would you buy a rotary comp tester?
 

just as the title states, discuss. Keep in mind Mazda comp wnts $1400 for theirs.

For $1400 no way. Guy had some for sale a while back for like $800. I considered it for a while but still too steep. Ten manybe 20 years down the road when I have every other tool I could ever want and if hydrogen rocket cars haven't replaced the rotary I may think about buying one.

Funny you should ask...I'm working with an EE to develop a build-it-yourself (ala Megasquirt) datalogging board and software to plot the output of a common 0-5v pressure transducer on a Palm handheld. The prototype board is done and I'm waiting on him to finish cleaning up the signal from the CAS, which is the last remaining hurdle. No idea on price yet, but it will be inexpensive (other than the pressure transducer, but maybe we can get a group buy going to minimize cost). I should be testing it in a month or so, then releasing the plans shortly thereafter.

Were you thinking of doing something similar?

BTW, if anyone has an OEM rotary compression checker and wants to sell it, let me know. I'd like to do a head-to-head comparrison.

http://www.japanicity.com/~mak/


-Ted

I bought a new-in-box graphing style one for 300 bucks and have been very happy with it. This was a few years back and I don't remember exactly where I got it.

You guys are missing the simple answer. Not to mention cheap.

Pressure transducer + cheap datalogger + old laptop =

Ok, what is a guy looking at for a good reliable pressure tranducer? And how does a guy know what to look for in one? I've found them on the net from $85-850.

This is an extremely good idea....especially if you already have two of the three, or at least something comparable. Thanks for the tip.

I'm using a Setra 209. A pretty damn good unit for the price from my laymans perspective. Get a buddy at a shop to order it for you and it's only a single Franklin. http://www.setra.com/tra/new/new_fc_209.htm

As far as configuration goes, you want it compatible with your datalogger's ranges. I'm actually using a 9V battery for excitation voltage.

I got a Mazda Comp checker off ebay.... I forget how much it was somewhere around 500 i think. Its pretty expensive but its been very helpful in tracking engine info... not only of my many motors, but my fellow racers as well.

The laptop idea seems more cost effective though.

So did you make up an adapter to fit the spark plug hole? What thread are those anyways? (brains not working anymore) Also what pressure range do you use? I'm thinking at least 200 psi but may go as high as 500 psi so that I can use the transducer in othere applications. ie brake force logging.

My question is the datalogger. I've got the transducer and laptop ends covered but my geek friends say I need to convert the analog signal of the transducer to digital for the laptop. I've already figured I can use a Haltech's datalogging capability to make it work but would like a more portable solution. Where to find the elusive datalogger?

Never mind. Google works surprisingly well when you tell it what to look for. I'm all over it! Thanks for the idea!!!!

14 x 1.25, I found all my stuff in this giant box of fittings my Dad has. Then I put an air chuck coupler in there so the wiring harness doesn't have to be twisted around. Great minds think alike. I too opted for the 500psi ceiling thinking about who knows what I might want to measure down the road.

Rotary compresin tester
 

[QUOTE=HeffBoost]You guys are missing the simple answer. Not to mention cheap.

Pressure transducer + cheap datalogger + old laptop =[/QUOTE

Great Idea Heffboost,
I run a Rotay shop, And I have 2 of the old Analog ones with the paper readout.
It is the only way to go if You are serious about building and testing rotaries.
A regular single cylinder comp. press. gauge, will not give an accurate reading nor show differences between chanber to chamber, It WILL however give a FALSE higher reading because it adds up all 3 chambers continuoslly,as long as You keep spinning the starter.
Your idea is excellent, and along the correct application lines of diagnosing to see if You have say 1 good, and 2 bad chambers in one rotor.
A paper graf readout, can tell You if youu have rotor Housing damage or not prior to dis-assemble.
Regards,

GT1-20b

Thanks, but I'm sure I'm not the first to either come up with the idea or to apply it.

Yes, I now too think it's the only way to go.

For $24.95 you can order the DataQ "starter kit." It logs 4 channels of +/- 10 V, has serial output and software.. Even an ActiveX control for custom software.

I'm still looking for an appropriate transducer. I have a 0-100psi one now but want a 0-150 psi unit. I just refuse to pay $100 for a simple 0-5v transducer.

http://www.dataq.com/products/software/acquisition.htm

Good luck. I personally think it's not too bad. I would love to know of a decent one that's cheaper.

The transducer I just ordered was $200, but it's super high-quality. I did find some transducers in the $70-90 range in quantity, however, so I will probably set up a group buy when my compression checker project is ready for prime time.

The setup we are working on is a general purpose datalogging board that can be used for just about anything (accelerometer, remote tach, etc). The compression checker is an add-on board and is quite sophisticated. In fact, it can identify and record the peak readings with no help from a laptop or Palm computer. In a future revision, we may add a small display so you can view the peak readings too. Another mode allows you to dump raw sensor readings out to a computer or Palm via serial cable, so you can graph the pressure/time function (like a sine wave).

The datalogging board is ~$50 fully assembled and tested and the compression checker add-on board will be in the neighborhood of $30, assembled and tested. I believe we will also be posting the schematics and parts list, so the geek-inclined can make their own for even less.

https://www.rx7club.com/forum/attach...id=95471&stc=1
https://www.rx7club.com/forum/attach...id=95472&stc=1

The software supplied will be for a Palm but if anyone wants to hack something for a PC, you're welcome to it. I like the Palm because they are dirt cheap (under $50 on eBay for a good one) and highly portable.

I'll probably get one, later down the road

I know, I know.. in the scheme of things it's probably not too bad. Most of the transducers I seem to find with specs are industrial grade units.. way more precise, durable, expensive that this needs to be. If I had a decent tool to log resistance rather than 0-5v I'd think about using a simple $12 oil pressure sender. I remember hearing about an AC pressure switch out of a Lincoln or Caddy that was an actual transducer and not just a switch.. and spit out 0-5v. That would be perfect and I'd bet it would be cheap as hell too. I can't seem to find it though.

Blake, I like your project. Where do I get on a list? Will any of the chips need to be programmed to get it running or will you offer it a-la Megasquirt.. kit of parts + preprogrammed ICs?

If you need windows software I'll offer to write you some..

Not starting a list...yet. I have to test it on a real rotary engine first. :) The EE is sending me the production datalogging board and the prototype compression checker board next week and I will take it to Pineapple Racing for a shakedown. Don't know the specifics of how it will be offered, except that we will have inexpensive assembled and tested units in addition to whatever else. Stay tuned for details. More eye candy:

https://www.rx7club.com/forum/attach...id=95520&stc=1

Count me in!

:-) neil

Take a standard compression tester and remove the Schrader valve. Watch the needle react on all three compression cycles of each rotor. You can easily spot a bad apex seal.
Will it log for you? NO!!
Is it cheap? YES!!
I do like the idea of the logger though.

Cbuzz

My answer is yes. If its reasonably priced and a complete unit or kit. Im there. I prefer it be configured for a PC so I can use it on the laptop.