Big bore short stroke

[clenfers]

Why has no one made a big bore short stroke engine like this,
5 inch bore and 2.5 inch stroke V8 or prefer a V12. Although a V8 is cheaper on mass production and (V12 due to more cylinders making for a smoother engine) also use long rods and thin piston rings.

This would rev high, and due to the large piston surface area make up for the torque of a short stroke as well as less ring friction, plus unshroud the valves.

Also equip this with Coates rotary valve heads for 10-15K rpm, he was trying to sell this design to the big 3 but they already had to much invested in the old ancient poppet valves.

If only I had a few million dollars lying around for R&D I could set capitalism aside and make something special for the masses

 

[shatner saves]

A V8 with a 5 inch bore and 2.5 inch stroke would probably have a useable rev range of about 1000 rpm (ie: no low end torque). Even with the rotaty valves you described, the rev potential of a motor like that would be severely limited because of the sheer weight of the pistons and piston speeds. The current average value for piston speeds right now is around 4500 ft/min (the '03 honda S2000 is at 4761.2 ft/min. Your engine would have an average piston speed of 6250 ft/min at 15,000 RPM. The engine, at around 393 cu. in., would also be big, with the bore spacing required to accomodate 5" pistons.

 

[clenfers]

World products has engine blocks with massive bores (4.625 bore and 5.850 stroke I guess they must just explode) and huge strokes so it can be done. Also the surface area of a piston makes up for a short stroke, sure less crank leverage but more flame front.
Also coates took a t bird 302 ( low tech) up briefly to around 14K rpm what i suggest is a engine built for it. Also it didnt have to be 5 inch bore exactly.
This 5.85 stroke at 5k rpm has a speed of 4875 ft/min.
Just checked the chevy 632 inch (4.6 bore and 4.750 stroke) for sale at many places such as Bill Mitchells wich had peak power at 7600 rpm had a piston speed of 6017 ft/min with this 4.750 stroke

 

[Dutch]

The problem with large bore engines is that at high RPMs, the flame front can't advance fast enough to cover the entire piston top. With pump fuel and a normal RPM range (up to maybe 7000), the maximum practical bore size is about 4.5 inches. WHen you start getting into radical fuels, I believe that changes the equation significantly.

 

[SVTdriver]

World products has engine blocks with massive bores (4.625 bore and 5.850 stroke I guess they must just explode) and huge strokes so it can be done. Also the surface area of a piston makes up for a short stroke, sure less crank leverage but more flame front.
Also coates took a t bird 302 ( low tech) up briefly to around 14K rpm what i suggest is a engine built for it. Also it didnt have to be 5 inch bore exactly.
This 5.85 stroke at 5k rpm has a speed of 4875 ft/min.
Just checked the chevy 632 inch (4.6 bore and 4.750 stroke) for sale at many places such as Bill Mitchells which had peak power at 7600 rpm had a piston speed of 6017 ft/min with this 4.750 stroke

You have to realize that engines you are comparing your engine to. Have significantly larger strokes. The Bill Mitchells one had nearly twice. And the world products had better than twice the length.

 

[shatner saves]

World products has engine blocks with massive bores (4.625 bore and 5.850 stroke I guess they must just explode) and huge strokes so it can be done. Also the surface area of a piston makes up for a short stroke, sure less crank leverage but more flame front.
Also coates took a t bird 302 ( low tech) up briefly to around 14K rpm what i suggest is a engine built for it. Also it didnt have to be 5 inch bore exactly.
This 5.85 stroke at 5k rpm has a speed of 4875 ft/min.
Just checked the chevy 632 inch (4.6 bore and 4.750 stroke) for sale at many places such as Bill Mitchells wich had peak power at 7600 rpm had a piston speed of 6017 ft/min with this 4.750 stroke

The question I have, for both engines, is how long will they live? Production engine durability requirements are a lot more severe than you would see in a Hi Po crate motor and probably a lot more than Coates ever tested that suped up t-bird engine to. a 632 cu in crate motor that see's regular trips to 7600 rpm is probably going to get torn down a lot more often than ypur typical high output production engine.

