How does capacity affect BHP?
Originally Posted by rapidcossie
Im not talking about maximum power Stavros....
All i said was that an increase in capcity should see you with an increase in power of the same amount.
Various people posted saying I was wrong and that you very rarely see any increase in power.
Karl even stated that he has bolted a 1.8 bottom end on instaed of a 1.6 and got no extra power.
he must have missed something as power should have jumped over 10 bhp just by changing the bottom end.
All i said was that an increase in capcity should see you with an increase in power of the same amount.
Various people posted saying I was wrong and that you very rarely see any increase in power.
Karl even stated that he has bolted a 1.8 bottom end on instaed of a 1.6 and got no extra power.
he must have missed something as power should have jumped over 10 bhp just by changing the bottom end.
If I had a 1600cc K series lump and swapped the bottom end over for an 1800cc version using the complete 1.6 head the power would rise from 111hp to 118 (as long as a suitable map is used) BUT if the 1600 engine's head was flowing the most it could already then changing the capacity is not going to increase the power.
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From: scotland
Originally Posted by Stu @ M Developments
I think everyone is arguing for different scenarios now. 
Maybe someone should do a summary... Hows this.
IF you design an engine that achieve a given volumetric efficiency (say 85%) at a given RPM it will make X power.
If you then change its capacity, but redesign the engine itself to allow it to still meet the same VE and RPM statistics as the first engine, you WILL make more power.
Maybe someone should do a summary... Hows this.
IF you design an engine that achieve a given volumetric efficiency (say 85%) at a given RPM it will make X power.
If you then change its capacity, but redesign the engine itself to allow it to still meet the same VE and RPM statistics as the first engine, you WILL make more power.
If there is a restrition like a carb that is stopping the engine flow more air then I agree that no matter what you do the power will not increase.
if there is no restrction then power WILL go up.
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From: scotland
Originally Posted by AlexF
Originally Posted by rapidcossie
if there is no restrction then power WILL go up.
but not in a linear way
it looks linear to me.
Euan,
It probably goes up in a reasonably linear way for the OHC engines, as they are not maxed out to their absolute limit in the first place. If they WERE, then I would assume that although there would be an increase, it would get smaller and smaller with capacity rises UNLESS the capacity increase was gained with more cylinders (and therefore more valve area etc).
It probably goes up in a reasonably linear way for the OHC engines, as they are not maxed out to their absolute limit in the first place. If they WERE, then I would assume that although there would be an increase, it would get smaller and smaller with capacity rises UNLESS the capacity increase was gained with more cylinders (and therefore more valve area etc).
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From: scotland
Originally Posted by Mike Rainbird
Euan,
It probably goes up in a reasonably linear way for the OHC engines, as they are not maxed out to their absolute limit in the first place. If they WERE, then I would assume that although there would be an increase, it would get smaller and smaller with capacity rises UNLESS the capacity increase was gained with more cylinders (and therefore more valve area etc).
It probably goes up in a reasonably linear way for the OHC engines, as they are not maxed out to their absolute limit in the first place. If they WERE, then I would assume that although there would be an increase, it would get smaller and smaller with capacity rises UNLESS the capacity increase was gained with more cylinders (and therefore more valve area etc).
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From: scotland
Originally Posted by RichardPON
Euan - did you see my genuine questions, or does someone have to a 500bhp+ cossie to get an answer to a simple question?
Originally Posted by rapidcossie
Originally Posted by RichardPON
Euan - those OHC engines. The heads, cams etc are all identical on each one?
all pintos heads are the same.
1.4/1.6/1.8 K series 16V engines all use the same head,cams etc except VVC/135 engines.
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From: scotland
Originally Posted by martin-reyland
Originally Posted by rapidcossie
Originally Posted by RichardPON
Euan - those OHC engines. The heads, cams etc are all identical on each one?
all pintos heads are the same.
1.4/1.6/1.8 K series 16V engines all use the same head,cams etc except VVC/135 engines.
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From: Newbury
Originally Posted by rapidcossie
They increase in a linear fashion dont they alex...
But I remember reading the cams are different - but no proof etc etc.
Alex
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Originally Posted by rapidcossie
I staed that a 25% increase in capacity will see you a 25 % increase in power...
I got shot down in flames for stating this even tho i know it to be true.
I got shot down in flames for stating this even tho i know it to be true.
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So in a round-a-bout way Euan you've ended up saying the same as karl?
Those OHC examples you gave, if its the same head etc on them all then its obvious that the heads nowhere near its flow limit, so all ford did was swap the bottom ends and fit a different carb (assuming the carbs are different) this would give the increase would it not?
In which case it wasnt really the capacity change that increased power it was the that the head could flow enough power in the first place.
I'm sure if the head was designed for max flow on the smallest capacity engine the power wouldnt go up if you bolted on the biggest capacity bottom end would it?
Those OHC examples you gave, if its the same head etc on them all then its obvious that the heads nowhere near its flow limit, so all ford did was swap the bottom ends and fit a different carb (assuming the carbs are different) this would give the increase would it not?
In which case it wasnt really the capacity change that increased power it was the that the head could flow enough power in the first place.
I'm sure if the head was designed for max flow on the smallest capacity engine the power wouldnt go up if you bolted on the biggest capacity bottom end would it?
