Supercharger belt slip? And how to eliminate

[Morritse]

About 5k miles after I changed my lower pulley on a hot day I noticed my supercharger pitch not climbing as it should. I can't think of anything but belt slip that would cause my blower to spin more slowly than it should.

https://youtu.be/_L9Z5EcMe5g

I have a correctly sized belt and good tension on it but this is still occurring. I'm boosting about 4psi less than I should be. Tends to happen more on hot days after driving for a whole when my engine bay is heat soaked.

Can anyone confirm that this is indeed belt slip? And how to fix it. I've heard CTS upper pulleys slip?

[bajan01]

What pulley size(s) and what belt size? 6 rib or 7 rib belt? Also what brand belt?

[Morritse]

What pulley size(s) and what belt size? 6 rib or 7 rib belt? Also what brand belt?

Gates 7pk 1325 with a 57/196.5
Didn't slip a bit for the first several thousand miles. I guess once it slips once it glazes the rubber causing more and more slip. So I think the belt is done (if this is indeed slip)

I have a contitech 7pk1335 waiting to be put on to see if it will rectify the issue

[Adamantium]

Is it a gates performance rpm belt?

If not, get one from Issem.

[bajan01]

Gates 7pk 1325 with a 57/196.5
Didn't slip a bit for the first several thousand miles. I guess once it slips once it glazes the rubber causing more and more slip. So I think the belt is done (if this is indeed slip)

I have a contitech 7pk1335 waiting to be put on to see if it will rectify the issue

I think that 1335 will be too big (loose). I run a 1338 on my 57/203 setup. Check the underside of the belt and see if the ribs are breaking up.

[Morritse]

I think that 1335 will be too big (loose). I run a 1338 on my 57/203 setup. Check the underside of the belt and see if the ribs are breaking up.

They appear to be in good condition visibly but there's quite a bit of black rubbery debris that comes off when I run it.

[bajan01]

They appear to be in good condition visibly but there's quite a bit of black rubbery debris that comes off when I run it.

Sounds like that belt is falling apart. I always buy two at a time but mine have been holding up well.

[Whitee]

About 5k miles after I changed my lower pulley on a hot day I noticed my supercharger pitch not climbing as it should. I can't think of anything but belt slip that would cause my blower to spin more slowly than it should.

https://youtu.be/_L9Z5EcMe5g

I have a correctly sized belt and good tension on it but this is still occurring. I'm boosting about 4psi less than I should be. Tends to happen more on hot days after driving for a whole when my engine bay is heat soaked.

Can anyone confirm that this is indeed belt slip? And how to fix it. I've heard CTS upper pulleys slip?

Probably not your issue but I’ll throw it in. I had the same issue when I was having intake flap issues. Do you have loss of power as well?

Doesn’t look like it based on video but figured I’d ask. I know you know a lot about these cars so disregard if there is no loss of power.

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[Morritse]

Probably not your issue but I’ll throw it in. I had the same issue when I was having intake flap issues. Do you have loss of power as well?

Doesn’t look like it based on video but figured I’d ask. I know you know a lot about these cars so disregard if there is no loss of power.

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Loss of power due to less boost. It pretty much feels like I have 4PSI less of boost. Nothing extremely drastic. I don't have any codes, I recall you having them right?

[bajan01]

Loss of power due to less boost. It pretty much feels like I have 4PSI less of boost. Nothing extremely drastic. I don't have any codes, I recall you having them right?

Log it and see where your boost is compared to before.

[Morritse]

Log it and see where your boost is compared to before.

Its at 17 compared to 21 before.

[bajan01]

Its at 17 compared to 21 before.

Yeah it certainly appears that the belt is slipping. I think that P3U had a similar issue a while back which turned out to be a disintegrating belt.

[Morritse]

Yeah it certainly appears that the belt is slipping. I think that P3U had a similar issue a while back which turned out to be a disintegrating belt.

