nasty pinging while using shell 91 octane

[turbo970]

dunno why but when i switched from a local gas station and started using 91 octane from the shell i would get nasty pinging every time the motor would go under load with no boost. then switched back a month later it stopped. could the e 10 they put in cause that pinging? all i know is the local gas station puts a ethenal treatment in their fuel. its supposed to help the negatives of the ethenal

[Legacy777]

It all depends on how the fuel is blended at the terminal. For example, down here we have 87 octane as regular and 93 as premium. At the terminal there will be tanks of regular unleaded, premium, and ethanol. For the terminal I oversaw the gasoline was blended with ethanol, regular unleaded (87) with 10% ethanol, and premium unleaded (93) with 10% ethanol. Ethanol will raise the overall octane level of the fuel, so the resulting regular unleaded may have an octane rating of 88 or more, while premium may have a rating of 94 or more.

What some terminals are doing, primarily for regular unleaded is using sub-grade unleaded (85-86 octane) and blending it with 10% ethanol. The overall octane level will be at the minimum level of 87 octane. So for your area, they could be making 89 octane and then blend it with ethanol to become 91 octane. I will say typically premium is treated better and is "protected" so not to cause contamination.

Ultimately it will depend on the recipe the jobber (trucking company) pulls and delivers to the station. It's possible the local station is getting its gas from a different terminal or just has a different recipe.

I'd suggest keep using what works.

[turbo970]

i'm sticking with the local gas. i never gave it much thought but when i went up hill and hit 3000 rpm it would ping like a machine gun. then stop once i let go of the throttle or went past 3500 rpm. i had the local subie mechanic listen and he said it could be the valves but when i said i switched gas stations he said check for pinging. its weird that the shell being name brand fuel would cause pinging.

[turbo970]

been running turbo 108 race fuel and use a half quart on every fill up. cost more but no pinging and engine temps are down. even notice its a tad more responsive.

[James614]

How many gallons is your average fill up? According to my rudimentary calculator skills, with 10 gallons of 91 and 1/2 quart of 108, you wind up with a 91.2 octane mixture. Of course, this is about as much as those bottled octane boosters claim to give (deceptively, as they'd advertise that 0.2 octane rating increase as 20 octane "points"). I'm curious, because I've never really put much stock in the idea that 0.1 - 0.2 octane would actually make a noticeable difference. I've always thought differences in fuel purity, water in the car's fuel system, etc etc would cause a margin of error larger than that.

[turbo970]

the 108 is bottled race gas which is 108 octane. i use 16 oz which is one oz per gallon. it brings the octane up to 94 octane. there is turbo 108 octane booster but i dont use that. i use the 32 oz bottles of race fuel

[James614]

I know you were using race gas, though what formula are you using to calculate the octane mix? I'm going off of (%FuelA*OctaneA)+(%FuelB*OctaneB)=Final Octane. Going off of that, you'd need way more than 1oz/gal to bring 91 up to 94 by mixing with 108.

[turbo970]

thats what they said to use for 94 octane. same formula torco said to use. but i cant get torco local so i get the turbo 108. 1 oz per a gallon to reach 94 if i use the whole bottle they claim 98 octane

[Legacy777]

James's equations are correct. 1 oz per gallon is not going to cut it. Below are links to a calculator and an explanation of the formula James posted.

http://www.wallaceracing.com/octane-mix-calc.php

http://www.racegas.com/article/52

[turbo970]

then how did torco come up with their formulas

http://torcoracefuel.net/2-docs/acceler ... -chart.pdf

[Legacy777]

I don't know.....Torco may be different stuff than normal race gas.....but even still I don't think 16 oz. is going to do much for 10 gallons of gasoline.

16 oz is 0.125 gallons....that's not much compared to 10 gallons.

[turbo970]

well its working lol i may try a jug of vp racing 110 to mix in

[James614]

then how did torco come up with their formulas

http://torcoracefuel.net/2-docs/acceler ... -chart.pdf

That chart is for using Torco Accelerator, which is a race fuel concentrate, so you don't need nearly as much (although I don't understand the dynamics of concentrating race fuel, it seems like if that's possible then you'd want all fuel to be concentrated).

[turbo970]

the guys at turbo 108 said there race fuel is close to torco's formula if not a lil stronger. so i gave them a shot since i can get it local

[James614]

Well, if its also concentrated then it's probably about the same. Now I'm curious about how you concentrate race fuel (or any gasoline for that matter), to get that much of an octane boost from such a small amount of fluid. Doesn't make any sense to me. And it makes sense that if you could simply concentrate fuel, why wouldn't refining and oil companies be doing this to save massive money transportation and storage? And automakers could significantly improve packaging/safety/weight with much smaller gas tanks.

[turbo970]

i do know theres MMT or something like that in the race fuel concentrate from turbo 108

[James614]

I found some interesting discussion on NASIOC about using Torco:
http://forums.nasioc.com/forums/showthr ... ?t=1448046

Generally, it seems that it works, and it doesn't really sound like concentrated race gas in the manner they advertise (more like a concentrate of popular additives commonly added to race fuel). But they also mention it killing catalytic converters, if you care about that kind of thing.

[turbo970]

no cats on my subie lol

[Legacy777]

James,

Thanks for posting that info....interesting read for sure.

Also, for those that are curious, here's what MMT is.

[Legacy777]

Well, if its also concentrated then it's probably about the same. Now I'm curious about how you concentrate race fuel (or any gasoline for that matter), to get that much of an octane boost from such a small amount of fluid. Doesn't make any sense to me. And it makes sense that if you could simply concentrate fuel, why wouldn't refining and oil companies be doing this to save massive money transportation and storage? And automakers could significantly improve packaging/safety/weight with much smaller gas tanks.

From what I read in the link you posted it's just concentrated additive. So you still need the same volume of fuel....it's the different or more additives that change the octane rating of that fuel.