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Fuel starvation in 3rd gen--solutions?

Old 03-08-07, 06:37 PM
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Originally Posted by DamonB
The 95 tank doesn't solve those problems.
I have yet to see any *definitive* proof that the 95 tank is a significant upgrade. Just lots of rumors and speculation...
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Old 03-09-07, 01:32 AM
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I'm going to post the results of my simple cover which I believe is similar to the 96+ tank design. With the stock 94 tank I'm getting starvation at 5/8 of a tank on DOT race tires. We'll see how much of a difference the cover makes, if any.

-ch
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Old 03-09-07, 02:09 AM
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Originally Posted by FDNewbie
I have yet to see any *definitive* proof that the 95 tank is a significant upgrade. Just lots of rumors and speculation...
Damian's car has a '95 tank and he doesn't have any fuel issues until he's down at or below 1/4 tank, about 14-16 gallons used. Then he will start to starve on long sustained left turns (like turn 5-6 at MAM.) He can generally pull 1.4-1.5 g's in a normal flat 90 deg turn.

My car with the '93 tank will fuel starve before my gas gauge even gets down to the 'Full' mark, at about 5-6 gallons used in left turns. The worst is at Road America, where there's a turn (6) at the top of a hill, the gas is thrown forward and up, and I will starve there at only 4 gallons used unless I'm careful. I can generally pull about 1.2-1.3g's in the same turn.
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Old 03-09-07, 07:27 AM
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Originally Posted by hyperion
I'm going to post the results of my simple cover which I believe is similar to the 96+ tank design. With the stock 94 tank I'm getting starvation at 5/8 of a tank on DOT race tires. We'll see how much of a difference the cover makes, if any.

-ch
Is the 1996+ tank cover a bolt-on ?

:-) neil
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Old 03-09-07, 11:30 AM
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If you have a mid-94 tank or later, yes. The way to tell is if your fuel tank bucket has provisions for tabs or not. My car, a 94, has them:



Older tanks have the plastic bucket, but the perimeter of the bucket does not have those little loops built in. The only way to be sure is to look inside your fuel tank...

-ch
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Old 03-09-07, 01:31 PM
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So our stock tanks have that plastic bucket in them... how does fuel make it into the bucket? Wouldn't it need check valves around the bottom of the bucket to allow fuel to enter (especially if you add a cover)? How big is the bucket?
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Old 03-09-07, 03:00 PM
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The bucket is a gravity feed system. There are two cases:

1) The fuel level is above the bucket wall (about 4" tall). In this case, the fuel completely fills the bucket

2) The fuel level is below the bucket wall. In the picture above you can see a small opening on the upper right side. There is a divider that runs left to right. When the car is level and not accelerating, the fuel comes through the hole and through hydrostatic pressure is forced into the bucket and fills it to the level of the rest of the tank. When cornering or braking, fuel can leave through the hole but the divider ensures that most of the fuel stays in the bucket--and drains relatively slowly.

The problem is that when you hit the brakes and go to 1.5G, all the fuel just launches right out over the sides of the bucket. The momentum of the fuel pushes most of it out, so the bucket isn't very effective. Supposedly, a cover can address this problem to some degree...I'll be testing mine (shown earlier in this thread) on Monday at the track to see if it makes any difference.

-ch
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Old 03-09-07, 04:07 PM
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I might have missed it, but can you make an internal bucket/surge tank that is feed back the fuel-return ?

I believe my 1993 Mercedes has this. I'll post a picture if I can locate it.

:-) neil
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Old 03-09-07, 04:26 PM
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The bucket cover--or at least mine--has the return line going into the bucket itself. The FEED and other aftermarket systems work the same way.

-ch
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Old 03-09-07, 04:34 PM
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A little off topic, but, hyperion, did you go to Laguna yet? Wondering because me and a fellow fd owner will be there with NASA on the 21st. I'd love to see your car.

Matt
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Old 03-09-07, 05:21 PM
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weather until he's down at or below 1/4 tank, about 14-16 gallons used. Then he will start to starve on long sustained left turns (like turn 5-6 at MAM.) He can generally pull 1.4-1.5 g's in a normal flat 90 deg turn.

