I want a smaller pulley for my M62.
What boost difference is there between the 3.0" and 3.1" pullies?
How small of a pulley can the 'stock' tensioner accomadate without slipping issues?
What would be a good fuel injector size to accomodate down to a 2.85" pulley?
What boost would be seen with a 2.85" pulley?
Is there an equation to figure this out?
Anyone dyno with a 3" or 2.85" pulley?
generally for every .1 less its 1psi, if you go down too much in size a smaller belt works better
whats your stock pulley size
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
3.34" is the stock pulley size
I have the pulley boys setup with the ZZ performace tensioner bracket.
I'm intercooled and with the stock pulley I saw 10 psi, the 3.0 13psi and the 2.8 15psi I'll forewarn you that the 2.8 is pushing it. I threw a rod at the St louis bash with the 2.8 pulley installed. 13.9@104.88 was my run prior to the rod snappage. The run where I snapped the rod was still a 13.9 coasting to 94mph at the finish. I'm not sure what size you can go down to without any belt slipping but most redline/cobalt users say 3.0 to 2.9 before they notice some slip.
12.770 @ 111.99 Intercooled Eaton M62
Maybe I'll shut up and be happy with the 3.1" pulley.
But I know I'll want more power, so I can't decide if I should go ahead and invest in HPTuners and make the 2.9 or 3.0 work with larger injectors...
Is there a way to prevent slip, can I coat the pully in something?
3" pulley has no slippage whatsoever. If your worried about the pulley slipping you can buy the oversized tensioner pulley for 20 bux from Intense. Billetflow also makes pulleys that are grooved to supposedly prevent slipping as well. The stage 2 belt is also available from GM for about 40 bux and that seems to be fine down to 2.8" other then youd have to cut off a rib. Lots of options... Surf the cobalt or redline forums all the info is there.
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Unless you intend on buying a new ECU you can't invest in HP tuners, they have do not support the eco reflash. The inherent flaw with that program is that the ECU and BCM will then have different VIN and that will create a whole different level of problems.
With the Eco reflash the 3.0 shouldn't be a problem with the injectors you have, beyond that it getsreally expensoive in a huryy.
(Airtonics isn't using the eco reflash he had a standalone when he used the 2.8)
Marchi1 wrote:With the Eco reflash the 3.0 shouldn't be a problem with the injectors you have, beyond that it getsreally expensoive in a huryy.
So you can drop to the 3.0 and not change anything? I always wanted to ask that question! I run rich now anyway so I would think when GM developed the reflash they tuned it pretty rich to save the engine.
With the smaller pulley...up the boost to 13psi and you'd have a nice A/Fs huh?
Eh...old man with a Corvette now...it was bound to happen sooner rather than later right?
I will tell you for sure as soon as I can confirm. But it make sense, the TMAP is a 2 bar, and GM has a very conservative tune. Looking at the stage 1 and stage 2 kits for the cobalt there is no computer reflash associated with them (if I remember correctly)
Marchi1 wrote:I will tell you for sure as soon as I can confirm. But it make sense, the TMAP is a 2 bar, and GM has a very conservative tune. Looking at the stage 1 and stage 2 kits for the cobalt there is no computer reflash associated with them (if I remember correctly)
Stage I has the reflash but Stage II doesn't. So I don't know if that would work for us or not by not getting it flashed again or tuned?
That's my question...can we run the 3.0 pulley and do nothing else? I have ordered my wideband and I guess I can order the pulley as well and post up some info? May do that in the next few days and just see...nothing else I could sell the pulley I'm sure!
Eh...old man with a Corvette now...it was bound to happen sooner rather than later right?
Other than running it and looking at the AFR I dont really think anyone can tell you for sure, if you didnt have the GM reflash and could use HP tuners that opens things up alot more to expand
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
I emailed ZZ Performance about this. On their website they say their 3" pulley is good for 6.5k rpm shifts and the 3.1" pulley is good for 7k shifts.
They did say with the stock fuel system they recommend the 3.1" pulley.
I'd like to try the 3" pulley and see what afr's I get.
you have my opinion
Edited 1 time(s). Last edited Friday, September 29, 2006 9:34 AM
Admiral Jedi wrote:I emailed ZZ Performance about this. On their website they say their 3" pulley is good for 6.5k rpm shifts and the 3.1" pulley is good for 7k shifts.
They did say with the stock fuel system they recommend the 3.1" pulley.
I'd like to try the 3" pulley and see what afr's I get.
Why would the diameter of SC pully affect when you shift? Do you overspin the SC if you shift higher on a smaller pully, or what?
15.3 @ 89.97mph, 14's on the way?
Ian Brydon wrote:Admiral Jedi wrote:I emailed ZZ Performance about this. On their website they say their 3" pulley is good for 6.5k rpm shifts and the 3.1" pulley is good for 7k shifts.
They did say with the stock fuel system they recommend the 3.1" pulley.
I'd like to try the 3" pulley and see what afr's I get.
Why would the diameter of SC pully affect when you shift? Do you overspin the SC if you shift higher on a smaller pully, or what?
not until a 2.5" pulley. 2.6" is minimum you can go without overspinning the blower at all...
14.425 @ 97.833 mph stock + GMPP s/c on drag radials.
Airtonics, I have that video saved. I used to watch it every day.
Did you not have wheel hop at the top of your first gear?
With my stock pulley my tires start chirping around 4,000 rpms in 1st at wot.
Tires are decent with a good amount of tread left on them.
I usually get wheel spin vs hop however I used to get wheel hop prior to the following items:
Rk sport upper and lower engine mounts, poly trans bushings and control arm bushings. The tires help a lot too I'm srue 235/40/17 hankook ventus rs2 z212 on an 8" wide rim.
04blackfire, the 2.6 was going to be my next item before the mishap. I'll eventually throw a 2.4 or 2.3 on there someday
12.770 @ 111.99 Intercooled Eaton M62
Im doing a full build, hoping to break well into 300 hp. If Id quit seeing Phlatcav getting all this cool stuff like the battery/intake idea, etc. I could get on it and focus on the engine.
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Airtonics wrote: I'll eventually throw a 2.4 or 2.3 on there someday
Some say "Bold", but I say the man is insane, but he also knows what he is doing, and I will let him continue to be a test bed and help in any way I can.
Lets build a motor this winter and see what happens...
Im currently running on my 2.9" pulley. Would going to a 2.8 make that big of a diff ya think? Im to scared to try it
From the 3.0 to the 2.8 I noticed a large increase. Keep in mind my car was probably beat on more than most. My daily driving habits are terrible, I almost never see vaccume. I also autoX'ed the car, did some open track days (hours of beating on it) and at least 70 track passes if not more.
Basically without the 2.8 pulley I think the motor would have gone, eventually due to fatigue. My best trap with the 3.0 pulley was 101.66, with the 2.8 pulley I was trapping almost 104.88, a very noticeable difference.
12.770 @ 111.99 Intercooled Eaton M62
