Blending fuel - snake oil or reasonable

Just tossing in one extra data point. My 11:1 compression Evo runs on E85. I carry enough to events so that I'm always able to buy from the same station that doesn't do winter/summer blends. They run the same mix year round.

Of course its a pain in the ass to do that, and with the MPGs I get with that car, I'd need to use a fuel truck as a tow rig for rally events. I suppose with a restrictor in place my MPGs might increase a bit, but the other major concern is that with a ~12 gallon tank, the car might not have the range to make the longer legs between fueling.

If you're able to, I'd think about getting it tuned using one of the national brands, and just make sure you're always grabbing from stations like that vs. the no-name store. Also, as others have said, the tuner makes all the difference. Make sure there are good fail-safes built into the tune so that if things start to go wonky, it'll pull back the power (cut timing? lower boost?) in an effort to save the motor.

Dave

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DaveK

If you're able to, I'd think about getting it tuned using one of the national brands, and just make sure you're always grabbing from stations like that vs. the no-name store.

Dave

That's exactly what I do (Sunoco) - but what you can't protect against (easily) is what if the fuel delivery guy puts the wrong gas in the ground tanks

Put it this way - Won Rally West Virginia with the fresh motor. No issues in 2 days of racing. 93 octane purchased just off of the highway at a Sunco outside of Winchester, VA.
Melted down one of the pistons 1.5mi into SS1 start at the next event. Fuel purchased just off of the interstate in PA.

I wish there was a simple fuel test kit that one could use that did on-the-fly octane verification of a given fuel sample. If there is one, I haven't seen it yet.

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EricW
That's exactly what I do (Sunoco) - but what you can't protect against (easily) is what if the fuel delivery guy puts the wrong gas in the ground tanks

Damn, that sucks.

What ECU are you running? What sort of fail-safe strategies are being used?

A hole in a piston is from running lean, isn't it? I had a friend who did that on two subie motors back-to-back because of an issue (aftermarket FPR & distribution block) that was causing one cyl to get less fuel than the others.

Dave

I seem to remember Mark Mager mixing something into his Premium pump gas when he drove the Legacy. For the STI, I dont recall anything but race fuel going into it.

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Welcome to the cult of JVL drink the koolaid or be banned.

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DaveK

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EricW
That's exactly what I do (Sunoco) - but what you can't protect against (easily) is what if the fuel delivery guy puts the wrong gas in the ground tanks

Damn, that sucks.

What ECU are you running? What sort of fail-safe strategies are being used?

A hole in a piston is from running lean, isn't it? I had a friend who did that on two subie motors back-to-back because of an issue (aftermarket FPR & distribution block) that was causing one cyl to get less fuel than the others.

Dave

A hole in a piston is from the crown getting reeeeeeally hot....
That can come from a number of different things: crown of piston thin, lean mix, detonation, wrong spark plug heat range (But while I've done that badly wrong, and the Pat Richard motor he brought for rebuild 100 years ago did it badly wrong ---out of 4 plugs, 2 had no side electrode at all, one had a blob of melted former side electrode, 1 was just roasted badly, at least 2 steps too hot--stock road car heat range in other words)---Eric has not only correct heat range, he has a very good plug , the same plug I use in YBG with 2 bar boost. It can also come from from a piston where the designer was getting cute--like Subie OEM pistons and most aftermarket "Shelf Stock" pistons with their bizarre straight sided square shaped dish that leaves less than 1mm material in the corners...

Lotta ways to make a hole.

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John Vanlandingham
Sleezattle, WA, USA

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Edited 1 time(s). Last edit at 12/17/2012 09:16PM by john vanlandingham.

Tuning is always key, no matter what the fuel. Been said here before but mixing works good. Typically I use it for a car that is probably fine on pump gas (and tuned for that) and you just want to add a bit of cheap insurance (really helps if you hit a condition you weren't able to tune for, such as radiator damage and car is running hot but you are still pushing hard, etc).

As has also been mentioned here, E85 is awesome fuel and I couldn't recommend it more. I have a flex fuel sensor in my Corolla which takes care of any different blends out there, or if I miscalculate my consumption and have to splash some pump gas in on a transit. Runs perfect on any combination from 0% ethanol to 100%.

Just remember E85 is hygroscopic so don't leave it sitting in the rally car for any length of time or you might regret it. Fuel systems can and will rust up and it has the potential to make a huge mess. The Internet will claim it doesn't happen and I am sure there are a few examples out there to prove that theory but it is an expensive gamble to take if it wasn't true on your car.

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John Reed
John Reed Racing
www.johnreedracing.com
johnreedracing@gmail.com

Back in 2008 we had the n/a Fucus motor rebuilt with Ford Racing this-and-that and then tuned for race gas. Being a small, amateur team with a small, amateur SUV-n-trailer I didn't want the logistics of hauling around race gas. So we blend 93 (or best we can get) with Torco Accelerator to approximate 100. It's a whole lot easier (and cheaper, actually) than race gas. Our motor has been awfully happy for 5 years and 30+ events.

YMMV

Simon

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Simon Wright
Owner/Driver USUK Racing - Home of the USUK Racing LED Light Bars!

North America Rally Map

you need a less agressive tune. i tuned the mazda on a laptop while i had dad pull hills at rpm intervals. just made sure the AFR was happy, did not use EGT. and added a bit of fuel at 0% throttle, so when you hit the pedal again there is less hesitation with turbo. no motor brake down hill big deal... tuned on highest mobil gas, might have been 91.

do not use AV gas. that stuff is horrid.

