Belt slip

[Jamesons Viggen]

I'm really confused. Your picture shows Dinan mounting hardware. What are you using to tension the belt?

It really looks like you are using the standard Dinan tensioner which isn't appropriate at all for belt tension. The configuration of pulley sizes you are using allows the belt to touch itself on top of the tensioner being too weak.

If you are not using the Dinan tensioner; Any RMS tensioner products do not work with the Dinan brackets. Osh uses a different charger spacing (it sit further into the engine bay than Dinan). Additionally, if you are using one of Osh's crank pulleys, they are also not compatible with Dinan brackets. The belt alignment is off by that same amount. Despite whatever he tells you, they do not work with Dinan brackets.

List out your tensioner and crank pulley setup please. I believe your issue is the hardware configuration.

My setup came to me used as a bit of a mutt, a Dinan/RMS stage 2.

I have an 6" 8 rib crank pulley, I wouldn't know by whom. The tensioner, I can't really say for sure since again, it was a used hodgepodge. I remember when I first installed the kit it ate a belt due to bad alignment that was blamed on the tensioner. So it was replaced, just don't know with what.

These are the best pictures I can get.

[Braymond141]

I'm going to say your mounting hardware and tensioner configuration are the primary issue. I would look into getting RMS brackets and maybe also consider their race tensioner setup. Your Dinan brackets are not compatible with what you are trying to do.

RMS has race tensioner just like this for S52 setups. The one linked is for S54, not sure why the S52 one was removed. http://www.racemarque.com/product/rm.../#.Xw9B4ud7kuU

Another member here ran 17-18psi with his supercharged M Coupe. I believe his power was higher than anyone that has been mentioned so far too.

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Here's the RMS Race tensioner setup in action on Kurt Hissong's race E36 M3.

[Jamesons Viggen]

I'm going to say your mounting hardware and tensioner configuration are the primary issue. I would look into getting RMS brackets and maybe also consider their race tensioner setup. Your Dinan brackets are not compatible with what you are trying to do.

RMS has race tensioner just like this for S52 setups. The one linked is for S54, not sure why the S52 one was removed. http://www.racemarque.com/product/rm.../#.Xw9B4ud7kuU

Another member here ran 17-18psi with his supercharged M Coupe. I believe his power was higher than anyone that has been mentioned so far too.

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Here's the RMS Race tensioner setup in action on Kurt Hissong's race E36 M3.

I'll look into getting the RMS bracket and tensioner. I think you are talking about Tommy's mCoupe, he has since switched to a turbo. I think he did 520whp on E85. Thanks for the help.

[Braymond141]

I'll look into getting the RMS bracket and tensioner. I think you are talking about Tommy's mCoupe, he has since switched to a turbo. I think he did 520whp on E85. Thanks for the help.

Yep. Tom just messaged me it was 520, I thought he was near 600. Sounds like you'll beat that once the belt issues are sorted, though Tom did mention the race tensioner setup would loosen up every few days. I would also add Gates new RPM line of supercharger specific belts to your list. Tom did not have those available to him then afaik.

http://www.gatesracing.com/assets/Ga...st%20LORES.pdf

I've switched to the RPM belts for my clients running standard 6-10psi setups and have been very happy with them.

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Just saw your tensioner pics. Yeah, Dinan parts are definitely the issue.

That ruler pic is not indicative of the belt groove spacing alignment. I have 6 crank pulleys here and have modeled some in CAD. I can assure you, RMS parts on Dinan brackets do not line up. I've done this on my car and a customer car too.

[Jamesons Viggen]

Yep. Tom just messaged me it was 520, I thought he was near 600. Sounds like you'll beat that once the belt issues are sorted, though Tom did mention the race tensioner setup would loosen up every few days. I would also add Gates new RPM line of supercharger specific belts to your list. Tom did not have those available to him then afaik.

http://www.gatesracing.com/assets/Ga...st%20LORES.pdf

I've switched to the RPM belts for my clients running standard 6-10psi setups and have been very happy with them.

Yeah, I talk to Tom a fair bit since I have the APE setup from him.

I did see the Gates new RPM line. Turns out the belt for the STS-V is the one I need, same size. I'll give the belt a try next time I am in there.

https://www.ebay.com/itm/Serpentine-...8/323783115347

[Jamesons Viggen]

Thanks for the help. It doesn't seem to be a real issue now, but I think as I try and run more boost and or a 2.6" pulley, the bracket issue and tensioner will cripple my plans for power goals.

I posted a wanted thread for an RMS bracket and sent an email to RMS.

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Just saw your tensioner pics. Yeah, Dinan parts are definitely the issue.

