924Board.org

[BionicBalls]

This comes up every so often, but it's been awhile so I figured I'd respark the discussion.

Found this site while searching:

http://www.selendesigntech.com/xFranco.aspx

Now who's going to start reproducing them?
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1980 924 NA
1982 931

[fiat22turbo]

I have one and I've thought about reproducing it.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[tyfighter123]

Group buy? fiat how much would you charge to make one?
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Porsche 924 1977 N/A
Mustang GT/CS 2007
Porsche 924S 1987 (parts car)(cut up and recycled)
Porsche 911S 1976
Porsche 931 1980
Porsche 931 1980 (parts car)

[ideola]

My Franco gear is at a specialty transmission gear shop at the moment, being reversed engineered...have already come up with one improvement for the front plate...
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erstwhile owner of just about every 924 variant ever made

[Martijnus]

I've been thinking about this lately too... but I don't know how much influence it'll have.

variable mechanical stuff is always cooler than electronics.
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"Rule: Turbo's make torque, and torque makes fun." (C. Bell)

924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment

[ideola]

The Franco gear is ideal for a DITC-equipped 931 running on CIS...

On the non-DITC cars, it has a tradeoff because it will affect ignition timing as well as cam timing since the ignition distributor is run off of the cam drive gear. On DITC cars, ignition timing is independent of cam timing, so this could be the ideal combination.

If the guys I'm working with can come up with a design that overcomes some of the inherent flaws in the original unit, I am going to try it out on the Club Sport motor. I know of at least one example where a very expensive 931 head was ruined because of a failure of the Franco gear. I have a design in mind that should eliminate that particular failure mode.
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erstwhile owner of just about every 924 variant ever made

[Martijnus]

Too bad both intake and exhaust lobes change, but there's no way around that. Better than having nothing at all.

Ideally it would be nice to be able to tweak the advance...by means of movable centrifugal weights, different spring loads (least challenging) or whatever and a possibility to use it as a timing sprocket too.

Dan, aren't the springs the weak link in this system? Springs fail/stretch over time and advance the camshaft to the max resulting in molested intake valves...?
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"Rule: Turbo's make torque, and torque makes fun." (C. Bell)

924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment

[Shurick]

[ideola]

It's hard to describe, but the way the unit works, is that it *retards* at max RPM. Retard is physically limited by the design of the housing, so if the springs fail you would be running at max retard, not the other way round.

The failure mode I am referring to above was not the springs, it was part of the design of the housing.
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erstwhile owner of just about every 924 variant ever made

[ideola]

[ideola]

[924-76]

[staticsan]

Intruiging idea. Some car makers put such a gear in as stock; I remember seeing one on an engine in the Sydney Motor show not too long ago. It was a DOTC engine, though, and it was only on one.

There is a way to for it to not retard the timing in a non-DITC engine, but it would be difficult to engineer. The trick would be to use a concentric cam: the outer piece has all the lobes for the lifters, and the innner shaft is what sticks out the back for the distributor. You would then need to modify the centrifugal gear so that the weights change the outer cam shaft whilst the inner one is simply driven directly.

Wade.

[gegge]

[ideola]

Wasn't able to get the info just yet, will have to wait now until after the holiday weekend ("Labor Day" here in the US...which is ironic since we all have the day off...!)
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erstwhile owner of just about every 924 variant ever made