I believe it 87NAT and here's why.
Back then, 93 octane gas was much better and more tollerant of knock retard than todays watered down 93 that we get. My best friend was running around on 23#s on a 60-1 T4 turbo with a DFI and 93 octane all the time without knock. His timing was set at 18* WOT in all gears. Witnessed it on many a night at the street races. Gas was good back then. Gas sucks today.
With todays turbo choices here are some items of interest that I have kept too memory.
If wanting 11's on low boost with a simple bolt on car, meaning stock bottom end, ported heads or aluminum heads out of the box, cam, ported intake, headers, downpipe, IC upgrade, and complete fuel system, you would need to run either a 67mm compressor wheel equipped turbo, or a 70mm compressor equipped turbo. There are guys out there who are doing this with a 67 P-trim turbo and with a 70 P-trim turbo. The converter has to be right, as well as suspension mods to be able to launch really hard if you limit yourself to low boost. By low I mean 17-19psi. The lower you run the boost, the more reliant you are on 60ft, in order to reach 11's. 59mm thru 61mm compressor wheels are typically mid 12 to low 12s on 15-17psi of boost. I'm sure there are some out there that have run 11.90s with a T63E running lower than 20psi on pump gas, heck, I did it myself with my old Limited back in '98, but you need to launch the car hard. It will be very hard to reach that level with a smaller turbo and only 17psi, unless of course the car is a super light weight and hooked like crazy. (IE: 3300# with driver and can deliver reliable 1.6x 60ft times.) 59mm through 61mm compressor wheel equipped turbos are good for 12's on pump gas boost levels. Throw alky into the equation so that you can turn the boost up to maximum limits, and up the timing, and then you start to get into the 11's with ease. Remember, traction and a good 60ft are the keys to successful low ets. More boost, higher octane and timing are keys to higher mph (IE: Horsepower).
One last thing to remember, when you start running larger compressor wheel equipped turbos, the charge temps are typically cooler at lower boost levels, however, there is a trade off, the cfm flow rating might not be very much higher than the smaller compressor wheel equipped turbos at the same boost level, so it's important to do your homework, before jumping into a super humongous turbo. I really like the 67 turbo and in my honest opinion, those who are looking to run mid to low 11's without having to max out a turbo will eventually fall in love with it as well. I can't wait to get mine installed this weekend and have some fun.
Hope some of this helps a little.
Patrick
, THDP, Dutt necked IC) and I really like it- pulls strong with the stock converter, and spools like a stocker........
