[BAN_M2C]

Anyone considered mixing 93 octane with 100 octane gas for our cars?

My old track car had been tuned to 93 octane fuel and after a while gas in my area stopped being distributed with 93 and was only provided with 91. Not willing to retune and lose power I resorted to mixing 91 octane with Torco Race fuel to get somewhere around 94 octanes and be able to still run the car safely with that tune.

In my area there is Sunoco 93 but there is also 100 octane Sunoco.. I believe at the pump or at least they sell the 5 gallon..

Any benefit of running the car with a mix of these two to bump octane? Maybe not stock, but with a couple mods done and this mix would the car adapt and run better?

http://www.sunocoracefuels.com/tech-...ulating-octane

[MadViper]

Very very interested on this topic, especially if this can be done without a tune and have some hp gains

[BAN_M2C]

Originally Posted by MadViper

Very very interested on this topic, especially if this can be done without a tune and have some hp gains

I have been thinking about throwing this out and see what some people here think about it.

I am relatively new to BMW and really don't know how adaptive these cars are to fuel.

But reading a couple places on how they have ran with 91 and see baseline numbers and some people run with 93 and see better baselines I wonder if mixing it up or even just filling with 100 octane would help.

I would think you need to run a couple tanks mixed before the DME registers anything and adapts but if you have a Downpipe and Intake lets say and no tuning the car will adapt based on the mods, what if you throw into the mix higher octane?

[DETRoadster]

I'm relatively certain that without mods you'll simply be pouring extra money into the gas tank. Not sure if you guys understand octane ratings or not. Excuse me if this is elementary to you. The "octane" rating is a measurement of how quickly the fuel burns and how susceptible it is to pre-ignition. The higher the rating the SLOWER and more controlled the burn. Marketing has done a great job of convincing folks it's the opposite. Higher octane, bigger bang, more power is what most folks think. That's incorrect. The truth is that the higher the octane rating the slower and more controlled the burn is, and conditions like compression ignition (or, pre-ignition) are reduced. This allows engine makers to either run higher compression, or, more boost. Now your engine is not going to change compression ratio so that's out. That leaves us with boost. Is your engine going to increase boost after detecting that it can get away with it due to you dumping high octane fuel in? My hunch is no. I'm guessing that BMW set a max boost based on readily available pump gas, like 92 octane, and has no provisions for the ECU to say "Hey look, I'm bumping the boost pressure that the wastegate will allow up and I'm still getting away with it. Must be 100 octane fuel in there, let's keep going."

Give it a shot, but my bet is you'll only feel your wallet getting lighter.

[BAN_M2C]

Originally Posted by DETRoadster

I'm relatively certain that without mods you'll simply be pouring extra money into the gas tank. Not sure if you guys understand octane ratings or not. Excuse me if this is elementary to you. The "octane" rating is a measurement of how quickly the fuel burns and how susceptible it is to pre-ignition. The higher the rating the SLOWER and more controlled the burn. Marketing has done a great job of convincing folks it's the opposite. Higher octane, bigger bang, more power is what most folks think. That's incorrect. The truth is that the higher the octane rating the slower and more controlled the burn is, and conditions like compression ignition (or, pre-ignition) are reduced. This allows engine makers to either run higher compression, or, more boost. Now your engine is not going to change compression ratio so that's out. That leaves us with boost. Is your engine going to increase boost after detecting that it can get away with it due to you dumping high octane fuel in? My hunch is no. I'm guessing that BMW set a max boost based on readily available pump gas, like 92 octane, and has no provisions for the ECU to say "Hey look, I'm bumping the boost pressure that the wastegate will allow up and I'm still getting away with it. Must be 100 octane fuel in there, let's keep going."

Give it a shot, but my bet is you'll only feel your wallet getting lighter.

Thanks for chipping in.

This is exactly why I wanted some people more knowledgeable than me on the topic to chip in.

In my track car is was running high compresion NA setup and the change to 91 was causing knocking. And we got it running nicely again by doing the mixture.

But like you explained the BMW engine is different and I definitely dont know the in and outs of how it behaves.

On a stock engine I see no benefit I agree.

But with a couple mods I was wondering if there would be any benefits given that the engine is adjusting to the mods and potentially to a better type of fuel.

[BruceM]

Actually, I think the most important adjustment modern ECU's make that is affected by octane is neither compression nor boost, but timing. If the ECU senses pre-ignition/detonation, it will pull timing, which will reduce power. ECUs are designed these days to operate just below the detonation limit, I believe.

What I don't know is whether an un-modded ECU will push timing to the limit of detonation if it senses a particularly rich octane grade of gas. If so, an octane boost would actually allow for an increase in power. If not, it will just serve as a protectant of the engine, entirely unnecessary in regular, non-track driving.

