Anders T.

My 1997 993 is going to have a totaly new programable ECU. We have only one issue left - the Varioram system. At what Point these valves shall open and close. Yes - I have made a search and I have bought the workshop manual, but can someone explain to me when they shall operate. Today we got 318 hp but the tourqe curve and values is no good. If someone has a qlue - please let me know.

//Anders T.

Bill Verburg

Not sure on am M64/21 motor but for the M64/20 RS

sliding valves
in the long position from idle to 5160rpm
then at that point if the throttle is at least 50° open they shorten

tuning flap is closed from idle to 5920rpm where it opens if throttle is more than 50° open

bcameron59

Can't vouch for accuracy but here's some sources with similar rpm values to Bill's info for non-RS motors. Apparently varioram was introduced on 964RS so seems reasonable that standard motor and RS kick in varioram at about the same RPM range.

5000 rpm:
http://www.excellence-mag.com/issues...4#.UnlpcTK9KSM

5200 rpm:
http://www.instant-g.com/Products/36...sion/VRAM.html

Bill Verburg

Ok for the M64/21 I believe the #s are 5000 & 5800
there are;
2 throttle plates
6 sliding pipes and
one tuning aka resonance flap

There are 3 modes for the system, for M64/21 and for M64/20 the modes are the same but the transitions are at different rpm

Mode 1, aka vibrating induction mode, idle to 5000rpm
only the top throttle is open, the 6 tubes are in long mode(ie there is no gap open to the resonance chamber because the tubes are fully extended), the tuning flap is closed

Mode 2, from 5000rpm to 5800rpm, Resonance mode 1, the tubes have been retracted, opening the gap to the resonance chamber, both throttle plates are open, the long pipe aren't really used here as most of the air is transferred from the 2 resonance chambers, alternately from one side then the other.

Mode 3, from 5800rpm to redline, Resonance mode 2, the resonance flap connecting the 2 sides of the resonance chamber opens, increasing the resonance frequency

as w / the RS the throttle needs to be open at least 50° , for the transitions

vram was never used on 964, it was first used on the '95 993RS

the first resonance intake was used on '84 3.2 Carrera, where it was of a fixed design. It became variable on the 964s(including 964RS), w/ a single tuning flap on the connection between the 2 resonance tanks. 964 RSR also used a variation of this single flap variable design but w/ ITBs. The 964 variable went through 2 phases, early w/ aluminum manifold and late w/ plastic manifold, The late 964 resonance design w/ slight mods also was used on '95 993.

Here's the Theilart manifold and ITB setup used on the 964 RSR

bcameron59

Uh oh, bad info on wickedpedia:

"VarioRam is a Porsche-patented engine induction system that was first introduced on the 1992 model year 964 Carrera RS motor sport special. It became standard on the 911-series starting from the M64/21 engine on the model year 1996."

http://en.wikipedia.org/wiki/VarioRam

Just goes to show, ya can't believe everything you read on the interweb.

hkspwrsche

My wife teaches 8th grade science and every year must explain why they can't use wikipedia as a resource. Unfortunately it not perfect.

geolab

The figures I have
On the M64-21:

Engine Shut, not contact........Resonance (or tuning) flap open
Engine shut, key on contact....Resonance (or tuning) flap closed
Engine idle............................Resonance (or tuning) flap open
0 rpm to 3250 rpm...............Resonance (or tuning) flap open
3250rpm to 5520 rpm ...........Resonance (or tuning) flap closed when throttle position > 60*
5520rpm to 6640 rpm............Resonance (or tuning) flap open

Varioram extensions (tubes) solenoids (vaccum) are triggered electrically by DME @ 5160rpm, throttle position should be 60*+ (RS is 50*+)

throttle position switch:
max WOT is 84* +/-3
full load 66* + > on M64-21

Bill Verburg

The RS #s I got from the factory RS manual, the M64/21 #s I got from Frere

Just for giggles and to confuse everyone here's another set of factory #s for the M64/21 from
Porsche Technical training Course P21
As Geo mentions all the solenoids cycle on key on, so we start at idle
where the tunong flap and sliders are in their home positions, flap open sliders long

at 4800rpm and throttle at least 50° sliders shorten

at 5840rpm and throttle more than 50° tuning flap opens

at 6640rpm tuning flap closes

Here's the accompanying intake volume map

Bill Verburg

Just so the '95 993 guys don't feel left out, per the P21 training manual
flap open from idle to 3000rpm
flap closed from 3000 to 5500rpm if throttle is > 60°
flap open 5500 to 6640rpm if throttle is > 60°

Anders T.

Thanks a lot. Still a bit confused, but I Think I got the M64/21. Will do my homework!
Thanks again.


Anders T.