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Old 14th September 2007, 03:33   #1
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Default BHP CC ratio

Common thinking is that the bigger the engine the more power it makes. But in some cases I've seen smaller engines making more power. For example the Swift's 1300cc engine makes 87 bhp but the Logan's 1400cc engine makes 75 bhp. While the similar sized Aveo's 1400cc engine makes much 94 bhp.

My questions:
- What is the relation between the BHP (the power an engine makes) and the CC (engine size)?
- Is there a maximum amount (in terms of bhp) of power an engine can make? Say.. an 800cc can belt out only 50 bhp of power.. not more than that.
- If the Aveo's engine can make 94bhp.. does that mean the Logan's engine can do the same?
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Old 14th September 2007, 04:31   #2
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theres the reliability factor too.and the economy.
a f1engine makes close to 1000hp from a 2.4 l engine but it has to last only for 2 races.
these cars u mentioned are built for comfort and economy. thats why we mod cars getting more out of them.
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Old 14th September 2007, 05:31   #3
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Quote:
If the Aveo's engine can make 94bhp.. does that mean the Logan's engine can do the same?
Yes, there are remaps available for the Logan 1.4, 16 and DCI.
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Old 14th September 2007, 05:39   #4
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Quote:
Originally Posted by BUSA View Post
Yes, there are remaps available for the Logan 1.4, 16 and DCI.
A remap can do only 20-30% atmost, and that too at the cost of reliability at many cases.
Engines are not just about size.
For example in 1920s a 5L engine would make only 20bhp.
So with twin turbo etc., you can have a 1.8L engine making 250bhp, and with a carb, you can have a similar sized engine make 50bhp.

Power is energy produced/time.
So if 2 engines burn the same amount of fuel in similar time, but one is 30% efficient and other is 40%, this means that the 40% one will produce more power
Power=Energy/time.
So the trick to power is
1. Burn more fuel in lesser number of time. This is achieved mostly by the injection mechanism
2. Burn the fuel efficiently. If you are just throwing out unspent fuel, its wastage, so you put in a turbo to force in more air, increase compression ratio, reduce friction blah blah.

When you have a bigger engine, you have a bigger chamber, so you can put in more fuel in lesser number of time.
So everything else remaining same a bigger engine will produce more power, but the other things are different for different cars, so you have these different numbers
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Old 14th September 2007, 12:04   #5
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Quote:
Originally Posted by ashutoshb View Post
Common thinking is that the bigger the engine the more power it makes. But in some cases I've seen smaller engines making more power. For example the Swift's 1300cc engine makes 87 bhp but the Logan's 1400cc engine makes 75 bhp. While the similar sized Aveo's 1400cc engine makes much 94 bhp.

My questions:
- What is the relation between the BHP (the power an engine makes) and the CC (engine size)?
- Is there a maximum amount (in terms of bhp) of power an engine can make? Say.. an 800cc can belt out only 50 bhp of power.. not more than that.
The amount of power an engine can produce depends on a large number of factors inclusive but not limited to:

1. Engine Size
2. Number of camshafts
3. Cam profiles
4. Induction (Forced/NA)
5. Fuel Type
6. Compression Ratio

1. Engine Size: Very obvious. A larger capacity engine will produce more power than an equally efficient smaller capacity engine.

2. Number of camshafts:Generally the rule of the thumb is, a DOHC engine will be more efficient than a SOHC engine. However, this efficiency may not just translate to more power being produced from the same engine, but may effect the torque or fuel efficiency as well, since the engine is able to burn fuel more efficiently than an equivalent SOHC engine.

3. Cam profiles: An engine with a higher cam profile will give more top end power than an equivalent engine with a lower cam profile. However, the offshoot will be rough idling and loss of driveability. The engines used in F1 cars use very high cam profiles, and hence hardly produce any power below ~6K RPM but rev upto 17-18K RPM. It is good for a race engine but bad as a daily drive since it will ruin your driveability. So when one wants to go for a cam upgrade, one needs to strike a balance between driveability and power.
This is where variable valve timing systems come in handy. They allow good driveability along with better cc to bhp ratio. Examples are the famous VTEC system by Honda. The previous generation S 2000 had a 2L DOHC VTEC engine. It is a NA unit that produced ~240 bhp. That equates to ~120 bhp per liter of displacement. Other examples are BMW's VANOS and Double VANOS, Mitsuibishi's MIVEC, Toyota's VVTi etc.

4. Induction: Forced Induction will give you better power than an equivalent NA engine. Pretty self explanatory. FI allows the engine to burn more fuel by using different approaches. However, one needs to make sure that the engine internals are able to handle the additional stress.

5. Fuel Type: Using fuel with higher octane rating usually means fuel is burnt more efficiently. However, this is also dependent on the compression ratio of the engine. An engine with a low compression ratio (like most of our Indian cars) will not benefit from higher octane rated fuel simply because it will result in pre-combustion. Top fuel dragsters in US use almost 85% methanol (correct me if I am wrong) because the compression ratio those engines run, it is able to burn it efficiently.

6. Compression Ratio: An engine with a higher CR will produce more power than an equivalent engine with a lower CR. This should also be supplemented with better octane fuel being used which will make the engine more efficient.

