58 replies to this topic

[stuboyle]

I've always felt that you could wring (not ring ) the hell out of motors in GPL with very little chance of them blowing it up.  There is no sense of rewarding drivers for keeping care of their equipment or penalizing those who were hard on their equipment.

Also, there seems a lack of randomness to the BHP your motor put out on any particular race.  There is no sense of "the boys back at the shop gave me a great motor today" or "power was off just a bit off today".

Seeing what Olaf Lehmann has done with engine power in his DirtgearPatch, got me thinking how it might be possible to better simulate how hard drivers ran their motors back in the day.

Any thoughts?

Edited by stuboyle, Apr 08 2021 - 08:55 AM.

[Pete Gaimari]

Have you run a full GP championship? It will show you how many DNF's there are. You'll also be one of them if you redline every shift.

Edited by Pete Gaimari, Apr 08 2021 - 08:53 AM.

[stuboyle]

Pete Gaimari, on Apr 08 2021 - 08:52 AM, said:

Have you run a full GP championship? It will show you how many DNF's there are. You'll also be one of them if you redline every shift.

No Pete.  A full 2 hour race is just too much for me.  My limit is about an hour, and that's pushing it.  With my limited knowledge of engine reliability from the 60's, I would not expect any motor to survive a 2 hour race with the driver hitting the redline on every shift or exceeding a certain RPM at then end of a straight.  I question if a motor could even make it half distance if you ran it that hard.  It seems that last few hundred RPM's were "emergency power" to use only if needed and you would be pressing your luck.

Edited by stuboyle, Apr 08 2021 - 09:29 AM.

[PTRACER]

Unreliability is modelled in GPL. Overheating causes you to lose oil or water, once the fluids drop too low your engine goes. Overrevving also damages it. It all sounds so very impressive but it's really just taking one number, like 1, and saying "If driver overrevs, reduce by 0.1 per second. At 0 the engine blows".

(Note: Simplified for simplicity's sake, may not be accurate)

[stuboyle]

PTRACER, on Apr 08 2021 - 09:39 AM, said:

Unreliability is modelled in GPL. Overheating causes you to lose oil or water, once the fluids drop too low your engine goes. Overrevving also damages it. It all sounds so very impressive but it's really just taking one number, like 1, and saying "If driver overrevs, reduce by 0.1 per second. At 0 the engine blows".

(Note: Simplified for simplicity's sake, may not be accurate)

I'm aware of that.  It's just a matter of degree.  It seems your can run it harder than you should be able to.

[Pete Gaimari]

The real cars didn't run novice, short, or long races. They just ran  long qualifying sessions and 2 hour races. Papy knew that and seemed to gear breakdowns for those races. I'm just guessing though. I know it's not unusual to lose over half the field in a GP race..

[stuboyle]

Pete Gaimari, on Apr 08 2021 - 10:50 AM, said:

The real cars didn't run novice, short, or long races. They just ran  long qualifying sessions and 2 hour races. Papy knew that and seemed to gear breakdowns for those races. I'm just guessing though. I know it's not unusual to lose over half the field in a GP race..

That's true.  By my calculation, a "long" race is still only 30% of full race distance.  Had they run the real races over only 30% distance, then ostensibly they could have run harder.

[Pete Gaimari]

I assume you run the Pro races?

[Robert Fleurke]

Apart from overheating, overrevving and speedshifting, there seems to be a random factor built in.

Sometimes engines blow while warming it up on the grid, sometimes they simply blow without any valid reason (no speedshifting, no overrevving), while some get away while overheating and speedshifting, even at Pro damage.

The mechanical damage model remains a bit of an enigma to me.

What would help me, is to find out the REAL redlines. Not the peak power revs, but the revs when the engine starts to get damage. I know some state that the peak power revs is the redline, but watching the powerband curves and redline dots in GPL Setup Manager makes me think differently.

Possibly Lee can add some valuable info by answering this question:

Does the end of the powerband curves in GPLSM (especially horsepower) mirror the redline, so does it correspond with the red dot (redline) in the lower graph (90% powerband), as I always used to think!?

Brabham (Repco) powergraphs attached. Max HP at 8200rpm. But the end of the curve is about 8700-8800rpm (estimated by scale), which corresponds with the red dot in the lower graph!? Rev limiter is even 9054rpm.

Attached Files

•  powergraph.jpg   73.27K   30 downloads

Edited by Robert Fleurke, Apr 08 2021 - 11:32 AM.

[paul_v]

Very interesting Robert.

This info about maximum sustained or safe revs as well as the revs which give max power or torque would be very useful.

I have asked this before.

[Robert Fleurke]

paul_v, on Apr 08 2021 - 11:55 AM, said:

Very interesting Robert.

This info about maximum sustained or safe revs as well as the revs which give max power or torque would be very useful.

I have asked this before.

The peak horsepower revs are shown in game at the car/team info. But again, in GPL Setup Manager the powerband curves/red dot (redline) show as more revs. Especially for the Repco. Each engine has it's own characteristic, and reliability, and thus has to be treated differently. For example with the Weslake you can't use much more revs than peak power revs...

For the Honda you better use less revs than peak HP revs (because of overheating), so it's better to shift at 11,000rpm than 11,300rpm, if you want to see the finish.

My main interest is original 67s.

Edited by Robert Fleurke, Apr 08 2021 - 12:14 PM.

[John Woods]

Have some vague memory of looking into definition of "redline" and recall it is an arbitrary limit engineers set with hope the driver will stay below that RPM and even more hope the engine won't blow up anyway, and it is not a result of applying a formula or rule that locks in a certain number.

It is the driver's job to not exceed whatever number the engineer's set.

