Monty

Due to the increased fuel requirements of twin turbocharging my SBC427, I had to make some modifications to my fuel system. I had a local racecar chassis shop install a sump in the bottom of my tank. I considered going with a racing fuel cell like a FuelSafe or ATL, but they didn't offer what I wanted. Anyway, the stock gas tank already has a plasic liner inside of it to help prevent leaks and fires in the event of a rear end collision.

I had them install two 3/4" npt pipe fittings in the sump and am going to plumb it with Aeroquip AN fittings and stainless steel hose. I am currently running two Aeromotive '1100hp' EFI fuel pumps and will probably run both of them in parallel with two -10 stainless steel fuel hoses going to a y-block at the front of the car and splitting again to the fuel rails. One of these pumps would probably satisfy my needs except at about 75%+ throttle. However, the redundant fuel systems is a nice guarantee against fuel system failure resulting in lean induced detonation and subsequent engine damage under boost. A new pump by Magnaflow is being released at this next weeks PRI show which they claim will support 2500hp, and has a duty cycle capable of supporting continuous street use, so I am going to look into that. Appearantly, they use some kind of gear reduction on it, kinda like the ministarters I guess, and they say it only uses about 15 amps. Each of the Aeromotives uses about 12 amps. They don't use a pump controller/voltage stepdown box though to control the pump speed. I asked about that and they said they "don't believe in that". I don't know, it seems the pump would last longer if it doesn't have to run at full speed all the time, even when max volume is not needed.

P.S. The turbochargers and wastegates should be here this friday...






[Modified by Monty, 11:46 AM 11/28/2001]

gkull

GD. Rules get touchy on everything including fuel cells. So I saw a couple of cars with tiny fuel cells (1-3 gallon) just mounted on the interior for FC requirements for racing only.

I was thinking about doing the same thing and it would have the additional use as a methanol tank for a separate high octane fuel durring NO2 use.

71coupe

Monty - the sump modification looks nice. I just read in one of my magazines about the same mod with a pre-made weld in sump.
Turbochargers? I thought you were starting a new project with a '69 Camaro.

Lohkay

Just curious....why a sump in the gas tank? I mean...its not like if you were feeding your engine with gravity. :lol: But if so you should put the sump on the back of the tank instead :lol:

hehe...sorry...just folling around but still curious about the real reason...

Monty

The reason for a sump in the bottom of the tank is two fold: electric fuel pumps are not vefy effective at pulling fuel, they are much more effective at pushing fuel. With a large head of fuel to pull out of the top of the tank, the effectiveness and durability of electric fuel pumps is reduced. You are putting a much greater load on the pump by making it pull fuel up, out of the tank and then back down to where the pump is located. Obviously, intank electric fuel pumps do not have thisprobelm since they are submerged in the sump. Having the sump at the bottom means that I am using gravity to keep the pumps pickup submerged and primed. The second reason for installing a sump is to ensure that the fuel pump pickup is always submerged, even under acceleration. The pickup points are actually facing the rear of the tank( consider that you are looking at the bottom of the tank, with the top of the picture being the front of the tank facing the differential), so that under acceleration, when the fuel moves up the rear of the tank, the pickup is alwasy submerged. Under braking and cornering the lowered section of the sump, combined with the baffleing created by cutting the holes from the tank to the sump helps ensure that the pickups are always submerged. The article that 71Coupe is referring to illustrates this. The tank and liner was not cut out to the same size as the sump. There are actually four 1" holes cut out with a hole saw underneath the sump. That way fuel can enter the sump from the tank, but it can't as easily get back out of the sump undercornering/acceleration/braking.

Another reason for installing the sump is to ensure adequate fuel volume. The lines instlled in the factory pickup are only 3/8" and would not flow enough for a forced induction EFI application like this.

I couldn't find a good '69 Camaro candidate, so I'm going to do this right now, and look for one next year. Anyway, I've already got this money pit, I probably don't need another.


[Modified by Monty, 1:14 PM 11/28/2001]

Lohkay

Yeah ok sounds right now...I guess I should just shut my mouth next time. :) But on the other hand I learnt something...didn't know electric pumps had a hard time pulling.

Monty

Hey, I didn't know either until a couple of years ago, when I called up Aeromotive and asked why their pumps are so darned loud. They told me one of the reasons was that I intially had it set up so that it was pulling fuel out of the top of the tank, increasing the load on the pumps, cuasing ti to work that much harder.

