Fuel Starvation?
 

This weekend I was running Streets of Willow, counter clockwise. I started the day with a full tank of fuel. The last session of the day my car started acting funny. Going up the hill through the Chicane to the bowl I could run through the gears to 7500 no problem. But coming down hill turning left in the last two corners before the main straight my engine would just kind of go flat and not rev above 6000 rpm on the straight. I was down to a half a tank of fuel at this point. Do you think this could be a fuel sloshing problem from the half full tank and left hand turns?

Depends where the pickup strainer is.

You can definitely starve on 1/2 tank, but shouldn't if the car is NA. It's a pretty big pop / immediate loss of power if you run the rails dry.

The 'won't rev past 6000 on the straight ' doesn't sound like a fuel starvation problem. In my experience a starvation occurs mid corner and goes away fairly soon; by corner exit depending on length of corner

Yea that sounds odd. I'll start to lose FP mid-corner and the power level / consumption sometimes won't let it recover and I'll end up starving at the end of a straight.

Supercharged on e-85

I was fuel starving my car N/A on E85 by 7/8th of a tank on a long, high-g left hander before going with a surge tank. It would starve right after corner exit and would last two or three seconds.

That sounds like what I was experiencing.

Do you have a data log with RPM, speed and throttle position?

No.

Are you running with stability or traction control on?

NO

I was able to do some test pulls today. rev to 7500, up to 120 mph with no trouble, engine pulled hard all the way and wide band O2 never leaned out. So I'm guessing it was just the half full tank and the track configuration that was causing my problems.

you def had fuel starvation at half tank with your setup for sure. welcome to the club. gonna have to keep full tank or get surge tank setup. couldn't run Atlanta motorsports park n/a with half a tank without starving

How many lateral Gs and for how long do you guys sustain it to get fuel starvation? I havent hit it myself but I run in fairly small tracks, no long sweepers, just wondering for the future (there is one big track with a long sweeper in my calendar this year).

Yup, full tank from now on.

I can't answer your question directly but I have seen over 1 G at different tracks.

Maybe its something to do with the banking in the corner? I see between 1.1 and 1.4g on every corner, and just last week I ran until the car had almost no fuel in it (3 laps past the fuel light) and no issues. So it seems the pickup for the fuel pump is enough for NA on normal gas but FI or E85 or both seem to have this issue. I guess you would have no option but to run a surge tank. Its a close to 100lbs of fuel you need to haul around otherwise :(

You are experiencing fuel starvation. This is a well known issue for left hand turns in boosted cars and there are a few threads with more details and solutions.

I have the Vortech supercharger and have the same issue on turn 3 at Palmer Motorsports Park. It is a sweeping left hander which I am going through at full throttle. If I am below 3/4 tank I see my revs start to drop at full throttle and my AFR goes full lean. This only started happening after I switched to 17x9 with 245 Direzzas and swapped out my sway bars. With these mods our cars are pulling significantly more lateral g's than the fuel tank was designed for.

The only solution I have heard of that has been documented to work reliably is a surge tank in the engine bay. This is a cumbersome and expensive modification that requires an additional (noisy) fuel pump and a tank that is vented to atmosphere (get used to smelling gasoline). And of course there is a greatly increased chance of fire when adding fuel lines in the engine bay.

I have heard mention of having a Holley Hydramat installed in the fuel tank, or an installing an additional in-tank floating fuel pump but have not seen anyone who has done either of these on the forum yet.

Until then I suggest you lift or risk destroying your engine.

Thank you, now that I know what's happening I'll run a full tank and lift if necessary.

What sway bars did you go to and did they reduce your lap times?
And if I may ask, what spring rates are you using.

Hotchkis front and Rear and yes, the sway bars definitely reduced body roll and gave me more grip in corners. Can't say exactly how much they reduced my lap times but with the front at stiff and the rear at medium soft plus new wheels and tires I was going through corners about 5-10mph faster than I ever had before. I was running RCE yellows which are 4.5k front and rear and Bilstein B8s, so not too aggressive.

I've since put the sways back on the softest setting to try to alleviate the fueling issue but still if I'm below half tank I get starvation in that one turn at full throttle so now I just ease off early and brake very late into the next corner.

I would assume that if you bias damping settings/tire pressure on one side of the car or go with softer sways to increase body roll it might make a difference but at the expense of speed.

@CSG Mike would know more about the issue and talked about it in the thread below

http://www.ft86club.com/forums/showthread.php?t=33991

Thanks for the info. I'll read the thread you posted for me. Thank you.

Can't say for sure but I would expect that anyone experiencing this issue is sustaining at least 1.1 lateral g's. On turn 3 at Palmer I'm probably sustaining that level of grip for 3-5 seconds.

245 or wider, 200TW or stickier, boost, a stiff suspension, and downforce will get you there. This chassis is incredibly well balanced.

This looks like it would help: http://www.radiumauto.com/Fuel-Pump-...T86-P1142.aspx

Definitely not a guarantee against starvation but looks like it would have much better pickup than the oem or a drop in pump.

This plus a surge tank would be the full fix for a high horsepower track monster.

Thank you, I'll look into that.

Here's the corner where I had the problem. Right after I hit the straight you can hear the engine quit revving and me short shifting.
https://www.facebook.com/steve.joneli?fref=ts

Moto-East has a plug and play surge kit that is the best option on the market right now in my opinion.

http://www.ft86club.com/forums/showthread.php?t=105934

Thank you, Ill look into it.

PM me if you want details on my fuel system and how to solve this. Surge tank isn't the solution.

Will do, thank you.

If surge tank isn't the solution, it would be really helpful to be shared with the community as that is the only viable solution I (and many others) are aware of.

Yes, however, I don't have time to do a full write up at the moment, so I would prefer to discuss it in private to avoid any group confusion. The experience and education level on forums vary so much, I don't want to be responsible for someone making a mistake while trying to do a massive fuel system conversion without a proper write-up.

Fair enough. I should have said the surge tank is the only plug and play type solution I am aware of. Certainly massive changes can be made.

So has anyone thought about installing some sort of drop in baffle balls?

Essentially plastic whiffle balls that would not displace much volume but would get jammed up in the middle of the saddle during high g corners and essentially create a barrier to the fuel sloshing to the other side.

It seems like this is used in other applications successfully. Also it would be fairly simple to do as you would just open the fuel tank and drop them in rather than a complicated surge system/fuel cell and there's no risk of deterioration over time like there is with foam.



Something like this but the size of ping pong balls:

http://www.gemplers.com/product/WEB218017/Baffle-Balls

or this in the golf ball or baseball size

http://shop.ctstore.com/store/pc/vie...?idCategory=70

Edit:

So apparently wiffle ball plastic will dissolve in gasoline over time, but the tank itself is made of high density polyethylene (hdpe) so I figure it must be safe to use HDPE baffling. My idea is to get some quality HDPE hollow balls and drill some holes in them. Any thoughts?

http://cicball.thomasnet.com/viewite...e-hollow-balls

Edit 2:

I found a patent filed by Goodyear in 1965 for this exact idea. https://www.google.com/patents/US3349953

We install a lift pump in place of the siphon tube in the passenger side tank which helps a ton. Eventually even that wouldn't cure it but our car pulls 2G so it may work for most people.

What happens on the boosted car is that the bigger fuel pump or higher fuel demands can empty the oem surge faster than it can recover. It doesn't recover fast enough on the track due to fuel sloshing so your siphon system isn't working 100% of the time.

It is hard to say but you need to go to Auto Machnique. So, He can identify the problem and solve it.