GTM Stage 1.5 s.c. tune issue
 

After installing an 88mm pulley ( replacing the 90mm pulley) on my GTM/ Gamma stage 1.5 supercharger I had run into tuning issues.
Because the intake runs parallel to the cat. converter on the stage 1.5 setup, the intake was drawing in hot air during the dyno pulls. The air was so hot that the tuner could not get numbers over 400 hp.
I've rescheduled a tune where I'm going to pull off the metal under tray and I'll have a commercial floor drying type fan underneath the car also to try to cool the air.
My tuner was concerned that the 88mm pulley was overspinning the sc, as the pulley made 11 psi . Thoughts on that?
He now has he car neutered until the new tune... Ughhh

That's strange my intake is also close to the cat converters... I'm sure it pulls in hot air as well ... shouldn't keep you under 400 hp tho.... the 88mm pulley should be match almost perfect maxing supercharger at the same time you hit 7.5 k engine rpm... 11lbs is about right

I never ran into that problem with my kit.
I ran the FI exhaust with in line 100 cell cats

If your running the stock cats, I could see a possible problem.

The 88 mm pulley is perfect and the 84 mm is close to SC overspeed depending on your RPM limit.

Which rotrex unit is utilized in the stage 1.5? Cuz I know like jinxx and my sc units maxed out with the 85mm pulley but they are c38-91s I believe, our cars put off a lot of heat, main intake temp downfall is the stock tow bar blocking our intercoolers, but that moving.

Have you entertained using ecutek at all ?

The stage 1.5 unit is a hybrid ... it's the stage one charger with a stage to intake housing ..and I think it's actually has more effiency that the stage 2 ......if I remember the research correctly when I bought mine... I haven't noticed a heat issue and I dynoed my car in July and it was pretty hot

Just back from my Tune on 3-20 17.

Still have disappointing numbers. 455rwhp/ 337 torque ,90mm pulley

Maybe someone can spot an issue.

First of all , My original stage 1 tune was 405 rwhp and 355 lbs torque , 84mm pulley

Now, with the Stage 1.5 kit

This kit includes 3" intake, 4.5 inch filter, 3" maf pipes, 90 mm pulley.
(Tried an 88 mm pulley also, but tuner could not get that pulley to make good power. )
93 octane pump gas.

Wondering why the numbers, especially torque are so low compared to others.
My tuner suggested HFc's ( I would have to have resonated, noise level wise) to help flow more air out. Then maybe I could use the 88mm pulley also.
So there's my situation...

Not really helpful to you but how did you get a hold of the 88 mm pulley I'm getting the 1.5 upgrade this week but he couldn't get the 88 only the 85 or 90 so I'm gonna get the 90mm also my maf pipes are 2.5 inch my tuner said 3 inch wouldn't matter

Ya, that pulley is hard to find. I sourced it through a member on this site.
I'm going to try to use once I figure out my issues.

I think the older stage one kits had a flaw in the intake piping ....too much restriction to the supercharger and not getting over 8 lbs regardless of pulley size. If that's the case the 90mm will be more matched to the charger. The smaller ones may be spinning the charger but the restriction is choking it out through ing the tune off ... the flaw was corrected by new filter location straight back close the transmission the old design location was 2 filters in the front left area with 90 degree bends ......where are yours located?

I have the stage 1.5 with the filter under the car in between the cat and the tranny. It's the lack of torque that is puzzzling.

That is strange I thought with a 88mm pulley and 11 psi you should be in the low 500s maybe that's on E85 maybe you could try that E85 does cool down the car really well torq number is kinda low but I wouldn't really worry about a 10 torq loss our cars always lacked in torq in general I'm sure on the streets with air flowing under your car the torq is way higher

I can definitely feel a loss of torque from my stage 1 kit.. I'm really disappointed.
I just ordered F.I. high flow cats and am going to slap that 88mm pulley back on when the cats come in. I'm going to flow some air damnit!! lol

Push comes to shove, I may try ecutek . ( now with uprev) I have sunk a boatload of $ in this car.. I want it to make sure it is running at it's best!

