diabolical1

iTrader: (3)

Hi All,

I need input on surge tank design. I have a few questions, but given my tendency to be long-winded, I'll break them up into different posts.

Bascially, I'm trying to build one for an FB that I'm working on. So far, I've test-fitted my first design (basically my regurgitation of 99% of the one's I've seen) - a 12-inch cylindrical tank with 3-inch inner diameter. My calculations give me roughly 1390 cc. More than enough for my needs!

The problem is I can't find a place where it will physically fit under the car with the pump in place - despite the fact that I've seen pictures of those types of surge tanks under FBs on the forum. It's not working for me. It still hangs too low for my comfort - an imminent disaster!

My solution is to mount it in the driver's storage bin, which it's still too big for, so here I am designing something else from scratch.

First question: what are the limits for surge tanks? I'd imagine that there is such a thing as too small and too big. I've noticed that none of the ready-made ones I've found are less than 1000 cc - many are 1300 to 1600. I'm more interested in minimum. I'd prefer a minimum volume that would safely feed 400 HP - even though the plan right now is 200-220 with the current setup. I'm fairly sure at some point the owner will want forced induction and I'll be the one to set that up, too.

diabolical1

iTrader: (3)

Okay, next question is regarding shape. I know they're usually cylindrical because it combats sloshing by creating swirl instead - at least that's what I took from the limited reading I found.

I also know that there are some non-cylindrical ones out there on the market - Racer Parts Wholesale sells one for example. So question number 2 is how important is the shape?

I sketched 3 designs during the day today and the one that appeals most to me affords me the option of softening the 90º corners if I cut a tube in quarters and use them in the corners of the sqaure - a little less volume, but less sloshing.

diabolical1

iTrader: (3)

I was reading a few threads and came across one where trochoid mentioned specific measurements between where the return line from the engine had to be with relation to the supply line at the bottom. My third question is simply if someone can explain or elaborate on anything regarding specific placements of the line fittings.

I know that the supply to the engine needs to be at the bottom and pointed to the rear of the car. I also know a bowl shape is better than a flat shape for this. I figure the return line to the tank should be as far to the top as possible to insure than full volume is always available to the high pressure side (the bottom). From what I can see, the return line from the engine can be placed anywhere as long as it's at or near the top.

diabolical1

iTrader: (3)

My fourth issue kind of goes back to the volume-thing. It's not a question per se, I'm interested in the minimum needed volume for 2 reasons and I just want to get input on whether or not my reasoning is sound.

The first reason is obvious. It's the reason why I find myself in this situation. Space. I'd like to maximize it because after all, this car is not being built for track use (maybe occasional runs), it's a street car. I figured he should be able to use as much of the interior space as he can and not have to worry about mechanical **** using all of it. The passenger-side will remain somewhat functional because I mounted the EMS there - long as he keeps electromagnetic sources away, he can use as Mazda intended it ... for storage. My point is I'm trying to make it as small as I can.

The second reason is what I really want to hear technical opinions on. I figure the smaller I make, the more it will stay full and due to the shape (if I don't soften the edges) sloshing shouldn't be a problem.

diabolical1

iTrader: (3)

Finally, this is just requesting a free-for-all for those of you that use surge tanks or have modified the stock gas tank. From everything I've read, it seems deisgning a fuel system with a surge tank is better than one based on a modified stock tank.

If my surge tank ideas turn to ****, I'm planning to go the modified tank route. I just want to hear the drawbacks as to why it is inferior. If it's built with baffles and perhaps one of those weld-on sumps, then I don't see how it's inferior to a surge tank. All in all it may be more expensive, but I think it would be much simpler. I just want to be enlightened. So anyone with an opinion, feel free to share.

Then there's even yet another option. Combining both schools of thought. Elwood designed an awesome in-tank surge setup that I'll shamelessly say right now I may try to replicate when it comes time for doing my own FB. It really is worth a look for those interested in such things. Kudos to Elwood.

Thanks.


EDIT: wouldn't you know it. Not even an hour since I started writing this and I've found surge tanks with as little as a quart as total capacity. Probably not enough for any of our needs, but I just wanted to correct my earlier statement when I said a liter was the smallest I've found. Cheerio!

diabolical1

iTrader: (3)

okay ... yes, i can be a dumbass sometimes. when i wrote this yesterday, i was honestly thinking "pint", not "quart". a liter and a quart are pretty close in volume.

1 liter = 1.06 quarts

1 liter = 2.11 pints (which was what i was actually thinking when i posted that nonsense yesterday)

proz07

iTrader: (6)

you pretty much have it minus the whole shape thing and reason for it.

first shape does not matter so much as long as your feed to the 2nd pump is on the botom and the other 2 lines are toward the top with tank return at the top. that should make getting the volume you want easier.

