? reduced sc pulley or reduced crank pulley or both?

[blaze6]

i've had look on the forums but couldn't find anything on this so apologies if this has already been covered, - is there any advantage to getting a reduced super charger pulley AND lightened/enlarged crank pulley? as a pose to one or the other? presumably the same performance gains and power delivery through the rev range can be achieved? with one, and there fore cheaper to get one or the other? ie: why get a 17% sc pulley with a lightened crank pulley when you can just get a 19% supercharger pulley?

[Jaw_F430]

Quote: Originally Posted by sayanthan (original)

i've had look on the forums but couldn't find anything on this so apologies if this has already been covered, - is there any advantage to getting a reduced super charger pulley AND lightened/enlarged crank pulley? as a pose to one or the other? presumably the same performance gains and power delivery through the rev range can be achieved? with one, and there fore cheaper to get one or the other? ie: why get a 17% sc pulley with a lightened crank pulley when you can just get a 19% supercharger pulley?

I would go just for S/C pulley. IMO I would avoid crank pullies

[DaFlake]

I'm in the no crank pulley camp as well as the original is a dampened and the ones on the street are not.

[BigShow]

Quote: Originally Posted by DaFlake (original)

I'm in the no crank pulley camp as well as the original is a dampened and the ones on the street are not.

What he said! The un-damped pulley's change the harmonics and have been known to cause oil pump faliure which can lead to a big bills. BMW damped them for a reason.

[captint]

I am in the other school and have already had my supercharger pulley done, but not my crank pulley done, although I have a lightened one to fit, i need a slightly different one for my new mods. I am however have my oil pump rebuilt as a precaution. I just want freer flowing revs, without the crazy expense of going down the Flywheel route

[MINIMANIAUK]

Quote: Originally Posted by BigShow300 (original)

What he said! The un-damped pulley's change the harmonics and have been known to cause oil pump faliure which can lead to a big bills. BMW damped them for a reason.

I would have said are suspected to cause oil pump failure at certain rpms and after a certain lenght of time . The smaller you go with the s/c pulley the less belt contact area you get and slipping of the belt at high rpms becomes a possibility

[MINI-Morgan]

I vote SC pulley although too small can cause belt slipping and reduced belt life. 17% seems to be the best size if you are running a bigger intercooler or its winter

[turtle343]

ive been thinking about this too. would it be worth fitting a 15% pulley to a jcw that lives in really hot weather or would that be dangerous?

[DaFlake]

Quote: Originally Posted by turtle343 (original)

ive been thinking about this too. would it be worth fitting a 15% pulley to a jcw that lives in really hot weather or would that be dangerous?

Plenty of guys down your way run 15% with no problems. I don't see an issue with it. Go above that and you need to start worrying about heat soak.

[roland2003]

..well Big Shows theory on the performance crank pulleys causing oil pump failure is completly wrong. We have had a car in running stock crank pulley and pump failed. (yep new engine) Cause? high rpm.....rev limit was set to around 7700rpm. (not a GTT conversion)
Oh this also overspeeds the SC /water in a big way too(with reduced SC pulley) ., so if you want your power to arrive at over 7K it could spell trouble.

[ScottyBoy]

Ive been running a 15% pulley an 2% crank pulley for around 10 000 miles and all seems fine and ive been thinking of re-fitting the standard crank pulley and upping the S/C pulley to 17% for the reasons that has been mentioned hear.

Im not sure which way to go so ill see what the outcome of this thread.....

[slider]

Quote: Originally Posted by roland2003 (original)

..well Big Shows theory on the performance crank pulleys causing oil pump failure is completly wrong. We have had a car in running stock crank pulley and pump failed. (yep new engine) Cause? high rpm.....rev limit was set to around 7700rpm. (not a GTT conversion)
Oh this also overspeeds the SC /water in a big way too(with reduced SC pulley) ., so if you want your power to arrive at over 7K it could spell trouble.

i have the GTT +3% crank pulley on my 210 jcw although i did have Roland fit a new oil pump , idler pulley & tensioner pulley at the same time.
I am however thinking about fitting a 15% or maybe even a 17% s/c pulley as well to further increase performance . I have recently fitted a GTT intercooler to help lower the inlet temp as i've been contemplating this mod ever since Roland fitted the crank pulley.
what are your views on this ( both Roland & other people)

[MINI-Morgan]

I did run the GTT enlarged crank for 25K miles with no problems so far but have taken it off for future projects and smoother running.

[MINIMANIAUK]

"Im not sure which way to go so ill see what the outcome of this thread....."

You will probably not get the answer , the crank /internals will have a resonant frequency ,and it is this frequency that the stock damper is designed for , this frequency has multiples at which rpms it reoccurs --- If it were below 6800 rpm ,then we would know as there would be plenty of failures already, what is not known is the rpm above this that would cause problems and how many times the engine would have to hit this frequency to cause failure.
High rpm power and running does have its limits ,including piston ring speeds ,which will no doubt be the subject of another thread

[BigShow]

Quote: Originally Posted by roland2003 (original)

We have had a car in running stock crank pulley and pump failed. (yep new engine) Cause? high rpm.....rev limit was set to around 7700rpm.

Quick question, how did you know the car's rev limit was set at 7.7k rpm? Was this measured on the dyno before the pump failed or after, or did you fix it then dyno it and then find out it was set at 7.7k rpm?

To change the rev limit to 7.7k it must have been custom remaped no? Superchips doesn't rev that high as I've seen that map taken apart. So that leaves West which runs to 7,250, Minispeed runs to 7,5k , MTH runs to 7,250... can't think who else increases their rev limit to that level so await your answer.

Are GTT crank pulleys damped then?