Belt slip on Magnacharged LS1?

[streetk14]

I just got the new 122 Magnacharger running on the LS1 in my '67 Camaro last weekend. I've been driving it around with the Magnuson base-tune, and am trying to make sure all the bugs are worked out before I take it to the dyno.

I seem to be having a belt slip problem at higher rpms or in the lower gears where the rpm increase is very quick (1st gear especially). I am only seeing about 6 psi max on the boost gauge, and that usually drops down as I get to the higher rpm range. There is a noticable amount of belt dust on my accessory mounting brackets, so I'm almost 100% sure this is a belt problem. The fact that I'm losing boost is what makes me think something is wrong.

This is the larger, 122HH blower, and I ordered it with a 1:1 rear pulley drive ratio so that I could run a larger front pulley for better belt contact. It has a 3.0" front blower drive pulley right now, and I am running the stock f-body crank pulley. I have seem some similar engine combos with the 122 blower, and I was expecting to see around 10 psi with these pullies.

I am running a Street & Performance front accessory drive system, and am wondering if this is my problem. I did upgrade the tensioner to a very heavy-duty tensioner when I installed the blower. The tensioner takes a 3 foot breaker bar to compress, so it is by no means weak. It seems to put good tension on the belt, but I don't really like it's location in the system. I have tried several different belt lengths and I switched to a Goodyear Gatorback belt, which did not get rid of the problem.

The other thing I think it could be is the lack of belt-wrap around the crank pulley. From looking at pictures, my setup has less crank pulley belt contact than a factory GTO or Vette has. I tried to route my belt a more efficient way (to get more wrap around crank), but I could not locate the proper length belt to do that. Apparently, all the belt manufacurers have a gap in their sizing from 115-117". I need something aprox. 116" long to route the belt the way I wanted.

Mark @ S&P is sending me an adjustable idler pulley bracket that is supposed to replace the tensioner on my accessory drive. He thinks this will cure the problem, but I wanted to get some input from you guys. Here is a picture of what my belt drive setup looks like. This is what I have, except my tensioner is slightly different.

What do you think?

Andy

[DeltaT]

Looks nice, Andy. Looks like you do have an opportunity to add an idler pulley right before your blower in that hole in the bracket I see, above the water hose attach point. That would give you some more pulley wrap with a minimum of fuss, and might help. You could increase your wrap so it almost touched the belt on the idler after the blower.

I have a 383 with a Vortech T-trim, and just finished adding an idler just like I am describing, and it helped. One disadvantage you have is a 6-rib setup, but the new adjustable idler pulley bracket might allow you to put more tension on the belt.

Jim

My site: http://home.mindspring.com/~jim_fisk/id1.html

[HILROD]

The crank wrap is small, maybe too small. What if you used an idler in that unused hole next to the alternator like Delta-T sugested and re-routed the lower belt. Also it looks like you have a Gatorback belt. Those have way less contact patch with all the grooves they have. Bad for supercharged applications.

[camcojb]

The crank wrap is small, maybe too small. What if you used an idler in that unused hole next to the alternator like Delta-T sugested and re-routed the lower belt. Also it looks like you have a Gatorback belt. Those have way less contact patch with all the grooves they have. Bad for supercharged applications.

I agree. Although it was a debate on the Lightning boards most people had much better luck with the standard Gates belts vs the gatorbacks.

Jody

[CarlC]

Andy,

I'm glad you got it up and running.

You may want to contact Magnuson but they may be limited on how much they can diagnose. However, I have a piece of info that may be helpful. During planning I discussed using the smaller ASP underdrive pulley with their engineering guys. Every one of them said stay away because of the reduction in belt wrap length. The stock F-body setup has 180* of belt wrap on a large pulley so there is a lot of belt length engagement, whereas yours has what appears to be about 120*. I think Hot Rod just did a Magnuson/Dutwieller GTO (same accessory drive) and he runs boost levels that we are looking for.

There is a picture in the LSX forum under a recent thread for painting LSX engines of mine and you can see the crank belt wrap.

