Ill keep this short and sweet for the time being. Anybody else run in to some really low compression test numbers on Mivec cars with aftermarket cams? I have ran in to numbers in the low 100s in good running cars with no symptoms of anything being wrong.

The factory numbers are lower than the non mivec cars of course. And the aftermarket cams can be ground on completely different centers etc. I just wonder if the numbers can vary depending on your mivec maps, and where the cams fall once you shut the engine down and the oil pressure is lost. I would think they would all go back to the same spot

 

What comp #'s are you seeing, 140?

 

I have seen them as low as 115! In cars that were running fine...

 

I know this post is kinda old but i have heard that the overlap on bigger cams will cause lower compression readings

 

I have ran into the same issue with my built 06 Evo 9. It has cosworth 272 cams with Manley internals and my cold compression is about 100 to 105 and the hot is around 110 on all four cylinders. I have no issues with the way the car runs or idles.

 

Yeah I thought mine had low compression too, but I guess not Mine was 130-125-120-120 and i'm running a stock motor with Cosworth M2's. Car was warm if I remember correctly, also has 121k on the odometer

 

I am pretty sure the internals that I have are causing the compression to drop too, but I am still gonna do a leak down check to be sure there is nothing wrong. The engine was just built about 13 months ago and maybe has 20 k on it

 

Stock 2005 Evo VIII, 67000 miles, idle pressure is 110 psi in two cylinders, 108 in the other two. Runs fine. Hopefully that gives you another baseline.

 

After 30minutes of "run-in" i had 155psi on all 4 cylinders with:
2.3 litre block
GSC S2's Mivec
Cold
done with all spark plugs out, and throttle body open.
Mahle 9:1 pistons (86mm) and Evo 9 Headgasket. (decked block and skimmed head)

 

Own an 06 Evo 9 with Buschur Stage 3 block and Cosworth 272s.... all 4 cyl at 110. I was worried myself, but seems to me alot of evo owners are experiencing this. Leak down test this afternoon!

 

Thanks for keeping this updated the last cpl years guys. I assumed all was ok back then, but that was the only evo 9 engine I had experience with at the time and we had done a few things that I was concerned how it was effecting the cranking compression. Fast forward a a cpl years and now I have my own engine machine shop and a lot more experience with Mivec cars

 

Speaking of....

 

Nice. What chassis is that in?

 

2001 Mustang.

 

Sweet!!! Almost did the same in my Conquest until I bought my current evo. Keep us updated.