Way I look at it is that there's only two ways of learning about this stuff: learn it yourself through experience, or learn from others' experience. I've found learning from others' experience (and mistakes) to be a more efficient, cheaper, and less frustrating ;).

arnold

Monty-
Prior to altering the fuel tank, did you consider using a high volume/low pressure
pump to extract fuel from tank into a small container from which the high pressure
pump could draw the fuel? Did the Aeromotive pumps became much quieter when
given the task of pushing the fuel in lieu of pulling the fuel? Or is it premature to
ask?

Monty

Too early to tell yet if the sump will help lower the Aeromotive's noise. They are loud, especially two. I never really thought of using an intermediate container or tank. I'm trying to keep it as simple as possible - less weight, less potential problems.

scorp508

Monty, I'm playing devil's advocate here......

The sump seems to be in the dead center of the tank. What happens under heavy acceleration with a lightened fuel load? It sounds like you could be pulling some serious G's. Could the fuel get loaded up against the back of the tank and be pulled away from the sump?

Just curious. :confused: :)

Monty

There is a slight chance of that if the fuel level is low I guess. The fore/aft location was limited due to the way the tank is located inside the car. Under the bottom front of the tank is a removable support bar, and under the rear bottom is the rear frame crossmember.

The way the sump was installed allows fuel to get into it from the tank, but presents some restriction for it to get out. Before the sump was fabricated and welded onto the bottom of the tank, 4 1" holes were cut into the bottom of the tank with a hole saw. Then the sump was contructed and welded onto the bottom of the tank. It's not just a big cutout. That way fuel can easily get into the sump, but there's quite a bit of material between the sump and the tnak itself to act as baffling. That is also the main reason the openings face the rear of the car, rather than forward.

Obviously I won't know for sure until I drive it. I would imaging I would need to keep a minimum amount of fuel in the car to keep the pickup from being exposed under hard acceleration. But I would expect that it would only need to be 3 gallons or so, just guessing.

ralph

Monty, what application are you building this car for? I know you drag race, but at 650+hp, i think you are already imbalanced. I mean your car would have a hard time applying that power to the ground now, and doubling that power is really going to put the rest of car at a disadavantage. Do you actually plan to race it competitively, and if so what other plans do you have for the car? I'm sort of surprised you didn't dial in your current setup before venturing into the land of forced induction. Nonetheless good luck...should be an intersting project.

Monty

No particular application, and definitely not organized drag racing - I gave that up seriously about a year ago when I got to the point where roll cages started becoming mandatory and the IRS was not allowed. It'll just be a street machine, and maybe a couple of test and tunes a few times a year. Something to cruise around town in and take to the Friday evening cruise-in spot.

I've been wanting to develop a turbocharged setup for a few years now. I should have just done it last year, I would've seaved myself the cost of pistons, cams, and a set of custom headers, not to mention all the time it took dynoing, tuning, and installing the motor.

I have no plans to ever put enough meat on the back of it that it would ever hook, but I may address the rear end this spring. I'll eaither go with a Tom's Differential's 31 spline setup or install a Strage Engineering 9" 4-link setup and do away with the IRS altogether. A local chssis shop that I use, who does specializes in 4-link installs, does very good work for affordable prices. He custom makes the center sections and axle tubes. So you can put on any kind of end plates and brake systems you want.

I could then sell the Vette Brakes rear suspension I have now, the diff with 3.55 gears, and the Tremec TKO tranny and go with either a Jerico or G-Force road race style tranny. But that's all in the future. I'm sure that alot of people will think that it's a waste of money, and the results in terms of ET's won't be overly impressive, due to the fact I'll have to light foot it off the line. But I think it will be cool, and it wouls still have somehting like a 150mph trap speed.

I called Rad Rods by Troy last week to setup and appointment to get an estimate on them doing my car. They are the one's who did John Meaney's 1300hp C4 in this month's Popular Hot Rodding that everyone is talking about. They told me that since that article was written, he's down to 10.40 at 164mph. He runs the last 1/8th in 3 seconds flat, the same as a Pro Mod car! I think that's impressive. He's running a 100% stock drivetrain.