I'm just wondering what caused it. Once it starts it makes sense that it will create a positive feedback loop, but the belt only had maybe 7k miles when it started. Maybe it got some coolant or oil on it which started the vicious cycle?

Anyways. I talked to issam. They're coming out with a gates RPM 1325 belt soon, so I ordered a bando one which will hopefully hold up until then.

[bajan01]

I'm just wondering what caused it. Once it starts it makes sense that it will create a positive feedback loop, but the belt only had maybe 7k miles when it started. Maybe it got some coolant or oil on it which started the vicious cycle?

Anyways. I talked to issam. They're coming out with a gates RPM 1325 belt soon, so I ordered a bando one which will hopefully hold up until then.

I believe that the extra rpm kills the belts because ultimately you have a bit of slippage and it simply gets worse over time.

What tune are you running and has anything changed recently tune-wise?

[Morritse]

I believe that the extra rpm kills the belts because ultimately you have a bit of slippage and it simply gets worse over time.

What tune are you running and has anything changed recently tune-wise?

Nothing changing tune wise. It started when I moved from 80° to 110° weather. Probably didn't help it.

[Black s5]

I run the same pulley sizes 57/196.5 and use gates rpm 1310 from issam.No belt slip.1325 belt from exelarate performance was slipping and showed the same symptoms.black fine debris as it started to wear in.

[MSq5]

New belt probably fixes the problem, but maybe the tensioner spring is weaker than you realize. They are pretty inexpensive. Might want to replace it while you have the belt off. Only one center bolt to remove to get it off. I don’t recall if the bolt is too long to get out without service position.

[Morritse]

I run the same pulley sizes 57/196.5 and use gates rpm 1310 from issam.No belt slip.1325 belt from exelarate performance was slipping and showed the same symptoms.black fine debris as it started to wear in.

Thanks for helping me confirm. The 1325 felt super tight honestly, how did you manage to get a 1310 on there

[bajan01]

Thanks for helping me confirm. The 1325 felt super tight honestly, how did you manage to get a 1310 on there

Lots of muscles and sliding the belt on to the tensioner pulley last as it doesn’t have a lip. I do have to say that the 1310 has to be super tight as I ran that on my 57/183 setup and thought that it was tight for that.

[Chris@EPL]

The Gates RPM 7PK1300 works on the 183mm crank pulley and have a lot of people also use them with a 187mm, so the Gates 7PK1310 could work on a 196.5. Tighter is better than looser.

[vpls4]

Nothing changing tune wise. It started when I moved from 80° to 110° weather. Probably didn't help it.

Hey did you move to the Phoenix area?

[Morritse]

Hey did you move to the Phoenix area?

No, school in bay area > live in Central cal :(

[RWD2quattro]

Hey man, I feel your pain. I bought my ported blower from a member here that sold his car and had a CTS pulley. At first seemed ok but after a few thousand miles I'd get belt slip and loss of boost, ask Ro. In the last year I've gone thru probably six belts, long story short, get rid of that POS pulley. I just went to 034 yesterday and had mine swapped, guess what, no more slip and gain my boost back .

I had two Bando belts that it chewed it up (posted pic on thread for belts), went thru several Gates 7PK1325 Horizon same result were it was cutting them in between ridges (look for a faint white line). Glad I got rid of it.

[Adamantium]

In case anyone isn’t clear, there’s a difference between the gates belt and the gates rpm belt.

Normal gates belts are common place for many applications and are no good for our application. The rpm versions are a completely different animal.

[RWD2quattro]

^^ True but Gates RPM belts are not available for 7PK1325 hence why we run the Gates Horizon from your neck of the woods .

https://assets.gates.com/content/dam...t-newbrand.pdf

[Morritse]

Hey man, I feel your pain. I bought my ported blower from a member here that sold his car and had a CTS pulley. At first seemed ok but after a few thousand miles I'd get belt slip and loss of boost, ask Ro. In the last year I've gone thru probably six belts, long story short, get rid of that POS pulley. I just went to 034 yesterday and had mine swapped, guess what, no more slip and gain my boost back .

