Need Info about Compression readings and hot starts
01-31-2015, 10:37 AM
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Need Info about Compression readings and hot starts
Hi, I am a newbie here so forgive me if i say something stupid
I did a compression test on my RX8 2007 Model. The upper rooter reading was 95 PSI and lower rooter reading was 80 PSI. First if anybody can let me know if these are livable readings?
Secondly i saw many posts which mentioned that low compression means poor starting. Well, My car always gets start within 4 seconds either cold or warm temperature.
So, All Gurus, whats your take on this? thanks
I did a compression test on my RX8 2007 Model. The upper rooter reading was 95 PSI and lower rooter reading was 80 PSI. First if anybody can let me know if these are livable readings?
Secondly i saw many posts which mentioned that low compression means poor starting. Well, My car always gets start within 4 seconds either cold or warm temperature.
So, All Gurus, whats your take on this? thanks
01-31-2015, 11:22 AM
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Upper and Lower? Which rotor housing? We meed more info, post the actual results. But either way 80psi is failing.
Anything in the red is failing
Anything in the red is failing
Last edited by 9krpmrx8; 01-31-2015 at 11:26 AM.
01-31-2015, 03:14 PM
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upper rooter 90psi, lower rooter 80psi. these are the actual readings.. spark plugs are fine but lower combustion chamber coil misfires sometimes. Can i change the coil and regain or maintain the compression or there is no hope?
01-31-2015, 03:16 PM
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upper rooter 90psi, lower rooter 80psi. these are the actual readings.. spark plugs are fine but lower combustion chamber coil misfires sometimes. Can i change the coil and regain or maintain the compression or there is no hope?
01-31-2015, 04:03 PM
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01-31-2015, 05:19 PM
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Rotors (not rooters) are front and rear, not top and bottom.
If you were measuring compression between upper and lower plugs on a rotor, your compression readings could change.
If you are using an analog compression tester for a single value it is worthless, since testing at a single plug hole has 3 different compression scores, one for each rotor face. Then you need the altitude and cranking rpm of the test.
Your scores are failing if you did the test properly, but I strongly suspect that you didn't.
Posted From RX8Club.com Android App
If you were measuring compression between upper and lower plugs on a rotor, your compression readings could change.
If you are using an analog compression tester for a single value it is worthless, since testing at a single plug hole has 3 different compression scores, one for each rotor face. Then you need the altitude and cranking rpm of the test.
Your scores are failing if you did the test properly, but I strongly suspect that you didn't.
Posted From RX8Club.com Android App
02-01-2015, 01:42 AM
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Yes, you are right. front rotor is 90psi and rear is 80psi. i did not conduct the test myself, i hired a professional electrician here in my country in Asia as there is no Mazda dealership here, But RIWWP, i will redo the test again by a more professional guy to measure the readings so Rebuilding is not an option here as there is no professional expert here in my country.
Tell me how long the engine can last in these readings and if not then which Engine to swap instead of rotary
Tell me how long the engine can last in these readings and if not then which Engine to swap instead of rotary
02-01-2015, 07:52 AM
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Not mobile today, here is a youtube video showing the engine design, from which you can better understand what is on the other side of each of the spark plug holes:
From that, you can see that behind any given spark plug hole, there are 3 rotor faces. If you compression test with an analog compression tester then it will give you the peak compression for the BEST rotor face. What you need to know is each individual face so you can see what the peak compression is for the WORST rotor face.
The problem isn't the mechanic you went to, the problem is the tool being used. Another mechanic with an analog tester isn't going to do any better for you. What you need is a rotary specific compression tester, as it will record the compression for each face separately.
Since it isn't likely that you have a shop nearby with rotary compression tester, you are going to have to find someone who understands why an analog tester won't work, and will get creative.
Keep in mind that you will NEED the RPM of the test too. "80psi" is passing if the testing speed is ridiculously low, but failing if it's moderately low or any higher. The testing speed DOES matter for the pass/fail results. So does the altitude.
