rotary compression tester
 

have any of the members bought one of these compression testers?
http://rotarydiagnostics.com/

they claim that the following people have bought a tester off of them:

SpeedSource, Inc., Atkins Rotary, Daryl Drummond Enterprises, Diasio Car Company, PF Supercars of MD, Banzai Racing, KDR Performance, Mazda Rotary Club of Switzerland, several Mazda dealerships, and numerous individuals in the US, Europe, Asia and Australia.


I just ordered one of the mulit rotor testing unit and would like any feedback that other members might have.

kenn

Looks cool.

I don't wan to shit on anyones parade but.....That looks like just a device that extrapolates the pressure store it on a eeprom and then you dump it with the software. Seems something like that could be made alot cheaper than what they charge. But if it works hey it works! Seems like just a newr version of the old school mazda one. would be nice to get inside that and see whats up in there!

yeah I thought so also but its still way cheaper than the alternatives for a premade unit. the only other units I have seen are from a source in Japan that makes the newer digital style onesfor Mazda , it does not log, so you can not store and later compare data or anything like that and its right at 850.00 and can only do one rotor at a time (not that its essential to do more) and even the old paper trace units used are going for between 4~500 used.

So I was like well as often as I have wished to have one and being that it costs right at 5000 yen (50.00 USD) to get a compression test at the local dealership (and I get a righteous discount)

with that in mind and considering how often I rebuild engines it would probably pay for itself in a couple of years,

just not sure f this particular company is straight or not......

I did a search in the good guy/bad guy forums and got no returns on them...:scratch:

I've got an old "MotoMeter" unit in my closet that was used for diesels. It records compression on a small card. I was going to convert it to rotary use by making an appropriate sparkplug hole adapter, but kinda lost interest in the project.

It's a nicely made old-fashioned German craftsmanship gadget and even comes in a fine wooden box.

The recording cards are available, and there are several in the box..

You might be able to hunt one up on eBay or maybe Craigslist.

If you were to drive by my house I'd sell it to you for $20, just to see how it works out. But I dunno about shipping to Japan.

it would almost be worth it to try, but AI jsut went ahead and ordered one of them. I ordered the multiple rotor unit thta can do up to 4 rotors (if you buy the extra transponders) adn will start with one transponder to see how it works, and will get back with ya all later about it.

Kenn

But to buy a new one from mazda with a discount is like 1300

Looks like a pretty good deal at $350 for the one-rotor at a time unit.

well i just got an email back from KDS and they were listed as one of the shops that had bought one, they gave it a two thumbs up with just the note to be careful about banging the sensor around as they damaged their sensor this way.

kenn

If you buy one and use it, be sure to report back here.

OK got my unit in today and will be setting it up and testing it after the 4th of july weekend. When I test it I will be going to The local mazda Dealership and testing ti side by side to see how accurate it is but I will need make a conversion chart so that I can compare kilograms to PSI.

On the unit itself, It looks Much better when it is front of you then it does in the pictures. I am not sure if Larry (rotarydiagnostics.com) is following the thread or not but if you are the photos on the website do not do the the unit justice.

The case is a nice solid case its about 2"x5"x8" with the adapters for the pressure transducers mounted on the outside, they are screwed into place vice being simply pressfitted or glued, (Nice touch I thought), so no worry about them coming loose, the pressure transducer itself has been mated to a brass quick disconect that then plugs onto the spark plug adapter. all in all a nicely assembled unit.

Well we shall see soon, We have a freshly assembled 13brew medium SP that was built from all new parts for a test mule and will be recording and documenting its entire break in. It currently has 200 kilometers on it of gentle break in and will will start upping the ante soon.

cheers

kenn

This is exactly what I was trying to build a few years back.

The thing that makes it expensive isn't the little black box or the software, it's the pressure transducer (yes that's the proper name for the sensors).

It doesn't dump it to a chip, you hook it to a laptop with the DataQ software installed and get the read-outs in realtime.

You can get the box and the software for $30 here, but the hard part is finding appropriate pressure transducers

http://www.dataq.com/products/startkit/di194rs.htm

I have one of those and the software, and had found a couple different transducers but I never finished the project because my at-the-time g/f and I broke up, I had to move out of the condo etc.. etc...

You need preferably a 0-200psi transducer that puts out a 0-10V waveform for that range. 0-100psi would give you more accuracy since the software reads the data in .2V increments but some engines might actually have compression >100psi so that wouldn't work. If you could find a 150psi unit that would be perfect.

I found all sorts of transducers in those ranges on ebay if you look for long enough, but the problem is the output. If you have one that changes amperage or resistance instead of voltage, you end up having to buy a $200 sensor box instead of the $30 one!

I found one more recently available for purchase here for $185:
http://www.gaugestore.com/prodinfo.asp?number=34298

So if you consider that their system uses two of those, that's $400 to replicate the kit yourself. Though you really only need one so $215 for a DIY rotary compression tester.