I had two Bando belts that it chewed it up (posted pic on thread for belts), went thru several Gates 7PK1325 Horizon same result were it was cutting them in between ridges (look for a faint white line). Glad I got rid of it.

I am wondering if it's more that there aren't any high performance belts made in the 1325 size. I never had a problem with my upper pulley when I was on a 179/187mm crank with RPM belts.

[RWD2quattro]

I went DP (194mm) at 45k and I already had 034 upper pulley. The Gates Horizon (EPDM) 7PK1325 belt came from Issam with his crank pulley.
I put 45k miles on that belt with no slip. At around 90k miles installed the ported blower with CTS pulley and had nothing but slip/chewing belt issues and that has been my experience and was the only thing that changed on my car belt related. From what the belts show (forensics), you can say, one of the ridges on pulley wasn't cut properly (tolerance) and too high as it was shinier and cutting belts in between ridges heating the belt and causing screeching/slip and fast deterioration. My car has 101k now and glad I got rid of that pulley, dealt with it for 10k miles. Please remove and inspect your belt thoroughly for these signs. Good luck with whatever you decide to do, just trying to help you.

I have a spare 034 upper pulley on my stock charger still, I can let you to test it out, if I'm wrong, keep the pulley.
Belt info.
https://assets.gates.com/content/dam...t-newbrand.pdf

[Morritse]

I went DP (194mm) at 45k and I already had 034 upper pulley. The Gates Horizon (EPDM) 7PK1325 belt came from Issam with his crank pulley.
I put 45k miles on that belt with no slip. At around 90k miles installed the ported blower with CTS pulley and had nothing but slip/chewing belt issues and that has been my experience and was the only thing that changed on my car belt related. From what the belts show (forensics), you can say, one of the ridges on pulley wasn't cut properly (tolerance) and too high as it was shinier and cutting belts in between ridges heating the belt and causing screeching/slip and fast deterioration. My car has 101k now and glad I got rid of that pulley, dealt with it for 10k miles. Please remove and inspect your belt thoroughly for these signs. Good luck with whatever you decide to do, just trying to help you.

I have a spare 034 upper pulley on my stock charger still, I can let you to test it out, if I'm wrong, keep the pulley.
Belt info.
https://assets.gates.com/content/dam...t-newbrand.pdf

Well damn. I'm down to buy it from you. Give it to Ro or something I'll pick it up from him haha

[RWD2quattro]

Does anyone have a pulley puller I can borrow to help a brotha out?

[Adamantium]

Think there’s a 7PK1325 gates rpm on the way. I’m waiting for one.

[Morritse]

Think there’s a 7PK1325 gates rpm on the way. I’m waiting for one.

Ya. He told me April ETA

[Whitee]

Loss of power due to less boost. It pretty much feels like I have 4PSI less of boost. Nothing extremely drastic. I don't have any codes, I recall you having them right?

Yes, I did have soft codes. Used a bottle of that miracle spray and everything cleared right up.


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[bajan01]

So I’ve been doing some reading...

The Gates RPM belts are designed to stretch less than the standard Gates belts and therefore you will tend to see higher boost levels when using them under the same conditions as if you used a standard Gates belt.

Having said that, they are more brittle than the standard belts and may actually be prone to breaking more than a standard Gates belt.

I am currently using a standard Gates 7PK1338 belt with my 57/203 setup and all seems well. I am seeing 24psi on my analog boost gauge. I don’t seem to be seeing any stretch with the belt even though it should stretch more than the RPM belt. Maybe this is because it’s on very tight...I don’t know. The recommended belt for this setup is 1345 but I started with a 1340 and ended up at 1338. I don’t think that I have more than 5k miles on any belt yet as I have gone from bone stock to software only, to single pulley, to dual pulley, to bigger dual pulley, to finally 57/203, within 18 months...all of which have required a new belt. I am approaching 5k on this current belt (Gates 7PK1338) and it’s holding up well.