2nd the only reason fo the surge tank is when you get lower on fuel in a tank with little to no baffle/foam so that when air does get sucked up it dosent get into the engine feed line. that surge tank will ALWAYS be full unless you run your tank dry. you are feeding that surge tank with the same efi pump that was running your engine before right?? unless you had a carbed FB??? that pump at basicly 0 psi will flow a retarded amount of fuel keeping the surge tank full and your 2nd pump just feeds off the air free pure fuel from the bottom of the surge tank. so all in all there is no SLOSH thers no room for it. hope that helps.


i made a picture in paint before i saw you already made diagrams but since i made it im putting it up anyway.


z

diabolical1

iTrader: (3)

thanks for responding ... and your diagram (although i already know how the setup goes).

yes, the car was carb'd before now and for the record, (far as i know) none of the FBs had in-tank pumps. the SE did have a baffled tank, but i'm not really interested in finding one just for this. if it comes to that, i'd rather just have the stock '83 tank modified. ironically, i'm using an SE pump for the high pressure side of this setup though.

however, it occurred to me after reading your response that i never shared the design that i plan to use. basically, i'm planning to use one of those pieces of thick square aluminum tubes (4-inch).
1. i plan to cut a 4-inch length
2. cut one side off and then,
3. cut my current cylinder in half and using a 4-inch length to
4. weld the half-cylinder onto the bottom of the square.

by my calculations, it should give me 1281 cc and moreover, fit pretty nice with space to spare. if i have the edges inside softened, obviously the volume gets decreased a bit, but i guess it should still be more than enough (integration was back in 1994 ).

i figure it gives me volume, space to play and the rounded bottom that help supply the SE pump.

unfortunately, i don't weld so i'll be needing to know if i'm wasting time with this design, which is why i started this thread. i'm going to have to pay someone to put it together and it's not my dime, but clearly it will be if there are screw ups. learning about general surge tank designs is a bonus.

i could post the sketch i made, but i just didn't feel like going through the trouble of putting it up on photobucket.

proz07

iTrader: (6)

well that changes things dont it....

first why do you or more importantly your customer??? want to run one?

2nd if your goal is only 2-220 i think you said for now do you really need it NOW. might be better to spend that money else where. but keep the designs for later.

i dont know much about the FB so the tank has no intank pump? even the FI gslse? and if not is the stock tank sumped some how from factory? maybe you can explain that to me. and your project is it going carbed or FI?

z

diabolical1

iTrader: (3)

well, my customer and i sort of have an agreement - he's my brother (afterburner16). so it's not the traditional "customer" relationship. he and i are both paying for parts, though he pays for most of them of course. however, what i'm really going to get out of this is a showcase because my car is taking a lot longer to build than his will.

i'm running the project build and i decided to run a surge tank because from my research it seemed to be the preferred setup of the two and i simply want to make the best effort not to **** up my brother's car because of ignorance. i want to give him the same attention to details and quality that i put into my car. personally, from an idea stanpoint, i prefer modifying the stock tank, that way i can use just one pump and be done with it. however, from all the setups i've seen with fuel injected FBs (save the stock SE, of course) many more run surge tanks than those who've chosen to modify the non-SE tank. naturally, some opted to get the SE tank. as i said, if i don't the get details i seek, then i'm probably going to just have his tank modified with baffles and a sump - besides i can get it cleaned at the same time, too.

the engine has been ported and ran on a Holley for years, but i told him to get with the times and get it fuel injected. so he said, if i build it and tune it, then fine! i've been building engines for years but so far the only tuning i've actually done have been with carbies. ideally, my car should have been my first EFI project, but his is a running car being converted, whereas i'm still building the motor for mine. so here we are.

and to answer the question about the SE, no, it didn't use an in-tank pump. it was external.

diabolical1

iTrader: (3)

compared to the others, the SE tanks have baffles and larger inlet and outlet hard lines. i can't remember all the details, but you can read them HERE if you want to.

the reason i've haven't gone out of my way to link other relevant threads here is the amount of time it's taken in the past for me to do so with other topics and it usually garners little attention.

however, from what i've found, there isn't much technical stuff out there on surge tanks. most of the hits you get when you search are basically someone being told to use one or someone telling you that they've used one.

off the top of my head, i remember the one Elwood designed and as i said it was awesome and inspirational. there was also an FD race car (i think it was in Japan or the Middle East, i forget ...) but that one used a custom one that was really cool as well.

proz07

iTrader: (6)

ok now i got it and did a little search mind you this is the internet and everybody has an opinion...
http://toyotaperformance.com/surge_tank.htm

states people go down to low as .5 liter and your tank is almost 3 times that size. you could possibly make it smaller as long as its kinda "tall" for the reasons stated in that page.

but now that i see that tank has no sump/baffle because of originaly being carbed this venture makes more sence and pretty much have to do. id have to suggest going with the surge tank way more than getting the tank baffeled. as baffles are only as good as where they are placed and still can fail at lower fuel levels I.E. see FD tank. the surge tank will pretty much give you a bullet proof fuel system for converting your carb to efi. so yes its worth the money to get it made in my opinion you should deffinatly do this and look at it this way you screw it up it isnt your car...lol sorry i had too

z

diabolical1

iTrader: (3)

hey thanks, man. that link was useful and it gives me some more direction. i'm not really sure if i'll feel comfortable going down to 500 cc, but at least maybe i could settle for 800 if i needed to. i was supposed to mock up my design today to test fit it in the car, but i ended up spending the day dealing with my own problems.

EDIT: not sure if 6.5 inches would be considered tall enough, but i'll see.