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MadMikeyL
05-27-2012, 06:48 PM
I tried searching and found lots of threads on belt slip theories and talking about clocking tensioners and replacing the spring, but I couldn't find anything with correct belt lengths for different OD combos. I have a 10% supercharger pulley and a 5% jackshaft pulley, and since I need to replace the belts anyway, Does anyone know what lengths or belt part numbers I should use with that combo? I realize that a 10% jackshaft pulley and a 5% blower pulley would be a better setup, but this is stuff I have accumulated over the years, so I am kind of working with what I've got here. Let me know if anyone knows what I need. Thanks.

Mike

DLF
05-27-2012, 08:13 PM
I tried searching and found lots of threads on belt slip theories and talking about clocking tensioners and replacing the spring, but I couldn't find anything with correct belt lengths for different OD combos. I have a 10% supercharger pulley and a 5% jackshaft pulley, and since I need to replace the belts anyway, Does anyone know what lengths or belt part numbers I should use with that combo? I realize that a 10% jackshaft pulley and a 5% blower pulley would be a better setup, but this is stuff I have accumulated over the years, so I am kind of working with what I've got here. Let me know if anyone knows what I need. Thanks.

Mike

I'm running the stock length belts on that exact setup.

MadMikeyL
05-28-2012, 10:39 AM
OK then. No belt slip issues or anything like that? The reason I ask is I did have just the 10% SC pulley on, and it would peg the boost gauge by about 3500rpms, and after swapping in a 90mm MAF, 80# injectors, and fixing a couple vacuum leaks, the car now struggles to build more than 10psi, and will max out at about 14psi at 6K rpms. The jackshaft belt definitely is due for replacement, so I'll be replacing both it and the supercharger belt, and I just ordered the heavy duty tensioner springs. Hopefully that fixes my low boost problem.

DLF
05-28-2012, 10:46 AM
I don't have any issues, at least with the car, that I'm aware of. ;)

MadMikeyL
05-28-2012, 10:47 AM
Cool. I'll do stock belts with the HD tensioner springs then, and we'll see what happens. Thanks.

Mike

DLF
05-28-2012, 10:50 AM
Cool. I'll do stock belts with the HD tensioner springs then, and we'll see what happens. Thanks.

Mike

Again, exactly the setup that I have.

DrFishbone
05-30-2012, 12:58 PM
Mine slipped bad with a 10% JS and 5% SC pulley and stock-length belt. I ended up getting 38 1/8 Gates belt, but even that slipped - the problem ended up being not enough tensioner travel when the belt began to stretch at high engine RPM's. I finally ground the tabs of the back of the tensioner (used to locate it properly) and re-clocked it to make the tensioning range centered again. If your tensioner has less than 1/2" travel until it hits the stop, you will probably have belt slip at high RPM.

DrFishbone
05-30-2012, 01:08 PM
Oh...BTW...

http://sccoa.com/forums/showthread.php?t=122363&highlight=belt+slip

I had forgotten about also re-clocking the crank-to-JS tensioner. I ended up having belt slip on it...fixing that finally solved the slip for good. :cool:

What I would recommend to anyone with beltslip, it to check how much travel BOTH the crank-to-JS and the JS-to-SC tensioners have. I think if they have at least 1/2 of their range to compensate for belt stretching, you should be good. Remedies would be: shorter belt(s), re-clocking tensioner(s). Also, filing the pulley rib sharp points off may help.

Maybe you're one of the lucky ones that doesn't have to do anything. :p:cool:

MadMikeyL
05-30-2012, 03:45 PM
Yeah, I had read through that thread while searching for what belt to use. Per DLFs suggestion, I got a pair of stock size belts, and I ordered the HD tensioner springs, so I'll start with that and see how it does. For both stock belts from NAPA it was only $34, so if they don't solve the problem, at least I'm not out much money. To tell you the truth, I'm not even 100% sure that I have belt slip, but I don't know of any other explanation for why the same blower with a larger intake and more OD would produce less boost.

BirdofPrey97
05-30-2012, 04:10 PM
Used the HD springs, but with the 10 rib setup it still slipped. 5% JS and 10% SC pulley.

