Any dyno results for pulley only swaps?

[Jer4251]

I want to bring my ZL1 convertible power to weight ratio into spec with the coupe if not higher. Looking at things I can do to get a decent gain without a ton of money. I've been wanting a rotofab, 2" longtubes with no cats, and a 2.5" upper pulley. along with a tune I know I will be well above the stock coupe, but what can I expect power wise if I do just the upper pulley to start?

has anyone got results on only the pulley swap?

How much hp will each lb of boost generally result in on the ZL1?

[hognutz]

2.55 upper is 13psi. proabably ~550-560whp.

most people don't do just the upper alone. some people have done just the lower 10% pulley which was 540-550whp. that is 10.5psi or so

my .02 if your pulling the snout to do the upper port it and throw a TB on at the same time.

then when you get done with all your mods you will be in the 600-625 range you will need injectors too at that point as you will be out of duty cycle.

[Jer4251]

Doing the lower pulley requires the new balancer to be able to swap pulleys right? That's $750+ I wanted to avoid unless I'm missing something. Thanks for the info thus far. I would love to be 600+ who when done with these mods. Was in search of 700 @ the crank with whatever was needed.

[hognutz]

Originally Posted by Jer4251

Doing the lower pulley requires the new balancer to be able to swap pulleys right? That's $750+ I wanted to avoid u less I'm missing something. Thanks for the info thus far. I would love to be 600+ who when done with these mods. Was in search of 700 @ the crank with whatever was needed.

well they both have different pulley dia. availible. the upper ~$200 requires you to pull the snout and press the pulley on. lower you just bolt on the new balancer. ~2-2.5hrs labor.

The ATI setup is $560 for balancer and pulley. It is more money in parts but way easy on labor.

upper ratios
2.85 1-2psi ~10.5 psi
2.5 3.5-4.5psi ~13psi
2.4 4.5-5spi ~15psi


the lower being a larger diameter allows for fine adjustment but at larger pulleys you have to run different brackets and idlers.

ie 8.6= 10.5psi
9.1 = 11.5 psi
9.5 = 13psi
10" = 15sp

the speet spot for power if you are a safty concience person is 10% lower and 2.5 upper that puts you right at max blower RPM at redline. then again that is like 16-17psi so it will build heat. you can run the smaller upper if you machine the snout a bit but then you leave a little blower RPM on the table.

Some will spin the blower harder I proabably will not many story's of broken parts start with ignoring limits because people don't think they apply to them.


Pulley upper or lower, CAI are the best starter mods. If I am pulling the snout though I am porting that at that time. ~15hp there and it would be redundant labor to do it later.

that is why I have 10% lower did not want to mess with that at first so I just did rotofab, 90mm, TB, 10% lower. some will say the upper is cheaper but the fact I threw it all on in 2.5hrs was nice. woul have taken me longer to pull the snout and take it to someone to press the pulley

then I will do ported snout, upper, and injectors at a later date but that is all similar labor so it makes sense in my mind to do that all at the same time.

[KCS]

Something to consider is the increased heat. You get a twofold effect from the increase in rotor speed and also from more boost pressure. We see the IAT2's skyrocket as we speed up the supercharger, especially as the boost gets over 10-13psi. Power falls off hard as the blower heat soaks from hot lapping or just "spirited driving" around town. Typically, we recommend paying some attention to the intercooler to keep everything cool as the boost is increased. We've seen as much as 40whp gains from our ice tank and heat exchanger on cars with the 2.5 upper and 10" lower pulleys, and the power doesn't fall off nearly as bad after back to back runs.

[hognutz]

very good advice at some point you will need to log you IAT2's and make sure your not breaking the 138 degree barrier or timing will get pulled. even at that point cooler air makes more power but passing 138 degrees will pulling timing and cost power in bunches.

easiest mod extrea resivoir capacity
then you have HX upgrade, chiller, meth kit, ice tank kind of options.

I am reasearching the RX chiller myself but that is one factor of me putting on the 10% lower on to start with until I have more funds. my logs show 11.5 psi 2500-5500 then ramp up to 13.8 psi through the band instead of starting at 13spi and ramping up I my iat2's were still in line. wating for warmer day to re-log and see where I am.

for me on this car set some kind of budget and it will work itself out. I did $1500 and lower, tune, cai, tb kind of fell in line. if I would have went upper I would have been nervouse about needing cooling mods and blowing my budget. Car pulls way better.

headers are next. then down the road upper port/puley, inectors and cooling mod of some kind possibly the chiller. I am staging it is cost and trying to minimize redundant labor.

[Jer4251]

well I went ahead and did longtube headers, LS3 tb and rotofab and a tune. wasn't tuned for the TB but left it on anyways, Going to go with the ati balancer and 22.5" overdrive pulley since my headers will drop boost a little bit. and leave the upper alone. so somewhere between 11-13 psi I think. what other pulleys do I need to replace to run the large lower pulley?

[Blown355]

Originally Posted by Jer4251

what other pulleys do I need to replace to run the large lower pulley?

You will need a 50mm idler pulley. You will also need to move a couple of coolant lines over so the lower pulley doesn't touch them.

[zl1fun]

I am running the 9.55" crank ring w/ CAI and a tune. I have never had an issue with heat or fuel. just my 2 cents...but that is all about to change...I am about to make some major mods....well...someone is.