Spittybug #2329 Peugeot 604 manifold custom conversion

[Spittybug]

Hello,
Set the distributor via vacuum guage (advance slowly) at idle: expect about 18". At 2000-2500 RPM the vacuum guage should read 24-25". Byrne

I'm not really understanding that Byrne. Manifold vacuum is at its greatest when the car is at idle (but we block it from advancing the dizzy). The mechanics of the unit inside the distributor control how much it can advance the plate, and our book says 20* is the max, when the vacuum is greater than 15" of Hg "pull". As the throttle is opened, manifold vacuum drops as a result of being exposed to atmosphere (inches of "pull" goes down), so I guess I'm confused as to why you say the vacuum gauge would show more vacuum?

Maybe the difference is in manifold vacuum and throttle body port vacuum? With air rushing faster past the holes in the throttle body it would increase the venturi effect and lower the pressure for sure. The manifold vacuum isn't subject to that same effect because of the larger volume and slower movement of air.

In a stock Delorean the vacuum hose to the distributor comes from the thermal vacuum control valve and the vacuum source for that valve is the manifold itself, not the throttle body, right?

Or perhaps you were suggesting setting the static timing via vacuum gauge reading rather than timing light? Sorry, I'm confused as to your point.

[Spittybug]

Using an Excel file I found that some MG owner had put together, I modified it to our stock specifications. It is pretty neat to visualize and see mathematically how it all comes together. Allows for "what-if" on getting the mechanical advance in quicker too. I guess we can't upload Excel files, so here is a PDF picture.

I'm going on the presumption that a lot of work went into developing the stock parameters (amount of advance and the specific springs used in the distributor) and they are therefore as good a starting point as possible.

I'm going to burn this to my ECU and see how it runs. The X and Y axes are configured so that I have a lot of detail down in the areas where the engine spends most of its time. It's ok that the table isn't linear as Megasquirt algorithms are calculating the appropriate values on the fly, not actually picking numbers off the table. The table is to establish the points from which to extrapolate the actual values.

[jangell]

I guess we can't upload Excel files, so here is a PDF picture

Can you zip it and upload the zip? Just curious if that would work. That does look like a pretty cool visualization of the map.

-- Joe

[Byrne H&A]

Measure the vacuum at idle and slowly advance the distrubtor to maximum vacuum while idling. If the distribitor is advanceed too far the vacuum will drop. At peak it may be 18 plus and if higher that is better. Tighten the hold down distributor nut and increase the RPM, the guage will advance to 23" or more at 2000-2500 RPM. Byrne

[Spittybug]

Can you zip it and upload the zip? Just curious if that would work. That does look like a pretty cool visualization of the map.

-- Joe

Let's try that..... you may have to change the .zip to .7z for it to work... I use a program called 7-zip for zipping. Dunno.

[Bitsyncmaster]

I just checked my vacuum. At 850 RPM idle I get 17.5". Between 2000 to 3000 RPM I get 19.5". When I punch it it drops to 5" or under depending on how fast I punch it. When I quickly let off the gas it can climb up to 25" also how fast I let off.

[Farrar]

Dave, off topic for this thread I know but it looks to me like you may have a small vacuum leak. When my engine is idling at 900 RPM I have 20-21"Hg reading.

Farrar

[opethmike]

As I am planning on going with ignition control sometime over this winter, I am keeping a very close eye on this thread.

I've already decided that the winter project for 2012-2013 will be cams/heads/exhaust. I'm 100% convinced that those will benefit greatly from the full MS control, and will make for a very productive dyno tuning session. Better than stage II, here I come! (....in a year....)

[Spittybug]

I burned and tested today with a little modification from what I last posted. I removed vacuum advance from the high RPM, low load area of the table. In the stock setup, with the foot off the gas (deceleration) the micro switch would engage, cutting off vacuum advance, duh. Not shown on this table I also bumped the 40 MAP, 700 and 900 RPM bins to 17 or so to help reduce the oscillation at idle. Helps a bit, but the bigger culprit is difference in VE table. Notice I increased the rate of getting the mechanical advance all in. Now comes in between 1000 and 3000 RPM. After these changes I tooled around with VE autotuner running and things improved even more. Basically dropped some of the higher VE values I had and made for less "jitter" when letting the clutch out.

The test drive felt good and strong. Better acceleration, no signs of pre-detonation. When cold, the idle hunts just a bit just like stock, but not once warmed up.

C'mon you other EFI guys, together we can nail this down tight! Take the plunge!

[opethmike]

I'm planning on taking mine to the dyno in the spring so I can get the ignition tuned properly. I'll be sure to put in information at that point.