Went back to stock pulley and slip is gone. The other option was to put a 1/4 spacer in under the SC to get rid of the slip, but my IC wasn't good enough for the 25% OD, so stock pulley put me back to 15% and the MPX builds boost very well now.

MadMikeyL
05-31-2012, 07:49 PM
Got the HD springs today. Is there and difference between the jackshaft tensioner and the supercharger tensioner? They both look the same on the car, and I have a couple spare ones laying around so I figured I could swap the springs into spare tensioners and then just swap them out on the car when I have a minute, but the instructions that came with the springs say there are differences between the tensioners, so I just want to confirm whether or not there are any differences between the tensioners before I swap them out.

DLF
05-31-2012, 11:03 PM
Got the HD springs today. Is there and difference between the jackshaft tensioner and the supercharger tensioner? They both look the same on the car, and I have a couple spare ones laying around so I figured I could swap the springs into spare tensioners and then just swap them out on the car when I have a minute, but the instructions that came with the springs say there are differences between the tensioners, so I just want to confirm whether or not there are any differences between the tensioners before I swap them out.

I honestly don't remember, but I think they're different.

Look at the p/n's. It appears that the SC tensioner ends in -KA and the jackshaft tensioner ends in -HA.

DrFishbone
06-01-2012, 07:28 AM
Doug is correct, they are different. If I remember right, the sc tensioner arm is a little shorter.

kenewagner
06-01-2012, 08:47 AM
Also, filing the pulley rib sharp points off may help.



Check that for sure. On a lot of aftermarket pullys the ribs are pointed. The belt will ride on that point and will slip. Simply file that point all around. Otherwise you can put better springs install the belt with a pry bar and it will still slip if it is riding on pointed ribs

Ken

MadMikeyL
06-01-2012, 10:26 AM
Well I checked the spare tensioners I have, and I have one of each part number, so I'll change the springs in the tensioners today and swap out the tensioners and belts maybe this weekend. Visually though, I can't see any difference between the 2 tensioners, but maybe I'll see something different when I pull them apart. I'll also check the pulleys while I am in there, and we'll see what happens.

Thanks for all the info!

MadMikeyL
06-09-2012, 01:13 PM
Well I got the HD tensioner springs installed, took it for a ride, and it made no difference. It goes to about 10psi almost right away, then slowly climbs to 14psi by 6K rpms. I was looking at it while idling, and the tensioners were both almost at the end of their travel, so today I pulled both tensioners off, drilled a couple new holes in the bracket, and clocked both tensioners to get them back into the normal range. Took it for a ride, and it is very slightly improved, still goes to 10psi and now it will slowly climb to 15psi by 6K rpms, so the boost is still way down compared to what it was with the stock JS pulley and the steel 10% blower pulley.

I guess the next thing is filing down the ribs on the pulleys? Both pulleys are from supercoupe performance, so I don't know if those are the ones that need to be filed down, or if I should be looking elsewhere. None of the grooves feel sharp, so I don't know. Any advice would be appreciated.

DrFishbone
06-09-2012, 09:56 PM
Mike,

If you can manage to clock the tensioners (especially the crank to JS) I would do that first. The try filing the ribs down a little bit. Before filing, look at the belt sitting in the pulley grooves - off the car. You should see if the ribs need ground down. I have the same pulleys, and I think the tensioners are what finally fixed the slip, but filing the pulleys helped too I think

MadMikeyL
06-10-2012, 09:55 AM
I clocked both tensioners yesterday, and it helped a little but still didn't fix the problem. Now just to be clear, when filing the pulleys, I file down the peaks of the grooves, not the valleys, right?

BirdofPrey97
06-10-2012, 11:30 AM
A lot easier to just raise the SC a 1/4 with shims.

MadMikeyL
06-14-2012, 10:19 AM
OK, at this point I have installed new belts, new HD tensioner springs, clocked both tensioners, and filed down the grooves on both pulleys, and nothing has helped. The car barely makes 15psi by 6K rpms, and is actually slower than when it was running like crap with vacuum leaks and a hacked up MAF and stock injectors. The only thing I can think of at this point is to go back to the steel 10% supercharger pulley and the stock jackshaft pulley and see if the boost comes back up to where it was, but it would be nice to be able to OD this blower more than just 10%. Any other ideas at this point?

