Hey

This is driving me mad, just wondering if anyone could offer any support?

Basically the question is 15 or 17% pulley...

I have a GRS Intercooler, colder plugs etc but my main reason for concern is that I plan on adding a cam and altering my rev limiter to around 7600rpm.
Will the 17% generate too much heat at those sort of rpms? Would 15% be better?

Just for the record... I dont track my car, it would be for fast road use only.
I have a scan gauge installed to monitor temps.

So 17 or 15?

Thanks for ANY help!

 

Go with 15% for daily street use.

 

go 15% and the ns1 cam and you will fly

 

17% is fine even if you track the car some.

 

Split the difference and get the M7 16% pulley. That's what I run - when it's running.

Kevin

 

17% all day long

 

I think you will find that a 17% at 7600 will do you more harm than good if you hang around those revs for any sustained amount of time. The supercharger will be generating insane amounts of heat, which not even a GRS can effectively bring down. If that's what you choose I would suggest water/meth for additional cooling. Just my $.02.

 

When we went from a 15% to a 17% pulley we had a GP intercooler and the RMW big valve head with an 8000 rpm limit. It was really cool to take it to redline. It would scream like a banshee . After switching to the 17% pulley, Jan lowered the limit to 7200 rpm because he said anything higher would be counter productive with the 17%.

 

I just cant believe there is actually that much difference between 15 and 17?!
Surely its a couple of mm at most, how can that make SUCH a difference?

The difference between 7200 and 8000rpm for instance - is a 10% difference for a 2% pulley size difference.... just seems a bit extreme?

I must admit... I want the 17% pulley for the low down power it gives etc and for the amount of time which I spend above 5500rpm is very limited I would be tempted to say that it would be safe... but Im just after getting other ppls opinions

How much heat difference at 7600rpm is there between a 15 and 17% pulley?

 

to go dat high i think its recommended that you need at least 440cc injectors and ARP head studs...

 

Why would you want a 17% pulley AND increase the redline? It's counterintuitive.

For a daily driver, 17% is fine--you're going to increase boost/torque down low. At higher RPM's all you're doing is spinning the supercharger faster than it can handle--you're not getting any improvement in performance, just generating a bunch of heat.

So go 17%, enjoy the improvement down low, and leave the red line alone...Or go 15%, maybe a cam, and increase the redline so you're getting measurable improvement at higher RPM's.

Personally, I'd recommend the former--really doesn't make much sense to run the engine at higher RPMs like that around town; if you're going to the track, that's another story....

 

futureal33 are you running a stock head? I dont think it would be safe to raise the rev limiter that high on a stock head, somebody correct me if i'm wrong, that just seems pretty high.

 

The RPM limit does depend on the valve train. I run a 17% and meth kit and make power all the way to the 8000 cutoff. If we reved it higher it would keep going.

This has been gone over before, the OBD temps from the Scangauge are off as much as 40F in fast transients. I see 180F on the outlet side of the IC( OBD says 135-140) and that is not the way to make power unless you can cool it properly.

 

It really depends a lot on how hard you drive it, and how often you drive it that way. I probably redlined my Mini about 10+ times each time I drove it. Worked fine with no problems for 5 years.

BUT fate finally caught up and I blew my engine this past May running 15%+2% + 7200rpm GIAC setup with JCW 380's.

On my new setup I'm going with 15% + RMW cam + 400cc injectors + good tune (not reflash)

 

What part finally gave out?

 

i'm running 17% and 7400 rpm, so go for it
if it gets too hot you might loose a little top end power, big deal
but for a street car your not going to be hanging around 7k for long in any gear, unless you want to get a ticket or worse
so dont let the "wise people here" worry you about it, and enjoy all that extra surge between 3-6k that a 17% delivers on daily basis

 

Are you running an uprated Intercooler?

 

with the 17% for 30,000 miles +
ive been oem 6months,
forge 9 months,
gtt 1yr
and grs 6 months, to date

so tried a few options
still not blown anything up apart from a clutch rocking 280+ bhp with other mods

70mph on motorway 3k = 6 degrees above ambient all day long,
its static heat soak not pullies that ramp up my inlet temps

disclaimer..... but it is a street car

 

people would be shocked if they "KNEW" the real temps of what comes out of the supercharger, after the intercooler and the REAL temp inside the intake manifold

what you see on your scan gauge isn't the real temp

 

Amen to that Jan.
Heat is an engine killer. That's why I am running a 16% pulley. Haven't had a tune yet - missed Jan in Louisville - but I intend to have the redline raised when tuned. A 16% pulley is right for me - gives me a little piece of mind. However, do whatever you want to. Just be aware of the potential problems.

Kevin

 

How about giving us some data or something for us to look at? If it is any good you may move a couple of your meth systems.

 

Can't keep them in stock anyway..... what's the point in giving our competition data that they should have anyway but don't

We have posted some of it in old threads but nobody takes notice, they want to believe what people with no data tell them

 

i also want one but dont understand pulleys.. what is better a 15% or 17% which lets more power etc?

 

It really depends on what other mods you have done or have planned for the engine, and how you drive--are you heading to the track, or just want a little more oomph for around town?

 

mines just stock atm but i wana get some mods and make it fast im just a noob and dont know where to begin. and no i never go to the track just around town