TwistedRotors

Well I haven't checked it against a Mazda unit, but the transducer I'm using comes calibrated and also has it's own built in temperature compensation. I may try testing against a Mazda unit if I get a chance, but the results may vary slightly as I'm unsure how their unit calculates compression. My tester uses a simple math equation to calculate the pressure based on the voltage that the transducer puts out.
-John

Razz1

And at what RPM?

.

swoope

iTrader: (5)

john,

at that price you will do very well. the only thing i would add is if you could find a way to get the spark plug hole connection a bit more rx8 friendly!

as it has a quick connect to the reader you should have some options.

beers

gregs

iTrader: (7)

i have the mazda tester but i would still be interested in this option being that it is portable

Jedi54

iTrader: (7)

this thing looks awesome, nice job.

P.S. don't mention prices on here unless you're a vendor. Just say it's very well priced otherwise the owners or admins might lock your thread. I'm sure if people wanna know, they can send you a PM.

olddragger

iTrader: (3)

yep ---you will need comparision data between this unit and the mazda tester. I can see people running to their dealers with a "low compression finding" only to have that disputed after they test the car. That would not be good.
Love this idea/and product if it is accuate--and it should be. Just have to validate. Bonify it!
I cartainly can see many car clubs buying one.
OD

RK

iTrader: (1)

I'd definitely be interested. May take up a club collection and test out all the 8's in my region.

TwistedRotors

Thanks for the tip Jedi, I went ahead and removed the proposed price from my first post as the intention of this thread is really just to show off what I built. :-)

Razz, sorry for the confusion....you would want to disable the ignition system in your car and turn the engine over with the starter. The FSM will have a table of what your compression should be at a certain RPM. This is why I included an RPM readout on my tester.

Swoope I'll look into what I can do for an adapter, but I think it may come down to just practice. I'm hoping to get a look at HeavyMetals 8 again and this time I'll take some measurments and pictures.

Olddragger, I'd put my tester up against a Mazda unit, but I'm more interested in how the Mazda unit is calibrated honestly. I've got the data sheet for my sensor so I know exactly how accurate it is, but I've got no information on the accuracy of the Mazda tester.

Gregs, did your Mazda tester come with an instruction manual or anything?

-John

Jon316G

iTrader: (1)

Maybe you could send a unit to a forum member who already has the Mazda tester so they can "beta" test it and give feedback on the pros/cons of both setups.
And even give us a readout from both setups and see how they look side-by-side from the same vehicle and same day.
It could be a good selling point if your setup proves just as good, if not better that the others.
Just a suggestion. Good work BTW.

paulmasoner

iTrader: (1)

looks very promising. the communities need something like this since as you said, the other portable options can be ridiculusly priced for what they actually are. would be a very nice option to be able to write the data for recall if its viable

TwistedRotors

I really would like to do a side-by-side comparison, but without data on the accuracy of the Mazda unit how do I prove which one is more accurate? hhmmm...definately something I've got to look into.

Hi Paul, originally I was going to have all sorts of neat features like multiple memory recall with labeling and date/time stamp. I wanted to have an internal memory card that it would save all this data to so I could pop it into my laptop and save it there too. Then I started to actually look at the hardware and software requirements to do all that. So I took another look at the big picture and realized I could do pretty much the same thing with a notepad and a pen. I like things that are simple and just work. Unfortunately with the micro I'm using, even a simple last reading recall after the unit has been switched off is not possible without additional hardware.

-John

alz0rz

iTrader: (41)

simplicity is key.

especially for a utility like this - thread and crank - the end. next.

paulmasoner

iTrader: (1)

Twisted, sounds reasonable, and i have an idea of the hardware expansion it COULD take to offer goodies like that, just didnt know if you perhaps knew a easier way to do it since i am very much a novice in circuitry

Mazurfer

I agree with what Denny(OD) said above.

I'm sure someone with the Mazda tester would do a side by side.

Show me a little data and I'm in for sure.

TwistedRotors

Well I'll do a side-by-side with a Mazda tester, but it won't be much of a comparison until I get some data regarding the accuracy of the Mazda unit.
The sensor I use has a <+/-.5% accuracy as per the factory datasheet.
-John

HeavyMetal699

I got your PM. I'm not sure what day I can do it, but during the week would be best. The hardest part would be scheduling a day at the dealership for them to test it. A same day back to back test, so engine temp won't be an issue, with the Mazda tester would be ideal.

Your tester costs about the same as 2 compression tests at most dealerships. On top of that there was a rumor while back that the dealerships might stop doing compression tests altogether.

Your compression tester sells itself.

neXib

I think people are more worried about the accuracy towards the Mazda device than the real results, even if the Mazda reader is less accurate. As that's what the dealers would use to verify anyway

Phil's 8

iTrader: (3)

I to would be very interested. Keep us informed.

TwistedRotors

Yeah, I was thinking about that at work tonight and realized that's what you guys were getting at. It makes total sense....even if they don't match we can at least find out what the difference is so that it can be compensated for to keep you from wasting a trip to the dealer.
You'll have to forgive me as I'm an RX-7 guy and I'm not used to the dealer being much help at all. I think the icing on the cake was when I went to get a UIM gasket and the parts guy looked through his computer and then told me that there was no such thing as an '87 Turbo II RX-7.

-John

TwistedRotors

PM'd you back.

arghx7

It needs to read the same as the Mazda unit, or damn close. The Mazda unit is the standard by which all other compression testers are judged, whether it is the most accurate or not.

skrubol

iTrader: (1)

The transducer may be acurate to +/- .5%, but the system will not be. For one thing having that swivel in there adds a bit of volume to the combustion chamber, and will reduce the compression ratio.
What transducer did you use? (if you don't mind me asking..)

Razz1

Test it against a new motor with both units.

Send one to sleepy Z or another engine re-builder.

They can measure side by side.

TrochoidMagic

twistedrotor: nice product. get it out, this is a tool i see handy to have sometime in the future.

ASH8

Great looking product so far mate...

Provided the Price is right (and our Australia Dollar is worth more than pea-nuts) you can count me in..

What I think you should do is an A and B Comparison on the same car with the Genuine Mazda Dealer CT and your CT, and publicise the results here and on your website.

Cheers
Ash