How does capacity affect BHP?
26-04-2007, 08:02 PM
#121
10K+ Poster!!
Originally Posted by Stu @ M Developments
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 the YB, a 4litre standard YB with a T4 on will NOT make 1100BHP no matter what your friends say.
26-04-2007, 08:04 PM
#122
10K+ Poster!!
Originally Posted by Jim Galbally
[edited because i sounded like an argumentative cnut]
either you're right, or the highly skilled professional reputable engine builders are
either you're right, or the highly skilled professional reputable engine builders are
we could go on and on about this but it is getting us no where..
people will only listen to these well respected engine builders and not some silly person who has all these silly ideas about getting power from engines
Funny how this silly persons engine out performed the well respected engine builders engine even tho the well respected engine was 100 bhp more powerful...
26-04-2007, 08:25 PM
#123
Funny how this silly persons engine out performed the well respected engine builders engine even tho the well respected engine was 100 bhp more powerful...
I dont actually know what tuners cars were there as i didnt attend but If you mean Lee in the Martini 3 door that I mapped (B16 BHP) then you will find he was on his limiter at 7800rpm due to lowered gearing for sprints and he reached that speed in 0.7m.
If you mean Andy Warnells well his is built as a track car and did a respectable top speed as far as i am aware?
Yours is teh one built for top speeds is it not? Or will you be challenging Lee at the Pod and Andy at Donnington?
26-04-2007, 08:40 PM
#125
10K+ Poster!!
Originally Posted by Stu @ M Developments
Funny how this silly persons engine out performed the well respected engine builders engine even tho the well respected engine was 100 bhp more powerful...
I dont actually know what tuners cars were there as i didnt attend but If you mean Lee in the Martini 3 door that I mapped (B16 BHP) then you will find he was on his limiter at 7800rpm due to lowered gearing for sprints and he reached that speed in 0.7m.
If you mean Andy Warnells well his is built as a track car and did a respectable top speed as far as i am aware?
Yours is the one built for top speeds is it not? Or will you be challenging Lee at the Pod and Andy at Donnington?
No disrespect to anyone but just beacuse Karl or yourself say something it does not mean that it has to be taken as gospel.
On another note my car was not build as a top speed car, its only a basic T4 engine in a standard saf that creeped up to 4th and nailed it, what happened after that was just good luck
Lee and Andy Im not having a dig
26-04-2007, 08:43 PM
#126
Originally Posted by rapidcossie
Originally Posted by Karl
Hello all,
I'm only on here briefly whilst checking mail, so please dont ask any other questions as I probably won't be here to reply.
Increasing capacity "can" give a power increase but usually does'nt in 95% of cases. This is because it is usually the cylinder head air flow that defines the total air flow through the engine and hence it is the cylinder head that dicates power, NOT capacity.
As a good example take a 1.6cvh fitted with a stock 32/34 weber carb. Makes around 90bhp. Bolt ALL the parts onto a 1800cvh bottom end with the same compression ratio....................guess what..............90bhp!
The difference is that the 1800 will make that same power a few hundred rpm earlier but the maximum power is actually determined by the maximum air flow through the engine. In this example it is contolled by the head flow.(and manifolds of course)
To put it another way on two otherwise identical engines except one being bigger capacity than the other, provided the smaller engine can physically rev that little harder (i.e. mechanically without failure) then the power will be the same.
These rules apply to N/A and turbo.
However what can be misunderstood is that by using a larger capacity engine with a turbo, it is possible to make use of larger turbos without excessive lag that you would encounter with a smaller engine, and hence produce more power because you have a larger turbo. (Unless you are prepared to live with the reduced response from the smaller capacity engine)
And finally for all the doubting thomas's....................
A 2.4 YB fitted with a T34 will make around 380bhp running the turbo flat out. A 2.0 fitted with the same components.....................guess what................ 380bhp.
