Updated on the VR4 upgrade

Car is running so well and POWERFULL that tuning on the street is Dangerous,
this thing is Insane.
So I put it on the dyno today to try and get my AFR set (I'm using TunerCat RT tuner) anyways I made 488hp and 522Tq at the wheels with an AFR of 12.7 to 12.8 across the board, next we started to smell some burnt rubber, we thought the tires where breaking loose but it was the blower belt slipping and I can only
make 11psi now.
I can make 11psi upto 5200rpm and then it drop to 9 or 10psi all the way upto 6000rpm.
A look under the hood revealed a pile of belt dust built up on the blower.

anyways how do you guys keep from slipping the belt on these VR4 blowers,
I have an 8rib setup 6 3/4 crank pulley and a 3 3/4 blower pulley, and the belt is really tight.

My trick is to spray some VHT traction bite on my racing belt the night before but on the street it only last a couple of rpm hits. I myself am going to add another fixed pulley to get more wrap around the VR4 pulley but I am runing a 3.75" and don't have the problem till I run my 3.5" at the track.

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Originally Posted by speedytang

I myself am going to add another fixed pulley to get more wrap around the VR4 pulley .

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Thats a great Idea, I think I'm going to look into that tonight.

Quote:

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Originally Posted by speedytang

I am runing a 3.75" and don't have the problem till I run my 3.5" at the track

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Question, what rpm are you turning your VR4 at, and what Bearing preload are you using.

I'm turning mine upto 47000 +, and my preload is at 52 in/lb.

My preload is between 47-55in. Now my dual VR4 setup, I had them at 60in and they kept the boost at 15psi all the way to 6800rpm. My street unit I run a 7" and 3.75" or 3.5" and rev it to 6800 rpm. 52k+ blower speed.

Latest update:

I found the tighter I got the belt the more the belt would slip, some times it
would climb to 13psi and at 5500rpm and then it would drop to 5psi up to 6200rpm.
After taking a close look at the belt setup I noticed that I now have an alignment problem, apparently the blower bracket is flexing.

Next I tried my 4inch pulley and only tighten the belt to the point of flexing
the blower bracket.
Now it will consistently pull 11psi every time with no belt slipping at all.

I believe that with proper belt alignment and a more robust blower bracket,
with the 3.75 pulley I should be able to pull 14psi with no slipping.

Now just gota make that happen.

Louis,

Hey, glad to see you here! I've been super busy with my hectic schedule! And my tranny is out! Glad to see, or hear that you got the VR4 going strong! Have you considered getting a larger crank and S/C pullies so you can get more belt on the belt system?

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Originally Posted by Dirk Diggler

Louis,

Hey, glad to see you here! I've been super busy with my hectic schedule! And my tranny is out! Glad to see, or hear that you got the VR4 going strong! Have you considered getting a larger crank and S/C pullies so you can get more belt on the belt system?

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That exactly what I'm doing, I've ordered a 7.75 crank 8rib from Paradise,
I will have to modify it thow.
and I'm having a 4.25 pulley made buy Auto Specialties in houston.

I'm also looking at stiffening the Blower Bracket.

Quote:

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Originally Posted by LBSZ28BLOWN

That exactly what I'm doing, I've ordered a 7.75 crank 8rib from Paradise,
I will have to modify it thow.
and I'm having a 4.25 pulley made buy Auto Specialties in houston.

I'm also looking at stiffening the Blower Bracket.

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I wonder what type of changes I would see with a larger crank and supercharger pulley system? and an 8 rib. I get 9psi with my sn2000? One question for you Louis, between the two impellers, was there a difference in HP at the same boost levels? I was getting 8spi with the vr4, but the belt was slipping severly! I could hardly tell any difference between the vr4 and my sn2000m. But, my sn2000 was running perfect, the vr4 was slipping bad :freaks:

? Dirk are you seeing 9psi at the Supercharger or Intake.
Next thing just to add to the cause. Sn2000 impeller is over at 8psi and after that even if it would climb higher it becomes a huge hot air pump because you are past the CFM range of the unit.

Dirk,

Yes I do believe there is more in torque with the VR4 impeller at the same boost, this

maybe due to the fact that the impeller is more efficient so the air temp is cooler at

the same boost levels,

also I think the boost comes in much earlier and quicker with the VR4.

I could not see much of any difference between teh vr4 and the sn impeller at 8psi, but the vr4 was slipping really bad, so hard to give a ture comparision. I do have a NOS kit for my Z, I plan on using a 50 shot, maybe,,,maybe a 75, but not much more. I would like to have kept my VR4, but I really like the quite sound of the SN blowers. Maybe later I'll get a VR4 kit with the 8 rib setup.

I don't know why I forgot to add this, but for speedytang and LBSZ28BLOWN, instead of getting larger pulleys, what about a cog setup? I think this would be money well spent!

Price at $350+ and even the Novi and Vortech models with twice the bearing surface has front bearing failure because of Harmonics and they void your warranty if you use one. You do need less belt tension but the cost and noise your starting to get past the VR4 power to cost ratio and your better off purchasing a Novi. A back up idler pulley is a better solution but on my Mustang I don't have the issues that other users of the VR4 have.