The Ultimate Guide to Mazda RX8 Compression Testing

This is the ultimate guide to Mazda Rx8 rotary engine compression, compression testing, and getting meaningful compression results for both a hot and cold engine. These renesis wankel engines are unique and this video should help guide you to diagnose one that is not running, learn why hot start problems occur, or just to check to make sure your engine is running healthy!
Rotary Compression Calculator: foxed.ca/index.php?page=rotar...
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Wow! You actually read the description! If you have low compression, you will probably need an engine rebuild. I am currently working on an rx8 engine rebuild series coming this fall! Don't tell anyone, they didn't read the description! I will be posting some stuff on my Instagram of this project before the project comes to the channel, so be sure to follow me so you don't miss anything!
#rx8 #rotary #compression #lowcompression #compressiontest

[@Zrvsgiorgos]

Yesterday, I started searching information about Rx8 compression, and about compression testers, and right on time, a new japanda tuning video pops up. You haven't made a video since more than two weeks, and suddenly, you upload one exactly about what i had trouble with. That's why I'm still one of your subscribers!🇯🇵🇯🇵

[@Kyle3195]

Just bought some merch to support your channel. The videos are great and help keep me motivated on my RX-8 restoration project.

[@shanvlogs3262]

Finally we got a new video.. 😍😍😍

[@letmecthevid]

your videos have been very helpful and well made. Thank you!

[@PowerWheelsAustralia]

I just did a compression test on my rew swapped Rx8 yesterday and the results are rebuild time.. I’m looking forward to pulling my engine out and upgrading a few things

[@Xehanortlw]

Unfortunately I got into a wreck a month back I love my rx8 took it to a rotary specialist to do a compression test to see if it's worth saving

[@ahmadsyawal8052]

Good information 👍👍👍

[@colbyjones1267]

Just did a compression test on my rx8 that I just bought. Averaged about 112 normalized at 250 rpm

[@ashleyfelizmatoz247]

Excelente compresion esta muy bien

[@jaceknox2590]

Hi I am wanting to buy new rims for my rx 8 but they only can in 19in and 20in i am wanting to put 20in in the rear and 19 in the front do u think that the 19 will fit on the front

[@JohnHonda2]

Where you get that front splitter?? Looks good👍

[@erichansen4718]

Thanks.

[@carguy1013]

does your car pull fast(pushes you well into the seat)? Smooth revs? Easy cold and hard start? Smoke?

[@Matth-yw1qm]

How long is your warm start?

[@billyz1904]

What's your opinion about 192hp rx8 5 speed manual (Europe). They are much cheaper and more common to find in Greece at least and with less milage than the 231 that's more expensive and with more milage.Are they less fun than the 231 because of the 7.500 rpm than the 9.000??

[@fetiqe]

Where do you get the spoiler from?

[@askannav2094]

Great video.. just two questions .. 1: other compression videos online show that they also compression test on the trailing plug as well as the leading plug. Would this make a difference to the overall results? 2: You would assume that as the engine warms up both the rotors & housing expand, thus making the compression go up. If so wouldn't the compression of a cold engine be comparable to a warm engine, all things being equal ?

[@malijames12]

I'm not an expert, so take these with a grain of salt. 1. There wouldn't be a meaningful difference. Compression testers record peak pressures within the combustion chamber. According to the laws of physics, the pressure is the same anywhere inside a closed system. Think of it like a doctor taking a patient's temperature from both ears. 2. While it is the case that the rotors expand (alone would increase compression), so does the housing. But the housing expands in the opposite direction of the rotor, and they "run away" much farther than the rotor can grow. The result is that the gap between the rotor and its housing is increased when warm. This reduces the compression ratio of the motor and diminishes its sealing capabilities; in turn, the higher, more desirable pressures become impossible. The reason for this is similar to when you press a bendy ruler at both ends, it bows outward.

[@GRFX19]

Good video but some mistakes. don't remove the Leading Spark Plugs and insert the tester in the Trailing Sparks plug hole.

[@PeterArmour]

Ive heard both. Does it really make much of a difference? Seeing how these engines work I don't see how it would matter if it is leading or trailing plugs removed.

[@LightGesture]

100s are low???

[@zowda4368]

I’m having trouble getting into reverse on my RX8, any tips?

[@JapandaTuning]

push down on the shifter! If its a problem, try changing your trans fluid with something like redline mt-90

[@tiborklein5349]

Great video, but you could have mentioned what compression is considered healthy, normal and low. I use the metric system and from what I found online yours is in the normal territory (7.1 bar) and should be fine for a while...

[@JapandaTuning]

Technically, anything under 7 bar (about 100 psi) is failing. It's not like the car won't run, but the blowby will cause failure to occur more quickly.

[@tiborklein5349]

@@JapandaTuning No, it's not failing. You'd have to be under 6 bar for that.

[@ao8271]

@@tiborklein5349 above 7 to be safe.

[@carguy1013]

@@JapandaTuning does your car pull fast? Smooth revs? Easy cold and hard start? Smoke?

[@joselperez9384]

Some day we will be able to billet the rotor housings... THE TIME WILL COME FOR THE RENESIS

[@carguy1013]

When . How hard is a bullet rotor. Pros and cons.