Even still, you can't get over the inherent low end torque disadvantage that such an oversquare engine design would have.

 

[clenfers]

Long rod, short stroke, big piston would live longer than a normal engine, the entire point is you can have your cake and eat it too, as far as flame front simple answer 2 spark plugs per cylinder to cover half the distance. Its an enginering fact that 2 engines with *(identical displacement)* will have similar torque it doesnt matter if it is a long stroke vs short stroke due to piston surface area.
I do realize they had more stroke that is the whole point its called ( reciprocating mass) wiht a short stroke the effective mass that ripping the rods apart isnt created till really high rpm.
And before you question cotes valves longevity go to his website and check out what they are installing them on, Electric utilities wouldnt use it if it was crap.
Dont you guys have desk top dyno, check it for yourselves same identical displacement = almost identical torque. I realize this is a ford site but there was a article about the 350 chevy should have built it takes all this into account and it makes for a badass engine. All im trying to do is question why we keep getting truck engines and not High po specific designed engines for the top of the line models.
By the way the 632 chevys are available for the street (on pump gas and will eat a 04 modified Cobras lunch), the tunnel vision around here is bad, we must know the enemy so as to choose are battles wisely. Of course this is all insignificant as in a few years all our cars will be gas hybrids (check out the new Ford Escape hybrid with its atkins cycle ) except for our track toys. Here is a article about the different 383's explaining my whole point THANK YOUhttp://www.hotrod.com/techarticles/0304_381/index2.html

 

[SVTdriver]

You do realize then how much it would cost a manufacturer to design a specific high performance engine for the mustang? A truck engine can be tuned for a car. A lot cheaper than a new design. Would it be nice if they designed an engine for every SE? Sure. Would it be realistic or practical? Not a chance.

 

[351CJ]

By the way the 632 chevys are available for the street (on pump gas and will eat a 04 modified Cobras lunch), the tunnel vision around here is bad,

And does that 632 Chevy meet 2005 ULEV-II emissions requirements as well as EPA MPG requirements to avoid the gas guzzler tax?

 

[shatner saves]

Long rod, short stroke, big piston would live longer than a normal engine, the entire point is you can have your cake and eat it too, as far as flame front simple answer 2 spark plugs per cylinder to cover half the distance. Its an enginering fact that 2 engines with *(identical displacement)* will have similar torque it doesnt matter if it is a long stroke vs short stroke due to piston surface area.

So you are using cylinder pressure to make up for the short stroke. If I were a mass producing an engine like that, by first question would be "How much fuel is this thing going to chug at low RPM?"

I do realize they had more stroke that is the whole point its called ( reciprocating mass) wiht a short stroke the effective mass that ripping the rods apart isnt created till really high rpm.
And before you question cotes valves longevity go to his website and check out what they are installing them on, Electric utilities wouldnt use it if it was crap.
Dont you guys have desk top dyno, check it for yourselves same identical displacement = almost identical torque. I realize this is a ford site but there was a article about the 350 chevy should have built it takes all this into account and it makes for a badass engine. All im trying to do is question why we keep getting truck engines and not High po specific designed engines for the top of the line models.
By the way the 632 chevys are available for the street (on pump gas and will eat a 04 modified Cobras lunch), the tunnel vision around here is bad, we must know the enemy so as to choose are battles wisely. Of course this is all insignificant as in a few years all our cars will be gas hybrids (check out the new Ford Escape hybrid with its atkins cycle ) except for our track toys. Here is a article about the different 383's explaining my whole point THANK YOUhttp://www.hotrod.com/techarticles/0304_381/index2.html

I'm not saying the Coates design is bad. Quite the contrary. Iv'e been a fan of that technology for years. However, considering he hasn't been able to successfully sell any of the auto manufacuters on it, especially with current concerns about fuel economy, I have to think that maybe if was lacking in some way.

