88-406

Will a converted P600b to a P1SC work in an L98 application? And if not why?

Thanks Guys

KM

gcrouse

Not sure what you're asking: a P600B head unit cannot be upgraded to anything else like a P-1sc or D series, it's completely different. (Actually you can get a slightly higher step-up 3.36 vs 3.05 and swap in a helixed impeller).

However if you're talking about getting a new P-1sc and installing it in place of the P600B in an L98 kit, I think all you need is the different bracket; the rest of the kit should work. ATI currently sells L98 kits w/ P600B and will upgrade you to a P-1sc at time of purchase for an extra $150 or so.

88-406

Oh, I must have misread somthing because I was under the impression that the P600 could be upgraded to the P1SC.

Oh well, live and learn!

Thanks

KM

gcrouse

Hey, it doesn't mean you can't use the P600B; it's got the same 1200cfm capacity as the P-1sc. I was in the same situation- I already had a P600B so why not put it on! You're just stuck with the oil feed / drainback line; and you do have to work a little to gear it up for a big 383. I'm running a the smallest pulley 2.25" to get the impeller up close to 60K at 6000rpm. But I had to relocate the idler pulley, change the belt routing, and make a tensioner assist to prevent the belt slippage. The #s in my sig were from the old 2.65" pulley (with long tube runners still); haven't dynoed the new one yet. You'll really enjoy the torque :cheers:


[Modified by gcrouse, 2:44 PM 10/8/2002]

88-406

Gcrouse

The P600B I have is the high pressure kit (15psi) on a L98. I'm trying to figure out what kind of pressure It'll make on the 383?. The 383 has very large and high flowing heads. Will the heads reduce the pressure it can make?

Thanks

KM

compuvette

Any time you increase flow through an engine with a belt driven supercharger and do not increase the ratio of the blower the boost will go down. The power will probably still go up, though because more air is flowing throught the engine anyway. Don't know the exact numbers of what you are looking for. What heads do you have?

88-406

Heads are AFR 210's race ready.

km

gcrouse

With my combo I saw 8-9psi @ 5600rpm using a 2.65" pulley (ATI calls that their 12psi kit). Just remember, boost is backpressure- so a freer flowing intake and heads will lower boost- BUT INCREASE AIRFLOW CFM! And that's what you really want anyway.

At 90% volumetric efficiency, a normally aspirated 383 needs 600cfm of airflow at 6000rpm. The P600B is capable of flowing twice that: 1200cfm at 60K impeller speed; it's all in the step-up ratio. The old pulley would only spin it up to 50K where it would flow 850cfm; I've recently switched to the smallest pulley 2.25" which should get it to 57K and 1100cfm. Can't hit 6000rpm redline yet cause of computer tuning issues, but it's already reading 9psi boost by 5000rpm so I'm expecting 12psi max.

In an ideal world without intake restrictions, flowing 1200cfm while the intake valve is open vs. 600cfm, will fill the space with twice the air, at will be at twice atmospheric pressure 28psi (14psi boost), and if you add twice the fuel it will make twice the power, etc, etc. Any intake restriction will cause backpressure and make your boost #s higher, but is restricting airflow cfm into the cylinder. Boost doesn't mean much- you want AIRFLOW!

88-406

What size was your old pulley? What sizes are available? Do you just measure the pulley cross sectional (diameter)? I routinly spin my engine close to 7000rpm, if I use a larger pulley to keep the compressor speed below critical will I be ok?

My engine setup likes to wind up! and I currently shift it around 6400-6700rpm. I was hoping to be able to just touch the top end power with a supercharger.

Any recomendations on how I can/should proceed?

Thanks

KM

gcrouse

I had a 2.65" and switched to 2.25" pulley; I think they have them from 2.25" to 3.25" in .10" increments measured across the top of the ridges.

Divide the max impeller speed (60000rpm) by your hard rpm limit (7000rpm) to get overall step-up: 60000/7000 = 8.57

Check if your blower has the the 3.05 or 3.36 step-up by turning the pulley 1 turn and seeing if the impellor goes around 3 times, or more like 3-1/3. Divide overall step-up by blower step to calculate drive pulley step-up:
8.57 / 3.05 = 2.81

Crank pulley is 7" if you haven't changed it; divide by required step-up to get blower pulley required:
7.00" / 2.81 = 2.49"

Assuming your blower was 3.05 (most are) you're right between a 2.45" and 2.55" pulley; you could use the smaller one if you pick a slightly lower redline say 6900rpm:
6885 rpm * (7.0" / 2.45") * 3.05 = 60000rpm

With such a big engine I'd get that impeller as close to 60K as possible to get the airflow you need.