What can I add to gas to boost my octane rating for safety margin?
 

I'm editing my original post to facilitate those who don't read through the whole post.

I found a source for high octane race fuel locally (thanks to those of helped me!). From the information I have been provided by all the people here smarter than me, I have decided that high octane race fuel is the only safe sure way to increase my octane level.

I realize that I will not be operating my car at 9/10ths during my first track day. Below I stated I hopefully will be, but many have informed me I in fact won't. Whatever level I am able to achieve is irrelevant, since I am simply looking for a way to increase my safety margin to protect my engine.

Now, back to the original post I made 3 months ago...

---------------------------------------------------------------------

My significant other got me a high performance driving school session for Christmas. I have spent the last few years preparing my car to be track worthy. It is 99% there. I just have to replace the master cylinder and pick up a helmet and it will be ready to go.

I am worried about detonation destroying my engine during a track event. Since I'll (hopefully) be driving it at 9/10ths the majority of the time, I presume it will be running very hot. It is a euro SC with 9.8:1 compression ratio, so it's borderline as it is. At a recent dyno run, the tech mentioned that it looked like it could be detonating in the 6,200 - 6,600 RPM range.

I know those octane boosters you get at the FLAPS are bogus, so what can I add to my gas for this track event to protect the engine from detonation? Toluene, MTBE? And, how much do I add per gallon of gas? Is it safe for the CIS system to add any of these additives?

I know you can get toluene at Lowes/Home Depot, but I would need to find a local source for any other additives that might work too.

Thanks for any help in advance!

you need to address the possible detonation on street gas.

and/or start buying drums of race gas. as i recall mixing various octane ratings of gasoline gives you easily calculated new octanes. that is to say the increase/decrease in octane is proportional. 50% 93 and 50% 102 would give you 97.5.

"Klotz Octane Booster is a concentrated tetraethyl lead substitute formulated to increase the octane rating of gasoline up to 10 numbers or more. Helps eliminate engine damaging detonation, spark knock, pre-ignition, and pinging from low octane gasoline. Octane Booster modifies the burn speed and flash point of gasoline to create a stable combustion chamber flame front, maximizing performance and power. Stabilizes oxygenated gasoline to prevent lean-out conditions. Klotz Octane Booster provides needed upper cylinder lubrication that is missing in unleaded gasoline."

You need to add high(er) octane gasoline.

Hey,
You can also go to your local general aviation airport with a couple of jerry cans and buy 100LL av gas. Don't do this if you are running a catalytic converter or will be in the near future, the TEL residue will trash the converter. It will eventually pass, don't know how long it would take though. Another option is to go to your local motorcycle shop and buy 5 gallon cans of race gas.
Good luck
eric

The question is, what is "10 numbers or more"? I've heard that with these octane boosters in a can a point is really 0.1. So 10 numbers would raise my gas from 93 to 94, not from 93 to 103.

No catalytic converter here, my car has SSIs with an M&K muffler. Good ideas, thanks. I should start researching race fuel in my area. I'm in Indy, so there has to be a plentiful supply.

There may be dealers that will sell by the gallon
 

We have a dealer in Denver Metro called Duggan Petroleum ( www.dugganpetro.com ) that has pumps you can drive right up to to buy racing gasoline. You can fill up the tank and/or properly labeled Gerry cans at about $6-8 a gallon depending on grade, last time I checked. You can go well above 100 octane. I believe you can get either unleaded or leaded so you'd want to remove your cat converter if you choose the leaded type and put in a pre-muffler (M&K sells an excellent one) or a bypass pipe to protect the cat's innards (assuming you find a place like Duggan in Indy).

I've been told that an MSD ignition unit will help with lower level detonation too but I'm just drawing from memory.

Where is your track day at ?

Most tracks have fuel (good stuff) right there.

If you plan ahead you could show up with 1/4 tank and do a 1/4 more of some race fuel (or 1/2 & 1/2 .. but you get the picture) blend it ...
I would doubt that you really need 100% full on highest available octane.

Motorcycle after-market places (not always the dealers) will have fuel in 5 gal drums.

For tracks that I go to that do not sell race gas (some smaller ones), I take a fuel jug or two with me. Check around some of your local race prep/engine build shops and they most likely have race fuel they will sell you. 5 gallons of 100 octance race fuel mixed with 15 or so gallons of 93 octane should work fine in your application.

