Spitfire Mk.XIV/e issues

[SupremeLoser]

I have found that the Spitfire Mk.XIV and Spitfire Mk.XIVe, the Griffon engine models, seem to be very prone to engine damage.  I'm watching the engine oil and coolant temps and they are fine, but if I run in emergency power for just a few minutes the engine is damaged, even on 150 octane.  For example, I can run the engine at say in the 15-18psi range (engine can run 21psi) on 150 octane, for a short while (about 2-3 minutes tops... not a full 5 minutes) and the engine is damaged.  Yet, the older Merlin Spitfires (the Spitfire Mk.IXc and Spitfire Mk.IXe), the engine can be run at max all out power settings and pull at least 5 minutes without engine damage.  Also, the Griffon Spitfires are a bit more of a handful, particularly at high altitudes.  They seem to want to fishtail and scrub speed very easily at 20000+ ft for example.

 

As a result of all of this, the Spitfire Mk.IXc is my favorite as it seems to handle the best and also that Merlin engine seems to be more robust.

 

However, my question is the modelling accurate?  I have read that the Griffon Spitfires were indeed not as good handling as the lighter Merlin engine variants.  The older and lighter Spitfires yet handled even better.  That seems correctly modelled, however, what I am unsure about is that high altitude fishtailing behavior of the Griffon Spitfires in particular.  They really can scrub speed off in a hurry and then are very vulnerable even to an older Bf 109 G-6.

 

I haven't found info regarding the Griffon engine being more or less fragile than the Merlin engine.  They were both very similar engines... in fact, the Griffon engine was a development/improvement over the Merlin in pretty much every way.  The only thing would be to watch out for the cooling as more hp = more btu to shed.  But, in flying it in IL-2, the cooling temps can be managed fine.  It is just that it seems to damage very easily even if oil/coolant temps are in normal range.

 

Thoughts?  Can the developers have another look at the engine damage model for the Spitfire?

Edited May 16, 2024 by Spitfire_Enthusiast1

[AEthelraedUnraed]

3 hours ago, Spitfire_Enthusiast1 said:

I haven't found info regarding the Griffon engine being more or less fragile than the Merlin engine.  They were both very similar engines... in fact, the Griffon engine was a development/improvement over the Merlin in pretty much every way.  The only thing would be to watch out for the cooling as more hp = more btu to shed.  But, in flying it in IL-2, the cooling temps can be managed fine.  It is just that it seems to damage very easily even if oil/coolant temps are in normal range.

More power also means more stress on the various components, so it doesn't sound altogether strange to me that a very similar engine with more power would be more fragile

 

However, it's almost universally agreed that the current "engine timer" system isn't very realistic (although opinions differ on how to solve the issue). The way IL2 works is that you've got a certain number of minutes of guaranteed failure-free operations at certain engine settings (go above these and this amount of time will decrease). Once you get past this (as well as a randomly determined "grace period"), the engine is "damaged" which *will* eventually lead to a complete engine failure. These engine timers are usually based on the maximum times given in period documentation (e.g. flight manuals). Of course in reality, getting past these time limits does in no way guarantee engine damage, and engine damage does in no way guarantee a complete failure. But it is what it is; it may be unrealistic but I don't think we're going to see a different system in this series. Perhaps Korea, but not in the current IL2.

 

4 hours ago, Spitfire_Enthusiast1 said:

Thoughts?  Can the developers have another look at the engine damage model for the Spitfire?

As I said, the engine timers are usually based on the official maximum time limits according to period documentation. If you have such documentation (i.e. official documents, no anecdotes) that show that different time limits were both tested and in active use, then you can post them here and *maybe* the Devs will have a second look at it (it has happened before).

 

If you don't have any data showing the current engine timers are wrong, then very likely the answer is no

[the_emperor]

International power (up to 1 hour): 2600 RPM, boost +9
Emergency Max All Out power (up to 5 minutes): 2750 RPM, boost +18
Is what you should be able to get from your engine minimum.

you should be able to increase your time at max boost by decreasing rpms (though historically and simulationwise a big mistake…but you can exploit that in the game). 