[@joselperez9384]

@@carguy1013 Cons: Still a Renesis Rotor. Pros: Availability.

[@wepteditz2353]

Do almost all rx8s need a engine rebuild once in there life

[@youngboi_yt]

Yeah lol

[@AndrewFerranRcjourneyz]

Cool

[@matercheff]

Front 89 95 92 rear93 93 96 2006 RX8 what do you guys think please help!

[@matercheff]

250rpm btw

[@rotaryperfection]

Watched the whole thing! How come you made no mention of the compression numbers as it relates to the elevation you're testing in? In some areas, even 90psi all faces is perfectly fine. This is hardly an Ultimate guide to compression. Now your numbers as it relates to temp range are sound but you left out the elevation factor which tells you the TRUE corrected numbers.

[@JapandaTuning]

I am sure I could have mentioned that, sorry for leaving that out. That is because the compression tester I have (link in the description) normalizes at 250 rpm and corrects for elevation pressure. Also in the link in the description for normalizing the compression data, there is a place to put your site of testing's elevation to correct for that. Sorry for not going into more depth in the video.

[@rotaryperfection]

@@JapandaTuning Yea because when these guys go testing their engines, the last thing we need is them thinking 100PSI is failing without understanding the full scope of the numbers. Back in Dec 2018, I bought a used 2006 Rx8 from Copart with 123,000 miles. Engine was flooded and had 65psi all faces after I got ot running. Most would say it's rebuild time but not me. I know all the compression restoring secrets. I did my carbon cleanings on the engine, drove it for 1,000 miles and the compression shot up to 95psi all faces. Corrected for my elevation. My corrected numbers were 110psi. Not bad for an original engine Rx8 with that many miles

[@caszzxs4104]

RotaryPerfection can you list out your carbon cleaning techniques please?

[@anthonydodier6143]

For some of you if you want the compression chart to know what psi is normal for every 13b here it is www.mazdatrix.com/rotor-weight-and-compression-chart/

[@192eDPI]

rx8かっこいいよね！！ 日本の車気に入りましたか？

[@jasonsultana3924]

もちろん！とくにロータリー。今ロータリーがもう出てなくて残念ですね

[@192eDPI]

Jason Sultana 僕もロータリー大好きです！ また新しく開発してくれたら嬉しいですね〜

[@mischiefpwns]

Your compression isnt too bad but you will see some reduced power. You could keep driving it for at least another 10k miles before a rebuild is necessary. I find anything above 6 bar is fine with a good ignition system. Your cold vs hot compression is pretty meaningless though despite the math and science work you put in. Many engines are different and the co-efficient wont be accurate due to spring rate differences. If you cant get the engine running and hot, it's not worth it to compression test. Even with low compression, the engine should always be able to start and run while cold. Great vid as always, your compression is actually better than my 6 speed manual XD.

[@JapandaTuning]

Yeah and when I rebuild it, I am looking to bridgeport also. As for the cold compression test, I know its not perfect like I mentioned in the video, but it should at least be a bit better. (I actually got the idea for this because I am working on an rx8 that wont start and want to check compression). Thanks for the feedback!

[@mischiefpwns]

@@JapandaTuning it should still start, even with low compression. Probably just got flooded. Try swapping in new coils, plugs and wires and starter if cranking below 250 RPM. After this, do the deflood process. got an RX8 running again like this and after testing it showed 4-5 bar hot.

[@mischiefpwns]

@@JapandaTuning Bridgeport on the RX8 good if you are tracking it. You'll see a good power increase. Keep in mind it will completely screw your idle though.

[@theoneTMoney]

lost chance to change math triangle to rotor

[@Snoopi25]

Trust me when I say, your compression is NOT LOW in the least loool... I have been running my RX-8 for a year with compression in the high 70's on the rear rotor and low 60's on the front rotor before my engine blew entirely. Until your numbers start going down to the 80 PSI range, you have absolutely NOTHING to worry about. Yes, you might lose some power, but if you clean off the parts of the engine (like your valves), and make sure there are no vacuum leaks, and that they are actuating properly, you will have a healthy RX-8. I can't remember if you are premixing or not, but that will help as well. I just got a freshly rebuilt motor with a bunch of mods done to it (street port, dowel pins, stud kit, RX-7 apex seals, etc.) and my compression numbers were above 105 and around 110. Your engine is healthy, bud.

[@Snoopi25]

I forgot to mention, that with my low compression numbers that I specified, I had NO hot-start issues... I kept my ignition in check, and I upgraded to a 2kw starter over the Series 1 starter.

[@infamousrx8960]

yea it really not bad but he uses it a a dedicated track car so he should probably have at least 4k stored away for a rebuild

[@Tyrese-oz6jo]

Snoopy25 where did you get this done at just out of curiosity

[@Snoopi25]

@@Tyrese-oz6jo Elite Rotary; I learned SO much about rotaries ever since I got in touch with them about 5 years ago. I knew I needed a rebuild from 2 summers before my engine blew, but I didnt have the finances at the time. Full time college student with a part time job and an RX-8 as a daily driver lol

[@Tyrese-oz6jo]

Snoopy25 how much did it cost you and where are they located