gamman

Is there a correction factor, or to what sae number is being used?

Carl Fausett

It is set to the SAE correction factor only, which is 1.001 for the Mustang MD500 dyno. Results on an inertial drum dyno (like a DynoJet) are often higher.

Crazy Canuck

Hey Carl,

Call my friend (Canadian) back. He was one of the first to buy the SC kit, bought the Stage II pulley and the car hasn't idled properly. He talked to you about the upgraded engine management kit and has left 2 messages.

Call him back, take his money, sell him the parts he needs to have a running car and ship him the parts. His car hasn't run properly in 2 years.

Jfrahm

Mine never idled until I moved the MAF down to just after the filter. There is too much backwash where the MAF is located on the stock kit. The issues of random CELs (related to the MAF) and the engine dying when divebombing the throttle go away also. I had a chunk of J tube laying around and put it in place of the MAF, and moved the MAF down under the front header panel.

Someone else sorted this problem with a bypassing recirculation valve that dumps some % of the bypass air also, if you prefer that solution.

Carl Fausett

Chris,

Of course I'd be happy to call him. Who is it? Send me a PM if you want. I will check my voicemail again, but I have found nothing yet.

Carl Fausett

NOTE: I do not disagree with Joel's comments above, just want to point out that they are comments about the Stage I kit. This thread is about the new Stage II kit, and not applicable.

The Stage II kit, when installed as recommended, has no MAF in it, hence no idle issue with back-wash from the MAF.

Carl Fausett

I was putting this together for a customer, and thought you might all want to know this.

If you have our earlier Stage II kit with the single-sided belt, you can easilly upgrade to the current Stage II setup with the double-sided belt.

You should have the upgraded (larger) crankshaft pulley, and larger injectors already.

If so, you will only need:

1) the new Stage II supercharger mounting bracket $ 136.00
2) the new Stage II double-sided belt $52.00
3) the new Stage II supercharger pulley $67

Total: $255.00

That will give you all the mechanicals for the new Stage II kit.

Then you will still need to come up with more fuel, control the injector events, and retard the timing under boost as needed. And the best solution I have found for this is the Electromotive kit for the 968 at $ 3120. Then you have complete tuning flexibility in the future and no idle issues.

pudjnr69

Carl,

As per Eric's post, a lot of us who bought the earlier kits have done most of these mod's ourselves. What did you do to get a 1710mm long belt to fit. I tried it on the original set-up and it was about 100mm too long (with the larger crank pulley, alternator pulley, etc).

I am still getting belt slip when running the smaller SC drive pulley - but the rebuilt SC has to be run-in and then I might be able to go back to a smaller pulley.

For intercooling - water to air would be best, but we could not find anywhere to put the radiator, hence the air-to-air one in the engine bay. We still need to do some bonnet/hood modifications to get the kit to breathe better.

De-compressing the engine to 10:1 lets it rev harder at high rpm.

Carl Fausett

Remember, every time you go to s smaller pulley, you loose tractive force and increase the load - the two forces are working in opposition. Each time the pulley gets smaller, the contact patch between the pulley and the belt gets smaller. And a smaller pulley also makes the impeller turn faster creating the need for even more traction.

This is why I developed the larger crankshaft pulley. The larger diameter crank pulley allows us to use a larger supercharger pulley and we gain tractive force on both ends.

Make sure you have our crank pulley, and then you can stop your belt slip without having to tension the belt like a piano string (which also shortens the bearing life).

The complete Stage 1 to Stage 2 upgrade includes the larger crank pulley, larger supercharger pulley, the double-sided belt, AND THE NEW SUPERCHARGER MOUNTING BRACKET that spaces the idler pulley out to match the new, longer, double-sided belt.

pudjnr69

Carl - I have the larger crank pulley installed, plus a larger than stage 2 supercharger pulley as the standard stage II supercharger pulley slips with a 6-rib belt. According to Tim at Raptor - with the standard Stage II pulley I should have been making around 10psi - but we cannot get over around 6psi without belt slip. We looked at trying to get more belt wrap on the SC pulley - but this is not possible.

As per the previous posts - I am running the VW 7-rib belt cut donw to 6-rib with a smaller top idler pulley.

If you want boost - you have to run the SC unit close to max rpm - or you just don't get max airflow. We were chasing max airflow and boost - hence why the engine was decompressed to 10:1, as at standard compression we had to wind a huge amount of advance out of the engine (Australian fuel is not as good as US fuel). By decompressing the engine, we could wind advance back in.

pudjnr69

Carl - what is the difference in the SC mounting bracket? I have two 1710mm 6-rib belts. Does it give you enough room to possibly run a second idler pulley to get more belt wrap on the SC (even a small deflection idler)

Carl Fausett

I dont think you will ever see 10 psi of boost. I know you have done the math for impeller speed - and I stop the Raptor at 50,000 rpm. http://www.928motorsports.com/servic...eed_Calculator

I got about 8 psi that way on a race engine with headers. It will never see 10 unless you over-clock it.
Expect very short bearing life if you do that.

Our bracket holds the same reversing pulley as the Stage 1 kit, nice and large to help belt wrap on the supercharger. It sounds like you have installed a smaller reversing pulley and that lessens the belt wrap and also spins to fast - the bearings in the reversing pulley will have a shorter life.

I can sell you just the longer bracket if you like - just PM me or email me at carl@928motorsports.com

Super7

Hi Carl,
Thanks for getting me the new plug wire set and brake fluid so fast. (Please send me the bill so I can get you paid) The car ready for the track again. I have had time to go over the car carefully, everything looks great and I am really confident in your new stage 2 supercharger installation. I just need to get a track day scheduled. I am posting a picture of how I mounted the plug wire separator on the distributor blank cover (just with a longer screw). Please let me know if you have other ideas of how the plug wire routing should be done.
Carl, thanks again for all of your very capable help.
Scott

Eric_Oz_S2

There must be a lot of drag in the SC unit for the Raptor to get belt slip. With the Rotrex I get zero slip with an 85mm pulley and the SC head unit running at 100,000 rpm internal speed (9.5:1 step up). That's with getting 7+psi at the intake and around 150 degree belt wrap on the SC pulley. The Rotrex has an adiabatic efficiency of about 78% where I run it. There is also larger Rotrex unit again that flows 40% more that would give about 10psi. These have been run successfully on 944S2's with standard crank pulley and no slip.

So perhaps the Raptor takes a little more horsepower to run hence the belt slip?

Carl Fausett

Scott - those are fantastic photos. I like where you have tied your ignition wires down to - that should work well.

Eric - we have seen the Rotrex and we know that the Raptor has higher adiabatic efficiency (85%) and higher pressure outputs. Its a nice supercharger, don't get me wrong, but head-to-head it will not compete with a Raptor.

The CFM output of the unit and the pressure it is able to build in the manifold is directly related to how much load you will have on the input drive belt. The higher the discharge output in CFM and pressure, the greater the load on the drive belt will be.