The 2.4 will simply make it lower in the rpm band, but likewise will run out of puff earlier meaning that the power band is no wider than the 2.0, simply that it occurs at lower rpms. This scenario is only usefull in cases where the engine has reached the end of its mechanical ability to rev, yet more power is required.
I'm only on here briefly whilst checking mail, so please dont ask any other questions as I probably won't be here to reply.
Increasing capacity "can" give a power increase but usually does'nt in 95% of cases. This is because it is usually the cylinder head air flow that defines the total air flow through the engine and hence it is the cylinder head that dicates power, NOT capacity.
As a good example take a 1.6cvh fitted with a stock 32/34 weber carb. Makes around 90bhp. Bolt ALL the parts onto a 1800cvh bottom end with the same compression ratio....................guess what..............90bhp!
The difference is that the 1800 will make that same power a few hundred rpm earlier but the maximum power is actually determined by the maximum air flow through the engine. In this example it is contolled by the head flow.(and manifolds of course)
To put it another way on two otherwise identical engines except one being bigger capacity than the other, provided the smaller engine can physically rev that little harder (i.e. mechanically without failure) then the power will be the same.
These rules apply to N/A and turbo.
However what can be misunderstood is that by using a larger capacity engine with a turbo, it is possible to make use of larger turbos without excessive lag that you would encounter with a smaller engine, and hence produce more power because you have a larger turbo. (Unless you are prepared to live with the reduced response from the smaller capacity engine)
And finally for all the doubting thomas's....................
A 2.4 YB fitted with a T34 will make around 380bhp running the turbo flat out. A 2.0 fitted with the same components.....................guess what................ 380bhp.
The 2.4 will simply make it lower in the rpm band, but likewise will run out of puff earlier meaning that the power band is no wider than the 2.0, simply that it occurs at lower rpms. This scenario is only usefull in cases where the engine has reached the end of its mechanical ability to rev, yet more power is required.
If we look at the range of 6 cylinder BMW engine we see that power does in fact increase in a linear fashion as the bottom end sizes increase 1.8 thru to 2.8 etc
Another example is the sierra OHC engines, look at the 1300 thru to the 2 litre versions, the power increases in a very linear fashion.
Going back to what tabetha and Alex said about the laws of diminishing results or some nonsense? meaning that you wont get 25% more power from a 25% increase in capacity.
I have a engine data book here that proves otherwise
The OHC range again shows you actually get more power than you would expect in some cases when going up in capacity.
26-04-2007, 09:00 PM
#127
Originally Posted by rapidcossie
Alot of people on here are blinkered Stu, thats what Im getting at.
No disrespect to anyone but just beacuse Karl or yourself say something it does not mean that it has to be taken as gospel.
No disrespect to anyone but just beacuse Karl or yourself say something it does not mean that it has to be taken as gospel.
I would NEVER want anyone to assume i am right just because i get paid to do it... i would hope they were bright enough to listen to my beliefs and arguments and then use them as a basis to start their own research into teh subject.
26-04-2007, 09:52 PM
#128
20K+ Super Poster.
No disrespect to anyone but just beacuse Karl or yourself say something it does not mean that it has to be taken as gospel.
if a doctor tells me something about medicine i dont tell them theyre wrong because i disagree.
if a plumber tells me something about pipes i dont assume he's wrong.
people are stating facts, not opinions, don't you see the difference?
27-04-2007, 07:39 AM
#130
Testing the future
Originally Posted by Jim Galbally
No disrespect to anyone but just beacuse Karl or yourself say something it does not mean that it has to be taken as gospel.
if a doctor tells me something about medicine i dont tell them theyre wrong because i disagree.
if a plumber tells me something about pipes i dont assume he's wrong.
people are stating facts, not opinions, don't you see the difference?
if they are stating a fact, then of course they are right because it is a fact. but someone saying 'this is a fact' does not make it so, even if they appear to be qualified to say so.
we are all humans with the ability to listen, think, reason, research, learn and should do that every moment of every day
27-04-2007, 07:40 AM
#131
10K+ Poster!!
