Biggest Car Engines

[BTB 500]

Yep.....and a tuned two stoke pipes job is to try and use the pulses to keep the mixture in the bore rather than going straight out of the exhaust....so it stops loses rather than gaining anything......which they don't do a great job at which is why they are high polluting and thirsty and (without any variable porting YPVS type trickery) pretty peaky too as the exhaust pulses only work within a narrow rev range..

We're only talking about power output here, not considering pollution / fuel consumption.

I've never used a 2-stroke bike but I flew r/c aircraft fitted with tuned pipes for many years. These produced more power with a pipe fitted than with an open exhaust (and a lot more than fitted with a simple can silencer). Pipes can certainly be designed to be 'peaky' and only work at a certain rpm, but these are essentially unusable in all bar highly specialised applications (e.g. racing aircraft that run continuously at full throttle only produce full power in the air as the prop unloads and rpm increases to the working range of the pipe). Normally though you'd use a pipe with a much softer/broader rpm range which might give a little less power boost at full bore but would be beneficial at lower ranges too.

Expansion chamber - Wikipedia

en.wikipedia.org

 

[BTB 500]

Not until a pump with moving parts is added can it be called FI.

IMO forcing fuel/air mixture into the combustion chamber before compression is providing forced induction, whether that's achieved via a mechanical supercharger or a reflected pressure wave from a tuned pipe. But as they say in the US, YMMV

 

[Mactech]

What naturally aspirated road going engine made the most power from its displacement ie, specific power output?
To get the ball rolling. consider the Aprilia RS250 motorcycle. 55hp from 250cc. 440hp/litre. Is there a road going NA engine that beats that?

Don't suppose you can guess what my track day weapon of choice was quarter of a century ago then?



Oh yes! It had a power band about the same width as the needle on the tacho....

 

[BTB 500]

Pipes can certainly be designed to be 'peaky' and only work at a certain rpm, but these are essentially unusable in all bar highly specialised applications (e.g. racing aircraft that run continuously at full throttle only produce full power in the air as the prop unloads and rpm increases to the working range of the pipe).

Just for fun here's a very old video of a control line speed model with just such an exhaust system. It takes over 10 seconds from takeoff to accelerate to the point where the engine comes 'on pipe' at about 55 secs in, giving a huge jump in power. This setup gives the absolute maximum power but would be useless for any normal application

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[Bellow]

FWIW, a tuned 2T pipe first creates a negative pulse which pulls fresh charge into and through the cylinder. A cylinder's volume can pass through to the exhaust. Then, a positive pulse rams all that almost lost charge back into the cylinder immediately prior to exhaust port closing. On a very highly tuned engine, that returned positive pulse - as it sees the closing exhaust port as a dead end - will bounce back into the pipe, do the whole traverse of the pipe's length again and return to the exhaust port (still positive) and rebound off the piston just before port opening and when the port does open and a fresh pulse emerges, the two pulses in essence combine and create stronger ensuing pulses.
When operating thus in their zone they can be very fuel efficient. It's at off-design point it falls apart. The need for fuel enrichment to cool intrudes but does so on 4T also when used to supress detonation.

 

[Doodle]

To get the ball rolling. consider the Aprilia RS250 motorcycle. 55hp from 250cc. 440hp/litre. Is there a road going NA engine that beats that?

Cut said motor in half. The Rotax 125s in the Aprilia RS (et al) were 33-34hp in full fat mode.

 

[BTB 500]

Last off-topic excursion, I promise

I used 'soft' tuned pipes in r/c aerobatics (where you're using the throttle a lot), and slightly more peaky ones in pylon racing (where you're not). I only raced in an 'entry level' class where the engines had to have full throttle control, but the international FAI F3D class uses un-throttled engines (there's just a fuel cutoff valve) with much more peaky pipes that only 'come on' in the air. These are faster but very critical to set up ... it's normal to adjust the compression (via shims under the cylinder head) and prop pitch to suit the weather conditions (temperature/pressure/humidity), even between flights. I preferred to just fill the tank and fly Example of an FAI F3D heat:

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[Mactech]

Cut said motor in half. The Rotax 125s in the Aprilia RS (et al) were 33-34hp in full fat mode.

