Technical Discussion on Power re:Honda engines

[pornstar]

I wanted to start a thread explaining the different ideals behind NA power and FI power, its advantages and disadvantages, and other matters concerning these 2 types with reference to the Honda engine.

Please do not make this a slangging match between NA v FI etc etc. Its not about which is better, its about power, a technical discussion on the differences in relation to a honda engine. Lets use the b16a as the example as its a very common performance engine.

Let me discuss the basic theory about Power. Power in the general term is simply described as a torque mulitplied by the rpm divided by 5250 (roughly). This is the general reference to power.

As a matter of clarity, I just wanted to let you guys know my take on that. I dont like this method of power statement. I prefer to measure power as a true value at any given state, at one point in time. This for your reference is torque. HP and KWs to me is a bragging right, and not a real sense of power.

The reason I suggest this is quite simple. HP is measured as an amount of force that is done over time. Because it is a function of time, its a false sense of power. This is purely my take on it, and its not final etc.

Usuing our equation power is torque x rpm /5250. Therefore the 2 methods of power increasing is to increase the numerator as the denominator is a constant. This is the major difference in tuning philosophy. The FI route increases torque, the NA route increases RPM. In more expensive machines, both of them are increased. Turbos that rev to 10k rpms etc, and bored out high revving NA engines.

Ill leave it at that, for now, anyone care to input?

[wynode]

Well given its is a debate comparing FI and NA I think dynamic compression and volumetric efficeincy have a lot to do with it. It is not simply torque x rpm.

DCR=SCR x VE

DCR - Dynamic Compression Ratio
SCR - Static Compression Ratio
VE - Volumetric Efficeincy

Fi essentially increases your VE and consequently your DCR.

But i'm not sure what you want do discuss Andy.............is it FI vs NA or how you gauge power between an NA car and a FI car?

[wynode]

PS: the last few issues of Revs Unlimited (HCCNSW) have had some excellant write ups on this topic :)

[h22a accord]

has any one heard of BMEP "brake effective mean pressure" Basically, its a calculation of how efficient an engine at making power and torque. Then you can calculate BMEPS of other engines and compare.

you can not compare NA and turbo cars though. Either one or the other.

eg

you divide the kilowats by the rpm the engine makes at max power divided bythe capacity of the motor in litres.

the calculation is as follows is for a JDM h22a

150 ( 150kw) divided by 7.2 (7200rpm) divided by 2.2 ( 2.2 litres)

equals BMEP of 9.46

which is farking good i say.

i think an s2000 has one of the highest BMEP's in the world, 10.6 if i recall.

[KB]

My BMEP for my EJ8

96kw / 6.6 / 1.6 = 9.09

So I assume that its quite a small scale, meaning that theres a massive difference between 9.0 and 10.0.

[sivic]

but even this is in a sense a bragging right. its no good having a high value for this if it results in a car being undrivable. just like peak power. a good engine should have a good power band with a steady curve. anyway back to topic. imo the pro's of NA and FI:
NA: response and control. predictability. relative reliability.
FI: torque!- great on the freeway :) . ease of modification (power wise)

cons:
NA: difficult/expensive to extract more power.
FI: prone to reliabilty issues (esp when you wind up the boost). fuel consumption. lag. boost spikes can also be a big issue as far as drivabilty goes - usually resulting from high boost/poor tuning/poor turbo choice etc. not as easy as some think to achieve a smooth power band with turbos

all in all it comes down to taste. i prefer NA just due to the response you can achieve as this allows better performance when a few corners get thrown your way. have had plenty of turbos come close to losing it trying to follow me round corners due to boost kicking in.

however, i got to drive my first turbo the other day which was my mates GSR cordia. i know what you are thinkin. they are slow pieces of crap. stock: yes. i've taken plenty to town. but my mates has had a fair bit of work including a 2 litre conversion, big FMIC, boost wound up etc. not an absolute monster but it still f@#$kin goes. after driving that i can see they appeal of turbo power. its great to be able to put your foot down and be greeted with such a sheer push (or pull in this case). great fun once your on the move :) . i dont think i would be game to push it very hard through corners though :o
really when it comes down to choosing you really have to decide what you want from a car. depending on what you want they are both great options

[h22a accord]

but even this is in a sense a bragging right. its no good having a high value for this if it results in a car being undrivable.


its not a bragging right, because its not about who has the most powerful engine. BMEP is about how efficient an engine is at producing power.

a v12 lamborghini has waaaay more power than a h22a but it has a very similar bmep. an s2000 engine is smaller and less powerful than a 300kw hsv but the hsv has a lower bmep than the honda.

