Supercharging?

[Eric_Oz_S2]

Resurrecting an old thread, but I thought I'd chime in. I'm currently developing my own S2 supercharger install using a Rotrex SC and keeping the AFM. Also using the 951 intercooler and turbo injectors (as per Peter's).

Tuning will be done using the Ostrich 2.0 emulator and tunerpro. This way I can adjust the timing and fuel to suit and potentially also run dual maps (using the coding plug). As boost is progressive with RPM, I can adjust timing purely by rpm as the two are always related (unlike a turbo that uses a wastegate). Boost will be somewhere around 5-7 psi - the actual value to be determined through trial of various pulley size and dyno results (need to keep rwhp to 246 to keep in planned class for next year).

The install is still underway, but here are a couple of progress pics.

Oil cooler has been installed in the left hand side using the existing support that mirrors the support for the engine cooler on the RHS. Simple brackets fabricated using 40x3mm galvanised steel flat bar and utilising the existing holes in the body. The cooler is a very tight fit but almost looks like it was made to go there. Cooling ducts in the front bumper cover line up nicely with the cooler. Some rubber grommets help isolate the cooler from vibration and give it some give between the radiator support frame and bracket. There is about 2mm clearance from the modified horn location to the cooler.

Also mocked up the basic hose system for the intake. It is amazing how much you can outlay on the various hoses, couplers and clamps. It would have been cheaper I think fabricating up most of this as hard lines, but at least this way I can easily adjust the setout. There are still a few pieces to install in this system.

The intake area is really tight. I am having to use a series of 45 degree bend and a 90 degree bend to get the pipework between the AFM and behind the front guard/fender. The cone filter will sit in the wheel well in front of the inner wheel liner and behind the front bumper cover. The hoses shown are not necessarily the right size, but show how it will fit together. I couldn't find anywhere to put the rotrex oil reservoir except in this busy little corner. It just squeezes in and is supported partly off the AFM. It may require a single hole drilled in the body for the lower bracket support.

 

[Bob]

Looks very tidy Eric, is this going in to a racing car or trackcar?

 

[George Elliott]

As Bob commented, nice setup.

I notice RUF use these Rotrex units for some conversions, and they are big/serious Turbo players.

The Rotrex unit seems almost like a Supercharger / turbo hybrid. Its a supercharger in that it is engine driven, but is turbo like
in that the "air pump" is an impeller with centrifugal housing, not positive displacement.

The traction drive is an unusual device. Can you achieve boost below 2000rpm??? Can you really spec the unit to deliver a constant boost as rpm increases without a waste gate to bleed excess air??

The 245rw figure is relatively low for the potential in your hardware, will that be the lo map, and perhaps 340rw be the hi map??

Many potential advantages over a turbo.

Only supercharged car I have experience of is a G60 Golf. Quick but thirsty, and I suspect the most fragile Golf I ever had.

Keep us up to speed
Happy New Year
George
944t

 

[Eric_Oz_S2]

ORIGINAL: Bob

Looks very tidy Eric, is this going in to a racing car or trackcar?

Thanks Bob.

It is a track car that gets some occasional road use (mainly driving to the track!)

ORIGINAL: George Elliott

As Bob commented, nice setup.

I notice RUF use these Rotrex units for some conversions, and they are big/serious Turbo players.

The Rotrex unit seems almost like a Supercharger / turbo hybrid. Its a supercharger in that it is engine driven, but is turbo like
in that the "air pump" is an impeller with centrifugal housing, not positive displacement.

The traction drive is an unusual device. Can you achieve boost below 2000rpm??? Can you really spec the unit to deliver a constant boost as rpm increases without a waste gate to bleed excess air??

The 245rw figure is relatively low for the potential in your hardware, will that be the lo map, and perhaps 340rw be the hi map??

Many potential advantages over a turbo.

Only supercharged car I have experience of is a G60 Golf. Quick but thirsty, and I suspect the most fragile Golf I ever had.

Keep us up to speed
Happy New Year
George
944t

Boost below 3000rpm is practically non existent with these units. On the track the car is always sitting above 4000rpm so it is not of too much concern. On the street you would probably notice the lack of torque increase down low.

245 rwhp is to achieve a power to weight of 5.72 kg/kw (class limits). Using class rules this works out to nominally 220 kw at the flywheel (rules state flywheel = wheel power x 1.2)

You can flatten the boost out using bleed valves, but you need to use a MAP sensor and standalone ECU for this to work. The best I can hope to achieve is to provide some inlet restriction to flatten out the boost curve - effectively increasing losses with higher RPM. For this reason I haven't been too hung up on reducing bends to the SC inlet (as there are about 7). It is a case of testing this and then (if necessary) dropping pulley sizes and adding an inlet restrictor plate.

The biggest advantage over a turbo is simplicity.

Possibly run a race map and road map. May also need to run the race map with O2 feedback disabled to add extra fuel for tip in conditions etc.

Cheers

Eric