Yea, I realize that, however, it does not feel like there is any significant power gain. Teh only reason I changed my cam was because it was a reground cam. Teh reground cam was off in duration on a few lobes. Teh mild change of cam was 6deg more on the intake, 3 deg less on teh exhaust with the same lobe center?
Thanks again for the help!
So that means the intake valve is opening soon after the exaust valve is closed all the way which is causing you to drop pressure. Cam selection is very important for turbo and supercharger applications and why usually the stock cam with a blower will out power a aftermarket cam not made for a blower because you need a complete burn with a stock cam to have cleaner emissions and not allow the gasses to exit the exhaust.
I assume that I am getting more air in the cylinders but since the valve is open longer on the intake ...it is filling up with more air, correct? Also, say I get the vr4 impeller and run 7psi with that unit (bigger s/c pulley). 7psi with the vr4 would yeild much more power due to the increased cfm's.......right. I want more power, not so much boost per say. So if I could get more power with the vr4 kit and run the same or close to same amtof boost, this would help with both longevity of the supercharger and more power. As far as my cam selection; i went from a zz3 ho cam (206/221 on 112 ) to a 212/218 on ll2 lca my zz3 cam did make 8psi as the stock cam did.
Last edited by Dirk Diggler; 06-15-2004 at 05:50 PM.
Speedytang,
One more question. IF I do upgrade to the vr4 impeller, Do i have to put more torque on the ball drive assembly? If so, how is this done? By adding another shim? & if I must add another shim, can I add the shim to the side facing the input shaft or do i have to take apart the ball drive unit and put the new shim toward the impeller side???
Everything should bolt together and be done since the most critical clearances are designed in the impeller and the new rear case. So do you have the other parts yet to hook it up.
OK, I bought my kit for the vr4 yesterday:D Now, I spoke with craig and he said that the normal sn series blowers should have 22inch lbs of drag on them when set up correctly. Measuring from teh output shaft, divide that number by 4.4 to get the drag from the output shaft. And the vr4 should have 44 inch lbs of force to move the ball drive unit. Speedy, what measurment do you go by when you set up the drag or psi on the ball drive and where do you take that measurment from?
I have three VR4's and the one I have never rebuilt at 55k miles I just noticed and the other two I built 10 years ago waiting on me to get a engine together for the dual unit mount I purchased way back in the day. I found my old information I had stored on specs and things I kept hold of and I was wrong on the information I quoted. I said ftlbs and it was inlbs so Craig is correct. The only thing is I have for the VR4 48 inlbs written down from the racers in the day and I took my belt off today and checking my unit with a digital torque wrench it reads 52inlbs and my 2 units I rebuilt a decade back read 54inlbs but they have not been run since rebuilt they have 0 miles on them. Sorry for the bad information. You can not check it with the belt on of course because you will be going against the compression of the engine.
Speedy, I"m a little confused of what my torque should be at the pulley ...with the belt off ofcourse ;) I thought the sn's were supposed to have 38ft lbs at the pulley? 38 inch lbs instead? And the VR4 should have 48inch lbs at the pulley?
THanks again! :)
Went thru my notes from years back and I thought it was ftlbs but my notes say inlbs also like Craig said. I will call him and we will talk shop on Monday I am leaving out of town now and 3 hour difference so I won't get to call till then.
When I ordered a set of balls from Craig he quoted inch pounds for me. He also said it needed to be measured without the seals. I assume this is because they would increase your inch pound reading with drag, when you actually do not have enough torque on the ball drive unit.
I spoke with Craig and he said the ball drive drag should equate to 44 inch lbs on the VR4 unit. SO assuming that Speedy has 44inch lbs, the additional 8 inch lbs Speedytang's unit had could be the additional drag by the seals?
Another question regarding the VR4. Is the water injection unit that came with my sn2000 sufficient cooling for the increased boost of the VR4? I do not want to run an intercooler, yet plan on either getting a larger pulley if I exceed 11psi of boost or purchasing a better water injection unit if need be.
Last edited by Dirk Diggler; 06-19-2004 at 12:36 AM.
Do you want the closeness between the "flat" back-side of the impeller & the case or closer to the inlet-hole and blades? In other words, if I had several shims of equal thicknesses under the impeller do I get better airflow by adding another shim or removing a shim?Originally Posted by speedytang
Thanks...
Closer to the inlet so less air escapes around the impeller.
I was speaking of putting more tension on the ball drive with the shims... I resolved my boost of 6-7psi to a consistant 9 psi by adding a .005 shim to the ball drive. I swear, it's almost 10spi! works perfect! I miss the vr4, but I will soon have my laughing gas 50 shot......ONCE i get my eagle 4340 crankshaft installed
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