Ok, so I recently put my built motor in and it revs to 8k now. I have the vortech with 2.87 pulley and a custom gtm pulley mod. My boost logs show that i'm still slipping so i thought of 2 other ways to increase belt wrap on the jackshaft pulley.

There is "under" routing and "over" routing ideas. They are named based on where the belt goes in relation to the Timing gear cover.

Currently i'm running an AC Delco pulley that is 70mm for my "pulley mod". I have found that a ford focus runs a timing belt idler that is 47mm in diameter and just over 1" wide. This is just 3mm in diameter smaller than a GTM pulley and only costs 17$ from the local parts store. Not a bad idea to use while testing before dropping 100$ on a pulley. This and the GTM pulley will fit between the timing cover and the 2.87 pulley. That is an important piece of information!

First try is with taking the belt over the timing cover just like the Rev-up style. The drawings aren't to scale so i included a picture from GTM (thanks!) showing that there is more room than the picture shows. The actual setup will not run the second (lower) gtm pulley. This setup doesn't seem to have as much belt wrap based on the drawing but if you look at actual pictures of where the belts would be it is going to wrap almost all the way around the pulley (well, past 3/4). The pictures are deceiving.

Second setup is the under. It wraps the belt under the gtm pulley and under timing cover. I have included a picture of Mr. PharmD's setup which is routed similar to this just with an extra pulley i didn't include. So we know this setup worked great for him up to 17psi. Thanks for letting me use your picture!

Both of these appear to provide more belt coverage than the dual GTM pulley mod. I'm trying to decide which one would provide the best coverage and would be the smartest way to route. comments, pictures, tips are all welcome.

 

What kind of impeller speed are you getting with a 8K rev. I would estimate 70065 RPM. I have not seen a Vortech spin that high

 

it calculates out to

2.87 pulley
8000rpm=66k impeller
7500rpm=62k

3.12 pulley
8000rpm=60k impeller
7500rpm=57k

If i need to i'll lower the rpm down or change to a 3.12 pulley. I haven't rev'ed past 7500 yet nor will i be on a daily basis. If something goes bang then i'll just put an 928 impeller with new bearings. Actually it will just make my decision for turbo that much more solid. Mr.PharmD is reving his i think higher than 66k. It's a t-trim but rpm max on t-trim is only 2k higher than the Sc trim.

 

Both setup seems like it should prevent the slippage but I like option 2 better just bc u can at least put the engine cover on if u wanted to. Looks real promising and I would love to see this thing rev up to 8K. GL

 

lol, that's because it's pretty much the same as your setup! You're biased!

in all honesty i think it might be the easier of the 2 routes. You're boosting to 17psi with it so it sounds like it will hold just fine.

Why haven't you reved yours up to 8k? you have a built block, correct?

 

Binder- are your blowers internals upgraded? if not, and you want to upgrade them to bearings up to 75K! rpm , PM me. I know someone that has them ( the same guy I got mine from, awesome price!! )and there made in Italy and spin up to 75-80K rpm.

 

U got me there, lol.

I wish I built my head to rev to 8K but I was running out of funds and was trying to cut corners

 

pm sent. i hope the impeller holds up!


don't you have new valve springs? I know you probably won't pull more power up top without cams but i thought new retainers and aftermarket valvesprings would be enough to allow the motor to rev higher (without floating). I have fererra dual valve springs.

 

Ya, I was cheap and it was last minute where I found some NISMO cams for hella cheap so I just used my stock valve springs to save some down time.

 

well, there are quite a few people that are reving to 7100 on stock valvetrain so you can at least rev to that high and get better gains with the cams. If i had to choose between stock valvetrain with cams or new valvetrain and stock cams i would have chosen your route. I honestly don't have a need to rev to 8k and i probably won't but on rare occassions.

 

You really dont have to worry about over reving the Vortech Blower . As long as the belts are slipping [ and you cant stop it unless you go to a cog set up ] the blower isnt reving higher . All SC systems seem to act a little different , but some where between 11 and 15 psi the blower gets so hard to turn the belts always slip . On my cog belt set up the blower was so hard to turn at 17 to 19psi it would snap the belts off of it .