At the track, I always fill with 100 for my 930, especially important in the summer, with high ambient heat conditions on a boosted engine.

[PackPride85]

Originally Posted by BruceM

Actually, I think the most important adjustment modern ECU's make that is affected by octane is neither compression nor boost, but timing. If the ECU senses pre-ignition/detonation, it will pull timing, which will reduce power. ECUs are designed these days to operate just below the detonation limit, I believe.

What I don't know is whether an un-modded ECU will push timing to the limit of detonation if it senses a particularly rich octane grade of gas. If so, an octane boost would actually allow for an increase in power. If not, it will just serve as a protectant of the engine, entirely unnecessary in regular, non-track driving.

At the track, I always fill with 100 for my 930, especially important in the summer, with high ambient heat conditions on a boosted engine.

^What he said. It's not about boost. The car has predetermined boost targets (probably load targets) that does not changed unless you start getting detonation.

The car also most likely has a maximum timing advance table based on load. This is usually tuned from the factory at the highest pump octane they expect. In this case it could be 91 or 93. Putting in 100 will do nothing but drain your wallet faster.

The only way to really tell is to run it on a dyno measuring timing advance for 91/93/100 octane and see if (1) it actually runs more timing advance at higher octane and (2) if that even leads to any more power.

[ashburyn54]

Originally Posted by EL BAN

Thanks for chipping in.

This is exactly why I wanted some people more knowledgeable than me on the topic to chip in.

In my track car is was running high compresion NA setup and the change to 91 was causing knocking. And we got it running nicely again by doing the mixture.

But like you explained the BMW engine is different and I definitely dont know the in and outs of how it behaves.

On a stock engine I see no benefit I agree.

But with a couple mods I was wondering if there would be any benefits given that the engine is adjusting to the mods and potentially to a better type of fuel.

You will see gains on something like 96 octane vs 91 or 93 if the conditions are the same.

Less timing will be pulled once temps start to rise. E85 is an extreme example due to the cooling properties but just 3 gallons of e85 on the stock tune(e30 fuel equaling 96 octane-ish) raised the baseline from 320-330whp to 360whp and about 400 foot pounds of torque. More than e30 or if you raise those boost targets and your HPFP will start to suffer.

This is based on real world dyno testing but I like the safety net of a little more knock prevention when running on the track.

[DETRoadster]

Yes, yes, of course. You guys are absolutely spot on. I was neglecting the timing aspect as a variable that the car can and will control based on detonation sensing.

I stand by the assertion that on a bone stock engine with no modification to compression, boost, or timing, the results will be marginal. Certainly not worth it to dump octane boost in or mix in race gas just to run down the street to buy groceries and drop the kids off.

I suspect you guys may be right though, that under extreme conditions like on a track, when you are pushing your 100% stock M2 to the limit, the higher octane fuel may ward off pre-ignition and allow you to maintain stock Hp levels beyond the point where the stock ECU would begin pulling timing on lower octane fuel.

So, Hp gain beyond stock on a stock engine = I believe no.
Prevent the ECU from pulling timing (and as a result power) under extreme situations = I can agree with that.

[BAN_M2C]

Originally Posted by DETRoadster

Yes, yes, of course. You guys are absolutely spot on. I was neglecting the timing aspect as a variable that the car can and will control based on detonation sensing.

I stand by the assertion that on a bone stock engine with no modification to compression, boost, or timing, the results will be marginal. Certainly not worth it to dump octane boost in or mix in race gas just to run down the street to buy groceries and drop the kids off.

I suspect you guys may be right though, that under extreme conditions like on a track, when you are pushing your 100% stock M2 to the limit, the higher octane fuel may ward off pre-ignition and allow you to maintain stock Hp levels beyond the point where the stock ECU would begin pulling timing on lower octane fuel.

So, Hp gain beyond stock on a stock engine = I believe no.
Prevent the ECU from pulling timing (and as a result power) under extreme situations = I can agree with that.

And this was part of why I wanted to pick some people's brains.

During an Autocross event or a full track day, as temperatures rise the car might pull timing if detonation is perceived.

Doing this mixture might just allow to run at high temps but feel no loss of power, something already being discussed in another topic I saw this week.

http://f87.bimmerpost.com/forums/sho....php?t=1346798

[rouxeny]

I think race gas for getting groceries will be a money suck. Save it for the track.

[auf Deutsch]

Sunoco used to carry 94 Ultra back in the day, along with shit 86 all at one pump.

