Fuel starvation in left-handers?
 

So I ran my car at Laguna Seca today, with GGLC. It's the first time I've run it with the CAN bus megasquirt input to my DL1 data logger, and I noticed some worrying lean spots in the data. Lots of rambling analysis in my build thread (see sig) but right now it's looking like the car is having trouble with fuel starvation when powering out of fast left-handers, mainly 5, 6, and 9. I started the session with half a tank, it was down to about 1/4 by the end.

Anyone seen this? Any suggestions on how to fix it other than filling the car up every session?

Datalog trace:

http://www.codrus.com/miata/fm2r/Jul...ror-label.png?

(yes, slow laps -- I was stuck behind a Porsche :-) )

--Ian

Put your OEM fuel sock back in

It is in, it's on the walbro. Well, unless it fell off and is floating around in the tank -- haven't checked that yet.

--Ian

I'm having the same problem and have replaced the sock twice now, as soon as I get below 1/4 tank I have problems. Replacing the sock and fuel pump helped a little, but it's still not 100%

I'm wondering if I didn't mount the walbro too far up on the pump assembly.

I'm not even on good tires, or the track...

There's a factory bracket at the bottom that pump goes on, so I'm not sure it's possible to get it too high.

http://www.codrus.com/miata/fm2r/bfk05.jpg?

--Ian

Next step would be to confirm that everything is in place inside the tank. Internal baffle may have come loose, fuel sock may be clogged or loose, pump may have come loose from the hangar.

I was at Sonoma on Sunday and nearly ran Acamas out of gas after getting greedy and doing ~4 laps with the needle below E. As it turns out, turbo cars won't do four 25-minute sessions on the same tank of gas. :) Acamas has a DW200 in the tank on a stock sock right now. If you're starving for gas with 1/4 tank in the car, something is loose/broken/wrong.

That's slightly different than my 1.6 setup, but it's basically the same. I've got a little bracket that used to pinch the stock pump into the hardline.

I never checked to see if the walbro had a more recessed intake nozzle than the stock pump, but I do remember fighting with the lower rubber bushing a bit. My plan now was to shim the lower bracket 1/8-1/4" lower using washers and a longer screw.

http://turbomirage.com/miata/2007_10/IMG_3606.jpg?

I think the end all solution would be a holly hydramat, but those things are expensive...

https://www.miataturbo.net/race-prep...y-users-88523/

deezums: What symptoms are you seeing on yours? Is it noticably stumbling or losing power? Mine appears to run just fine, it's only by analyzing the data logs that I can see it going lean.

I'll be opening up the tank to take a look this weekend.

--Ian

I really only take a few corners near my old shop hard, and there's two lefts that will fuel cut seemingly every time. It's a hard noticeable fuel cut, like hitting a brick wall.

I can make it do it on command at 1/4 tank by trying to do donuts to the left, if I go to the right no problems. Figured that out when I was trying to kill old tires for fun.

I guess the only other thing I really see is the your "return" line is rather high up off the bottom of the tank comparatively, do you think it would benefit it at all to extend it to the sock, or right underneath the sock?

Yeah, it's possible that simply removing the in-tank regulator results in a lot of splashing that's driving fuel away from the pickup sock, I need to look into that.

--Ian

Interesting. @turbofan had the same issue. With the regulator disconnected just like yours.

Think he swapped in a new sock and fixed it.

I don't have the data to back it up though, and my car would straight up 100% lose power on left turns, then return a second or so after exiting the corner.

But yes, a new OEM sock fixed it. Old one was crusty. Certainly can't hurt.

Had the same issue at MRLS, under 1/2 tank on lefties and it was dead for a 2 count till the car straightened out. Car is parked so never did fix it, I'll be trying the new sock since the one in the tank is original, prolly fucked.

So we played with it a bit this evening. Disconnected the filler pipe, stuck an inspection camera into the tank, and primed the car to see how much splashing was going on. This is with the car parked, not even running, just turning the key on/off to prime the pump 3 times. Since the injectors are all closed, this should be as high a flow rate as the return line ever sees -- it's a lot, but the splashing isn't all that bad. There's about 3 gallons in the tank at this point. The camera is sideways because, well, that's how it ended up. Aiming these things is hard. :)



--Ian

I have seen fuel starve when an otherwise healthy looking fuel sock had a single tiny hole in it. If the system was working fine and suddenly develops a starve, it has always been the sock in my experience. The socks that ship with Walbro kits work perfectly as OEM replacements.
The sock is a wear item BTW. Keep a new one in your track spares.

OK.

I put a new OEM sock in yesterday -- hopefully this will address the issue.

http://www.codrus.com/miata/fm2r/fuel-sock-compare.jpg?

thanks,
--Ian

I did a hydramat install on my V8 exocet which goes faster, sucks more fuel, and corners harder then any 4cyl miata. It fixed the fuel starvation issue. Highly recommend. It requires you to switch to an in-line style pump in the tank, so that you can hook to the hydramat pickup. Here's the photo album.

https://www.facebook.com/media/set/?...1&l=83a4a6e8f9