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93 octane gas (381rwhp) 100 octane gas (406rwhp)

343 Views 7 Replies 4 Participants Last post by  Steve Jarvis
I returned to the dyno for another try with race gas since my BPU Supra seemed to be on the low side on my first dyno visit.

My first visit to the dyno was in sequential mode with an EBC so my boost would spike to 22psi hold 18.5psi and drop to about 17psi at redline. I heard a little knock at the transition to the second turbo but it didn't appear that I had gotten any timing retard. This netted 381rwhp and 413rwtq.

My second visit to the dyno was in ETTC with a MBC so my boost would spike to about 19psi hold 18.5 and drop to 17psi by redline. I had also added the "MAX AIR" airbox to my HKS intake (this was not the reason my #'s were higher). The big difference was I added 100 octane gas so I wouldn't get any knock. I wanted to see if I had gotten any timing retard the first time. Well I think it is easy to see that I did. I believe that these #'s are more indicative of the power my car makes on the road since I never had any knock on the street. But with basically no additional parts I made 406.2rwhp and 424.5rwtq.

You can see my mods and dyno chart at

Later, Steve
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Great numbers Steve. Sounds like your car runs well. I dont know about the gas in your area but here in Hawaii BPU Supras trap about 107-109 on pump gas and 115-118 on race gas. The 92 octane is not very good here.
we mostly have only 93 octane up here !
I ran 115.45mph on 93 octane. Next time I will try putting in some race gas and see what it will do. I don't think it will make much of a difference, because I only think I was getting knock retard when I was at the dyno with no air going through the intercooler.

Later, Steve

[ July 13, 2001: Message edited by: Steve Jarvis ]
You first dyno run has denotation written all over it. Look at how jagged the curve is. If that is happening on the Dynojet (light load) that is definitely happening on the street when on 93 octane. You really need to

to pull some timing advance -or- run race fuel all the time -or- drop the boost.

I also saw you were approaching 13:1 AF ratio on that first run. That is way to lean on a boost application. I wouldn't go leaner than 12:1.

Your motor won't have a long life detonating like that. A high MPH pull in 4th at that AF ratio is going to really heat those pistons.


[ July 13, 2001: Message edited by: TimZ28 ]

[ July 13, 2001: Message edited by: TimZ28 ]
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I had knock on the dyno because there is basically no air going through the intercooler. On the street there is plenty of air going through the intercooler. Lower intake temps no detonation. Also on the dyno the only time it knocked was at the transition to the second turbo when the boost spiked.

Regardless it's better now, and this car has done more than 500 miles on roadcourses and over a year of street driving in this basic form.

Later, Steve
Steve, I think you will find 100 octane makes a difference. Our ECUs will add timing until they detect knock, even more than would be seen on a stock Supra.

But what about that a/f? If you add some fuel you might be able to smooth that line a bit.
I actually added 2% in the 4200rpm range. I could probably get everything a little better, but I don't think there is any substatial gains left. I was in a hurry to get the T78 RX7 we built on the dyno so we could start tuning it. We spent 2 hours on it. We were pretty happy with the 442rwhp at 16.5psi.

Later, Steve
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