anyone ever try in cylinder pressure sensing ?

[Yves]

Wonder if anyone has ever tried to fab up a diy system.

Most systems I see are very expensive (in the order of + $10.000). Looks like this could be done with a pressure sensor mounted to a spark plug and a data acquisition board like NI has them.

[subwoofer]

This has been discussed at length, and is very attractive indeed. The only "little" problem is getting hold of a pressure sensor that will work. Closest to an off-the-shelf solution is the Delphi sensor apparently used by Daimler (Mercedes-Benz), but that requires modifications to the head to install.

http://www.msextra.com/forums/viewtopic ... 25&t=55863

[JAM]

Definitely something that would be fun to play with, but as noted the cost at this point seems to be a bit distracting. This is one i was looking at

http://www.tfxengine.com/index.html

[Yves]

I think there are sensors that are mounted on a regular spark plug. Do these have issues then ?

Yes, the TFX unit seems nice, but at $5000 for a system with 1 sensor, is very expensive to say the least.

Other option would be with an ionsensing device, however have not seen those in stand alone form.

[Speedy_G]

spark plugs with cylinder pressure sensor integrated are very expensive. Around 3000€ for one.
And this is just the start. The other stuff you need is even more expensive. For professional use for example Kistler KiBox ~70000€


Another possibility is to use a ion sensing system. Its cheaper and easier to adapt to an engine.
You can use the signal to locate the peak pressure position. Its a good thing for ignition application. There is a typical range where you get the most torque.
with cylinder pressure indication you use the combustion centre of gravity. (50% of heat curve). This point is a bit earlier than the ppp.

and you can also use the signal for knock detection.


ion sensing is used in a lot of newer cars. For example in some BMW's.
And i think SAAB is using it for a long time.
Delphi is one of the supplier for those systems.
They already used it at the Harley V-Rod. This was in 2002.
The engine was developed or let's say improved by Porsche.

[racingmini_mtl]

Ion sensing is NOT used to determine ppp in OEM applications; it is only used to detect knock and engine phase. Determining ppp from ion sensing is very limited in range (load and RPM) so it is not something that can be used for any practical application at least with the current technology.

Jean

[Yves]

I thought that the spark plug sensors were something like $ 1000

[Speedy_G]

Ion sensing is NOT used to determine ppp in OEM applications; it is only used to detect knock and engine phase. Determining ppp from ion sensing is very limited in range (load and RPM) so it is not something that can be used for any practical application at least with the current technology.

Jean

As far as i can say, its only a problem at low rpm and low load. There you got the problem that its hard to locate/extract the maximum in the thermal ionisiation. It varies too much / no clear or good signal.
So it shouldn't be a big problem for our purpose here.

and yes currently ion sensing is not used in oem applications for cylinder pressure engine managment, but there is a lot of research going on there.


Do you have practical experience with ion sensing?

[Yves]

I have gotten a quote for the TFX engineering system, but wow US$ 5.000,00 for just one sensor. The sensor alone costs € 1500.

Now I'm willing to see how far I could take this. I can get my hands on a good NI 6259 daq that could be used and I'm willing to search for an instrumented spark plug. If the testing succeeds, I might be able to have someone make a pcb that could do this on a regular basis and export its data to MS, which might be something that could benefit a lot of tuners here. But I'm not good a programming labview. Anyone here has any experience.

[crash914]

I actually did this years ago, in the mid '80's for my senior college project.

At the time, all we had was IBA AT computers. I used as I remember, a "Data Translation" analog input board and a piezo pressure transducer that was attached to a spark plug. I did not buy the spark plug so don't know who made it.

The plug was a stock one that was modified with a little pipe welded to the top side to a hole drilled into the chamber next to the electrode. the transducer then screwed to the top of the pipe. It was pretty small as I remember. If I had more brain cells left, I might remember where we got the plug. I seem to remember that the analog board was around $2k and the spark plug was $500. I would look for a piezo transducer company that will then custom fab the spark plug for you...shouldn't be too much money. It is a lot easier now than then. herb

[Yves]

I can get a NI 6259 DAQ with usb for 300 $, but the spark plug is around 1500 if the quote from TFX is correct.

[crash914]

All I remember is that the spark plug was modified by the people that made the transducer. I don't believe that the cost was over $600.00 I just can't remember who made the transducer...good luck!

[crash914]

Here is one, don't know the cost though.
http://www.optrand.com/fliers/calplug_060201.pdf