That ruler pic is not indicative of the belt groove spacing alignment. I have 6 crank pulleys here and have modeled some in CAD. I can assure you, RMS parts on Dinan brackets do not line up. I've done this on my car and a customer car too.

Thanks for the help. It doesn't seem to be a real issue now, but I think as I try and run more boost and or a 2.6" pulley, the bracket issue and tensioner will cripple my plans for power goals.

I posted a wanted thread for an RMS bracket and sent an email to RMS.

[pbonsalb]

I like that dual pulley belt wrap system and the adjustable tensioner. I had an RMS adjustable tensioner, but it was not as fancy as that one. I still think the 6.00 crank pulley will be a problem as you try to go smaller on the blower pulley, like to the 2.6 you mentioned. If you could actually spin it to 7200 without slip, you would be at 60,000 blower rpm, which is way beyond is 52,000 rated maximum. Maybe heavier duty bearings and billet impeller take care of that. I don’t know. But I think a 6.5 or 6.75 or 7.0 crank pulley would drive with less slip.

[Braymond141]

Thanks for the help. It doesn't seem to be a real issue now, but I think as I try and run more boost and or a 2.6" pulley, the bracket issue and tensioner will cripple my plans for power goals.

I posted a wanted thread for an RMS bracket and sent an email to RMS.

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Thanks for the help. It doesn't seem to be a real issue now, but I think as I try and run more boost and or a 2.6" pulley, the bracket issue and tensioner will cripple my plans for power goals.

I posted a wanted thread for an RMS bracket and sent an email to RMS.

I have an RMS V2 bracket setup I can trade you straight up for your Dinan.

[tommy1394]

Just to jump on this thread, I had to shim the RMS tensioner pulleys because they did not properly line up with the belt pulleys.

[Braymond141]

IMG_2199.jpg

[Jamesons Viggen]

Just to jump on this thread, I had to shim the RMS tensioner pulleys because they did not properly line up with the bet pulleys.

Good to know, thanks!

IMG_2199.jpg

Yeah, that's what I'll need. Hopefully I can sell my Dinan bracket so out of pocket won't be too bad.

[tommy1394]

I have some RMS stuff left over let me find the box and take some pics

[Jamesons Viggen]

I have an RMS V2 bracket setup I can trade you straight up for your Dinan.

That would be awesome. Maybe I send you like a core $$ so that way I can get yours, take mine off, then send you mine, you return the core. Sound fair?

I have some RMS stuff left over let me find the box and take some pics

Lemme know what you've got lying around.

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I like that dual pulley belt wrap system and the adjustable tensioner. I had an RMS adjustable tensioner, but it was not as fancy as that one. I still think the 6.00 crank pulley will be a problem as you try to go smaller on the blower pulley, like to the 2.6 you mentioned. If you could actually spin it to 7200 without slip, you would be at 60,000 blower rpm, which is way beyond is 52,000 rated maximum. Maybe heavier duty bearings and billet impeller take care of that. I don’t know. But I think a 6.5 or 6.75 or 7.0 crank pulley would drive with less slip.

I know my upgraded blower is supposed to net a few thousand extra RPM. Randy I think measured my crank pulley at 6.5, I don't know if that's just how he measured it. Like my 3.33" pulley was more like 3.5" when I measured edge to edge at the center

[pbonsalb]

Measure from top of groove to top of groove. Outer shoulders, if your pulleys have them, don’t count.

I have no idea how Vortech decided on the sizes - some seem arbitrary. Probably based on large volume applications, and were designed to obtain a specified boost, which required a certain blower speed, and depended on the application’s crank pulley diameter. You can have whatever you want custom made.

[Jamesons Viggen]

Measure from top of groove to top of groove. Outer shoulders, if your pulleys have them, don’t count.

I have no idea how Vortech decided on the sizes - some seem arbitrary. Probably based on large volume applications, and were designed to obtain a specified boost, which required a certain blower speed, and depended on the application’s crank pulley diameter. You can have whatever you want custom made.

My gut says it's a 6.5" pulley.

Thanks to the help above I'll have an RMS bracket. While I'm switching I'll try the new RPM series belt. I'll hold off on the 2.6" pulley until I'm on a Dynojet. I'll go back to the same Dyno and see if it's 500whp on pump with less belt slip and then E50.

[Jamesons Viggen]

I like that dual pulley belt wrap system and the adjustable tensioner. I had an RMS adjustable tensioner, but it was not as fancy as that one. I still think the 6.00 crank pulley will be a problem as you try to go smaller on the blower pulley, like to the 2.6 you mentioned. If you could actually spin it to 7200 without slip, you would be at 60,000 blower rpm, which is way beyond is 52,000 rated maximum. Maybe heavier duty bearings and billet impeller take care of that. I don’t know. But I think a 6.5 or 6.75 or 7.0 crank pulley would drive with less slip.

