How much Boost

[hottacoX]

how would one go about testing the octaine of their gas? I want to esure what I am pumping is what I am getting.....

 

[Torspd]

You would have to have it sent to a lab that does testing. If you found that thr octane was way off, then I would report the station.

The necessary octane level, also depend, among other things, on compression ratio. Subi's run about 18 from the factory.

 

[sdxrunner619]

Unfortunately this is happening all too often. I am at 16psi, on a 91* tune with only 16* degrees of timing max. I also always put 93* octaine in from a major company like Sunoco or Mobil. I'd rather stay at 670-680rwhp then blow the motor at 720rwhp.

The ways to help compensate for the crappy fuel is to run meth as a safety. Don't tune for it to make power use it as a cooler and octaine boost or switch over to e-85.

^THIS

I have a friend that made 720whp on a stock 240sx block. forged rods and pistons. Running e-85....lasted about 20k miles till a heater hose blew and she ran dry on coolant...:rolleyez:

 

[zacksblacktaco]

what causes a knock? what should be done to fix it? what can be doneto improve the longevity of a 400hp 1gr??

 

[Whitebeauty]

I think the last part of that question would be,.....Make it fat!..in other words rich.

 

[Bulldogger]

what causes a knock? what should be done to fix it? what can be doneto improve the longevity of a 400hp 1gr??

Knock is caused by poor octaine gas, too much timing or high downstream temps ( air temps above 125-130* going into the cyclinder start to pull timing)
Too prevent use a name brand gas and hope it is actually what it is suppose to be. Next good tuning air fuel ratios around 11.5:1 under boost, and not real aggressive engine timing. Third methanol (windshield washer fluid) spray used for cooling and octaine boosting, not to be used to advance timing for more power. Windshield washer fluid which is 35-40% meth and the rest water, helps cool intake charge and reduce knock and raises octaine fuel number plus adds alittle boost usually .5-1lb depending on size of nozzle.