My car with the '93 tank will fuel starve before my gas gauge even gets down to the 'Full' mark, at about 5-6 gallons used in left turns. The worst is at Road America, where there's a turn (6) at the top of a hill, the gas is thrown forward and up, and I will starve there at only 4 gallons used unless I'm careful. I can generally pull about 1.2-1.3g's in the same turn.[/QUOTE]Understood. But the only reason I question the conclusion you're jumping to is, do we have any similar data from '94 tanks? Ie, is there anything special about the '95s that is different than the '94s? Or is this simply another case of '93 FDs being shafted in poor initial quality?
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Old 03-09-07, 05:45 PM
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Originally Posted by FDNewbie
But the only reason I question the conclusion you're jumping to is, do we have any similar data from '94 tanks? Ie, is there anything special about the '95s that is different than the '94s? Or is this simply another case of '93 FDs being shafted in poor initial quality?
The 95's have "improved" baffles around the fuel pickup. It's all relative. The 95's are not quite as bad as the earlier cars but the 95 baffle does not actually solve the problem.
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Old 03-09-07, 05:48 PM
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Originally Posted by DamonB
The 95's have "improved" baffles around the fuel pickup. It's all relative. The 95's are not quite as bad as the earlier cars but the 95 baffle does not actually solve the problem.
Damon, you're saying this w/ considerable confidence, so I'm guessing you've verified this for sure? I'm not doubting you; as I said in my earlier post, I have *never* seen solid data/pics/info supporting this, that's all. Curious if anyone here actually has, or are we all actually repeating speculation?

And I'm specifically speaking of an improvement in the '95 tank over the '94 tank (not 94 and 95 vs. 93).
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Old 03-09-07, 05:50 PM
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Originally Posted by FDNewbie
Damon, you're saying this w/ considerable confidence
That's because the 95 cars still experience the same problem.

It doesn't matter which tank we're discussing. They all starve badly, the 95's just aren't quite as bad as the earlier cars.
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Old 03-09-07, 06:10 PM
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K...I read ya loud and clear
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Old 03-09-07, 06:17 PM
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Originally Posted by DamonB
That's because the 95 cars still experience the same problem.

It doesn't matter which tank we're discussing. They all starve badly, the 95's just aren't quite as bad as the earlier cars.
I agree with one minor correction.

Damian's car shows that if your goal is to make a 15-30 minute session on the track without starving, the '95 tank can do that. Just fill it up imbetween each session. The '93 tank is not sufficient for higher hp cars.

If you want to actually use all the fuel in the tank (down to, say 1 gal or less left,) you are correct, they all will not work.

FDNewbie, I don't have any data from a car with the '94 tank, sorry.
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Old 03-09-07, 06:28 PM
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Originally Posted by GooRoo
FDNewbie, I don't have any data from a car with the '94 tank, sorry.
No worries; again my concern was finding out if everyone was harping on a feature/upgrade available on '94s as well, but simply saying it's a '95 thing only, only b/c we haven't tested it on '94s

From my experience, a whole host of modifications were made during mid-production in '93. These modifications were found on a good percentage of the '94 FDs, and ALL the '95 FDs. That's what I think the case is here as well. Yet the way ppl refer to it on the board makes it seem it's a '95 and up thing, exclusively - which I highly doubt. THAT'S what I'm seeking a clarification of

~Ramy
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Old 03-09-07, 06:50 PM
  #118  
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Sweet someone else has already done this! I plan on doing something very similar soon.






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Old 03-09-07, 07:11 PM
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If it helps, I have a 94' and I have only seen fuel starvation on left handers when my fuel level was around 1/4 or less. However I have only done a couple of track events on my car so far (it's currently in pieces waiting to be worked on).

As for the stock plastic bucket... how about replacing the "hole" in the side of the bucket with a check valve? Or maybe a couple of them, on several sides of the bucket. I think that coupled with the cover would be a good solution, basically like one of those trap boxes or whatever.

However I'd still like to know how big that box is... how long do you think the fuel trapped in the box lasts? Is it enough for a long high-G left hander?
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Old 03-10-07, 03:00 AM
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Originally Posted by rotoober
A little off topic, but, hyperion, did you go to Laguna yet? Wondering because me and a fellow fd owner will be there with NASA on the 21st. I'd love to see your car.

