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Unread 19 January 16, 19:47   #1
SidW
 
Join Date: Dec 2015
Default GT40 rev limit\engine failure

I haven't yet been able to complete a full lap ( including out lap ) of Le Mans in the JWA GT40 without the engine blowing up.
At first I thought I was over revving the engine when the car took off over the Mulsanne hump, but that turned out not to be the case.
I know how rev limiters work, and that they only protect the engine from the drivers right foot by limiting the spark, not from badly timed downshifts or incorrect gear selections - but this seems to be caused by running flat out for extended periods of time, like you would do at Le Mans.

Would anyone like to give this a go, just to confirm I haven't been really unlucky, or I am doing something else wrong ?
The track is VLM 77 if you want to make sure that taking off over the hump isn't the problem, but I guess 67 Spa would be another candidate where you spend most of your time flat out in top.
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Unread 19 January 16, 20:36   #2
David Wright
 
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Join Date: Jun 2006
Location: UK
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The red zone on the rev-counter is there for a reason

I think you've made an error with your gearing for Le Mans. The only way I can reproduce the engine blowing up in a lap is to run constantly on the limiter. If you do this your engine will only last for around 30-50 seconds.

When running at Le Mans you must choose the highest final drive - 10/32. The engine produces peak power at 6.500 rpm. To achieve the best speed on the Mulsanne you need to reach maximum speed at these revs. Selecting 10/32 will give you the highest maximum speed and you won't blow the engine.

If you change gear at between 6500 and 7000 rpm you should be fine.

Information on revs at peak power can be found in the showroom. There is also a manual for the GT40 and Porcshe 906 which goes into a bit more detail.

http://www.nogripracing.com/forum/sh...d.php?t=351571

http://www.nogripracing.com/forum/sh...d.php?t=351991

In reality, the GT40 didn't have a rev-limiter. In producing the physics for P&G I had three options

1) set the rev limit at a speed the engine can sustain indefinitely
2) set the limit at a speed the engine can sustain for short periods
3) set the limit above the speed the engine can sustain so you have no protection at all - like the real engine.

I opted for 2) as the default. You can break the engine by sustained abuse but have some protection.
I have given the option of 3) - you can raise the rev limit in set-up screen so you have no protection.

Last edited by David Wright; 19 January 16 at 20:50.
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Unread 19 January 16, 21:04   #3
Dominiek
 
Join Date: Apr 2009
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I was just about to post something similar, albeit less knowledgeable and less eloquent. The worst I could do to the engine with the appropriate gearing (10/32 indeed) was a 17% increase in damage over ten laps and that required very aggressive downshifting in a style I'd never use for real in this gem.
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Unread 19 January 16, 21:14   #4
SidW
 
Join Date: Dec 2015
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I'll stop driving using " HUD in cockpit " mode then, so I can see the needle on the rev counter instead of just the HUD shift light...
I really should have known the GT40 didn't have a rev limiter, lord knows I've read 'Racing In The Rain' enough times...

Good decision on the engine I reckon, it'll make endurance racing more interesting and realistic.
I'll now edit the "LifetimeEngineRPM" value in the GT40 eng files back to it's intended value

Edit :- It wasn't " HUD in Cockpit " that was removing all the needles from the dials - what on earth have I done wrong ?

Edit edit :- Forget the above, had " Visible MOTEC " turned off

Last edited by SidW; 19 January 16 at 21:37.
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Unread 19 January 16, 22:11   #5
dragob
 
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Join Date: Jan 2008
Location: Bulgaria
Age: 39
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Yeah, I have read that Ford engineers forbid the drivers to use first gear even in the slowest corners at Le mans so as not overrev the engine ("Go like Hell" book.)
btw the GT40 is 10 times more fun to drive now that P&G 3.2 has been released.
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