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Fuel starvation in 3rd gen--solutions?

Old 02-17-07, 05:00 PM
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Interesting....so a fence with a gap for the level arm to clear then. And the top of the fences having a lip to minimize "spillover". Again, it's just to keep the fuel from sloshing (or slowing its rate of slosh). Although I don't have sustained high G cornering experience...are there that many high G corners where we go WOT through it? If not, then the fuel flow rate will be less than the 1L per 15 seconds; hence not a huge volume needs to be trapped.

I'd love to see what you have fabricated, Hype!

Weird that no-one tried stuffing the foam around that ATL surge tank w/ the check valves.

Good topic!

Originally Posted by hyperion
Actually, let's talk about what happens. There are two conditions that lead to starvation in the 93-95 tank:

1) long sweeping left hand turns -- at 1g, the fuel surface is at a 45 degree angle in the tank. Much of the fuel that was in the surge bucket flows over the side, and what's left (1/2 * 3x3x10, or 45 cubic inches, or about 2/3 of a liter) is quickly depleted by the motor which consumes about 1L every 15 seconds.

2) heavy braking followed by a left hand turn -- the car dives under braking (3 seconds) throwing the fuel over the front wall of the surge bucket. Then the car turns in, launching more fuel over the right side of the bucket. There is probably less than 1/3 of a L left, so even moderate acceleration will cause starvation.

The latter case was what happened to me in turns 11 and 2 at Laguna. Heavy braking followed by a left. I had starvation at just over 1/2 tank.

The bucket in the tank (shown earlier in the thread) tries to do what you're suggesting: block fuel from three sides. Unfortunately, since the fuel level sensor arm hangs over the bucket side, you can't just make walls that go up to the top of the tank.

The factory approach is a cover that sits across the bucket and below the fuel arm. This provides two advantages:

1) Reduced 'slosh' over the sides of the bucket under braking or sudden turns
2) During long left turns the bucket holds more fuel (although some of it is leaking out through the hole where the pump and return tube go through the cover). My guess is that the capacity of the bucket is roughly doubled with this approach.

I have fabricated my own cover and will be testing it at Laguna in early March.

-ch
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Old 02-17-07, 06:10 PM
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The only concern I have about making the bucket taller (with walls) is that the column will weigh 6-10 pounds. The bucket is held on to the bottom of the tank in a somewhat flimsy way, and I'd be worried the force of that fluid would rip the bucket off the tank floor.

Here's a few pics of my prototype. I hand-cut the metal with aviation snips, but I got some pretty good dimensions of the tank and made a CAD database of the part so I can reproduce it. You can see the method I used to determine the exact pump location. (The mock-up cover is a cardboard and aluminum foil sandwich.)

The finished part has a rubber gasket for a good seal with both the bucket and around the pump. Some gas can escape out that hole, but the flow rate is limited.

-ch
Attached Thumbnails Fuel starvation in 3rd gen--solutions?-img_1023.jpg   Fuel starvation in 3rd gen--solutions?-img_1027.jpg   Fuel starvation in 3rd gen--solutions?-img_1034.jpg   Fuel starvation in 3rd gen--solutions?-img_1038.jpg  
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Old 02-19-07, 10:27 AM
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I'm trying to imagine where you would run at wide open throttle in a high G turn for 30 seconds. Maybe Daytona? Anyhow, my external surge tank is 2.5 inches in diameter and about 9 inches high. We have a standard stock car 8 gallon fuel cell with the pickup in the extreme right rear corner of the cell. There's no baffling in the cell other than the usual foam which doesn't really baffle but is there to prevent big explosions if something bad happens. We've run the car at Portland, Laguna Seca and Pacific Raceway (Seattle). Pacific and Laguna are "backwards" tracks for road racing so they favor my circle track cell. But Portland is a clockwise track. Before we put in the surge tank, the car would cut out due to fuel starvation after just a few laps at any track. After installing the surge tank we haven't had a hickup.
One thing to remember is the stock fuel tank has a strainer on the end of the pickup in the tank. Since switching to the cell, we just use an open pickup line. We had to add an inline fuel filter in our low pressure fuel line on the suction side of the low pressure pump. This is because there is a tiny screen in the suction side of the stock GSL-SE high pressure pump that plugged when we first made the mods. The inline filter prevents that problem.
By the way, we installed the surge tank next to the cell. We used all of the stock parts and placement of the high pressure pump, filter and lines.
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Old 02-19-07, 11:10 AM
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The other thing to remember is the fuel return line. Fuel is constantly being returned to the tank from the fuel rail. If you plumb the return into your bucket or surge tank then you are in fact constantly replenishing the fuel level around the pickup even as fuel is being consumed by the pump. At high power less fuel is returned, but nonetheless this is why your bucket or surge tank doesn't need to hold as much fuel as you might initially guess.
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Old 02-23-07, 01:46 PM
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okey dokey....I found a tank baffle from FEED that claims to solve our problems. I have a friend who has a car import/parts business (quite a large one) and can get it. However, in respect of the forum rules, I've emailed Ramy to see if he can do it too. So let's see what he says.