Back then I was hoping that someone would take it the step further and find a way to make a circuit that can interpret the 0-10V waveform and output the compression for each chamber on little LED read-outs like the official Mazda one does. This one will just display the graph on the computer and it's up to you to interpret it. So what you get on your screen is the same kind of thing you'd have gotten from the OLD mazda rotary tester that had ticker tape and looked like a seismograph.

Either way, for taking the effort out of assembling a system like this, I give these guys props and there's no reason to think it wouldn't work as advertised. The price is reasonable (once you look at what transducers cost!) and if I wasn't so broke I'd probably buy one.

Jon

...I still like the old skool standard comp. tester with the valve removed so you get each pulse. Hasn't failed in 18 years of driving rotaries. I can tell if the shit is blown or not , damnit! $1300.....sheeeeeeit!

I've found a regular compression tester with the valve taped down, recorded on my video camera for frame-by-frame playback, does the job for me... but this definitely works more easily.

Thought about making something like this a couple years ago, but got lazy. Hehe.

Y'know, Vipernicus, I bet one of those pressure transducers, coupled to my digital storage scope, would work just dandy, too.

results of tester, long post.
 

OK heres the skinny on it. hooked it up to the car over the weekend, and followed all directions, got it all loaded into the computer and then started recording, the first time around I made one mistake, you need to completely shut the computer off after loading, and then restart the computer or it will not record (at least mine did not) after that initial restart all is well, and the unit worked as advertised, the first one tested was my track toy which is the following, 1st gen with S-5 transplant, IHI RHC-7 (62-1) with 40K kms. on a rebuilt motor thats mostly track use :)

I got 129-128-128 front rotor and then 124-123-123 on the rear.

I thought thats a bit higher than I was expecting and then i decided to use the unit to measure the cranking RPM as was explained in the destruction manual. and it worked out that my engine was cranking over at 303 RPM vice the required 250 ish. Looked at S-5 Mazda FSM and according to its compression cranking RPM comparison chart it seems that I should subtract about 12 PSI as a correction for the difference in RPM

This would then give me 117-116-116 front and 112-111-111 rear for a difference of 7 or 8 PSI from front to rear.

any body got any input on this? in the past when I used the dealerships tester, they gave me readings that were normailized to 250 rpm.

next test will be my friends FD; its literally a brand new engine with all new housings , rotors, journal with a mild streetport and all of the supporting mods. It has about 300 Kilometers on it since it was built and is still in breakin period. I plan on testing it this week and then retesting it each 200 Kms or so so that I can get a baseline graph and some experience with the tester itself.

I am curious as to how fast the compression comes up and if we can use this as a baseline to determine when the engine is in fact finishing breaking in ?

Being that this car is basically a private effort track car that occasionally sees some weekend cruising it should be interesting to track its compression from breakin period to its next rebuild cycle maybe a year or so from now.

End result is that the unit works, works well and is relatively east to use, as long as you remember to restart the computer after loading the programs. The seller communicates well, and he ships quickly, don't think I could have asked for much better service from Him.

kenn

God, I love science!

The tester may tell when the apex seals/housings are fully broken in and the engine has reached max compression. It won't tell when the bearings are fully broken in. New bearings can take as long/longer than apex seals to break in.

Good to hear a positive report on this unit. It's a much less expensive option than the Mazda one and could generate some strong sales.

You have 40k on your track car already? Sounds like you've been having a good, and serious time with it.

Off topic, have you had any luck finding the 5 bolt SSR centers I need yet? I'm getting close to the point where I can order the Moser axles, the centers are the only thing holding me up on that.

What are the minimum specs for a laptop that the software can be used with?

Scott,

Good to hear from you again, I had a set that i was bidding on a few months back but had no luck on them, i will have to watch yahoo again.

40 K kilometers is only 25,000 miles, you have to remember I drive the car to the track and back, and the good tracks like Ebisu are a 5 hour drive with me driving spiritedly :naughty:

Honestly ebisu is like about 650 kilometers away so it adds up quick.

Kenn

Ken, next time a pair comes up for bid, PM me and we'll see what we can work out. I still have that pair of 5 bolt centers that don't fit. They will need to be sold or they will become wall ornaments.

Good write-up Kenn! And thanks for the postive feedback. I just came across this post after reading your post in another thread.

I have not run across the restart-after-install situation you ran into, but as I'm sure you know, it's always best to do a restart after installing software. There is one thing you should look out for, though. If you unplug the USB cable before shutting down the program, the program will likely freeze the computer. Not a big deal, but it usually requires a reboot.

As to the question Rotor13b had about the minimum computer specs, the WinDAQ programs that ship with the system will run on any PC, laptop or desktop, running Windows 2000, XP, or Vista. Processor speed and/or the amount of RAM in any computer running those operating systems should be adequate for the programs. The computer can be located up to 16 feet from the tester without providing auxilliary power by adding an optional 10 foot extension USB cable. Longer distances would require a powered USB hub. Also, one customer reports running the system on an Mac using the Windows emulation software, Paralells.

Larry