[BAN_M2C]

Originally Posted by auf Deutsch

Sunoco used to carry 94 Ultra back in the day, along with shit 86 all at one pump.

I need to verify because there were some that had 100 at the pump.

I believe one in my area still does have that pump.

[Ramon.]

Originally Posted by EL BAN

I need to verify because there were some that had 100 at the pump.

I believe one in my area still does have that pump.

I know there is a Sunoco by me (new jersey) that has 100 octane. Here is a link that will help you find one local to you. http://sunocoracefuels.com

[zenmaster]

Originally Posted by DETRoadster

So, Hp gain beyond stock on a stock engine = I believe no.
Prevent the ECU from pulling timing (and as a result power) under extreme situations = I can agree with that.

Normally this would be the case. However, we can measure timing advance/retard while on a dyno and don't have to guess what will happen.
A stock M2 has an agressively tuned engine which already pulls timing on 91 without needing extreme conditions. Terry Burger measured all this several months ago. His HP/torque/timing measurements are also pretty much what one would expect from the similarly sized N55 turbo at 15-16psi.
To put it another way, a stock M2 will dyno slighty higher on 93 than 91 under same conditions.

[DETRoadster]

Originally Posted by zenmaster

Normally this would be the case. However, we can measure timing advance/retard while on a dyno and don't have to guess what will happen.
A stock M2 has an agressively tuned engine which already pulls timing on 91 without needing extreme conditions. Terry Burger measured all this several months ago. His HP/torque/timing measurements are also pretty much what one would expect from the similarly sized N55 turbo at 15-16psi.
To put it another way, a stock M2 will dyno slighty higher on 93 than 91 under same conditions.

Sure, sure. That I can believe. I does make sense that an M2 headed for the US market with a US market tuned ECU woudl have provisions to take advantage of 93 octane fuel as it's readily available in many states. But are the provisions there to take advantage of, say, 100 octane? Maybe BMW would spend the time to work that into the engine management code. I dunno.

I'd love to see some back to back dyno pulls with 93 octane and 100+. if it keeps on making more power I'll very happily stand corrected....and go by some octane boost

It would be pretty damn funny if folks spending $5k to $10k on exhaust systems and intakes for 0 Hp gain can be showed up by a guy and his $4.99 bottle of 108 octane boost.

[ashburyn54]

Originally Posted by zenmaster

Normally this would be the case. However, we can measure timing advance/retard while on a dyno and don't have to guess what will happen.
A stock M2 has an agressively tuned engine which already pulls timing on 91 without needing extreme conditions. Terry Burger measured all this several months ago. His HP/torque/timing measurements are also pretty much what one would expect from the similarly sized N55 turbo at 15-16psi.
To put it another way, a stock M2 will dyno slighty higher on 93 than 91 under same conditions.

This ^ right on the money

[NO_USER_]

Would you notice a difference if you had one M2 with 91 and another with 93, power wise?

Thanks!

[BAN_M2C]

Originally Posted by Mbavar2

Would you notice a difference if you had one M2 with 91 and another with 93, power wise?

Thanks!

I think the general consensus on this thread is YES, a 91 vs 93 run could potentially show better numbers for the 93 running car given that stock tuning from BMW might have been tailored around having 93 available at the pumps.

[BAN_M2C]

Thanks everyone for chipping in on the topic and laying out their ideas or thoughts.

So to recap and see if I understand what some of you mentioned. What I think the discussion has shown is that there isn't any improvement envisioned on a completely STOCK car by just adding 100 octane to it.

On a modified car with tuning you could definitely see improvement I would say.

What I think we also have been agreeing to is that a car with stock tuning, just by adding better or higher octane, you will ensure that as temperature rises you have no timing being pulled.

If the car has 91 it might sense knocking and pull on timing so you would have loss of power whereas with a potential mix yielding higher octane you wouldn't feel any loss of power because the car would not pull timing, you would most likely see the power being constant.

[NO_USER_]

Originally Posted by EL BAN

I think the general consensus on this thread is YES, a 91 vs 93 run could potentially show better numbers for the 93 running car given that stock tuning from BMW might have been tailored around having 93 available at the pumps.

Yeah, that makes sense. Real question, is it worth mixing 100 octane to get to 93 octane in California, if it's only your weekend car? It'd probably take about 3 gallons of 100 octane to make the mix = 93

~$60 per tank assuming 100 octane is ~$9-10/gallon

[Maynard]

Blast from my past - we used to mix leaded regular and unleaded super as cheapo racing fuel. The lead antiknock had diminishing effects (i.e. it helped the unleaded super more than it cost the regular) so the end result was equivalent to about 100 octane. Doubt you can still get TEL as an additive, and VERY toxic....