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3.7 Roadster rev hang - how do you drive around it #606978
08/12/19 04:50 PM
08/12/19 04:50 PM
Joined: Oct 2010
Posts: 142
returned OggieMogger
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Roady Offline OP
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Joined: Oct 2010
Posts: 142
returned OggieMogger
I drove one recently and am perplexed how those of you who own one 'drive around' the issue.

I found it difficult in first and second (since advised to pull away in second) but not a problem once in third and above. I'm not a hot shoe driver so wouldn't be piling on the revs at every opportunity.

Your thought would be welcome.

Re: 3.7 Roadster rev hang - how do you drive around it [Re: Roady] #607001
08/12/19 06:56 PM
08/12/19 06:56 PM
Joined: Feb 2016
Posts: 2,632
East Harling, Norfolk UK
Richard Wood Offline
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Richard Wood  Offline
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Joined: Feb 2016
Posts: 2,632
East Harling, Norfolk UK
This subject has been much discussed. Rather than repeat and if you have an hour or two to kill innocent some threads on the issue starting here then here and finally here.

The quick answer though is whilst there have been some noteworthy attemtps to cure it there is currently no simple or economic solution.


Richard

2018 Roadster - Red/Magnolia - "Morton"
1966 Land Rover series 2a SWB
1960 Velocette Venom
Re: 3.7 Roadster rev hang - how do you drive around it [Re: Roady] #607006
08/12/19 07:16 PM
08/12/19 07:16 PM
Joined: Aug 2019
Posts: 136
Cheshire
Themorganeer Offline
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Cheshire
This issue has previously been aired on a few occasions. The latest being the thread “Roadster 3.7. - Any known issues” from early August.

Unless the ECU has been sorted such that rev-hang does not occur, under certain road conditions these cars can remove all control from the driver until the engine revs decide to settle down.

Once the engine revs rise above its tipping point, even via the rear wheels loosing traction on oil dropped onto the carriageway, instant release of the accelerator will not stop the revs howling for a few seconds. If a wheel then bites, the car shall be unceremoniously dumped into the scenery.

If on a dry straight road on changing up at over 4K revs there is a violent twitch from the rear, either walk away while you can or get the ECU fixed.


Chris
2015 Plus4
Re: 3.7 Roadster rev hang - how do you drive around it [Re: Themorganeer] #607008
08/12/19 07:18 PM
08/12/19 07:18 PM
Joined: Oct 2013
Posts: 6,539
Northamptonshire UK
Stringers Best Mate Offline
Talk Morgan Sage
Stringers Best Mate  Offline
Talk Morgan Sage

Joined: Oct 2013
Posts: 6,539
Northamptonshire UK
Originally Posted by Themorganeer


Unless the ECU has been sorted such that rev-hang does not occur, under certain road conditions these cars can remove all control from the driver until the engine revs decide to settle down.



What a load of rubbish.


Steve
Re: 3.7 Roadster rev hang - how do you drive around it [Re: Roady] #607009
08/12/19 07:21 PM
08/12/19 07:21 PM
Joined: Aug 2019
Posts: 136
Cheshire
Themorganeer Offline
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Cheshire
Opinion not shared


Chris
2015 Plus4
Re: 3.7 Roadster rev hang - how do you drive around it [Re: Themorganeer] #607019
08/12/19 08:20 PM
08/12/19 08:20 PM
Joined: Apr 2017
Posts: 1,097
Staffordshire
IvorMog Offline
Has a lot to Say!
IvorMog  Offline
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Joined: Apr 2017
Posts: 1,097
Staffordshire
Play nicely boys.

I'm personally not a fan of fly by wire systems but all modern cars use them and as a generalisation they are very reliable. Even a throttle return spring can break and leave the throttle wide open on older cable operated cars.

However Chris, if it really was as dramatic as you suggest, there would have almost certainly have been fatalities or at least serious accidents and the VCA would be crawling all over Morgan to resolve the issue. I'm certainly not aware that this is the case.

I'm sure there are some rev hang issues (I'm not a Roadster owner) but I don't think unsubstantiated scare mongering helps.

If however it is as bad as you say, and you have evidenced it first hand, who have you reported it to?


