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Fuel starvation in 3rd gen--solutions?

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Old 02-08-07, 02:51 PM
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Fuel starvation in 3rd gen--solutions?

So, the left-hand-turn starvation issue is well known. Here are some of the fixes or workaround I've heard:

1) Never run less than 5/8 of a tank -- which sucks for long track days
2) Run a swirl pot or accumulator -- you need another fuel pump, the tank, and a place to mount it
3) Modify the OEM tank (remove volume or install baffles)
4) Run a fuel cell

Are there other solutions I've missed? For those of us who run on the street and the track, 2 and 4 are out. 3 is expensive, and 1 is annoying as hell.

Does anyone have any other ideas?

-ch
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Old 02-08-07, 02:55 PM
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#3 is the cheapest and most elegant solution. A small "tank" that encloses the fuel pickup is built around the stock baffle. The return line would then dump into this tank so the pickup could never starve.
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Old 02-09-07, 09:13 AM
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IIRC, the 95+ fuel tanks (or maybe it was 96+) were changed to help aid this problem (not completely fix it though).
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Old 02-09-07, 07:33 PM
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I want to fix this problem.

How would I go about doing #3?

Apologizes for the hi-jack.
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Old 02-09-07, 08:20 PM
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I think this is your # 2 http://www.more-japan.com/product.ph...cat=544&page=1

I thought our tanks allready had baffles to prevent this? Was it not untill the 99+ that they added baffles?
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Old 02-10-07, 11:03 AM
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Originally Posted by NeoTuri

How would I go about doing #3?
Check out the posts from gfelber and streldoc:

https://www.rx7club.com/race-car-tech-103/fd-gas-tank-baffle-slosh-problem-233215-post2250917/
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Old 02-10-07, 12:37 PM
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Hmm... if I'm going to go through the trouble of fixing the OEM tank, I'd rather eliminate the starvation problem altogether and get an external tank (#2).
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Old 02-10-07, 12:59 PM
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Just Get A Surge Tank Nd Fix It All!
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Old 02-11-07, 06:17 PM
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Damon, that thread is really helpful. I'm trying to visualize what Gene is talking about...have you seen any pictures of the mod he used?

-ch
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Old 02-11-07, 08:37 PM
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For reference, here's the ATL catalog. I'm wondering if something from page 20 could be adapted? (I don't think the fuel tank opening is 5x5x6, but the tanks are 'semi flexible' so...

http://www.atlinc.com/US/download.ph...eCatalog06.pdf

-ch
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Old 02-11-07, 10:45 PM
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I seen another racer at the track who put this in his tank. Fuel cell foam.
http://store.summitracing.com/partde...5&autoview=sku
He said it fixed the problem he was having.
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Old 02-11-07, 11:04 PM
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Well, here's another use for small digital cameras:



-ch
Attached Thumbnails Fuel starvation in 3rd gen--solutions?-img_0966.jpg  
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Old 02-11-07, 11:11 PM
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So the above post: the driver's side of the car is up in that picture. You're looking straight down into the fuel tank. The pump and inlet filter go into this bucket with the fuel level sensor hanging just outside it (down in the picture).

You can also see that there is a little track that runs back and forth in the left and right directions of the car. There is an inlet to the bucket at the end of the track (in the lower right hand corner of the picture).

There are large baffles in the tank, but they look mostly useless in stopping sloshing. Since the bucket (and the pump) are on the left side of the car, left hand turns push all the gas to the right and out of the bucket. Under accel and right hand turns the fuel tends to cover/fill the bucket. (Braking is not an issue because the car isn't under power and the return line is refilling the bucket.)

The bucket is maybe 4" tall. If it were taller, it would probably work more effectively. However, if you do this you can't use the fuel level gauge properly.

But seeing this I don't understand the modifications that the guys were talking about on the other thread...

-ch
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Old 02-12-07, 07:13 AM
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While I was doing my swap I decided to try and fix this problem as well so I decided to sump the tank, so instead of running one pump I am running 2. I left the stock pump in its place but I also have an inline bosch pump gravity fed by the sump, is this a solution? NO! Definately works better then the one pump in the tank but I wouldn't say it's perfect, I notice minor dips in the fuel pressure(5psi) while going around hard corners the last track event I was at. I only noticed this after the tank was just below half, I have been searching for the cure for this for along time so I am curious to see what you come up with.

