detect engine knock

[DutchEdwin]

Now, my car is running, only question remains, what is the best timing.

To early will result in blowing holes in the pistons, to late will give bad mileage.

So our worst enemy is the engine knock. But how to detect?

I ran over an article that states that most engines from 1995 have a knock sensor. But can you use this device on our old engines.

I did a little google and ran into two articles,

http://www.mez.co.uk/turbo7.html (go to the section Knock Detection Part 1 and 2.

And referring to an article in autospeed magazine http://autospeed.com.au/cms/article.html?&A=0353 on how to build a cheap electronic stethoscope from a hard-hearing device.

Has anyone done this before?

enjoy.

[Plymouthy Adams]

the knock sensor detect the pinging by sonic wave and is directly connected to the on board engine controller which will retard timing electronically till the engine no longer knocks..this is why you can run these engines recommend for higher octane on the lower grade fuel..the computer will compensate..albeit at a loss of performance..so..unless your engine has controller that provides for this feature I do not know how you could take advantage of this feature

[greg g]

use the vacuum gauge connected to the intake manifold to attain the highest steady reading at idle. If necessary adjust the idle speed as needed. then drive the car, If you have a moderat hill in your area, run the car up the car in high gear and try to accelerate up the hill. Any sparck knock (or pinging as we call it) will be audible. If you ca hear it pull over and retard the timing a bit and try again, retarding a bit each time till you can nolonger hear the knock. You will probably end up at about 6 to 10 degrees BTDC if your fuel is anything like what we have over here. The factory spec is 4 BTDC.

[martybose]

use the vacuum gauge connected to the intake manifold to attain the highest steady reading at idle. If necessary adjust the idle speed as needed. then drive the car, If you have a moderat hill in your area, run the car up the car in high gear and try to accelerate up the hill. Any sparck knock (or pinging as we call it) will be audible. If you ca hear it pull over and retard the timing a bit and try again, retarding a bit each time till you can nolonger hear the knock. You will probably end up at about 6 to 10 degrees BTDC if your fuel is anything like what we have over here. The factory spec is 4 BTDC.

A good analysis of timing a stock engine. But if you've raised the compression, or added carburation, or headers, or a cam, or (like myself) all of the above, you might find that even with 91 octane gas you wind up back at 4 degrees BTDC!

But the process is right; I have a favorite hill that I used for setting my timing.

Marty

[Cpt.Fred]

do you use the vaccum port from the manifold, were the wipers are connected to, or the one on the base of the carb, were the vac advance of the distributor is controlled with?

what would be a normal reading on the gauge?

i still have not fully understood how this is related, vac and timing...

[james curl]

Yes, you use the port where the wipers connect. If you get a long hose that will reach inside and install the vacuum gauge on it then you can go out and drive at 50 and then 60 and see what the vacuum reads at a steady speed. You might find that your vacuum advance is still in the picture on total advance at those speeds. The manual gives the amount of vacuum advance for different advance readings. You would want to take that into consideration when setting the initial static advance. The timing is considered to be at its optimum setting at the highest vacuum reading at idle speed.

[Cpt.Fred]

thank you! that's good to know, i'll test it later today...

[greg g]

The vacuum reading gives a very good indication of the condition of the engine and how it runs. At idle the engine produces the most vacuum at the maifold, setting timing for the highest reading produces the most efficient combustion process.

[greg g]

Here is a good primer on the use and interpretation of vacuum gauge and thier readings

http://www.secondchancegarage.com/public/186.cfm

[DutchEdwin]

Greg,

I did all you stated, except....I live in a flat country. All the hill I have available is a river dike, 10 meters high. I did retard timing until I got the max vacuum. The reading of timing went way off scale on the crank shaft. It must have been like 15-20 degrees. But the vacuum reading was 22 inch. I run the car now at 6 degrees because the engine had the best stable rpm at 450 rpm. I know it is not ideal yet. should probably more like 10 degree. but still the vacuum is then about 19-20 inch.

There is something I did wrong or not set right.

When the car has ran for 10 miles it will not start or very hard start after 3 minutes

My next step is to change all electric, coil etc.

To set the ignition at best my idea was to have an electronic stethoscope to hear the knock before you can hear it in the interior. That way you are safe and have the engine run best.

The article is about building one your own. Was hoping someone did this before. If not, I'll be the first.

[greg g]

Opps I forgo most of the hills in the Neatherlands had really damp areas on the down hill side. You can also check by runing on a level stretch and in high gear try wide open throttle acceleration from about 15/20 mph if its going to knock it should under that load. You can make it more effective by adding weight to the car, 3 freinds, tool boxes, several cases of beer, bags of tulip bulps, etc.

[DutchEdwin]

Got it, and then down hill to 12 m below sea level

Keep you posted when I have the stethoscope ready.