Carl Fausett

Non-intercooled = Stage 1
Intercooled = Stage 2

Basically:
1) compression-check your motor and make sure your cylinders are within 10% of each other.
2) fix your engine oil leaks

Rule of thumb: if you can clock 1,000 miles on your 928 and use or loose less than 1 pint of oil (1/2 quart), your engine is sound and a good supercharging candidate.

CMW

As smog always seems to pop up... one of the virtues to either the Centrifugal or Positive displacement blowers... in the end most of these kits can litteral once set up be removed... restored... smogged and installed again in a day.

I agree with Carl on the power to weight your light 80 928 will scream with 320 RWHP

bcdavis

Now we just need a PD blower kit for the early cars...

I know it's being worked on, but at this point, unless he wants to buy Goldmember, or invest in John making him some manifolds, quick Carl and Murph are the only ones offering a "kit" to boost the older cars... So it becomes a moot point, unless he wants to wait a while...

928fan4life

So will a stage 1 get me to 320rwhp? or do I have to goto a stage 2 for that?

Carl Fausett

On your 1980 AT, our Stage 1 will deliver about 304 HP from 6 psi of boost on a healthy engine, and stage 2 (intercooled) will deliver about 330 HP from 9 psi of boost.

In Stage 1, we get an increase of about 80 HP from 6 psi of boost, or a ratio of 13.3 HP per PSI of boost. In stage 2, although the gain is over 100 HP, the ratio is only 12.2 HP per pound of boost because we hit the max capacity of the early 928 fuel system to provide fuel.

All numbers I have been using in this thread are crank HP numbers, as I have been quoting Porsche published HP numbers, which are also all crank.

For RWHP, subtract 15% for manual trans cars and 18% for AT cars. Most Mustang owners use 20% as the loss factor thru their automatic trans, but I have found the Porsche 928 automatic to be more efficient than the Fords, and 18% seems to be a better number.

tammons

I have run 2 turbo cars with no major problems, both driven very hard and on several trips. The first one about 25k my current car about 55k + both on early not rebuilt engines at around 8-12 psi. Expect to pick up about 120 hp ++ and a ton of torque at 8psi and at 12 psi hang on. Its a wicked ride. Actually I am contemplating selling my setup, if i part my car. As far as temperatures, super chargers blow hot air too. The big difference IMO is a turbo has constant exhaust back pressure and a super charger is tugging on the crank all the time.

Supercharger is easier to install. Turbo is tough to build. With a turbo you will have more underhood heat. I have built 3 different types of setups for the 928, the last the simplest.

The only thing that is going to melt pistons and burn valves is letting the mixture burn temperature get too hot which will lead to detonation. I got some early advice from a turbo builder to set my car up at 1300-1350 degrees with an exhaust temp probe. At highway speed, no boost, I had it set up at 1450 or lean and got good gas mileage, but under boost I tried to keep it at 1300. 1650 F is melt down. The center of a detonation charge is around 6000 degrees, so it does not take much of that to melt pistons or collapse ring lands. The other problem would be say running race gas and 20 psi on a stock engine. You would probably create too much cylender pressure and probably blow a head gasket or collapse a piston. Also if you turn it up an efficient intercooler is manditory.

There were some guys down here that built a twin T4 Turbo S4 that was making 950 hp on race gas. First they collapsed the pistons, bent the rods, They then sleeved the block, new forged rods and forged pistons then started blowing clutches, finally got a clutch that would work, then started snapping drive shafts, got a custom one made then started blowing trannies and finally gave up.

The 928 drive train can handle around 500-600 hp more or less. Really I think 450-500 is probably the safe limit. I have heard of guys breaking the intermediate plate in high horsepower cars too. I think the early auto trannys can handle more, but I am not positive about that.

Carl Fausett

I agree.

Tammons is correct again here, Tim Murphy and Todd have shown that the 928 manual drivetrain can handle 500 HP - and more - for an extended period of time without damage. Both have been above 500 HP for at least a year.

The automatics in the 928 are actually spec'd to handle higher torque values than the manual, it is quite a tough automatic. CW says that the AT in the 928 can handle up to 650 HP and 700 Ft lbs of torque... although to my knowledge, knowbody has been there yet to tell us!

The "Supercharger vs Turbocharger" conversation is a bar stool arguement that has no end. It belongs on the list of other bar stool arguements that have neither answer nor end like: "air-to-air intercooler vs air-to-water" and "Positive-discplacement vs Centrifugal"

There is not doubt that, when properly engineered, they both work.

When it comes to aftermarket applications, centrifugal superchargers have several advantages (as compared to PD blowers and Turbos): easiest installation, ability to retain most if not all OEM anti-polution stuff for EPA recertification, and coolest charged air before an intercooler.

928fan4life

what would I need to do to get over the 300 rwhp if the stage 2 kits only get me to the 330 crank hp?

Rob Roy

Carl,

You talked earlier about the early 928 fuel system being a limiting factor. Is this the same issue for both the K-Jet as well as the L-Jet? If so, what is required to overcome it?

Thanks

Carl Fausett

928fan4life - I'm sorry, buyt you are driving a 220 HP motor right now, why don't you go to 320HP and stop and be happy? If more than 320HP was possible with the fueling system you have on that 1980, I'd have it.

How do you get above 320HP on an early L-Jet or K-Jet?
Our supercharger kit can provide more air, but the 928 is maxed out on fuel delivery at that point.

If your willing to run tandem fuel lines from the tank to the front, twin fuel pump syustems in parallel, and to re-program the L-jet or add an aftermarket
FMS (Fuel management System), change your injectors, etc, etc - all things are possible. These things are just not reasonable solutions for most of our customers who are kit buyers - they want a one-day, bolt -on, you-have-tested-this-already-and-it-works-soultion.

You can take ourt kit and keep building up from there if you like. The sky is the limit.

mspiegle

320rwhp+ in a car like that will be pretty fast... faster than my car was. I know that my car with 345rwhp (it was an 86.5) ran DEAD EVEN with a slightly modded '01 Z28. Go take a ride in one of those and see if you like it.

928fan4life

I would be more than happy if it wa 320 rwhp but as Carl said earlier it is 320 crank HP so that would make it around 275 rwhp

Carl Fausett

its the same thing.....
CHP before and after or RWHP before and after - ITS THE SAME THING.

let me convert it for you.

on a 1980 Automatic... you are driving around 180 RWHP now and the Stage kit will take you to 263 RWHP. Its still a whopin' improvement.

mspiegle

320chp is still going to be plenty of power in that chassis. What's the fastest car you've driven?

Carl Fausett

To put it another way...

The purpose of our kit - as the 16v Euros are so rare at 310 HP (at the crank, remember, about 264 at RW) is to take all of us guys driving around our 220HP 928's and wishing we had the 310HP euro - and give us performance above a Euro in one weekend.

THAT is what our kit is for. One weekends effort on an old 928 and viola! - you have a euro or a S4 under the hood! Our kit out-peforms both the 16v Eoro and the stock 32v S4.

Question: if you could trade your 220 HP early 928 in for a 1991 S4 - but keep your payments the same.... would you? Now you can.