What are the differences between a 15, 16, 17 & 19% pulley..?

[Reedy]

Could someone please explain to me what the differences are between 15, 16, 17 & 19% pulleys.

Cheers

Chris

[luca]

The first difference is the sizes. Each pulley is a reduced size compared to stock ie 15%reduced size, 17% reduced etc.
When the pulley gets smaller the power is shifted lower down the rev range. Also the smaller the pulley, the higher the boost. But with running a high boost with the e45 supercharger it can make it run too hot and make it inefficient and ultimately lose power if it gets too hot.
I ran a 15% on mine as i wanted to be on the safe side and when i had it fitted it was in the middle of summer so was quite warm.
Most people on here run the 17% which seems to be the best for good midrange power.

[MiniPetrolHead]

I have a 15% reduced pulley, i remember the day i had it fitted, i drove it very slowly to a petrol station (i was very low on fuel) put £20 and nailed it out of the petrol station (after paying obviously), i was grinning like the cheshire cat!

Alex

[Reedy]

I have a 15% reduced pulley, i remember the day i had it fitted, i drove it very slowly to a petrol station (i was very low on fuel) put £20 and nailed it out of the petrol station (after paying obviously), i was grinning like the cheshire cat!

Alex

lol

[Reedy]

so i guess if your running a 15% pulley you can run it with stock I/C ...but a 17% or 19% requires a uprated I/C..??

I've been looking at the M7 16% pulley....why do they not have a 15 or 17% one..??


Chris.

[R53mcs]

Just that they chose to go inbetween the 2 most common sizes. Webb motorsports do a 11 or 12 % as thats what they chose. Alta did 15 and 17 etc and GTT do 17% ... its each tuners preferred size. Many say avoid 19% pulleys, however with the right kit to keep it cool and fueling to mtch it the 19% can be very very fast... as seen on perms BBR car

PS my stock IC car on a 15% with optimised bypass valve, was cooking in the summer.... a JCW GP IC and an M7 scoop really helped this. Even the stock MINI S pulley can cook the IC in the summer, so if you go up to 15 get colder plugs and get an IC as soon as you can afford it as you'll then see the real difference between stock and -15 etc. If you get a 17% then defo do the IC at the same time IMO, although I have seen very very good times from 17% GTT 220 (no IC upgrade) on a hot day at the drag strip!

[luca]

I still ran bigger intercooler on mine with 15% pulley

[Jaw_F430]

so i guess if your running a 15% pulley you can run it with stock I/C ...but a 17% or 19% requires a uprated I/C..??

I've been looking at the M7 16% pulley....why do they not have a 15 or 17% one..??


Chris.

I woudn't recommend running any extra boost with stock I/C.

[Reedy]

Good job i got a GP I/C coming

[Jaw_F430]

Good job i got a GP I/C coming

Top work