Ah! But the Honda RS125 production race bike was 46bhp....and the most fun I've had on 2 wheels. This is Paddock at Brands



It was my son's race bike, but as I'd paid for it and built it, it was only fair I should test it....

 

[Bellow]

Ah! But the Honda RS125 production race bike was 46bhp....and the most fun I've had on 2 wheels. This is Paddock at Brands

View attachment 151702

It was my son's race bike, but as I'd paid for it and built it, it was only fair I should test it....

You beat me too it. 125cc motocrossers back in the 1980s were making 45hp. IIRC 500 GP bikes made 220hp so 440hp/litre (880hp/litre as measured in the manner of 4Ts).
So, 2Ts can be as small as 1cc (I have one) or as big as the ones powering the largest ocean going ships (where torque in lbs.ft is in seven figure territory) and anything in-between. The Crecy and Nomad would have killed 4T in aviation had the jet engine not done so. (The jet/gas turbine killed 4T but not 2T. It merely stopped further 2T development). Yet, they still aren't taken seriously - despite all they can offer.
Anyway enough thread diversion - the possibility of a road going 2T car engine is likely on a par with another 12.8litre engine emerging.

 

[Doodle]

Ah! But the Honda RS125 production race bike was 46bhp....and the most fun I've had on 2 wheels. This is Paddock at Brands

Not exactly road going though

On the subject of 500GPs, many summers of youth were misspent in the company of one of these; Krauser 500 in an LCR chassis, campaigned by a family friend.

.

You'd swear it was actively planning to murder you at any given moment.

 

[ALFAitalia]

Anyway....sort of back on topic....which NA car makes the best power litre for litre???

The Ferrari 458 Speciale: makes 132.7 hp/litre......pretty good for a larger lump at 4.5L.....not quite at the 166 in the T.50.....but more of a full production car.

 

[Doodle]

I suspect Gordon Murray's T50 must be up there, given that it revs to about 10 million?

 

[ALFAitalia]

Yep....thats the 166 per L mentioned in the post above.
Revs equal power.
But torque is what you feel when you put your foot down. Nothing more tiring to drive than a car that needs revving all the time, I took in a Type R Civic in Px years ago....used it for the weekend......great fun!.......for about 20 minutes....tedious after that. Give me big CCs or medium CCs with high low rev boost any day. High revving cars should be on the track.

A power curve should not look like this (Stock VTec Civic)....look at that nasty hole in the torque, right middle of the revs where you need it.



That's what a torque and power dyno chart should look like on a road car.....virtually flat and full torque from 2 to 5 thousand rpm....IMO...of course.



One reason Im not so keen on the M156 is lack of low torque and how quickly it falls away.....a 6.2 should not need to be revved like that to make torque......but thats why it makes a successful track weapon. Horses for courses.

 

[ALFAitalia]

Not exactly road going though

On the subject of 500GPs, many summers of youth were misspent in the company of one of these; Krauser 500 in an LCR chassis, campaigned by a family friend.

.

You'd swear it was actively planning to murder you at any given moment.

Gotta love those hydraulically formed spannies!!! CRACKLE CRACKLE CRACKLE!

 

[BTB 500]

So, 2Ts can be as small as 1cc (I have one)

Smallest I had was 0.16 CC (0.010 CI). Very practical little engine - flew a couple of small r/c models very nicely. No throttle though - full power till it ran out of fuel. We had a racing class for the 0.33 cc version (0.020 CI) which we flew indoors at Olympia (4-up heats) when the Model Engineer Exhibition was held there in the '90s.

I still have a couple of 0.55 CC diesels, which are throttled and silenced. Beautiful little engines with excellent throttle response. They were the only IC things I kept when I went all electric in 2005.

 

[BTB 500]

I suspect Gordon Murray's T50 must be up there, given that it revs to about 10 million?

See post #8 !

 

[StMarks]

What naturally aspirated road going engine made the most power from its displacement ie, specific power output?
To get the ball rolling. consider the Aprilia RS250 motorcycle. 55hp from 250cc. 440hp/litre. Is there a road going NA engine that beats that?

