I will be running my car at the track for the first time this weekend. I have done a search and can not find any solid information. I have a few questions reguarding racing gas.

1) Does racing fuel have lead in it?

1b) If it does, will it harm my o2 or cat?

2) My car has 9.3:1 compression with 11 PSI of boost, should I use racing fuel? The supercharger is NOT intercooled and I do not have an alky system.

I want to run the car hard, but want to do what I can to prevent knock. I do have a MSD-6BTM igntion, so I can pull timing based on boost, but I want to hedge my bet if I can. Any help would be great. I will post times after I run it.

Note: I edited this post to reflect the proper compression ratio, I had originally listed it as 9.5:1

 

 

Right now I drive it on 92 octane with a bottle of 104 octane boost in each tank. I have not run it at full boost for more than about 2-3 seconds on the street.
Normally I set the Boost Timing Master at 2 degrees retard per pound of boost(with a max of 20 degrees retard). I have watched my knock counts through the RPM range and when I get counts at higher RPM's I can usually get them to stop by turning up the timing retard.
But as I said, I have not run it at full boost for any extended time. So running the quarter mile, I anticipate it being at full boost for a good 12 seconds.

 

Why not build a cheap water injection system to keep detonation away and give a few degrees of timing back?

 

Well, since you called me on it I will have to fess up. I have an Alky injection system, I just have not put it on because with street driving the MSD ignition seems to be able to handle it.
If the engine does not hold up racing(and that would not suprise me) I am prepaired to upgrade, but I was still curious about racing gas.

 

I am not a serious drag racer, but I do have some experience racing boosted Chevys with stock engines, and somewhat high compression ratios. So FWIW, here is my opinion:

I personally would run race gas every time I run. The last outing at the track was with my Turbo Z24. I run 10psi of boost on a stock '02 U-van 3400V6 (9.5:1). I do have water injection, and it does not knock. On the first pass, the hose leading to the FMU came off (I guess the rubber got a little soft from the temps because it was about a 90 minute drive to the track withno cool-down time). I ran lean halfway down the track, and lifted just as I shifted into 4th (surprisingly, it still went 12.6 at 108mph). I honestly feel that without the 3 gallons of 104 in the tank, I would have been replacing pistons. Of course the water injection also provided a cushion, but IMO it is not worth it to take the chance. You never know what can happen when you are racing, and it is worth it to have the extra margin of safety.

I plan to install a water injection system on my TT IROC before I run it to 10 psi as well.

 

Well, I ran it today. I ended up using 93 octane and put the 104 octane boost in the tank (I mixed the container with 4 gallons of gas rather than the recommended 20 gallons) The car ran fine and I had no audible knocking. I will install the alcohol system before the next time I run it.
Now for the results: 14.4 at 102MPH with a 2.25 60'.
I really thought it would do better, but I still had fun. Next I will work on getting some traction.

P.S.- This 305 may not be very fast, but I am very impressed with how well it is holding up.

 

Using the boost retard keeps detonation away by taking out timing and hurts power a rediculous amount. When you run water/alcohol injection, you can keep your timing where it is without detonating, thereby giving more power for very little $. Paxton kits used to come with water injection, when they replced it with the boost retard power went down (and the price of the kit went up).

 

I agree with you 100%. I am a true fan of water injection. Too bad Corky Bell disapproves of it so much in his book. It gives a lot of guys a bad impression of it, even though it works very well, is cheap and reliable. I wonder if Bell ever tried it??

Hugh MacInnes book has some good water injection tech though.

 

The one bad thing about water injection is the fact that the WI is the only thing that keeps a motor from detonating. If the system were to fail or if you ran out of liquid, engine damage could occur.

Carroll is a big advocate of WI on its supercharger systems.

 

There are several jap cars running water injection stock so I would imagine the concept to be very reliable. The only catch being that I believe a sensor switch is used to limit boost and or timing when the tank is empty. I think that would be tough to duplicate but you could possibly use an OEM window washer tank sensor to at least illuminate a dash warning light when your tank ran dry. I know a light in my buddies Passat comes on when his window fluid is near empty. Seem like it would be simple to adapt, just a thought.

 

Thats great to know- any specific vehicles you know of (good to know in case I get in an argument over water injection )

 

I may need to eat my words on that, there may only be one, the Subaru STi. I thought the EVO VIII had it as well but can't back it up right now, the rest are JDM cars we don't get here like Type-R RX-7's. Of the two articles I read on the STi one said water injection the other said manual intercooler spray. To my knowledge the the STi runs both, Subaru's web site doesn't get into it. An automatic system that injects water based on certain parameters with a manual system to spray the intercooler on demand. Either way it uses water as an effective means to control detonation in a stock waranteed OEM application. If you can call a WRC homologation car "stock".

 

Don't those jap cars water inject onto the intercooler, not into the intake itself where it cools the air by contact?