General Sluggish Barchetta rev counter

Currently reading:
General Sluggish Barchetta rev counter

Unionfan

New member
Joined
May 27, 2022
Messages
8
Location
Confolens
Hello all. Our Barchetta's motor seems to be running just fine but when you press the throttle, the revs climb more slowly than we would expect for a 16v petrol engine..... Even our diesel Skoda's needle rises and falls much more quickly when we do the same thing. We don't expect our little green gem to accelerate like a Ferrari but we would expect to see the rev counter needle moving at more than a glacial pace if we're in the right gear. Is this an engine issue or a rev counter issue?

Interested to know what we should expect to see on that rev counter as if slow progress of that needle is normal then fab, no worries. :) Thanks.
 

ernibv

Member
Joined
Jan 19, 2022
Messages
92
Location
Leiden
How does the engine sound? The b has a very quick throttle response. Just don't trust any of the meters.
A simple test is to open the bonnet and listen. Does the engine rev in sync with the meter?
If the engine reacts the same as the meter, sit in the car and bring the rpm's up to 2k and hold it there. Within about 15 seconds the revs will climb to 4k without you doing anything. Does this happen ?
Sounds like a really standard Barchetta throttle control valve problem. Check the site. Lots of info.
grtz
ER
 
OP
OP
U

Unionfan

New member
Joined
May 27, 2022
Messages
8
Location
Confolens
ernibv, s130 and Davefridge, thanks for your thoughts.
I've tried the suggested activity and
1) the engine revs do rise in line with pressing the accelerator peddle (although there is a little slack in the peddle I think)
2) the rev counter does climb but not seemingly as fast as the revs rise (heard most clearly with the bonnet open)
3) first gear acceleration sees the rev needle climb quickly and in line with engine noise and speed
4) car accelerates slowly at anything under 4,000 revs.... not sure if this is normal or not.

Basically, it seems like if I floor the throttle in every gear, the car accelerates well and the rev counter climbs (albeit more slowly in 3rd, 4th and 5th). I know peak power isn't developed until something like 6,000 revs but is it normal that a barchetta engine has to be flogged to the red line to get something close to responsive throttle performance?

Thanks in advance again, folks :) Your advice for this newbie to barchettas is much appreciated.
UF
 
Joined
Dec 5, 2006
Messages
5,147
Location
Wrexham, North Wales
To be honest it sounds like there is nothing wrong with your rev counter based on your feedback to us.

I've never tried to map / correlate or "B"'s rev counter to the engine. All I know is that when driving, as opposed to revving in neutral, and going to max RPM I've never hit the rev limiter or had any other concern.

What you will find in *ALL* instruments the meter reading (needle or digital) will be damped to a lesser or greater extent. With a traditional volt meter this is plainly evident. With a pulse driven RPM/Frequency meter then the only way to gauge the dampening is is blow on, flick, hold and release the meter needle. You will find that the needle will be quite sluggish.

Not sure what else to add/say.
 
Joined
Dec 5, 2006
Messages
5,147
Location
Wrexham, North Wales
Thanks very much s130 :)
You are welcome. Dampening of instruments can be a tricky subject. Too little and the needles flap around all over the place (e.g. on a vacuum gauge where the vacuum pulses from 0 to max and back on each piston stroke) or too much when short term fluctuations from a normal level are over smoothed/integrated out.

On the electronic carb balancer, I designed for our 130TC, I had to do some heavy integration/smoothing of the differential metering circuitry. Old style manometers used for this purpose us either mercury (has large inertial mass) or use pinch/restriction screws in the vacuum lines.

Then you have the old digital speedo teaser. Am I doing 35 or was it really 34.n or even 33 or less as you passed that speed camera? :)
 

ernibv

Member
Joined
Jan 19, 2022
Messages
92
Location
Leiden
From the sound of it you just have the standard Barchetta idle control valve problem. Clean it or replace it. Plenty of info about that here on the site.
If you hit 6000 rpm in any gear the ECU will back off automatically.

4) car accelerates slowly at anything under 4,000 revs.... not sure if this is normal or not. Not normal. See above. Check your clutch.

Basically, it seems like if I floor the throttle in every gear ( Not a good idea. See above. Check your clutch.) I know peak power isn't developed until something like 6,000 revs but is it normal that a barchetta engine has to be flogged to the red line to get something close to responsive throttle performance? This is just not true ;) Check your clutch. See above.
grtz ER
 
Top