[poid]

i think the BMEP calc isnt the best, as you are only looking at peak horsepower. That tells bugger all of the story really.

As Andeh was suggesting, we should be looking at the torque of an engine...and not just peak torque, but the torque curve. Although peak torque and where it lies on the power bands still tells us more than peak hp does.

You may notice on some Japanese videos that they talk about torque to weight, and not power to weight...i think they are on the money.

[pornstar]

I think if you guys get roaring VTEC BMI edition, it would be good for you to watch it as tsuchya (sp?) tests teh Le Mans twin turbo GT NSX.

Watch carefully what he says when his driving the car, during the run, he says, the gearing doesnt match the track that he is testing it on, simply because it was made for the Le Mans circuit. But he has no problems doing fast driving, "such things are overcome with torque".

Even at the end, when he talks about the differences between teh Le Mans car and the GT NSX in JGTC, he says clearly the differnce between the cars is the power. even tho the JGTC have 500hp as their limit in their highest class, he says that most drivers in the JGTC cant imagine how much power 650hp is. Seems strange that 150hp is something they cant imagine the difference with? He is referring to the torque difference in the cars.

[toE]

but even this is in a sense a bragging right. its no good having a high value for this if it results in a car being undrivable. just like peak power. a good engine should have a good power band with a steady curve. anyway back to topic. imo the pro's of NA and FI:
NA: response and control. predictability. relative reliability.
FI: torque!- great on the freeway :) . ease of modification (power wise)

cons:
NA: difficult/expensive to extract more power.
FI: prone to reliabilty issues (esp when you wind up the boost). fuel consumption. lag. boost spikes can also be a big issue as far as drivabilty goes - usually resulting from high boost/poor tuning/poor turbo choice etc. not as easy as some think to achieve a smooth power band with turbos

all in all it comes down to taste. i prefer NA just due to the response you can achieve as this allows better performance when a few corners get thrown your way. have had plenty of turbos come close to losing it trying to follow me round corners due to boost kicking in.

however, i got to drive my first turbo the other day which was my mates GSR cordia. i know what you are thinkin. they are slow pieces of crap. stock: yes. i've taken plenty to town. but my mates has had a fair bit of work including a 2 litre conversion, big FMIC, boost wound up etc. not an absolute monster but it still f@#$kin goes. after driving that i can see they appeal of turbo power. its great to be able to put your foot down and be greeted with such a sheer push (or pull in this case). great fun once your on the move :) . i dont think i would be game to push it very hard through corners though :o
really when it comes down to choosing you really have to decide what you want from a car. depending on what you want they are both great options

err...pornstar did mention that this isn't about NA vs. FI ;)

[2ds]

lol, you allways sound so stoned when you start these threads andy

-2ds

[pornstar]

shhhhhhhhhhhhhhhhhhhhudup! :)

[wynode]

Geez lets have a more productive discussion please!

[pornstar]

Yep pls do.

Anyway, I wanted to highlight that formula for a reason. Why is it important? Looking at the formula, when rpm = 5250, then the torque cruve on your dyno MUST cross the hp/kw curve. That is a theoretical however.

But what I wanted to share was some of the basics of why people say honda engines respond so well to boost/FI.

The nature of the Honda engine as I have raised earlier with the question about bore and stroke is that its very unique. High revving NA engines usually contain a shorter stroke. What Honda did to my understanding is to raise the stroke for capacity, but lower the bore. A smaller bore size gives less friction, less friction is very important to a high revving machine. but you can see what this leads to, if we use small bores, the capcity of the motor drops. Cure this by increasing stroke, and then you get more capcity, but the longer stroke makes the engine go under alot of stress, and unable to maintain high rpms for a long time. ill go more into this later.

The nature of the honda engine is that with its high revving capabilities, the other numerator in the equation allows the engine to create a great deal of power by adding torque.

[wynode]

I'm consfused as to whether we are talking about honda engines or on how to best get a mathematical representation of power / torque accounting or its spread throughout the rev range?

[pornstar]

its everywhere and anythign wyn ;)

this has been one of hondas fortes for a long time, why/how they can produce long stroke motors that can rev to 9k rpms daily and not have problems.

[wynode]

That was in the other thread.......and a few things included bearings / ECU and quality of workmanship ;) but lets not get sidetracked! hehe

[pornstar]

wyn, the other thread doesnt even come close to answering how they did it...

[2ds]

i don't bleieve they do andy, isn't the motor in the s2k under square ?

