3200 = 4300 cc / min x 70% = ~3000 cc / min or about 3 liters per minute.

Walbro 255lph in stock gas tank + Aeromotive A1000:
Walbro ~250lph @ 10psi (should flow slightly more)
A1000 ~300lph @ 45psi (slightly underrated)
So we have a differential of about 50lph or ~ one liter per minute.
Thus, if the A1000 is flowing all of it's fuel into the engine, worse case, the surge tank should drop at a rate of 1 liter per minute.
The Walbro is flowing about 4 liters per minute.

In this case, if at 70% pulsewidth, the surge tank will never empty, cause the Walbro outflows the max fuel going into the engine - 4lpm versus 3lpm.

Now, say the engine requirements are bumped to 5 liters per minute...
We now have a differential of 1 liter per minute between the engine fuel requirements versus the Walbro capacity...
Thus, if the surge tank is approximately 2 liters, this will empty out in about 2 minutes.
Now, 2 minutes of WOT is a LONG time!
Unless you're doing Bonneville LSR runs, this much capcity is more than enough for most road race tracks, where WOT runs are typically 10 to 30 seconds max.

 

[hatch]

I found this Turbo XS surge tank:

Turbo XS Fuel Surge Tank - Group 5 Motorsport - A premier automotive performance store in San Diego

Looks like its setup for dual pumps.



Edit:
Here is a AMS kit for the EVO that includes a fuel pump, fittings, and hoses.

AMS Fuel Surge Tank System Mitsubishi EVO VII VIII IX 01-07 Vivid Racing

 

[Ludachris]

Question guys, would a surge tank have to use an external pump? It seems to me if we could make one work with a factory pump it would be a lot more cost effective.

 

[360glitch]

I'm glad to see that you guys are working together for a solution to this problem. I am currently building up a TSi for autox and was notified about this issue yesterday. I look forward to seeing what you guys can come up with. I'd give you input if I could but after looking at what you guys have been discussing I'm not sure how much help I could be. :S

If any of you experienced track guys want to give me some advice check out my thread here:

http://www.dsmtuners.com/forums/newbie-forum/311003-1g-turbo-awd-autocross-build-up.html

 

[turbosax2]

Question guys, would a surge tank have to use an external pump? It seems to me if we could make one work with a factory pump it would be a lot more cost effective.

You can still use the stock pump in the stock tank since it is essentially operating at 0 pressure. I guess you could mount an internal pump to the top of the surge tank but that would make the surge tank more complicated to make and it would have to be large enough to fit the pump and filter in. A stock pump couldn't be used in the surge tank just because it doesn't flow enough for most people. An external Walbro 255hp flows more and costs only a little more than the internal pumps, so it doesn't make sense not to go external. Plus, if you ever need to switch to a bigger external pump the swap would be extremely easy.

 

[Ludachris]

You can still use the stock pump in the stock tank since it is essentially operating at 0 pressure. I guess you could mount an internal pump to the top of the surge tank but that would make the surge tank more complicated to make and it would have to be large enough to fit the pump and filter in. A stock pump couldn't be used in the surge tank just because it doesn't flow enough for most people. An external Walbro 255hp flows more and costs only a little more than the internal pumps, so it doesn't make sense not to go external. Plus, if you ever need to switch to a bigger external pump the swap would be extremely easy.

Good points Eric. Makes sense.

 

[Ludachris]

I think maybe if we can come up with a good mounting location and decide on the dimensions, we can probably start talking with some vendors about it.

 

[turbosax2]

You could place the surge tank somewhere in the engine bay. This way you could probably keep the factory fuel lines to and from the stock tank. This wouldn't be as ideal for weight, but we're not talking about too much weight between the tank, fuel, and pump. I'm personally not a fan of this idea for several reasons but it would be the most cost efficient. I would prefer it next to the stock tank, like you said, and replumb the whole system with SS braided line.

http://www.dsmtuners.com/forums/bolt-tech/283820-surge-tank.html

 

[Ludachris]

I think if we're doing this for road racing we need to try and design it so that it sits near the tank, not in the engine bay. There's no point in adding additional weight to the front end of the car, however little it may be. And everyone's engine bay is going to be different, so it would be difficult to find a common mounting point for most cars. Though I can see the AWD/FWD and 1G/2G differences in the rear causing some issues in trying to find a common mounting point in the rear.

 

[Ludachris]

I just peeked under the car and it looks like there's plenty of space between the tank and the rear-end support bracket. There's one possibility.

 

[hatch]

How much space is there behind the rear bumper support?

 

[Ludachris]

How much space is there behind the rear bumper support?

