Quote:
Originally Posted by Supercharged_Z
bedfordshire near aylesbury, i think the x mas meet is in bluewater kent iirc
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the way i saw it was that the oil is what lubricates and cools the gears. once the oil has been sprayed onto the gears it has done its job and needs to be evacuated as quickly as possible as it is now hot. the gears have no clearance between them . they are meshed tightly and so when using the oil return higher up you have an oil bath. the oil cannot escape from between the gears as they mesh and that is what loads it up and causes all the heat. we bench tested the theory. we ran the charger with a drill with the snout off. then applied lots of oil and the drill slowed down alot where the load had increased. so we found that just the oil jet was ample lubrication.
here is a small article about cam timing when using supercharger instead of naturally aspirated. every bit of research i do says the same thing. reducing valve overlap, reduced inlet duration and increased valve lift are the modifications required. im trying to get a new set of cams made but piper insist that their 270 durations cams for naturally aspirated will do the job. but george at rsm has already advised me that they do not work as he has already tried. was it you and your car that george has been helping with
Intake cam:
Because of the negative effects of overlap on a supercharger car's performance, and especially in the case of high exhaust back pressure as is the case with most factory supercharged cars, we find that the optimal cam duration for the intake cam is typically 30-40* of duration less than a normally aspirated camshaft for the same peak power RPM. The decision to reduce the intake cam duration rather than split the duration reduction between the intake and exhaust cams, is that the intake cam will flow air under pressurized conditions (due to the addition of the supercharger and the increase in intake manifold pressure) and so at a reduced intake cam duration the engine will still be able to get it's full share of intake air. At the same time, the high rpm efficiency improvement from the reduction of overlap will also boost power production with a more conservative cam. Finally, if we would like to get more flow from the intake cam, there is still the option of using a higher lift camshaft (with a steeper profile due to the decreased duration) with supporting valve train modifications to make sure valve float doesn't occur at higher rpms.
Intake cam timing:
The cam timing for the intake cam would ideally be retarded which would move the intake cam opening event farther away from the exhaust valve closing event so as to reduce or eliminate overlap, and as a side effect the power stroke duration will increase by retarding the intake cam which can also compensate for the lost power from the duration reduction.
Exhaust cam:
The exhaust cam duration and lift for a supercharged version of the motor should be similar to a nitrous camshaft, in the sense that the exhaust cams on nitrous specific builds have:
1- Very healthy cam duration & very healthy cam lift to allow a severely elevated amount of exhaust gases to be able to efficiently exit the motor when the nitrous is activated and the horsepower (and thus the exhaust gasses) have both doubled in quantity.
2- As little or no overlap if possible, as any overlap would mean that nitrous would be sprayed from the intake side and out the exhaust, which is wasteful of our limited supply of nitrous. Similarly the more overlap we have, the harder the supercharger will have to work because of what we explained earlier about either exhaust reversion into the intake, or the supercharger pressurizing the exhaust.
Exhaust cam timing:
Advancing the exhaust cam both opens and closes the exhaust valves sooner. Opening the exhaust valve sooner slightly reduces the power stroke, but at the same time it reduces overlap and makes better use of our supercharger. Typically an an advanced exhaust cam combined with retarded intake cam will provide the best results on a supercharged car, especially with a restrictive exhaust.
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