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

That's what I thought but Steve19 above says he has it on a 2009 / 2010 Series 2

Maybe the cable sticks

I know at least 2 owners of S2, S3 Roadsters who had problems with rev hang, one completely fell out with it (and the dealer) and chopped it in for an Aero 8

Isn't it all down to the programming of the ECU, the cause of rev hang can be put down to the war on emissions .Manufacturers have been intentionally implementing rev hang within ECU programming to save themselves from a potential emissions problems. When the throttle is released and the clutch is dipped, an ECU with rev hang is programmed to leave the throttle slightly more open than usual.

This strategy is used because it was found that suddenly closing the throttle produced a sudden spike in gas pressure within the crankcase which emphasised the rate of oil vaporisation, thus adding to emissions from the engine. Also, when the throttle is suddenly shut, the fuel mixture suddenly becomes lean which creates NOx (oxides of Nitrogen) which also contributes to emissions.

So may have little to do with cable or fly by wire throttles and down to ECU programming. I think I have experienced a little rev hang in my series 2.
regards

But if it's a cable operated throttle body, when you take your foot off the pedal the TB will close.

With fly by wire throttles, you could programme the ECU to stay open a bit but not with a cable throttle.

Unless the ECU opened the idle air valve a bit on the cable throttle cars to allow some air in.

When the S2 Roadster came along there were occasional stories of lazy throttles but not every car suffered, and the S3 was the same.

Another related question.

Is there any physical difference between the S1 & S2 lumps as in the bottom end and basic head etc?

Simon mentioned the cams, induction and ECU are different but what about the basic architecture?

All 3 liter roadsters had a throttle cable. Nevertheless, with my S2 the rev hang was extremely pronounced and so bad and long lasting that I had zero engine brake after downshifting downhill before corners. Driving was absolutely no fun. Even though the throttle was closed immediately by the cable, the rev hang occurred with the help of the idle air valve controlled by the ECU. As I wrote above, otherwise it was a great car and with the new ECU even more so.
Only the new ECU had transformed the car into a very fantastic driveable one.

John Harris has absolutely hit the spot. It is exactly these reasons why there was a rev hang. Historically, it was the first intervention in automotive development that put other interests above pilot control. I have great sympathy for the reasons for this intervention, but from a driving perspective it was frustrating...as long as you didn't just roll along unsportingly with the car and in these cases, rev hang was sometimes not even noticed.

Interesting Heinz, I thought it was only the 3.7l that suffered this.

Heinz, that is very interesting.

I think most people think of the ECU controlling the throttle, fueling etc.

But on a cable operated throttle body the Idle Air Valve does indeed act like a miniature drive by wire throttle body so rev hang could occur by the programming of the table in the ECU that controls the IAV.

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.

BTW it was the same flywheel so that did not affect the inertia of the engine.

Fascinating subject.