Fuel Sloshing
 

I recently did my first track day since going turbo and first time on NT-01's (from Azinis). I exprienced fuel starvation around the same turn every time I ran with the tank lower than 1/2 tank. Fill it up and no issues. I never had this problem in the past, but never ran tires this sticky.

Is it normal to experience fuel starvation at these grip levels?

No. Miatas will run right down to E without issue (even on Hoosiers). Better check that your fuel pickup sock is in good condition.

I replaced the fuel pump/sock with the turbo install. I might have boogered something up. Worth checking I guess.

Definitely not normal, Miatas will run on fumes with Hoohoos and aero.

Did you use a stock fuel stock? Or a walbro sock?

either wrong sock, or incorrectly installed assembly/pump, or something else.

Or maybe it's just not actually true that all Miatas will run on fumes on the track. Mine won't, Ed's won't, several others won't. Mine has no broken baffles and a brand-new factory sock and still starves powering out of left handers when it gets down to 4-5 gallons left. A suggestion has been made that it might be the removal of the NB in-tank regulator that hurts it, due to the return pipe dumping the fuel halfway down in the tank. I stuck a camera in there and recorded it (not while moving) and it doesn't really appear to be that big of a deal. So I dunno. Rallas appears to have an NA, so presumably he hasn't removed an in-tank regulator.

One thought is that the "will run on fumes" allegation is (AFAICT) primarily based on endurance racing Miatas, particularly various cars owned/run by Emilio. Note that these are all naturally aspirated cars which suck down a whole lot less fuel per second than a turbo car does. I have read that the reason you want a factory fuel sock is that it lets fuel into the sock fairly easily, but prevents it from draining out quickly. In effect it's acting like a small surge tank. If so, then it's possible that this small reservoir of fuel is enough for a 150-180 rwhp to power out of a corner, but not enough for a 300+ rwhp car to do the same.

For my car I've basically just been avoiding running it low by filling up every couple sessions.

--Ian

If I don't start a track session with at least a quarter tank, I will experience a fuel cut kind of symptom during a long left-hander. Maybe it's an Emerald Mica '99 thing.

Happens on my 91 on the street, thought I might have mounted the pump and therefore the sock too far up. But, last time I checked it was firmly against the bottom of the stock NA lower rubber grommet and foot. I was planning on removing the rubber grommet next.

My tank does not have tall baffles, its a small tray with maybe half inch tall walls. It would not hold much fuel where it needs to be. Can't find a good picture online, don't think my tank is modded or busted. Can't see any broken spot welds...

I replaced the entire fuel system and lines, the filter, the sock twice...

Hope my new one doesn't have this problem.

Edit: Here's what the inside of my tank looks like.

http://i.ebayimg.com/images/g/DGMAAO...Cu/s-l1600.jpg

Is the sock supposed to be under that hole???

I only had the issue on turn one at CMP which is a left hander, not real long left hander though. No issues on any of the other turns.

I replaced it with an aftermarket sock that that looked identical to the original one removed with the original OEM pump, nothing special.

Which turn at CMP? I have never had any fueling issues at CMP with my turbo 94. Had it down to less then a quarter of a tank many times.

Turn1

Does anyone have the part number for a factory fuel pump sock/strainer? I cant find any factory socks online.

I've run/raced (and regularly for weight savings) down to the E many times racing. Never had fuel issues, ever. Most races I start at 1/4 to 1/3 full.

Stock fuel pump, regulator everything. 1600 turbo with 260 hp atw and now with the 1800 at 320+ hp atw (though we did change the pump to the DW one at the engine upgrade).

edit to say: No jinxes.

Yeah, I've put 12 gallons in an NA Miata at the track. Bone stock, never opened gas tank.

A stock NA6 tank setup will fuel starve with ~10oz left in the tank

It looks like that is a NB part number. Does the NB sock fit NA pumps? I have a Bosh factory replacement pump in my 91.

Thanks! That's much cheaper too! Is that the factory part? Everyone seems to think that the factory sock/strainer retains fuel better than aftermarket socks/strainers.

I believe it is factory sized. And it's a Denso part, so likely stock.

Someone else may know better though.

The factory NA part number is B61P-13-ZE1, found one on ebay for $26. Looks like the Denso part number is 952-0001.

Purchased this and installed last night. I have not tested it on the track yet, but the Denso part does fit. The sock part does seem to have more "structure" inside so that it can't be squeezed flat like the previous sock that came with my DW200 pump. It feels similar to the OEM sock that was on the car. That extra structure could make the difference, or maybe it's the sock material is better at trapping the fuel. If this doesn't work i guess I'm looking at a surge tank or one of the Holley HydraMats.