Remember too that with a high pulley ratio you will be spinning the belt faster and any slippage will be magnified. All of this theory of stretch vs. minimal stretch goes out the window on worn belts, misaligned pulleys, poorly manufactured pulleys, etc.

[Morritse]

Yes, I did have soft codes. Used a bottle of that miracle spray and everything cleared right up.


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Ah so the crc GDI actually worked?

[Morritse]

So I’ve been doing some reading...

The Gates RPM belts are designed to stretch less than the standard Gates belts and therefore you will tend to see higher boost levels when using them under the same conditions as if you used a standard Gates belt.

Having said that, they are more brittle than the standard belts and may actually be prone to breaking more than a standard Gates belt.

I am currently using a standard Gates 7PK1338 belt with my 57/203 setup and all seems well. I am seeing 24psi on my analog boost gauge. I don’t seem to be seeing any stretch with the belt even though it should stretch more than the RPM belt. Maybe this is because it’s on very tight...I don’t know. The recommended belt for this setup is 1345 but I started with a 1340 and ended up at 1338. I don’t think that I have more than 5k miles on any belt yet as I have gone from bone stock to software only, to single pulley, to dual pulley, to bigger dual pulley, to finally 57/203, within 18 months...all of which have required a new belt. I am approaching 5k on this current belt (Gates 7PK1338) and it’s holding up well.

Remember too that with a high pulley ratio you will be spinning the belt faster and any slippage will be magnified. All of this theory of stretch vs. minimal stretch goes out the window on worn belts, misaligned pulleys, poorly manufactured pulleys, etc.

I don't see why belt stretch would cause a difference in boost. No matter how long the belt is you're still get 3.x revolutions of the SC pulley per revolution of the CP

[bajan01]

I don't see why belt stretch would cause a difference in boost. No matter how long the belt is you're still get 3.x revolutions of the SC pulley per revolution of the CP

If it stretches and that stretch induces slip it would. This could also cause premature wear on the belt and the slippage would only get worse.

[Morritse]

If it stretches and that stretch induces slip it would. This could also cause premature wear on the belt and the slippage would only get worse.

Ok I understand. BTW any way to tell you have misaligned pulleys other than "looking"?

[bajan01]

Ok I understand.

I’m just speculating here. There are so many pr combinations using different pulley vendors, different ECU and TCU tune vendors that it’s difficult to pinpoint the root cause of some of these issues.

For example, I had an interesting phenomena that would occur right at 5k rpm with my old tune. Everything pointed at temporary belt slip as I could feel less acceleration and then a surge right at 5k rpm. The belt was fairly new and on inspection all of the ribs looked good. I switched vendors and the problem went away, running the same belt. Acceleration is most certainly better having not touched the belt or tensioner.

[bajan01]

BTW any way to tell you have misaligned pulleys other than "looking"?

I don’t know. I installed my pulleys and belts myself and I am confident that they are installed correctly and therefore should be aligned if manufactured to spec. I’m running an EPL upper pulley an iAbed Fluidampr crank pulley and ring. Zero problems from day one. I have heard of others having belts jump with similar setup but unless they somehow received a poorly manufactured pulley (hard to believe as these are not hand turned and there is quality control that goes into the process) the installation process or a bad belt would be the only other contributing factor.

[Morritse]

I don’t know. I installed my pulleys and belts myself and I am confident that they are installed correctly and therefore should be aligned if manufactured to spec. I’m running an EPL upper pulley an iAbed Fluidampr crank pulley and ring. Zero problems from day one. I have heard of others having belts jump with similar setup but unless they somehow received a poorly manufactured pulley (hard to believe as these are not hand turned and there is quality control that goes into the process) the installation process or a bad belt would be the only other contributing factor.

Going off what RWD said, I do believe him when he said his upper pulley is bad. The shiny ridge in combination with going through 6 belts a year with the only change being the upper pulley is quite convincing.