EVO 8 head vs 1G head

TEC · Dec 15, 2003

Re: Re: Re: F/I vs N/A

Velocity does not become less important. You are theorising wrong. You are forcing air into the intake manifold, yes. But it is not forced into the engine. The piston travels way faster than the air it is trying to suck in. It is still trying to suck in on a turbo car. The turbo car simply has a denser mixture to suck in.

I can only assume then that everyone elses theory on why turbocharging works is wrong then?

Start here: How turbocharging works (this is not a slant against you but a clearer way to express what I am trying to get across in basic terms)

Science tells us that a given cylinder will hold only so much air (I'm intentionally discounting varibles such as air density, elevation, etc. for the purpose of simplicity). Beyond that given, air must be forced in to exceed that given amount or the cylinder made longer. This is what happens in turbocharging. The turbo FORCES more air past the valves in the cylinder than what would normally occur. This compaction causes a higher amount of oxygen to be present in the mixture. The density that you refer to happens inside of the cylinder not out in the intake. If it did occur in the intake you would get the F&F affect, you know "manifold welds in danger", which by the way is impossible since there are always at least 2 valves open in one of the cylinders during any part of the engine cycle.

NO! There's VERY LITTLE DIFFERENCE. There's no such thing as suction, either.

Yes there is. If you've every worked on a carbureted engine its quite apparent. By placing your hand over the carb you can feel the air being pulled into the carb. Again, with the valves being the only hole in the closed cylinder, as the piston drops it pulls air into the cylinder. You can see this affect if you take a straw and place a ball of paper bearly smaller than the straws interior diameter inside. If you hold the straw perpendicular to the ground the ball drops through the straw. If you take your finger and place it on top of the straw, cutting off any air from the top side, the ball will stop traveling. Why? As the ball pushes air out of the bottom of the straw, it also pulls air in behind it. The same goes with a piston in a cylinder.

However, saying that velocity matters for an N/A engine, but not for a turbo engine is just ridiculous.

That is not what I said, please re-read my post.

Lastly, I'm not a bench racer. If someone can bring some proof or evidence to support a claim to smaller ports, then fine I'm willing to discuss it. But until such time, its useless to continue on this subject. (this is not directed towards anyone but merely towards the total outcome of this thread)

Will's Fiero · Dec 15, 2003

TEC said:
Yes there is. If you've every worked on a carbureted engine its quite apparent. By placing your hand over the carb you can feel the air being pulled into the carb. Again, with the valves being the only hole in the closed cylinder, as the piston drops it pulls air into the cylinder.

You are speaking of suction and manifold pressure above ambient as though they are two different things... and what I'm trying to tell you is that there is NO difference between the two. If I put my hand over the throttle body of a running engine, what you are feeling is atmospheric pressure pushing air into the engine, into volume that is being emptied by the piston. Air at atmospheric pressure pushes into the cylinder, turbocharged boost also pushes its way into the cylinder. The ONLY difference is the amount of push. That doesn't change resonant lengths of intake runners, as the speed of sound in air is only slightly affected by density and affected much more by temperature. It doesn't change the necessary port size because in terms of volumetric flow rate, the engine is taking in just as much air as it would without boost.

The difference lies in the relationship of intake and exhaust pressure and the interactions therebetween during the valve overlap period.

Lastly, I'm not a bench racer. If someone can bring some proof or evidence to support a claim to smaller ports, then fine I'm willing to discuss it. But until such time, its useless to continue on this subject. (this is not directed towards anyone but merely towards the total outcome of this thread)

Did you READ the information at the link in the first post in this thread?

DGFTurbo · Dec 16, 2003

colonelfox said:
The intake, head and turbo used on 2G's was NOT designed with moddability in mind. Mitus knew exactly what they were doing. Increasing low and midrange while sacrificing topend was the goal. What you and I may see as inadaquate, an engineer on the other side of the world see's as "just enough" for the vehicle's target output and daily drivability. You don't design a car and make it easy for the consumer to modify it and then make a warranty claim when something breaks. There's too much money to be lost. The 2g heads do their job. They flow enough for what they were designed for, but there's better flow possible from the 1G heads and port work.
I'm sure Mitsu also designed the EVO intake and head for the low end grunt needed in WRC racing. They didn't do it with topend in mind as in a rally race there's little high speed running going on. It's a low and midrange battle where throttle response and instant torque is key. With a free flowing head that 525 WHP Evo would be seeing MUCH higher output but it would also have a thinner power band. They designed the bottom end to handle the incredibly harsh racing conditions the engine is exposed to. The average 6 bolt wouldn't last a day bouncing off the rev limiter and being thrashed around like that.
Nobody took a step backward, they did exactly what they set out to do.

thank you
someone understands that engineering is the art of comprimise.