I'm running 10.3:1 compression, BTW.

Absolutely correct!!

Octane boosters all have issues with "collateral" damage; some of which you can see and some manifests itself later on. I would not use those for what you are doing.

Unleaded race gas will do the trick for track days and a Google search should show you where you can buy it in your area.

Stay away from aviation gas for two reasons: its full of lead that ruins the oxysensors & cats and the octane is NOT the same as R+M/2 at the pump. Further, its formulation is intended for smooth burning at high altitude and it burns too slowly for sea level use in automobile engines that run at different RPM's.

This is a little OT, but since Steve is here participating I am going to ask the question because I want to know his answer. What about E85 in our air cooled cars? We're using it very successfully here in Colorado in modern vehicles, but what about the old CIS cars that don't have an ECU that you can retune/reflash. Is a 10 or 15% mix of E85 with pump premium an option for the OP's application?

This was my backup plan. Problem is it requires pre-planning on my part, which I'm not great at. Sounds like good ol' race gas is the only safe method, so that's what I'll do. The track day is at Putnam Park just west of Indy. I'm pretty sure I remember seeing race gas for sale there.

Good question. I've wondered that as well since E85 has a much higher octane rating than E10. I've heard that E85 (and E10 for that matter) is not good for the rubber seals in the CIS system and will eventually deteriorate them. I'll defer to the experts to chime in though for a conclusive answer.

My guess would be no. You need to increase the amount of fuel around 40% for proper fueling with E85 and you would have to seriously modify a CIS FD to do this.

Absolutely VERBOTTEN
 

There are at least half a dozen reasons to never do this. I'll leave it to Steve to fill in the blanks but stay away from this idea!

I would say another reason is that alcohol can mix with water (unlike gasoline) and this water could be transported into the CIS system where very close tolerance items (like the fuel distributor piston) would suffer greatly if any corrosion was to be induced as a result of the moisture...

using pump gas, go back to the dyno, retard your timing a few degrees. do a comparison of the numbers. you may not loose any HP. the dyno is the way to set the timing anyway, advance it until you no longer see any HP gains.
make sure you have no air leaks, you do not want to be lean

try one step colder plug, if you are tracking it, you can run a colder plug anyway.

I just got off the phone with Matt on this subject but I'll try to summarize.

The use of E85 is a real bad idea for all Porsches built before 2009, despite the 116 octane (RON) of Ethanol for several reasons. Here are just a few:

1) Ethanol is hygroscopic and the absorbed moisture facilitates and accelerates fuel system corrosion of any non-stainless steel parts.

2) Ethanol attacks and dissolves elastomers in the fuel system thats not made from Viton. This means that any rubber parts: gaskets, seals, O-rings, fuel lines made from rubber will suffer.

3) Ethanol has 1/3 less BTU's per gallon and as such, requires richer fuel mixtures than gasoline. The fuel pump, injectors, and FD (CIS) components require upsizing to deliver sufficient fuel volumes to maintain Stoichometric or better, air-fuel ratios. In some cases, there are no options to do this.

4) Ethanol is a powerful solvent and washes the cylinder walls of their lubrication. Ethanol dilutes regular engine oils so special oils are needed to control engine wear. Remember, OEM's are not concerned about this; the motor simply must make it through the warranty period. Race cars using straight Ethanol use special oils for this fuel and E85 isn't THAT much different.

5) Ethanol is very detonation resistant, however an engine using E85 really needs different ignition timing maps (advance curves) and more compression to take advantage of this fuel's characteristics. This is not a bolt-on proposition and may render the engine unable to run safely on normal (E10) pump gasolines.


This is a very complex subject and I've just touched on the highlights. If I had time, I could write a book on this,.....:) :) :)

I do hope this helps,

could this change the mixture? i connected the LM2 to my car when i was driving home from charleston. at first i was seeing a little over 13 at idle, i know, rich, i had just bumped it a little more rich to see how it ran. but the main thing was, at speed, my mixture changed from around 15,avg, to 16 avg. BTW, not to hi jack, but ethenol was brought up and the need for mixture change, so this may be helpfull. anyway, this was on the hiway so it was steady speeds. i did fill up, cant rememeber if it was in the middle of taking readings. if i did fill up and filled up with a higher ethenal gas, would it appear leaner?

thanks for the info on ethenal steve.


as far as the OP, i still say retard 2-3 degrees and check on a dyno with pump gas.