 

ya, i'm not too concerned about it. It will either live or die. I've had it to 7600 with the 2.87 pulley so far and it's still working fine. The amount of time it will actually spend over the limit is so short i dont think it's going to be a problem. If i was running long amounts of time at full boost then i could see them fail. For now it would be lucky to have that rpm for longer than 1-2 seconds.

booger, i replied to one of your old threads about slipping on belts. I was trying to think of a way to measure and log impeller RPM. If we can do that then we can effectively calculate the amount of slip. If at 7000 rpm and X-pulley setup it should see 55k rpms (arbitrary numbers). If we log the impeller only moving 45k rpms then we know the belt is slipping.

That way we can honestly say "i spun the impeller too fast". I would probably bet money on your train of thought that the impeller is never reaching the calculated speeds.

 

My main problem is lack of traction on my power steering pulley. I plan on doing the Timrod setup or the "over" design because it seems to put more belt in contact with the power steering pulley along with sand blasting it for good measure. Speaking of sand blasting, summer 08' I had issues with slipping on my jack shaft pulley even with the GTM upgrade. I took my 2.87 pulley to a friends and we sandblasted it and slippage has not been a problem though you are running way more boost than I am it will still help. Don't forget to tape the areas of the pulley you don't want to lose paint before you do it though. Also, did you polish your supercharger bracket? How did you get the paint off if? I'm sure it's much the same way of polishing our intake manifolds where you first have to remove the rough cast and bring to a mirror finish with abrasives and finally buff and polish. I have all the pads abrasives and high speed tools to polish aluminum.

 

Just off the wall thought from looking at the 2 drawings.

Can you eliminate the pulley that is right in the middle (lower left of the vortec bracket), and use the factory idler pulley (if equiped)....seems like you would get more "wrap" around the closest 2 turns with it in either way you went....granted it will make the belt have to be a little longer, but when you are at the length that belt is already does it really matter if you add 5 more inches.

Just a whacky thought.
Tom

 

I've never had a problem with the PS pulley slipping. It doesn't have a lot of resistance so i wouldn't see why it would slip.

Also, if you look closer, my "over" isn't the same as the timrod setup. mine moves BOTH sides of the belt over the timing cover therefore providing more wrap on the vortech pulley.

about the polish: that's Mr.PharmD's car so you'll have to ask him. mine is still black. I would assume it's the same as any aluminum. Sand off the anodizing then start polishing.



are you talking about the setup where both belts run over the timing cover? first picture. I think i see what you're saying, take out that idler on the vortech plate and extend the belt around the stock idler. That would work if you had the idler machined smooth. it would be a smooth side pulley. It would add more wrap to the steering pulley. I guess it would help but i haven't been having problems with the steering pulley so i would be out the cost of having that stock idler machined smooth.

 

I seem to get some squealing for about a minute or two after start up when the engine has sat overnight. Kind of embarrassing when someone wants to hear your car start up when you have a few guys checking out your car over some beers in my garage. I thing I may have an allingnment issue and will look into this when I pull my supercharger and bracket out for my revised pulley configuration. Do you happen to have the belt size needed for your "over" design. Is there any grinding needed? I think the timrod setup might require that main bracket bolt to be ground down. I think I am going to polish my bracket too, mine has a couple of small scratches but the mirrior finish just looks so much cleaner. Any tips on this Mr. PharmD? Thanks in advance.

 

the bracket is anodized so you have to strip it off before sanding & polishing. a diluted solution of lye is the easiest way to go, but Heavy Duty Easy-Off will work too. spray it on, let it sit for 5-10 minutes max, then scrub the annodizing off with medium to rough grade steel wool (brillo pads work too, but are slower) & soapy water. you'll have to repeat the process a few times since the anodizing is pretty tough, but you'll eventually get to a clean surface to work with.

as for the polish, since its a big flat plate, grab a 8-9" long sanding block and work your way up from 400 grit to 2000 grit. finish it off at the buffing wheel if you have one, or just hit it with some Mother's Polish. a pic of my bracket before i finished it up on the buffing wheel is attached.

 

I'm TimRod,
Here is the link to the Belt Modification Thread.
https://my350z.com/forum/forced-indu...-solution.html
I'm making over 14Lbs of Boost @ 7100 rpm, and 2.87, and over 35,000 miles with this setup, and only had to adjust the belt 2 times.

Hay Jeff, when are you going to get that car on a 1/4 mile DragStrip?

 

19.5 psi @ 6400-6500 rpm. 2.61 or 2.62 pulley on vortech setup. dayco belt. no slippage, no breakage. gtm pulley mod ftw

 

Thanks for the advice! This is exactly what I will be doing!