"When driving hard, at anything below ½ - ¼ of a tank, “fuel slosh” can begin to occur, and can starve your car of fuel.

What happens is the fuel moves around in the tank under hard acceleration, braking, and cornering. This can move the fuel away from the pickup, and air will be sucked into the fuel system. This starves the car of fuel, causing the car to stutter or in extreme cases stall. It also causes the car to run very lean, and as this usually happens when the car is being driven hard, it is not good for your engine. To solve this problem, Fujita engineering has developed this baffle. It traps fuel around the pickup, meaning that it can never run dry under normal conditions.

A worthwhile addition to any car that is used hard on the road, goes onto the track, or goes drifting.

We would recommend this to be fitted by your local tuner to ensure the fuel system is fitted back correctly."


Price is around $250 + shipping.
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Old 02-23-07, 01:56 PM
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Very cool! I'd get the dimensions to make sure you can actually put this down through the fuel tank access panel. Also, I'm not clear you this would be secured to the bottom of the tank, nor how the fuel level sensor would work with it. Are you sure this is an RX7 part? Or is it a universal application?

-ch
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Old 02-23-07, 02:08 PM
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I really don't know but it says it's for the FD3S...I was hoping Ramy can get more info. I can't find this part on Fujita's site. My friend (actually friend's friend) says the instructions are in Japanese. Here's a link to his site: http://www.neweraparts.com/Default.a...&ProductID=195
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Old 02-23-07, 02:18 PM
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Guys, I have all of the images from Gene's site, but have PM'd him for permission to repost.

Originally Posted by hyperion
Here's the site on wayback--but no images!!!

http://web.archive.org/web/200505160...uel_system.htm

-ch
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Old 02-24-07, 12:33 AM
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I've been dealing with this in the race car. I am running a 16gal fuel cell in an FB, and below 5/8 of a tank, it gets air in the fuel lines. I am working on converting a fuel filter into a surge tank, along with a second pump. Total cost is less than $100 and should be an awesome solution. I'm pretty sure you could copy the design for the same price on a street car. I'll have some pictures up tomorrow of the build.
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Old 02-24-07, 11:49 AM
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Originally Posted by jimeby
I built an external surge tank for my GSL-SE racecar which solved all of my starvation problems. There is a very good discription of a simple surge tank like the one I built here: http://www.sdsefi.com/techsurge.htm
This one is much fancier that the one I built. I welded caps on a piece of 2.5" exhaust pipe and then welded small tubes in for the fuel line connections. Since it's all low pressure I only used push on rubber hose with hose clamps. I had an old inline Bosche fuel pump laying around that I used for my aux supply pump. So, I spent no money whatsoever to build it.
You just have to decide if you have:
A) More money than time.
or
B) More time than money.
For me, it always has been B.
You could always go the route I plan on taking when I convert to EFI.

Grab a Volkswagen fuel pump.

VWs have a 1-liter surge tank ("fuel pump reservoir) that gets fed from a low pressure pump in the tank, and the fuel rail return gets fed through the reservoir before being overflowed to the tank.

Downside: New from VW, the reservoir is about $150-200, and the pumps are in the $300 range.

Upside: I can find "known good" pumps with reservoir for $50.

Further upside: The pumps designed for CIS normally operate at 120psi. They are some of the baddest pumps you can get, and will flow a LOT at "only" 45-60psi.
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Old 02-24-07, 09:44 PM
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I recently stuffed my fuel tank with fuel cell foam. My tank baffling had broken - fortunately it wasn't to solve a starvation issue.

Yes, you need to leave an opening on the right side of that plastic box under the pump, since the fuel float needs room there. But I stuffed a block of foam fore and aft of the pump box, and this keeps the blocks on the right side of the tank pushed over/away from the float.

I'm sure an aux tank would work really well if you're trying to run on a fraction of a tank to save weight, but for most of us I think the fuel cell foam is quite good. And the whole bit cost under $50.

Dave
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Old 02-26-07, 07:38 AM
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Originally Posted by HedgeHog
I really don't know but it says it's for the FD3S...I was hoping Ramy can get more info. I can't find this part on Fujita's site. My friend (actually friend's friend) says the instructions are in Japanese. Here's a link to his site: http://www.neweraparts.com/Default.a...&ProductID=195

Any news on this??? Group buy would be nice.
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Old 02-26-07, 10:11 AM
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Originally Posted by paul_3rdgen
Any news on this??? Group buy would be nice.
Go rush Ramy...he's incommunicado...so far.