Guessing, based on a lot of experience, GPL engine damage can happen at any RPM depending on variable conditions which are likely applied somewhere in GPL code, which implies maybe that while there might not be a real life absolute redline there must be one for each engine in GPL?

Awhile back someone asked when I shift and my reply was "just before the valves begin to float," which in retrospect seems about as virtually silly as it gets.

Might also explain why it seems so easy to blow an engine.

Edited by John Woods, Apr 08 2021 - 12:49 PM.

[PTRACER]

 Robert Fleurke, on Apr 08 2021 - 11:18 AM, said:

But the end of the curve is about 8700-8800rpm (estimated by scale)

Brabham redline is hardcoded to there yep. Only thing is, I don't know if damage occurs AT the red line or over it. When driving normally, GPL won't allow you to go over the specified limit, but driving over bumps at max RPM, shifting down too early, revving in neutral etc. does, and that should be where the damage occurs.

Edited by PTRACER, Apr 08 2021 - 01:02 PM.

[Pete Gaimari]

Shifting down too early in the Lotus seems to do the most damage. It will record a higher rpm than we can get accelerating. I usually upshift the Lotus around 8500 for a GP race. I'll go to 9000 for just qualifying. I'll downshift real late in the race.

It's my understanding and observation that damage accumulates. You can over-rev the engines many times before it blows and sometimes will finally blow when you're doing nothing wrong. Maybe some of that is random but it could be your mistakes made earlier.

[Robert Fleurke]

PTRACER, on Apr 08 2021 - 12:44 PM, said:

Brabham redline is hardcoded to there yep. Only thing is, I don't know if damage occurs AT the red line or over it. When driving normally, GPL won't allow you to go over the specified limit, but driving over bumps in the road at max RPM, shifting down too early, revving in neutral etc. allows you to go over it.

Cheers Paul. Indeed, but the weird thing is last 2 oAo races I did never reach the redline, despite bumps and my agressive downshifting (possibly once at the start tho), I have checked this with GPLRA, and also didn't have speedshifts in the laps that I checked. (I checked all laps last race).

I did notice you use less revs than me, but also there are guys who use more revs than me (like Enrique/Tristan). Still at a loss why I had a header failure at Sebring 64 and a camshaft failure at Goodwood 65, after years of not having blown up the super reliable Repco...

Edited by Robert Fleurke, Apr 08 2021 - 01:15 PM.

[John Woods]

A few weeks ago sat in the pits in the Lotus 49 with car in neutral. floored throttle and held it down thinking at some point, probably quickly, the car would overheat and blow up.

This was in response to a chat discussion about overheating.

Didn't happen until temp got up over 340F, which took a few/several minutes, (which was very painful to listen to btw).

[Robert Fleurke]

Pete Gaimari, on Apr 08 2021 - 01:04 PM, said:

Shifting down too early in the Lotus seems to do the most damage. It will record a higher rpm than we can get accelerating. I usually upshift the Lotus around 8500 for a GP race. I'll go to 9000 for just qualifying. I'll downshift real late in the race.

It's my understanding and observation that damage accumulates. You can over-rev the engines many times before it blows and sometimes will finally blow when you're doing nothing wrong. Maybe some of that is random but it could be your mistakes made earlier.

The Cosworth DFA is a very sensitive engine for overrevving, and mostly overheating. I use my own numbers out of experience as a guideline, combined with GPLSM graphs, and GPL Team info. As I said, I do approach each 67 engine differently due to it's characteristics.

The BRM you can run fairly hot, hotter than any other engine. Engine heat is related to the amount of revs. But compared to the Honda it's much more reliable, even when I had a few blow ups last seasons in GELI. I have to push the BRM to the boundaries to be able to fight for podiums as well.

I do agree especially with the second paragraph Pete, That said, it's hard to explain why  engines blow when warming up the engine on the grid, or on your outlap (which happened to me as well), while never coming close to redline etc.

Therefore there must be also a random factor built in...

[TvO]

I once had a UKGPL race at Sebring, where the concrete slabs on the runway create considerable bumps. Wonderfully modelled by Ginetto. Anyway, I was running in the back in the BRM but was up into the top 5 because one after the other blew their engine on the bumpy straights. I was one of the last to go, but the rough nature of the track was hard on the car for sure.

Also, once I was running an offline race at Zandvoort in the BRM as well when suddenly a wheel fell off on the straight after the Hugenholtzbocht! I later had it happen in a 1965 online race at Oulton Park Fosters as well on the main straight.

So mechanical problems do happen, especially in Pro / GP damage level races. But usually I stuff it in the wall before it happens.

Tommie

Edited by TvO, Apr 08 2021 - 03:11 PM.

[Pete Gaimari]

Another thing I do is with gearing and i'm sure most of you know this. For qualifying I gear for the longest straight to redline at the end of the track. For the race I gear much higher is case I catch a draft which can over-rev the engine.

I was just thinking about that bumpy track and a higher gearing would have helped keep the rpm under redline.

[Lee200]

Robert Fleurke, on Apr 08 2021 - 11:18 AM, said:

Does the end of the powerband curves in GPLSM (especially horsepower) mirror the redline, so does it correspond with the red dot (redline) in the lower graph (90% powerband), as I always used to think!?

Brabham (Repco) powergraphs attached. Max HP at 8200rpm. But the end of the curve is about 8700-8800rpm (estimated by scale), which corresponds with the red dot in the lower graph!? Rev limiter is even 9054rpm.

Rob, the red dot in the lower graph is the maximum rpm which is about 8700 for the Braby BT24.  GPL has a rev limiter that begins to cut power as maximum rpm is approached.  It's not all that precise however, and overrun by few hundred rpm usually occurs as you noted.

The curves in the upper graph are the ranges for 90% of the maximum horsepower and torque.  The 90% horsepower curve extends all the way to maximum rpm.