Cylinder compression


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Asphaltmaniac
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Cylinder compression

Post by Asphaltmaniac »



I have 180K on my 06 and although it runs beautifully absolutely with no oil burning. I decided it was time to check cylinder compression. All six are 155 to 160 PSI. But the manual calls for 201 PSI. Seems too me thats high for a 9.8 too 1 engine that does not require premium fuel.
Has anybody else run a compression check and what did you find?
Thank you.


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Re: Cylinder compression

Post by Steve F »

Personally, I have not, but doing some checking on the internet, it seems the typical norm is 190, 200-210.
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Re: Cylinder compression

Post by AZgl1800 »

Asphaltmaniac wrote: Sun Jan 14, 2018 8:33 pm I have 180K on my 06 and although it runs beautifully absolutely with no oil burning. I decided it was time to check cylinder compression. All six are 155 to 160 PSI. But the manual calls for 201 PSI. Seems too me thats high for a 9.8 too 1 engine that does not require premium fuel.
Has anybody else run a compression check and what did you find?
Thank you.
I assume that you held the throttle open for the test?
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Re: Cylinder compression

Post by jinx »

I did a check on my 2006 at 150,000 miles and all cylinders where between 190 and 205. So you may want to check yours again or use a different gauge.
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Re: Cylinder compression

Post by DaveO430 »

They are all pretty close which is good. Did you have the engine warm and the throttle open?
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Re: Cylinder compression

Post by FlyBoy2121 »

I GoldWingMen

The important thing is that the compression on all the cylinders must be less than 5 to 10 pounds between all the cylinders.
But has 5 pounds no problem.

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Re: Cylinder compression

Post by thrasherg »

The gauge that you use makes a huge difference, I find pressure gauges with long hoses always read much lower than gauges with short hoses (length of the line from the spark plug hole to the actual gauge), as FlyBoy states, the actual value is not really that critical, it is important to have the same reading across all cylinders. I would say based on your readings that your engine is in great condition and the low pressure reading is either due to an inaccurate gauge or perhaps it has a long hose lead and that is causing a lower reading? Maybe you can try a different gauge just to see if that makes a difference. As stated the engine needs to be warm and the throttle should be held wide open during the test and you just keep cranking the engine until the gauge stops showing an increase in pressure.

Gary
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Re: Cylinder compression

Post by Asphaltmaniac »

AZgl1800 wrote: Sun Jan 14, 2018 9:16 pm
Asphaltmaniac wrote: Sun Jan 14, 2018 8:33 pm I have 180K on my 06 and although it runs beautifully absolutely with no oil burning. I decided it was time to check cylinder compression. All six are 155 to 160 PSI. But the manual calls for 201 PSI. Seems too me thats high for a 9.8 too 1 engine that does not require premium fuel.
Has anybody else run a compression check and what did you find?
Thank you.
I assume that you held the throttle open for the test?
yes, wide open.
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Re: Cylinder compression

Post by Asphaltmaniac »

thrasherg wrote: Mon Jan 15, 2018 9:17 am The gauge that you use makes a huge difference, I find pressure gauges with long hoses always read much lower than gauges with short hoses (length of the line from the spark plug hole to the actual gauge), as FlyBoy states, the actual value is not really that critical, it is important to have the same reading across all cylinders. I would say based on your readings that your engine is in great condition and the low pressure reading is either due to an inaccurate gauge or perhaps it has a long hose lead and that is causing a lower reading? Maybe you can try a different gauge just to see if that makes a difference. As stated the engine needs to be warm and the throttle should be held wide open during the test and you just keep cranking the engine until the gauge stops showing an increase in pressure.

Gary
The flexible section of my hose is almost 14 inches and is not covered with a metal braid to prevent expansion. I will source out a smaller section and test again.
Thank you!!
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Re: Cylinder compression

Post by Asphaltmaniac »

DaveO430 wrote: Mon Jan 15, 2018 7:14 am They are all pretty close which is good. Did you have the engine warm and the throttle open?
I was very happy too get such a tight group. The engine was warm and I held the throttle wide open. Another member suggested that the hose on my gauge may be to long and that will give a lower reading. The hose I used is 14 inches long. I'd bet good money he is right. I will source out a smaller length and test again.
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Re: Cylinder compression

Post by brian.peters »

as others have said the actual reading is not as important as consistency between cylinders. rule of thumb is within 10%. Many things will impact the actual readings but throttle position is really not one of them. I've done hundreds of compression checks on everything from big block V8s to 50cc chain saws and throttle has never made a difference. It makes sense as you will eventually fill the cylinder and cranking speed is not fast enough for the throttle blades to create a meaningful restriction.

