Info on Air Velocity and the intake side.

[jugbugz]

Ok, I've finally got the time to sit down and type out some tuning advice from HONDA Builders. This will change how we see things a bit and clarify some facts... tuning pretty much involves a lot of understanding of PHYSICS period.

This also shows how well HONDA has engineered it's parts and made the perfect combination. I've learnt that changing any parts of your car will create a negative and positive change... it's not always as positive as you think especially things like exhaust and intake. One item will affect others.

I hope everyone finds it helpful...here it goes...

As for intake manifolds, unless you've made INTERNAL MODIFICATIONS that need much improved airflow or in order to realise enhanced power, you should really stay with your stock intake or perhaps a Type R or Type R knock off for B16 and B18 based combos. For other engines, Extrude Honing the intake will improve flow and reduce pumping losses.

While we're on the intake, lets talk briefly about bored throttle bodies. WITH THE RIGHT COMBINATION OF PARTS, using an OVER-SIZED THROTTLE BODY is a legimate power enhancer. The trouble is, a lot of shops operate on the principle, "if big is good, bigger is better" Thats just not how it is at all. For example, look at a high revving race type head that's good for top-end power. It's going to loose power down low because thats the nature of making the port bigger: YOU LOSE VELOCITY< BUT YOU PICK UP VOLUME. YOU GET GOOD POWER ON THE BIG END. To some extent, that's also true on the throttle body. If you go too big, YOU LOSE VELOCITY and hurt LOW-END "STREET RPM" POWER, but you gain volume and reduce friction in the form of lower pumping loss. However, the engine doesn't need the extra volume---IT NEEDS VELOCITY. Late model VTECs have larger throttle bodies already.

More than half the time, if you flowed the head, even if you have it ported and massaged, then flowed the throttle body, you'd find the throttle body flows much more air than the engine can use at street RPM. OVER-SIZED THROTTLE BODIES SELL BECAUSE THEY MAKE YOUR ENGINE FEEL MORE POWERFUL FOR A GIVEN AMOUNT OF THROTTLE. IT'LL GIVE YOU PART-THROTTLE PERFORMANCE. For instance, at quarter throttle, it is giving the engine two-thirds throttle airflow. Your car feels more powerful, because it is receiving more throttle than your foot indicates. At wide-open throttle, though, an over-sized throttle body doesn't do you any good because the engine only flows as much air as the HEAD-INTAKE-EXHAUST-AND-CAM COMBINATION PERMITS. Infact, it may hurt off-idle performance.

All parts have to work together. If a component upstream or downstream restricts flow, or alters flow velocity in any way that the engine doesn't like, YOU LOOSE POWER.

 

[blinx9900]

As for intake manifolds, unless you've made INTERNAL MODIFICATIONS that need much improved airflow or in order to realise enhanced power, you should really stay with your stock intake or perhaps a Type R or Type R knock off for B16 and B18 based combos. For other engines, Extrude Honing the intake will improve flow and reduce pumping losses.

and this is why i hate books like this, that is wrong, and ill tell you why, b18c gsr engine uses a dual stage intake manifold, adding a 68mm throttle body has shown gains of 6whp numerous times from 4000rpm and up, furthermore the dual stage intake manifold is somewhat of a bottleneck and eliminating the butterflies by replacing the manifold with an aftermarket like BBK coupled with the 68mm tb has shown significant gains on mild set ups, obviously people with aftermarket cams and other mods are going to see much higher gains.

books like that you have to take with a grain of salt, you cant believe everything they say, its just a guy with an opinion.

 

[jugbugz]

Ok, now we I'll type out some more info on Tuning the Airflow path.

A naturally aspirated engine will consume approximately 1.25 standard cubic feet per minute (SCFM) of air per horse power at or below peak torque, while using approximately 1.4 SCFM above the torque peak to the peak horsepower value. (SCFM is a measure of airflow with atmospheric conditions at a barometric pressure of 29.92 inches of mercury, 60 degrees F, and no water in the air, i.e dry vapour pressure)POWER THEN, is directly proportional to mass flow through the engine, regardless of the unit measure you use. The mass flow is air(oxygen and other components) and fuel. When you increase mass flow through the engine you increase power. That is the result of adding cool air intakes, expensive cylinder head modifications, intake manifolds, headers, and exhaust systems.The airflow components of your engine include the intake ducting and manifold, the cylinder head, and the exhaust system. The design of these components determines the upper limits of total airflow, i.e. the horsepower limits,as well as the maximum torque potential of the engine combination. The design and the tuning of the cam determine the RPM range wherepower is made, within the airflow capacity and velocity limits of the airflow path.

