[Fot] TR4 Race Engine Break-in Questions

[fubog1]

 The short version, rings flex.

	
	Piston pushes ring up, it's flat and against the lower face of the	groove. Gas pressure charge travels through the side gap on top past the upper face of the ring	and gets behind it right before TDC @ ignition point.
 At that point	the ring flexes and seals the top and lower faces of the ring	against the groove faces, and the charge is trapped behind the ring;	this is for pressure retention & max ring expansion. When the	piston starts to go down, the ring flexes back flat against the	upper groove face and loses the charge behind it and relaxes a bit.
	
Repeat this every combustion stroke.

	
	The above is with power on.

	
	On closed throttle (decell), there's a vacuum on top of the piston	so there is not a pressure charge to fully expand the ring, so it	doesn't flex the same.

	
	This flexing of the ring will give it a very very slightly ) face as	a result, it's not perfectly flat.

	
So ring seating isn't just to to get	the initial "burnishing" of ring/cylinder wall, it also	establishes the profile of the ring face for the best seal under	both full open and full closed throttle.
	
It's all in the ring FLEX!
	
This is also why ring side clearance	is so critical, I scrap more pistons for this being out of spec than	for any other reason, especially if the engine was running rich.

	

	
	My break-in routine is-

	
Initial start, run to temp, 1 maybe 2	heat cycles, retorque & check all.
	
	(If new cam, 15-20 minute @ 2k rpm)
	
No excessive running beyond cam	break-in and basic tuning with no load!

	
	On track, 2-3 warm-up laps @ part throttle, vary RPM 4-5k, use some	engine braking.

	
	2-3 more laps with more throttle and engine braking, same rpm.

2-3 more laps using full throttle, maybe 85-90% revs, and intentionalrepeated HEAVY engine braking from WOT in top gear.
After that I usually do a retorque andfollow-up; next time out should be good to go. 
This open/closed throttle runningsubjects the rings to the loads that it will have under normaloperation.
HTH
Glen


 

 

-----Original Message-----
From: Paul Ricco via Fot <fot at autox.team.net>
To: Friends of Triumph <fot at autox.team.net>
Sent: Sat, Aug 25, 2018 1:30 pm
Subject: [Fot] TR4 Race Engine Break-in Questions

FOT,Good afternoon and we hope everyone is having a great weekend.We have a couple questions for those who have had experience and success building TR4 race engines.  The information might be helpful others on the forum as well.1.  We have seen a few different recommendations for initial run-in.  They seem to range from 5 minutes to 20 minutes at approximately 2000 RPM’s.  How long and how many RPM’s are people running them  for?2.  How long are people leaving the break-in oil in the motor?	a.  Are people taking out the break in oil right after the run-in and replacing it with regular oil before leaving for the track?	b.  Are people running a few sessions under load at the track with it in and then switching?	c.  Something else?  If so, what are you having success with?Again, we are really gearing the questions towards race engines due to complication of breaking in the race motors at the track with limited time and the track session schedules.We are trying to avoid re-starting the entire referendum up on oil brands again, so we apologize if we do.  We are really trying to get to how people are breaking-in the TR4 motors successfully.Thank you for considering my questions,Paul Ricco_______________________________________________fot at autox.team.nethttp://www.fot-racing.comDonate: http://www.team.net/donate.htmlArchive: http://www.team.net/pipermail/fotUnsubscribe/Manage: http://autox.team.net/mailman/options/fot/fubog1@aol.com

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