Gtm Supercharger pulley discussion

kentmo280z

On my original GTM stage 1 supercharger set up I had an 84 mm pulley.
Ran at 405 rwhp w/ 353 lbs torque. The kit came with a funky intake & 2.5 " maf pipes. The car pulled great from low end up through high rpm.
Since then , I upgraded to the stage 1.5 kit. The 92mm pulley that should have been supplied with the kit was not available at the time of purchase, so I ended up buying a Kraftwerks 90mm pulley.
The 1.5 kit intake is 3" , the supplied MAF pipes were not symmetrical in shape and are 2.75".
Reading Sam's original post on the Stage 1.5 kit, the MAF pipes were to be 3".

So, all the items were installed, had the car dyno tuned and the numbers were kind of disappointing . 454 rwhp and 338 torque. Notice that the torque went down 15lbs., which I can feel in the low end driving.
Since having the dyno done, I fabricated 3" symmetrical MAF pipes but have not retuned yet.

This is where I need help. I WANT MORE TORQUE. Is a 88 mm pulley really going to make a difference over the 90 mm which I currently have installed?
If I install my 84 mm pulley , will I be in risk of popping the engine? I could have the tuner adjust the rev limiter to 6.5 or 7k rpm if needed.
Why would a fuel return benefit this setup? I have the fuel pump relay installed and 1000cc injectors installed also.
I see some setups with an 85mm pulley, so is the 84 mm pulley that mush more radical?

Jinxx

I run with a 85mm on a stage 2 supercharger and it maxes out the supercharger at about 7.1k rpm .....I think the stage one supercharger can handle the 84..better but I'm not sure ...the 88mm is best matched to max out your supercharger at your 7500rpm ....the issue I had with my fuel system was fuel pressure drop and starvation at higher rpm larger injectors would magnify the pressure drop and I didn't want to risk the motor on what I felt was a unstable setup ..even tho some do run stock fuel system over 500 whp..I just felt safer...there is always a risk of popping the engine ...but greater risk if fuel system is at its limits ....and yes you can set limiter down lower depends on if you want to redline your car or not ..using the 84mm or the 85 mm I wouldn't run past 7k very often ..but that's my opinion .....with the 85mm on the stage 2 I got 523whp and 395 torque...if you want more torque ..it would be safer to go turbo IMO..

Another option would be to upgrade fuel system with e85 ....that would get you more hp and torque and maximize output ...if e85 is available near you

jmroy6

Im running the 85mm pulley on my stage 1 kit. I rev to 7.5k almost everytime i drive it with no issues to date, granted i upgraded to a 25row oil cooler to help cool the sc from the added heat. If you want more peak torque i would throw the stock cats on if they arent already, or run a smaller pulley for more boost.

__________________
2012 370z GTM SC

kentmo280z

Fuel starvation is what I'm concerned about. So, I'm trying to find an 88mm pulley and not have that issue. No luck so far.
What bothers me about the 1.5 upgrade is that my torque went down. Thus , the thought about using a smaller pulley.

Jinxx

The 88mm will be about 10lbs boost and the 85mm will be around 12 lbs boost ...for me that is still a huge pressure drop in fuel ... always bettter safe than sorry and the upgrade is like 600 bucks vs blown motor .. but still a lot of people are running with stock fuel setup so all a matter of preference

Jinxx

With 85mm pulley you are over spinning the supercharger specs at about 7k .... I wouldn't recommend going smaller and running to 7.5k that is a sure way to pop a motor or blow the supercharger... and the the oil cooler upgrade isn't gonna help overspinning or over boosting .... stock cats will increase torque and hp due to not losing boost pressure through the exhaust valves

kentmo280z

You're convincing me ..
What fuel return setup are you using so I can look into it?

tiller

Iam using Cj-Motorsports fuel return plus fuel hat,I believe jinxx is using it to.

For more torque the cats definitely would help, also off topic I've been researching jwt exhaust cam upgrade, they show some real nice torque gains.

kentmo280z

It's funny how my torque dropped with the upgrade kit. The increase in air flow plus the larger pulley must contribute to that issue. I do have the stock cats installed.
I see that there are a few CJM kits available. Which setup are you using?
Thanks!

tiller

I think our plastic intakes are partly to blame for the torque loss but I could be wrong,but gtr intake is an expensive upgrade.

Iam using the s1e return kit plus aluminum pump hat, our plastic pump hats have been known to crack over time after drilling thru them.

I'll be starting to install mine this weekend most likely

Jinxx

I'm also using the s1e but the top hat wasn't available when I got mine. .... not sure how the cams would effect the supercharger

kentmo280z

I've tried to find an install manual on the Se1kit so I can see what is involved, but to no avail. I always like to see what I'm getting into. I'm no fan of messing with the fuel pump. Kind of a drag pulling that thing out of it's cradle.

I'm going to have a machinist look at my 90mm pulley and see if he can machine it down to 88~87 mm..

Jinxx

It's a simple install hardest part was routing the new fuel line around the gas tank ... once that is done was piece of cake. One thing about the smaller pulleys that I liked was that you get boost sooner in the rpm.

kentmo280z

[QUOTE=Jinxx;3617539]It's a simple install hardest part was routing the new fuel line around the gas tank ... once that is done was piece of cake. One thing about the smaller pulleys that I liked was that you get boost sooner in the rpm.[/QUO
That 84mm pulley on the stage 1 pulled harder than my stage 1.5 setup even though I gained 50 hp.

Work in progress... When I get a pulley in the 88 mm range I'll be fine.

What size MAF pipes did you and Tiller receive in your kits?
Mine came with non symmetrical 2.75 " pipes. I have since made my own 3" pipes.

tiller

[QUOTE=kentmo280z;3617613]Iam not really sure my exact size maf pipes but I'll check, there slightly smaller then my throttle body's just by visual