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Discussion Starter · #1 ·
I'm a bit of a newbie and looking into buying a single turbo supra with midsized turbo (65-70mm compressor, ~.7 A/R)

If i do get a supra ti will have to perform daily driving duties. Since i can't very well afford to drive around with 100+ octane race fuel all the time, but would still like to enjoy the fun of 600rwhp on occasion i was wondering what my options were, and what people recommended and/or what was common, i'd really like input from daily driven singles. I think the easiest way to do this is to list what i understand the options to be and you guys can correct/add to what i have:

1) 93 octane pump gas. I'd probably just drive around with the boost controller set around 14-15 psi or let the boost be controlled by the wastegate with BC off. And then turn boost to 18-20 psi for spirited driving and/or race. How safe is occasionally boosting this high on pump gas. How much damage is done by occasional detonation pre-ignition, i've heard its not quite as fatal as with the beloved rotary engine i'm so used to. At A/F ratios of around 11 and say 20 psi of boost, can detonation/preignition be avoided?

2)Alcohol or Water injection. A lot of rotary guys use water injection to safeguard against detonation. Is it real common among supra owners? What are the differences between water injection and alcohol or propane injection. Where do most guys mount the reservoirs? How much higher can i go on 93 octane with alcohol injection? Would 22-24 psi still be safe, or is water/alcohol injection kinda like a band-aid, when the only real solution is higher octane fuel?

Just looking options other than toluene, xylene or C-16

Since i won't necessarily be going with an AEM car, comments regarding timing and the ability to run more boost if you retard the timing are welcome, but i may not have that option.

For those with the SCM alcohol injection, how often do you refill and have you ran into any problems

Thanks for any info guys, it is much appreciated, and while i have searched some i probably havne't searched as much as i could have and i'm sure these questions have probably been answered before... but some of this stuff (the SCM kit) hasn't been around for too too long so i was looking for a recent opinion on things

SORRY ABOUT THE LONG POST!!!! THanks for those who took the time to read it!

1,439 Posts
Do a search, there is plenty of info on the boards. Anarkey, a member here sells a meth injection kit that allows higher boost levels than 24psi on pump gas.

Also, Afs of 11:1 are fine... just get a wideband so you always know how lean you are running.

Discussion Starter · #3 ·
I searched more after posting and answered most of my questions. Sounds like 18 psi is about the limit on pump gas, so i'lll probably invest in a meth kit if and when i pick up a supra. Has anyone been running one for a long time? Any blown motors on meth/water kit cars?

Discussion Starter · #4 ·
I guess I have had mine the longest, being the "inventor" of the MKIV system that lots of people have now. Almost two years now.

No failures. Quite the opposite. I personally made a mistake that would have cost my my motor, had I not had MW injection. I left the boost control set wrong, as a result my wastegate basically had unlimited boost. To this day, I have no clue how much boost that really was. Well over 32psi on 92 octane. Could have been 40psi for all I know. Engine was fine, and pulled like a sonofabitch.

Here's a testimonital of another saved motor:

“My car survived a 4th gear dyno pull and made 629.4 hp and 598 tq at 29.9 psi (dropping to 27.3 psi by 6600 rpm) on crappy CA 91 octane and methanol!! We then added 104 octane and made 644 hp and 610 tq on the same settings. Highest pull of the day was 646.5 hp and and a huge 645.4 tq @ 30.9 psi.

AFR during the 91 octane pull dipped into the danger zone and hit mid 14's above 5000 rpms, yet the EGT's still stayed remarkably cool at 650c due to the cooling effects of the

I am certain if not for the cooling effects of the methanol, my engine would be in a state of major meltdown now.”
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