I was also having some long left-hand turn fuel starvation issues. 99 with LS1 swap. Baffle is fine, fuel tank is clean. The sock I removed was in fine condition by the looks of it. The tank was half full when I was having this problem.

Holley hydramat is not cheap but works amazingly well. I'm a believer. I had to find a solution on the exocet because of the shitty fuel tank angle required and since installing it I have had zero issues on a turbo car. The larger magnet mount kit they offer works perfectly in the miata fuel tank.

Curious which Hydramat you used as I'd think the tank baffle might get in the way. I'm assuming you used some sort of adapter kit to transition from the pump inlet (not sure what size that is) via some fuel-compatible hose to the AN fitting on the hydramat using a hose barb connection. Their site sells some fittings and such and hose, but it's the connection to the pump inlet I'm not sure about.

Thanks

Hydramat is a great solution to a problem we don't have

I'm using a Walbro 190LPH-HP with a Radium adapter on the pump and the 15" x 8" hydramat cross in a 99 miata fuel tank. I had fuel starvation issues at anything under 1/4 tank even in a straight line because of the exocet tank mounting angle. But after switching to the setup below I can go down to almost nothing in the tank.

https://www.holley.com/products/fuel...s/parts/16-101
Walbro E85 Fuel Pump Outlet Adapter
Submersible PTFE Fuel Tubing
https://www.holley.com/products/fuel...s/parts/16-204

It looks like Radium changed the adapter, pretty sure mine was a barb and not an AN fitting. You could convert the hydramat NPT to a barb and the Radium fitting to a barb and just run their submersible hose or go AN fittings on both. My concern with an AN line would be that it might not be flexible enough. It is a tight space and ideally you would use the Radium PTFE flexible hose (link above) with barbs. The hose does need to be a little long as you need space to be able to mount the hydramat and get it aligned while having the pump assembly tilted to the side.

The cross lets you get some side coverage for slosh and nestles down into the factory pickup spot beside the baffle perfectly. I oriented it so the short ends point outwards and the long ends run front to rear. I put the long rear part under the rear baffle and it fits perfectly. The bigger magnet mounts that holley sells are strong as hell and it won't move at all.

I changed to the factory sock last nigh. Just comparing the size and angle of the Denso sock to the aftermarket one it looks like the Denso sock is bigger and will reach deeper in the tank.
https://cimg0.ibsrv.net/gimg/www.mia...e1dafbc56d.jpg
https://cimg4.ibsrv.net/gimg/www.mia...600d9c1e5d.jpg
https://cimg7.ibsrv.net/gimg/www.mia...2e03704f7e.jpg

That brown one is the aftermarket sock? It's the completely wrong shape, which would make a big difference in what tank level it began to starve at... The Denso one (assuming that's the clean white new one) is similar shape/size as factory.

Agreed. Did the same back in September, the Denso sock also seems to have more internal structure or volume, so I hope it works out. Haven't been on track to test it yet.

https://cimg3.ibsrv.net/gimg/www.mia...f62287ddac.jpg

I experienced fuel starvation with my 90 SM at Sebring turn 1 this past november. Once it dropped below 1/8th tank, it would cut off mid corner and wouldn't kick back on until almost turn 3.... lol

I won't be starting a race with less than 1/2 tank again.....

I have run the car down to fumes during a 90 min enduro at Daytona in May of last year, so I was sorta surprised when this happened during my Sebring race

Your fuel sock and you
 

As Ryan pointed out, the brown sock will not work. Despite it's simple appearance, the OEM tank, sock, pickup and baffles work extremely well. Easily feeding an engine at sustained 1.5g down to about 1 gallon. If you have a problem with fuel starvation with anything more than 2 gallons in the tank, you have a pinhole in the sock. This is not conjecture, guess or something we read on the interweb. You may not even be able to find the pinhole, but trust us, it's there.

You may also notice, upon dismantling an OEM pump/sock where there are slight wear marks in the baffle plate inside the tank. That is where the sock rests. That location is Critical to proper scavenging. Change the pump or sock so the sock isn't resting in that part of the baffle and the carefully engineered scavenging system will not work. Walbro and Deatchworks install kits put the replacement socks in the right spot. But also look at your fuel pump install. If the assembly is significantly shorter or longer than OEM, the sock will either be crimped or not touching the baffle in the right spot.

Using E85 will cause the socks to wear. A car run on gas might have it sock last forever if not disturbed. That same car switched to E85 late in life will usually kill the sock in a year or so. We usually switch both fuel filter and sock after the first track weekend on any new builds after switching to E85.
On E85, the sock becomes a wear item and should be swapped at least every two years. Ditto fuel filters.

It's not rocket science