Although the gross mass flow through the engine's airflow path determines the amount of power it is capable of producing, the trick is to getting the most airflow from what you've got. The measure of this is called VOLUMETRIC EFFICIENCY (VE). Improving your engines VE is the goal of most of the bolt-on performance components.

From a performance standpoint, increasing VE contirbute to increased power outputin two very important ways. FIRST Filling the cylinders with more air and fuel makes more cylinder pressure. Which is fundamental to generating power in a engine. Second, it reduces pumping losses. On the intake side, the pumping loss is the work done to fill the cylinder with air and fuel. Even though atmospheric air pressure forces the charge into the cylinder, if the pressure inside the cylinder is still lower than atmospheric, then work had to be done to create the pressure differential. The pumping losses on the exhaust side come from the work done to push the residual gases out the exhuast system. So anything we do that reduces the pressure differential, i.e. completely filling the cylinder with air and fuel, will reduce intake side pumping loss;/U] reducing the work required to evacuate the cylinder on the exhaust stroke reduces pumping loss on the exhaust side. Reducing pumping loss means that the work that would have been devoted to pulling and pusheing mass flow through the engine is now available at the crankshaft to accelerate your car.

The question arises: how best to increase the VE of your engine? To get a better understanding of this process, we need to get down to the molecule level.
The air that we breathe is approx 78% nitrogen and only 21% oxygen(the remaining 1% is other trace gases).
Oxygen molecules are the ones that combine rapidly with the molecules of the fuel to create heat and raise the pressure in the combustion chamber to make power. NITROGEN DOESN'T BURN, but it sure takes up a lot of space in the intake manifold and combustion chambers. In addition, don't forget the humidity, i.e. water vapor suspended in the intake air.

Adding fuel to this mix changes the temperature, and therefore, the pressure and density of the intake charge, as well as taking up it's own space. ALL these factors affect flow, so infact "AIR" IS NOT A STATIC VALUE. Many factors affect the amount of air/fuel that can flow through your engine. It's behaviour is completely random, in fact, it's quite predictable, which allows us to shape intake and exhaust passages that improve flow.

 

[jugbugz]

Here's a bit about 'Efficient intakes should promote Laminar Airflow'.

Essentially, air behaves like water except, as a gas, it expands more when it's temperature rises. At certain speeds, it acts as fluid, which is why aerodynamic studies use fluid dynamic equations asn oil-filled "wind tunnels." What engine builders have found is that a fluid (and therefore a gas) flows smoothly over walls and shape of a tube UNTIL IT HAS TO MAKE A TURN GREATER THAN 9 OR 10 DEGREES.

Smooth airflow is called laminar airflow. Laminar flow is when the gas or fluid " seems well organized," as Joseph Kats put it in Race Car Aurodynamics.
Laminar flow usually (but not always) produce the highest volumeflow with the least amount of drag. TURBULENT FLOW is when the air starts to tumble. It becomes disorganized, generates friction, and slows the gas or fluid flow. WHEN YOU FORCE A FLUID TO TURN MORE THAN 10 DEGREES, IT WANTS TO SEPARATE FROM THE SHAOE THAT IT'S FLOWING OVER, WHICH IS WHEN THE AIR AND GAS FLOW START TO TUMBLE AND SLOW DOWN.

In my personal view, I guess this is why cold air intakes with long hoses gives less throttle response opposed to short ram air intakes.

 

[jugbugz]

blinx, I agree with your opinion, but there must be reasons why that b18c gsr engine is able to make more power with a bigger throttle body.

oh, this book has opinions from AEM, Jacksons racing, etc etc and scientists of physics that come a long way.. it's states some very deep understandings. But anyhow, like all tuners, not everyone agrees with each other...

and this is why i hate books like this, that is wrong, and ill tell you why, b18c gsr engine uses a dual stage intake manifold, adding a 68mm throttle body has shown gains of 6whp numerous times from 4000rpm and up, furthermore the dual stage intake manifold is somewhat of a bottleneck and eliminating the butterflies by replacing the manifold with an aftermarket like BBK coupled with the 68mm tb has shown significant gains on mild set ups, obviously people with aftermarket cams and other mods are going to see much higher gains.

books like that you have to take with a grain of salt, you cant believe everything they say, its just a guy with an opinion.

