What octane rating fuel are you running with forced induction street engines? Interested in all options.
I have a 6-71 blower on a 440 with twin 750 double pumpers that I run 50/50 with leaded C12 (112 octane) and 93 pump gas (non-ethynol). Seems to run well right now.
Kid at my shop has 2 supercharged SBC sand toys. A rail and a truck. He uses 100LL avgas. Swears by it. And I know for a fact he's not at all shy about buzzing those motors to 4-5 grand all day long. His right foot is so heavy he walks in circles.
THAT's...an blind, open ended question if I ever saw one..! Let me count the ways - 1. Blower pressure ? 2. Static compression ratio ? 3. Cam design (dynamic compression ratio)? 4. Car weight ? 5. Transmission ? 6. Gear ratio ? 7. Street car ? 8. Race car? 9. Blower design, Roots, Screw, Turbo, Belt driven turbo, ______ ? 10. What have I forgotten ? Answer the above questions...THEN and ONLY then will anyone be able to even try to answer your question with an intelligent answer. Mike
Well I guess you called me out on that. I did mention that this was in regard to a street engine and I did ask the previous poster what his CR was. 1.blower PSI 10-12 psi 2.CR as assembled 7.98 to 1 3.ISKY 260 TB grind 4.2450Lbs. 5.4 SPD high 1st. Long spread to 2nd. 6.3.27 ratio to gain EGT with 4 spider carrier 7.Street car as mentioned 8.N/A 9.TRW/Rayay F/B TURBO AS STATED 10. YOU FORGOT TO READ MY POST
Hey Mike, Don't assume that who your having a dialogue with is an idiot. If you wanted the info on my build I would have been happy to give it to you, but instead you challenged my knowledge of my own ride. NOT COOL NORM
Use enough octane to keep it from rattling. I run 87 on the street, and 91 or 93 (depending on where I am) when I go racing. A little less boost, a little more compression, but it's a Roots blower, not a turbo. Those things scare me, you never know what it's gonna do, when.
I don't own, ever build anything forced induction for the street that cannot be ruu on minimum spec premium unleaded, which is 91 E10, using the US (R+M)/2, also known as AKI number. Only on special request will I build and tune for E85, but the owner must be made aware that this is a permanent commitment to use that fuel. Building a street car that requires exotic fuel to operate gets old really fast. I have customers with blown and turbo cars that drive them tens-of-thousands of miles yearly. This is would not be possible if the could not simply be filled up at conventional gas pump.
Hey guys, I asked a general question about octane ratings and forced induction for the street. I mentioned that I run 100LL. I have water/meth injection more as a intercooler because I have a draw through turbo and I can't run an intercooler with a draw through turbo. The Corvair is air cooled so I need the injection to keep cylinder head temp in check. I'm here to enjoy the hobby like all of us. They way Mike asked for the specifics seemed like a challenge. My apologies
I'd have a cylinder head temp gauge for each head, EGT ahead of the turbo, and an Oxygen sensor after. You have to know your air fuel mixture is correct. Lean equals hot. Too hot on a turbo car is bad enough, to hot on an air cooled turbo car can get expensive.
I have a full complement of gauges. Clynder head temp. Manifold pressure, oil pressure, oil temperature and a hidden wide band 02. I'm not having issues myself, I was looking for alternatives to 100LL Avgas.
I presume that you are not having issues with pre-ignition on 100LL. What results have you gotten with conventional premium? Do you have any control for spark advance that responds to boost?
61 - Stop your whining and man-up...YOU didn't provide this info to...anyone..! Was NO challenge whatsoever. Just asking for info that YOU...should have had the knowledge to provide...without...others having to ask..! Since you are...all knowledgeable and all, it should have been in your first post...at the top here. Mike
I have a recurved dizzy with initial timing 18 degrees adv. With a hybrid vac adv/retard canister and a vac solenoid to lock vac adv at idle and its triggered with a Crane Cams XR-700 ign. I asked the original question because I have always run 100LL. If the consensus had been a certain octane I was going to try it. Avgas gets pricey.
Last time I went to get 100LL they said they said they could only pump it into a plane due to new FAA regs. Ever try any off the shelf additives?
Well, both Jim and I run boosted stuff on plain old pump juice. I would see if you can come up with a happy combination of AF ratio, advance, and boost that will allow for that. The power potential may go down a little, but the fun level should not.
Mike, I was asking for a general consensus on octane for a street car. I didn't feel the need to go into specifics of my car. I did share the specs with you and I have not recieved your recommendation. If I misconstrued your earlier post, I got your message now. I won't be expecting a recommendation.
That has been the case for some time. Not everyone is following the law, which could result in some HEFTY fines. It is unlawful to dispense gasoline with any level of Lead in it into a motor vehicle intended to be used on public roads. It would suck to build a car that can only run on fuel that you are not supposed to have access to in the first place. When, not if, your supply is cut off, what do you do?
This is just an inquiry. Would the octane rating between different countries be similar? I know some places change the octane rating to suit different seasons. In Australia our lowest rating is 91 which is what my avatar runs best on . Engine design from 1948- 1962. Highest pump octane is 98.
My biggest issue is getting a proper A/F ratio through the whole RPM range. The large bore YH side draft that is currently on the car has its limitations. I have it running a bit rich for safety and to compensate for the wrapped exhaust.
That is true with regard to Avgas. I am a pilot and have a 500 gal tank I can pull from. I didn't build the engine to only run on 100LL. I have the fuel and it is certainly a safe guard against detonation in an air cooled engine.
Yes, but no. The octane ratings are the same, but the method used to assess them varies by country. The most common evaluation methodologies are: Motor Octane Number (MON). Research Octane Number (RON). Anti-Knock Index (RON+MON)/2, commonly shown on the pump as R+M/2, which is an average of the first two. That's what we use in the US. Due to these different methodologies, even when applied to the same fuel, you get different numbers. For instance, 95(RON) octane in Australia is 90((R+M)/2) octane in the US. That is for the same fuel.
Buy it at Sears Point, like all the other racers. The airport fuel was half the price though, when they would fill a jug. When, not if, that's cut off it will be a sad day indeed. Both of my blown street cars run pump gas.
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