So you should Gareth - everyone should.
But when presented with adequate proof to support a fact or theory then you should accept that fact or theory, even if previously you disagreed with it.
Alex
PS I did some reading on Pintos last night - the last thing you do when tuning them is modify the size of the ports. They are TOO BIG as std. This supports why a simple capacity change works. The head can flow the extra air required to fill the cylinder and make a bigger bang because of that.
But when presented with adequate proof to support a fact or theory then you should accept that fact or theory, even if previously you disagreed with it.
Alex
PS I did some reading on Pintos last night - the last thing you do when tuning them is modify the size of the ports. They are TOO BIG as std. This supports why a simple capacity change works. The head can flow the extra air required to fill the cylinder and make a bigger bang because of that.
27-04-2007, 08:29 AM
#133
I think that all Euan is trying to say that if you increase the capacity at the same time as improving the flow capability of the head and the turbo, that the power goes up by "around" the increase in capacity.
Everyone else seems to be taking the stance of limiting the increase by retaining certain limiting factors. But to be honest, you would have to be REALLY stupid to retain these limits when increasing the capacity. Obviously the norm is to take advantage of this extra air flow with a bigger turbo etc....
See that was easy, you just have to see it from BOTH sides .
Everyone else seems to be taking the stance of limiting the increase by retaining certain limiting factors
. But to be honest, you would have to be REALLY stupid to retain these limits when increasing the capacity. Obviously the norm is to take advantage of this extra air flow with a bigger turbo etc....See that was easy, you just have to see it from BOTH sides
.
27-04-2007, 08:42 AM
#134
20K+ Super Poster.
nick, then it comes down to trust i s'pose.
i trust alex to know that if he says something's a fact, then it is. if he wasn't 100% sure, he wouldnt say it. stu same as alex.
Karl i don't trust as i dont know him, but then i've never seen him be proven wrong on this kind of thing, so i'm confident in his abilities.
i trust alex to know that if he says something's a fact, then it is. if he wasn't 100% sure, he wouldnt say it. stu same as alex.
Karl i don't trust as i dont know him, but then i've never seen him be proven wrong on this kind of thing, so i'm confident in his abilities.
27-04-2007, 08:58 AM
#135
10K+ Poster!!
LOL @ nick - I would test it but for the fact I would simply be covering very old ground. I trust Dave Walker's comments so his words on shitty old Ford engines will do for me 
I try VERY hard not to spout shite about cars - to the extent its my job!
I am paid by BMW to teach their apprentices in the best programme there is (goverment proven
).
Its a matter of pride - and the fact I like to be right
Alex
I try VERY hard not to spout shite about cars - to the extent its my job!
I am paid by BMW to teach their apprentices in the best programme there is (goverment proven
).Its a matter of pride - and the fact I like to be right
Alex
27-04-2007, 11:07 AM
#136
10K+ Poster!!
Originally Posted by AlexF
So you should Gareth - everyone should.
But when presented with adequate proof to support a fact or theory then you should accept that fact or theory, even if previously you disagreed with it.
Alex
PS I did some reading on Pintos last night - the last thing you do when tuning them is modify the size of the ports. They are TOO BIG as std. This supports why a simple capacity change works. The head can flow the extra air required to fill the cylinder and make a bigger bang because of that.
But when presented with adequate proof to support a fact or theory then you should accept that fact or theory, even if previously you disagreed with it.
Alex
PS I did some reading on Pintos last night - the last thing you do when tuning them is modify the size of the ports. They are TOO BIG as std. This supports why a simple capacity change works. The head can flow the extra air required to fill the cylinder and make a bigger bang because of that.
The extra power does come from the increase in capcity
Ill have my apology anytime guys
27-04-2007, 12:26 PM
#137
Guest
Posts: n/a
Originally Posted by rapidcossie
Originally Posted by AlexF
So you should Gareth - everyone should.
But when presented with adequate proof to support a fact or theory then you should accept that fact or theory, even if previously you disagreed with it.
