Deceleration timing values-Skoda 120L Estelle

autoreplica · Post by **autoreplica** » Tue Dec 09, 2014 7:42 pm

I read somewere that vacuum pressure under deceleration=throttle complete closed is around 0.2atm=20kPa (manifold vacuum). So, with distributor, on loads smaller than 20kPa, under deceleration, distributor vacuum correction is 0deg (ported vacuum), centrifugal=mechanical correction is like in distributor mechanical correction map + static advance.
Then the rows 10 kPa; 20kPa loads in MJ ignition map are identical with 102kPa row ?
Are these rows "deceleration rows" ?
In most maps posted here these rows values was with maximum advance=static+centrifugal+vacuumatic.

Observation: Fuel drawn under deceleration is only via idle jet which is 50%-70% smaler than main jet who rulz WOT. But in this situation is very little amount of air drawn = very rich AFR condition. The engine are revved by car's inertia (engine braking).
These ignition settings avoid exhaust popping under deceleration ?

Here is this kind of Skoda 120L Estelle map. Not tested yet due to harsh weather conditions

Alex B · Post by **Alex B** » Wed Dec 10, 2014 8:14 pm

I don't know where you looked but in de MJ default map there is a difference between the 10-20KPa maps and 102KPa. It is clever to increase advance at such low revs with increasing KPa, the engine picks up easier when you start to open the throttle. Check my second Saab Sonett map to see what I mean. It reduces a possible short stutter when you are at low revs and start to accelerate; it did in my case anyway.

Alex

autoreplica · Post by **autoreplica** » Thu Dec 11, 2014 5:19 am

Alex B wrote:I don't know where you looked but in de MJ default map there is a difference between the 10-20KPa maps and 102KPa. It is clever to increase advance at such low revs with increasing KPa, the engine picks up easier when you start to open the throttle. Check my second Saab Sonett map to see what I mean. It reduces a possible short stutter when you are at low revs and start to accelerate; it did in my case anyway.

Alex

In this map, all RPM, load and advance values are deducted from distributor's centrifugal and vacuum correction diagrams posted here : http://www.autosportlabs.org/viewtopic. ... 7871#17871

Can you post your distributor correction diagrams, please ?

Alex B · Post by **Alex B** » Thu Dec 11, 2014 10:30 pm

Don't know exactly what you mean with correction diagrams, but here is the link to the maps I use on the Sonett.
http://www.autosportlabs.org/viewtopic.php?t=3799

Looking at your maps i don't think it is a good idea to set advance so low at high vacuum. Mixture is lean so you need extra advance.

Alex

autoreplica · Post by **autoreplica** » Fri Dec 12, 2014 5:00 am

Alex B wrote:Don't know exactly what you mean with correction diagrams, but here is the link to the maps I use on the Sonett.
http://www.autosportlabs.org/viewtopic.php?t=3799

Looking at your maps i don't think it is a good idea to set advance so low at high vacuum. Mixture is lean so you need extra advance.

Alex

Here, page 66 : http://www.vintagesaabmanuals.org/uploa ... 150dpi.pdf

As from model 1971 , "maximum maximorum" advance is: 6deg.(static)+26deg.(centrifugal=2x13deg.)+12deg.(vacuum=2x6deg.) = 44deg.
This occur when RPM is higher than 4500RPMcrank(2x2300RPMdistr.) and vacuum is higher than 0.5bar.vac. = -0.5bar.atm=50kPa.
At WOT vacuum is near 0bar.vac.(no vacuum)=1bar.atm (atmosferic pressure)=102kPa , so maximum advance is : 6deg.(static)+26deg.(centrifugal=2x13deg.)= 32deg. for RPM higher than 4500RPM like in your map.
But vacuum regulator start to action from around 0.2bar.vac.=0.8bar.atm=80kPa.
Is your vacuum regulator a special differential type with both manifold and ported pick-ups ? Vacuum correction diagram have "negative" correction curve for deceleration purposes?
On deceleration manifold vacuum is very high, ported vacuum is near zero and total advance will be: 6deg.(static)+26deg.(centrifugal=2x13deg.)-6deg.(Vac.)=26deg. for RPM higher than 4500RPM and full closed throttle.

Sorry, it's late, must go to job !

Off-topic: I have idle problems with my WEBER 32/36DGAV !!!

Alex B · Post by **Alex B** » Fri Dec 12, 2014 4:27 pm

My Adobe Reader is obsolete and for some unknown reason I can't download an upgraded version so I can't open the file, but I think I know which graphs you mean. The vacuum regulator your describe was for the US market only, mine is bog standard with only one vacuum line, so only normal advance and no retard. The US version was used in order to meet exhaust gas regulations. Doesn't make an engine run better I read.

Off topic: what is your idling problem? I have 2 engines with DGV's (manual choke) so I am quite familiar with the type. Do you have the idle settings procedure?

Alex

autoreplica · Post by **autoreplica** » Sun Dec 14, 2014 6:52 am

Off topic: what is your idling problem? I have 2 engines with DGV's (manual choke) so I am quite familiar with the type. Do you have the idle settings procedure?

Alex[/quote]

Can you sugest to move this to another forum about Webers ?
It is OK to discuss this here ? I agree, it's interesting for many, i.e. datalog analysis, but boooring for others....
Brent, it's OK ?

Alex B · Post by **Alex B** » Fri Dec 19, 2014 8:04 pm

PM sent.

Alex