Boatmad.com


Reply
 
Thread Tools Display Modes
 
Old 11-12-2006, 05:05 PM   #1
Registered User
 
Country: Poland
Location: Warsaw

Join Date: Dec 2005
Location: Warsaw
Posts: 568
compression - help

I have got information that engine I want to buy have compression 148

What the hell id this?? How many Bar is this??

It is XR2 from 1997. Is it good compression for that engine??

Please help
__________________

Mike_G is offline   Reply With Quote
Old 11-12-2006, 06:30 PM   #2
jw.
Registered User
 
jw.'s Avatar
 
Location: Scotland
Interests: Hole maker
Boat make: Humber Ocean Offshore
Engines: KAD 300/DPX

Join Date: Mar 2004
Location: Scotland
Posts: 954
It's about 10bar. A bit high, I would have thought. But what do I know?
__________________

__________________
JW.
jw. is offline   Reply With Quote
Old 11-12-2006, 06:34 PM   #3
Registered User
 
Toffy's Avatar
 
Country: Belgium
Location: near Ghent
Occupation: engineer
Interests: boating, wakeboarding, snowboarding, fitness
Boat name: Outlaw
Boat make: Phantom 21ft
Engines: Yamaha 200hp
Cruising area: Zele / Kanaal Gent-Terneuzen

Join Date: Jun 2006
Location: near Ghent
Posts: 473
Quote:
Originally Posted by Mike_G View Post
I have got information that engine I want to buy have compression 148

What the hell id this?? How many Bar is this??

It is XR2 from 1997. Is it good compression for that engine??

Please help
"148" is most likely the compression value in psi-units. (pound per square inch)
psi values are most commom in compression measurement
1 psi = 0,0689475729 bar (btw, you can google this : type in "psi -> bar" in the search field and press enter)
148 psi = about 10,2 bar

I' don't know XR2's that good. 148psi sounds high and therefore good to me.
But you have only 1 value ! Having equal measurements on all cilinders is also very important. When one measurement is 'down', this means you have a problem cilinder, that needs to be fixed...

The other guys here on the site can confirm if the 148psi rating sounds OK.
They probably are able to predict which cilinder is usually a 'problem' cilinder on this engine type...

Hope this helps, T.
Toffy is offline   Reply With Quote
Old 12-12-2006, 12:18 AM   #4
Registered User
 
Burty's Avatar
 
Country: UK
Location: Weston Super Mare
Occupation: Electrical Engineer

Join Date: Mar 2004
Location: Weston Super Mare
Posts: 6,351
Send a message via AIM to Burty
i think xr2 run around 160 psi. as long as all clyinders are within 5 psi of each other it should be ok
Burty is offline   Reply With Quote
Old 12-12-2006, 01:22 AM   #5
Registered User
 
RossM's Avatar
 
Boat make: Phantom 23

Join Date: Mar 2006
Posts: 1,650
Send a message via MSN to RossM
yep will second burty's 160, went to pick up a rebuilt xr2 with 10 hours onit and they were all just over 160
RossM is offline   Reply With Quote
Old 12-12-2006, 08:14 AM   #6
Registered User
 
Country: Poland
Location: Warsaw

Join Date: Dec 2005
Location: Warsaw
Posts: 568
But do you think I can ride on this engine on 148 or will I have to rebuild it??
Offcours if difference between cylinders will be less than 5 psi??
Mike_G is offline   Reply With Quote
Old 12-12-2006, 09:34 AM   #7
BananaShark Member
 
Cookee's Avatar
 
Country: UK
Location: Salcombe South Devon
Occupation: Racer and builder
Interests: Winning races
Boat name: BananaShark
Boat make: BananaShark 34' Race
Engines: Twin Yanmar BY 260's

Join Date: Mar 2004
Location: Salcombe South Devon
Posts: 4,632
It all depends on the age of the engine - the earlier ones were only 175 hp not 200 and might have lower compression?
__________________
Cookee



British Champions! RIB Formula 1 2005
National Speed Record Holder at 90.15 (still)

www.bananasharkracing.com
Cookee is offline   Reply With Quote
Old 12-12-2006, 10:02 AM   #8
Senior Member
 

Join Date: May 2006
Posts: 277
The actual compression number is so unimportant vs the fact that the compression between each cylender needs to be the same or within about 5.

The guages you buy from Halfords are quite often 20% out, and age, poor handling etc makes them very inaccurate, so looking for a specific figure is almost irellevant.

What is critical is that they all read the same ( or near the same )

Finally a very high compression could indicate skimming, and a tendancy to detonate - which is bad, but you should see this affecting the cylenders, due to one side getting leaner air and one side getting richer air, so they should be out of the pressure range differential if this did occur.
FabFour is offline   Reply With Quote
Old 12-12-2006, 12:23 PM   #9
Registered User
 
Country: england
Location: southampton
Occupation: boat builder /engineer/powerboat training centre
Boat make: rib/cat/mono/tri
Cruising area: i DONT CRUISE anywhere

Join Date: Apr 2004
Location: southampton
Posts: 163
Send a message via AIM to PHANTOM EVOLUTION
compression

just to add more fun to the compression of this XR2 ,you could have the left/right hand banks different by more than 5 psi and from mercurys point of view theres nothing wrong with the engine,and the compression may differ depending on port height.
PHANTOM EVOLUTION is offline   Reply With Quote
Old 12-12-2006, 12:31 PM   #10
Registered User
 
Country: Poland
Location: Warsaw

Join Date: Dec 2005
Location: Warsaw
Posts: 568
Thanks for your answers

Mike
__________________

Mike_G is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Powered by vBadvanced CMPS v3.2.3

All times are GMT +1. The time now is 08:02 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
×