Since I had the autometer boost meter installed, I tested to see if different brand of fuels will have different effect on performance...

So far, I tested with the Petro Canada and Shell V-Power, each for 3 weeks, what I found is:

Petro Canada 94 octane > Max boost = 13~14psi at redline.
Shell V-Power 91 octane (Some said it is 93) > Max boost 16psi at redline.

I remember last year when I was on track, I used the ELF octane booster and my MCS reached 16psi before redline...

So the fuel does have relation to SuperCharge boost?

 

It seems to me that you should be boosting alot more than that with a 17% pully... I would imagine your gauge is off... You never know, though....

 

How could the fuel affect the boost? There's no "dump valve" so the only thing generating pressure is the RPMs and vehicle speed? Sounds more like measure-to-measure variation

 

16psi with a 17% in second gear at redline is about right

 

Then why do i get more than that wth my 15% at redline?

 

:D cos ur special

but seriously, atmospheric conditions and other variables are important.....

temperature, even mods like air intake (greater boost), headers and catback (less boost if there's better flow), and even the height above sea level all make a difference...

just out of curiosity, what boost do you see at 2nd gear and at what redline? stock or modified?

 

This is true, I remember when we are at 38C since last month, my Max boost was only 14~15psi, now actually with cooler weather (18~20C) I get 16psi (redline, 4th gear) or a bit higher boost (which cause the DSC light on).

I still don't understand why, but it is true that when I used the Petro Canada 94 fuel, I can never go up to 15psi... In summer, it was even worst... It can only go up to 11PSI! Then I switch back to Shell V power and will never go back....

 

ok i think i might understand why.....(someone correct me if i'm wrong)

your supercharger is driven by the crankshaft. If you're making more power (which you would with both better fuel and colder weather), you're spinning up the SC faster, and thus have more boost earlier (at say 3-4kRPM) then you usually would. When you're upping the engine speed, you up the supercharger speed. Since roots blowers make boost post-SC (because they're trying to cram more air into a smaller space), the more boost you start with, the more air you're increasingly cramming in, and thus the higher boost you make

yes, no, anyone?

 

Thats kinda true, but the S/C is belt driven to the crank, which means it pumps a certain amount of air directly proportional to what rpm the motor is at. At 2500rpms the s/c will always be spinning at the same rpm. The only variants are atmospheric, so things like your IAT's etc... dictate the amount of PSIg you'll make. I boost 2-3psig more when the temp changes from 90 degrees F to 50-60F.

 

yeh, but what i meant was if you are making more power, you get to a certain rpm more quickly. If you take longer to hit a certain rpm the air that has been jammed into the pre-IC horn gets used up before more air gets pumped in...if you're spinning it up quickly, the car has less time to use up all that air, and thus have more boost? Is that at all correct?

 

Air density....

 

What Brand Of Gasoline Gives The Most Boost? I Want More Boost. Can I Add Octane Booster To Get More Boost?

 

Because MTH software raises the redline to 7200rpm...

The higher you rev the supercharger, the most boost you get.

 

Yea, air density and not octane should be the controling factor. Only if the lower octane is causing pre-detonation and the ECU retards your timing to avoid it would (lowering maximum rpm in the process) would octane be a factor, but as you are reaching redline with both kinds of fuel, I suspect that all the difference is made by the atmospheric conditions.

 

fuel density?

 

Exactly

 

at 15 pulley produces 14.5lbs of boost - yr gauge is off.

 

What Is The New Redline When The Ecu Retards The Redline?

 

What I think is, it could be the fuel quality makes different? I remember that in Fifth gear (UK car channel) they did test different kind of fuels with different kind of cars. For NA cars, the quality of fuel will not make any different, but as for any F/I cars, it makes almost a 50BHP different if I remember well (with a Subaru STI).

So, could it be the quality of fuel which makes the supercharge blower runs slower, which cause less boost? I did test both Petro Canada and Shell V power for a while in same condition (Shell V power was test under 34C and almost 80% of humidity ).

But at the end, I am still not sure...

And yes about the MTH does help the redline to run over 7000~7200 rpm, my 16psi + happened right after the 7000rpm The MTH tuner is a great product.

 

the denser the charge the stupider or just slow?

 

Turbo's are different. They run on exhaust gases. More complete combustion (due to the higher octane number) means hotter, and thus faster exhaust flow with more volume, which in turn means faster spinning turbines, which means more boost...