The disadvantage of vane-type superchargers has always been the rubbing friction of the vanes. Here Judson have shown excellent engineering know-how by mixing food common sense with the very latest techniques. The Judson’s vanes are at an angle (not radial), so that the centrifugal forces are virtually, but not quite, canceled. Additionally, the vanes (or blades) are made from a laminated plastic material which weights half as much as aluminum and which is dimensionally stable at all temperatures from 50 degrees below zero to 300 degrees Fahrenheit. Similar vanes are used commercially by Ingersoll-Rand (portable air compressor) and Thor Power Tool (air-powered grinder). A small amount of lubricant is used (about one quart per 1000 miles) but the exact amount is not at all critical. For this purpose, Judson supplies with the kit an aluminum rocker arm cover which incorporates a metering valve,
the best boost in go
for the least in dough
readily adjustable to give one drop of oil every 4 to 6 seconds at idle. Incidentally, the lubricant is SAE 10, or Marvel Mystery Oil. Judson warns, "do not use any other type or brand of upper cylinder lubricant, as most top oils are primarily a cleaner and not a lubricant." To which we can only add "Amen."
Insofar as the driver’s job is concerned, there is absolutely no difference in any way. We did encounter some clutch slip after five consecutive "all-out" standing starts. For the flat-out, always-on-the-floor type of driver, the special competition clutch is necessary. but we honestly feel the most MG owners will not need, or want, the heavy-duty clutch.
The engine itself sounds no different when supercharged. Peak bearing loads are actually decreased, because the higher combustion pressure opposes the inertia forces which tend literally to throw the piston up into the cylinder head. Occasionally there is faint noise ( a sort of clatter) from the vanes. This is normal and no cause for concern.
The car tested is the property of Bill Corey, who writes our monthly "Tune-Up Clinic." It received no special tuning at his shop and is, according to its owner, not so good a performer as some other examples which have received the same treatment. Judson recommends that a Bendix fuel pump be used for speeds over 90 mph (one way). However, this run was with top down and with the continental kit shown. The latter item may not seem important, but we ran parallel tests for drag losses on the Tech Ed’s MGA and got the following data with the Tapley meter at 60 mph:
|
|
|
Stock/ |
Test Car |
| Test weight, ton |
1.080 |
1.195 |
| Calculated rolling resistance |
20 |
22 |
| Tapley drag, top and |
|
|
curtains up, lb/ton |
90 |
- |
|
Same, lb force |
97 |
- |
| Tapley drag, top down, |
|
|
lb/ton |
100 |
107 |
|
same, lb force |
108 |
127 |
| Net air drag, top |
|
|
|
down, lb force |
88 |
105 |
From this it is obvious that the continental kit makes for considerable extra air drag and has a marked effect on the
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