Home Mobile Forum News Cookbook FaceBook Us T-Shirts etc.: Europe/Worldwide. eBay Motorsport Links Advertising Live Chat  
Site Partners: SpotterGuides  
Related Sites: Your Link Here  

Go Back   TenTenths Motorsport Forum > Racing Talk > Racing Technology


Reply
 
Thread Tools Display Modes
Old 9 Mar 2012, 17:45 (Ref:3037603)   #1
dtype38
Race Official
Veteran
 
dtype38's Avatar
 
Join Date: May 2004
England
East London
Posts: 2,479
dtype38 has a real shot at the podium!dtype38 has a real shot at the podium!dtype38 has a real shot at the podium!dtype38 has a real shot at the podium!
Combustion chamber carbon build-up : an odd pattern?

Due to the demise of a thrust bearing I had to change the crank on my race engine this week. It's a full strip-down job as the head has to come off to get the timing chain off the crank. No biggy, but when I looked at the chambers and pistons the carbon pattern wasn't anything I'd seen before. Now I've run this engine for years and it likes to run rich (like 5% CO rich - its just the way it wants it!) so when I take the head off I usually expect to find 6 black cambers and 6 black pistons. But last time I rebuilt it I put some different pistons in and this time they weren't all black. The chambers are, but I've never seen completely clean sections of piston before. Anybody know if its something I should be concerned about?
Attached Thumbnails
Piston01.jpg   Piston02.jpg  
dtype38 is offline  
__________________
New direction, new start..... life begins again!
Quote
Old 9 Mar 2012, 19:27 (Ref:3037643)   #2
GORDON STREETER
Veteran
 
GORDON STREETER's Avatar
 
Join Date: Nov 2006
Spain
Kent+Mojacar Spain, but not always ?
Posts: 7,645
GORDON STREETER is going for a new lap record!GORDON STREETER is going for a new lap record!GORDON STREETER is going for a new lap record!GORDON STREETER is going for a new lap record!GORDON STREETER is going for a new lap record!GORDON STREETER is going for a new lap record!
It normally means oil contamination during combustion IMHO
GORDON STREETER is offline  
__________________
Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa !
Quote
Old 9 Mar 2012, 21:05 (Ref:3037693)   #3
VIVA GT
Subscriber
Veteran
 
VIVA GT's Avatar
 
Join Date: Apr 2005
England
Leicestershire
Posts: 3,511
VIVA GT has a real shot at the championship!VIVA GT has a real shot at the championship!VIVA GT has a real shot at the championship!VIVA GT has a real shot at the championship!VIVA GT has a real shot at the championship!VIVA GT has a real shot at the championship!
In my experience this is usually the early stages of detonation! (But you've been lucky, it's only taken the carbon, and not the aluminium of the piston or the head. Some may say that this shows you've got it all spot on, just on the right side of serious detonation...
VIVA GT is online now  
__________________
Incognito: An Italian phrase meaning Nice Gearchange!
Quote
Old 9 Mar 2012, 22:39 (Ref:3037734)   #4
graham bahr
Veteran
 
graham bahr's Avatar
 
Join Date: Jan 2003
England
cambs
Posts: 2,071
graham bahr should be qualifying in the top 10 on the gridgraham bahr should be qualifying in the top 10 on the grid
are the pistons slightly taller than the old ones? if you run really tight sqwish clearances you get sections of the head/piston where no combustion takes place, when i pull race pintos and m10 bmw engines i've built ( 0.030" swish) apart they always have clean bits on the piston where the piston comes close to the head/valves
graham bahr is offline  
__________________
AKA Guru

its not speed thats dangerous, just the sudden lack of it!
Quote
Old 9 Mar 2012, 22:52 (Ref:3037740)   #5
dtype38
Race Official
Veteran
 
dtype38's Avatar
 
Join Date: May 2004
England
East London
Posts: 2,479
dtype38 has a real shot at the podium!dtype38 has a real shot at the podium!dtype38 has a real shot at the podium!dtype38 has a real shot at the podium!
I'd be surprised if it was oil contamination as its only done four or five hours running since a bore hone and new rings. Having said that, Venolia do specify very large piston clearances so it's possible.

Detonation wise, I'm actually running more conservatively on this set of pistons, down from 10.8:1 to 10.5:1 and backed off from 34deg max advance to 32deg. There hasn't been any hint of pinking so I'm hoping that isn't an issue.

Indeed the piston crowns are a lot taller than the old ones (although not the height at the edges) but being a lazy arse I couldn't be bothered to take them all out and machine the tops off so I just fitted a thicker gasket. This has kept the compression ratio similar, but ironically its massively increased the squish around the edge from the 30" I'd normally use way up to something like 120".
dtype38 is offline  
__________________
New direction, new start..... life begins again!
Quote
Reply

Bookmarks




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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Carbon/Carbon Racing clutch JJ68 Racing Technology 2 22 Jan 2011 13:02
Expansion of combustion Mackmot Racing Technology 9 7 Feb 2005 03:06
Bizarre pattern.... Knowlesy Announcements and Feedback 2 7 Dec 2004 21:26


Powered by vBadvanced CMPS v3.2.3

All times are GMT. The time now is 12:04.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Original Website Copyright © 1998-2003 Craig Antil. All Rights Reserved.
Ten-Tenths Motorsport Forums Copyright © 2004-2018 Royalridge Computing. All Rights Reserved.