quote:Originally posted by jeffw
A good day today at Debden although with mixed weather.
I ended up 2nd in class with a 67.x sec run, 7th overall and was beaten by Paul Bowden (by 1 sec) and some single seaters. First real competitive
run for the Supercharged Phoenix, 2nd run I was running out of fuel on the last few corners and the third run I outbraked myself into the roundabout
(always a sign you haven't done your best time when you have to select reverse during a run !).
It does go well....100mph in 3rd ! Still on low boost mode so once the extra 50-60BHP appear we should be a little further on. Looking back at my
previous Debden data the car is 15mph faster at peak speed to my 210BHP NA engine.
The tyre size on the rear is 215/55 13" Avon ZZRs.
Yes indeed. Omex have been doing a lot of work on the Raw car recently (Engine dyno, different heads/cams/intercoolers etc) and have settled on an
engine specification which best supports the Rotrex kit.
I need to change my intercooler, which is very inefficient, for either a better intercooler or a charge cooler. This will gain back something of the
6psi loss currently through the intercooler and then we can reduce the supercharger pulley size so that we hit max supercharge rpm at max engine rpm.
This will give us another 2-3psi. With these two modifications alone it should go from 9psi at max rpm (250HP at the wheels) to 14-15 psi at the
plenum which should see the engine up towards the 300HP at the wheels. If we then skim the head to give 11:1 compression ration and the new, bespoke,
cams that Omex have developed it will be well into the 300s at the wheels. Maybe even 350-370 at the crank.
Just dropped the pulley by 10mm and it now runs 310BHP & 240 ft lb. Still have a lot of losses on the intercooler which will be the next thing to
resolve...
What maximum RPM are you running ? I beleive the Rotrex supercharger is designed to run at a maximum 100,000 RPM and with the engine running at 7500
rpm with the pulley diameter at 95mm (which is what it has been designed to run at) it is just over the limit at 104,000 RPM. If you are dropping the
pulley diameter to 85mm, the supercharger will be heavily overspun at an engine speed of 7500 RPM (I think it works out at about 140,000 RPM) and I
have been told the supercharger will not last very long - I looked into doing this also but was advised not to. Have you done something different to
support this or running lower maximum engine RPM ?
Rev limit is down to 7100 which works out to be 101K on the supercharger. My cams are done and dusted at 7100-7200 so not an issue although as you
can see from the spreadsheet 90mm maybe the way to go.
After the idler and tensioner failure and the 3rd gear being stripped (box has been rebuilt as a BGH E8 now) the car is running. When the head was
off to replaced the bent valves they discovered the clearances where set at 2 thou and not 10 thou. All these where reset and the engine now revs
much faster (!) and makes 300BHP at the wheels....which is why 3rd gear stripped.
A very wet Abbeville last weekend. Car was wheelspinning in any gear with more than 1/2 throttle. Does show how easy it is to drive on part throttle
though. Make sure you switch to 1080p...watch me almost put it in the gravel on hte first lap and all the MX-5s drifting.
