An M45 is really quite big for a 1300cc. They are mostly on 1600cc or 1800cc cars. You can run the charger to 15,500 rpm so with an engine capable of 6,500 rpm and allowing for a loss here & there, the charger is 'theoretically' capable of giving a 1300cc engine 27 lb of boost! Now M45s don't like that much and a lot would leak back yadda yadda (don't go there) but it does show that it really is too mcuh charger for that size engine.
The real problem is using a charger this big and aiming for only 7 lb of boost. With the super-low drive ratio required, the charger is running so slowly, it isn't very efficient in the idle-3,000 rpm engine range, risking some of that positive displacement instant-boost goodness.
Hence my question. What is a reasonable drive ratio for the 1300cc engine and M45 combo? What is the reasonable limit of boost & static compression ratio? According to the calcs sheet on:
http://www.sprintex.com.au/ 9 lbs of boost on a 1300cc will give 135 hp at 6500rpm.
The calcs are all really wooly since teh allowances for losses are wild guesses and the charger is being run off the chart (at the low end). I'm keen to know people's real experiences with them.
I'm asking because I have a spare M45 lying around in the garage
M
