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98 octaine blends and general fuel doping.

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Hello all this is my first thread on here.

I have an old r33 skyline that currently has a tired-ish stock internal rb25 that will soon be replaced with a warmed up rb25/30.

I've put my new turbo chosen for said rb30 onto the poor old 25. its a BorgWarner sx-e 364.5 .91 rear that should be good for about 820goat power at the crank. It spools remarkably well for its size on the 25 and zipps along well too. Now im thinking even more power could be pulled our of the rb25 but its 9.0:1 comp ratio, stock cast pistons, daggy head castings and baby cams aren't ideal to process what the borg is spitting out.

A normal person would e85 this situation but I have the following issues with that.

-e85 is only available in 200l drums where I am. its $3 a litre (98 is $1.55 a litre) my car uses 20/l per 100km costing about $30 e85 will use 30l/100 costing $90 so everytime I got to town it's $100 in fuel.

-My injectors and pump don't flow enough to make the power I want on e85.

-My partner doesn't like me keeping large amounts of highly flammable goods at home.

So what are my other options? Methonol blended to pump 98?, e85 diluted with 98 to e42.5 or e21.5? Mainly looking to add the fuel to cool combustion and prevent knock.

Id prefer something with a stoich ratio as high as possible. also it would be good not to have to change my fuel lines. (injectors and pump are fine) Methonol 20% is what I'm leaning too as methanol is more accessable. and cheaper however I don't know what effect 20% Methonol will have on my fuel system.

has anyone had first hand experience or know of any good tech articles on what effects fuel blends yield?

10-20% methanol is quite common here in the UK as there are hardly any E85 pumps. some people have seen gains of ~100bhp with a 20% mix tune, extra boost used etc, over pump super unleaded. It really depends on who's doing the tuning an how they do it.

That just reminded me of having a 200 liter drum of methanol standing around. Cost price 95 USD

Attached Files

I haven't tuned on any methanol/98 blends but I could see the potential for this working well. I'd probably lean more towards a lower percentage ethanol blend though if you're worried about your fuel system capability. The stoichiometric AFR of ethanol is 9.0:1 while methanol is 6.4:1 so for the same percentage of methanol in your 98 you are going to need to inject more fuel.

I've had some pretty impressive results from even low percentage blends of ethanol, and in most instances the potential improvement in power as the ethanol percentage increases tends to drop off pretty quickly. What I mean is that from E0-E25 you're likely to see a significant improvement in performance but from E85- E100 the gains typically are insignificant.

I ended up scoring some methanol on sunday and made the change to M20 on monday. I don't have a dyno for power figures but the car definitely likes a bit of methonol. I had a really rich 98 tune in it (lambda75-76) for safety. Added fuel overall then pulled a little out till I was at lambda .8 on boost. Even with the leaner mix the car is still running 5degrees lower in water temps after a session of power pulls.

Now I know it works I'm just waiting to see if the small methanol content will have dramas with attracting water in the high humidity durning our tropical wet season.

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