Exhaust Gas Temperature QSB 6.7

[Quitsa]

I note from the specification sheet that the EGT at the turbo outlet for my QSB 6.7 550s is 970F.  When running at my normal “easy” cruise of 2600 rpms and around 50% load, I see an EGT reading of about 660F.  Is this telling me anything apart from it being very unlikely that the engine is overloaded?  The EGT does not seem to change a whole lot unless running at displacement speed.  It never gets up near the 970 reading even at WOT, though I have never stayed at WOT for more than 30 seconds.

I never had EGT sensors before so I have no idea of what to expect.

Topic

[Quitsa]

Thanks Tony.  I did map the actual fuel curve against the published Cummins curve back when testing props.  I am within 5% from planing speed on up to WOT, being slightly above at the lower end and slightly below from 2600 approaching WOT of 3360, where I see about 95%. 

By the way, the Cummins folks are still unable to diagnose the source of the knocking noise I asked about a few weeks ago.  They tried plugging the injectors one at a time and also disconnected the fuel rail solenoid and there was no real change in the noise.  What is odd is that the noise goes away when the gear is engaged.  That might indicate the coupling was the source, however, the frequency of the noise is about 300 rpms, not the 600 rpm idle.  Since there is nothing turning in the reverse gear at 300 when it is in neutral, that would seem to rule out the coupler, which would be rotating at the engine idle speed of 600 rpms.

[Tony Athens]

Your EGT numbers are right in line with what we see when everything is RIGHT for this engine.. Use these numbers as your “all is right” baseline for future reference..

 If you really wanted to “see” your engine loading, graph your GPH against the “factory propeller” curve at all rpm’s from 2000 up to 3000  ( cruise RPM’s) .. 

Tony

 

 

 

 

Tony

[Author]

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