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Going from 97 pump gas to 100% methanol? or 50/50 racefuel?

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Hi, I race on my 240sx with a sr20det and 425whp nothing funcy (holset hx35), I was running 97 octanes and octanium of vpracing (80 points of octane) and I have some troubles with the engine. We are taking the head of this week but it looks like headgasket (arp head studs and cosworth gasket) so we are probably gonna try a different fuel to keep the engine safe, the log show .78 lambda and the boost that we tune at the dyno (20psi). We have two options for this... going 100% methanol injection or running 50% 97 pump gas and 50% leaded race fuel, probably sunoco 116 octanes. Wish option is best for safety and/or power, I have only tune methanol with some drag cars this car is only use every two weeks and have 6-7 races per year. I have heard about the problems with any alcohol fuel but I have never actually seing it. Any comments or recomendation would be great, with the 50/50 combination I have seen 100°C less on the exhaust at the exacly same tune that without the 50% leaded race fuel, and tune engines to .86 lambda no problems...

I'm assuming you're talking about changing the main fuel the engine will run on rather than supplementary injection? If so I'd recommend the 50/50 mix of pump gas and race gas. Methanol is a pain in the ass to deal with since you need to flush the fuel system post event. You'll also need to inject around 2.5 times more methanol compared to pump gas so the fuel pump and injectors will probably need to be replaced with larger items.

Unless you're aiming for a large increase in power over where you are now, the 50/50 mix should give you plenty of octane to be safe.

I don't want to go any higher in power I just want to be safe and save money/time on engine problems... And yes I'm talking in change the fuel that the engine is running with another, I will go with 50% 97 pump gas and 50% sunoco supreme 116 octanes is the best price/octane that I have in hand. The engine have more than enough power to stay on the top of the competition with my corrent car so I will probably gonna keep the lambda at .80 that I'm running now and the ignition map aswell.

Thanks for the advice I will go with that.

My only other tip would be that you will need to be very careful with your mixing to make sure it is always the same 50:50 mix. Any variation will ultimately affect the final octane of the fuel. This isn't quite as significant if you're not requiring all of the octane for engine safety, or if the fuel you're mixing with is non-oxygenated. If it is oxygenated then the air fuel ratio will change if the mixture varies significantly.

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