I am using the same turbo's and wastegates he used, and both of out motors use the same blcok and 18* heads. The guy that owns the machine shop I use is very good friends with John, John helps them tune the Speedpro SEFI int he NMCA/NSCA racecars. Anyway, they are going to get the cam specs and calibration file from him for me. So I hope to get similar results, although his is a 406 while mine is a 427.

Twin_Turbo

Monty,

Can you tell me what they did with the bladder on the spot where the sump is welded on? I need a sump like that too and I'm not sure if I'm going to just cut out a piece of the bladder or just cut away the skin and drill holes in the bladder.

Marck

[EDIT]

Okay, I read somem more and I see you drilled 4 1" holes...that answers the above question. But now.. what happens if the fuel can penetrate between the skin & the bladder? Or did you use some sort of sealing method to remedy that?




[Modified by Twinnie, 1:45 PM 12/3/2001]

Monty

The bladder is actually a hard plastic container, about 1/8" thick material. It appears the metal tank is comprised of an upper and lower half, they put around the plastic and then weld the seam all the way around.

My tank was in good shape before we put the sump on. There was no rust and the seam weld was complete. I thought about the fact that a small amount of fuel could get between the bladder and the tank, but I don't think it will be a problem. The fit between the bladder and tank is very tight, there isn't any room at all that I can tell. The plastic liner was a only used in the later C3's anyway. When I asked the guy to do it, I told jim about the liner, I thought it was rubber rather than hard plastic, and he said that he had done several other C3 Corvette tanks, and none of them had the liner. I don't know the exact year, but I am guessing, based on the tanks he's done and other comments made by other forum members, that the plasic bladder was added to the tank around '77 or '78. It owuldn't surprise me if it was a federally mandated safety deal.

I can't really think of any type of sealer that would be 100% fuel safe that you could put between the tank and bladder at the opening. But I really don't think it is a problem. I'll let you now though. If it is, I guess I'll have to get an ATL or FuelSafe fuel cell made afterall. But they're about $1000.

Tomulrich

I thought the C4 in popular hot rodding magazine had a 4L80E transmission......or was it stock?

are you running a vacuum pump on you motor?.....what is your opinion on vacuum pumps? What about the use of low tension rings....on a street/strip car?

Monty

Yeah, you're right, the tranny is a built 4L80E. I had the differential and halfshafts in mind when I said it had a stock driveline.

I'm not running a vacuum pump right now, but I am switching from an in the pan Titan Pro billet wet sump pump to a Stock Car Products external west sump pump, basically like a single stage dry sump pump. SpeedPro/F.A.S.T. recently released their eDist distributorless ignition system which will interface with my SpeedPro SEFI unit, so I won't be running anything off of the camshaft.

I think vacuum pumps can be made to work pretty well on a street/strip motor. It probably isn't worth the money and complications for everyone, considering the power benefit. But if you want that last 10-15 hp then go for it. With a vacuum pump, the low tension rings work very well and still maintain good oil control. But the ultra-low tension rings require too much vacuum to work, so I definitely wouldn't recommend them on a street car. You need a 4 or 5 stage dry sump pump to produce enough vacuum to get them to work, and it's still not good enough in the long run.

I don't remember the exact numbers, but low tension rings are nothing more than .030" under oil control ring sets, and ultra-low are .060" oil control ring sets. So basically, if you had a 4.030" bore, you'd run a 4.00" oil control ring set. I've never run low tension rings myself, but I know a few who do, both with and without a vacuum pump.

Also, you don't want too much vacuum or it could actually pull the oil out from the bearings. This is an extreme case, with like 17+ inches of vacuum, and can usually only be created by using a 4 or 5 stage dry sump pump. I think vacuum pumps tyically only make about 8-12 inches of vacuum depending on how many vanes it has and which pulleys you use.

76Vette350NOS

Once primed, I don't think the fuel pumps will be appreciably quieter with the bottom sump. This is because as long as the pumps are below the pick-up, any upward piping has a corresponding downward piping, creating a syphon effect. Once primed, you could disconnect your pumps and the tank would still completely drain all by itself.

Monty

You're probably right, that's a good point.

The noise really isn't a problem anymore, I'm kind used to it, and with the exhaust and my stereo, I can't hear barely hear it anyway.

In some ways, I like hearing it, cause I know by the sound it's working.

StingrayRacing

Lookin good!!!

I'm running a similar sump with one of those Blue 1000hp pumps...what have you decided on for exhaust manifolds...custom I assume.