When it comes to replacements, there won't be any 'good' options. I just checked your IP, and it's in Pakistan, is that correct? There are a number of 2JZ engine swapped RX-8s there, and it seems like quite a few people have gotten it pretty straight forward. You won't have the restrictions or challenges we do in the US when it comes to picking another engine, so it's largely going to be whatever you can afford to swap in, and/or what you have the skills to swap yourself.
From that, you can see that behind any given spark plug hole, there are 3 rotor faces. If you compression test with an analog compression tester then it will give you the peak compression for the BEST rotor face. What you need to know is each individual face so you can see what the peak compression is for the WORST rotor face.
The problem isn't the mechanic you went to, the problem is the tool being used. Another mechanic with an analog tester isn't going to do any better for you. What you need is a rotary specific compression tester, as it will record the compression for each face separately.
Since it isn't likely that you have a shop nearby with rotary compression tester, you are going to have to find someone who understands why an analog tester won't work, and will get creative.
Keep in mind that you will NEED the RPM of the test too. "80psi" is passing if the testing speed is ridiculously low, but failing if it's moderately low or any higher. The testing speed DOES matter for the pass/fail results. So does the altitude.
When it comes to replacements, there won't be any 'good' options. I just checked your IP, and it's in Pakistan, is that correct? There are a number of 2JZ engine swapped RX-8s there, and it seems like quite a few people have gotten it pretty straight forward. You won't have the restrictions or challenges we do in the US when it comes to picking another engine, so it's largely going to be whatever you can afford to swap in, and/or what you have the skills to swap yourself.
02-01-2015, 08:57 AM
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Not mobile today, here is a youtube video showing the engine design, from which you can better understand what is on the other side of each of the spark plug holes:
Rotary Engine - YouTube
From that, you can see that behind any given spark plug hole, there are 3 rotor faces. If you compression test with an analog compression tester then it will give you the peak compression for the BEST rotor face. What you need to know is each individual face so you can see what the peak compression is for the WORST rotor face.
The problem isn't the mechanic you went to, the problem is the tool being used. Another mechanic with an analog tester isn't going to do any better for you. What you need is a rotary specific compression tester, as it will record the compression for each face separately.
Since it isn't likely that you have a shop nearby with rotary compression tester, you are going to have to find someone who understands why an analog tester won't work, and will get creative.
Keep in mind that you will NEED the RPM of the test too. "80psi" is passing if the testing speed is ridiculously low, but failing if it's moderately low or any higher. The testing speed DOES matter for the pass/fail results. So does the altitude.
When it comes to replacements, there won't be any 'good' options. I just checked your IP, and it's in Pakistan, is that correct? There are a number of 2JZ engine swapped RX-8s there, and it seems like quite a few people have gotten it pretty straight forward. You won't have the restrictions or challenges we do in the US when it comes to picking another engine, so it's largely going to be whatever you can afford to swap in, and/or what you have the skills to swap yourself.
Rotary Engine - YouTube
From that, you can see that behind any given spark plug hole, there are 3 rotor faces. If you compression test with an analog compression tester then it will give you the peak compression for the BEST rotor face. What you need to know is each individual face so you can see what the peak compression is for the WORST rotor face.
The problem isn't the mechanic you went to, the problem is the tool being used. Another mechanic with an analog tester isn't going to do any better for you. What you need is a rotary specific compression tester, as it will record the compression for each face separately.
Since it isn't likely that you have a shop nearby with rotary compression tester, you are going to have to find someone who understands why an analog tester won't work, and will get creative.
Keep in mind that you will NEED the RPM of the test too. "80psi" is passing if the testing speed is ridiculously low, but failing if it's moderately low or any higher. The testing speed DOES matter for the pass/fail results. So does the altitude.