It also appears that all of the accessories are driven from one belt. Combine reduced crank belt wrap with the number of idlers (they take power to drive as well) and belt direction changes (yup, more power) and there could be a problem. The stock A/C is a separate belt which reduces loading on a stock application, so who knows how much more that effects a single-belt arrangement.

You might try putting a some machinists bluing on the supercharger and crank pulley and observe which one has it rubbed off. I don't know if this will work but it's worth a try.

If you stick with this accessory drive you may have to try and fab an idler between the PS and WP pulley.

[streetk14]

This is a real picture of my engine, which is a little different than the one I posted above. The other pic was mainly to give you guys a better idea of how my belt was routed.

I think my setup has a tighter wrap around the blower pulley than in the other picture. The blower idler and water pump pullies almost touch, so it's as tight as it could be there.

As some of you said, I don't like the belt wrap on the crank pulley either. I was going to route the belt more like this picture below (ignore the alternator on the upper drivers side), so the belt goes around the idler pulley before it goes to the power steering. I could not locate the proper belt to do this, so that idea is out. If you look at the pic below, it seems to have a good amount more belt contact on the crank.

[streetk14]

It also appears that all of the accessories are driven from one belt. Combine reduced crank belt wrap with the number of idlers (they take power to drive as well) and belt direction changes (yup, more power) and there could be a problem. The stock A/C is a separate belt which reduces loading on a stock application, so who knows how much more that effects a single-belt arrangement.



Hey Carl,
I forgot to mention that I had my A/C compressor bypassed right now. I thought the same thing (too many accessories on one belt) so I just went straight from the alternator down to the crank pulley.

S&P makes a different compressor bracket that will move it back to run off the smaller A/C belt groove on the factory balancer. They recommend this for higher horsepower applications, but I obviously have other problems since my A/C is out of the picture at the moment. I will most likely move the compressor and run a seperate belt for the A/C, but I want to solve my real problem before I spend $$$ doing that.

Andy

[streetk14]

Here's another shot of my actual motor. There's not much room for any changes up top near the blower, but I have thought about adding an idler pulley (maybe attach it to the water pump) to the system. The closer to the crank pulley, the better. I'd like to be able to get at least 180 degrees of belt wrap around that pulley.

Also, I thought I'd throw this out there as well. There is a company who makes a larger, 8" crank pulley. This would increase belt contact and eliminate the possible need for a smaller blower pulley to increase boost. Just another idea.

Andy

[CarlC]

Jody's belt change is likely the best, least-expensive route to try. Some belt dressing might help as well.

[streetk14]

Jody's belt change is likely the best, least-expensive route to try. Some belt dressing might help as well.

I tried a couple Gates belts, and it made no difference. The Gatorback seemed like it actually may have helped a little, and that was what all the Magnacharged GTO guys suggested I run.

At this point, it seems like my problem is the belt wrap around the crank pulley. The new bracket that is on it's way will allow me to route the belt the way I want, and it should use a shorter belt that is available at the parts stores.

I am going to give this new part a shot, and if the belt is still slipping I may look into moving the alternator and power steering to the factory locations. Then I would be able to use one of the high performance belt tensioners on the market that bolts in the factory location. I like the looks and quality of my accessory drive system, but it really wasn't designed for a supercharger and it limits me on what parts I can use/change.

I'll be sure to let you guys know how that new bracket works when it gets here (either monday or tuesday).

Andy

[DeltaT]

Looks like you have room for a dedicated, 8-rib supercharger belt setup there. Those really let you crank up the belt tension. I was shocked by how much tension they wanted me to run but have gotten used to it. The belt puts out a nice note like a guitar string when plucked now...

Jim

[streetk14]

Looks like you have room for a dedicated, 8-rib supercharger belt setup there. Those really let you crank up the belt tension. I was shocked by how much tension they wanted me to run but have gotten used to it. The belt puts out a nice note like a guitar string when plucked now...

Jim

Unfortunately, it would require some major changes to put a dedicated, 8 rib system on there. This is something that would be nice, but really shouldn't be needed for what I'm trying to do.