Don't suppose you can guess what my track day weapon of choice was quarter of a century ago then?

.

Fwiw amongst my stable I still have a 1996 (the Matt Silver finish one) Rs250 with only 8k miles under it's belt.

 

[Bellow]

Smallest I had was 0.16 CC (0.010 CI). Very practical little engine - flew a couple of small r/c models very nicely. No throttle though - full power till it ran out of fuel. We had a racing class for the 0.33 cc version (0.020 CI) which we flew indoors at Olympia (4-up heats) when the Model Engineer Exhibition was held there in the '90s.

When I wrote ''1cc'' I was aware there were smaller engines - but not that small!

I still have a couple of 0.55 CC diesels, which are throttled and silenced. Beautiful little engines with excellent throttle response. They were the only IC things I kept when I went all electric in 2005.

This got my attention. Diesel (HCCI to be more precise) with a throttle I've never heard of - didn't believe it possible. I was under the impression that if a throttle was required, glow plug was the way to go. Anything you can add here? Eg, any special fuel requirements, as throttle responsive as glow motors, any set-up peculiarities re compression adjustment etc, etc?

 

[BTB 500]

This got my attention. Diesel (HCCI to be more precise) with a throttle I've never heard of - didn't believe it possible. I was under the impression that if a throttle was required, glow plug was the way to go. Anything you can add here? Eg, any special fuel requirements, as throttle responsive as glow motors, any set-up peculiarities re compression adjustment etc, etc?

The American Cox company made a lot of small glow engines but the TD .010 (CI) was the tiniest. They actually did a limited edition with it mounted on a tie pin! The glow element was incorporated into the cylinder head rather than being a separate plug.

My technique with small diesels (I had a pair of throttled/silenced 1.5 cc ones as well) was to start them on full throttle without changing the compression. Left alone they'd stop after a second or less, but you could 'catch' it by momentarily choking the carb with a finger over the air intake. This way you could keep it running in longer and longer blips until it was warmed up and running normally. Then you could throttle back. The 'official' technique is to increase the compression for cold starts then back it off again as the engine warms up, but getting it back to exactly the same position is a bit hit and miss. The engine temperature changes in flight so what sounds right on the ground can become over (or more likely under) compressed in the air. I used a standard commercial fuel - Model Technics D1000:

MSL Model Technics D1000 1 Litre Diesel Fuel (Version 2) MT-D1000-1L-V2, Model Shop Leeds

The throttle response was excellent. I used to compete in 'fun fly' competitions and in the limbo event (where you had to make as many passes between two poles and under a tape as possible in a minute) I figured that a very small model would have a significant advantage. So I designed this lightweight model for a 1.49 cc diesel and comprehensively thrashed everyone with it Unfortunately for the following year they banned 'micro models' on the basis that they were unfair?!





In a lineup with a couple of other models I was flying at a display in the 80s:



(the one in the middle was powered by an .80 (13 cc) 4 stroke with a belt-driven drum valve in the cylinder head)

This was my first prototype which flew very well until a head-on mid air collision!





P.A.W. are probably the best known current manufacturer of diesels, ranging from the .55s I have up to a 10 cc version:

Engines

 

[Bellow]

Thanks BTB 500 - appreciated.
My interest is in HCCI and where it exists at larger scale, torque control is usually with constant airflow and varying the fuel strength (technically quality governed) - which with a 2T is wasteful as the excess air is at a cost. What I've seen today is HCCI torque control by quantity governing which is what I want to explore.
I have a DC Spitfire which I'm considering experimenting with if my direction of travel is compatible with it. I don't have its prop though. From memory it ran with a 6 x 4 prop (6'' diameter, 4''/rotation pitch?). Does that sound right? If so, given that it will be static, is there a better prop choice (to load the motor)? I doubt that the Spitfire will be throttled but I have aThunder Tiger 20 glow motor that I'm thinking of converting to HCCI and would use it for throttling experiments. I've been told a suitable prop for it with RC is a 10 x 6. I've also read that glow motors converted to diesel require different props. Which direction re diameter and pitch and again, it being static?