Rep Power: 312

http://www.forparts.com/fi.htm

http://www.asashop.org/autoinc/may2001/fuel.htm

http://www.waynesgarage.com/docs/mileage.htm

http://pages.prodigy.net/jforgione/MB_SFI.html

http://216.239.41.104/search?q=cache...hl=en&ie=UTF-8

http://216.239.41.104/search?q=cache...hl=en&ie=UTF-8


But I guess I'm just an idiot, huh andyman? I could post more, but I really don't think I need to.....Point proven.

 
Rep Power: 312

Oh wait - here more!

http://216.239.41.104/search?q=cache...hl=en&ie=UTF-8



and another!

http://www.autoshop101.com/forms/h43.pdf

Oh my!

I guess the guys at autoshop101 can understand things - maybe you should take a class in autoshop....that might help!

 
Rep Power: 413

I wrote up a long reply to this, but I scratched it in the hope that we can attempt to get this back on topic (since I was one the people to push it off topic )... We believe one thing, you believe another... Some exmples provided back up your opinion, while others back mine...


No big deal, let's just agree to disagree and keep giving us some more good info from your datalogger....

 
Rep Power: 328

ok, now you have completely LOST me. understand that its been a few years and all since ive wrenched for a living. but are you trying to say that at 50mph you take your foot off the clutch and gas and turn the car off its going to F up the engine because its in gear? Could you please clarify ?

 
Rep Power: 328

From what i can gather , granted its not like i was ever a fuel system god. But i do have a good grasp on how a cpu controled fuel system works. I would have to agree with opto for the most part from what ive read. Now im not for certain as to if it completley shuts off fuel on decel with zero throttle or not. But it does make sense to me, and i can understand how it would work. Now im not taking sides here, but i think there could be a missunderstanding between the two different arguments here. I guess from my view on the decel with zero throttle it would put the car into an engine braking status and would require very little if NO fuel at all. I have smoke coming from my ears now, my brain dont work like it used to

 
Rep Power: 350

Man, I wasn't attacking you, you don't need to attack me just because we don't see eye to eye. You could at least show a little maturity here, I'm trying my best, you should, too.

Anyways, I checked and read every single link you posted. You aren't making a valid point by posting links. It's a discussion and by you saying that the injectors completely shut off is absurd. I don't know what's so hard to understand. I've given reasons and examples of why what I have said is correct but you're not explaining yourself. Posting links for GM fuel systems and fuel system evolution throughout the decades doesn't prove your point. I want to know why you believe (and how it's possible) for the injectors to shut off during deceleration at an rpm above 850 (as you posted earlier). That's it. Just explain.

 
Rep Power: 350

I think you're correct, in part. All I'm doing is breaking down what the Helm's quote says. It says that for deceleration above 850 rpms, the ecu cuts current (as in electrical current) to the injectors. Therefore, it's not pulsing the injectors the same as it would if you were accelerating. It pulses as it would if the car was idling. All I am saying is that your crank will not continue to rotate if there is no fuel being injected into the cylinders every stroke.

And for the scenario I was talking about earlier with shutting off the engine while doing 50 in 4th gear, what I'm saying is that your crank is rotating at a certain rpm when you're doing 50 mph in 4th gear. If you go from 2XXX rpm and shut off fuel supply and ignition spark as well as air into the tb, there will be no more combustion in the cylinders, right? If that's the case, the pistons will not continue to fire and there will be no more force causing the crank to rotate.

Now look at it realistically. If the crank is rotating then suddenly there is no more force on it, it's going to want to continue to rotate (Newton's law of inertia.) But there is nothing going into the cylinders and they aren't continuing to fire so the crank is no longer being moved by anything other than intertia, it still is moving 4 pistons and rods. There is no longer going to be any oil pressure and the cylinder walls will not be lubricated after that and it will seize your engine.

 
Rep Power: 350

I didn't see any that did. Did I miss something?

 
Rep Power: 312

I am an engineer. I see things in a conceptual light. I read technical documents on a daily basis. What the Helm manual wrote, as well as the most excellent link I posted about from autoshop101, explain everything about how it works in great detail. There really isn't anything else too it. The engine continues to run because the cars in motion. Its not going to suddenly stop just because fuel is cut off. We're talking about how many pounds of steel moving at 5000 or so RPMs? That is a LOT of inertia - and don't forget about our favorite little guy, the flywheel - which stores mechanical energy......There is much more to the engine stopping than just taking fuel away.....

 
Rep Power: 350

But without fuel your engine will die. I had my fuel line pop off of my rail while I was decelerating before and my **** started bogging bit time. If I hadn't realized what was going on and pushed in the clutch quick enough, it would have torn my motor up. But the engine didn't continue to run. It was dying right there without fuel.

 
Rep Power: 328

I think its a missunderstanding between you 2 one is thinking in gear (manual trans) car turns off yes the car will decelerate and the engine will continue to have RPM's untill the car comes to a stop. Will it stop crankshaft rotation imediately? NO not until the car comes to a stop cause its in gear. But on the other hand if its an automatic trans or is in nuetral yes the engine will stop rotation, imediately? NO not untill its released all of its energy that is built up in the crankshaft and rods and pistons and such. In either case the crankshaft is still turning for either a second or 2 or 10 seconds depending on what situtation and the engine will continue to pump oil during this time cause the crank is still turning and in turn the oil pump is still turning untill no more crakshaft rotation. Now onto the fuel electrical question. When the key is turned off there will be NO more spark, and no more fuel entering the combustion chamber other then the residual fuel and last coil discharge on the spark plug. As to the question about fuel and spark shut off during deceleration with zero throttle i think this needs more investigation. I for one can see how its possible. But cant fully understand the transistion from none to back into throttle without hick-ups. Guess i should refresh some knowledge and do some reading

 
Rep Power: 312

Ok - after rereading what I wrote, I was wrong here. MY car was attempting to maintain a -10 LTFT. Theorhetically the LTFT should be at 0 if everything in your car is perfect (in a perfect world). The ECU was attempting to correct for a higher than "normal" amount of fuel per injection cycle by injecting less fuel. If the value would have been positive, than it would have been attempting to inject more fuel to compensate for a lean condition. After logging more data it seems my engine may be running a wee bit rich, which accounts for the fuel correction from the STFT and LTFT......

For some reason I can't get the MAP pressure to log properly. It monitors fine, but does not seem to log. I've emailed the company, hopefully its just a glitch they will fix.

BTW, there are other software packages that will work with the digimoto box, because it is a "universal" device made by elmscan. Here is a link which provides other software for it as well:

http://www.scantool.net/software.htm

I have yet to try them out - they look pretty cool as well...