EFI & Firing management setup

[Duvalof]

Hi Gents;

I know that in our forum we have good engineers and i am currently assembling a vintage BMW CSL Grp 5 with an M5 engine. I decided to go with a racing engine management ECU. This manage either the fuel and the firing.

My question today is how to proceed to setup the firing timing to avoid the knock. I was thinking to build a little electronic device which lights when knock is detected. For the fuel i will use a lambda sensor it should be easier. Any of you ever saw that somewhere ?

Any advice on how to proceed for an engine setup is welcome as i never did that before !
For memory i have no dyno to perform the program .... /ubbthreads/images/graemlins/bandito.gif

A pic of the car :

 

[Murray Cowley]

Wow, that looks mean. It's about twice as wide as a normal Beemer!! Have fun! /ubbthreads/images/graemlins/banana.gif

 

[Ron Earp]

Get a wide band O2 sensor from one of the gauge companies. Use them on our race cars to get the carb right. Also, Exhaust Gas Temperature probes are perfect too and we use them as well.

On knock, there are lots of OEM sensors that can be used and a few aftermarket devices to display the signal for you.

Ron

 

[Duvalof]

Ron,

I have the lambda and the ECU manage and display it on the computer
You mean that displays for knock detection exists such as airfuel ratio displays ?
Never saw that ... /ubbthreads/images/graemlins/confused.gif

Which A/F ratio do you use on your cars ? i was thiking for 0.97 (fuel rich)
The car will be used on tracks, i think you'd bet it ... /ubbthreads/images/graemlins/grin.gif

 

[Ron Earp]

Yep, there is one I know of as I've seen it in a buddies race car, that is, a knock display. Has a LED and displays knocks detected, has a "sensitivity" knob, and a red light that comes up as well. It may or may not do anything with the ignition, I'll have to find out.

R

 

[Ross Nicol]

Most engine management systems on cars these days use a piezo microphone element attatched to the block/head.This sensor detects knock/pinging caused by over advanced ignition timing or poor octane fuel.When knocking is detected the computer backs the timing back (retards)to protect the motor from damage.If your cars management does not have this feature, as Ron suggests an after market unit
that flashes a light on the dash when knock occurs will probably save money on blown motors,if you really push the ignition advance to the edge.I doubt whether a unit like this could do anything but indicate that the motor is knocking.
Ross

 

[Duvalof]

Ron, Ross,

I have the 2 piezo sensors, the only thing i miss is the display. As you mentionned Ross, this is only way i found to setup correctly my engine near its maximum capacities (ie near the edge).It is not possible to detect knock with ears sometime so i prefer to secure it with a display. Those BMW engines are quiet sensitive and very expensive to repair so i don't need a blown piston !

I spoke with the engineers at work and they explained that knock should be detect true a "window" means you shouldn't make the detection on the total crank duration but only during the firing. The objective is to avoid detecting other noises (frequencies) at high revs, such as valvetrain noises. Ron, do you think those displays take this fact into account ?

 

[Ron Earp]

I'm sure they do with the sensitivity portion control. In fact, I remember reading an article about the problems with knock detection and you can ignore the data during firing, or, you can simply build a filter in the device to try and filter "non-knock" events. I think the first case of ignoring the data during firing would be best but that will be a more sophistcated device.

Ron

 

[Duvalof]

OK Ron, thanks, so now the thing i must do is to look into the network to find this device !

 

[Ron Earp]

Try some of these:

All in One
http://www.fastwrx.com/turboxstuner.html

Specific for models
http://www.jandssafeguard.com/safeguard.html

Generic
http://www.jandssafeguard.com/

 

[Duvalof]

Many thanks Ron ! ;o)

 

[Paul Thompson 'Hooligan']

HI Fred

Fuel ratios are a strange and complex subject. For the best setup, get the car on a dyno and set it correctly for max power throughout the rev range. For what it's worth, I would think 0.97 is a bit lean for max power still safe but I generally aim for 0.93 to 0.95 max as a starting point and then work from there.....

 

[Duvalof]

Paul, i'll keep your advice in mind, you seem to be aware of the subject with the Motec ...
I tried to obtain information from M (BMW sport dpt), a German friend of mine work there. I asked him if he could provide some fuel and firing maps, to my surprise his was not allowed to do this, even if the engine is no longer produced and now from 1997 ... Secrets remains secrets !