Steve Weiner-Rennsport Systems

Hi:

Recently, the State of California has chosen to eliminate MTBE from motor fuels and instead, use Ethanol as the oxygenate to reduce emissions.

There are some concerns about this change that everyone who drives a performance car should be aware of, especially turbocharged ones.

1) Octane Rating: The highest octane fuels you might see now are 91, instead of 92. This may be an issue for cars with certain performance chips, high compression ratios, and forced induction. 91 octane is, IMHO rather marginal unless this is taken into account when undertaking any program of performance enhancements.

I've posted a matrix chart on our website for blending 91 octane pump gas with 100 octane unleaded race gas. I hope this helps. Look at the URL below.

2) Elastomer Compatibility: This is largely an unknown as the long-term database is incomplete. For certain, Ethanol is well known to attack and slowly dissolve certain rubber parts used in all fuel systems. You may not get the long life expected from such items and this deserves some scrutiny. Ethanol is also an excellent solvent and scours out all dirt, rust, and contaminates in the fuel system sending them into the filter. This causes rapid filter clogging and immediate fuel filter changes are recommended along with more frequent changes than the Factory recommends. This will stop your car dead! Change that filter at least twice a year.

Last, octane boosters are not recommended except in emergencies. The additives in any effective octane booster leave a big brown mess inside your engine and they do not improve octane proportional to costs. Further, these additives WILL attack the rubber gaskets, O-rings and seals with the attendant troubles that this will create in the long term.


Lets Talk about Porsches

'86turbo

before you make any assumptions check out these sites
http://www.vtr.org/maintain/gasoline-octane.html
http://home.kscable.com/ssutton/miat...e/toluene.html

Rick - '89 930

Steve, I live in Atlanta and recently BP service stations have taken over Amoco service stations. Amoco I thought always had the better grade and higher octane, 92. Should I been concerned we the BP takeover, they have been advertising that they have reformulated all their gasoline’s.

Steve Weiner-Rennsport Systems

Hi Rick:

I do not know if you ought to be concerned or not. Each oil company blends a different product in each region of the country for the prevailing conditions each season. This is done for lowest emissions and drivability in the temperature range that each area experiences.

I'm not familar with the blend that you find in the Atlanta area but if the EPA has mandated reformulated gasolines, it will not matter much which brand you choose from that perspective. Reformulated gasolines in general contain oxygenates such as Ethanol or MTBE that will lean your fuel mixture compared to a "standard" fuel. For a Turbo, this is is NOT good as these already run too lean in certain RPM ranges.

That said, every brand of premium fuel does not run and perform identically and you should try a few different ones to see which one works the best in your car.

Regardless of which brand you ultimately decide on, I would strongly suggest that your fuel mixture (CO) is checked and corrected if needed, for the fuel you use.

Once again, I would NOT recommed using Toluene, Zylene, or any other octane boosting chemical in these cars due to long-term attack and damage to the elastomers in the fuel system. That will be very expensive lesson.

jbird

How would running 100% race fuel effect the car on both short and long term?

Jim

JBH

Amazing enough, most premium gasolines in your area probably come from a central pool shared by everyone that sells that grade. The fuels differ primarily in their additive packages and here you may find differences.
The exception to that was Amoco who manufactured a clear premium - that was really good fuel. Alas, the cost of segregated storage, transport and retail tanks did it in.

Best advice is to go with a major brand. That way you are sure to get a good additive package.

I do not see the problem with using toluene or xylenes as they are common components of pump and racing fuel. These liquids are fully miscible and of the same boiling range as your gasoline. Unless blended at very high levels, they should not degrade any of the elastomers at a rate any different than normal high octane fuel.

I would strongly advise against using other forms of octane enhancers; especially oxygenates.

Rick - '89 930

What about the use of fuel injection cleaners/additives such as Chevron. Would you recommend them. If so, which one.

Steve Weiner-Rennsport Systems

Hi Jeff:

Good advice indeed from the "knowledgable",...

I must add however, that many people who choose to use Toluene, Zylene and other such chemicals tend to use too much under the philosophy of "If a little is good, then more is better" and this WILL damage the elastomers used in most German cars.

Racing gasolines blended with these same compounds do not cause any grief and we strongly recommend this alternative.

We have taken containers of Toluene, Zylene, Ethanol, Methanol, and MTBE then inserted various rubber bits (new) used in these cars. Seals, gaskets, O-rings, rubber fuel lines, and some of the internal pieces from the fuel distributors, fuel pumps, and injectors.

This was done to observe and document any long-term effects (2-12 months)from the use of these products. I must tell you that the Toluene and Zylene simply turned anything that was NOT Viton to mush. The hygroscopic characteristics of the alcohols corroded some the metal pieces over time and the MTBE appeared inert.

After watching this unfold over a 4-9 month period, I cannot recommend in good faith, the use of these compounds in any car at concentrations over 10% and even then, its risky over the long run.
The cost of the 930 fuel distributor, not to mention all the other fuel system parts that contain rubber, should be factored when making the decision about what to use.

BTW, the price for a REBUILT, exchange, Turbo fuel distributor is $ 2188.50.

ZCAT3

Steve - for those of us in CA that do not have 100 Octane fuel readily available (at least without using half a tank to get it), what do you think of the "homebrew" mix of:

100 oz of toluene for octane boost
25 oz of mineral spirits (cleaning agent)
3 oz of transmission fluid (lubricating agent)

Then add 16 oz of this per tank. This would be far below you 10% max for toluene, so is it fair to say this would not be of detriment ot the car? It seems like running low octane gas in the car is also harmful, so perhaps it is fair to say this is no more harmful than just running 91 octane?

Steve Weiner-Rennsport Systems

Hi Bill:

Using your formula at that mixing ratio should not harm anything as long as you fill the tank after you pour that in.

I will surely admit that the gasoline situation is not going to be easy nor convenient to deal with for certain kinds of cars. Some special efforts might be needed to locate and use race gas when required.

JBH

Rick:

I would recommend the Chevron line of products - they make some very good injector cleaner and additive packages.

Link to their products is here

This obviously addresses a different issue than the octane enhancers discussed above.

Steve:
I am impressed that Rennsport Systems conducted a test of different elastomers in different solvents - I believe your results and agree with you that in high concentrations, toluene, xylenes, and other light aromatics will definately degrade those materials and pose a risk to the fuel system. Too much of a good thing can indeed cause serious problems.

PramTT

Since they eliminate the 92 octane from the pumps here in CA, I have been mixing 91 and 100 octane from my local 76 pump. I used the mixing chart on the 76 website as a guide and I am shooting for 93 octane for my biturbo. It just happen that the 76 station with the 100 octane is just three blocks from where I live. At $4.50/gallon they are pricey but. . . . .

86944turbo

I believe that this octane problem is a serious one. I've read (don't know for sure) that Porsche's latest turbo's require 93 octane for max. perfromance. If that's correct, then in running 91 octane, you will lose some perfromance at some point. I've been using Sunoco GT-Plus 104 octane unleaded for 8 years. It has been delivered to my home in 55 ga. drums. It is expensive ($3.80-$4.50/ga.). I consider it vital as I run up to 1.4 bar. I understand that one of the ingredients in this fuel is Toluene. I've never experienced any problems what-so-ever with this fuel. I know of cars that have run 1.5-1.6 bar with this fuel W/O any problems (the genius is in the timing). Before I added my intercooler spray bar, I recorded 60C intake temps. at 1.4 bar. The MoTeC does not have any anti-knock properties, so I cannot risk anything but a top notch fuel, and I believe that this is the best unleaded out there.