Have you seen? 2

[lugnuts67]

I had been contemplating the limiting factor for the modern internal combustion engine and came to the conclusion that it is the valve design. Then I started to sketch out a rotating barstock system with ports cut into it and looked around on the net for similar ideas.

Has anyone else looked at the Coates engine (

http://www.coatesengine.com)?

It looks quite promising but they are not producing for the public - especially my old Pontiac.

 

[NickE]

Ive always heard that sealing the exhaust ports was the difficulty, exhaust gas in a modern ICE is ~1600F+ and In my turbocharged 2.0L its up to 1700F.

Few sealing materials would work and allow the rotating bar to continue to rotate.

Also variable valve timing would go away, until the ports and passages could be designed to change geometry w/ RPM.

 

[turbocohen]

The limiting factor is thermochemical.. flame speed.

 

[automotivebreath]

"The limiting factor is thermochemical.. flame speed"

I must agree, and the solution is in cylinder turbulence, early transition to turbulent flame with the resulting flame intensity. This combined with modern combustion chamber designs will produce minimal burn durations resulting in less negative work and little heat loss to the piston and head.

 

[patprimmer]

coats engine has been thrashed to death in previous threads.

A search may throw up a lot of discussion.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[lugnuts67]

Thanks patprimmer. There were several good points there both pro and con. What I did not see mentioned though was the ceramic-composite bearings and sealing surface. I too have some reliability concerns about a 14,500rpm small block Ford because of rotating mass but the lubrication would definitely be there seeing as the only lubricated parts are in the bottom end.
I know that it seems too good to be true but there must be some plausibility to the design - he has secured a contract on large truck engines and is selling them on bikes. Maybe the pros are overstated and the cons understated but I would like to see one myself or maybe just an independent test.
Don't get me wrong, I am not sold on it but am intrigued.

 

[globi5]

What do you understand under limiting factor? Power density or efficiency? Gasturbines do not need valves at all and have high power densities, however don't reach efficiency levels of diesel piston engines with poppet valves. So I guess you're talking about power density since replacing poppet valves with a less restrictive valving mechanism would mainly promote flow and thus possibly increase power density (if there aren't any sealing issues).
But then again turbocharged engines can generate plenty of power with poppet valves: Here's a video of a 'family sedan' with a turbocharged 2.0 l engine that only needs 8.95 seconds on a 1/4" mile.

http://media.putfile.com/Worlds-Fastest-EVO-8-Buschur-Racing

(Not sure about power levels of this engine, but it might be over 1000 hp. Is this not sufficient?).

 

[NickE]

globi5 -- the mitsu, Lancer-EVO is a far cry from a family sedan.

(And thats what can be doen by consumers, In WRC trim these 2.0l 4-cyl turbo motors are making ~600ft-lbs at 1500rpm and by 7000rpm are HP restricted by a 34mm (or thereabouts) restrictor plate to limit them to 300hp.)

With pneumatic poppets or e-mag poppets dont F1 motors rev to like 16,000 rpm?

I just have to agree that poppet valves are not the limiting factor here. Possibly the limiting factor is the basic design of the SBC?


Nick
I love materials science!

 

[turbocohen]

Flame speed is the #1 limiting factor in F1.

 

[globi5]

Actually I wouldn't be too sure about flame speed in F1. If it was flame speed then F1 wouldn't be this short stroked, since the shorter the stroke the longer the flame has to travel (very wide and flat combustion chamber). So at least in this case I would argue that piston speed is one of the limiting factors.

NickE, regarding the family sedan: Well, you have to admit that it has 4 doors and a trunk.

 

[globi5]

Hasn't F1 already reached 20,000 rpm?

 

[patprimmer]

There is quite possibly more than one limiting factor. The parameters to optimise each might be in conflict and a compromise is used so that the overall optimum is achieved, ie a bore and stroke where piston speed and flame travel limits hit the engine simultaneously.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Greenlight]

F1 engineers did testing a few years ago to "try" and determine the limiting factor in an F1 type IC engine.

The information that did "leak out" is that they stopped the testing at 31,000 rpms. I have not seen any other details of the testing made public.

 

[globi5]

Keep in mind F1 engines are quite limited as well. If I remember correctly they're only allowed to use metals and/or materials with a limited modulus of elasticity (and density) and of course are only allowed to use 8 cylinders.
E.g. no carbon fiber rods or ceramic valves.
Also a high bore / stroke ratio leads to a combustion chamber with a large surface area where gases can cool down more rapidly and thus hurt torque.

 

[globi5]

Not quite on topic, but since we're at it: It's a pity that F1 engines are this regulated. They should only limit fuel and maybe displacement and allow any positive displacement engines including wankel engines. This way they only need to be powerful but efficient as well.
Of course this would increase the possibility that one team finds an engine concept that is far superior as far as power density and efficiency goes. But to slow down a faster team they could simply add weight (as done in other race series).
This way our daily drivers might eventually benefit from these developments as well.

It is also interesting to see, that F1 teams of today consume 10 or 100 times more resources to develop a race car than 40 years ago. A race car, which for regulatory reasons is far less innovative than some of the race cars developed in the past.

 

[MikeHalloran]

The limiting factor for development of any technology is

...

money.



Mike Halloran
Pembroke Pines, FL, USA

 

[globi5]

Lotus had an F1 car with a gasturbine running 1970 or at least around then. I don't know what the exact budget was back then but I believe it was less than a tenth of what an F1 one team has now.
It is only a question of where you set your priorities. If innovation goes up, predictability and reliability will go down. So what? An F1 car is not an airliner, instead of 1 smoking engine we would simply see 10 per race. I just don't believe that people would stop watching it, simply because there are more smoking engines.

F1 is supposed to high risk and action. However, F1 regulations start to generate a higher predictability level than regulations of a retirement home.
And I don't say they should reduce safety, I just say they should allow more innovation particulary in the engine department where it might help generating more efficient engines after all.

 

[GregLocock]

Just out of idle curiousity, when was the last time that a concept that was invented in racing made its way onto production road cars?


The cars are more expensive now because there is more money available. A racing team will always spend 105% of its budget.


Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[globi5]

Entirely new ideas hardly come from racing applications anyway, but experience, useful data and promotion of a new technology did come from racing. For instance from the turbo-charger era or from the semi automatic gearbox development.
Now you can argue that the turbo-charger was invented 1905, but it didn't start to become widely popular on road cars before it was extensively applied in racing.

This huge F1 budget is now used to do a lot of detail work, for instance to work on the various little fins to guide air on a particular part of a chassis, which is generation of data that has mainly value for this particular chassis but very little for anything else, sometimes not even for the next years chassis.
Also, I'm mainly critizing F1. Not all racing series are like this, as Audi showed with its first Diesel powered race car winning LeMans.

 

[GregLocock]

On the latter point, the rules were jigged to favour the diesel.

Yes, I'd allow the turbo and possibly sporting 4wd, as succesful transplants from racing into road cars. That was what, 30 years ago? Since then nothing of any interest.

Motor racing is primarily a business, not a Petri dish for experimentation.







Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.