Now, to get higher displacement, I've heard of boring out and changing the "stroke." What I do not know is how this works.

Which is more effective for increasing torque and which will limit your revving? Just from logic, I've deduced that stroking will lower revs and de-stroking will translate into higher revs..is this correct?

Basically then, I'm asking for the lowdown = the outline of the above misconceptions/cloudy concepts I have...

The reasons for getting a higher displacement in our case are related to higher torque correct? List what else if I am missing the point please!

Now: what are the advantages to a higher revving engine? (the B18c engines have lower displacement/ higher revving engines than the H22a's)?

Also, is it then possible to make a high-revving high displacement (high torque) engine? What would have to be done here...?

any help here is appreciated...

Note: Obviously i am referring to our import engines here...so none of them are actually HIGH displacement..but you get the picture..

 

Actually, your ability to Rev is based on your Rod Length to Stroke Length Ratio.

An Example: the B16a has a r\s ratio of 1.74:1

So the rod is 1.74mm for every 1mm of stroke. This is almost optimal...Optimal is 1.75:1, this gives you the broadest torque curve and the highest rev range. rpm kills motors though, especially when you have significant sidewall loading from having a bad r\s ratio. The Piston get 'pushed' against the sidewall and distorts your honing.

1.75:1 is not Optimal for creating torque, but will give you a higher horsepower because Horsepower = Torque * RPM\ 5252. The higher you can rev with a given torque = higher horsepower. Conversely, you don't want to make all of your power @ 7000rpm, because most people never rev that high on the street.

Anyways, Im getting tired of typing...someone else elaborate.

Suprdave

 

how about more friction, heaver bigger parts are harder and less safe to move fast. hehe

 

this has the potential to be a really good thread here...

so is the output (general design of power curve) of a motor going to be determined by the bore and stroke of a motor?

there's an interesting tech article at http://www.turbomagazine.com/archive...201_tech02.jsp that relates to this topic quite well....

 

7000 rpms I think would be considered low for a honda engine....I'm doing a built B20 and I'll probably only go to 7000 rpms, where as all the other B-Series (other than LS engines) do 8000-8500 + rpm's.

 

Bore x Stroke does not determine the Power Curve. Bore x Stroke determines the Displacement, which determines the Torque (In very Simple Terms)

The Ability to rev that Torque, determines your horsepower.

You power curve is dictated by your Rod Length \ Stroke, also throwing in varibables such as Fuel, Compression, Head Porting, Cams, etc....

The Ability to Rev Correlates with the Piston Speed which is also related to the Thermal efficiency of the motor.

EXAMPLE: The longer the piston dwells @ TDC the more efficient the Burn is. This will also help with pulling more air into the cylinders.

With a Short Rod setup, the piston does not dwell toward TDC long enough to complete the burn and doesn't breath well enough.

Chime in, anyone...

Suprdave

 

So given the somewhat small displacement of our engines, what would be the best way to make the maximum amount of torque?

As I've read, torque determines the actual power, while horsepower dictates how fast you go.

 

The best way to maxamize torque in a 4 cylinder is thru forced induction. Although I would like to see a honda motor with a big bore, and small stroke. It is too bad all the b series engines are designed the reverse of this. Long stroke, small bore. Oh, the b16a stroke is pretty small...but so is the bore.

An all motor setup on a 4 cylinder can be fast, but you will allways have to rev the crap out of the motor. FI will give you a more usuable powerband.

Thus my reason for deciding to go turbo.

Oh, I was checking the specs on a 4g63 turbo motor....the R/S ratio is 1.74 also I believe.

 

sleave and bore.....I would think that you would want to maintain a r/s of 1.74:1 IE a B16 and the sleave and bore the 16 to ohhh lets say 84mm....now you have lower end power. BUT....compair prices of doing this as apposed to adding a turbo....hmmmm, also depends on where you live (smog relations).

 

That's true, but if you build your engine for turbo correctly, you will end up having to sleeve it anyway...

But I assume based on what HX said, the best way to get more torque is to increase the displacement while maintaining a r/s 1.74:1..right? What determines that "perfect" ratio?

 

fully built crvtec would give you the best of both worlds...hi revving engine with torque up the ying yang...
you will need a vtec head with all the goodies... (cams,sprockets,head work, bullet proof valve train etc....) all the stuff you need for a built head.
as for the block youll need a b20 block with aftermarket rods and pistons with a z10 girdle with Vtec oil and water pumps. with this setup you should net some good numbers.