The use of E10 or E85 will certainly require a mixture change as an engine calibrated for gasoline runs leaner with varying combinations of Ethanol.

Your LM-2 will show the differences,... :)

Really - unless you are Michael Schumacher undercover, or have extensive track experience, I sincerely doubt you'll be at 9/10's on the track as a green student [if it's PCA]

Usually you'll want to start out at controlled speed, smoothness if you are at 7/10's on your third session of the day you'll be doing better than 95% of typical first time students.

You can still have gobs of fun shifting before 6,000 rpms. You'll also discover that the car is capable of so much more than you thought. have fun!

a green student might be at 9/10ths very briefly... just before the dust cloud.

Steve,

As you know, I have posted on this before. My thoughts in this thread (http://forums.pelicanparts.com/porsche-911-technical-forum/385016-effects-ethanol-gas-2.html#post4002167) are:

Good show, Harry.

JMHO, but Ethanol is for drinking and gasoline is for motor fuel. :) :)

It's important to understand that when analyzing AFRs with different fuels and combinations, that you cannot use AFR ratios anymore in the traditional sense to determine if an engine is running lean or rich. You'd want to go by the Lambda values which is actually how the factory engineers look at it.

The Lambda value is the ratio that the fuel mixture is at or deviates from the Stoichiometric ratio, the ratio for the chemically correct air/fuel ratio necessary to achieve complete combustion of the fuel. Under complete combustion, without excess oxygen after combustion (lean) or a shortage (rich), Lambda equals 1.0. For pure gasoline the stoichiometric ratio is 14.7:1, or 14.7 parts of air for each part of gasoline. However for different fuels, the air/fuel ratio is different for each to achieve Lambda 1.0.

For common fuels this is:

Methanol, 6.4:1
Ethanol, 9.0:1
MTBE, 11.7:1

As you can see, for methanol, it would require more than twice the amount of fuel for the same amount of air to equal the energy output of pure gasoline, thus the decreased fuel efficiency and potential leaning mixtures from switching to such fuels or similar oxygenated gasolines. If you're seeing an AFR of 15 or 16:1 with an alcohol fuel, that's like seeing an AFR of 25 or 30:1 on gasoline!! In other words, you can not use the target AFRs for gasoline with alcohols.

Using your LM-1 or LM-2, you must either know the correct target AFR for your fuel, or switch over and focus on Lambda instead, which is a target reading that always remains consistent, irrespective of the fuel or combination used. For example on a LM1 or LM2, if you were running pure ethanol, if you read a Lambda of 1.0, you will simultaneously see an AFR of 9.0, where you'd want to be to normally be at idle and cruise, and where the O2 sensor would try to modulate it to if the fuel system had the range to deliver the increased volume. If you're running an alcohol fuel or mix and expect to see a stoichiometric at 14.7:1, forget about it as that would be incorrect and look at the Lambda which you want to be 1.0. If expecting to see 13.0:1 under power, instead focus on your Lambda at 0.88-0.89.

I saw a well written article about octane boosting with Toluene. I think it fits right in with this thread.
Toluene - Octane Booster FAQ

The student thinks there at 9/10th when the off-road adventure occurs. They're really only running about 7/10ths. Thats why the car, driver, and instructor usually come out unscathed.

I'm just amazed that someone would ask how to raise their octane level, and not post what the heck they were using for fuel when they posted.

No need to be amazed. In fact, I got quite a few helpful responses and learned a lot about fuel when I posted this close to 3 months ago.

Thanks to at least three helpful people here on Pelican, I have located a few sources of race fuel here locally. I'll be mixing the race fuel with the mystery gas that I use regularly for my first track event. I'll feel much more comfortable knowing that when I'm driving 1/10th, 5/10ths, 7/10ths or whatever level I am able to achieve, that I don't have to worry about my motor suffering from detonation.

Indy 110 octane
 

The Speedrome race track on the eastside of Indy has 110 octane nearby . Also The Sunoco on US 40 at the NW corner of the Indy airport property has 110 .Also the Sunoco near Oreilly Raceway main gate has it . Enjoy your track time and keep the shiny side UP .

Eddie