DIY Delta sensor

I decided to make delta sensors before attempting to build an absolute pressure type sensor.

Very cheap to make. I haven’t finished putting it together because I’m waiting for banana connectors.

The capture I posted is just me trying to figure out the orientation.

Here’s the complete product. I should’ve bought different banana connectors. But, I had these already.

Will update with some captures once the adhesive sets in.

Here is a couple captures. Gonna have to do another capture as I had throttle plate open.

Here is the intake done during a crank but with the throttle closed.

Looks like it's working. Were these traces taken on an engine with some kind of mechanical issue? There's some suspicious looking variation between cylinders.

One other thing are these piezo traces DC or AC coupled? My 'scope only does DC so I'll build a cap into the sensor, when I build mine, if AC coupling is required.

Nice. Looks sensitive enough for the cars I work on.

Are any of those captures on known bad cars? Maybe pull a spark plug on one and see what the waveform does.

Matt, I used DC, I am experimenting as I have only used in cylinder transducers and if I’m being honest I don’t truly understand this. I’ve only used a FLS in a coolant tank which was easy to find the bad head gasket.
I have seen something about using AC coupling which I will try.

The biggest thing here for me is I don’t have a pressure transducer of my own even though I’m comfortable using one for diagnostics. This is a step to help me grow as I am really struggling with understanding these captures on the intake. I think I understand exhaust captures but either way, I will learn it eventually!

As far as the captures, there’s only one capture done the correct way and that is the one that pretty much only shows the green trace. When capturing intake, I’ve been advised to do it during a crank and with the throttle body closed.

They’re all the same car. It only has a secondary miss which during the cranking capture would in good have an affect. Or effect. Ehh I’m not an English major. I will pull a spark plug and post another capture when I can. I’ll also post exhaust captures both running and cranking.

These sensors an unbelievably cheap to make if you brake down the parts per unit. Most of it isn’t worth buying individually as the cost is around the same for buying in multiples.

Hi John,

I attached a document that might be helpful in understanding intake pressure waveforms. And there is a link to another document that exceeds the 5Mb upload limit. It's on the same subject. Ask any questions you may have, if I know the answer I'll contest.


1drv.ms/b/s!AilHGEYrlbUTa9QXRlRAZu9Bhj4?e=LnwEGK

Reading over the material here in a minute. Thanks Juergen.

Cranking exhaust capture with a mechanical fault.

Here’s one that had the parts cannon fired at it. Everything from plugs and wires, to coils and PCM.

It was suspected the new PCM was bad by the mechanic. It even passed a block test.

I couldn’t sync due to not long enough leads. I’ve been advised next time to pull a spark plug as a sync (Good idea).

This capture shows a little funk on two adjacent cylinders. Didn’t have an adapter that fit to hookup into the coolant tank on this one.

Now, two adjacent cylinders, first thought is head gasket. But these captures make me think the intake valves aren’t properly sealing and could be at fault circled in yellow).
Am I wrong?