If we go with my acquaintance's shop, he's only offering 10% and shipping will be either from Japan or England (his two bases).
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Old 02-26-07, 01:33 PM
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Well this was good timing. I'm about fed up with the fuel starvation I'm getting on the street, much less autocrossing and track days. I only get about 80 miles of good driving before it feels like I'm riding on a bucking bull if I'm not careful. Fuel starvation confirmed as the culprit thanks to the fuel pressure gauge flicking wildly.

Was excited to find this thread...but dang, now I'm disappointed that there's not a better solution. Really hate to add an external surge tank since it's a street daily driver. But I cringe at having to modify or replace the fuel tank, too. Anyway, if anybody finds a good solution and there's a group buy, count me in, but I guess in the mean time I'll have to stick with stopping at the gas station every damn day......
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Old 02-26-07, 01:57 PM
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Originally Posted by HedgeHog
okey dokey....I found a tank baffle from FEED that claims to solve our problems. I have a friend who has a car import/parts business (quite a large one) and can get it. However, in respect of the forum rules, I've emailed Ramy to see if he can do it too. So let's see what he says.
I'm liking this but I can't seem to picture how this is going to fit through the OEM tank opening. More info please

As Pete mentions below one member fixed the problem by capping the OEM baffle box and placing several (4 I think) large fuel cell ball check valves around the periphery of the OEM baffle box - permitted flow in from any side but never allowed fuel to slosh out of migrate out of the tank.

I would experience fuel starvation in turn 3 at VIR on Hoosiers at 1/2 tank. teh tunr is a 5-7 second high G left hadn sweeper.... FWIW.
Regards,
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Old 02-26-07, 11:46 PM
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I'll request a scan of the instructions. Fingers are crossed.

BTW, has no one tried putting in the ATL surge tank w/ the trap doors? That seems to be the simplest solution...or is it.
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Old 02-27-07, 07:25 AM
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I'm starting to think I must have a bigger problem. I was on the way to work this morning with exactly half a tank. Just starting off from a stoplight and turning left, I can't give it more than 1/4 throttle without the fuel pressure gauge fluttering. Granted it's not bucking yet, but I know from experience it's close.

I checked my baffles and from what I can tell they're all still attached. Though I do have an early 93 so I guess maybe that's part of the problem. I was just remembering somebody mentioned tank pressure being an issue. I just recently had to replace the gasket around the fuel pump to fix a bad leak there. I now get a coke-can opening sound when I open the cap to fill up with gas. Is there anything else I should be checking on that front? I do notice that if I just turn the switch on, I get full fuel pressure but then it slowly creeps down, maybe a pound every 10 seconds. Does that sound normal?
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Old 02-27-07, 11:14 PM
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^maybe time for a new fuel pump?
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Old 02-27-07, 11:21 PM
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Seems like I'm late to this thread, and I didn't read all 5 pages (just this last one), but I'm assuming that those with these fuel pressure problems have recently installed a fresh fuel filter?
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Old 02-28-07, 07:42 AM
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Originally Posted by GoodfellaFD3S
Seems like I'm late to this thread, and I didn't read all 5 pages (just this last one), but I'm assuming that those with these fuel pressure problems have recently installed a fresh fuel filter?
Umm. I have.
It's not dropping fuel pressure we are experiencing, its NO pressure when the fuel pickup is uncovered
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Old 02-28-07, 08:06 AM
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Originally Posted by gracer7-rx7
^maybe time for a new fuel pump?
Yeah, I thought that too, but everything's fine until about the 3/4- 1/2 full mark. I think I'd be having problems all the time if it were due to the pump or wiring or anything like that.

And yes, fuel filter has been replaced relatively recently. Ditto Crispy on that.
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Old 02-28-07, 08:39 AM
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Originally Posted by GoodfellaFD3S
but I'm assuming that those with these fuel pressure problems have recently installed a fresh fuel filter?
A clogged fuel filter would be an issue every single time the engine is under high load, not just during high g manuevers on less than half a tank of fuel. It's easy to tell the difference between starving the pickup and an actual fuel system problem.

64,000 mile fuel filter
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Old 02-28-07, 09:17 AM
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Lightbulb

Originally Posted by DamonB
A clogged fuel filter would be an issue every single time the engine is under high load, not just during high g manuevers on less than half a tank of fuel. It's easy to tell the difference between starving the pickup and an actual fuel system problem.

64,000 mile fuel filter
Like I said, I didn't read the thread. I just saw 'fuel issues'
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Old 03-01-07, 09:14 AM
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Here's a description of how to build a surge tank using a fuel filter. I saw this type mentioned earlier in the thread. This one isn't all that pretty but it can be built on your kitchen table with off the shelf parts. But who am I to talk about pretty????... I'm no craftsman. Luckily my homebuilt one is hidden under the rear of the car!

http://madscientistmatt.blogspot.com...-overkill.html
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Old 03-01-07, 11:25 AM
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Minor update: My friend is getting a scanned set of instructions sent from FEED. So as soon as I get it, I'll post it up to show how the part fits.
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