[SupremeLoser]

I understand that the current engine sim revolves around timers and I am fine with that.  Not perfectly accurate, but I can understand getting to another level of detail modeling engine reliability and damage at different power settings would be something in the next version of this simulation.  And besides, the time is the function listed to match up with the engine power settings info for each plane.  I went ahead and made cards in place of the picture that states the engine power settings for each plane for easy reference.  If it says I can run 2750rpm at 21psi for 5 minutes, I expect that.  At least in this simplified engine timer model.

 

Regarding more power on the same/similar engine making it less reliable at the higher power level, that would be true if no other improvements were made to the engine to handle that power.  However, they did make the engine improvements that dealt with handling the added load on the engine.  This can be seen empirically that a number of the same engine family went through numerous revisions, the Merlin for example, where the power by the end of the war was nearly double that of at the beginning of the war and yet there are few reports that the engines were blowing up early in the later war.  Also, though a lot of the power came from increased boost from higher octane, it also came from improvements in how the engine ran... often the supercharger design itself to allow more efficiency at higher boost/altitudes thereby netting substantial power gains (two stage vs single stage superchargers, different superchargers altogether, better flowing inlets and exhaust, etc.).  Also, bear in mind, the reason the Griffon engine made more power than the Merlin was it was a larger displacement engine.  So it wasn't being stressed more.  The Merlin engine was 1649cid compared to 2240cid of the Griffon.  To give an example:

 

Spitfire Mk.IXc

Merlin 66

1649cid

Maximum power in Emergency Max All Out mode (3000 RPM, boost +18, low gear) at 5750 feet: 1705 HP

1705hp/1649cid= 1.03 hp/cid

 

Spitfire Mk.XIV

Griffon 65

2240cid

Maximum power in Emergency Max All Out mode (2750 RPM, boost +18, low gear) at 2134 m: 2063 HP

2063hp/2240cid = .92 hp/cid

 

I picked the situation where the engine is making the highest rated hp.  These are settings and altitudes I run often in combat.  As you can see, the Merlin actually has a higher specific output.  Yet, I can run that engine no problem for the rated 5 minutes at emergency power setting.  This is not the case for the Griffon engine.  I just would like things to be consistent with their ratings listed.

 

The importance of the engine power you can reliably run for a given duration is critical in combat.  I probably don't have to tell you guys that the difference in 100hp can be the difference between life and death.  One particular situation where you need sustained high power settings is in doing sustained circles when following and trying to get your guns on the enemy.  Even if you aircraft can outturn it running full power, that doesn't happen if you have to reduce the power and then the enemy can actually outturn you and pull away gradually and get on your tail.  There are workarounds sure, but why not simply have the engine performance accurate and consistent across all of the aircraft?  This would mean the aircraft combat simulation would be more realistic with how the planes actually flew.

 

Also, one note about octane.  150 octane does more than simply allow higher max boost at the same power setting.  It effects the entire operation of the engine curve.  In other words, in a Griffon engine that can make 21psi on 150octane vs 18psi on 100octane, it would improve the reliability and duration settings for all of the other power settings too.  This is because the higher octane provides a much higher detonation threshold, a killer of boosted engines (and a big reason why they fail if you sustain the engine at higher power settings for too long).  So, if for example I can run 2600rpm and 12psi for 15minutes on 100 octane fuel, I would expect being able to run higher boost at the same rpm for the same time on 150 octane fuel.  Probably about 2600rpm and 15psi for 15 minutes.  Likewise, if I run the same 2600rpm and 12psi on 150 octane fuel instead of 100 octane, I would expect I could run it longer on 150 octane without damage... say 30 minutes vs 15 minutes.

 

So, in short, al of the engine power settings manifold pressure/boost would go up when going to higher octane fuel... not just the max power setting, but cruise, international, combat, etc.

Edited May 16, 2024 by Spitfire_Enthusiast1

[the_emperor]

dont  you get longer time till damage when keeping the throttle at 18lbs instead of 21? I thought so. 

the problem is, in reality you couldnt manipulate the throttle past combat/climb setting as we do in percentage increments, since the throttles were usualy gated at that  setting and you would insteantly go to full WEP if you "break the wire". 

so having a predetermined setting for all out WEP and not letting us tinker with that, would probably reflect reality better of course coupled with a bit more relaxed timer self destruct sequences.  