-2ds

[pornstar]

undersquare = long stroke, small bore :)

[2ds]

gah, i mean oversquare =p

-2ds

edit: searching around i've found information on a new s2k powerplant ?
2004 s2k powertreain part 2 (http://www.hondanews.com/CatID2069?mid=2003100141147&mime=asc)

but i do believe the current model, well the one i'm taling about anyway has bore 87 / stroke 84 making it oversquare.

the new one (according to that link) is undersquare but it redlines at 8k rpm

-2ds

[pornstar]

yer, spoke to a few engineers that build race engines and when I told them that the ITR engine that revs to 9k rpms has an 87m stroke they were like, are u sure? 5 mins later, are u sure sure? 10 mins later, are u really sure? haha :)

[crx_16x]

What is the cylinder lining of the f20 made of again?

[tinkerbell]

have you considered that the reason that B18C's DO rev so high might be due to VTEC?

if there was no VTEC, the engines power curve would drop off (ie the point at which no more power is made) at about 6500rpm?

it is about breathing and airflow.

the reason 'other' engines don’t rev so high is likely due to them not making power past that point, because they are constricted by the lack of airflow into and out of the combustion chamber.

look at it this way - the B20B makes power to 6500rpm. that is where redline is.

but a B20VTEC can rev to and make power to 8500rpm...

what is the difference?

the head!

sorry it is no *magic* answer pornstar, but it is basically the crux of your ponderance :)

[Nuttz]

now that is a bloody good point tinkerbell..

[pornstar]

not at all tinker, its good that u brought it up. I hve thought about it like that, but im looking at it from an engineering point of view in the sense of the forces involved with the piston weight and counter movement.

I agree that suffocation occurs wihtout the extra lift and duration of the vtec cam, but these engineers are talking about the piston speed issue associated with the long stroke. The piston speed and the angle of the crank required to get this long stroke creates a vibration in the inside of the engine, add to thsi friction, head constraints and you can really see why its such a good engine that honda come out with.

good to hvae ur input tho as always

[J_Mech]

I think BMEP is the way to go for some part of the argument, you can compare a wide variety of engines using this claculation. Although BMEP is an actual pressure figure, so some of the values you guys have been getting are a bit weird. For the prelude (2.2L, 200Hp, 7200rpm) I get 1.1MPa or around 160 PSI. s2000 (2L, 240Hp, 9000 rpm) gives 1.2Mpa or 170PSI. Current honda F1 engine (3L, 960Hp, 18000rpm) gives about 1.6MPa, or 230PSI. So there definatly higher cylinder pressures in an F1 machine.

Another argument would be the weight of the engine rotating parts, basically the more weight the higher the engine loading from rotation speeds. So light pistons would really help out in lowering the engine loads at speed, giving the ability to develop more power and still remain with parts that are not over stressed.

Other things would include fuel type, CR, bore/stroke, etc

J_Mech

[Savant]

everyone go back to basics. torque is a turning force, measured by a force multiplied by the diameter. so torque is how hard the explosion pushes down on the piston which turns the crank. ok.
power is defined as the rate of doing work. so work done / time taken. To the layman, "how quickly we can do a certain amount of work"
one last thing that must be defined is work. work is force multiplied by distance moved.



As a matter of clarity, I just wanted to let you guys know my take on that. I dont like this method of power statement. I prefer to measure power as a true value at any given state, at one point in time


Now this is quite simple, because we can graph the "power curve" we can derive it and find any value at any point in time. so we end up with:

P = dW/dt

Where P is power, W is work and t is time.

And the units for power are kW = kJ/s and hp = 550 ft·lbf/s

[wynode]

Power is just a timed rate of work.

The reference Andy was making was in relation to the power made at a particular RPM or the relationship between power, rpm and how it is spread out throughout the rev range.

[pornstar]

Good stuff maximus. But i think you will find its illusive in the fact that honda engines make big power in fact arent making big "power". Why cant your average honda civic or integra tow another car? cos the truth is, torque as the measurement of force turning the wheels is much lower than the hp/kw figure that hondas make.

The illusive factor is that time factor. Ie hp is one foot pound moved by a horse in a given amount of time. If you look at it this way, its illusive because it really is just how many times the engine is doing it over a given amount of time that is giving the honda engines big hp/kws.

Thats why i dont like that measurement of power.

[wynode]

Well the most common honda engines are in the sub 2.5L category (hence not the best suited for towing) but I know what you're getting at. The fact that they have bad low end torque, and I take it that this is the discussion.

