Engine diagnostic software? Computer tool for old cars? - PeachParts Mercedes-Benz Forum

JeffreyNMemphis · #1 04-18-2009, 03:34 PM

Hello Friends,

I have an extra laptop that runs Microsoft XP. It is just sitting in a box with no job or purpose. I was thinking that it could be a dedicated tool for car stuff. Is there some old software that is cheap or freeware that I can run on this computer that will tell me the engine timing, vacuum, Air/fuel ratio, what is going on with the ECU at different settings?

My engine is the 1973 M117 engine. Laptops were a distant dream when this car was built.

There must be something. If there isn't, maybe there should be? As much as we love technology and old cars, there is definitely a market.

Thanks in advance for your thoughts...

Jeffrey

Arthur Dalton · #2 04-18-2009, 04:05 PM

Your car is pre closed loop...............

JeffreyNMemphis · #3 04-18-2009, 04:13 PM

Arthur,

I am an old nuts and bolts guy hobby mechanic with no formal training. I don't know enough about engine management electronics to know what closed or open loop means. Can you tell me more or point to somewhere I can read about it? I am totally willing to learn and do the footwork in my quest for information; I just need a clue or some direction to head in.

Arthur Dalton · #4 04-18-2009, 04:29 PM

Nutz and Bolts kinda guy....

Ok ...this is Basics only.
Closed loop refers to Engine fuel management control by the use of an 02 sensor in the exhaust pipe...this sensor tells a computer if the engine is running rich or lean...and the ECU respondes to that signal and adjust the fuel mixture in the opposite direction to try and get it to Stoic [ 14.7 to 1 a/f] --- [ lambda]
If the 02 reports "Rich" , the ECU leans , and v/vesa.......So , once an ECU sees a cycling 02 signal, it is said to be in 'Closed Loop' , where all controls of fuel mixture are in reference to the 02 signal being fed to the Engine Management System...a very efficient way for the engine to get the biggest bang for the buck.
Google has ton of info using lambda or 02 sensor ......

http://en.wikipedia.org/wiki/Air-fuel_ratio

You car is a point ignition system and has no 02 , so it has little info to report back to a laptop.
The tools for those were dwell meters /exhaust analysers/and timing lights....

JeffreyNMemphis · #5 04-18-2009, 05:13 PM

Good answer... Thank you.

I considered getting an Innovate wide band 02 kit for my Porsche. At the time, I was doing research for Turbo conversion and decided that path was going to be expensive.

The fuel management system using an 02 sensor is what provides a laptop with data for interpretation? Or does it just provide data for AFR meter.

I have some other questions... That I will say out loud here and then search with Google for an answer. I have watched shows on television about car tuning that show laptops with information that help tune the car. If someone has experience or knowledge that is helpful like Arthur, I appreciate it.

For early fuel injection systems like MFI, CIS, D-jet (like my car), is there any benefit to knowing A/F ratio? dwell, timing or other? Is there any other information beside AFR that would be helpful to know about the motor for tuning optimum performance?

Is there any benefit to be gained on cars with carburetors to know A/F ratio? Would it help tune carbs?

Is there any kit like the Innovate system that comes with sensors that is designed for pre-closed loop cars? My 1973 didn't even have a tachometer. Just the basic temperature, oil pressure and gas gauge.

There is an adjustable screw on my ECU, but I don't have any way to measure the effect if I change it, so I have not touched it.

Gurunutkins · #6 04-18-2009, 08:14 PM

Hi Jeffrey

I have a megasquirt system on my car so use a laptop to monitor the temp, revs, injector pulse etc etc but without going to a stand alone system I dont think you can do too much to monitor the system.

I installed 2 O2 sensors in my car, one to control closed loop operation of the megasquirt and one in the other exhaust going directly to a stand alone afr meter mounted in my dash. whilst running, the afr meter is actually a very good indicator of how well you are running and is about 10 seconds behind what the engine is actually doing. so if I acclerate about 10 secs after pushing the pedal I see the mixture bars climb into the rich area and then when I ease off they drop right down into the lean section etc and at cruise 2700rpm on a flat road it just sits slightly short of the middle of the range.

quite fun to watch and is very helpfull for telling you to ease off the throttle etc.

cheers
Barri

GaryF · #7 04-19-2009, 04:16 AM

Quote:

Originally Posted by JeffreyNMemphis

For early fuel injection systems like MFI, CIS, D-jet (like my car), is there any benefit to knowing A/F ratio? dwell, timing or other? Is there any other information beside AFR that would be helpful to know about the motor for tuning optimum performance?

Is there any benefit to be gained on cars with carburetors to know A/F ratio? Would it help tune carbs?

Is there any kit like the Innovate system that comes with sensors that is designed for pre-closed loop cars? My 1973 didn't even have a tachometer. Just the basic temperature, oil pressure and gas gauge.

There is an adjustable screw on my ECU, but I don't have any way to measure the effect if I change it, so I have not touched it.

As Arthur said, an exhaust analyser, timing and dwell meter tells you everything there is to know. The open loop old style fuel injection systems are effectively pre-programmed to map the fuel requirements to pre-defined situations. Unlike modern FI systems they don't monitor the effects of that mapping and can't adapt to events such as vacum leaks or worn engines. So even if you did montor everything with a PC there's little you can do to change the situation. That's where megasquirt comes in.

Tachometers were an optional extra in '73 and take their input from the ignition points so this in itself doesnt reflect a lack of capability.

The screw on the ECU controls the idle mixture only and again an exhaust gas analyser is required if you want to set it precicely, if you fit an O2 sensor an A to D converter and a bit of software on your laptop you've basically just built an exhaust gas analyser the hard way.