Oil or fuel starvation?

[Digitalwave]

Car: M20 e/i hybrid 2.8 stroker, stock oil pan, no baffle or scraper, stock fuel pump in stock tank.

After a long left hander at PBIR (pic below) I am hitting some sort of cutout towards the top of 3rd gear (around 5,500 rpm) after exiting the corner. The car will have already straightened out when the cut occurs, but it's a pretty long corner and I'm accelerating out from the apex.

It's not happening elsewhere on the track; I can go to redline fine coming out of right handers.

Any thoughts would be appreciated. I'd love to not have to baby it coming out of that corner.

It's happening on the straight in between turns 4 and 5 on this diagram.

[e30_302]

Fuel

[gte175x]

oil would not cause the motor to stall or cut out / unless you were seizing it...fuel would be my bet

[vpilarrt]

Hmm, I've only had fuel pickup issues on long right handers. The fuel pump is in the right side of the gas tank and during right handers the fuel migrates over to the left tank (or at least away from the pickup). I solved it in my track car by moving the M20 fuel pump hanger to the left side of the tank with a low pressure pump from a carbureted car (I used one from a '88 Honda Accord) and putting a fuel hanger from a '91 318is in the right hand tank with the OEM high pressure pump. Run a fuel line from the output of the left tank hanger to the return port on the right tank hanger (the 318is hanger has 2 ports). You'll have to run power to the left tank pump, I wired a dash switch in so I could turn on the left tank pump when I get below half a tank and start to get cutout. This pumps extra fuel from the left tank to the right, more than the OEM in-tank siphon can do.

[Digitalwave]

Right, I read about fuel starvation being most common on right hand turns. It does feel like a fuel cutout though.

[dude8383]

Yeh, thats starvation, super bad for the motor!

How much fuel did you have in the tank? A surge tank will definitely help alleviate or even eliminate your starvation issues.

[Digitalwave]

It was occurring when below half a tank, but I believe it was still happening after I refueled to above half a tank in the later sessions. I'll have to look at my video footage.

Edit: my car is an 07/87 build, and has the smaller fuel tank. It probably has the 2 fuel pump setup, right? I might need to start by replacing both of those. It would be cool if that fixed my phantom CEL at high RPM (maybe it's running lean up top). I always just attributed that to the Miller MAF setup.

[Axxe]

In tank pump might be on the fritz. A surge setup is easy to do on an early model if you are track dedicated and can have fuel in the trunk. Either way I would start by pulling the in tank pump and seeing what you find, could be a clogged sock, or a bad pump. I use a generic in tank lift pump, I think it lists as an 89 Ford Thunderbird or something similar.

[TobyB]

Hmm, I've only had fuel pickup issues on long right handers.

Yeah, agreed- that should happen in 5, not in 4...

Easy answer- fuel pressure gauge. a tee, a cheap oil pressure gauge, some fuel tubing,
tie- wrap it to a wiper, off you go.

Crap in the tank? Flapper door problems? Loose battery flopping around in the trunk?
Things like this start to be a real pain to troublesoot...

t

[smellthebeans]

Yeah, agreed- that should happen in 5, not in 4...

Easy answer- fuel pressure gauge. a tee, a cheap oil pressure gauge, some fuel tubing,
tie- wrap it to a wiper, off you go.

Crap in the tank? Flapper door problems? Loose battery flopping around in the trunk?
Things like this start to be a real pain to troublesoot...

t

Sounds like typical low fuel issues that occur as you approach 1/2 a tank. Typically occurs during longer right handers but I have also experienced it in left and right highly technical combinations. Bottom line is fuel pool away from the pump pick up causing the starvation.

Holley Hydramat is a possible solution but I dont think they sell fittings for the BMW E30 pumps.