 

 

Edited May 16, 2024 by the_emperor

[SupremeLoser]

Thanks for the replies guys.  Well, I went ahead and did some measured tests and I stand corrected.  Here are the results:

 

Spitfire Mk.IXc

Merlin 66 - 150 octane

Observed Maximum Power Engine Failure Time:

1000ft 335ias 3000rpm 25psi : 6m 30s

5000ft 327ias 3000rpm 22psi : 7m 20s

 

Spitfire Mk.XIV

Griffon 65 - Rounded Exhaust Pipes - 150 octane

Observed Maximum Power Engine Failure Time:

1000ft 350ias 2750rpm 21psi : 6m 0s

5000ft 350ias 2750rpm 21psi : 6m 40s

 

So.... the failure times look reasonably close to matching the engine power settings specs listed for these planes, which is 5 minutes. I'll take 6m and some change!  I suppose this is an example of where perception does not correspond to reality.  The reality is the Griffon engine fails only slightly earlier than the Merlin in the test above.  Close enough.  I can accept that perhaps the Griffon engine was slightly more fragile in operation at full power.  And by that we are only talking about 30-40s difference.  I perceived it was failing much sooner than that.  It could be that in combat it was more sensitive to lower air speeds and higher oil and coolant temps.  I do notice the Griffon Spitfire does seem to run hotter than the Merlin.  That part does make sense actually.  Significantly more hp in the same airframe with very similar sized cooling radiators and locations.

 

I also took another look at the indicated power setting in technochat vs the listed specs on both 100 octane and 150 octane.  The max continuous and max combat power settings are not effected by the octane.  On second thought with my prior comments on this note, I actually now think this is correct.  The higher octane will only increase the maximum power setting... no effect on the maximum settings for cruise and combat.  Why?  Because there is no detonation limit with octane at those lower power settings.  It is only at the limit that the threshold is moved higher with the higher octane.

 

So, in short, looks good :).  I just will leave this info up for any others that want to understand it better.

Edited May 16, 2024 by Spitfire_Enthusiast1

[ShamrockOneFive]

Upvoting this and commenting that THIS is the sort of resolution I love to see. Something comes up, you test it, find out if perception matches reality or not and go from there. Well done!

[FeuerFliegen]

One other thing I wanted to add that can affect engine timers- if you increase the throttle too quickly, the RPMs will rise quicker than the constant speed prop is able to change positions and will rev higher than what your RPM is set to; so in the case of the Spitfire Mk XIV, based on my testing - depending on what your throttle is at, if you push it to 100% then you might rev it as high as 3050.  In my case I only got 4 minutes of emergency power until I got the technochat message that the time had been used up, after pushing it a few times from low manifold pressure and revving it from anywhere from 2950-3050rpm.

[Sayan]

On 5/16/2024 at 9:53 AM, Spitfire_Enthusiast1 said:

For example, I can run the engine at say in the 15-18psi range (engine can run 21psi) on 150 octane, for a short while (about 2-3 minutes tops... not a full 5 minutes) and the engine is damaged.

  2-3 minutes ???

Kuban, spring, Spitfire Mk.XIV and XIVe. Altitude 5000 feet
Emergency power 2750 RPM, boost +18,   2...3...4 minutes, normal flight, after 5 minutes warning about exceeding the limit.
I keep the same mode for another 30 seconds, then switch to the continuous mode 2400 RPM, boost +7, and manually open the radiators.
My Spitfire is flying!
It's the same story using 150 octane gasoline boost +21 

4 test flights.
Spitfire is the best!
Sincerely.

 

Edited May 20, 2024 by Sayan

[SupremeLoser]

Hi Sayan, please read my post down a little further.  In it, I documented actual tests I just ran and I basically had to eat crow  .  As you mentioned I found I could run Emergency Power for about 6 minutes. 

 

Also, that is true that you can gain back time by running at cruise/continuous settings for a bit and then put her back at full throttle!  I use this often in extended combat.  The key is to take advantage of any time you have when you are sufficiently away from other planes and especially have altitude on them.  That is an opportunity to give the engine a break for a minute or two.

Edited May 23, 2024 by Spitfire_Enthusiast1