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The low compression version of the M28.21 and M28.22 motors for Sweden, Switzerland and Australia have 9.3:1 compression rather than 10.4:1 compression, and 275 hp vs. 310 hp.
The factory literature is a bit of a mess on this point. The 1980-84 and 1985-89 Tech specs book lists all 1984 and 1985 M28.22 motors as being the 10.4 compression, 310 hp model, but in '86 they call out the low compression version for Switzerland and Sweden, while Australia got the M28.45/46 motor instead.
The factory workshop manual says that all 84/85/86 Swiss/Swedish/Australian cars got the M28.22 motor with lower compression, but then on the same page there's a listing for Australia, Germany, Australia and Switzerland getting low(er)compression M28.45/46 motors.
Confusing.
So- I am not aware of any external identifiers on the engine itself that would indicate it's a low-compression motor. The easiest thing to do would be to get a cheap USB borescope, pull sparkplug #1 and look at the piston dish, it should be pretty easy to differentiate. See picture below for the differences in the piston tops.
1985
C10 - Switzerland market
M28.22 - engine serial # range 82F 05001>10000
A28.06 - transmission serial # range 16 F 05001> 11000. A28.05 = 14:33 R&P (2.36:1) , A28.06 = 13:33 R&P - 2.54
M220- Limited slip differential
I415 - Widening of the gauge on the track on the rear axle
I454 - Automatic speed control
I525 - Alarm with continuous sound
I593 - Antilock brake system (Bosch)
M650 - Sunroof
I686 - Blaupunkt Hamburg SQM24
Samuel types faster than I do. Samuel, have you seen a Swedish or Swiss M28.21/22 that specifically calls out the low compression motor? I've never seen one.
Samuel types faster than I do. Samuel, have you seen a Swedish or Swiss M28.21/22 that specifically calls out the low compression motor? I've never seen one.
I don't think so
Your answer is much more complete than mine.
I haven't seen a low compression M28/21 or M28/22 for a European country so far, and I'm not sure that they were produced. My assumptation is based on the fact that the equipment code for these engines, M151, was only used on 1985 Australian 928s.
Thanks very much. I will try to source a borescope to be sure...but I’m now assuming (selfishly) its a 310 engine
The options do not list full leather interior...even though I believe it is the case (unless the vinyl really looks like leather). Is it possible all Swiss cars had that option? Here’s a picture of the interior:
The "75" on the sticker is the code that indicates the kind of interior, leather or leatherette, colours, etc. We don't know how to decode it, but you could check with any Porsche dealer if yours is correct or not.
04-05-2020, 01:49 PM
Samuel, have you seen a Swedish or Swiss M28.21/22 that specifically calls out the low compression motor? I've never seen one.
