Someones feeding you a bit of overly optimistic info there.

What they did was drop a smaller pulley onto the stepdown of the supercharger, but 60-80hp? Generally I think most street racers would be estatic to get another 20-25HP off a smaller pulley. (Smaller means it spins faster, thus provides more boost).

Considering anything over 9 PSI on a Supercharger with a stock engine requires a intercooler and aftercooler, I wonder if they bothered to install the proper cooling to the system to maintain lastability? Huge mistake unless proper precautions were made, and this is why stock SC's have governor limitations of 6-9PSI. Anything more and you need special cooling for just the SC.

I predict your Dyno will come in at around 50% of the additional HP they promised. They don't sound to savy on the performance side of street tuning wherever you are getting it done.

I am somewhat skeptical as well.  This is at the dealership.  Here's what they said:

The components add 53HP. That's what they're rated at. That part I buy.  On top of that, and this is the part that is interesting as it goes into the deep unknown (i.e. way out of my knowledge area) is that they did something with the Supercharger bypass to take it from 10PSI to 15PSI.

They said that Eaton rates it as safe up to 15PSI.  And hence the other 47 or so horse power comes from that.  I'm skeptical though about that and want to learn more about that.  Since it's all under warranty (this is the dealership doing this) I'm not too worried but still curious to learn more about this.

Heh, yes, it's under warranty now - will it stil be in a few years time, though? Perhaps they expect to pick up a bit of extra work later . . . you have to ask why they don't just do it as standard. Could be it would just use more fuel than normal in that configuration.

@ 15PSI on a super charger boost with normal compression (standard for a Jag of your type is approx 8.9 to 1) that's the equivalent of a 17 to 1 compression ratio) Thus the only way that the engine won't detune itself to prevent redetination is if you put race fuel in. If you put race fuel (112 octane or higher) you MIGHT get what they claim, although you'll be smoking hot without a full intercooler, one that is way higher rated than the one that comes in the car. Fortunately, the car will detune itself with the computer to prevent most of this, although if they have taken out all of the auto PSI sensors etc. you're going to cook your supercharger pretty quickly, and because it's direct drive unlike a turbo, you can really kill your engine in a hurry with this, even on belt drive. (causes backpressure at the wrong times and can break piston shafts etc.)

Since they would charge you ALOT of money to change the compression ratio (they have to take the entire top end of the engine off and basically double or triple up on the thickness of the head gasket) I doubt that they've done it the right way and you're going to have problems in the long run.

And keep in mind that this is a Ford engine you're talking about here. It's not like it's a Honda that will run on dirt for 5 years straight and still not need a tuneup. I'd go have the car checked by someone that knows their stuff on turbos and superchargers when they're done to see if the dealership fu*ked your car up or not. Likely they have. Even if the supercharger is rated at 15 psi and it has a strong enough cooling system for a supercharger to be spinning at close to 25,000 RPM to get 15 psi the engine itself isn't going to be happy. Best case scenario, it's just going to detune itself if the computer can compensate. Worst case you're going to blow up your engine. If you're lucky it will happen within warantee.

At the very least, make sure that you're running 93+ octane at all times, cause otherwise you're just going to use fuel like crazy and get nothing for it.

Just a couple things worth adding:

1) It's a leased car. So in 3 years, it's going back. And anything that goes wrong during that time is their problem. So they have no incentive to screw with it.

2) I will definitely keep people informed on the results. So far, I'm very pleased with it.

Brad,

Changing a supercharger pulley does add horsepower, but not that much. I changed mine out on my 911 and i gained around 27-30 hp when we when we put it on the dyno(the supercharger was being rebuilt at the time, so i'm sure it also factored into the gain in hp) Definately follow Galt's advice about taking it to a supercharging specialist if you suspect there's a problem. I have found that aftermarket supercharger mods can get a little wacky if everything is not set up correctly.


High octane is the way to go. I like to spike it with a little avgas once in a while to give my ride a little treat. She likes it!

If you put race fuel (112 octane or higher) you MIGHT get what they claim

Always be careful of racing fuel, though.  Most of it has lead in it, which is typically the stuff you'll find at pumps around here (usually you can only find turbo blue, which isn't blue, and it has lead in it).  The "good" stuff is typically only found at the track.

Other bits to note about fuel- if you buy fuel that is meant for off-road use (which most racing fuel is, and is off road diesel) it is colored red.  Why?  Because it's not taxed the same as on-road, and you get a hell of a fine if you have it in your car and they catch you on the street.

By the specs online, I'm sure you will be fine simply running premium in it.....plus, who cares?  It's a lease.  If it blows up, it's their problem.