Matt
Hey Matt,

I go to Laguna this Monday with Trackmasters. I'm hoping to get my car sorted for regular track use...I'm waiting on a brake kit and I'm installing an Accusump in the next month or so. Plus I'm redesigning the cooling and intake system. What a project! Let me know what other track events you're going to--I'd be happy to take you for a spin in the car.

-ch
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Old 03-10-07, 03:04 AM
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Originally Posted by RaceDriver7
If it helps, I have a 94' and I have only seen fuel starvation on left handers when my fuel level was around 1/4 or less. However I have only done a couple of track events on my car so far (it's currently in pieces waiting to be worked on).

As for the stock plastic bucket... how about replacing the "hole" in the side of the bucket with a check valve? Or maybe a couple of them, on several sides of the bucket. I think that coupled with the cover would be a good solution, basically like one of those trap boxes or whatever.

However I'd still like to know how big that box is... how long do you think the fuel trapped in the box lasts? Is it enough for a long high-G left hander?
The check valve approach is exactly what Gene Felber did on his car, plus a cover. With this he could run down to a few gallons. This is the same approach used by ATL and other fuel cell companies.

-ch
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Old 03-10-07, 03:11 AM
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Originally Posted by afgmoto1978
Sweet someone else has already done this! I plan on doing something very similar soon.






I'm guesstimating that this column holds about 180 cubic inches of fuel, or about three liters of fuel. At WOT on a big motor, that's about 45 seconds of fuel. Assuming that fuel can get to the pickup of the filler pump, it would be pretty bulletproof.

That said, I'm not crazy about the build quality, but that's what I get for being a picky bastard. I also don't like the fact that the bottom of the filler pump is not supported. Having all the weight on the fitting at the top is not optimal.

-ch
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Old 03-12-07, 09:21 PM
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Hyperion, so did the "bucket cover" help any at the track?
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Old 03-13-07, 03:07 AM
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Track Report: Laguna Seca, Monday March 12th

Well, some very encouraging news to report from my track day at Laguna. The short version is that the tank bucket mod allowed me to run down to below 1/4 of a tank--10 gallons less fuel than before. Details:

I started this thread after my last track day there in January where I was experiencing starvation in turns 11 and 2 (both left handers following heavy braking zones). I was getting engine cutout due to air in the lines at around 5/8 of a tank. (All tank measurements refer to what the gauge reads while stationary in the paddock.)

After some very helpful information and ideas from the forum--especially Gene Felber--I created a cover for the slosh bucket in the FD gas tank. Mine is a '94 and has slots built in for tabs.

At Laguna I ran five 20 minute sessions and took some notes along the way. My car has Michelin Pilot Sport Cups which are short of a full slick but are nonetheless an extremely sticky DOT road racing tire. I run 285/35/18 on all four corners and have a fairly aggressive suspension. This is only the second track day for these tyres.

Here's what the tank read at the start of each session.

Session 1: 3/4 tank
Session 2: 5/8 tank
Session 3: 1/2 tank
Session 4: 1/4 tank

I ended session 4 with the tank reading this in the paddock:



I put about 5 gallons in the car for the last session just so I didn't run out. After that I filled the tank which took a further 12 gallons. Based on my burn rate, I would say that I ran the tank all the way down to about 4-5 gallons without any starvation. This includes braking from 130 MPH and then going through a 200 degree left hand corner (where I had starvation issues previously).

The track was hotter than in January--bright sun and near 80 degrees air temp--so I would say grip was a bit better this time around.

I should note that during the sessions the fuel gauge drops 1/8-1/4 lower than what it reads at rest. For example, during session 3 the gauge was below 1/4 for much of the session, but when I came to rest it settled right at 1/4.

This is only one datapoint. I haven't autocrossed the car, nor have I run at a high-speed track where you have a series of high-G corners in sequence. However, it's very encouraging to be able to run down to 1/8th of a tank when before I was having trouble at 5/8.

I have no doubt that an in-tank surge enclosure or dual-pump system will work even better, and I've no idea if this mod will work for all applications. But for me, it's a big improvement!

There is an autocross this weekend that I may attend just to test a bit more. I may also go to Infineon on Friday if I can make the time.

-ch
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Old 03-13-07, 08:31 AM
  #125  
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Cool, very good info. Sounds good enough for me. I'm gonna make a cover for my tank too.
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