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
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
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!