| mdxforever |
All cylinders exactly 230psi ! Very little or insignificant variation.
How does that look to you ? :cool:
While I am on the topic I wanted to know -
In any manual or book usually it says "pressure should build up quickly" or "in a few strokes". But what is "quickly" and "few strokes" ?? Typically after how many strokes should a healthy engine really top out the pressure ?
The first stroke usually is about 120-140psi and then by the fourth stroke it gets close to the max(220-230psi). Does that sound normal ? |
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| SuperTech |
| That all looks about right to me. |
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| G. COLTON |
quote:
Originally posted by SuperTech
That all looks about right to me.
Can you give a little explanation? I am used to big v-8's that give a high reading of something around 150 to 160 psi. Just what is the compression ratio of the MDX engine?
George |
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| mdxforever |
ok thanks supertech. thats good to know.
George, per the book the mdx's
Bore = 3.5" (8.89cm)
Stroke = 3.66" (9.3cm)
Compression Ratio = 10.0:1 (i thought it was 10.3 but anyway) |
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| SuperTech |
The 230psi is a little high...but after an engine gets some miles on it, you have some deposits built up on the pistons, valves, and combustion chamber. These deposits take up space, and that effectively raises the compression ratio a little.
Of course everyone's compression gauge may vary a little, but if you're over 185psi on that motor and they're all within 10psi of eachother, everything is fine.
And George, most big V8s have a compression ratio closer to 9:1. Big V8s haven't had higher compression ratios than what the MDX has since the muscle car era. Of course there are a few exceptions in the modern day and age though. |
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| G. COLTON |
Thanks for the info. Yes, things do change. I really have not had to do much under the hood of an automobile in many years. The last compression check I did was a pair of 454's on a boat.
G |
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| mdxforever |
at 230 psi I wonder what the actual or real-world compression ratio is ?
going by simple physics, if the ambient pressure was 14.7 psi then the compression ratio is about 14:1 !
(230 - 14.7)/14.7 = 14.6 |
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| 04mdx4sq |
quote:
Originally posted by mdxforever
at 230 psi I wonder what the actual or real-world compression ratio is ?
going by simple physics, if the ambient pressure was 14.7 psi then the compression ratio is about 14:1 !
(230 - 14.7)/14.7 = 14.6
That was my thought, guess your manual should call for AvGas instead of premium! :D |
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| mdxforever |
| ha ha or probably time for a seafoam treatment ! |
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