Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Roadster S1 v S2

The mass flywheel is often mentioned as a possible solution in connection with the rev hang. Believe me it makes virtually no impact. On the S2 Roadster, you might suspect this effect of the large dual mass flywheel...as long as the rev hang is programmed. But with the other ECU without rev hang, the RPM goes down very nimbly even with the dual mass flywheel.

The effect of the programming is greater than that of the mass size.

Another example. I had other problems with my 4/4 a year or more ago. To make it short, a switch under the brake pedal was defective. A bumpy loose contact made for ugly and stuttery driving. Before mounting the new switch I experimented with two modes, a) the electrical connection permanently disconnected (corresponds to the ECU program while braking) and b) the electrical connection permanently with contact (corresponds to the ECU program while driving without brake).

a) lowers the engine speed more decisively and faster so that the braking effect is greater. But if you drive with it all the time (which I tested) everything is too rich in the mix, the exhaust turns black, the lambda sensor gets dirty and the consumption increases dramatically. But lowering the engine speed is much more effective. You would think the flywheel has much less mass.

b) ensures the right gasoline/air mix when driving. Fortunately, the programming does not cause any detrimental rev hang at all. But the engine speed drops much slower than under a). When braking with permanently bridged contacts of the switch under the brake pedal (which would be interrupted by the switch in normal operation), you work against the slower falling engine speed when braking.

I want to say with the two examples, (Roadster S2 and 4/4 Sigma) that there can be a psychological deception and that the programming can have more effect than the physical mass.

Heinz,

Although I have only only done about 100 miles or so in my S2 I find the rev hang is more pronounced at higher engine revolution gearchanges, hardly noticeable below 2500rpm, the rev hang duration increases significantly at higher revs. I'm adapting my change gear timing accordingly, at higher rpm it almost feels like the time it used to take to double declutch, although in reality it is just a second or 2 longer duration over the gear change. to allow the revs to fall. On an engine braked down hill descent it must be extremely frustrating. I used to detect what I suspect was rev hang at higher revs on my Duratec 4/4 at very high revs, I suspect any vehicle with an EGR fitted may have some ECU rev hang to reduce emissions further.

Regards

John

Even some 4 cyl cars suffer eg, the 4/4 with the 1800cc (silvertop & some blacktop's)

I had severe rev hang on my 2002 4/4. I was told it was due to emission concerns as John Harris explains.
It was a good sales technique though as it drove me potty and led me to buying a roadster in 2004 when I could stand it no more!
Mine was a series one, an early one, and it's my belief that the factory had worked really hard on all aspects of that model, from the position of the gear lever to the electronic programming, everything was just right....except the dreadful nylon type front bushings which I had to change back to bronze.
I think it was a high point for the factory; they hadn't just adapted anything from a previous model as easily as possible, they had really tested everything out before releasing it.
There was a very tiny bit of rev hang but it was hardly noticeable, I think they had reduced absolutely as far as possible in that car.
Nick

Jon, you're absolutely right I think. That's what I meant by my previous post.

Back then I don't think I had put 2 and 2 together but now I can see it was a basic form of rev hang and it really did slow down the upshifts. You could of course just bang it though but that would not be very kind to the drive line.

Now here's a thought. My Omex ECU can be set up for full throttle gear changes where it kills the spark when the clutch is hit at high revs.

I wonder???

"When I think back to my early experience with my old Zetec, I had forgotten that I used to feel that the gearshifts were slow because it took too much time for the engine to slow down on upshifts.

When I changed the ECU to Omex and was able to programme the IAV to my requirements, the gear change was much slicker because the IAV remained closed under those circumstances. In effect, slight but noticeable rev hang."

I fitted the restrictor plate to the idle control valve thingy on my yr2001 4/4 but the difference was a bit subjective...
Fortunately when we sold our boat SHMBO agreed to a Mog upgrade to an almost new S1 Roadster, best Mog of the 5 I've owned

I am coming rather late to this interesting thread. Mine is the 100 Edition 3.0, registered June 2010. Were all the Centenary Editions S2 or could mine be S3 (and how would I know, as MMC told me there was no 3.0 S3)? If it helps, I have not experienced any rev hang thus far - all of 10 days.

Hi. I have a 2010 S2 and would like to do the ECU change, mentioned in the article here, where can I source the ECU and is it a mod I can do myself or do have to have some re mapping done?

Thanks

Librands used to sell them

I'd have a word with Henry at Williams.

They did the re-map on my 2009 Series 2 Roadster and might be able to suggest a way to provide an exchange ECU or something similar.

Only an idea, don't know if it's possible.

Librands and Williams are now "related" but I think the current Librands offer is only Series 1.