99GSTRaptor · Dec 16, 2003

Will's Fiero said:
You are speaking of suction and manifold pressure above ambient as though they are two different things... and what I'm trying to tell you is that there is NO difference between the two. If I put my hand over the throttle body of a running engine, what you are feeling is atmospheric pressure pushing air into the engine, into volume that is being emptied by the piston. Air at atmospheric pressure pushes into the cylinder, turbocharged boost also pushes its way into the cylinder. The ONLY difference is the amount of push. That doesn't change resonant lengths of intake runners, as the speed of sound in air is only slightly affected by density and affected much more by temperature. It doesn't change the necessary port size because in terms of volumetric flow rate, the engine is taking in just as much air as it would without boost.

The difference lies in the relationship of intake and exhaust pressure and the interactions therebetween during the valve overlap period.

Did you READ the information at the link in the first post in this thread?

I'm going to have to agree 100% with Will on this one. Atmospheric pressure is 14.7 psi. Many people don't realize this because we always reference boost from 14.7 psi, where really 15psi of boost is 29.7 psi absolute.

When the cylinder starts it's decent, it creates a vacuum, or at least partial vacuum that is pressurized with the 14.7 psi of air as soon as the valve opens. With boost, it's just filling with a force equal to 14.7 psi + boost psi.

It may feel like it is sucking in, but a vacuum is not exerting any forces to suck, the outside pressure (atmospheric pressure) is what is exerting the forces to push (fill) the cylinder.

Eric

noreaga0221 · Dec 16, 2003

99GSTRaptor said:
When the cylinder starts it's decent, it creates a vacuum, or at least partial vacuum that is pressurized with the 14.7 psi of air as soon as the valve opens. With boost, it's just filling with a force equal to 14.7 psi + boost psi.

It may feel like it is sucking in, but a vacuum is not exerting any forces to suck, the outside pressure (atmospheric pressure) is what is exerting the forces to push (fill) the cylinder.

Eric

one of newtons laws,
with every action, there is an opposite and equal reaction

Air wouldnt enter the engine unless it was being pushed and pulled at the same time. The atmosphere cannot push air into the engine unless there was a vacuum pulling it in..

Will's Fiero · Dec 16, 2003

noreaga0221 said:
one of newtons laws,
with every action, there is an opposite and equal reaction

Air wouldnt enter the engine unless it was being pushed and pulled at the same time. The atmosphere cannot push air into the engine unless there was a vacuum pulling it in..

You don't understand Newton's laws. Air molecules go where there's space for them. The equal and opposite reactions are what push them into the opening space, because they are constantly bouncing off themselves and the surfaces that contain them. That's what makes air pressure in the first place.

noreaga0221 · Dec 16, 2003

Air pressure is a result of air being built up within a specific area. you can blow air out of your mouth but it will never go above atmospheric levels, if you blow into a balloon, it will go above atmospheric. given, probably slightly but thats because of the limitations of our lungs and the walls of the balloon being weak and easily pushed outwards by the high air pressure inside and the lower pressure outside.

The equal and opposite reactions are what push them into the opening space,

either you wont that wrong or you are agreeing with me because thats what i was just saying.

as for not understanding newtons laws, how can one not understand that. i remember numerous demonstrations showing his theory. one was to have someone drop a piece of paper and have another person try to punch through it with their fist... will they ever be able to? no because the force put out by the fist is limited by the amount of force the paper can 'hit' back with. another one would be how our cars move.. the engine spins the wheels, the ground applies a force but since its easier to move the car and not the ground, the car moves forward. if the car was in mud, you could say the ground was not exerting enough force to get the car moving.

anyway i was just throwing in that law since you think air can get into the engine just because its pushed in and that vacuum isnt a force. :dunno:

Will's Fiero · Dec 16, 2003

noreaga0221 said:
Air pressure is a result of air being built up within a specific area. you can blow air out of your mouth but it will never go above atmospheric levels, if you blow into a balloon, it will go above atmospheric. given, probably slightly but thats because of the limitations of our lungs and the walls of the balloon being weak and easily pushed outwards by the high air pressure inside and the lower pressure outside.

Air will not move without a pressure difference, so it's pressure MUST be higher in your lungs and mouth in order for the air to move out.

either you wont that wrong or you are agreeing with me because thats what i was just saying.

as for not understanding newtons laws, how can one not understand that. i remember numerous demonstrations showing his theory. one was to have someone drop a piece of paper and have another person try to punch through it with their fist... will they ever be able to? no because the force put out by the fist is limited by the amount of force the paper can 'hit' back with. another one would be how our cars move.. the engine spins the wheels, the ground applies a force but since its easier to move the car and not the ground, the car moves forward. if the car was in mud, you could say the ground was not exerting enough force to get the car moving.

anyway i was just throwing in that law since you think air can get into the engine just because its pushed in and that vacuum isnt a force. :dunno:

You were right, but for the wrong reason. As the piston goes down, air molecules bouncing around inside the port bounce out into the cylinder. Vacuum is not a force. Vacuum is an artificial concoction by humans to work with pressures less than what they breathe. It's kinda like current. People defined current to flow from (somewhat arbitrarily defined themselves) positive polarity to negative polarity. In actuality, electrons flow from negative to positive. It's just a matter of looking at the big picture.

noreaga0221 · Dec 16, 2003

Will's Fiero said:
It's kinda like current. People defined current to flow from (somewhat arbitrarily defined themselves) positive polarity to negative polarity. In actuality, electrons flow from negative to positive. It's just a matter of looking at the big picture.

that people who defined it was ben franklin. later when scientists figured out current actually flows opposite of what he said, they named his theory conventional flow and called the 'correct' theory electron flow. anyway you say vacuum is an artificial concoction made up by humans. well ok. vacuum can be an absence of air, most commonly refered to as outer space. Vacuum could also be a force opposite pressure. i dont see this going anywhere so lets just agree to disagree. just continue on with the other discussion and forget i said anything.

