Hi all. For a stock or nearly stock program, we know that
our car will handle 87-octane without blowing up, and will
dial down the timing. We know it will adjust and run faster
with 91-octane or 92-octane.
I wonder how high this adjustment will beneficially go?
If I can get 94-octane would it show on a dyno? 97? 99?
I know there are different programs from different tuners
that are specifically for higher octane race gas. I am just
asking about how good is enough with stock or stage I
level programs. I just talked to one tuner who said that
the car will get more power all the way up to 100 octane!
Joe

 

We have tested with all kinds of fuel with our Softronic flash. One car that we put some VP MS109 in picked up around 30-40 whp on the dyno. We have also run a bit of leaded gas in certain cars with cats and have seen changes in power. ( We do NOT do it often just once to test. It will kill cats and o2 sensors so I do not reccomend doing it with out parental supervision lol.)

Mitch

 

Hi Mitch. Are you saying that you got 30-40hp by going from 92-octane to 109-octane?
My question is: if you mix 109 with 92 to get 100-octane, will you gain half that, (15-20hp)
or would the car gain 30-40 hp with 100-octane, and any higher octane makes no difference?
I have two extra-performance options:

1 - 100-octane unleaded race gas (mixed with some pump 91-octane)
2 - mixing 1 gallon of toluene with a tank of 91-octane to get about 93.5.

If I find out our cars will gain all the way up to 100-octane or more, then
I have to go with option 1, with as little pump gas as possible. However,
if we find that our car will gain only up to 93, 94, or 95, then I can easily
go half-and-half with race gas, or even get all the goodies with a gallon
of toluene.

This discussion is for stock or stage I or stage II cars. I know that fancy
tuners can make a program to take full advantage of any super-duper gas...
Joe

 

The only way a higher octane fuel will provide you more power is if your timing is currently being pulled because of knock. If your timing is not being pulled using 92 -93 octane, there is no additional power to be gained from using a higher octane fuel.

If you can maintain timing as specified by the computer program, you are at maximum power as far as timing goes.

 

Does this mean Vivid's Softronic tune is causing the ECU to pull timing on pump gas? I'm still contemplating tunes so how would one know if the ECU was pulling timing? Would it show up on some of the commonly available diagnostics programs?

 

subscribed....great questions....hoping someone has the answers. I was running strictly VP100 and the car "felt" stronger, but no data. I have since gone to pump gas as I ruptured 2 fuel lines and the hypothesis was the higher octane fuel (actually higher toluene content) was "eating" my hoses (I know this is still debated).

 

Yes, that is the way it works.

We know that, and we've already had confirmation that dyno power
*is* increased with a stock motor by using higher-than-pump octane.

We understand that. The current question is:
"At what octane rating will the motor will get it's max power."
We already know that it is somewhere above 91 and 119.

 

I use ERC's MUL-A:

http://www.ercracingfuels.com/ercMulA.htm

You might consider it, in some proportion, when we determine the
minimum octane rating for max power for our cars. I suggest this
gas because it's fraction of toluene is 20%, which is essentially
identical to pump super.
Joe

 

Excellent question.

There is a range of maps in the DME, and will pull timing to increase power until it starts sensing knock. The question is, at what octane will there no longer be improvement.

In my e39M5 that number is around 96 (R+M/2) Any higher and there is no change in timing

I've run 100 and 95.5 in the 996TT and cannot sense a difference, BUT THAT IS NOT RELIABLE. Definately an improvement over 91 (california)

They'll be a lot of anecdotal inputs- but what would clinch it is a tuner who has monitored timing with various fuels. With stock programs.

A

 

i think u must have a tune spcificly for higher oct. that will let u rin higher boost to get more power... or if u have an ebc , u can simple crank the boost up on 109. with astock ecu i dont think u will see much gain with 100oct.. as i know my m3 needed a tune to take advantage of the higher oct.

 

No it does not pull timing. We would not set a car to pull timing and add fuel if it were knocking as this will send EGT's through the roof.

Porsches have a very dynamic knock detection system that is really unlike any most any other car. The ecu can detect the octane rating and it can automatically trim in added amounts of timing to increase performance or vise versa.

I would say test for yourself and see the gains. I cannot say it will go to "X" octane as I dont have hard enough evidence to say either way. We added 5 gallons of 109 to under a quater tank of 91. We have also run just 116 in P Cars before. I would say there is a limit it will get to and I would think that C-16 is probably too much and would make no difference between an unleaded 109. We get such bad gas here in AZ that anything is better than 91. So the gains would be less on 93 with 109 I am sure of that.

It is pretty neat how these cars do a lot of the self tuning and trimming that they can do. I would say the next best thing would be some sort of Ion sensing that would run a closed loop ignition control but that is still some time out before we see that in OEM cars.

Hope this helps some,
Mitch Mckee
Vivid Racing

 

My best guess is about 96 or so. I tried this on a dyno years ago(M3 e46 and 996tt) and do not still have the sheets but I do remember a jump in torque from 91 to 95, then no improvment running 105 unleaded race gas. I just try to mix for 95 when I can. 10 gallons 91 pump to 7 gallons 100 no lead.

 

Comparing a Porsche TT to an M3 in terms of ECM's is not a fair comparison. There is no reason to be using race gas in a N/A M3 unless you are higher compression. The 2 computers are totally different.

I do see what you are saying but it is the same with an Evo. You can not set a timing value and then put in race gas and the timing increases, well it will if it is knocking. Totally different control methods.

Mitch Mckee

 

On an otherwise properly running stock engine, 93 is all you need for full power. Just monitor the timing and you'll have your answer. It's not that complicated to determine.

Obviously, with heat soak, your requiremements increase.

 

There is a limit. For instance, I know on my twin turbo S4 that 96 octane is the make the ecu will automatically adapt to (ie it stops adding timing). However I have a separate file that used race gas and advances timing even more.