Eric_Oz_S2

Pauly,

The cooler is the Rotrex supercharger oil cooler. The supercharger has a kind of in built oil pump that pumps through the cooler. I still have the stock S2 engine oil cooler (On the other side) that seems to work well on the track - never had an overheating problem.

mikey_audiogeek

Bigger crank pulley might kill two birds with one stone. 928motorsport make one.

Cheers,
Mike

Paulyy

the oil must get pretty hot then, I've got a SC14 (Roots-Type) supercharger, off a toyota 2.0L, and as far as i know the oil just sits in there.

Eric_Oz_S2

Yes - it is designed to spin at up to 100,000rpm. So a little like a turbo that is fed off the engine oil system.

Eric_Oz_S2

I decided to go for an 85mm pulley. Have installed just need to get new belt and then go through the whole tuning thing again. Should get about 5-6 psi. Decided to keep it safe at the moment for reliability. Timing will need to be reduced further as with very limited retard I was getting some knock counts around 5000 rpm near the torque peak. Plan is to use 0.75 degrees retard per 1 psi boost as a start point.

I ran the 100mm pulley setup on the track and there was a noticeable improvement - like 1+ second less accelerating from 140-180 km/h. Couldn't get a lap time reduction as it was pissing down rain.

Eric_Oz_S2

Dyno plots from today - peak is 180 kw at the wheels (242 hp). For our club rules (1.2x to get engine kw), this equates to 216kw and 290hp. So it is actually very close to my target of 225kw at engine (max for class).

Dyno
Note the dyno calibration seemed to be out by about 5%. Multiply the RPM on the dyno plot x 0.95 to get actual RPM that corresponds to the log data.

We tried advancing ignition further, but there was not much to be gained and knock counts doubled. With current maps there is only about 7 knock counts (all around 3000-4000 rpm), but on the road I get nil. Intake temps peaked at about 50 degrees C. The intercooler is obviously doing its job (it is better on the track as the airflow at the dyno room isn't that great). There is a dip in torque at around 4000rpm - not sure if this is due to knock retard?



Boost Log - about 7 psi peak


AFR log (from logger)
AFRs in low 11s. There is more to be gained by going to 12, but tuner thought this was not a good idea.

Dubai944

Nice result close to what you wanted, congratulations.

What was your opinion of GT Auto? Who is the tuner?

Eric_Oz_S2

They were pretty good. I controlled the programming, so it probably made it a little hard for them as they normally tune aftermarked ECUs (of course). I'll go back once I have made some further changes (MAF, etc). Next time I'll look at the timing map in more detail and try different maps.

blown 944

Congrats.

On your dyno it looks like you may be either pulling too much timing in the upper rpms or possibly that is where it gets rich. I would expect the torque to stay pretty flat. It almost looks like the compressor is not keeping up.

blown 944

Looking closer, your torque drop offs directly coincide with your afrs. I think it needs to be leaned out in those areas sliggtly

Eric_Oz_S2

For interest sake, I compared to the SFR dyno on their web page:



The torque is a little higher with mine, but the SFR peak power seems slightly higher but only at the top end. I suspect this is more a result of the dyno runs stopping a little too low. Of course different dynos = different results! I think the Rotrex ramps up a little steeper than the Procharger as well.

That dip up the top could be associated with terminating the run a little early.

The SFR kit has no timing adjustment (only an APEXI NEO-FC Fuel controller) and it will have more advance over 4000 RPM where mine has been pulled. The SFR does use a MAF however. I can only assume the SFR kit is pulling timing using adaptive knock control as I am retarding timing by 5 degrees at the top end (basically using 0.75 degrees retard per 1 psi boost). As the DME is already reading maximum voltage above 5000 rpm on the AFM, then using an interceptor to replicate the MAF signal will not work predictably above this limit. Without changing the maps the scaling will affect PT maps. Software changes in the DME is the only correct way to adopt a MAF.

In summary - the results are about what you would expect for an S2.

Now - how do I make it better?? RS Barn Headers, Hi-flow Cat or cat delete??

Eric_Oz_S2

Sid - AFRs are set conservatively to enhance engine durability. There would be some power to be gained by raising AFRs, but in my opinion the gains probably aren't worth the risk.

Yeah - I need to investigate timing further at the next dyno run. Probably should have retarded further as a comparison. I have to say I had the AFRs set leaner on a trial run and it did feel quicker - but got lots of detonation as well - so no good.

Eric_Oz_S2

Here is a comparison of the now supercharged S2 vs the data provided by Porsche for the 987S (Cayman S) (Porsche data is the faded graph with green line, the multi-coloured lines over the top are from my data logger). Note the acceleration is almost identical. I thought this was interesting to show how the performance has increased. In reality it is also lineball with the Cayman S - on the track the acceleration on long straights is almost exactly the same.

Paulyy

that's real good for a car that just dynoed ~245 rwhp

victor25

Eric, I just purchased an s2 and plan to supercharge it. As you can see from my avatar I already have experience with rotrex superchargers. Actually I sell a 928 s4 rotrex kit. Anyway, I may want to pick your brain a time or two, this is if you do not mind.
Actually would you be interested in selling me a mounting brackets, if you have any extras that is? What size charger are you using? I am planning a simple build with 6lbs.