Supercharger project

[944 man]

I'll look forward to it; but I'll wait until its settled down.

Is the supercharger drive belt as close to that water hose as it appears to be?

 

[Peter Empson]

I had to shorten it quite a bit, but that picture is misleading, there's a fair bit of clearance now.

 

[Diver944]

Looks much better than the pictures at the beginning of the week []

Is the foil wrapped pipe on the left the output from the supercharger and the blue one on the right goes into the throttle body, and where on earth is the air filter?

 

[Peter Empson]

ORIGINAL: Diver944
Is the foil wrapped pipe on the left the output from the supercharger and the blue one on the right goes into the throttle body, and where on earth is the air filter?

From the front of the car, the right hand pipe goes from the SC into the intercooler and the left hand one goes from the intercooler to the throttle body. The supercharger inlet pipe (that I had all the problems with) is effectively a 'C' shape, which loops the intake pipe back under the supercharger so the air filter ends up just in front of the offside wheel pointing pretty much straight ahead.

 

[Gary C]

The compressor looks like a centrifugal unit ie just like a turbo's compressor ?

Never seen a supercharger like this, only screw or lobe units, or is it one of those G-wave units like VW used ?

 

[PSH]

Nice project Pete... I'm impressed.....[8D]

Pete

 

[Peter Empson]

ORIGINAL: Gary C

The compressor looks like a centrifugal unit ie just like a turbo's compressor ?

You're spot on Gary, that's exactly what it is. They're the most efficient supercharger, are compartively easy to fit and should still give reasonable fuel economy around town. The downside is it doesn't make much boost at low rpm's but I think that suits me, as there's no massive torque at get away to cause the transmission problems.

 

[sawood12]

Pete,

Does it have a variable gear or a fixed gear, i.e. at low engine revs does it have a higher gear than at higher revs?

 

[Peter Empson]

Hi Scott, it has a fixed ratio. The specs are quite interesting to read, its max internal rpm is 80,000 for example, and in the right application it will produce up to 24 psi []

 

[edh]

ORIGINAL: Peter Empson

Hi Scott, it has a fixed ratio. The specs are quite interesting to read, its max internal rpm is 80,000 for example, and in the right application it will produce up to 24 psi []

you mean in a 3.2 low compression build? [] - you'd have to flow some air to make 24psi! - presumably there's a CFM limitation on the blower that would kick in first? (not that I know much about superchargers..)

 

[944Turbo]

Excellent glad you got it running and initial outlook is good. Cant wait to see it.

I will be hoping to fit my innovate Sunday and do some mapping before Monday afternoon - I was supposed to have this week off to get some work done on the car but ended up working instead.

Good luck,

Tony

 

[Peter Empson]

ORIGINAL: edh
you mean in a 3.2 low compression build? [] 

Don't tempt me...
I may have some evil plans for the spare block, but I've just not worked out quite what they might be yet [8|]

ORIGINAL: edh
- you'd have to flow some air to make 24psi!  - presumably there's a CFM limitation on the blower that would kick in first?  (not that I know much about superchargers..)

Max flow is listed as 1100 cfm (not that I know much about boost).

 

[Gary C]

Interesting, the efficiency of a turbo without the inertial lag.

Does it need a bypass to prevent compressor surge ?

 

[Peter Empson]

Hi Gary, my setup uses at a BoV, although I read somewhere that this isn't a necessity with my SC.

I've had a fun day, the morning was spent sorting out wiring and gauges and the afternoon driving the thing []

Most of the A/F tuning is now done, there are some areas that need more work (especially when coming off the throttle at high rpm's), but I'm pleased so far. I've stayed slightly on the rich side in many places as a safety measure, with WOT in the 12-12.5 region.

Only issues are the idle still isn't great (I decided simply raising the speed was a cop out) and its stalled on me a couple of times when dipping the clutch after a high rpm run (almost certainly related).

I'm getting a max of 0.4 bar (almost 6 psi) which is very close to target, and somewhere in the region of 0.2 bar at 3k rpm, which very quickly increases to 0.4. I have a feeling there's a little belt slip at higher rpm's as the boost curve appears to flatten off at 0.4 rather than continuing to rise to a peak as anticipated, but I'm not complaining. I don't want to tighten the belt until I'm sure that is the case as I've heard the standard altenator bearings don't like increased loads placed on them.

The noise is quite fantastic, very similar to the jet like noise of some of the Turbo's like Paul's, but not as high pitched, and it sounds right, mingling nicely with the exhaust note. I'm even getting used to the slightly demented whistle at idle. I'll try to get a video done (there should be one tomorrow anyway)

It definately pulls a fair bit harder than before, I've spent too much time today with one eye on the gauges to really enjoy the extra grunt, but considering I believe the timing to be very conservative it's working rather well. I'm sure when I get a pro to fine tune it on a dyno then there will be even more to come.

Some I'm now hot, exhausted, deafened (even with ear protection on most of the time) but happy []

 

[Diver944]

Can't wait to see this in action tomorrow [8D] Well done Peter

When I setup my Turbo with the piggyback I was advised by Vitesse John to aim for an AFR of 11.8:1 or slightly richer to 11.5:1

Is it slightly different for a supercharger so you can go a bit leaner at 12.5:1? If it is I suppose it's because there is less heat being output as the exhaust gases are not involved?

 

[Peter Empson]

I was under the impression that the SC wouldn't need to be as rich as a Turbo, the reading up I did suggested a min of 12.5 was a good target, but I'm very new to this boost stuff, so perhaps a bit more fuel wouldn't go amiss just to be on the safe side. I'll have another play tomorrow [].

 

[Diver944]

No, don't adjust anything on my say so - I know nothing at all about fuelling for superchargers.

May be worth a quick email to John at Vitesse, he'll know and was always superbly quick with support when I was tuning mine.

 

[Peter Empson]

Yes John has been fantastic, it seems his base map was pretty close considering everything. When I was running AFR's in the mid 11's I could see some blue/black smoke, which suggested to me it was richer than it wanted to be, this disappeared when I got it into the 12's. I've just been rereading a thread about a 968 owner with the same kit and he's doing the same, which seems promising (and he has more boost than I do).

 

[Peter Empson]

I've just heard back from another owner and he confirms I probably have some belt slip, he's getting 0.55 to 0.6 bar on his setup with the same pulley, he uses some anti-slip belt spray and has increased the tension which seems to have done the trick.

I'll get tonight out of the way and then have a play []

 

[Copperman05]

Interesting thread Peter, thanks for sharing. Look forward to seeing and hearing it sometime in the future.

Edd