Smooth Performance...

[Cosmos*]

I've been meaning to ask this question for ages...

When I'm driving at lower speeds, eg, 30 mph and under or around town, my chim's ride/performance isn't smooth at all. It's "lumpy" and progresses along in a series of mini jerks/lunges although there is no loss of power (sorry if this sounds odd, I'm struggling trying to find the right descriptive words). It's almost like the car is protesting at going slow if that makes sense.

Can this be considered as relatively normal to a degree or is something amiss?

[the dodger]

This is another "TADT, Sir" But some are worse/better than others. Mine is very jerky/uncomfortable below about 2500 on a constant throttle. I live in a 30mph village so the only way to progress is with suirts in 2nd gear! I am sure this problem can be cured/minimised by a visit to a rolling road with Mark Adams (the ECU chip Master) in tow. Something I've promissed myself later in the year.

[GreenV8S]

Depends what gear you're in. It seems normal for them to get a bit hickupy (technical term) idling along at low RPM. How low you can let the revs drop before it starts complaining varies from car to car (and from day to day) but 1500 RPM is typical. You're better off dropping a gear to keep the revs nearer 2000 RPM, this avoids labouring the engine and also gives more throttle authority for acceleration and braking (if the engine is at tickover you get precious little of either).

[shnozz]

i assume the stepper motor has been cleaned?

[hut49]

Cosmos* said:

Can this be considered as relatively normal to a degree or is something amiss?

Something's amiss - but it maybe difficult to identify the fault without diagnostic kit - I don't recommend the hit and miss approach of.. it might be the coil.... or the HT leads ...or etc. You can spend a fortune and get nowhere. If you're in the S East are you near Dorking? If so give Motorvation a call 01306 877047 - they know v8 TVRs, they've got dyno/rolling road facilities and staff with attention to detail. Small shop that gives good value for money.

>> Edited by hut49 on Sunday 18th January 23:04

[Apache]

A common problem, see this thread


www.pistonheads.co.uk/gassing/topic.asp?h=0&f=23&t=70243

[HarryW]

hut49 said:

Cosmos* said: Can this be considered as relatively normal to a degree or is something amiss? Something's amiss - but it maybe difficult to identify the fault without diagnostic kit - I don't recommend the hit and miss approach of.. it might be the coil.... or the HT leads ...or etc. You can spend a fortune and get nowhere. If you're in the S East are you near Dorking? If so give Motorvation a call 01306 877047 - they know v8 TVRs, they've got dyno/rolling road facilities and staff with attention to detail. Small shop that gives good value for money. >> Edited by hut49 on Sunday 18th January 23:04

I think you'll find that motorvation moved to gatwick and now are called Austec (check advertisers on here for contact details) , heartedly recomended, good guys . Particulary as they have the rolling road so can monitor the car whilst its mis-behaving on the move, so to speak, which is worth its weight in gold for running faults IMHO.

Harry

Harry

[hut49]

Thanks for that - wondered why I couldn't find their website! Should have checked before posting

[cosmos*]

HarryW said:

I think you'll find that motorvation moved to gatwick and now are called Austec (check advertisers on here for contact details) , heartedly recomended, good guys

Have already paid Austec a visit a few months ago and I'm going to book my chim in for a service there too.

Anyway, thanks guys for the reassurance that it's not just my chim with a less than smooth performance at low speed/revs. So basically it would appear to be a general characteristic of the car which may be subject to some improvement if you look into it.

[shadowninja]

Which sort of petrol are you using? 98RON may solve the problem... unless you're already using it.

[N17 TVR]

the dodger said:

This is another "TADT, Sir" But some are worse/better than others. Mine is very jerky/uncomfortable below about 2500 on a constant throttle.

Ditto, mine was always about 2700 revs - although it is considerably better since I went and had a rolling road and re-chip session with Mark Adams (as recommended by Rog in his original post which I've only partly quoted).

Mark didn't pick anything specific up when doing his analysis, but the combination of a new chip / new fuel mappings made a big improvement.

Stepper motor cleaning on a regular basis doesn't hurt either.


>> Edited by N17 TVR on Monday 19th January 15:11

[wildego1]

I agree with shadowninja. I used to have this problem when I used to use Optimax, I think it's called transmission shunt. I now use bog standard unleaded 95 RON no problem's car still flies, no more shunt, a bit cheaper too.

[M@H]

I never experienced this problem with mine at all and found that it would "pull" from sub 1000 rpm in 5th quite happily.. obviously I was lucky ?

Cheers
Matt

[cosmos*]

Matt, it does "pull" okay without any loss of power but the ride is jerky until you reach higher revs/speed. Say you come up behind someone doing a constant 35 mph in 4th gear, you have to change down to get the revs higher to try and keep the ride smooth otherwise it's really irritating. It doesn't cure the problem but it helps to some degree. And then I overtake asap!!

I use Optimax but might try the 95RON to see if this makes any difference as in a process of elimination.

The stepper motor has been cleaned recently.

[Apache]

You could have a problem with pinking then

[Big Al.]

cosmos* said:

Matt, it does "pull" okay without any loss of power but the ride is jerky until you reach higher revs/speed. Say you come up behind someone doing a constant 35 mph in 4th gear, you have to change down to get the revs higher to try and keep the ride smooth otherwise it's really irritating. It doesn't cure the problem but it helps to some degree. And then I overtake asap!! I use Optimax but might try the 95RON to see if this makes any difference as in a process of elimination. The stepper motor has been cleaned recently.

Roz, drive mine on Sunday and see if it's any different.

>> Edited by Big Al. on Tuesday 20th January 17:21

[cosmos*]

You're brave!!

Donuts

[Big Al.]

cosmos* said:

You're brave!! Donuts

I'm Diabetic!

[V8 Archie]

cosmos* said:

you come up behind someone doing a constant 35 mph in 4th gear, you have to change down to get the revs higher to try and keep the ride smooth

I'd be changing down to get decent drive when I go past anyway .

Seriously, though I'd be unhappy if I needed 2500 for a smooth ride. Mine only gets lumpy at about 1000-1200. That might be partly due to extra torque, but I'd have thought that would work the other way.

Mind you 20mph is about the minimum speed I can do without any loss of comfort.

[M@H]

cosmos* said:

Matt, it does "pull" okay without any loss of power but the ride is jerky until you reach higher revs/speed. Say you come up behind someone doing a constant 35 mph in 4th gear, you have to change down to get the revs higher to try and keep the ride smooth otherwise it's really irritating. It doesn't cure the problem but it helps to some degree. And then I overtake asap!! I use Optimax but might try the 95RON to see if this makes any difference as in a process of elimination.

Hiya.. this really doesnt sound like a TADTS to me i'm afraid.. I could cruise happily at 30mph in 5th in mine, very smooth (I always used optimax).