Brian, the AFR doesn't change with fuel quality or octane. The car WAS rock solid on the tune - it just melted down because of bad gas and no knock sensing enabled.

Had the car been tuned on 91 and accidentally put in 87, it would have done the same thing... and had solid AFRs.

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EricW

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Dazed_Driver
Its most likely not worth it, especially mixing with pump gas.

You'd need to have the same gas from the same batch of the same blend to have an "accurate" recreation.

Let me be clear - I'm saying that I'm proposing tune for the WORST (read: NO mixing) and then run a mix of the pump+race. From some reading, unleaded + leaded is generally a bad idea, but unleaded + unleaded is generally not toooo bad?

I'm not looking for accurate - I'm just looking for something that's some generally measurable amount that's better than worst-case (read: pump gas) that's already been tuned for. I know I won't get any more performance gains, but I'm looking for the insurance of the higher octane to help provide some mechanism of reducing potential detonation.

Make sense?

video: ?t=59m13s

She goes both ways.

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Kirk Coughlin
Woodbury, MN and River Falls, WI

Quemadmodum gladius neminem occidit, occidentis telum est.

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EricW
Put it this way - Won Rally West Virginia with the fresh motor. No issues in 2 days of racing. 93 octane purchased just off of the highway at a Sunco outside of Winchester, VA.
Melted down one of the pistons 1.5mi into SS1 start at the next event. Fuel purchased just off of the interstate in PA.

Just curious, Eric, did you test the PA fuel and find it was below octane rating? Also curious if there was anything significantly different about the 2nd event in terms of air temp and humidity, and was there any chance that the engine sucked in a bit of water or did a bunch of oil suddenly get in there? Could a sensor or control have gone wrong? With that rapid a melt, it sounds to me like something was steady wrong, like timing waay advanced or a fuel restriction. Was the knock sensor disconnected or is there none? How did the piston melt? Any pix? Any AFR indicator on the car?

FYI, I run the knock sensor in the Starion; it has worked once or twice when I set boost a bit too hard. The Starion strategy is rather harsh: fuel cut off! It was a pretty abrupt indicator, but glad it was there.

BTW we use the name brand strategy: Sunoco #1 and Shell #2.

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starion887

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EricW
Put it this way - Won Rally West Virginia with the fresh motor. No issues in 2 days of racing. 93 octane purchased just off of the highway at a Sunco outside of Winchester, VA.
Melted down one of the pistons 1.5mi into SS1 start at the next event. Fuel purchased just off of the interstate in PA.

Just curious, Eric, did you test the PA fuel and find it was below octane rating? Also curious if there was anything significantly different about the 2nd event in terms of air temp and humidity, and was there any chance that the engine sucked in a bit of water or did a bunch of oil suddenly get in there? Could a sensor or control have gone wrong? With that rapid a melt, it sounds to me like something was steady wrong, like timing waay advanced or a fuel restriction. Was the knock sensor disconnected or is there none? How did the piston melt? Any pix? Any AFR indicator on the car?

FYI, I run the knock sensor in the Starion; it has worked once or twice when I set boost a bit too hard. The Starion strategy is rather harsh: fuel cut off! It was a pretty abrupt indicator, but glad it was there.

BTW we use the name brand strategy: Sunoco #1 and Shell #2.

No - no easy way to test the octane. I looked at portable kits and they are $$$. Cheaper than another motor, but still not something that I'd be willing to whip out my credit card for at the drop of a hat.

RWV was warmer and more humid. Should have been on the worse end of the fuel burn than the BRS weather of cool and dry.

Fuel injectors were verified 100% functional and no issues with the fueling system that we could find. I'm still waiting to get the logs off the ECU which did capture AFR.

What kind of pics do you want? The piston completely melted and the slag ruining the shortblock?

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EricW
it just melted down because of bad gas

if you did not have the gas tested i would give up on this excuse and keep looking.

check ring gap on other pistons (blow by) ?

our mazda had been tuned by a super elite shop where all the employees were extremely rad. the car ran horrid when we first got it, would not idle and would pop n buck intermittently. the "awesome" engine had super neato pistons and rods stonger than popeye. that motor melted a piston. we put a new motor in and i checked the ECU with laptop.. the TDC was absolutly wrong in the ECU. it was so far off i have no idea how that car ran in the first place. this did lead to some testing of AV Gas in the mazda, under the strong encouragement of my father... that stuff burns too hot and was a waste of time.

i remember when Allen's Subie ran out of fuel near a start control. he had to borrow a local resident's old lawnmower gas from the shed... he finished.

I am 100% confident of bad gas. Car was PERFECT at RWV - all ECU logs showed no issues. If it was knocking at RWV, it would have melted down there - especially considering it was a two day event with huge elevation changes, lots of wide open throttle, and pegged boost.

Ring gap and everything was fine on teardown. No major blowby issues (catch cans were catching some mild fuel and oil mix depending on which can, but it was nothing dramatic. No increase or decrease in blowby after engine build and through RWV).

It is absolutely possible to finish with bad gas... but not if you're wide open throttle and you're keeping it out of the boost.

Since everyone is curious for for photos of the damage:




The heads sustained NO damage. Just engine block and melted piston.

I don't mean to argue and what I say depends on the condition of the other pistons, but I've seen a partially-clogged injector do exactly that to a 4G63. The gas, in that case, was fine.

As to the original question: we were mixing 4 gal of Sunoco 93.5 with 1 gal of toluene to a water-injected 4G63 with a FP big28. This was back before e85 became the rage in the DSM/Evo world.



Edited 1 time(s). Last edit at 01/15/2013 09:45AM by Iowa999.