As I stated above, the amount of power an engine can produce includes but not limited to the above mentioned factors. So experts, please contribute and mention other factors which I am not aware of.
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Old 14th September 2007, 12:21   #6
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So, more power out of smaller engine = less engine life.
Is it also, less power out of larger engine = more engine life?
Quote:
Originally Posted by paras211 View Post
f1engine makes close to 1000hp from a 2.4 l engine but it has to last only for 2 races.
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Old 14th September 2007, 12:34   #7
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Originally Posted by diabloo View Post
So, more power out of smaller engine = less engine life.
Is it also, less power out of larger engine = more engine life?
No thats not true at all. It depends on the cost of the technology used.

For e.g

Honda City IDSI - 77bhp
Honda Cty Vtec - 100bhp

Both are 1.5L but the Vtec will surely have more engine life then the IDSi due to the tech used. Also till date there is never been a Vtec engine failure (barring F1 ofcourse where Hondas engine's are not the most reliable)
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Old 14th September 2007, 12:51   #8
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Its got to do more with the materials used for the engine and the technology. Honda S2000 makes 240 hp out of 2.0 litres. Its a very reliable car (Same holds true for the its build also).
Basically it shows the company's maturity in engines.
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Old 14th September 2007, 13:02   #9
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^^Hehe thats hardly any power... the EVO does 286bhp in the stock state of tune with the FQ models doing 320bhp, 360bhp and there was even a limited edition 400bhp. Ofcourse its turbocharged but then I guess its the highest bhp per liter ever out of an internal combustion engine.
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Old 14th September 2007, 13:07   #10
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Srishiva was not quoting the maximum bhp achieved in a 2.0L engine. Of course we know Mitsubishi is a capable company too

Quote:
Originally Posted by reignofchaos View Post
^^Hehe thats hardly any power... the EVO does 286bhp in the stock state of tune with the FQ models doing 320bhp, 360bhp and there was even a limited edition 400bhp. Ofcourse its turbocharged but then I guess its the highest bhp per liter ever out of an internal combustion engine.
Quote:
Originally Posted by srishiva View Post
Its got to do more with the materials used for the engine and the technology. Honda S2000 makes 240 hp out of 2.0 litres. Its a very reliable car (Same holds true for the its build also).
Basically it shows the company's maturity in engines.
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Old 14th September 2007, 13:42   #11
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The Grand Vitara in India is detuned to produce 119 BHP from the 2.0 liter 16V DOHC engine that produces 140 BHP in Europe.

The way they did it I guess is by reducing the compression ratio for Indian models from 10:5 to 9:5. Am I correct?

And can we undo this so that the Grand Vitara we buy from maruti can be restored to it's original 140BHP?
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Old 14th September 2007, 15:00   #12
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Quote:
Originally Posted by reignofchaos View Post
^^Hehe thats hardly any power... the EVO does 286bhp in the stock state of tune with the FQ models doing 320bhp, 360bhp and there was even a limited edition 400bhp. Ofcourse its turbocharged but then I guess its the highest bhp per liter ever out of an internal combustion engine.
Dude there are no limits (almost) to what you can achieve in FI. There are FWD Honda Civics with B16s and B18s producing over 600 bhp at the flywheel and running 8 seconds 1/4 mile. Check out these videos for an example:





My point is that an Evo FQ400 producing 400bhp with FI is certainly commendable, but keep in mind that, after a limit, it is very difficult to make a NA engine produce more power, whereas it is not so in case of a FI engine (till a certain point, of course).

This is the very reason I mentioned the S 2000 engine. FYI the F20C (engine code for the previous gen S2000 engine) had a redline of 9K RPM (It had to, for it to be able to produce so much power). It also won the "International Engine of the Year" award in the 1.8L to 2L category for five consecutive years; 2000 through 2004 (when the F20C was replaced by the F22C)

INTERNATIONAL ENGINE OF THE YEAR 2007

These are just plain facts which I am bringing to your notice. I don't want to fuel any arguments.

Last edited by doomsday : 14th September 2007 at 15:02. Reason: Updated link.
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Old 14th September 2007, 15:01   #13
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I'm talking about cars coming out of the factory with warranty... not those tuned by tuners.
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Old 14th September 2007, 15:15   #14
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Quote:
Originally Posted by anandpadhye View Post
The way they did it I guess is by reducing the compression ratio for Indian models from 10:5 to 9:5. Am I correct?

And can we undo this so that the Grand Vitara we buy from maruti can be restored to it's original 140BHP?
Compression might not be the reason alone. It could also be due to a restrictive intake/exhaust, cam profile, fuel pressure, injector sizing, ECU limitations amongst many other factors.

Yes, if you can figure out what components are different from the international version you can restore it back to 140 bhp.

FYI, Indian OHC Vtec produces 106 (?) bhp while the Thai Version produces 130 (?) bhp. I am told by changing the intake manifold, ECU, cam profile and increasing the CR one can achieve that figure on our Indian engine.
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Old 14th September 2007, 15:33   #15
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Originally Posted by doomsday View Post
Dude there are no limits (almost) to what you can achieve in FI. There are FWD Honda Civics with B16s and B18s producing over 600 bhp at the flywheel and running 8 seconds 1/4 mile. Check out these videos for an example:



Firstly what tech Honda uses of Vtec, same is used by Mitsu to extract more power and honda does not use FI but Mitsu does and a 2.0L engine from Mitsu tuned can go upto 1000whp

You can check this out a Evo which does a 1/4th mile less then 8 secs, now what you got to say about that.

Buschur Racing - Your source for Mitsubishi racing parts and accessories
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