The 'E' Type Forum

I hope this is the right place to post my question, but maybe it should be posted at "UPGRADEs". I got a 123/TUNE programmable distributor and been learning about ignition timing curves. So far so good, but many questions. The 123/TUNE distributor includes a vacuum nipple so a MAP curve can be also programmed... but my car has Weber DCOE45's, so I have no vacuum! For the moment, Ill try to block-plug the distributor nipple and juts program the advance curve. Anyone can help me understand if by going vacuum-less I should compensate the advance curve is any way?

I live in Mexico City which is 2400m ASL (7,804ft), What you, wise guys, recommend that I should consider regarding advance, total timing and static timing?

Rodrigo

PS: If anyone interested, I found some valuable information: http://rockridgefarm.com/vettdoc/Timing_101.pdf ...

Why not tap into the manifold and connect there? You can even buy the original suction pipe #C21576 and elbow #C21573 from SNGB for about $20. Once you have that working you can use the Megajolt maps as the basis of your tuning but ideally it needs to be done on a rolling road. It will take longer to get the Webers right though!

Heuer wrote:Why not tap into the manifold and connect there? You can even buy the original suction pipe #C21576 and elbow #C21573 from SNGB for about $20. Once you have that working you can use the Megajolt maps as the basis of your tuning but ideally it needs to be done on a rolling road. It will take longer to get the Webers right though!

Thank you David, I've researched about this and the following comment, from the question I post at 123, resumes what everybody seems to agree with:

You can't tap into the manifold as you will only get a vacuum pulse from one cylinder unless you have a balance tube manifold. Mine isn't so it can't be done. The post throttle plate vacuum on a 45 will throw it into a state of confusion

I'll look into the parts you recommend.

About the Megajolts maps, should I consider 100%, 50% or which curve? since mine is 2D. I think to compensate the lack of O2 at my alttitude I should consider more advance at static and at total timing, correct?

Rodrigo

Rodrigo

The standard vacuum pipe comes off one of the SU bodies and that does not appear to cause a problem with the 123. Alternatively you could use the method we use for Megajolt - tee off the Reservac vacuum hose:


I assume you are not using this Weber manifold which does have a vacuum port?:


More here: http://www.mangoletsimanifolds.com/mani ... -etype.pdf

Heuer wrote:Rodrigo

The standard vacuum pipe comes off one of the SU bodies and that does not appear to cause a problem with the 123. Alternatively you could use the method we use for Megajolt - tee off the Reservac vacuum hose:

David, Rodrigo is using Webers and therefore a different manifold. There are ways of hooking-up all six inlet tracts to power a servo, but the undamped fluctuations of manifold vacuum from a single choke would not work as a vac-advance source.

Theoretically, it is *possible* to arrange ported vacuum with Webers, but since the whole point of Webers is performance and the whole point of vac advance is economy, there is a practical and philosophical mismatch of the 'have or eat' cake variety...

Pete

I ran my car for years with just the mechanical advance without any problems other than poor fuel economy and as Pete says that is clearly not a concern if you fit 45DCOE Webers! After I fitted EDIS/Megajolt with vacuum advance my fuel consumption went from 14-18 mpg to 18-20mpg. Interestingly it improved still further with the cable throttle system as we averaged 22mpg on our latest jaunt through France.

Thank you guys, I do understand I'll be sacrificing economy... And I'll keep on searching about a way to get vacuum.

But if you read my first post, the question is: Considering that I'll go vacuum-less, should I compensate the timing curve in any way? .... And recommendations for high altitude in regards to timing (static & total).

Access to a rolling dyno is not available for a couple of months. I will just use a timing curve as a base and try to tune while driving.

Altitude should not affect timing in any way. What is does do, of course, is affect mixture strength considerably, and the thing to beware of is if your carbs are setup for your present altitude . If that is substantially in excess of 1000metres / 3000 feet , say 1500 metres /5000 feet and upwards and your carbs are optimised for that altitude, then if you descend towards sea level your mixture will become progressively weaker and if you use high performance at low altitude there is a risk of detonation , piston/valve burning etc