Eric_Oz_S2

Carl, I suppose unless you measure the 2 setups on the same engine with the same power output you will never know the true adiabatic efficiency of these. Rotrex also makes claims of "upto 98% efficiency" - that of course depends on size selected and what point on the map it is run. As Raptor aren't particularly forthcoming with technical information and the Raptor has no separate oil cooling system, let's just say I don't disagree with the claim but I'm a little sceptical. Perhaps teh 85% efficiency is an optimum value, but not necessarily the case if it run flatout?

It sounds like you have real world experience - can you elaborate on how you have compared the 2 head units? I also wonder when subject to heat soak in a racing environment whether the true efficiency still holds (given the Raptor has no way of cooling itself).

Carl Fausett

Correction: the Raptor is air-cooled. It comes with a remote cooling fan unit that blows cool air thought the case and out the other side. It is very effective at cooling the bearings and the case.

The manufacturer has recently upgrade the remote cooling unit to one that is smaller in size, but produces more CFM. The coolers are small, lightweight, and draw very few amps.

Eric_Oz_S2

How do you get cool air to it? It's not in a particularly cool part of the engine bay.

Carl Fausett

I agree. Anything behind the radiator is hot. So the remote air cooler for the supercharger is mounted in front of the radiator iin clean, cool air, and the air hose is run from it to the Raptor. There are two barbed hose bibs on the Raptor, one for cooling-air-in and one for air out. All these bits are included with the Raptor.

Here is a picture where you can easily see both of the cool air bibs on the head unit.

Cooling the bearings and the case with cold air from a remote location (in front of the radiator, not in the engine bay) is simple and uncomplicated, lightweight, and works well.

Super7

More 968 stage 2 track time:
I just got the car back on the track for the second time for another test and tune. Another great day! I have an AIM data acquisition system so I can post some real results. First of all I am really out of practice with having only driven on the track a few hours total in the last few years. I have also made a lot of set up changes to the car some there is a need for some real experimentation and relearning too. I took the data from my best 968 Mid-Ohio run ever (back in 2006) and compared it with this stage 2 test and tune day.
End of Front Straight speed: 98.6mph to 107.2mph (8.6 mph improvement)
Between turn one and two: 102.2 to 110 (7.8 mph improvement)
End of Back Straight: 127.5 to 138.7 (11.2 mph improvement)
Between 10 and 11 95.2 to 103.5 (8.3mph improvement)
Lap times:
With all of the unfamiliar changes to the car I was just hoping to not be a lot slower. I was looking for 1:45. I really never got completely in the grove before the brake fluid boiled. I think there are still a two to three seconds to be found.
Lap 1: 146.746
Lap 2: 145.262
Lap 3: 145.202
Lap 4: 148.016 traffic
Lap 5: 148.225 traffic
Lap 6: 144.202
Lap 7: 144.349
Lap 8: 141.659
Lap 9: 140.968 (It was really hard to get last three digits to be "968")
...Boiled brake fluid. (I am having my brake cooling ducts relocated and enlarged)
My best lap in this car at Mid-Ohio, at the top of my game, was a 143.069. It don't think getting into the 1:38s with the stage 2 supercharger will be a problem. I will post another update next season.

mikey_audiogeek

Great work!

Cheers,
Mike

Damian in NJ

Beautiful!

Carl Fausett

Thumbs up! Well done!

333pg333

Have you got any in-car video Scott?

Super7

Another 3 days of 968 stage 2 track time:
I just got back from Mid-Ohio. It was mostly wet and cold (April at Mid-Ohio) but still was able to run the engine hard three days in a row. Flawless performance with the stage 2 kit. It don't have any concerns with reliability. I just check the temp sticker and belt after each run and everything was always is normal. I haven't taken any videos yet but will do so. It really runs with an entirely different group of cars now. The GT3 cup cars and the GT3RS 4.0s still get by me but they don't pull away very fast anymore. I will post another report next time.

RajDatta

Nice!! Thanks for sharing.

Carl Fausett

I really hope this gets read by those who still fear that our kit has belt slip problems.

The first models did when they were raced, they were re-designed, and now they don't have belt slip issues at all - even when raced.

Thanks for the feedback, Super7!

mtnspeed

A little additional work first, but would like to keep up with my buddies M3's at the track.

Jfrahm

I for one was never able to cure belt slip on the street with the single sided belt and SC driven on the belt back (currently stage 1.) This was either with the early stage 2 or stage 1 pulleys. I could get it to not slip and drop boost for short periods of time with the belt very tight, but I got belt dust and a belt smell all the time and soon I would see the boost fall off at higher RPM.

The Phaeton V6 double sided belt seems to have sorted it, as did the double sided Corvette or Volvo belt with an additional idler. Before I got the Phaeton belt from the UK I planned to put an eccentric at the reversing idler for easy belt adjustment and use my extra idler setup, which mounted an idler between the AC and crank, to allow a longer double sided belt available locally to be fitted. I like this solution because you get more crank wrap and you can then adjust the belt tension from above and not get dirty. If I ground some flats on the eccentric the belt tension could also be set with a torque wrench and crow's foot.

My extra idler down there killed about half of the belt adjustment range and made getting the belt on and adjusted a chore. I could have moved the idler to the span between the alternator and the AC but then you do not get more crank wrap and having some belt adjustment up top is desirable and no great engineering feat.

-Joel.

Carl Fausett

Thanks for working through it, Joel. Yours was install #1.

They've gotten quite a bit better since then!