Explain using a vacume gauge to set optimum timing at idle. I heard someone mention this a few days ago.
Are you carbed or EFI ?LukeNukem said:Explain using a vacume gauge to set optimum timing at idle. I heard someone mention this a few days ago.
ChuckChuck said:Sixlitre, what are their total timing numbers (32* and 52* with vacuum advance) based on? Ideal total timing numbers tend to vary greatly between different engines, and different combustion chamber shapes will have a huge effect. Base timing of 6* is also pretty dang low ...
Anyways, any idea where they're getting their numbers, and what engine that's on?
Chuck said:Nice, thick gumbo mud. :thumbup
I'm already pretty familiar with the benefits of getting the timing set as close to ideal as possible, and I definitely agree it makes a bigger difference than just about anything else you can do. I was just curious where those numbers were coming from and what you recommended for testing and setting cruise timing. Curving the mechanical advance for full throttle is pretty easy if you're willing to spend a little dyno time, but finding the best vacuum advance curve under part throttle cruise for economy takes more than a little more work, so whenever I find someone with good info on the subject, I always hit 'em up for whatever I can find out. :rockon
How are you measuring for best cruise advance? Are you looking for the total advance that yields highest vacuum at cruise conditions, and then setting the vacuum advance canister to yield that advance at that vacuum? (Sounds circular, but I'm sure you know what I mean -- sort of an iterative process to find a setting that will give you highest possible cruise vacuum.) In other words, when you say one Mopar liked 57 degrees total timing at cruise, what are you watching to determine that it's running better on 57 than 55?
Right now I'm running TFI, so no vacuum canister for me, but I'm hoping to switch the truck over to Megasquirt sometime over the next year -- which would give me full control of all timing parameters. :thumbup
Wow !Chuck said:Okay, that's what I actually thought you were probably doing, tune for knock and then back off a few degrees. Cool. :thumbup
Actually, the reason your factory EFI 5.0L does so well is the knock sensor. I believe they used one in 86 too, my reference doesn't go back past about 88. :cry Anyways, it does exactly the same thing -- the computer's timing table is set just far enough up to cause knock, and it uses the sensor to retard the timing and hold it just below the threshold.
To heck with MAF conversion, go Megasquirt! If you're used to doing your own tuning, you'll do much better with a fully tunable system, and it's cheaper than a MAF swap as near as I can see. Don't get me wrong, I love the MAF system on my Stang, but when you swap you'll also lose your knock sensor. I know the MS guys are working on incorporating knock sensing now, and they may have it already, I don't remember. Besides, a properly tuned MAP based controller is honestly better than MAF in most cases ... and it'll certainly be better later when you get tired of your plain jane 393 and want to go turbo/supercharger. :histerica As far as I know, the only reason the factories went over to MAF was the fact that it would automatically compensate for incompetent maintenance, or the complete lack of any maintenance. There are no power advantages, and MAF actually costs you top end power because of the extra intake restriction.
Megasquirt can be found here. It's essentially an open source system, and is about 1/10 to 1/5 the cost of most aftermarket systems with the same capabilities. I also strongly recommend their forum, tons and tons of information there, the link is on the left. I've been watching the forum for a year or two to learn and I haven't even set up MS on anything yet. :toothless
I was actually going by the 88+ Probst book, which was why I didn't have the info on your 86. Lots of good, quality info in Probst's stuff. Eventually I'll have to pick up the edition you have, but the only pre-91 stuff I have around right now is carbureted (for now, at least). :toothlessSixlitre said:Wow !
Megasquirter, on the surface, looks like a viable alternative to Tweecer or MAF, like you say !
My favourite EFI reference is this;
I figured I'd better grab the 80-87 book before the later book superceded it and it became extinct.
I would assume he does, but I don't know offhand. There are a number of vendors running side (or in some cases primary) businesses assembling MS boards for people -- might be something he'd want to look into, since he's got plenty of electronics experience. Actually, there are probably a few things regarding MS that he might find a market in, and I'm all for Bronco guys who help the community so much being able to make a good living. :twotu:Sixlitre said:Thanks for the tip, and remember that vacuum arm will always deliver ALL it's advertised degrees. All we're doing by adjusting it is to slow down or speed up when it delivers the degrees. If you need less degrees you need a lessor cannister.
Thanks for the tip on megasquirt, does Fireguy know about these guys ?