When it comes to replacements, there won't be any 'good' options. I just checked your IP, and it's in Pakistan, is that correct? There are a number of 2JZ engine swapped RX-8s there, and it seems like quite a few people have gotten it pretty straight forward. You won't have the restrictions or challenges we do in the US when it comes to picking another engine, so it's largely going to be whatever you can afford to swap in, and/or what you have the skills to swap yourself.
Thanks bro for all the important info
02-01-2015, 09:00 AM
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Need one more info, when i drive and go into a little bit of bumpy road, the steering seems to lean right or left itself. which part do i have to get it tested as shocks are totally fine
02-01-2015, 10:16 AM
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Rotors (not rooters) are front and rear, not top and bottom.
If you were measuring compression between upper and lower plugs on a rotor, your compression readings could change.
If you are using an analog compression tester for a single value it is worthless, since testing at a single plug hole has 3 different compression scores, one for each rotor face. Then you need the altitude and cranking rpm of the test.
Your scores are failing if you did the test properly, but I strongly suspect that you didn't.
Posted From RX8Club.com Android App
If you were measuring compression between upper and lower plugs on a rotor, your compression readings could change.
If you are using an analog compression tester for a single value it is worthless, since testing at a single plug hole has 3 different compression scores, one for each rotor face. Then you need the altitude and cranking rpm of the test.
Your scores are failing if you did the test properly, but I strongly suspect that you didn't.
Posted From RX8Club.com Android App
I think you are right that i didn't conduct the tests properly because my car starts within 3 seconds on cold and even on warm and also RPM Needle stays idle. so i will definitely test it again by some good mechanic
02-02-2015, 12:09 AM
#12
40th anniversary Edition
Are you getting what RIWWP is saying ? you need to get a rotary engine specific compression test that will yield six numbers (Three rotor faces, for each of two rotors, for a total of six compression readings) and the cranking rpm and altitude of the test numbers need to be known also. Without that info you will not have a true picture of the health of your engine. It is not about the "good" mechanic" it is about having the proper equipment to do a rotary specific engine compression test.
02-02-2015, 05:17 AM
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Are you getting what RIWWP is saying ? you need to get a rotary engine specific compression test that will yield six numbers (Three rotor faces, for each of two rotors, for a total of six compression readings) and the cranking rpm and altitude of the test numbers need to be known also. Without that info you will not have a true picture of the health of your engine. It is not about the "good" mechanic" it is about having the proper equipment to do a rotary specific engine compression test.
02-02-2015, 04:08 PM
#14
Life After 8K RPM....
You might also want to look into cooling mods, it's crazy hot down there.
Have a thermostat that will let the coolant flow sooner, and have your fans come on at lower temperatures.
and get that compression test for sure.
As RIWWP said, you can swap pretty much anything down there as the labour is very cheap you just need to source the parts.
Have a thermostat that will let the coolant flow sooner, and have your fans come on at lower temperatures.
and get that compression test for sure.
As RIWWP said, you can swap pretty much anything down there as the labour is very cheap you just need to source the parts.
02-03-2015, 05:39 AM
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You might also want to look into cooling mods, it's crazy hot down there.
Have a thermostat that will let the coolant flow sooner, and have your fans come on at lower temperatures.
and get that compression test for sure.
As RIWWP said, you can swap pretty much anything down there as the labour is very cheap you just need to source the parts.
Have a thermostat that will let the coolant flow sooner, and have your fans come on at lower temperatures.
and get that compression test for sure.
As RIWWP said, you can swap pretty much anything down there as the labour is very cheap you just need to source the parts.
Thanks brother, sure i will let the fan come on sooner when the summer starts. I have redone the compression test " Again with analog" " MY BAD" as there is no specific mazda compression tool here and the reading came out " Front rotor 95psi and rear 85 psi.
