Bronco bustin' -- what happens when you put 87 octane in a twin
 

Somehow I must have pushed the wrong button on the Chevron fuel pump last week or maybe the station got its fuel tanks mixed up. Whatever happened, shortly after filling up, I noticed that the FR-S was running a bit rough. This became progressively worse over a day and by yesterday morning the damn thing was acting like a bucking bronco. Surge followed by staggering in low gears under acceleration, smoothing out in the middle gears, but having rapidly alternating power drop outs and surges above 6000 rpms. This caused a violent back and forth rocking as the weight transferred from rear to front and back again. Like water sloshing in a bowl, except my brain was the thing getting sloshed!

I figured there might be a connection with the fillup, so I did two things: bought a bottle of Permatex NOS octane booster and gave the car a topping off with 93 octane (about a third of a tank). The Permatex NOS is supposed to be good for 3.1 octane boost (31 octane points) and contains 5% nitromethane! :D Within five minutes of the additive/fillup being put into the tank, the bucking and hesitating stopped and the car went back to driving normally. So, bad or too low octane gas appeared to be the cause.

I can only guess that the ECU was intervening to prevent severe detonation, with the resulting effect of alternating bursts of applied power and lost power. Once the octane was sufficient for the engine, the problem went away. Has anyone else ever encountered this fuel related behavior?

Well, now, babydriver, first I would contact Permatex Corporation and tell them you have a testimonial that you will share with them, for a price, so they can use it for their advertising and promotion.

It's my understanding that the engine will run OK on 87 octane ...... it just won't run with full power, because the ECU will pull back on the timing.

Maybe they sold you a little water with the gas at the station and the NOS stuff overpowered it .....:D

Since you can't remember which button you punched at the pump, are you sure you didn't hit the "diesel " button ..... :eyebulge:


humfrz

Nah, the diesel button is green and the nozzle didn't fit, I mean won't fit. I suspect bad gas too, as I don't remember pressing 87 octane. Perhaps the 1/3 of a tank of 93 did the trick and the NOS went along for the ride. What is not in doubt was how badly it was running before today's fillup and how quickly it returned to normal afterwards.

Next time pay attention what you are doing

Yep, MOST of the time ...... :sigh:

I was back in Saint Louis a couple weeks ago and pulled into a BP station.

I grabbed a pump handle with a BLACK glove on it and was trying to jam it into the filler tube of my rental car, when I noticed it didn't fit. About that time a young lady asked "are you sure you want to put diesel in that car?"; she went on to say that the handles with the GREEN gloves are the gasoline ..... the handle with the BLACK gloves are diesel.

I think the rest of the world is different from that BP station ..... or I need to get out more ...... :bonk:

When I get my scooter, it won't matter ..... as long as I don't try to plug it into a 220 volt outlet ....... :confused0068:


humfrz

OK, I guess I'll have to add a "sarcasm" emoji when I'm being ironic. :clap:

I looked up the MSDS for Permatex NOS and it provided the list of ingredients, Numbers are in percents:

kerosene 8008-20-6 >60 (%)

manganese 2-methylcyclopentadienyl tricarbonyl 12108-13-3 <10

(MMT is an anti-knock additive, once commonly used in gasoline, but no longer commonly used as a fuel additive in pump gas in the U.S.)

proprietary polymer mixture, unspecified <5

(Who knows? This is how you get a patent for what would otherwise be a bunch of industrial solvents mixed together with kerosene.)

:sarcasm:


naphtha petroleum, light aromatic solvent 64742-95-6. <5
solvent naphtha petroleum, heavy aromatic 64742-94-5 <5

(naptha is basically lighter fluid - light: 5 to 9 carbons, heavy 7-9 carbons)


Stoddard Solvent 8052-41-3. <5

(a mixture of aliphatic hydrocarbons, 7 to 12 carbon chains)


xylene 1330-20-7 <5

(dimethyl benzene, an aromatic hydrocarbon)


If we stick to the percentages as listed, they add up to 100%, given that the kerosene is "more than" 60%. Nitromethane is listed on the box but not in the MSDS. Interesting since it is not a petroleum distillate (it is synthesized from propane and nitric acid) nor is it a polymer. Must be a very small fraction indeed.

So, longer hydrocarbon chain molecules, MMT, a little nitromethane and kerosene. Sounds like Jet Fuel A?

Good reply ..... :thumbsup:


humfrz

I also noticed that the ingredient list for STP's octane booster is nearly identical to that for NOS octane booster. This can't be a gas dryer, because it doesn't contain any anhydrous alcohols (methyl, ethyl, isopropyl). We use anhydrous (200 proof) ethanol at work, and believe me, if there is any water in the solution to which it is added, that water is gonna be bound up in a heartbeat. In fact, it is nearly impossible to keep it anhydrous as it absorbs the humidity in the air!

The spark retard makes the combustion unstable. That causes the surging.

Not like that with 87. My car was filled with 87 by the dealer, I accidently put 87 in once (never push the buttons while at the beach during bikini season) and once when I was low in the middle of nowhere and they were out of 91. Other than a barely noticeable drop in power I never had a single other symptom from the pulled timing. Even the perceived drop in power may have been more reverse placebo than a real noticeable difference during my regular street driving.
Throwing my money in with the bad gas crowd.

You need to get out more.... it's probably a BP thing as here all diesel pumps are black and petrol is green. I'm fairly sure it's the same in the European continent too.

Oh, OK ..... good information ....... :)

So, is that related to driving on the "other" side of the road in the UK ... ??

(hey. I haven't had my oatmeal let this morning ...... so, be nice ......:sigh:)


humfrz

Yep BP changed colours many years ago (2007-8?) and has been messing with everybody ever since. Although black is usually diesel and green gas around here it is not carved and stone and there are a rainbow of colours used.

I've put 87 before in the car before. Ran the same except it felt slower.