questions about fitting a centrifugal supercharger

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Mat Grant

southern UK
Hi all,

I am looking to supercharge a 1UZFE, my 1UZ is swapped into a Lotus with a very low bonnet line. So Rootes/twin screw type blowers that sit on top of the engine are out, so has to be a centrifugal - I am looking at fitting a Rotrex C38. I have made a plywood mockup of the bracket (which I have named the “Squid bracket”) to mount the C38 at the front of the engine and have a dummy head unit which allowed me to trial fit the belt fitting etc.

I am looking for quite low boost 6/7 PSI, as I am told this will work with stock ECU and injectors. I have picked up a set of 8 “pale green” injectors in case they are needed – can’t remember the engine they are from, but it is the sort that bolt straight in – same impedance as stock 1UA ones. The car has the Toyota W58 gearbox, ally sandwich plate version, and changing gearbox (eg R154) is going to be too much work / hard to fit in chassis so don’t want to do it. So I’m looking to keep the torque down to where the W58 won’t break.

But I have not put a supercharger on an engine before, so have a few questions, if anyone can answer them from experience or knowledge I’d really appreciate it.

  1. Is it good to go for 7PSI on the stock ECU and injectors? If I change only the injectors for the higher flow ones, will that allow the ECU to fuel the engine correctly? My (very basic) understanding is that the engine adjust injector opening via feedback from O2 sensors etc to deliver the correct fuelling)

  1. Should I fit an intercooler for 7PSI – space / air hose routing will be a bit of an issue, From the reading I’ve done I get the impression that at that level of boost it won’t be necessary, but am I good to run without one? Or is it needed?

  1. I’ve read about the PCV hoses, where the throttle body one needs the PCV valve added to prevent the boost pressurising the crankcase, but is anything else required in this area?

  1. Will the brake servo be getting enough vacuum to work properly? Logic tells me as there are so many boosted engines out there it’s either not a problem or there must be a way to ensure vacuum at the servo(?) But is anything specific required? There will be a blow off valve fitted.

  1. Do I need an oil cooler? The water radiator is a custom built 3 core ally one as large as will fit in the space, so there’s not a lot more I can do there, but have space for an oil cooler.

  1. Anything else I’ve not thought of that I should consider before committing to going down this route?

I’ve done some searches of the forums but couldn’t find definitive answers, so if anyone has answers to any of the above or recommendations I’d appreciate it.

Thanks, Mat.

PS - mods sorry if this is in the wrong section of the forum