Twincharging with Screw-Type SC instead of Roots

[jbond]

Twincharging an engine that features a screw-type supercharger (ie it already has internal compression) in my mind has the following advantages and disadvantages:

Disadvantages:
It would still feature parasitic loss when the supercharger is "bypassed" and the turbo is powering away at higher rpm

Advantage:
The efficiency being better than a roots blower, would mean lower temps and more power

Can one of the gurus post their thoughts? PatPrimmer and Warpspeed had a lot to say on previous TwinCharge topics.

In short: what is the suitability of screw-type SC for twincharging project?

PS: I really have the twincharge bug! help!

 

[patprimmer]

Crankcase oil has a much harder life than gearbox oil due to blow by of combustion products.

A blower gearbox may see some oil dilution from unburned fuel depending on where the fuel is added to the system. This applies to all oil types



Regards

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[j79guy]

The best oil is the oil you change. Regularily. I put a B&M minicharger on a small block Chevy, back in the mid 1980's, and about a year and a half later, the customer calls me up saying the blower tossed the drive belt and the unit is siezed. I ask "when did you change the oil last"? Bingo, he never did. Rebuild was thankfully light, and from then on every 5000km, the oil was replaced with regular 10-30 engine oil with good results. On my Thunderbird SC, I was using genuine Ford supercharger oil, when I discovered that Ford's supercharger oil seemed to be exactly the same as aircraft turbine engine oil, (Unscientific smell, and finger feel test.) and since then I've used Esso-2380 turbine engine aircraft oil in the supercharger gear sump, with excellent results. (The car now has 265,000km on the original engine.) A lot less expensive per litre too.

j79guy

 

[jbond]

Well, just a short update on this one today I bought an EJ255 which is the 2.5 litre turbo engine as used in the Subaru WRX 2006+ models

Have also decided that I won't do an engine transplant, but I'm going to design a car in Pro-E software and then build it

Also, I'm stoked at the price - I got it dirt cheap! $300AuD which is about $200 USD
how cheap is that! spun bearing or something, which doesn't matter cos I'd rip it open anyways~