But if you are reving to 8000 rpm's wouldn't you be able to put on a 3 inch pulley and get the same boost as a smaller pulley?

 

his numbers are slightly off, but not enough that they aren't correct. But the rpms are the same for the m62 or the tvs. He put in smaller print that the tvs would NOT be out of it's efficiency range.

 

no. The supercharger will indeed be spinning as fast as a smaller pulley would make it run, but the engine is also spinning faster, taking in more air every second to match the output of the supercharger. That would leave less air left in the intake manifold to produce boost.

 

Yeah the numbers would be the same for the TVS. Since were on the subject, here is what you'd have to rev the engine to to reach the 22,000 rpm mark. Pretty silly but I'm sure some are curious to know:

2.3 @ 8,096 = 22,000 rpm
2.4 @ 8,448 = 22,000 rpm
2.5 @ 8,800 = 22,000 rpm
2.6 @ 9,152 = 22,000 rpm
2.7 @ 9,504 = 22,000 rpm
2.75 @ 9,680 = 22,000 rpm
2.80 @ 9,856 = 22,000 rpm
2.85 @ 10,032 = 22,000 rpm
2.9 @ 10,208 = 22,000 rpm
3.0 @ 10,560 = 22,000 rpm
3.1 @ 10,912 = 22,000 rpm
3.2 @ 11,264 = 22,000 rpm
3.3 @ 11,616 = 22,000 rpm
3.4 @ 11,968 = 22,000 rpm

So theres a demonstration of how hard it would be to run the TVS to its maximum tested continuous speed. Damn near impossible.

By the way, the forumla I'm using is:

(blower rpm * pulley size) / Crankshaft pulley size = engine rpm

So for a 2.75" pulley this is what I'm doing:

(22,000 * 2.75) / 6.25 = 9,680 rpm

 

So to really get benifit from 8000 rpm then the tvs is needed. What about 7500 rpms? I think OTT has a tune option of 7400.

 

not really. an M62 will also see gais, assuming you have the correct headwork. You just have to be sure you're not overspinning the blower using a M62

 

Well to not over spin the m62 you would need to get a 3 inch pulley which would make only 15 pounds of boost or so.

 

^^ correct...but 15psi yields about how much torque? multiply that torque by RPM and you'll get some good power at the wheels.
its all personal preference though

 

Has anyone ever actually experience problems from spinning to high? Seems like a lot of rumors without much experience talking about what you need to spin to 8k. I'm wondering how many have tried it and had problems??

 

i ran into valve float on stock valve train once i pushed the 7500-7600 mark. (30-32k mi)

its an easy to hear sound, and the data logs went wacky.

in fact, i might still have some on the laptop....i'll take a peak.

 

I've driven/built 2 LSJ's that go to 8K daily. M62, TVS, and Turbo. No problems what so ever. People make it into a huge deal for nothing.

Both are DD street cars they use to get to work.

 

If you're going to be running a full valvetrain persay with a ported head and full exhaust.. Do you honestly think that a 3.0" pulley will net you 15 pounds of boost? Not even close.. I was running a 2.6 with a ported blower and full 3" exhaust and barely saw 17 pounds of boost..

Just food for thought?

 

I just threw a Cobalt on the dyno and let it rip. Bone stock except for ZZP 1.0 flash and injectors. Made 234WHP peak at 7200 rpm. Made it to 7500 no problem but there wasn't a point in trying it higher cause power was falling. Peak power is incredibly dependent on timing. PCM was peaking at 26 deg timing past 7k. With reduced timing (happens on it's own in most flashes when you drop pulley size) peak power is lower in the rpm band.

 

i plan to rev to 8000 when my build is finished. i was planning on using a 2.8" but i may use my stg2 pulley to be on the safe side. i have a fully upgraded supertech valvetrain ported head as well as balance shaft deletes.