So i firmly believe that our mechanics dont have the proper tools and my car is fine because its not giving me any issue with race pickup, RPM idols and hot and cold starts
02-08-2015, 07:45 AM
#16
40th anniversary Edition
You can have some faces of the engine that read ok for compression and other faces that are failing, meaning the seals are going bad or you have some damaged areas in your engine. . Any failing faces can mean problems that can lead to a cascading scenario with your engine over time, even if it seems to run fine now. So i still recommend you find somewhere to get a proper rotary compression test done. Your thinking all is fine is only wishful thinking without the proper set of six numbers to prove that. There is a max range of how much compression numbers should vary from face to face and rotor to rotor and still have a healthy engine.
All rotary engine are built by hand and there will always be slight differences in compression numbers , even on healthy engines. But as long are these six numbers are close enough within the proper good number range then they can vary slightly from face to face and rotor to rotor. But if you have huge number differences that signals real problems in your engine. Separate falling faces or failing rotors will eventually lead to more total engine failure. You just need to know the whole story here. Even failing rotary engines can seem to run fine for thousands of miles but will get worse. Hey man maybe your engine will be fine, but you can't play a guessing game without a full set of compression test number from your engine , You may need a reman or rebuild.
All rotary engine are built by hand and there will always be slight differences in compression numbers , even on healthy engines. But as long are these six numbers are close enough within the proper good number range then they can vary slightly from face to face and rotor to rotor. But if you have huge number differences that signals real problems in your engine. Separate falling faces or failing rotors will eventually lead to more total engine failure. You just need to know the whole story here. Even failing rotary engines can seem to run fine for thousands of miles but will get worse. Hey man maybe your engine will be fine, but you can't play a guessing game without a full set of compression test number from your engine , You may need a reman or rebuild.
02-09-2015, 05:42 AM
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You can have some faces of the engine that read ok for compression and other faces that are failing, meaning the seals are going bad or you have some damaged areas in your engine. . Any failing faces can mean problems that can lead to a cascading scenario with your engine over time, even if it seems to run fine now. So i still recommend you find somewhere to get a proper rotary compression test done. Your thinking all is fine is only wishful thinking without the proper set of six numbers to prove that. There is a max range of how much compression numbers should vary from face to face and rotor to rotor and still have a healthy engine.
All rotary engine are built by hand and there will always be slight differences in compression numbers , even on healthy engines. But as long are these six numbers are close enough within the proper good number range then they can vary slightly from face to face and rotor to rotor. But if you have huge number differences that signals real problems in your engine. Separate falling faces or failing rotors will eventually lead to more total engine failure. You just need to know the whole story here. Even failing rotary engines can seem to run fine for thousands of miles but will get worse. Hey man maybe your engine will be fine, but you can't play a guessing game without a full set of compression test number from your engine , You may need a reman or rebuild.
All rotary engine are built by hand and there will always be slight differences in compression numbers , even on healthy engines. But as long are these six numbers are close enough within the proper good number range then they can vary slightly from face to face and rotor to rotor. But if you have huge number differences that signals real problems in your engine. Separate falling faces or failing rotors will eventually lead to more total engine failure. You just need to know the whole story here. Even failing rotary engines can seem to run fine for thousands of miles but will get worse. Hey man maybe your engine will be fine, but you can't play a guessing game without a full set of compression test number from your engine , You may need a reman or rebuild.
I totally agree with you, But here in my country ( Pakistan), mechanics use analog testers and do not know how to measure each face with cranking rpm, that's why, readings are always wrong. No one has here Mazda specific compression tool.
So that's why i said that maybe my engine is fine if its is starting in hot and cold under 3 seconds. the ONLY error that computer noted was rear cylinder misfire but that can be due to some bad coil or plug, otherwise the car seems Okay when it comes to pick and racing.
Any idea where i can buy Mazda standard compression tool and any DIY Method for this test to run? if yes then please guide
02-09-2015, 06:18 PM
#18
Life After 8K RPM....
Yes, I have checked with numerous friends no one knows of a rotary mechanic in the country.