I'd run it and not worry about it in the least.
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Re: Cylinder compression

Post by GoldWingrGreg »

Asphaltmaniac wrote: Sun Jan 14, 2018 8:33 pm All six are 155 to 160 PSI. But the manual calls for 201 PSI.
Has anybody else run a compression check and what did you find?
Yes ... on many, and I too have always wondered about the Honda spec of 201 PSI after 5 bumps from the starter. In the Service Manual it says to take a reading after cranking it over 5 times. If I take a reading then, I always get reading from 160-175 PSI ... not 201. However, I take 2 reading at 2 different points while cracking each cylinder 1 time. As it cranks, at 5 bumps I make a mental note of the compression then while continuing to crank it and then stop the cranking after 15 bumps. I then record both reading ... i.e. 165/210. Usually the reading after 15 bumps is between 205-225 PSI.

Hopefully this information helps clear up why some report getting readings like you have while others report compression much higher. Healthy compression after 15 bumps will be 205-210. Higher reading (225 PSI) after 15 bumps is from either carbon buildup and/or poorly adjusted valves.
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Re: Cylinder compression

Post by Asphaltmaniac »

GoldWingrGreg wrote: Wed Jan 17, 2018 5:47 pm
Asphaltmaniac wrote: Sun Jan 14, 2018 8:33 pm All six are 155 to 160 PSI. But the manual calls for 201 PSI.
Has anybody else run a compression check and what did you find?
Yes ... on many, and I too have always wondered about the Honda spec of 201 PSI after 5 bumps from the starter. In the Service Manual it says to take a reading after cranking it over 5 times. If I take a reading then, I always get reading from 160-175 PSI ... not 201. However, I take 2 reading at 2 different points while cracking each cylinder 1 time. As it cranks, at 5 bumps I make a mental note of the compression then while continuing to crank it and then stop the cranking after 15 bumps. I then record both reading ... i.e. 165/210. Usually the reading after 15 bumps is between 205-225 PSI.

Hopefully this information helps clear up why some report getting readings like you have while others report compression much higher. Healthy compression after 15 bumps will be 205-210. Higher reading (225 PSI) after 15 bumps is from either carbon buildup and/or poorly adjusted valves.
I borrowed a tester from Autozone and it clearly is in better shape than my old one. Cylinder 1 is 190. #3 is 185 with the rest being 170 through 176. There is 10% difference between the high and low, which is fine. But I was hoping for just a little better....
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Re: Cylinder compression

Post by GoldWingrGreg »

Asphaltmaniac wrote: Fri Jan 19, 2018 6:52 pm

I borrowed a tester from Autozone and it clearly is in better shape than my old one. Cylinder 1 is 190. #3 is 185 with the rest being 170 through 176. There is 10% difference between the high and low, which is fine. But I was hoping for just a little better....
How many bumps to get to your readings ???
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Asphaltmaniac
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Re: Cylinder compression

Post by Asphaltmaniac »

GoldWingrGreg wrote: Fri Jan 19, 2018 8:52 pm
Asphaltmaniac wrote: Fri Jan 19, 2018 6:52 pm

I borrowed a tester from Autozone and it clearly is in better shape than my old one. Cylinder 1 is 190. #3 is 185 with the rest being 170 through 176. There is 10% difference between the high and low, which is fine. But I was hoping for just a little better....
How many bumps to get to your readings ???
8-10 Id guess.
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Re: Cylinder compression

Post by Asphaltmaniac »

GoldWingrGreg wrote: Fri Jan 19, 2018 8:52 pm
Asphaltmaniac wrote: Fri Jan 19, 2018 6:52 pm

I borrowed a tester from Autozone and it clearly is in better shape than my old one. Cylinder 1 is 190. #3 is 185 with the rest being 170 through 176. There is 10% difference between the high and low, which is fine. But I was hoping for just a little better....
How many bumps to get to your readings ???
Had an AH HA! moment here this morning. When testing my Toyota or big block chevelle with my vacuum gauge. Due to my 4300ft altitude I add 4 points. So when my big block idles at rock steady @16 inches I know at sea level it would be 20 inches. Beautiful! So accounting for altitude my wings compression numbers get closer to whats stated in the manual. So instead of 190 down to 170. Its really 211 down too 189. Much closer too that 201 stated in the factory manual. ahhhh I feel much better now. :D
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Re: Cylinder compression

Post by DaveO430 »

Yes altitude does matter. Numbers given are at sea level. I never gave a compression test much value except to see if one or more were way lower than the others. If you want to see where the compression is going if it's low a leak down test is the best way.


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