Race gas

tonyphip

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Mar 8, 2012
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So i have an 88 7mgte built motor and tranny its been running good at 15lbs of boost, i want to turn it up to 25lbs, so the question is should i use 110 octane gas to prevent detonation? is anyone running at 25lbs? if yes what kinda gas you using?
 

Nick M

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A Lex meter and 550's will support that compressor with 93. And 25 psi is past the sweet spot on the 7M by a good amount.
 

tonyphip

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Mar 8, 2012
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whats the sweet spot on a 7M? and i have 550 injectors. someone told me i could use 91 octane and to mix a few gallons of 110 in with it does that sound like a good idea?
 

te72

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Mar 26, 2006
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tonyphip;1887453 said:
whats the sweet spot on a 7M? and i have 550 injectors. someone told me i could use 91 octane and to mix a few gallons of 110 in with it does that sound like a good idea?
I think Nick meant a CT-26, the stock turbo, which you don't seem to be running. However, "t3/t4" just tells us you have one of two different footprints for the turbo, doesn't really say much about it at all... You could have a turbo with a T4 footprint that is choked to hell at 25psi, or you could have a T4 footprint turbo that is horribly inefficient at "only" 25psi, or anything in between. ;)

Anyway, it's all in the tune. If you can meet the fuel demands for the amount of air getting into the cylinders... You might be pushing it if things aren't tuned right though. If you're worried about it, water/methanol is cheap insurance, as is toluene, if you know how much to mix in.
 

Backlash2032

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Sep 20, 2010
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Size and A/R are more important in this case I believe. Not that trim isn't important

Sent from my terrible HTC Rezound using Tapatalk. Don't buy HTC...
 

mk3-4-me

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Funny how people say T3/T4. Like TE72 stated, t3 and t4 is a flange type. Hybrid turbos use one section from each, so they say t3/t4, which doesnt explain anything.

What turbo do you have?

What mm is the wheel?

What are you using for tuning?
 

Nick M

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No, the T04E compressor is well past the sweet spot at 25 psi. Just look at the compressor map. I am not saying you can't do it. Have bowl work done to flow the air the compressor is trying push.
 

Notsafe1jz

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Aug 16, 2012
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Race gas is never determined by boost alone. Right now I'm running about 17-19 psi on pump on a T66 strapped to a 1JZ with A/Fs in the early to mid 11s. Zero knock and it's never done anything to scare me while driving it.

Here's how you should relate the need for race gas. 1. Your horsepower vs displacement/engine layout. 2. Compression/cylinder pressures. 3. What you are using to tune with/who is tuning. 4(optional, haha). If you are at the ragged edge of your injectors and want just a little bit more temporarily.

A good rule of thumb with race gas is any time you make over 80 hp per cylinder, it's a good idea to consider over 100 octane unless your tune/tuner is very good. Mind you again, this is all displacement dependent. Smaller pistons/displacement will fight knock better than a larger piston.

I can't imagine that you would make any more than 450-500 wheel with the set up above at the boost levels you are requesting, however as stated above what size injectors and what are you using to tune? I made about 400 wheel with a 60 trim on pump gas at about 23 psi with a 4g63. After that, the car got tuned on race gas as that's pretty ragged with pump on 4 cylinders(with old tech; s-afc and MAFT). Hopefully this helps a little bit.