[vina]

Originally Posted by Sutripta

OK. Not much of an internet guy, so I'll rattle of a few terms and you can do your own searching.
Mushroom and Tangential cams. Geneva mechanisms.
Valve overlap. Relation to powerbands.
Advantage of OHC to pushrod implementations. (Maybe even an debate of this Re: V8s)
DOHC vs SOHC.
Slightly OT - dual springs, pneumatic springs, beehive springs. Desmodromic setups.

Regards
Sutripta

PS. Gosh. This is the worst case of jargon dropping I've seen in a long time.

Jargon is fun . I'll search and find the stuff and write to you for any queries.

[aaggoswami]

Very interesting discussion, which I believe is not coming out to a conclusoin.

Lets consider this :
K10B Wagon R.
Bore X Stroke : 73 X 79.5

F10D Wagon R.
Bore X Stroke : 68.5 X 72

Still the F10D had much better torque at bottom end as compared to K10B. I can vouch for this as my uncle has F10D waggie and we have K10B. In traffic, its quite easy to drive F10D as compared to K10B. Both my father and me ended up stalling K10B waggie as we are used to high bottom end of F8 in our M800 ( which is 1 lakh kms. + ).

Lets consider this pulling from dead slow speeds in our M800 and Waggie. After the usual nasty bumps, even with 3 passengers, the M800 on CNG will pull cleanly in second. K10 Waggie even with one person will not. First is required in our Waggie.

Similar story is applicable while comparing even F8D Alto with K10B waggie.

Its a rather crude example, but enough to give view about the power characteristics.

Ofcourse, at higher rpms, K10B waggie eats F10D waggie.

Baleno and Ikon.
Ikon details are already posted and hence not repeating again.
But Baleno
Bore X Stroke : 75 X 90
power is almost equal to Ikon.

But still Ikon had more available torque at lower end. No doubt, Baleno was high geared, but in city driving, the higher available torque of Ikon was visible. Once rpm climb, Baleno becomes strong and remains so till around 6500 rpm.

IMO, state of tune matter a lot here.

[vina]

Originally Posted by aaggoswami

Very interesting discussion, which I believe is not coming out to a conclusoin.

Lets consider this :
K10B Wagon R.
Bore X Stroke : 73 X 79.5

F10D Wagon R.
Bore X Stroke : 68.5 X 72

Still the F10D had much better torque at bottom end as compared to K10B. I can vouch for this as my uncle has F10D waggie and we have K10B. In traffic, its quite easy to drive F10D as compared to K10B. Both my father and me ended up stalling K10B waggie as we are used to high bottom end of F8 in our M800 ( which is 1 lakh kms. + ).

Lets consider this pulling from dead slow speeds in our M800 and Waggie. After the usual nasty bumps, even with 3 passengers, the M800 on CNG will pull cleanly in second. K10 Waggie even with one person will not. First is required in our Waggie.

Similar story is applicable while comparing even F8D Alto with K10B waggie.

Its a rather crude example, but enough to give view about the power characteristics.

Ofcourse, at higher rpms, K10B waggie eats F10D waggie.

Baleno and Ikon.
Ikon details are already posted and hence not repeating again.
But Baleno
Bore X Stroke : 75 X 90
power is almost equal to Ikon.

But still Ikon had more available torque at lower end. No doubt, Baleno was high geared, but in city driving, the higher available torque of Ikon was visible. Once rpm climb, Baleno becomes strong and remains so till around 6500 rpm.

IMO, state of tune matter a lot here.

I'm sorry, but I don't follow what is your point here. You have put a lot of information so it is hard to tell.

Also are we sure that gear-ratio etc. are not playing a role here? Torque at the engine shaft is not the same thing as torque at the wheels.

Also are you sure about dimensions of the k10B engine - both your bore and stroke numbers are larger than those for F10 engine, even though the F10 is known to have higher displacement

[dhanushs]

Originally Posted by vina

Also are we sure that gear-ratio etc. are not playing a role here? Torque at the engine shaft is not the same thing as torque at the wheels.

+1.

The difference between Grande Punto 1.3 and Swift DDiS 1.3. AFAIK, both sport same engines, in same state of tune.