The big bore, short stroke, long rod engine design you describe WOULD BE MASSIVE, with or without rotary valves. Forgetting anything else, that would be enough for auto manufacuters to walk away from it.

That Bill Mitchell engine you keep referring to costs $15,000, and doesn't even make an attempt at being EPA or CARB legal.

 

[clenfers]

It would be no more massive than the current big blocks available.
A friend of mine read my posts and asked why i was being so hard on Ford, this was not my intention I have had several mustangs and loved all of them however my favorite had a 302 in it big bore short stroke Relatively speaking all it was missing was the windsor deck height for longer rods.
As for Cobras I almost bought a left over 03 model its a great design for what they had to work with. I got an 03 GT instead and I love it just like my 01 GT I had.
Also the 632 if assembled by your self would come in less than $15K probably half that much, a new Cobra engine from Ford is not cheap either and the dollar per HP aint that great. Add in fuel injection and the ability to shut down cylinders (which we will start seeing soon in new models) and the emmisions and milage of a 632 would be quite good. Chevrolet is going to be implementing this on there 496 Truck big blocks that are in production, put a Whipple on one of these things and you would have a monster. When I said big bore it wasnt set in stone that it had to be 5 inches or even 4 inches that was just an example, take our current model V10 it would make an excellent candidate like the 351 V-10 they made and take it down to 5 liters and throw in some longer rods. And for those of you who didnt know longer rods allow higher compression with pump gas due to effective piston dwell time in relation to crankshaft degrees of rotation, not mention the more effective use of dynamic cylinder pressure in regards to crankshaft degrees of rotation.

 

[SVTdriver]

Yes maybe assembling the 632 yourself you could save 1/2 the money MAYBE. But you could likely save just as much buy building the Cobra motor yourself. And there are Cobra motors with a KB blower running some pretty freakin high hp numbers. Cobra motors complete are running $12k. But that 632 is $15k and still missing a few items.

 

[shatner saves]

It would be no more massive than the current big blocks available.
A friend of mine read my posts and asked why i was being so hard on Ford, this was not my intention I have had several mustangs and loved all of them however my favorite had a 302 in it big bore short stroke Relatively speaking all it was missing was the windsor deck height for longer rods.
As for Cobras I almost bought a left over 03 model its a great design for what they had to work with. I got an 03 GT instead and I love it just like my 01 GT I had.
Also the 632 if assembled by your self would come in less than $15K probably half that much, a new Cobra engine from Ford is not cheap either and the dollar per HP aint that great. Add in fuel injection and the ability to shut down cylinders (which we will start seeing soon in new models) and the emmisions and milage of a 632 would be quite good. Chevrolet is going to be implementing this on there 496 Truck big blocks that are in production, put a Whipple on one of these things and you would have a monster. When I said big bore it wasnt set in stone that it had to be 5 inches or even 4 inches that was just an example, take our current model V10 it would make an excellent candidate like the 351 V-10 they made and take it down to 5 liters and throw in some longer rods. And for those of you who didnt know longer rods allow higher compression with pump gas due to effective piston dwell time in relation to crankshaft degrees of rotation, not mention the more effective use of dynamic cylinder pressure in regards to crankshaft degrees of rotation.

Light truck emissions and fuel economy requirements are a lot different from passenger cars.

Answer me this: why is it that with all the auto manufacturers from different cultures all over the world, there are no production automobile engines that even come close to the 2:1 oversquare condition you are suggesting? Even the current Yamaha R1, at a bore/stoke of 77 mm x 53.6 mm doesn't even come close to that.

The engine would still be big. Comparing it to the 2005 mustang 4.6L, with a slightly overquare bore/stoke of 3.55 x 3.54, your engine would be at least 5.8 inches longer. That's only if (big IF) you could get away with using the same wall thicknesses and water jackets while swinging those 5" pistons. You could do a 5.8 liter v10 with the 4.6's bore/stroke and it still wouldn't be as long.