Alex
PS I did some reading on Pintos last night - the last thing you do when tuning them is modify the size of the ports. They are TOO BIG as std. This supports why a simple capacity change works. The head can flow the extra air required to fill the cylinder and make a bigger bang because of that.
But when presented with adequate proof to support a fact or theory then you should accept that fact or theory, even if previously you disagreed with it.
Alex
PS I did some reading on Pintos last night - the last thing you do when tuning them is modify the size of the ports. They are TOO BIG as std. This supports why a simple capacity change works. The head can flow the extra air required to fill the cylinder and make a bigger bang because of that.
The extra power does come from the increase in capcity
Ill have my apology anytime guys
I thought you meant just swapping the bottom ends would give an increas in power without touching anything else
If that wasnt your argument I stand corrected, although its pretty fuckin obvious power will go up with more capacity and fuel/air, so I didnt think we'd be arguing about that
27-04-2007, 12:36 PM
#138
10K+ Poster!!
Originally Posted by rapidcossie
didnt say it was a restriction
Bigger capacity can flow more air so it should make more power with it.
Bigger capacity can flow more air so it should make more power with it.
so your back tracking now?
27-04-2007, 12:38 PM
#139
20K+ Super Poster.
rapid, but in that scenario, you're not gaining power due to the increase in capacity per-say.
it's just that the change you make "fixes" the other flaws with the engine, and makes it work as it should
bit like mapping, when you map an engine, you don't create power, you release power thats already there as potential
it's just that the change you make "fixes" the other flaws with the engine, and makes it work as it should
bit like mapping, when you map an engine, you don't create power, you release power thats already there as potential
27-04-2007, 12:48 PM
#141
20K+ Super Poster.
depends on the system. stu explains this very well in his technical sections in Fast Ford. describing how/why this would work.
if we're talking cossie? no, it'd need a remap
if we're talking cossie? no, it'd need a remap
27-04-2007, 01:07 PM
#142
Guest
Posts: n/a
Originally Posted by Jim Galbally
depends on the system. Stu explains this very well in his technical sections in Fast Ford. describing how/why this would work.
if we're talking cossie? no, it'd need a remap
if we're talking cossie? no, it'd need a remap
27-04-2007, 03:00 PM
#143
Originally Posted by Jim Galbally
rapid, but in that scenario, you're not gaining power due to the increase in capacity per-say.
it's just that the change you make "fixes" the other flaws with the engine, and makes it work as it should
bit like mapping, when you map an engine, you don't create power, you release power thats already there as potential
it's just that the change you make "fixes" the other flaws with the engine, and makes it work as it should
bit like mapping, when you map an engine, you don't create power, you release power thats already there as potential
.You'd have to be pretty stupid to increase the capacity without taking advantage of this increase with improved in/out additions.
27-04-2007, 03:39 PM
#144
10K+ Poster!!
So with a bigger bottom end and similar head, will just the torque be increased?
My car (2.1zvh) only made 267.7bhp on APT rollers, whereas Christian made 322.5bhp (1.6cvh), on the other hand mine made 325ft/lb and Christians (If I read the graph correctly) made 271ft/lb.
Pretty much a complete swap of BHP and TORQUE.
I know a lot of other factors come into it, but is this the general outcome of bigger bottom ends over smaller ones?
His made peak power at 5000 and mine at 4000, although he is using a bigger turbo (gt30 to my t34/5).
I dont know really, hence the questions
My car (2.1zvh) only made 267.7bhp on APT rollers, whereas Christian made 322.5bhp (1.6cvh), on the other hand mine made 325ft/lb and Christians (If I read the graph correctly) made 271ft/lb.
Pretty much a complete swap of BHP and TORQUE.
I know a lot of other factors come into it, but is this the general outcome of bigger bottom ends over smaller ones?
His made peak power at 5000 and mine at 4000, although he is using a bigger turbo (gt30 to my t34/5).
I dont know really, hence the questions
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