Originally Posted by vina

Also are you sure about dimensions of the k10B engine - both your bore and stroke numbers are larger than those for F10 engine, even though the F10 is known to have higher displacement

Vina, IIRC,the Indian F10 is 1L and and the K10B is 1.1?. Or opposite?

[Mpower]

Originally Posted by pranavt

The CBR has roller rockers, which is why I talked about them. Wouldn't be talking about them if they weren't there.

I'm talking about engines in general.

Originally Posted by pranavt

With DOHC, you can push both the cams quite a lot lower towards the combustion chamber and still have the desired valve angle. Hence the shorter stem. With a SOHC, there is a minimum limit for shortening the rockers or the valve stems before the geometry becomes unreliable

Hmm..not sure how! If you go look under the hoods of a few cars. SOHC heads are always more compact (ht & width) compared to DOHC. In fact that is one of the primary reasons for using it.

Originally Posted by pranavt

Or assume that they know things that are beyond your current knowledge. I chose to assume the second option rather than make a complete *** of myself.

Suit yourself !
In case I wasn't clear..I'm not assuming anything.

Originally Posted by pranavt

With DOHC, you can push both the cams quite a lot lower towards the combustion chamber and still have the desired valve angle.

IMO the stem length driven mostly by spring ht and then the port size and shape (aka port geometry). If you want a large dia, straight shot port like you see on superbikes you need a narrow included angle and relatively taller stems.

[vina]

Originally Posted by dhanushs

+1.

The difference between Grande Punto 1.3 and Swift DDiS 1.3. AFAIK, both sport same engines, in same state of tune.

Vina, IIRC,the Indian F10 is 1L and and the K10B is 1.1?. Or opposite?

It is the other way round - F10 is 1061cc (WagonR 1.1 - 1.1L) while the K10B is 998cc (1L); also I'm not sure about this, they are very different engines - K10B I hear comes with VVT and is an all aluminium engine.

[Sutripta]

Originally Posted by vina

Also are you sure about dimensions of the k10B engine - both your bore and stroke numbers are larger than those for F10 engine, even though the F10 is known to have higher displacement

Could number of cylinders have something to do with it?!

Originally Posted by aaggoswami

Very interesting discussion, which I believe is not coming out to a conclusoin.
.....
IMO, state of tune matter a lot here.

I really wouldn't have picked these engines as comparison examples. Too different. Also a capacity difference.

Regards
Sutripta

[im_srini]

Originally Posted by aaggoswami

Lets consider this :
K10B Wagon R - Bore X Stroke : 73 X 79.5
F10D Wagon R - Bore X Stroke : 68.5 X 72

Originally Posted by vina

Are you sure about dimensions of the k10B engine - both your bore and stroke numbers are larger than those for F10 engine, even though the F10 is known to have higher displacement

Aaggoswami is correct, its just that the K10B is a cylinder short...

Originally Posted by vina

K10B I hear comes with VVT and is an all aluminium engine.

The K10B engines available here do not come with VVT, the M16A in the SX4 does though...

[pranavt]

Originally Posted by Mpower

Hmm..not sure how! If you go look under the hoods of a few cars. SOHC heads are always more compact (ht & width) compared to DOHC. In fact that is one of the primary reasons for using it.

The reason why they are more compact is usually because you don't need to package 2 cam pulleys right next to each other. However, you can have the cam closer to the CC in a DOHC more than with an SOHC.

Suit yourself !
In case I wasn't clear..I'm not assuming anything.

Hey, I was asked to interpret marketing speak, apologies if I assumed wrong lol.

IMO the stem length driven mostly by spring ht and then the port size and shape (aka port geometry). If you want a large dia, straight shot port like you see on superbikes you need a narrow included angle and relatively taller stems.

Shouldn't it be the other way round? As in the spring height being determined by the stem length? Sounds counter-intuitive to do it the other way. I have no experience with designing engines, just understanding them, so you know more than me when it comes to that. Good info.

[vina]

Originally Posted by Sutripta

Could number of cylinders have something to do with it?!

Regards
Sutripta

You are right about that, overall volume would have 4 cyl for F10 and 3 for k10.

However with that for comparison we should really compare the per-cyl power/torque. I guess you already know that and were nudging me towards realising my folly. Thanks.

