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[Fot] TR4 Race Engine Break-in Questions

Subject: [Fot] TR4 Race Engine Break-in Questions
From: fubog1 at aol.com (fubog1)
Date: Sat, 25 Aug 2018 17:33:25 -0400
References: <CAA640A0-A574-463E-84F9-9CAFB52ED96D@att.net>

 
        
 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: 
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