 

[jugbugz]

ok, I found something...

Oversized throttle bodies affer a large diameter opening and flow more air. Is this a restriction?? IF YOUR ENGINE COMBINATION DOWNSTREAM FROM THE THROTTLE BODY WONT FLOW ANYMORE AIR, THEN THE LARGER THROTTLE BODY WONT HELP. In fact it may hurt off-idle performance...

 

[jugbugz]

HONDA HEADS

Fortunatly, the Honda has provided performance enthusiasts with some of the best-flowing production heads ever built. The architecture of the B18C1, the B16A2, and H22A1 VTEC heads are virtually right off the race track.

The intake and exhaust port designs are such that unless you are building a full race monster and/or plan to fuel you machine with methanol, very little is needed. Even the Non-VTEC B-series and the SOHC D-series engines have very efficient head design. Infact the most knowledgable tuners will tell you as far as headwork goesm spend your money on a good valve job to improve low lift flow. That's where you'll find the most improvement in airflow on these heads.

 

[jugbugz]

HEAD AND INTAKE RUNNERS

Intake runner length ultimately determines where the engine can make power. GENERALLY, longer runners make good low-to-mid range TORQUE, wereas shorter runners make high RPM horsepower.

First off, we need to clear up some misunderstandings about headwork. An awesome designed to rip it up at 10,000rpm will almost always hurt performance down in the low range. Think about it. The ports have to be bigger to flow more air at that RPM, the CHARGE VELOCITY through the intake is going to be slow. You should know what that does to the Volumetric Efficiency of the engine until the air gets moving and has enoung INERTIA to help pack the cylinder.

This is a common mistake that enthusiasts make. They come to a head porting asking for a full race deal, and then they're mad at the porter because the engine lost mid-range power and suddenly burns the tires off the car. That's if they listended to the porter and got an intake, exhaust, cam and fuel delivery to match the headwork. Most of the time, the guy just slaps on the stock intake and is really disapointed to find he's lost power all the way through the RPM range. The intake doesn't let the heads breathe, and the ports are too large to keep the velocity up, so you've got a lose-lose combination.

 

[jugbugz]

This is why having a something bigger isn't always better. Theres very little to gain in the top-end and much to loose from the bottom to mid range.

Velocity and Inertia is always the determination of where power is made and lost. Sizes and designs of the exhaust and intake affect velocity.

I know of 2 B16A's both on a EG shell, that were tuned in the same workshop and 1 was producing 10hp peak more than the other one. So the 1st one had 10hp more @ wheels than the 2nd at peak, while the 2nd one had more low-mid-range power everywhere.
This is the story, on the Drag strip, with the same driver of the workshop, the 1st car with 10hp more peak power was slower than the 2nd car by 0.5secs.. amazing... Apparently this came from TODA chief Australia. He said, the reason was because the 2nd car has more mid range power, and would pull away on gear changes. Top end power isn't everything.

 

[jugbugz]

SUMMARY on AIR

Remember that air expends when it gets hot. That doesn't create more oxygen to combine with the fuel, it only takes up space and reduces the amount of oxygen available to burn with the fuel.

ulitmately it comes down to the combination, Everything in an engine affects everything else. It's all about the Combination, not single well made specific parts.

 

[iceman]

good info, kind of thing you could write volumes of books about, ill be honest in that i barely understand physics and tech stuff too much, just learnt little first hand from trying several of components on car and mainly from what people have told me that have worked on my car

the following is completely true

"This is the story, on the Drag strip, with the same driver of the workshop, the 1st car with 10hp more peak power was slower than the 2nd car by 0.5secs.. amazing... Apparently this came from TODA chief Australia. He said, the reason was because the 2nd car has more mid range power, and would pull away on gear changes. Top end power isn't everything. "


but the whole internet thing and people just getting into modding only really know what they read on internet etc which is shame ( i also learnt the hard way), 95&#37; still think its about that top figure, i could take my car tommorow to my tuner and could comfortably squeeze 10-20 bhp at fly from my top end but would slow the car down and hurt engine

 

[blinx9900]

