Vacuum figure when idling

Edwardatherton · Post by **Edwardatherton** » Fri Aug 31, 2007 2:24 pm

Now that I have a long serial lead I can plug the Land Rover into the computer outside the office window... !

When idling the vacuum is in the high-30's range. Is this normal? Min/max when standing still is 14-110.

Does this runtime graph look right for an idling engine? The MAP is 'jittery' as well as the revs. How stable should I be aiming to achieve?

Thanks!

Gilesy998 · Post by **Gilesy998** » Sun Sep 02, 2007 6:05 am

I've had this concern, as I could only describe the vac measurement as "rattling" up and down erratically. I asked the question on my club forum, with some interesting answers - http://www.minifinity.com/index.php?nam ... ic&t=49660

I've now added two connection possibilities to a spare manifold I had, but have yet to fit it to the car -

rbalmford · Post by **rbalmford** » Sun Sep 02, 2007 7:30 am

I can't answer your question directly as I run TPS. One observation however: I have no experieence of Land Rover engines, but your idle advance seems very 'low', especially as with a MAP sensor, it allows you to increase the advance at low load (high vacuum/low pressure) relative to that at high load (low vacuum/atmospheric pressure). What is you low rpm/high load advance in your ignition map? Maybe post a screenshot of the numeric ignition map showing the cell being used at idle.
Rich.

fikus01 · Post by **fikus01** » Sun Sep 02, 2007 9:14 am

if you have taken your vacuum supply from the same place that rover put the take off for a vac advance dizzy, chances are you arent getting vacuum! with the su carbs (im assuming you have) the vac takeoff is often partially shrouded by the butterfly and it gets airflow past it which means u wont get a true vacuum reading! if u havent already, try getting the vac takeoff from the manifold its self and as centrally as possible!

Post by **brentp** » Sun Sep 02, 2007 6:42 pm

I have to say, your RPM looks pretty solid. However, I'm used to a turbocharged 1.6L with 550cc running very rich at idle- it's a little bouncy.

Your pulsing map is causing your advance to change, which is probably causing your RPMs to hunt up and down a bit. Smoothing out that vacuum source will help.

Do you have a brake booster line you could tap into? Often those see equal vacuum across all cylinders. My friend's TR6 was configured this way and it provided good results.

Edwardatherton · Post by **Edwardatherton** » Mon Sep 03, 2007 8:24 am

The vacuum advance take-off is coming from the brake servo line on the manifold (which I don't use for anything else).
The carb is a twin-choke Weber.

I will try and find a plastic fuel filter thing today and see if that smooths the vacuum.

As for advance figures, I was playing about with the map on Friday at work (boss was away for the day!), so I need to find my initial workings which I left at home and see what I had in the previous map before I changed things...! The idel was better on that map.

Thanks for the replies so far, I'll update on progress soon...

Edwardatherton · Post by **Edwardatherton** » Wed Sep 05, 2007 8:33 am

When I got to work this morning I hooked up to the computer while it was still hot (the engine, not the computer). This is the runtime when hot - much more stable! One of the tappets is ticking, so I'll check them this weekend.

Edwardatherton · Post by **Edwardatherton** » Wed Sep 05, 2007 9:00 am

and here is the map I'm using...