Found this shot of my crank pulley, doubt that helps identify the size lol.

[Master Crash]

Hey, I am getting ready to put a 2.87 pulley on my VFE stage one kit and want to know the likelihood of belt slip on a kit that has nothing else done do it. 6 rib, 80-inch belt, piston tensioner, 5.7” crank.

I was planning on getting a smaller belt and then maybe installing an idler beneath the SC pulley to increase tension/belt contact. It was a relief to me to see that another member has done exactly that, I am glad to know I am on the right track, but I want to know if I just put the smaller pulley and nothing else, what are the chances of slip and how extreme do you guys think it will be?

What is the primary cause of belt slip? Is it because the work to turn the SC is magnified as boost increases? Would you expect to see belt slip only in high RP(4500+) or would it be more related to engine load?

As usual there is so much knowledge on this forum. You guys rock. Many many years of experience in one place.

[pbonsalb]

You would see it at very high rpm under heavy load. The centrifugal makes almost no boost at low rpm. From around 3500 to 7000 boost increases exponentially. It actually makes leak boost only by at peak rpm. So watch the boost gauge as you go from 5000 to 7000 rpm. If boost stops rising, probably the belt is slipping or you have a boost leak. You can also look for black rubber debris around the blower since the slippage occurs at the blower pulley. You might get a little if that anyway so look for more than is usual.

I don’t know whether the 2.87 will cause issues or not since I never had a centrifugal running off the stock drive. I think others have reported going even smaller and claimed no issues, but that would surprise me. If you do get slip, see if there is a belt a few mm shorter that you could try. Probably someone has posted the specs before. If that does not wor alternatively, increase wrap by using an extra pulley like Jamesons did. That was a great idea.

I don’t know the boost you expect, but make sure it is within the abilities of your injectors, hfm, tune and fuel pump. What works fine on a 3rd gear pull may not be fine under the longer sustained load of a 5th gear top speed run, as I learned the hard way years ago with a modified Vortech system.

Assuming you have a stock VFE system, look into a meth system and/or intercooler. A couple of people cut down the little water to air brick inlet/outlet used by RMS and squeezed it in, one guy found a generic brick on the internet and stuffed it down where the PS reservoir is located, and a few converted to air to air intercoolers. Look at Jamesons posts for a good air to air example and posts from cj.surr for the generic water to air unit.

[5mall5nail5]

From around 3500 to 7000 boost increases exponentially

Well...wouldn't it increase linearly, not exponentially?

[pbonsalb]

My understanding is that it is exponential but I am not an engineer. RPM may be linear but the boost is apparently not. You get approximately the square root of peak boost at half peak rpm.

[Master Crash]

Well...wouldn't it increase linearly, not exponentially?

My understanding is that it is exponential but I am not an engineer. RPM may be linear but the boost is apparently not. You get approximately the square root of peak boost at half peak rpm.

In my reading I've found that the boost curve is really neither. Like Phil has said the SC will make practically no boost until you hit ~3000 RPM, then it does rapidly go up in a way that has an "exponential" appearance when you plot it on a graph. After a certain threshold it becomes more linear and then finally it just plateaus. It looks similar to the image I have attached. This has a lot to do with not only the output from the blower unit, but also from the rate at which the engine can ingest the air.

My impression is that shrinking the pulley will cause the SC to hit its sweet spot at lower engine RPM, allowing you to benefit from greater hp/torque gains in the lower end, without having to continually rev the shit out of the engine. the downside is that if you're not careful, you risk boost levels that are too much for a stock setup at higher rpm -- anything over ~9-10psi on stock internals is going to be risky without additional accommodations. You're going to have intake temperatures that are well over 60C and engine knock becomes a big problem.

A truly linear rpm-boost relationship is more apparent when you are running a positive displacement setup. I.e., roots or twinscrew. BTW I firmly believe that those forms of supercharging are far more preferable to a centrifugal, but installation requires a great deal of precision machining/fabrication, and such kits are no longer easy to find for older, (e36) generation engines. So for a weekender it's just more practical to work with the the readily available centrifugal kits that many of us have.

sigmoid_function.png

[Jamesons Viggen]

My car's been at CES awhile now. The car showed 18psi on the dyno, belt slip seems to not be an issue.

The manual RMS tensioner and Gates Race belt made things much better.

Glad to have Nick back to tuning the car. More on those results later.

The only issue left is IATs.

Intake temps were 150+ after 1 dyno run on an 81 degree day.

The APE flex fuel unit doesnt adjust timing. I didnt want to run an E85 only tune for a variety of reasons.

So the best bet is a Snow Performance methanol kit. Great way to cool down the IATs.