"This is the story, on the Drag strip, with the same driver of the workshop, the 1st car with 10hp more peak power was slower than the 2nd car by 0.5secs.. amazing... Apparently this came from TODA chief Australia. He said, the reason was because the 2nd car has more mid range power, and would pull away on gear changes. Top end power isn't everything. "

and thats where transmission gearing plays an important roll, the longer your gearing the more mid power you want, the shorter your gearing the more top end power you want, thats why rvm always tells people will b16b's the best mod is a shorter final drive.

you can do what ever you want, its very difficult to improve the midrange power of the b16b, in fact it was not made to produce midrange, it was made to produce top end power, and most of us have chosen to try and improve in that area as thats the strenght of the motor. between shifts you never fall below 6000rpm so top end improvements imo are the only things that matter.

 

[jugbugz]

and thats where transmission gearing plays an important roll, the longer your gearing the more mid power you want, the shorter your gearing the more top end power you want, thats why rvm always tells people will b16b's the best mod is a shorter final drive.

you can do what ever you want, its very difficult to improve the midrange power of the b16b, in fact it was not made to produce midrange, it was made to produce top end power, and most of us have chosen to try and improve in that area as thats the strenght of the motor. between shifts you never fall below 6000rpm so top end improvements imo are the only things that matter.

oh mid range includes 6000rpm - 7000rpm we regard the top end as the last 1000-2000rpm

Whats the best final drive ratio for street? I want to change mine but don't know where and what spec...

 

[ManosEK9]

oh mid range includes 6000rpm - 7000rpm we regard the top end as the last 1000-2000rpm

Jugbugz, what you say is a bit off mate, vtec area is not midrange at all, in contrast, is the area where the engine performs in its maximum potential.
DC2 makes only 130 bhp just before vtec kicks in, and 190 bhp in fractions of a second as soon as vtec enables.
In general, midrange is considered to be the pre-vtec area.
The midrange does not changed in case vtec operates in lower rpm, for example 4500-5000 rpm, even if you do it, you are gonna see that the gains are negligible there

 

[iceman]

it is hard to get considerable mid range from b16b but can be done, been in 1 which had almost same in mid range than a stock ek9 at near top end (n/a) and still 1.6

 

[blinx9900]

Jugbugz, what you say is a bit off mate, vtec area is not midrange at all, in contrast, is the area where the engine performs in its maximum potential.
DC2 makes only 130 bhp just before vtec kicks in, and 190 bhp in fractions of a second as soon as vtec enables.
In general, midrange is considered to be the pre-vtec area.
The midrange does not changed in case vtec operates in lower rpm, for example 4500-5000 rpm, even if you do it, you are gonna see that the gains are negligible there

i agree, i consider 6000rpm+ top end

 

[Dino-Spumoni]

Good information jugbugz, thanks for taking the time to type it out.
But credit goes to where it is due and the book is : High Performance Honda Builder's Handbook, by Joe Pettitt, 2002.
The book is from 2002 so of course its a little bit outdated in some ways, but most all of the actual theories and information are great info. As with anything do your research on a broad spectrum and take everything you hear with a grain of salt.

 

[jugbugz]

Good information jugbugz, thanks for taking the time to type it out.
But credit goes to where it is due and the book is : High Performance Honda Builder's Handbook, by Joe Pettitt, 2002.
The book is from 2002 so of course its a little bit outdated in some ways, but most all of the actual theories and information are great info. As with anything do your research on a broad spectrum and take everything you hear with a grain of salt.

Yeh, it's all theory... only have to try and find out... I'm surprised that there was nothing said about the B16B...

 

[jugbugz]

Jugbugz, what you say is a bit off mate, vtec area is not midrange at all, in contrast, is the area where the engine performs in its maximum potential.
DC2 makes only 130 bhp just before vtec kicks in, and 190 bhp in fractions of a second as soon as vtec enables.
In general, midrange is considered to be the pre-vtec area.
The midrange does not changed in case vtec operates in lower rpm, for example 4500-5000 rpm, even if you do it, you are gonna see that the gains are negligible there

I guess so... I was looking from 7000rpm because most of us have 9000rpm redline.

Thanks for the correction but since when did the B18C make an increase of 60hp within 1000rpm from vtec crossover?

B16B makes max power @ 8200rpm and at 6000rpm it's no where near. I know theres a power hike from 6000rpm but cmon, fractions of seconds later??