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Driving a XKR without the supercharger - how much power?
Well my supercharger started to make a lot of noises, and needs a rebuild. After the struggle of getting the supercharger out of the car I was curios if I could drive it without.
Made blinding plates for the elbow outlet (where it connects to the backside of the supercharger and for both intercooler inlets.
Disconnected the bypass valve and set the butterfly valve stuck open.
Result? Car starts and drives "without issues" and no warning lights or fault codes.
BUT. The engine now has to breath all its air through the tiny bypass valve.
My car scanner app can calculate theoretical horsepower from MAF - with supercharger 390 hp, with supercharger and bigger lower pulley (+18%) 430 hp and now without supercharger? 102 HP! This is at 3800 rpm, I did not bother try higher rpm, it is just SO slow to pick up speed :-)
and now without supercharger? 102 HP! This is at 3800 rpm, I did not bother try higher rpm, it is just SO slow to pick up speed :-)
An interesting experiment that reminds me of the switchable Supercharger on the Mad Max V8 Interceptor !
The low performance is due to the relatively low Compression Ratio of 9:1 in the 4.0 XKR. The engine is designed to expect a minimum quantity of air volume from the Supercharger and this minimum requirement is simply above that achieved with normal aspiration.
Roughly plotting your measurement (Blue line) on my own power chart (standard 4,2 XKR) it appears peak power without Supercharger is about 125 HP !
An interesting experiment that reminds me of the switchable Supercharger on the Mad Max V8 Interceptor !
The low performance is due to the relatively low Compression Ratio of 9:1 in the 4.0 XKR. The engine is designed to expect a minimum quantity of air volume from the Supercharger and this minimum requirement is simply above that achieved with normal aspiration.
Roughly plotting your measurement (Blue line) on my own power chart (standard 4,2 XKR) it appears peak power without Supercharger is about 125 HP !
Interesting. BUT the low power is mostly because it now breaths through the bypass valve and are choked from air. I did not measure how big that butterfly valve is, but about 25 mm (1 inch) maybe?
Interesting. BUT the low power is mostly because it now breaths through the bypass valve and are choked from air. I did not measure how big that butterfly valve is, but about 25 mm (1 inch) maybe?
Read again! The supercharger are removed from the car, not just the drive belt. That is why I had to blank it.
you are very adventurous,
I’m not understanding how running the engine thru the bypass valve is a learning experience. Probably some aspect of it that is beyond my understanding ( that’s a low bar ).
I’m not understanding how running the engine thru the bypass valve is a learning experience. Probably some aspect of it that is beyond my understanding ( that’s a low bar ).
Well I learned that it was a stupid idea and waste of time
I also learned that it was not a total waste of time, because the car now starts and runs (ish), so it is possible to move it around while I am waiting for the new supercharger.
Driving a XKR without the supercharger - how much power?