DLF
06-14-2012, 10:30 AM
So after reading your earlier posts, I have a question.

You did a bunch of work; MAF, injectors, vacuum leaks, etc., without touching the pulleys or belts and the boost went down, correct?

If so, then it doesn't sound to me like the pulleys and belts are your issue.

Something else is wrong, and you just haven't found it yet.

What blower and inlet are you running?

What about the tune? I assume that you had to change it for the MAF and injectors.

DrFishbone
06-14-2012, 10:44 AM
Can you tell which belt is slipping?

What belt brand did you buy? Gates is supposed to be the good one.

I'm using a Gates HD green belt on mine, but I have a 5%SC and 10%JS.

Where are the tensioner stops at in the tensioning range?

With the shorter belt, mine doesn't slip. The longer belt will stretch more than a shorter...also I'm thinking that the HD belt may stretch even less as well..it doesn't have the rubbery feel like most belts do.

MadMikeyL
06-14-2012, 10:50 AM
I did all the work at the same time, including the pulleys. When I got the car, it had an MP2 blower, MP inlet, steel 10%OD supercharger pulley, stock crank and jackshaft pulleys, 85mm TB, 3" intake tube with the PCV vent not connected back to the intake tube, and a 94+ MAF with the center post cut out of it, stock injectors, stock intercooler, and there was a vacuum leak at the EGR adapter on the inlet cause whoever installed it only used one bolt. I didn't realize all of these things were wrong with it at first, and in fact the EGR adapter leaking I didn't find out until I had the blower off the car to do the injectors, and honestly I don't know how the thing even ran at all like that, let alone as well as it did, but with that combo, it would peg the boost gauge by about 3500rpms, and I never revved it past 5K because of the stock intercooler and injectors. About a week before doing most of this work, I got and installed a double intercooler from Ken Wagner, and again it would peg the boost gauge by 3500rpms and again due to the stock injectors I never revved it past 5K. After that I was waiting on the 80# injectors from the group purchase, and when those arrived, I installed the 80# injectors, a 90mm LMAF, 4" intake, 10% aluminum supercharger pulley, 5% aluminum jackshaft pulley, and fixed the vacuum leak at the EGR adapter and routed the PCV vent back to the intake, and changed the injector size in the tune (no changes to air/fuel ratio or timing), and it was after doing all of those things that the boost dropped. So aside from the pulleys, all I did was install a better flowing intake, fixed a couple vacuum leaks, and gave the engine enough fuel and an accurate meter for how much air is coming into the engine, so I didn't think any of those things could have dropped the boost, and thought if anything, they would help it build more boost. That is actually part of why I am thinking about putting the old pulleys back on, since if I do that and the boost doesn't come back up, then I know it was something else, and if I do that and the boost does come back up, then I know one of the aluminum pulleys are slipping.

DLF
06-14-2012, 10:53 AM
So you haven't hooked up a WBO2 and don't really know the A/F ratio? You didn't mention changing the MAF transfer, did you also do that in the tune?

I suspect your tune is the problem.

BirdofPrey97
06-14-2012, 10:54 AM
Try some washers under the SC to raise it up 1/4 inch and see if that helps with the slipping.

MadMikeyL
06-14-2012, 11:03 AM
Yes, I also changed the MAF transfer, sorry, forgot to mention that. You are correct, I haven't hooked up a WBO2 so I don't really know what the air/fuel ratio is, which is why I left the actual ratios in the tune alone. I didn't think the tune could cause a drop in boost like that, especially knowing how far off everything must have been before. When I get some time, I'm going to change back to the pulleys that were on the car when I got it and see what happens. If the boost stays down, then that means I need to look into the tune for the answer, and if the boost comes back up, then that would mean the problem is in the pulleys.

DLF
06-14-2012, 11:50 AM
Sounds like a plan...