[vina]

Originally Posted by im_srini

Aaggoswami is correct, its just that the K10B is a cylinder short...

Attachment 535695



The K10B engines available here do not come with VVT, the M16A in the SX4 does though...

Got it already - you didn't have to put table However from the numbers you have we must compare "per cylinder" torque or power (normalised by displacement). In any case I didn't understand what Aaggoswami was trying to get to.

[aaggoswami]

Originally Posted by vina

also I'm not sure about this, they are very different engines - K10B I hear comes with VVT and is an all aluminium engine.

Originally Posted by Sutripta

I really wouldn't have picked these engines as comparison examples. Too different. Also a capacity difference.

Originally Posted by vina

In any case I didn't understand what Aaggoswami was trying to get to.

Blame it on my poor presentation skills. What my point is :
-> Mainly the power and torque characteristics are dependent on state of tune.
-> To prove my point, I was giving some example of very old old engine with different bore:stroke ratio and new engines with different bore:stroke ratio.

I hope I'm clear now. I have compared Ikon and Baleno as they are mainly from same time.

Yes, gearing has to do with it, but not so much in first two gears atleast. I dont think that Wagon R has so much changed gear ratios and is drastically low or high geared.

We have often concluded on TBHP that Civic has a weak bottom end, have we ever considered that Corolla can have a lower gearing ?

To the best of my knowledge, K10B is all aluminum and very light, weighing only 47kg dry.

[vina]

Originally Posted by aaggoswami

Blame it on my poor presentation skills. What my point is :
-> Mainly the power and torque characteristics are dependent on state of tune.
-> To prove my point, I was giving some example of very old old engine with different bore:stroke ratio and new engines with different bore:stroke ratio.

I hope I'm clear now. I have compared Ikon and Baleno as they are mainly from same time.

Yes, gearing has to do with it, but not so much in first two gears atleast. I dont think that Wagon R has so much changed gear ratios and is drastically low or high geared.

We have often concluded on TBHP that Civic has a weak bottom end, have we ever considered that Corolla can have a lower gearing ?

To the best of my knowledge, K10B is all aluminum and very light, weighing only 47kg dry.

I agree that apart from bore/stroke a lot of other factors will come into play - I guess state of tune is an amalgam of a lot of them together.

Anyway, looking at stroke only: "effective bore" for a (hypothetical, for comparison with 3-cyl k10b ) 3-cyl F10D will be about 15% large than you stated. Stroke will not change.

then k10B has a longer stroke at 79mm vs. 72mm for F10D. This is an increase of about 10%. Also k10B has a displacement about 5% less than F10D (999cc vs. 1061cc) . So overall torque should have been about 5% less if stroke length was same.

Thus overall you would get a difference of about (roughly) 5% based on stroke alone, with k10B having a higher torque at the same rpm.

Now k10B is rated 90Nm@3500rpm and F10D is rated 84Nm@3500rpm - a difference of about 6% (roughly same as the estimate of 5% above).

I don't know the lower-rpm numbers but I would be surprised if they tell a very different story. And they might given your experience with the cars.

State of tune etc. matter a lot but unless there are big inefficiencies somewhere that can be removed in a new design, it is pretty hard to get around Physics.

[Sutripta]

@Srini, good to see you here!

@aaggoswami
Displacement trumps everything. So when we talk of long/ short stroke, constant displacement is implied. The metric is the 'squareness' of the engine, rather than absolute values for stroke.

And to bring the focus back to the topic, let me reiterate the question.
"Is it possible to design a short stroke engine with a torque curve similar to a long stroke engine."

Please note that lack of a ready example is not proof of impossibility! (Pls. note SS-Travellers signature)

Regards
Sutripta

[pranavt]

Originally Posted by Sutripta

And to bring the focus back to the topic, let me reiterate the question.
"Is it possible to design a short stroke engine with a torque curve similar to a long stroke engine."

Please note that lack of a ready example is not proof of impossibility! (Pls. note SS-Travellers signature)

Regards
Sutripta

Play with the cam profile, intake and exhaust port diameters and total lengths, etc. Should be doable pretty easily if you have a good engine simulator and some time.