Way too dangerous in a rear impact collision.

 

[tsiboosted]

I just peeked under the car and it looks like there's plenty of space between the tank and the rear-end support bracket. There's one possibility.

I dont know if you would want it under the car would you? Too easy for something to hit a line and rip it off etc. Most of the surge tanks I have ever seen, were mounted somwhere inside the car. Now obviously there will be different mouting places as each persons interior will differ.

I saw a circle track racer make a bracket and have it mounted in the rear portion of what would be the interior there near the backseats. It was mounted to the bracket which was mounted to the floor and the surge tank set up about 5 inches or so off the floor of the car.

 

[Ludachris]

I dont know if you would want it under the car would you? Too easy for something to hit a line and rip it off etc. Most of the surge tanks I have ever seen, were mounted somwhere inside the car. Now obviously there will be different mouting places as each persons interior will differ.

I saw a circle track racer make a bracket and have it mounted in the rear portion of what would be the interior there near the backseats. It was mounted to the bracket which was mounted to the floor and the surge tank set up about 5 inches or so off the floor of the car.

I'm not sure if that would be considered legal for NASA or SCCA. That's my only concern. Since our fuel lines run under the car already, it can't be much more dangerous to mount a surge tank under there as long as it's tucked pretty well.

 

[tsiboosted]

I'm not sure if that would be considered legal for NASA or SCCA. That's my only concern. Since our fuel lines run under the car already, it can't be much more dangerous to mount a surge tank under there as long as it's tucked pretty well.

Well I can understand that and see where you are coming from there Chris. The only reason I was thinking that is (of topic a bit) but a fuel cell is inside the car with fuel lines inside the car and they are NASA & SCCA legal. I have also seen pics of surge tanks under the hood. Different locations for different cars obviously. But if we/anyone could come up with a "good" location for one, that is when we could get the dimensions we need to have someone make one.

If we ended up mounting the tank under the hood. Could almost fabricate a bracket as well to maybe mount it to the fire wall.

Here is one I found mounted underneath the car as Chris was eluding to.

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And anohter one that was fitted to go around the spare tire in a car. Dont see why we as DSMs couldnt almost make one like this perhaps and put it where the spare tire use to be. Im just trying to throw different ideas out there is all here.

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[hatch]

As far as under the hood I was thinking where the charcoal canister is normally located. I know that everyone doesn't have theirs removed but that may be a good under the hood location.

 

[Phil1320]

Every swirl pot install I've seen has placed them inside the cabin at the rear. But, for those of us that still run stock tank and in tank pump it would make sense to mount it somewhere near the tank in the undercarriage for sure.

Phil

 

[cioc]

So, I spent some time under the car today and started brainstorming about possible locations for a surge tank. I came up with three options. One being above the muffler, next to the gas tank.(Least favorite option due to heat from muffler preheating the fuel...does anyone else think the muffler gives off enough heat to do this?.)
<a href="http://s116.photobucket.com/albums/o39/cioc/?action=view&current=IMG_7255.jpg" target="_blank"><img src="http://i116.photobucket.com/albums/o39/cioc/IMG_7255.jpg" border="0" alt="Photobucket"></a>

The next was in between the unibody and the bumper.(In the picture to the left of the bumper absorber where the unibody dips down and then left.) This would allow for a large vertical tube style surge tank. The only drawback I see to this option is in the even of a rear end collision.
<a href="http://s116.photobucket.com/albums/o39/cioc/?action=view&current=IMG_7257.jpg" target="_blank"><img src="http://i116.photobucket.com/albums/o39/cioc/IMG_7257.jpg" border="0" alt="Photobucket"></a>

The last and my favorite option although not weight bias friendly is the location opposite the muffler. It seems as though there is a ton of room and plenty of areas to mount a simple bracket. The stock tank has a hole just aching for it.
<a href="http://s116.photobucket.com/albums/o39/cioc/?action=view&current=IMG_7256.jpg" target="_blank"><img src="http://i116.photobucket.com/albums/o39/cioc/IMG_7256.jpg" border="0" alt="Photobucket"></a>

 

[Ludachris]

In the latest Turbo mag I saw today, there was an installation article on the AMS surge tank kit for EVOs. Here's the product on their site:
Automoto Sports Copyright&copy AMS 2006

Seems to me that if we can find a standard mounting location (I prefer the third location pointed out by cioc above) that will work for most all DSMs, we can get one of our fabrication vendors to throw something together similar to what AMS has.

Here are some pics - looks like they mounted it in the same location on an Evo that I would like on a DSM:

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[cioc]

I REALLY like the shield on the AMS kit!