That is really strange ...with the that setup you should be able to get close to 500 whp with the 88mm and smaller....the 90mm pulley numbers look about normal....super chargers don't produce high torque numbers ....I'm only at 395lbs TQ with 522 whp...on 93octane and uprev.....everything else is stock on my car as well ...still stock cats and exh

Ya .. it is strange.. Your torque is great! Most 1.5 setups that I've read on here are 475 to over 500 rwhp. and much higher torque than my setup.
I'm curious, what size are your maf pipes? I'm trying to duplicate the original 1.5 setup, but gamma sent incorrect pipes and they had no idea which ones that I really should have gotten..

The 88mm pulley put out 11 psi and the 90mm put out about 9ish

My 85mm was 12.5 lbs ....I have 3inch maf pipes.....you could be pulling timing for some reason and losing TQ and whp I'm not sure about the details of the 1.5 compared to the stage 2 but if you are getting 455/337 with the 90mm pulley that seems about right ...maybe ty another tunner

You running stage 2 kit ? I thought 88 was max with the 1.5 85 would be over spinning

I think Jinxx has a stage 2 kit

I'm running stage 2 kit .... both stage1 and 2 supercharger units max out at 90k... 88mm pulley put you at 90k around 7500 rpms... the 85mm is over spinning it a little at 7500 rpms (it's like 95k) ... but I normally don't redline the car ... I wanted the boost earlier in the rpm

I think the pulley is the difference in my stage 1 kit compared to stage 1.5. I used an 84 mm pulley in stage 1. It pulled hard in the low rpm range. My 90mm pulls hard after 4k rpms...

I believe the sooner you get the boost in the rpm range the more TQ you will get ....but even with 84/85 mm pulley around 400 ish is prolly the max .......if you want more TQ you would need to go to e85 and tune for it ......or convert to a turbo kit
Still tho with what you have you should be 480-520 whp with 84mm and 350-390 TQ

I just talked with another tuner , and he suggested changing the crank pulley rather than the supercharger pulley. He thought that the larger, lighter crank pulley would spin the s.c quicker, put less stress on the front of the engine and make more low end torque.

I've not seen this discussed here???

I'm not sure how exactly that would make more torque. If it's the same size pulley but lighter, I would think the only difference would be on initial throttle tip-in. If it's larger, wouldn't it spin the sc less? Wouldn't it need to be a smaller pulley to spin it faster?

I just found this from 1 Slowz "the factory crank pulley is 146mm

SO an 88mm pulley would be 146/88 x 7500 x 7.5 = 93324rpm "

So a larger crank pulley appears to make the s.c. spin faster.
A) My setup 90mm pulley w/ stock crank 146 mm pulley -146/90 x 7500 rpm x 7.5 ( SC gear ratio) =91,250 rpms
B) Using a 150mm crank pulley, 90mm s.c pulley 150/90 x 7500 x 7.5 = 93,375 .
This is if my formula is correct???

THINK I'LL DISREGARD THE CRANK PULLEY IDEA.... DON'T EVEN KNOW IF DIFFERENT SIZES ARE AVAILABLE..

Yes a larger crank pulley will increase the rpm of the supercharger. If your belt is slipping already though I don't know how much this will help. The reason people go with smaller supercharger pulleys instead of larger crank pulleys is because the larger crank pulley will also make everything else spin faster(alternator, ac comp) which has parasitic loss on the motor. You may net 7hp out of a larger crank pulley and 10hp out of a smaller supercharger pulley. This is my understanding someone correct me if I'm wrong

I ended up having Seb from Specialty Z do a ECUTEC remote tune. I reinstalled the 88mm SC pulley and did logs as he instructed. I also changed out my Bosch EV14 1000cc injectors and replaced them with ID 1050x, which was recommended by Seb.
He did a fantastic job!! The car runs much better, with more torque, from the ECUTEC remote tune than with the Uprev Dyno tune!!

All is good in the world!!

i'm running 1.5 kit with uprev and i'm at 450whp and i think 90mm pulley, i forget TQ