TimH

iTrader: (2)

<http://herbstmail.com/v-web/gallery/Cars/Dyno>

Since I have no basis for comparison I don't know if this looks right or not. I'm a little surprised at how torque falls off above 6k. Sorry the line is so faint on the image.

Street Port
Blueprinted stock sequential twins
Open Intake/Downpipe/Cat-Back with stock cat
ASP Medium
Pettit Unlimited ECU
12 PSI 101 Octane
(peak RWHP reported as 281 @ 10 PSI in 3rd and 4th gear but I don't have the curves)

Any comments?

matty

why u running 101 octane?

TimH

iTrader: (2)

Uh, because I can?

Seriously, I've never hooked up an O2 sensor to know how good my A/F ratios are with the Pettit maps and figured I'd rather be conservative in case of a boost spike. Sometimes I put in 91 octane but mostly run race fuel which these days is only twice as expensive. I'm thinking I may push a little above 12 PSI soon, too.

matty

u make less power with more octane. only run hi octane when u want to run some serious boost. Not to mention u are wasting your money.
---only trying to help.

TimH

iTrader: (2)

Really? Something to do with the rate it burns?

matty

if you know then why do u run it? thats expensive

TimH

iTrader: (2)

I don't know what my A/F is. If I knew it was always ok or rich I might be less conservative on octane. Since I fill the tank less than once a month the money doesn't matter much, and a grenaded motor would overwhelm the difference for sure.

Does high octane really produce less power?

matty

yes.

TimH

iTrader: (2)

Hmm. Could you point me to an explanation of why? Is it a rotary thing?

salva

iTrader: (6)

I'ts kind of like retarding your timimg. You will be safer (less chance of detonation) but you will make less power because of the later ignition which is similar to higher octane in the sence that your complete combustion will occur later. I hope this helps.

Motor City RX-7

put a midpipe on and you'll break 300

hey, it's a disposable planet

t-von

iTrader: (8)

Your avatar is insane. What is that?

TimH

iTrader: (2)

Picture of a model Weta Productions made in their design for the balrog in Peter Jackson's Lord of the Rings films. Very cool bit of work.

TimH

iTrader: (2)

So, if I understand this correctly, I could expect a faster burn with lower octane, with an effect sorta like more spark advance. Might that prevent the torque rolloff I'm seeing at high RPM?

I'm guessing spark issues wouldn't give such a smooth rolloff...

cloead

You're still sequential right? If so your transistion is happening about 1000-1500rpms late.

TimH

iTrader: (2)

About 4800. Isn't normal about 4500?

cloead

My transition is around 3800.

matty

why is that?

cloead

Because that's where it is supposed to be?