So.....does someone wanna post the torque stats for a 1.8L honda vs say a 1.8L Nissan?

But will that be enough?

[Savant]

Power is just a timed rate of work.

umm... yea, i think i said that.

Andy, what is this thread about? you started it off talking about NA and FI and both their advantages and now you have moved on to talking about how little torque honda engines have. Everyone has posted something up totally unrelated, i think, because no one really knows what you want here. Give us another quick run down.

Low torque in a honda engine. Either a lower force (bang) or shorter turning diameter. It would be rediculous to shorten the diameter so i'm guessing the force is decreased. This could be due to their economy factor. Put in less fuel, less bang, but lots of little bangs (8k rpm) makes the car move pretty quickly.

[wynode]

umm... yea, i think i said that.

Andy, what is this thread about? you started it off talking about NA and FI and both their advantages and now you have moved on to talking about how little torque honda engines have. Everyone has posted something up totally unrelated, i think, because no one really knows what you want here. Give us another quick run down.


:thumbsup:

[2ds]

i told you he sounded stoned when he stated these threads

-2ds

[Phantasm]

Maybe everyone needs to get into a similar mind state as andy to understand the question?

Well my idea of the honda engine is that it is a compromise.
Honda seems to have taken the ideals which they wish to fulfill, and incorporated it into there engines.
The element of torque lacking from there engines is a direct trade off of fuel economy. And all a turbo is doing to the engine is acting much like an artificial capacity increase to fill this gap, but it then reintroduces the higher use of petrol along with its increased performance.
I currently dont see any engine that features fuel efficiency, linear power production across the rev range, aswell as high levels of torque across the rev range.
Even just power and fuel economy, as even the honda engines when using vtec are not highly fuel ecomonical.
The only real solution to this problem i think, is increasing the efficiency in which an engine uses its fuel, the maximisation of its combustion and resultant energy use.
Also alternate fuels could be an issue, as the increases in torque that diesel produces is well known.

[wynode]

Another thing that honda's do well is have low emissions ;)

[2ds]

modern combustion engines are allready extreemely efficient.

-2ds

[wynode]

modern combustion engines are allready extreemely efficient.

-2ds
Really?

Last time I checked they were around the 25% efficient mark.......wouldn't call that efficient!

[2ds]

you see it doesn't sound efficient but think about it this way, how far can you move your car (say 1 ton of steel and plastic) with one litre of petrol ? maybe 10km with very average fuel cnsumpion ?

now i'll give you 1 litre of milk and we'll see how far you can push your car ?

electric motors have much greater effciency at 90%+ but current battery technology is woefull as far as energy density goes. as soon as someone creates a really good battery we can kiss internal combustion good bye..

-2ds

[wynode]

petrol engines are around 25% efficient.....they loose most of the other 75% as heat. Can't really compare petrol to milk ;)

[Savant]

Really?

Last time I checked they were around the 25% efficient mark.......wouldn't call that efficient!


:thumbsup:


even then, 25% is pretty high. I did tests on a holden camira engine (yes i know holden) and it came up 18% efficient. It sounds good saying you can move a car and passengers 400kms from a tank of petrol but it's not.



I currently dont see any engine that features fuel efficiency, linear power production across the rev range, aswell as high levels of torque across the rev range.


That's true, less fuel gives a softer bang so yeah, less torque.

[pornstar]

[QUOTE=Savant

That's true, less fuel gives a softer bang so yeah, less torque.[/QUOTE]


not always maximus

[2ds]

petrol engines are around 25% efficient.....they loose most of the other 75% as heat. Can't really compare petrol to milk ;)

25% is high and my point is still valid. the fact that you can move so far on so little fuel is very important. there is litereally nothing better given range needs and effciency needs.

think about the fact that we are also converting a liquid into mechanical energy to move the car. how much effciencydo you expect ?

-2ds

[pornstar]

on 7 beers, u could move like a whole car urself ads :) .... plus two rims ;)

[Savant]

25% is high and my point is still valid. the fact that you can move so far on so little fuel is very important. there is litereally nothing better given range needs and effciency needs.

think about the fact that we are also converting a liquid into mechanical energy to move the car. how much effciencydo you expect ?

-2ds

Not really converting liquid into mechanical energy. The liquid is going under a chemical change (liquid to gas) and the result of that moves the car. And 25% is not high at all! 25%, come on. only 1/4 of all available energy is being used! The rest goes to heat, noise, exhaust fumes etc. Big waste!


Andy, i don't know of any case where less force gives higher toque. But i haven't seen many of your experiments heh.