Since, MAzda never released rotary powered cars there to begin with.
Another suggestion to help your engine last is, take out the CAT since they don't have emission regulations. This will help your engine last longer, and unleash a little extra hp.
change your oil every 3k, and stay on top of Ignitions components.
It'll be alot easier and cheaper for you to import an engine from Japan directly.
Hope this car serves you for long, all the best brother
Since, MAzda never released rotary powered cars there to begin with.
Another suggestion to help your engine last is, take out the CAT since they don't have emission regulations. This will help your engine last longer, and unleash a little extra hp.
change your oil every 3k, and stay on top of Ignitions components.
It'll be alot easier and cheaper for you to import an engine from Japan directly.
Hope this car serves you for long, all the best brother
02-10-2015, 06:13 AM
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Yes, I have checked with numerous friends no one knows of a rotary mechanic in the country.
Since, MAzda never released rotary powered cars there to begin with.
Another suggestion to help your engine last is, take out the CAT since they don't have emission regulations. This will help your engine last longer, and unleash a little extra hp.
change your oil every 3k, and stay on top of Ignitions components.
It'll be alot easier and cheaper for you to import an engine from Japan directly.
Hope this car serves you for long, all the best brother
Since, MAzda never released rotary powered cars there to begin with.
Another suggestion to help your engine last is, take out the CAT since they don't have emission regulations. This will help your engine last longer, and unleash a little extra hp.
change your oil every 3k, and stay on top of Ignitions components.
It'll be alot easier and cheaper for you to import an engine from Japan directly.
Hope this car serves you for long, all the best brother
Thanks Brother. i also noticed that a vaccum pipe from map sensor to engine was cut off, so i fixed it today, i will let you know how that will work. Also will change ignition coils soon.
Removing the CAT will make exhaust sound loud so thats why i'm not doing it. Everything in the engine seems perfect. I talked to my electrician and they don't know how to put the fan to come on sooner. so guide me about cooling mods.
Also sometimes my check engine light shows and blink for sometime and then it disappears. My electrician told me to put high octane in it and the problem will be solved but i believe that the rear ignition coil misfire sometimes. any ideas about that?
thanks and waiting for the reply
Last edited by RX8 pearl red; 02-10-2015 at 07:46 AM. Reason: added more information
02-10-2015, 08:13 AM
#20
40th anniversary Edition
Do not wait to change your ignition coils if evidence is you have a bad one. A bad coil will cause uneven ignition and fuel burn which can cascade into engine trouble and possible engine failure and even cat failure. DONT wait. rotary engines are super sensitive to any poor or failing ignition component, coils, wires and plugs. Ignore these and you might be ultimately paying for a new engine, seriously. (I have owned seven rotaries,so I have some knowledge here) Check the threads here for moderator RIWWP's good post on ignition coil choices, what to buy in each price range and what to avoid. If you have the ability to shop internationally, the best choice are the BHR coils and wires with new plugs. The BHR coils and wires will last the lifetime of your car and offer a slight bump in performance and mileage . Just google Black Halo Racing. And yes, ALWAYS use premium gas in your RX8. Using anything with less octane will lead to poorer engine performance and ultimate engine damage (with possible detonation damage).
Last edited by gwilliams6; 02-10-2015 at 08:22 AM.
02-10-2015, 09:59 AM
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Do not wait to change your ignition coils if evidence is you have a bad one. A bad coil will cause uneven ignition and fuel burn which can cascade into engine trouble and possible engine failure and even cat failure. DONT wait. rotary engines are super sensitive to any poor or failing ignition component, coils, wires and plugs. Ignore these and you might be ultimately paying for a new engine, seriously. (I have owned seven rotaries,so I have some knowledge here) Check the threads here for moderator RIWWP's good post on ignition coil choices, what to buy in each price range and what to avoid. If you have the ability to shop internationally, the best choice are the BHR coils and wires with new plugs. The BHR coils and wires will last the lifetime of your car and offer a slight bump in performance and mileage . Just google Black Halo Racing. And yes, ALWAYS use premium gas in your RX8. Using anything with less octane will lead to poorer engine performance and ultimate engine damage (with possible detonation damage).
