Don Terrill’s Speed-Talk

Newold1 wrote: ↑Mon Dec 10, 2018 5:44 pm David:

What would be the cost of this spark plug substitute pressure sensor be and the related equipment and devices to read the measurements and record them? Sounds expensive.

I have assembled the components necessary to build an Engine Pressure Kit for use with a data logger.

The cost of the kit would come in at $675 and would include:
High Pressure Sensor (0-300 psi)
Low Pressure Sensor (0-100 psi)
Spark plug adapter (any size or style)
Exhaust pipe adapter (with thermal insulator)
Inlet air temp sensor
All necessary wiring and bungs

The kit could be used to measure and collect induction pressures (including turbo boost pressure), compression cylinder pressure, exhaust pressure (including turbo back pressure) and inlet air temperature, in a running engine.

A low cost, high speed data logger (approx $1200) would be provided with necessary software and harness. System can be used on carbureted engines or most ECU equipped engines via CAN. Detailed documentation for installation and data analysis is included.

If anyone is interested in more information and availability, please send me a PM. I am reluctant to use this forum for advertising or product promotion but would engage in any technical discussions.

You would probably have to write code to smooth the data as well to make it legible.

You also need to, ideally, sync with crank position.

hoffman900 wrote: ↑Tue Dec 11, 2018 2:50 pm You would probably have to write code to smooth the data as well to make it legible.

You also need to, ideally, sync with crank position.

Actually not. There are other ways to get the job done.

David Redszus wrote: ↑Wed Dec 12, 2018 10:24 am

hoffman900 wrote: ↑Tue Dec 11, 2018 2:50 pm You would probably have to write code to smooth the data as well to make it legible.

You also need to, ideally, sync with crank position.

Actually not. There are other ways to get the job done.

Not to which part??

The smoothing program could be written in another of programs. I know this is something that people I’ve talked to do that use this kind of equipment mention.

hoffman900 wrote: ↑Wed Dec 12, 2018 10:28 am

David Redszus wrote: ↑Wed Dec 12, 2018 10:24 am

hoffman900 wrote: ↑Tue Dec 11, 2018 2:50 pm You would probably have to write code to smooth the data as well to make it legible.

You also need to, ideally, sync with crank position.

Actually not. There are other ways to get the job done.

Not to which part??

The smoothing program could be written in another of programs. I know this is something that people I’ve talked to do that use this kind of equipment mention.

Smoothing is undesirable since it eliminates useful information. I never use smoothing if i can avoid it and I usually can.

David Redszus wrote: ↑Wed Dec 12, 2018 10:31 am

hoffman900 wrote: ↑Wed Dec 12, 2018 10:28 am

David Redszus wrote: ↑Wed Dec 12, 2018 10:24 am

Actually not. There are other ways to get the job done.

Not to which part??

The smoothing program could be written in another of programs. I know this is something that people I’ve talked to do that use this kind of equipment mention.

Smoothing is undesirable since it eliminates useful information. I never use smoothing if i can avoid it and I usually can.

Do you have an example of what a raw output looks like on a firing engine?

hoffman900 wrote: ↑Wed Dec 12, 2018 2:15 pm

David Redszus wrote: ↑Wed Dec 12, 2018 10:31 am

hoffman900 wrote: ↑Wed Dec 12, 2018 10:28 am

Not to which part??

The smoothing program could be written in another of programs. I know this is something that people I’ve talked to do that use this kind of equipment mention.

Smoothing is undesirable since it eliminates useful information. I never use smoothing if i can avoid it and I usually can.

Do you have an example of what a raw output looks like on a firing engine?

Yes, I have dozens of data sets, mostly from turbo exhaust applications, and a number for two stroke crankcases.
With a sampling rate of 1000Hz, the raw time series looks like mere hash.

Unfortunately, I don't have a good way to post graphics.

At work we use Optrands PSI plug setup and AutoPSI-TC. Together I think they are about $1300. A cheap 4 channel oscilloscope can be had for a bit over $400. Our beater scope is a Instek and works well, but is less user friendly than costlier Keysights and such.

The nice thing with a setup like this is you can look at cylinder pressure on a running engine, tag into a crank or cam position senor, see when ignition fires, etc. Really helps understand whats going on inside.

David; if the pressure data is presented like a graph, pressure VS time, crank degrees or whatever- could you do a screen shot and post the pic?

Most likely, the most interesting part would be a larger range of RPM or boost, but to give an idea of the output a small glimpse would be helpful?