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Old 11th March 2010, 05:30   #16
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Originally Posted by quadra View Post
So if we were to compare Figo 1.4 with Punto 1.3d - (see specs below)

1. Which one should perform better. Sohc with higher CC or Dohc with lower engine CC.

2. How would these 2 cars react in low - mid - top end


It looks like the Punto has got the higher boost pressure, which has got to do more with the turbo arrangement.
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Old 11th March 2010, 08:05   #17
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Originally Posted by quadra View Post
So if we were to compare Figo 1.4 with Punto 1.3d - (see specs below)

1. Which one should perform better. Sohc with higher CC or Dohc with lower engine CC.

2. How would these 2 cars react in low - mid - top end
A lot of parameters decide on low end, midrange and top end. One of the parameter is oversquare and undersquare engine.
The G13 had issues with lower end, but Baleno's G16, which belongs to same engine family, had good amount of torque.

Another example. SX4's M16A and G3HC's ( i.e. ANHC ). M16A is DOHC and G3HC is SOHC. But there is difference separating them when it comes to performance.

SX4 in EU was updated to 120 bhp M16A engine. Before that, M16A gave out 125 bhp for Swift Sport. The state of tune for these EU units is higher than Indian format of the engine.

Another example.
Corolla. The one that we have still uses 1ZZ-FE where as internationally, Corolla is available with 2ZR-FE. Be it the Altis or previous generation corolla, engine has been the same. But due to differnet state of tune, they behave in a different way. Altis's bottom end is now even more stronger than Corolla's.

So, its a very difficult question to answer how an engine would perform just on basis of SOHC and DOHC. State of Tune + Technology ( like VVT of Suzuki and Honda's IVTEC ) make the difference. iVTEC manages to alter duration, timing and lift of intake cam( only on intake IIRC ).

Last edited by aaggoswami : 11th March 2010 at 08:12.
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Old 11th March 2010, 11:30   #18
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Quote:
So if we were to compare Figo 1.4 with Punto 1.3d - (see specs below)

1. Which one should perform better. Sohc with higher CC or Dohc with lower engine CC.

2. How would these 2 cars react in low - mid - top end

When you compare 2 diff engines, its the state of tune that matters. As aggoswami has mentioned, there are also examples of smaller sohc engines producing more power than a bigger dohc engine.

But if you take an SOHC and DOHC (equally tuned) engines with cam being the only diff. The DOHC should perform better.

Shan2nu
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Old 12th March 2010, 03:36   #19
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Thanks CPH, aggoswami & shan2nu for your comments.

I can see that we are talking about lot of variable factors when talking about low, mid & high ends & that equally tuned SOHC / DOHC engine with cam being the only diff....the DOHC would pefrom better.

I know but my question is.....talking SPECIFICALLY about the FIGO d vs PUNTO d keeping both engines as STOCK, which one should perform better.

A diesel TD is on the cards soon btw
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Old 12th March 2010, 08:39   #20
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Originally Posted by aaggoswami View Post
A lot of parameters decide on low end, midrange and top end. One of the parameter is oversquare and undersquare engine.
The G13 had issues with lower end, but Baleno's G16, which belongs to same engine family, had good amount of torque.
I don't think an engine being over square or under square will be a big factor for torque distribution or even the SOHC vs. DOHC debate. That's because almost all inline 4 cylinder engines are under square (stroke>bore) including both the engines you mentioned in your post. The general rule of thumb is that under square engines are geared towards better lower end torque, which is really useful for small displacement engines (and hence the 4 cylinders) whereas over square engines are geared towards better top end power (more popular in larger displacement engines).

Having said that my Subaru Impreza uses a 2.5L 4 cylinder boxer engine (EJ254) which is heavily over square (99.5 mm bore, 79.5 mm stroke) and still has amazing lower end torque delivery. Go figure!
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Old 12th March 2010, 10:30   #21
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Originally Posted by SL
That's because almost all inline 4 cylinder engines are under square (stroke>bore) including both the engines you mentioned in your post.
+1.
I was just about to say that.
Both the G13B and G16B are undersquare. Its just that the G16 gets that extra 300cc from higher stroke which helps with the bottom end torque.
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Old 12th March 2010, 23:09   #22
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it hardly matters. what it matters is shown in the following. It helps engine breathes better.
If you recall Baleno has 4 valves per cylinder, but its opening/closing is controlled by a smart single cam. We all know how greatly it can be tuned.

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Old 13th March 2010, 17:12   #23
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Quote:
Originally Posted by sujaylahiri View Post
I don't think an engine being over square or under square will be a big factor for torque distribution or even the SOHC vs. DOHC debate. That's because almost all inline 4 cylinder engines are under square (stroke>bore) including both the engines you mentioned in your post. The general rule of thumb is that under square engines are geared towards better lower end torque, which is really useful for small displacement engines (and hence the 4 cylinders) whereas over square engines are geared towards better top end power (more popular in larger displacement engines).

Having said that my Subaru Impreza uses a 2.5L 4 cylinder boxer engine (EJ254) which is heavily over square (99.5 mm bore, 79.5 mm stroke) and still has amazing lower end torque delivery. Go figure!
What you just quoted has got only really significance on n/a engines. It would not make a real impact on force induced intakes.
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Old 13th March 2010, 17:15   #24
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Originally Posted by quadra View Post
Thanks CPH, aggoswami & shan2nu for your comments.

I can see that we are talking about lot of variable factors when talking about low, mid & high ends & that equally tuned SOHC / DOHC engine with cam being the only diff....the DOHC would pefrom better.

I know but my question is.....talking SPECIFICALLY about the FIGO d vs PUNTO d keeping both engines as STOCK, which one should perform better.

A diesel TD is on the cards soon btw
I don't think that you are stupid.

From what the figures show (if we can trust official figures that is) the Punto will perform better.

The Figo is more economical.
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Old 13th March 2010, 17:36   #25
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Off Topic: The Punto MJD FE figures in there do not remotely match to the real world figures.
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Old 13th March 2010, 23:15   #26
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Quote:
Originally Posted by quadra View Post
So if we were to compare Figo 1.4 with Punto 1.3d - (see specs below)

1. Which one should perform better. Sohc with higher CC or Dohc with lower engine CC.

2. How would these 2 cars react in low - mid - top end


Whether your engine is SOHC or DOHC is kind of a moot point when it comes to diesel engines. I think there are more important factors to look at here, for comparing power and torque characteristics. Like the type of the fuel injection system, or the size and pressure rating of the turbocharger installed, or even the valvetrain technology. The SOHC vs. DOHC debate really becomes more pronounced for gasoline engines, because let's face it, all diesel engines are good at low end torque but lack top end power.

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Old 9th October 2010, 02:45   #27
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In my opinion dohc in itself does not produce any extra power (provided both sohc and dohc are operating same number of valves), it only makes the valve train heavy. But it provides a flexibility in design of the head which is all important .

Also a large stroke engine does not produce any extra torque than the same cc large bore engine. Usually larger bores are used in high revving engine due to their lower piston speeds at the same RPM so they are usually tuned to produce high torque at higher RPMs. So for similar reasons a long stroke engine is designed to produce more torque at lower RPMs.

For similar capacity (cc) a large bore engine produces higher power due to their revvy nature. Also in a large bore it is easier to put bigger valves for easy breathing at higher revs.

But a large bore requires a larger combustion chamber which is inefficient, also since high rpm engines usually run higher compression ratios it is difficult to attain high ratios with large bores, so a compromise has to be reached.
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