BTW I have tried twin pumps in the tank when my car was rotary, tried feeding one pump with another(one intank, to one inline) and nothing worked better then my current setup. I monitor the pressure with a greddy fuel pressure gauge on the pillar mount.
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Old 02-12-07, 08:18 AM
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Paul, can you clarify? You have an external reservoir that has a gravity-fed outlet that goes to another pump? (Like the Rotary Extreme kit?) Where did you put the reservoir?

-ch
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Old 02-12-07, 08:30 AM
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Originally Posted by darkslide750
I seen another racer at the track who put this in his tank. Fuel cell foam.
http://store.summitracing.com/partde...5&autoview=sku
He said it fixed the problem he was having.
This looks like a great product, anymore information on it? Correct me if I am wrong but this is how fuel cells work, they really don't have any baffling, just foam to keep the fuel from sloshing and rapidly spilling out in a crash.
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Old 02-12-07, 08:42 AM
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Foam is much more about safety than eliminating starvation. Check out the ATL catalog--they install surge tanks in the middle of the foam. I don't think the foam alone is a solution.

-ch
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Old 02-12-07, 08:42 AM
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Originally Posted by hyperion
Paul, can you clarify? You have an external reservoir that has a gravity-fed outlet that goes to another pump? (Like the Rotary Extreme kit?) Where did you put the reservoir?

-ch
Sorry for the confusion, an actual sump in the tank (drag racing style). The tank was modified with a sump added to the bottom and welded in place with 2 -10an ports welded to the sump. Here is a pic, not using that pump or location...... but this is the sump.
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Old 02-12-07, 09:04 AM
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So the inline pump is external?

Can you lay out the path of the fuel flow, such as:

stock pump pickup in tank
stock pump outlet to reservoir
reservoir overflow return to tank
secondary pump pickup in reservoir
secondary pump outlet to FPR
FPR return to reservoir

Or whatever the right routing is...

-ch
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Old 02-12-07, 09:29 AM
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Yes, the inline pump is external. Both pumps are connected to a distribution block, then to an aeromotive fuel filter and from there to a single -8 feed line to the fuel rail. At the end of the second rail I have a FPR, and a return line off the regulator bleeding off the excess fuel with a -6 return.

I am currently thinking of changing my setup, I want to simplify things......possibly a returnless system like the Vette uses.
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Old 02-12-07, 09:37 AM
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Ah, thanks for the clarification.

As far as the Vette goes, it's a return-less system in that the FPR is mounted in the tank. (You're doing an LS1, right?) Most people are putting the FPRs just outside the tank or in the engine bay.

I'm wondering if there is room for this under the car:

http://www.lancershop.com/customer/p...?productid=538

You could use the stock pump to fill this, and then put a pump inside that would go out to the FPR. I've no idea how to get specs on this, though. SARD's website is mostly under construction...

-ch
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Old 02-12-07, 10:14 AM
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I have been running my LSX for about a year already.
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Old 02-12-07, 10:24 AM
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Originally Posted by hyperion
But seeing this I don't understand the modifications that the guys were talking about on the other thread...
Material is added to the bucket so the walls are higher. Then add a lid that fits over these new walls with an opening in the top just big enough to get the fuel pump through. Plumb the fuel return through the lid to help ensure there is always fuel near the pickup.
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Old 02-12-07, 10:26 AM
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Ah, but how did they deal with the fuel level sensor? If you put walls up around the bucket, you'd have to get rid of the sensor...

...or am I missing something?

Also, they never posted the Mazda part number for the top part of the baffle. I'd rather buy than fab.

-ch
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Old 02-12-07, 03:30 PM
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Originally Posted by hyperion
Ah, but how did they deal with the fuel level sensor?
It's not in the way? The fuel level sender attaches up near the top of the tank cover and extends to the right of the pickup. This mod essentially creates a bowl with a lid on it just around the fuel pickup.
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