ODD REVING 1600 S/Sport

[James Saunders]

I have a 1600 k-series supersport which when u blip the throttle and the engine revs it takes a long while before the revs die down again .. if your in slow traffic and dip the clutch the revs hover for a few seconds then drop. Does anyone know what this may be or have had any similar experience with a 1600k ???

Also, has anyone managed to get the shift-up light on ???!!!!

[oilyhands]

The K is renowned for sticking throttle bodies, the plastic body can easily distort and stop the butterfly from closing properly and rapidly, this can be exacerbated by the clip which attaches the filter to the TB, if it is overtightened it can pull the TB out of round. There are a variety of other possible causes, sticking throttle cable, sticking IACV, air leak, duff connection to TPS or other sensor, but I would check the TB first.

 

oily

[Sid Spalding]

Yes I have a similiar behaviour with my SS. I also have a lightweight flywheel and before building was expecting a very quick fall off of revs after lifting the the loud pedal. However my feeling is that there is just too much inertia in the system to allow the revs to fall away too quickly - this is underlined when you switch off a hot engine (i.e. with the fan going). Instead of the engine stopping immediately, it keeps going for 2-3 seconds, (I assume) becuase of the inertia of the fan.

Yes I also get the revs continuing after I dip the clutch - can't explain that one.

 

Change up light - I assume you have taken it round to 7400-7600 (I think that's the rev limit) ?? I know I didn't dare until a friend was showing how to drive Gurston Down and drove the course "slowly" for me (in my car). I saw the change up light then between the gaps between the fingers over my eyes ! The small black cable can easily get snagged and come loose at either end, so it's worth checking.

 

cheers

 

Sid

W77 CAT

[Peter Carmichael]

Will Paul has this on his Superlight. We experimented by running my Emerald ECU on his engine and it fixed everything.

 

The main differences are probably to do with the vacuum tube that runs to the ECU. The vacuum is used to sense the throttle pedal position; the throttle potentiometer is only used to sense transients on the Rover MEMS. The Emerald only uses the throttle potentiometer, which means that it is set up for a particular altitude and particular barometer reading.

 

Make sure the vacuum hose is clear and make sure it seals properly onto the fuel trap and ECU connections and has no constrictions.

 

There may however be a problem with later ECUs because my '97 Supersport revs cleanly.

[Mike Bees]

Most modern product setups are like this, it's for emissions purposes AIUI.

 

Mike

[oilyhands]

I suppose this comes down to the *extent* of the problem, modern EMSs do tend to dampen a closing throttle using the IACV in order to reduce hydrocarbon emmissions, if the soaring throttle has always been there and its not too excessive it may be the ECU doing what comes naturally, if it's a recent phenomenon and is *excessive* then it probably isnt normal and may warrant further investigation.

 

oily

[R500 CYA]

My 1.6SS does this too, don't worry it's quite normal. wink.gif

 

As for the shift light, get on a track day, put on a crash hat and switch off your brain. I guarantee you'll see it on all the time!

 

Nick

[mike ashurst]

Mine was OK until the MOT man decided to try and reduce my idle speed for the emissions test (Not required, long story, don't get me going on that one!). Now it intermittently holds its Revs when I lift off. I've re-fiddled with it, but it's still not perfect. More fiddling required this weekend.

 

Mike

[Mike Bees]

What on earth did he fiddle with?

 

When the car is up to temperature and idling normally, try disconnecting the idle air control valve and see if that cures the problem (sticky IACV isn't uncommon). Disconnecting the IACV will stop the ECU from "bringing the engine in to land" slowly.

 

Mike

[CHRIS CLARK]

On way back from area meeting tonight we had the shift light on several times. A few of the changes were perfectly timed so that the light just blinked as I was 'on the change'; great! Nice 'n' bright at night!!

 

When I first went to fit the change light (it had been missed off at original construction)I had a duff 'light' (it'sjust a jumbo L.E.D.+ resistor). Kept banging it off the hard limiter (7600) with no sign of a light. Removed it and tested it on 12v battery; nothing! Parts dept at Caterham said when I returned it that that was the problem. It needed more than 12 v to work! mad.gif (240v perhaps? Dur). Needless to say, I proved the point and got a new 'un out of Caterham. That worked fine!!!!!!!!!!!

[James Saunders]

Many thanks for all your comments. Now I have a few things to try and it puts my mind at rest knowing its not an uncommon fault.

 

Thanks

James S