There is a company (east coast supercharging) that makes a LS1 8 rib conversion kit for the main drive belt. This would be nice, but is fairly pricy as well. They also make an extra-heavy duty belt tensioneer that is supposed to work very well. The problem is that that tensioner won't work with my accessory drive.

I'm going to have some faith in this bracket that is on the way. Some guys swear by solid tensioners, others have reported problems, so I'm rolling the dice here. If this deoesn't work, I'll likely go with the tried and true OEM alternator & bracket (low on drivers side) and factory power steering pump mounted above it. Then, I can use that ECS tensioner (or the one supplied by Magnuson) and I should be in good shape.

Andy

[CarlC]

Andy,

Slight change of topic.

How did you route your PVC system?

[streetk14]

Andy,

Slight change of topic.

How did you route your PVC system?

I used part of the original F-body PCV line that I had. I ran it from the factory location at the rear of the driver's side valve cover to one of the big barbs on the blower near the bypass valve.

Then, I just connected a hose from the passenger side valve cover to the barb on the throttle body (like the factory setup). I might get a nice breather to replace the passenger side hose, but it's not really a big deal right now.

Andy

[CarlC]

I want to stay away from breathers. They always spew gasses and make a mess.

Side note. PCV gas ingestion has actually shown an increase in blower efficency. More than one supercharger sent back in for service with a bunch of miles and carbon buildup on the rotor surfaces has shown an increase of sealing ability. Still, it just seems wrong! Oil in the combustion chamber is a whole other story.

[streetk14]

I want to stay away from breathers. They always spew gasses and make a mess.

Side note. PCV gas ingestion has actually shown an increase in blower efficency. More than one supercharger sent back in for service with a bunch of miles and carbon buildup on the rotor surfaces has shown an increase of sealing ability. Still, it just seems wrong! Oil in the combustion chamber is a whole other story.

I've heard the same thing about the oil mist from breathers, but there is at least one on the market that I know of that was designed to eliminate that problem. I think it was Arizona power and Sound, and I found it over at ls1gto.com. Does it really work? That I don't know for sure.

I've also heard that the blower acts as a vaccum pump and does a good job of evacuating crankcase pressure. As long as the oil isn't getting into the combustion chamber, I'm fine with it. It seems that a lot of LS1 guys are having problems with oil in the intake and smoke from the exhaust from the PCV system. I never had any problems when I was running my nearly-stock LS6, and I have yet to notice any smoke with my blower. My motor never used any oil either, so maybe I'm the lucky one (my motor is low-mileage, though). A lot of GTO guys are running breather "catch cans" to eliminate the oil in the intake. The way I have mine set up right now seems to be working well, so I'll most likely keep it that way.

Andy

[THX 138]

might have to change the rotation of your water pump and add another idler pully. With the Saleen now I'm on Ford boards alot and they always put two pullies next to the blower pully for maximum contact.

[HILROD]

It looks like you'd only need an idler in the un-used boss next to the alternator, to set it up that way. As long as you can get a belt that size it looks good. Your water pump would still be rotating correctly. If the belt is upside down on an accesory it is reverse rotation, teeth down is standard.

[deuce_454]

i have had luck applying track-bite to the belt on a procharged car with belt slippage issues....

[Texas Hotrod]

Really cool looking pulley system. Just a little too complex for my taste.
The problem seems simple to me, if that is in fact a spring loaded tensioner.
The tensioner is having to withstand the total forces generated by the blower, water pump, alternator and the AC. The PS pump is on the "pull" side of the belt, everything else is on the "slack" side. The tensioner needs to be between the WP pulley and the AC compressor for maximum effect. I guess there is a reason why GM uses a seperate belt for the AC on the LS engines, it frees up space for proper placement of the tensioner.

Don't ever use belt dressing. I have to deal with that headache on a regular basis. People here use it on squeaky belts, making the problem 50 times worse. Then it's a mess trying to clean all the gunk off of everything.

There has to be a better way to reroute the belt, eliminate an idler (or two) and add a manual belt tensioner.