I googled and contacted BHR, waiting for there reply if they can ship them to Pakistan.
Can you arrange BHR coils with plugs for me and send it to me in Asia? i will be really grateful. Kindly let me know about the total price please if shipping is possible by you.
If somehow BHR can not be arranged then can i go for oem coils?
Last edited by RX8 pearl red; 02-10-2015 at 10:17 AM. Reason: added more information
02-10-2015, 10:59 AM
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02-11-2015, 01:23 AM
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Changed one faulty Coil which was not sparking at all. Also put Hi Octane gas with Liqui Moli fuel injector cleaner and all problems fixed. Now car starts in 2 seconds whether hot or cold
02-11-2015, 09:12 AM
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Rotors (not rooters) are front and rear, not top and bottom.
If you were measuring compression between upper and lower plugs on a rotor, your compression readings could change.
If you are using an analog compression tester for a single value it is worthless, since testing at a single plug hole has 3 different compression scores, one for each rotor face. Then you need the altitude and cranking rpm of the test.
Your scores are failing if you did the test properly, but I strongly suspect that you didn't.
Posted From RX8Club.com Android App
If you were measuring compression between upper and lower plugs on a rotor, your compression readings could change.
If you are using an analog compression tester for a single value it is worthless, since testing at a single plug hole has 3 different compression scores, one for each rotor face. Then you need the altitude and cranking rpm of the test.
Your scores are failing if you did the test properly, but I strongly suspect that you didn't.
Posted From RX8Club.com Android App
02-12-2015, 06:47 AM
#25
40th anniversary Edition
My guess is baring any customs issue, that yes BHR may be able to ship to Pakistan. The BHR coils are lifetime,they work great, are built super strong and will give a slight power and mileage boost. Highly recommended by hundreds of club members. Charles of BHR is a great guy and will help all he can. He makes great RX8 products, top quality.
Other coils need changing out every 30k miles. If you get OEM coils instead, try to get the latest OEM version the "C" coils, instead of the older design A or B coils. The "C" coils so far have been shown to be better built and last longer.
Contact BHR | Black Halo Racing
BTW- I dont know if this is possible. But if you have a few RX8 owners near you, it may be worth the purchase. There is a lower cost rotary engine tester that will work with your laptop computer . I know because a friend of one of our local RX8 club group (an RX7 owner) brought one to a local club meet and used it to test several of the engines of some new RX8 owners in our group. If I can find a link to this on the internet, I will post it. Following the instructions this tester could be used by anyone with basic mechanic skills (getting a spark plug off, one at a time) and some computer knowledge (Using the software to calculate the results.) I will look for this for you. It did work to get proper compression readings .
Best to you. We all are here to help you all we can, this is a great group worldwide.
Other coils need changing out every 30k miles. If you get OEM coils instead, try to get the latest OEM version the "C" coils, instead of the older design A or B coils. The "C" coils so far have been shown to be better built and last longer.
Contact BHR | Black Halo Racing
BTW- I dont know if this is possible. But if you have a few RX8 owners near you, it may be worth the purchase. There is a lower cost rotary engine tester that will work with your laptop computer . I know because a friend of one of our local RX8 club group (an RX7 owner) brought one to a local club meet and used it to test several of the engines of some new RX8 owners in our group. If I can find a link to this on the internet, I will post it. Following the instructions this tester could be used by anyone with basic mechanic skills (getting a spark plug off, one at a time) and some computer knowledge (Using the software to calculate the results.) I will look for this for you. It did work to get proper compression readings .
Best to you. We all are here to help you all we can, this is a great group worldwide.
Last edited by gwilliams6; 02-12-2015 at 07:04 AM.