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OK, successful rebuld,however, I used to get 8.5lbs of boost, maybe even 10 if I reved to 6000rpms. I now see the supercharger petering out at 7psi? Do I need to tighten the race assembly that puts pressure on the races/ball drive unit? I am guessing that it is not tight enough? I put 20ftlbs on the race doughnut assembly. Should I put 25 or more on this part?
Well, I put 10 more ft/lbs of torque to the doughnut that holds the ball drive races in place and I am still only getting 7psi:( One thing I did do is I polished the back side of the supercharger where the impeller sits. maybe this is why I am getting less boost? Any ideas of why my boost is lower than it was orginally? I did add some trick shift hoping to see an increase, but no such luck:(
Also, I have a air fuel gauge and when I get into the upper rpm's (4800 and above) the air meter goes from yellow/green to red/ no lights :( :mad: (green is rich, yellow is stoich, red is lean and no lighs are really lean). As of now, I"m done for tonight. But I did change my fmu from a 6/1 to a 12/1 and plan on burning a chip to add fuel durring WOT. Any ideas on this part of my problem?
Just got back from changing the fmu and chip. The fuel problem is solved! But I am still only getting 7psi as compared to my orginal 8.5psi??? Any Ideas of how I can get my orginal boost level back? :confused:
You didnt do anything at all to the engine while your paxton was off at the machine shop did ya?
Brian,
I totally forgot. It's been such a long process! I had been waiting 3 MONTHS for my headers..long LONG story. Anyway, during that time, I changed my cam, however, the cam change was not very significant. I had a ZZ4 cam and changed to a comp cam. LCA on both are 112. Duration on the old cam @ .050 was 208/221 and the new cam is 212/218. The old cam was a "reground cam" and it was off in duratoin on a few lobes. So I purchased a new cam. I don't think the new cam is the reason for the lack of boost, but it would explain the loss of boost :( . And the car does not seem to have any more or less power than before :o Thanks for the reply. Also did you see what I did to the valley for the dowel's on the case of my s/c?
Yes, I looked at those pictures quite a few times. I dont know how the heck that chipped off like that. I will definatly keep in mind to machine a couple extra just incase something like that happens. I may have a couple extra machined in when I buy the vr4 half next month while its all apart.
Wait, you put new headers on your car?
My old headers cracked becasue i put header wrap on them:( I got the exact same headers, but coated inside and out. maybe the increased duration on the intake and the little decreas on the exhaust is what is causing the decreased boost? But 2.8lbs decrease over such a little change?
man. that is weird.
after you put the cam in it did you adjust the timing and such again?
yea, the cam is 4 deg advanced as my old cam was. I am considering one of two things. One, keeping the sn2000 and upgrading to the vr4 OR saving more cash and then selling the sn 2000, and purchasing an ATI procharger. I love the stealth of the sn type blowers. Can harldy hear them:D love that! But the constant maintence of the ball drive units concerns me. I have heard a lot of bad things about them, however, I have had good luck with mine, 4 years, 15k miles, but I still worry about how long this rebuild is going to last. So for now, I'm saving my cash for the ati, but using my sn2000( and loving it). In the mean time, I'm enjoying having my sc on the car:D and plan to make a decision as of how this rebuild last me.
And the one draw back of the ATI, other than the cost, is the very noticable whine :eek: yea, it sounds cool, but you have to live with it every day :rolleyes: That can get old, real old!
Remember that changing a cam duration will change the boost you see but that does not mean your building less power. PSI numbers on a gauge really mean nothing without a dyno to see the changes and 1/4 mile times are not that much help because you can't make things equal on each run.
Speedytang, I realize that a cam chance can increase/decrease the boost, however, my cam change was so small, i did not think it would matter. The only reason I changed cams was becase the cam i had was a regrind. I think the cam was off in duration in a few lobes. So i purchased a brand new cam to make sure it was a correct cam in all lobes. I spoke with craig at paradise and he said my impeller could need to be moved closer to the case of the supercharger.
My impeller is so close that a piece of paper will not go between the impeller and case. You need to take a water marker and paint the case then keep moving the impeller close till you have paint on the impeller blade and make that last shim half as thick but remember that at 50k rpm the impeller could increase on the 'SN' style blade and that is why the VR4 impeller is made so different for a tighter clearance measurement.
Well, I checked the clearance between the impeller and the back case. It was .025 so I took two of the 4 shims out, now it is .015 but have yet to check the boost level. Turns free, cranked up the engine and let it run for 10 min...everything seemed ok. Just have not had a chance to take her out for a test run:( I will later and keep you posted! :cool:
thanks for the help!
I took it out and there was no change:(
Without a comparsion like on a dyno or a few runs down a dragstrip the lower boost number could mean nothing if your power is the same. Cam, Headers, Intake design can all change a boost psi number but yet make no difference or like when I changed heads I lost 2psi but gained 48hp on the dyno. Just remember you changed other parts and so you might be chasing a boost ghost. That is why it is always said to make one change at a time to see if you decrease or increase power and that is why the magazines always show one change at a time to see one variable at a time.
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.
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??? :confused:
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.
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?Quote:
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 :rolleyes:Quote:
Originally Posted by speedytang