Technical 1.1 SPI MAP sensor - does it have a vacuum damper?

[Tom126]

Hello,

I'm troubleshooting a stutter under very heavy acceleration in 2nd/3rd on my 126 with a 1.1 SPI conversion.

There's a length of vac tube between the throttle body and the MAP sensor. On my install there's a black and white cylinder with 'CARB' on one end and 'DIST' on the other which makes me think its repurposed(?).

This tube was quite wet with what smelled like fuel and what looked like yellow liquid, I guess old fuel.

For peace of mind I have ordered a new MAP sensor, it may well be 20 years old now.

Should there be a restrictor/damper between the throttle body and the MAP sensor?

Thanks

 

[dac69er]

Alot of cars have a filter between them, but as standard the cinquecento sporting does Not, it is just a straight section of pipe.

 

[Tom126]

Thanks a lot - I will remove and see how I get on. It certainly does act as a restrictor. Do you know why I would have a build up of fuel in there? Is there something in the throttle body that normally stops this?

Thank you

 

[dac69er]

The vacuum take off for the map sensor on the cinq is a little stub on the inlet manifold. If you are coming off the throttle body, that may not really be suitable and could contain fuel residue.

 

[Tom126]

Thanks for that. Due to the engine 'bay' (it's like a shoe box) the throttle body has a dome filter straight on the top of it with a ~50mm tall adapter between the tb and filter. I wonder if I could tap in to the adapter or would you imagine that the vac would be too low there? I may end up having to make a longer air intake and tap in to that.

Thank you, you've really helped.

 

[Tom126]

Thinking out loud but if I get some hard (steel) 6 mmOD/5 ID and form it so the end sits level with the injector that should give a strong vac 'signal', comparable to the throat of the TB... More to follow.

 

[dac69er]

Thinking out loud but if I get some hard (steel) 6 mmOD/5 ID and form it so the end sits level with the injector that should give a strong vac 'signal', comparable to the throat of the TB... More to follow.

you need to take the vacuum source after the throttle butterfly

 

[Tom126]

Ah! When you said inlet manifold I imagined the ducting between the air box and the TB. So if my inlet manifold between the TB and the head is correct to the engine it should have a takeoff? I will look. Thank you, you saved me a big headache.

 

[dac69er]

Ah! When you said inlet manifold I imagined the ducting between the air box and the TB. So if my inlet manifold between the TB and the head is correct to the engine it should have a takeoff? I will look. Thank you, you saved me a big headache.

correct. there is a takeoff that goes to the brake master cylinder servo and also the map sensor.
yours may be slightly different if its in a different car, but i wouldnt have thought so.

 

[Tom126]

correct. there is a takeoff that goes to the brake master cylinder servo and also the map sensor.
yours may be slightly different if its in a different car, but i wouldnt have thought so.

Upon further inspection my manifold has a bolt where the takeoff usually is. Case closed!

Time to get the lathe set up.

Thanks ever so much for your help. May explain a few things.

 

[Tom126]

Oops

 

[Tom126]

Hello,

Thanks again, just machined up the adapter using the bolt that was plugging it and reset the ECU. Throttle response is a little better to say the least. I was wondering what I was missing...

Hope for better weather tomorrow for a proper drive.

Thanks ��

 

[dac69er]

Great. Glad it's sorted.

Where is your brake servo vac pipe connected too? Or is it old enough not to even have a servo assisted brake?

 

[Tom126]

There's no servo on this - considering it