F82 fuel starvation on track

[r4dr]

I don't see many people posting here, but I'd rather try here before I go into the shithole that is F80Post. Background: F82 M4 Competition, Ohlins R&T coilovers, 18" EC-7s wearing 275/305 NT01 tires. It's not my car but I've been dual driving it lately and pushing it harder than it's been pushed before, hence this post.

I've been running into severe fuel starvation issues, specifically on an off-camber right hander. This kind of makes sense to me, since the fuel pickup is on the right side I believe. Basically anytime I start with the needle around 1/2 tank or lower, I can't make it through a 20 minute session without going into limp mode. Which then involves me throwing the hazards on and puttering off the track while praying no one hits me.

Given I use more than 1/3 of a tank (indicated at least) per 20 minute session, and it's being dual driven... even putting 5 gallons in after each double stint resulted in limp mode in the 3rd double stint of the day. Has anyone seen this issue and found a solution? I can't find any kits online like for the E36 and E46 where they put another fuel pump in the other side of the tank.

[IamFODI]

Free bump for an interesting question!

[r4dr]

Forgot I posted this here. We discussed this a bit on the F80 forums. No fix is known, just gotta fill it up... given that a 20 minute session uses almost half a tank, it's rough. This is only on NT01s too.

[IamFODI]

Forgot I posted this here. We discussed this a bit on the F80 forums. No fix is known, just gotta fill it up... given that a 20 minute session uses almost half a tank, it's rough. This is only on NT01s too.

That sucks. Seems like an annoying issue to have, not to mention a weird void in the aftermarket.

What do the track-only cars do? Fully custom or race-specific tank/pump setups?

[r4dr]

That sucks. Seems like an annoying issue to have, not to mention a weird void in the aftermarket.

What do the track-only cars do? Fully custom or race-specific tank/pump setups?

BimmerWorld came up with the some of the solutions for the E36 and E46 cars back in the day, but the F82 GT4 cars they're campaigning don't have this problem because they have fuel cells vs. the regular street M4s. They admitted over the phone they hadn't felt motivated to look into solutions because of this... lol.

I don't know of many track-only F80 cars, but that may change. If someone comes up with a solution (shouldn't be too hard, just add another fuel pump like the other BW kits do) they will definitely have a market.

[WestBankM4]

I had dual fuel pumps on my E36 M3 and they were easy enough to install and wire up. I don't see the issue with doing the same for our F8x chassis, I haven't experienced fuel starvation on the track though, I know the oil pan has baffles to trap oil in specific parts of the pan on hard cornering but I didn't experience fuel starvation, I had about 1/4 tank left at one point. Maybe I wasn't pushing it as hard as you but I was giving it all she had.

Interesting to see if Turner or the link come out with something for the F8x chassis in the future, I'd definitely get them just for peace of mind.

[SYT_Shadow]

It is a really annoying issue. They had this problem in the E46 back in the stone age, then they fixed it perfectly in the E9X gen to the point you can track at zero without issues, then in the F8X they screwed it up again.

It is ridiculous. It's like the F8X having subframe issues.

Anyway, it happens anytime you have less than half a tank if you're driving hard enough. Even a hair less than half a tank and it can fuel starve to the point it shuts down.

I double-duty the CS and I put a 5 gal jug in, which is just enough to prevent it when running 25 or 30 min sessions. If this isn't working for you you'll need to find a way to feed it 7 gal or whatever it takes so it is happy

There will be a solution for this, just not yet. One guy fixed it but with $1500 of parts.

[r4dr]

I'd rather fix this than the E46 subframes though!

[SYT_Shadow]

I'd rather fix this than the E46 subframes though!

For sure! No doubt about it!

[Slonik]

f8x has built-in fuel filter (into the fuel pump cover), so fuel pump performance drops a dramatically, when filter goes dirty.
we have this issue here in russia a lot more often, due to a worse fuel quality.
so, our local f8x guys, who have a lot of track time during season, change fuel pump (which goes with this cover and built-in filter in one cat number) every year.

some another, more smart way. if you check in the bmw cat, there are an option, when you have external fuel filter location instead of internal in the cover.
so, not to change fuel pump every time, you can make a swap to the external filter config one time, and then change filters only.
i've checked it and this external filter widely common and available for many other bmw models in local shops, and cost about 30-40$ per item. so you only need to order and wait one time all this parts, like different fuel pump, some fuel lines (cause external filter locates under the body) etc, and then changing this filter will be easy enough.

if i remember correct, all this parts for the swap cost about 1.5-2x of usual fuel pump cost, so not so huge difference, compared to every year change.




barrel on the cover - built-in filter

[bigjae46]

Earlier 3 series were saddle tanks with a siphon pump on the left side. For fueling issues, you can add a pump on the left side with some minor modifications.

Surprised the F8X doesn't have something similar on the left side of the tank. There looks like some sort of plug on the left side. Possible to replace with another fuel pump assembly and move the fuel back over the right side? Only other option I can think of is a surge tank but not sure if that's a great idea for a daily driver.

[TeddybearCup]

A surge tank is what a ton of track cars run (if not blocking off half the OEM fuel tank or installing an aftermarket fuel cell entirely). In tank setups are my favorite due, but have had a few cars with surge tanks outside the fuel tank. Both allow me to run to empty.

A second pickup seems to also work as well, and seems more popular for BMWs, as far as kits go.

External surge tank setups typically run well under $1000, but could require some understanding on how to plumb return lines, making sure you set fuel pressure correctly depending on the car, and secure mounting, outside the cabin.

[IamFODI]

Still so puzzling to me that this is a thing. Fuel starvation below 1/2 tank seems like a weird problem for an M3 to have.

Based on Slonik's feedback above, maybe BMW M just never tested it with less-than-excellent quality fuel, so they never saw the fuel filter issue?

[TeddybearCup]

Still so puzzling to me that this is a thing. Fuel starvation below 1/2 tank seems like a weird problem for an M3 to have.

I think it's a financially driven thing: How many buyers will be swayed by whether a car's fuel tank or pump setup can resist fuel starving? Really, just the ones that seriously track their cars. But of that, probably very few would change their car buying choice as a result. Meanwhile, they can save some money on every single car sold without spending on baffling or more complex pump setups.

I've come to expect starvation (and needing to address it) as a given issue with any car I track, and set myself up for a pleasant surprise on the off-chance the car doesn't starve prematurely.

[bigjae46]

I think it's a financially driven thing

I 100% agree. I think with the F8X and later model M cars they are less track focused and more 0-60 and 1/4 mile time focused. BMW has gutted their factory teams - not even Formula E anymore. I think BMW was correct in their direction because you don't see many F8X and fewer G8X cars on track. Haven't seen a F9X M5 or M8 on track yet.

Modern M cars (turbo'd) are really nice cars with cool looking tech and go really fast.