Jim Green's 90q 20vt - 636whp 07k

[audifreakjim]

Stock pulley,

I did the maths on all of this. At 6300 crank rpm, the alternator spins at 15973 rpm on the stock setup. On my setup, with the stock alternator pulley and TTRS crank pulley (same as Stock), it spins at 18040 rpms.

Other RPMS

@800rpms
Stock- 2028
Jim- 2290

@ 6300 RPMS
Stock- 15976
Jim - 18040

@ 8500 RPMS
Stock- 21551
Jim - 24340

Those 8500RPM values are pretty scary, but as long as they are not sustained at that level the alternators will live. My old setup was reaching those #s, as well as the other built 07K guys are not having any issues.

The real value you need to pay attention to is the idle number. The larger the alternator, the larger the minimum RPM for charging is. For these, the minimum value is ~2300 rpm so you don't have much room to use a larger pulley.

[elaw]

That... doesn't make any sense!

I don't have the stock A/C compressor, but if you look at a photo:

...it's clear the "output" pulley (the one closer to the compressor body) is smaller than the "input" pulley. So anything driven off that pulley will turn slower than if driven from the crank, all other things being equal.

I can't of course say how much slower as I haven't done measurements, but just eyeballing the diameter I'd say the difference is 10-15%. So I can't see how, when driven from the crank pulley, your alternator would be spinning slower than with the stock setup...?

[audifreakjim]

You are right, I can't read my own spreadsheet. These are based on the numbers Hank measured for me. Updated above.

The docs I saw on the alternator were still around 2300 rpms to start charging, but based on the stock rpms it may be a little lower.

In the end I decided to say screw it and just stick with the stock size because it has a nice one way clutch in it.

[pkw]

Just put AC in this race car to solve it AND stay cool.

[SEStone]

Without measuring the pulley, it looks like the same size crank and alt pulleys as what come stock on my Mk5 GTI with a 7000rpm rev limit.

You may also want to review the E46 M3 for information on maximum operating range for an alternator. The 997 GT3 is similar, I can get those numbers if you like. The M3 revs to like 8300 stock, the GT3 does up to 8800.

[audifreakjim]

My old alternator was reaching stratospheric levels and survived. The reading I did said they will go higher than ~18000 rpm limit, but don't expect additional charging above the rated amount.

If you have the #s handy it would be interesting to see.

[audifreakjim]

Plumbing is just about finished. I have been messing with organizing all of these AN lines for too long, but I am really happy with the way it's turning out. The clamps are simple nylon spacers from Made a For You

[elaw]

Wow... that is a thing of beauty.

That looks an awful lot like an OE valve cover on there... I thought those were too tall for the B3?

[ChrisAudi80]

Wow... that is a thing of beauty.

That looks an awful lot like an OE valve cover on there... I thought those were too tall for the B3?

It's porn.

And Jim can haz moar hood clearance because of CF hood w/o frame.

[alxdgr8]

I think the stock vc works fine with B3 stock hoods, it's B2 that don't clear.

[elaw]

I think the stock vc works fine with B3 stock hoods, it's B2 that don't clear.

Can anyone with a B3 confirm this? Although I love the look of the machined VCs for these engines, my bank account would be much happier if I could use a stock one. Or maybe a stock one with some creative modification...

[audifreakjim]

I have a regular b4 hood and the CF hood and both clear fine. I think a regular B3 hood would be fine, but the fuel rail I am running with a B3 hood would need changed to something different.

[ringbearer]

Looks good! I love those clamps, work great and not overpriced.

[type85]

Big Jim!
What did you coat the manifold and ex. housing with???

PS: you what they say about guys with big turbos don't you??????

[A20V200]

Big Jim!
What did you coat the manifold and ex. housing with???

PS: you what they say about guys with big turbos don't you??????

Answer: THEY MAKE LOTS OF POWER!!!!!

[audifreakjim]

The coating is from Cerakote, it's a mix of glacier silver and black

[deaner]

Looking good! Can't wait to see this thing up and running.

[audifreakjim]

PS: you what they say about guys with big turbos don't you??????

Well, that last time I was out at your track, Big Willow, a guy in a brand new 911 Turbo S car came over and said "What the hell is in that thing?"

That's generally what they say.

[ringbearer]

Bet that put a smile on your face

[90quattrocoupe]

One thing you never have to do with Jim Green. You don't have to slow down, when you pull over to let him pass, at the track. He always has enough HP to get the job done.

You also have to love the way he pushes Corvettes when they are in the twisties. Drives them nuts.

Greg W.

[highlander69]

Looking awesome Jim!!

I'm really looking forward to seeing this on the road. Seems like yesterday I was looking at
pictures of you building your 20v header

[vt10vt]

The coating is from Cerakote, it's a mix of glacier silver and black

Are you expecting this to hold up? I just used Cerakote on my manifold because my boss had some extra laying around but my impression was that anything besides Swain Tech shouldn't be expected to hold up. Although I obviously love if that were not the case.

[audifreakjim]

Absolutely. Do some research on the stuff. It's really nice. I have dropped wrenches and other things accidentally on the header and it hasn't left a scratch. This coating is stable to 2200 F or something ridiculous.

[vt10vt]

Absolutely. Do some research on the stuff. It's really nice. I have dropped wrenches and other things accidentally on the header and it hasn't left a scratch. This coating is stable to 2200 F or something ridiculous.

I have noticed it is durable to work around, I'm just really skeptical of any diy coating that is supposed to hold up to the kinds of temps a manifold sees regardless of claims. Glad you have confidence in it though, now I'm actually excited to see how it holds up!

[audifreakjim]

I didn't DIY, it was professionally done, sandblasted, acetone dipped and sprayed by OC coatings who does some awesome work with this stuff. A lot of it is on guns.