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I understand all this But, why do manufacturers like ford sell bigger engined cars then? Whats the point to them?
Ie why sell a focus with the choice of 1.6, 1.8 and 2.0 litre engines?
Why not all be 1.6 with the choice of 1.6 std, 1.6 bigger air flow, 1.6 even bigger air flow...???
Gen question...
But, why do manufacturers like ford sell bigger engined cars then? Whats the point to them?Ie why sell a focus with the choice of 1.6, 1.8 and 2.0 litre engines?
Why not all be 1.6 with the choice of 1.6 std, 1.6 bigger air flow, 1.6 even bigger air flow...???
Gen question...
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Originally Posted by Lee Reynolds
I understand all this But, why do manufacturers like ford sell bigger engined cars then? Whats the point to them?
Ie why sell a focus with the choice of 1.6, 1.8 and 2.0 litre engines?
Why not all be 1.6 with the choice of 1.6 std, 1.6 bigger air flow, 1.6 even bigger air flow...???
Gen question...
But, why do manufacturers like ford sell bigger engined cars then? Whats the point to them?Ie why sell a focus with the choice of 1.6, 1.8 and 2.0 litre engines?
Why not all be 1.6 with the choice of 1.6 std, 1.6 bigger air flow, 1.6 even bigger air flow...???
Gen question...
I know Honda and the like can make it reliable, but when you think how many div's manage to kill a fairly tame/standard focus through lack of maintenance, imagine what it would be like if they were a bit more delicate
Also I bet drivability comes into it as well, a bigger engine is quite lazy and effortless to drive compared to a revvy smaller engine.
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Originally Posted by Lee Reynolds
Why not all be 1.6 with the choice of 1.6 std, 1.6 bigger air flow, 1.6 even bigger air flow...???
Gen question...
Gen question...
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From: scotland
Originally Posted by Stu @ M Developments
Originally Posted by rapidcossie
I staed that a 25% increase in capacity will see you a 25 % increase in power...
I got shot down in flames for stating this even tho i know it to be true.
I got shot down in flames for stating this even tho i know it to be true.
The engine I originally commented on was my friends subaru EJ20 which is known for having big valves anyway.
He bolted on an EJ25 bottom end and got a 25% increase in power.
This is all I commented on but was told this HAD to be un true due to these laws and ideas people had.
I said I had wittnessed with my own eyes so I knew it to be true.
I then provided other examples where this is also true.
I dont claim to be an expert or do I claim to be 100% correct but I did claim that these increases where achiveable where other said thy were not.
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Originally Posted by Matt J
So in a round-a-bout way Euan you've ended up saying the same as karl?
Those OHC examples you gave, if its the same head etc on them all then its obvious that the heads nowhere near its flow limit, so all ford did was swap the bottom ends and fit a different carb (assuming the carbs are different) this would give the increase would it not?
In which case it wasnt really the capacity change that increased power it was the that the head could flow enough power in the first place.
I'm sure if the head was designed for max flow on the smallest capacity engine the power wouldnt go up if you bolted on the biggest capacity bottom end would it?
Those OHC examples you gave, if its the same head etc on them all then its obvious that the heads nowhere near its flow limit, so all ford did was swap the bottom ends and fit a different carb (assuming the carbs are different) this would give the increase would it not?
In which case it wasnt really the capacity change that increased power it was the that the head could flow enough power in the first place.
I'm sure if the head was designed for max flow on the smallest capacity engine the power wouldnt go up if you bolted on the biggest capacity bottom end would it?
I understand fully what your saying Matt, sorry but Im no expert(get out clause
)
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hold on, so you told all the experts that they were wrong, then you agreed with them?
i woulda thought you'd have stopped after people mentioned the F1 engines being 1.5 litre
instantly rubbishes any capacity theories
i woulda thought you'd have stopped after people mentioned the F1 engines being 1.5 litre
instantly rubbishes any capacity theories
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Originally Posted by rapidcossie
Originally Posted by Stu @ M Developments
Originally Posted by rapidcossie
I staed that a 25% increase in capacity will see you a 25 % increase in power...
I got shot down in flames for stating this even tho i know it to be true.
I got shot down in flames for stating this even tho i know it to be true.
The engine I originally commented on was my friends subaru EJ20 which is known for having big valves anyway.
He bolted on an EJ25 bottom end and got a 25% increase in power.
This is all I commented on but was told this HAD to be un true due to these laws and ideas people had.
I said I had wittnessed with my own eyes so I knew it to be true.
I then provided other examples where this is also true.
I dont claim to be an expert or do I claim to be 100% correct but I did claim that these increases where achiveable where other said thy were not.
I think this shows that everyone is arguing about different things and are all correct in their own way. To finalise my thought on why you cant just increase capacity and gain great power;
If you had taken that scoob to 3.0 litres and gained 50% more power, do you hionestly think that then boring it to 6 litres will actually double it? Thats what your posts have suggested you think, hich is why everyone is debating it...
Some engines are capped miles away from their flow limits and some are damn close to it indeed. And this topic, incidentally, was about Turbocharged engines not NASP, and i dont care how big you bore out teh YB, a 4litre standard YB with a T4 on will NOT make 1100BHP no matter what your friends say.
