In cylinder pressure measurement

[Mark Wilcutts]

This has been done in a labratory environment for at least 50 years. The
main manufacturers are Kistler (www.kistler.com) and AVL List
(www.avl.co.at). For mounting, either a modified spark plug or cylinder
head flush mounting. The sensors are $500-$1500 and require a charge
amplifier ($1000). They suffer from drift and thermal shock but are
otherwise excellent for combustion analysis. Gross things like misfire and
knock are easily noticeable.

Recently, in our lab we have been using an optical transducer
(www.optrand.com) that measures the deflection of a flush-mounted diphragm
remotely with a tiny laser through an optical fiber. These currently cost
about $900 and don't need a charge amp. Future indications are that the
sensor electronics can be miniturized and the sensor produced at very low
cost.

One problem is, how to collect all that cylinder pressure data and then
what to do with it once you have it? We use a DSP data acquisition card
($$$) clocked by a crankshaft mounted optical encoder at 1 CAD increments.
We are using the data to back out actual rate of burning and thus get some
measure of the quality of combustion, our emphasis being on combustion
during cold start. 

-- 
Mark Wilcutts
Mechanical Engineering Department	University of California

On Wed, 12 May 1999, C. Brooks wrote:

> Has anyone ever heard of anybody doing this? I was talking with someone
> about data acquisition systems and the subject came up while we were
> discussing methods of knock detection. I'm not to enthusiastic about being
> able to monitor A/F ratios accurately or in realtime, and our conversation
> kinda stuck with me.
> 
> If anyone's ever seen or heard about somebody performing in cylinder
> pressure measurements I'd love to hear about it. I imagine the transducers
> would have to be pretty tough, how would they mount? What kind of sample
> rate do you think would be needed? Best of all, who would make a sensor that
> could take the abuse???
> 
> 
> 
> Charles Brooks