The base timing is just that, the advance is in the ECM as you suggest, programmed by numerous tables. Some folks think you just turn the distributor to get the advance you need. The advance should be programmed in the chip, and there is a LOT of places to tune. Moving the distributor makes global changes. A motor might need more or less advance at any given load vs RPM.

There are benefits to manually advancing the distributor to a larger bias than stock on an electronic distributor, such as to decrease the distance between the rotor an the terminal for applications where the total advance might achieve the limitation of 45 degrees BTDC.

-- Joe

 

Actually, on old carb applications without electronic distributors you had both centrifigul and vac advance, both of which was adjusted with kits.

With the first generation electronic distributors, the advance was built into the module and could not be altered. I'm guessing this is what started the ignorant trend of globally moving the distributor.

With newer systems (late 70s, early 80s CC carb) the advance is done in the chip based on engine load, RPM.

I fail to see your issue with that. Maybe it's because you don't understand how ECM's work, and have never tuned one. I've used '747/'746 and even '730 ECM's to just control timing in a lot of carb applications, especially boats. It also can be used to continue controlling the torque converter, fans, etc. But you didn't know that did you.

-- Joe

 

Correct. You are making my point for me. So why the emphasis on "ELECTRONIC FUEL INJECTION SYSTEM" distributors? Whether the advance curve is electronic, programmed into the computer or chip, or it is controlled by weights, springs, and a diaphragm from within the distributor, rotating the distributor has the same exact effect.



You fail to see a lot. You WISH you knew what I know. The ECM CAN be left in place to control several things. I don't need for YOU to point that out to me. But just because you were able to cobble something together, doesn't make it right. Like Kobbledvette's MAFless tune. The timing needs for a boat are quite different than for a DD car. A race car can work well with centrifugal advance only, or even a locked out advance mechanism for off road use where smoothness, drive ability and economy are of little concern. I have yet to read, in one of these EFI to carb conversions where the TPS, MAF, and/or MAP were retained. Retaining the ECM and the electronic distributor in such a conversion would be like a mechanical distributor operating without a vacuum advance mechanism. NOW, can you see the issue.

Just because you "fail to see" something that is clearly evident to many, is no excuse to poison the minds of the young and impressionable people that simply want to learn about their cars. Statements like "The more spark you can run, the more power you can make. It's pretty simple really.", and "I wouldn't have removed the computer, it can still control the timing. serve no purpose in a place where people are seeking serious help and advice on their projects.

RACE ON!!!

 

You missed the point entirely. No surprise, I'm getting used to it.

The point was: Moving the distributor GLOBALLY changes it. If you are moding a computer controlled ignition, you should be making changes in the bin. There are a lot of other tables that effect timing as well.

I'm pretty comfortable where I am, thank you.

I wasn't pointing it out to you, the other thread had nothing to do with you. But why did you bring it up?

cobble is like duct taping your bumper on, or like advancing the distributor or raising the fuel pressure and calling that tuning. What I do is modify code until it can't run any better. If you don't understand how to do it it's fine, but don't try to knock on me.

Thats not me. thats him.


This is coming from a guy who doesn't modify advance tables but just turns the distributor.. wow.

You don't have a clue as usual.

The advance table is based on load vs rpm. Obviously a MAP (or maf) signal would be required, much as it existed (MAP) on the older CC carb applications.

In regards to the other thread with the carb swap, he was doing it on a '90+ car which does not have a VSS buffer in the dash. His 4000PPM VSS is wired directly into the ECM. My statement about keeping the ECM was because unlike you, I know what I'm talking about.


I like how you try and turn this around. You are pretty good at that.
The fact remains YOU do not understand what I'm talking about so you choose to try and discredit me with your typical nonsense. If you can't tune an ECM fine. If you don't understand how the code works well that is fine too.

First quote is proven science. You yourself have stated how you advance the timing until the car won't go any faster at the track, so please give it up. My statement was in direct relation to coolant temps. You seem to think a car is perfectly fine at 220-240. I explained that the cooler you can keep the water, the more advance you can get away with without detonation, and generally speaking the more advance you can get away with the more power the combination will make.

The second statement. You just simply have no clue what you are talking about. Perhaps a few of the other guys with '90+ cars can chime in and explain to your simple mind why they left the ECM in place to keep the CCM and speedo/odo happy. Not to mention it will have absolutely ZERO idea that the injectors, IAC, and TPS are not there anymore and the advance tables will work as they always had.

I don't know why you feel so threatened by me.

-- Joe