 

excellent thread kidz....

how can building up a motor be done to insure that you'll still pass emissions? won't altering the physical dynamics of the motor itself alter its emissions?

 

Like I said, B16 + sleave + bore = same as above only cheaper.

 

It takes more than just torque to make power. Give me a lever long and strong enough, and I'll make you 1,000,000lb-ft of torque.

The thing with power is that by definition, it is force x velociy, or in our case torque x rpm. So if I was actually moving that lever against the 1,000,000lb-ft, then I'd be making power. If no movement is happening, there is no power.

In the end power dictates how fast you accelerate. You can have a motor making little torque, but if it's revving really fast it can still make power. You can then use a gearbox to convert the rpm's into usable torque at the wheels.

 

in general, torque and horsepower can be described in the following terms:

torque affects acceleration
horsepower dictates top speed

take these definitions rather loosely though...

 

short and simple

 

short, simple, and wrong.

No offense.

The torque curve dictates how fast you accelerate at all points in the rpm band. Combined with gearing & drag, and you can find top speed.

Horsepower is simply a number derived from torque & rpm, which gives you an idea of where you make the most torque, and consequently how well your car can take advantage of shorter gearing. A peak horsepower number represents nothing more than roughly where you make the most torque.

In an applied setting where gear ratios are fixed, like in dyno tuning, horsepower numbers are mostly irrelevant.

As far as passing emissions with a bored or stroked engine, it usually comes down to fuel tuning. A stock ECU isn't going to have enough flexibility to deal with the larger capacities of the engine.

A cheap way to solve this is with an FPR (fuel pressure riser), which adds more fuel without the ECU knowing about it. But in many cases, in order to get enough fuel at all points in the rpm band, you'll be running rich in others . . . . consequently failing emissions.

But using a good comprehensive fuel-tuning method (hondata or other standalone), the engine should be able to run as clean or cleaner than stock. Note however, that wild NA cams represent a whole other problem, as lots of overlap (time when the intake & exhaust valves are open together) means lots of pollution.

And I'm not sure a bored, stroked, & sleeved B16 would be any cheaper than a CRVTEC. Sure, B16's are cheap & there's fewer parts to acquire, but that's a lot of machining & labor to be done. But I've never researched and summed the costs for each approach, so I could be wrong.

 

well, of course you're correct... but that's why i said take these definitions loosely. of course there are many other factors that affect torque... but horsepower is a function of torque over time (or RPM), just as speed is a function of acceleration over time... and just as you had mentioned, there are indeed drag factors which limit your speed (drag is an opposing force), gear ratio factors, et cetera...

 

Again

 

Maybe I'm nitpicking, but even taken loosely, it's incorrect. Horsepower does not dictate top speed. There may be a positive correlation between the two, but correlation doesn't imply causation in this case.

Just another internet myth I'm tired of seeing propogated. That and that whole "small engines need backpressure" crap.


[Modified by Daemione, 2:32 PM 11/14/2001]

 

That's also wrong, no offense.

I can guarantee that an engine with a perfectly flat torque curve but a steep horsepower curve will not accelerate the same throughout the entire rpm range.

My b16 doesn't have much more torque at the top end than at the low end. Hell, it doens't have that much more torque than a d16. Yet it accelerates MUCH, MUCH faster at the top end. It's acceleration follows its power curve.

When people say an engine has lots of torque, what they really mean it that it has power at low rpm.

Torque x rpm = power
If the rpms are low then you need the torque, but the result is power.

If you put a 1000lb-ft@1000 rpm motor in a car,
and a 100lb-ft@10000 rpm motor in another car,
and you give them both proper transmissions, they will both accelerate at the same rate (all else being equal).

 

Cheapest way to increase torque noticeably is increase compression. Milling the deck is relatively cheap compared to boring/stroking.

Not that I would recommend it. Gives you problems of it's own.

 

I don't believe this is accurate. 150 ft/lbs. of torque will pull exactly the same at 8,000 rpms as it does at 3,000.

A B16 with a flat torque curve (a well-tuned JRSC will give you this - around 135 ft/lbs. across the board) in 3rd gear will take the same amount of time to go from 30-50 mph as it does to go from 50-70 (ignoring drag).

 

I'm saying the exact opposite of you, and I'm sticking to it. It's useless to argue any more though. I think we need a thrid party to call this one, preferrably of the engineering type.

 

Agreed. I looked into this a month or so ago, as I wasn't sure myself. What I determined from a couple different sources was my current point of view.

I'll see if I can dig up some previous discussions.