Trust me, someone has thought of this before, and decided against it.

 

[clenfers]

You can get a big block with 4.600 bore and 10.2 deck height, combine this with a 3 inch stroke and 6.535 rod readily available (as are 6.800's) and you would still have a compression height of 2.165 piston, this would be a 398cubic inch engine . You can also get deck heights up to 11.625.

Here are some rod ratios for ya http://www.racewindsor.com/performancepartsplus/ratio_table.html
Here is the article about the engine they should have built http://www.purplesagetradingpost.com/sumner/techinfo/350 chevy engine.html
Also given the beefy parts in the big block its ability to withstand more power from a durability stand point compared to our Cobra SC 4.6 are hard to ignore.
And as for engine bay clearance we have seen V-10s put into the Mustang and some 460's.

 

[SVTdriver]

You can get a big block with 4.600 bore and 10.2 deck height, combine this with a 3 inch stroke and 6.535 rod readily available (as are 6.800's) and you would still have a compression height of 2.165 piston, this would be a 398cubic inch engine . You can also get deck heights up to 11.625.

Here are some rod ratios for ya http://www.racewindsor.com/performancepartsplus/ratio_table.html
Here is the article about the engine they should have built http://www.purplesagetradingpost.com/sumner/techinfo/350 chevy engine.html
Also given the beefy parts in the big block its ability to withstand more power from a durability stand point compared to our Cobra SC 4.6 are hard to ignore.
And as for engine bay clearance we have seen V-10s put into the Mustang and some 460's.

You do realize that is a chevy motor right? Ford is not going to build a chevy motor anytime soon.

 

[clenfers]

Yes I realize its a Chevy motor thats not the point, Im talking engine theory as it applies to all engines. These same things can be applied towards current aftermarket engines as well as future engines.
I see lots of pot shots at my and various rescources information. However I am waiting for someone to present some facts that they have researched cause Im getting tired of having to keep disproving statements others have made IE piston speeds and engine dimensions rod ratios and the exsistance of various mythological parts. Run a 302 Ford aginst a 305 chevy on your desktop dyno with the only difference (this means same heads, valve sizes, and cam and compression) being in the bore stroke and you will see they have near identical bottom ends with the 302 laying the smack down at higher rpms yet both are 5 liters! Further examples can be seen in Ferrari and Lambo engines power/torque ratings versus displacment is quite high due to understanding the enginering for true performance efficiencies instead of the big 3's good enough for mass production designs.

 

[shatner saves]

So, essentially, you wan't ford to put a big block in the next mustang (GT?).

Keep reaching for that rainbow.

P.S. You couldn't buy a motor for a ferrari or Lambo for the cost of a complete mustang. It'd be cool if it had a motor like that, but it would be even cooler if I could afford that car sometime before I'm dead.

 

[clenfers]

It all depends on what you consider a big block to actually be, and no I dont expect Ford to put it in the next mustang but would appreciate it if they applied more Advanced Theory to our engines such as they are doing with Duratec's. Dont get me wrong of the Big 3, Ford has been leading the way in engine tech, Im just whinning for more despite their financial gain.

The original reason for this thread was I was in hopes of a particular reason why they didnt carry the 302 bore and stroke over, or a little more oversquare design into the modulars.

This will be my last post on this subject as Im sure everyone is tired of listening to me and my hot air as this is a Forum for the 05's.
Sorry to have bothered my fellow Mustang brothers.

 

[bigal51]

good post, Got some smart peeps here.

 

[80deathtrap]

Oversquare engines have bad heat transfer characteristics when compared to square and undersquare engines. This is because they have a larger surface area for a given displacement. This means they lose alot more of the energy released from the fuel. It also means more friction. I like oversquare engines. And I would prefer to work with them. But there are obvious disadvantages when it comes to economy issues.