Bob

1999 4/4 2 litre Zetec
Re: 3.7 Roadster rev hang - how do you drive around it [Re: Roady] #607023
08/12/19 08:48 PM
08/12/19 08:48 PM
Joined: Apr 2008
Posts: 8,731
Gloucestershire, UK
Hamwich Offline
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Hamwich  Offline
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Posts: 8,731
Gloucestershire, UK
Maybe I'm completely off-beam here, but as I understand it, the reason 'rev hang' occurs is because the ECU manages the revs in such a way as to ensure excess fuel is burnt rather than being chucked out the exhaust port. The fuel supply can be cut as soon as the pedal site registers 0 (ie no torque demand), but there's still a fair amount of fuel in the inlet tract that needs to be burned, hence the revs not falling as quickly as one might expect as the car transitions down to meet the target RPM/torque demand.

I find it difficult to imagine that an ECU which is registering a pedal site of zero and a current RPM which is greater than the target RPM is going to do anything other than manage the revs down as cleanly as it can. The idea that it's suddenly going to apply sufficient fuel and revs to supply a torque demand that isn't there is pretty fanciful in my view.

My car rev hangs a bit, as I suspect many cars with FBW throttles and clean-running engines do, but all I do is release the throttle marginally before depressing the clutch rather than after, and ensuring my clutch in/out movement on upchanges is as smooth and quick as possible to maintain drive. I also tend to either short-shift when I'm driving normally or hang right on to gears when I'm pressing on. In my experience rev-hang is only an issue in that intermediate stage when one is changing up at around 2500-3k rpm. If I change up at 2k or under or 5k or over I never have a problem. Admittedly 5k rpm in a 165bhp car is a bit less intimidating than 5k in a car with another 100 or more bhp on top, but hey, nobody buys a 3.7 Roadster because they want to drive like a pussycat, do they? smile


Tim H.
1986 4/4 VVTi Sport, 2002 LR Defender, 1957 R4 CV, 2005 Ferrari Vipar
Re: 3.7 Roadster rev hang - how do you drive around it [Re: Roady] #607024
08/12/19 08:54 PM
08/12/19 08:54 PM
Joined: May 2011
Posts: 1,061
Seamill, Ayrshire
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Max5 Offline
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Seamill, Ayrshire
The question really is why should you have to? I have owned two 3.7 Roadsters and both suffered from rev hanging to various degrees among other electronic vagaries. Through my dealer MMC offered to fix the problem on receipt of £2k on top of the £53k I had paid for a new car! I declined and got rid of both and bought a 4/4!

Re: 3.7 Roadster rev hang - how do you drive around it [Re: Max5] #607027
08/12/19 09:11 PM
08/12/19 09:11 PM
Joined: Apr 2008
Posts: 8,731
Gloucestershire, UK
Hamwich Offline
Needs to Get Out More!
Hamwich  Offline
Needs to Get Out More!

Joined: Apr 2008
Posts: 8,731
Gloucestershire, UK
Originally Posted by Max5
The question really is why should you have to?


Because MMC lacks the resources to develop a custom engine management system that is tailored to the car characteristics, works with the dash module and immobiliser, and is fully emissions compliant in all the territories the car is sold in?


Tim H.
1986 4/4 VVTi Sport, 2002 LR Defender, 1957 R4 CV, 2005 Ferrari Vipar
Re: 3.7 Roadster rev hang - how do you drive around it [Re: IvorMog] #607031
08/12/19 09:21 PM
08/12/19 09:21 PM
Joined: Aug 2019
Posts: 136
Cheshire
Themorganeer Offline
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Themorganeer  Offline
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Joined: Aug 2019
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Cheshire
Hi Bob

Originally Posted by IvorMog
Play nicely boys.

I'm personally not a fan of fly by wire systems but all modern cars use them and as a generalisation they are very reliable. Even a throttle return spring can break and leave the throttle wide open on older cable operated cars.

However Chris, if it really was as dramatic as you suggest, there would have almost certainly have been fatalities or at least serious accidents and the VCA would be crawling all over Morgan to resolve the issue. I'm certainly not aware that this is the case.

I'm sure there are some rev hang issues (I'm not a Roadster owner) but I don't think unsubstantiated scare mongering helps.

If however it is as bad as you say, and you have evidenced it first hand, who have you reported it to?


In response to your query - Yes absolutely - full facts reported to DVSA, following zero interest from MCC, complete with independent witness details.

DVSA's comment on receipt of report "Unfortunately, as you are no longer the owner of the vehicle then any communications between DVSA and the manufacturer with regards to this matter, are considered non-disclosable".

I have no issue with this and have since moved on, but feel duty bound to warn of the potential risk associated with this particular car under certain road conditions.

Trust this clarifies.


Chris
2015 Plus4
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