Just to let you all know, I\'ll soon have a compression tester suitab;e for the rotary engine up and running. It\'ll be working through my laptop computer using PC based oscilloscope software, analogue to digital converter and a gas pressure sensor from SensorTechnik.
This should be all go by beginning of Feb (got some holiday coming up before though).
Thought this might be useful for anyone in the southeast to know.
Pete
that sounds like an interesting device, will it log the RPM as well ?
edit> I suppose that will be a function of the wave length
Sounds a bit like the Comp 7s.
sounds a hell of a lot cheaper :D
Plot will be pressure against time on each rotor so rpm will come from that.
I phoned up Mazda in Southampton and they seem to do it all wrong by compression testing on the RX7 with a normal gauge. The tester they have just got in for the RX8s has cost £15,000!
Now my little idea is costing about £150 + my time and some DIY fabricating of a few bits.
I\'ve bought 2 pressure sensors - one is a 0-250psi one and the other is 0-150psi. I need to connect these via 2.5mm or so tubing to the dissected threaded plug of a standard compression tester. I\'m guessing the highest pressue I\'d see on a rotary is about 130psi but I have a reason for wanting to use ones that I can calibrate to a much higher level. What often happens is that the region of linearity often tales off in the upper half of a sensor\'s range and optimum calibration is usually easier to achieve in the lower portion.
Each of the pressure sensors give an output of 0.5v to 4.5v and the relationship between pressure and voltage is almost perfectly linear. So for example, an output of 2.0v would equate to 125psi on the 0-250psi sensor, and 63psi on the 0-125psi sensor.
The analogue to digital convertor takes this analogue voltage and converts it to an 8 bit digital measurement that is used as the input data for the PC based oscilloscope.
The software for the PC based oscilloscope is fantastic and allows really easy calibration of the sensor. At university I\'ve done loads of instrument calibration and this is no different to calibrating my atomic absorption spectrometer!
My PhD in Environmental Science has got to be submitted by Monday so I guess that\'s why I\'m busying myself with other stuff - to somehow justify not getting it all done!
Go the mad Professor! :D
Great stuff Pete, I use Labview and a little visual basic to run my D/A convertors at uni. My rigs nearly finished now, so lets just hope my programming skills don\'t let the side down:rolleyes: ;)
Let us know how you get on and good luck with submitting; that day seems so far away from me now with my rig only just being ready to calibrate:eek:
Paul:D
interesting you saying about the compression tester for the RX8, as Mazda in Poole have no idea if they are even going to get one let alone when... £15000??!!! I hope it comes with a free RX8 attached to it.
Next up, a nifty little printer with a graph of the results with smiley faces and sad faces, then people can put it in with all the other crap they collect owning a car these days.
Maybe even jazz it up a little... Our survey says... REBUILD!
(http://www.ukgameshows.com/atoz/programmes/f/family_fortunes/bygraves_duhduhh.jpg)
Nice one Matt :rollin Can\'t beat the Bob Monkhouse Family Fortunes though.
I\'m pleased to say I\'ve now got everything except the pressure sensor up and running. The software is excellent. It\'s a doddle to view (and also print out) the graph of the compression peaks so you get an instant visual indication of how closely matched the chambers of each rotor are without having to look at numbers. Click of a button to change the graph y axis from psi to kpa or whatever you want.
Pressure sensor should be with me in the next few days.
Already thinking of an upgrade and that will be to a mult-channel analogue to digital converter (ADC) so that I can plug in as many rotors or cylinders as I want in one go!
get yourself a signal converter to read the RPM signal from the ECU and you\'ve got yourself the ultimat boost controller mapping tool, a sensor for throtle would be useful as well... food for thought:D
I\'m already working on another little project that I need to look for someone with some programming experience to help me with. I\'ve got a Wizards of Nos nitrous kit that I\'m going to be whacking on my Skyline. Didn\'t want to fork out £300+ for a progressive controller so I\'m thinking of using a programmable solenoid controller (programmed via RS232 and has various analogue and digital inputs and has pulse width modulated outputs to control solenoids and so on). I\'m thinking that if I have inputs for RPM, turbo boost, and all the other bits then it might make a pretty safe and customisable nitrous controller, and boost controller if I stick in a knock sensor!
I would definately rig up a lambda sensor if your running gas through it, compensation could be made based on the reading of the lambda sensor???