they can be tightened a lot. should be tight like a guitar string.

 

I tightened it a lot of turns this time. Wot for a second and 5psi and no sequel at start up

 

Then you have other issues...

 

post your setup. pulley size, headers, etc.

also, 5psi was at redline wot?

 

Don't be afraid to tight a belt with SC. There is few thread about how much tight belt on Forced induction section. Every car is diff, and there is no way to tell you "this much" is perfect, but that will given you an idea.

Edit: if you feel that your belt is tighted enough and if you flow it all the way during pulls. Even with bigger pulley or smaller pulley, you should see more than 4psi. It's good to try look for leak test and check all the couplers are tight. I think it is something very simple issue, if you can not figure it out yourself, it's good to stop by local shop. Good luck.

 

I will tightened the belt a little more. I mean it would be at a steady two to three psi sometimes four for a second. Now it holds five about 6500 so I would think its just a loose belt. I have been working a ton. So I will try that and measure the pulley. Thanks for the help guys.

 

the largest pulley (least boost) will give you more than 5psi. I think it's somewhere around 9psi with the stock pulley at 6700rpms wot.

Here's what you can do. find a long straight stretch of your belt between 2 pulleys. With 2 fingers try to twist the belt. You should be able to twist the belt about 90 degrees. By twist i mean not turn it the direction it moves, but from the front to back or back to front of the car. If it's hard to turn it 90 degrees then it's tight. If you can turn it more than 90 degrees then it's probably still loose.

Also you can check the mounting plate. Rub your finger on it and if you have black dust on it then the belt is slipping.

Do you have the r4 software for the ss box? if so hook a laptop up to the box and do a record. It will show you the MAP pressure. You could see where it levels off. If it levels off before redline anywhere then you have either a slipping belt or a boost leak. If it only shows up in higher rpm and higher PSI then it's probably belt slip.

 

A commonly overlooked area for a "stabilizing" leak is the coupler on the volute. Depending on how car back the hose coupler is on the volute taper, an area can open up and leak at a certain pressure.

We had a problem last year on our Porsche with it suddenly holding 8psi of boost to redline like a turbo even though it should have went to 15psi. We found out that even though the coupler on the volute was tight, it was far enough back on the volute that the air would pass between the coupler and the volute and then start leaking.

 

Quick question: Is the GTM pulley mod required with the revised, non-revup belt layout (79.5" belt) and 2.87 pulley? I don't want to add another pulley to the bracket if the 2.87" pulley won't slip with the revised belt layout.

 

generally yes but each car is different.

My car was fine until just after 11psi. It started slipping (identified in logs) just after 11psi. You can tighten the belt really tight but then you'll wear out bearings faster or you could use the gtm pulley mod which gives more contact area therefore you won't have to keep the belt as tight.

I would run it without the belt and log some pressures and see how it works out for you first. Then if you see the pressure flatten off after a certain point (instead of climbing the entire time to rev limiter) then you know you are slipping or have an air leak. You will have black dust all over the mounting plate and supercharger if the belt is slipping. Easy to identify.

 

thanks for the quick response man. i'm polishing my S/C pulleys so i'll probably add the GTM pulley anyway to prevent any potential slippage caused by the smoother surfaces.

on a related note, is there a way to tell if a 2.87 pulley needs to be machined down besides putting it on the bracket? i've read multiple threads where some people have to machine it down, while others do not. my 2.87 came from vortech and was bought off summitracing.com.

 

Under NO load or just spinning the jack shaft by hand the 2.87 pulley has plenty of clearance. But there are spring loaded retainers in the jack shaft housing and the shaft can move front to back under load about .020

I put thousands of miles on my car with the 2.87 and never had any problems, but about a year ago I replaced the bearing in the jack shaft and found that the Back of the 2.87 pulley had been just touching the front edge of the housing.

So I just chamfered the front edge diameter of the housing about .060

 

thanks! i got off my duff and loosely re-assembled the housing through the bracket and into the 2.87 pulley. like you said, the pulley has a bit of clearance, but its not enough for me to be comfortable. based on what i'm seeing, i'll need to machine the back of the 2.87 pulley so that outside edge returns at 90 degrees rather than the current 45 degree chamfer (see chef-j's pic below):

 

About the polishing: Take the color off the belt surface of the pulley but do not polish them or you will get quite a bit of slippage. From a distance it will look just fine if the surface is only satin metal verses polished metal. Then you can polish the face as blingy as you like

I have a vortech pulley and haven't noticed any clearance issues or anything rubbing. I just had the supercharger off a few weeks ago checking things out and there were no issues. Not sure if that will last a long time but currently 6 months of use was ok. It might be an issue like Tim stated where after wear occurs it starts to rub.

 

thanks for the tips man! i stripped & hand polished the outside face of the S/C pulley, but left most of the anodizing in the grooves. the tips look shiny, but they are just bare, unpolished aluminum - as you said, you can't see the grooves from afar anyway. i'll make sure no compound gets on that area when i finish everything up at the buffing wheel.

i did polish the smooth belt surface of the cog tensioner pulley though since its highly visible and looks like it just places tension on the cog belt.

FYI, polishing this stuff is a b!tch

 

yes, it is a pain in the butt. The fun part is doing it all again in a year when it gets faded and oxidized!

You could do like some members have done and sandblast the grooves of your pulleys to get the anodizing off while still leaving a surface that has friction. It would give a more close uniform appearance since the pulley and grooves will both be a bare metal type.

 

that's a good idea
i'm a 2-3 weeks away from the install so i'll look into sandblasting those surfaces.

 

great write-up. Why is this not a sticky?

 

it used to be a sticky forever. i guess it got old finally

 

sooooooooo....i have been holding off on this post until i was ready to start turning bolts. i'm going to install the vortech starting next Friday - any last minute advice is welcome

Build includes:
- vortech v3 tuner kit - polished, including bracket & pulleys except the parts contacting belts
- dw 600cc injectors
- walbro 255 fuel pump
- ngk iridium 1 step colder spark plugs
- tuning by technosquare reflash (i'm local)
- cosworth plenum - polished & port-matched to OEM lower intake manifold
- transgo valve body upgrade
- earl's (setrab i think) 5x16x2 tranny cooler
- powerlab oil pan spacer
- 2.87 or 3.12 pulley (depends on what tuner feels is safe)
- koyo v-core radiator
- 14" spal & 12" mishimoto fans in mishimoto shroud
- nismo t-stat
- gauges - innovate wideband & PLX multigauge (tranny, oil, and coolant temps, oil pressure, & other OBDII info - fuel pressure coming soon)
- berk high flow cats
- fujitsubo legalis r catback exhaust

i was planning to install the spark plugs, fuel pump, and injectors, but i think i will just pay the tuner to do it when i go for the tune. from what i've read, it may or may not be bad to drive to the tuner with this stuff already installed. again, any other last minute advice is much appreciated