Will's Fiero · Dec 16, 2003

noreaga0221 said:
that people who defined it was ben franklin. later when scientists figured out current actually flows opposite of what he said, they named his theory conventional flow and called the 'correct' theory electron flow. anyway you say vacuum is an artificial concoction made up by humans. well ok. vacuum can be an absence of air, most commonly refered to as outer space. Vacuum could also be a force opposite pressure. i dont see this going anywhere so lets just agree to disagree. just continue on with the other discussion and forget i said anything.

What I was getting at was that people don't understand the relationship between N/A engines and F/I engines because they thnk that pressure and vacuum are different, when in reality vacuum is just a screwed up way of looking at pressures less than ambient.

outbost · Dec 16, 2003

I think that the 2G guys are just mad because their head ports suck. :created: Who cares about midrange on a 4cyl?

91eclipsegsx16boy · Dec 16, 2003

16g-95GSX said:
Honestly 530awhp to me is incredible considering the drivetrain loss has to be something like 22% or more. As assuming a 22% drivetrain loss that means its pushing around 679 crank hp. 600awhp would put it at 769 crank hp assuming the same loss.

Blah, must everyone disregard the phenomena witnessed where with more hp, there is less of a constant ratio-ed drivetrain loss, and it becomes more of a static number?

Dyno proof is stil silly unless there is significant difference because of the countless variables, unless there are several runs with each set up to average IMO.

On some of the ported heads found by vendors, you can see really smooth intake ports, while the one article linked for the bike heads shows big gashes in the ports to promote atomizing and proper swirl:

However, b18c5 and S54 cylinder heads, which are part of some of the highest factory specific output motors, feature extensive smoothing of head ports for better flow. Don't forget you can stil increase swirl with more lift, too. Perhaps not only size but also finish/texture of ports should be considered??? Although, in stock vs. stock I'd imagine the casting techniques of both 1g, 2g, and evo heads is the same, unlike b18c5 vs. b18c1 heads, so I guess it's a null point.

If this is a stock 1g vs. 2g vs. evo head comparison (which I believe it is), I think we should eliminate ported/vendor head comparisons as that just throws in even more factors by whomever did the porting.

Just my random 2 cents

-aaron

Will's Fiero · Dec 16, 2003

91eclipsegsx16boy said:
On some of the ported heads found by vendors, you can see really smooth intake ports, while the one article linked for the bike heads shows big gashes in the ports to promote atomizing and proper swirl:

Go back and read the article again. These gashes are not to promote atomization... they are to help adhere the epoxy he uses to raise the floor of the port.

Speaking of which, has anyone else noticed that by raising the port floor and smoothly contouring it into the valve bowl, he's increased the short-turn radius and improved the valve entry angle?

DGFTurbo · Dec 16, 2003

Will's Fiero said:
Go back and read the article again. These gashes are not to promote atomization... they are to help adhere the epoxy he uses to raise the floor of the port.

Speaking of which, has anyone else noticed that by raising the port floor and smoothly contouring it into the valve bowl, he's increased the short-turn radius and improved the valve entry angle?

Ya i noticed that too. that is one of his biggest advantages

91eclipsegsx16boy · Dec 16, 2003

Will's Fiero said:
Go back and read the article again. These gashes are not to promote atomization... they are to help adhere the epoxy he uses to raise the floor of the port.

Hmmm, my mistake. That makes much much more sense, lol.

-aaron

magnus · Dec 17, 2003

I don't know if this was mentioned before, but the 1g head ports are so large because the Japanese market Galant, used the different plenum with the twin runner setup, the Cyclone intake (Twin runner setps with butterflies was all the rage in the late eighties early 90's cars), these were used to increase torque on the slightly lazy low compression motor.

In order to save money, I suspect, they just used the same casting on the american market cars and just changed the intake manifold. A cheaper alternative, and a method of cost savings which can be seen on many mass produced cars.

After they switched to the higher compression ratio, to aid in tq production, The added complexity of the Cyclone intake was abandoned. They could move to a better cylinder head design, that would promote better cylnder filling, and overall power at a lower RPM.

Blame it on the Cyclone.

kengsx · Dec 17, 2003

I've been aware of the motoman website ever since I was looking for a good engine break-in procedure. Other than his choice in formatting and style of repetition, he brings up a lot of good arguments, and let's face it, doing things differently from the masses has always been the path to the next level.

Speaking of intakes though, how do you guys think the port velocity argument for heads applies to intake manifolds. Here there are different things happening such as resonance / pulse timing / Hemholtz theory? I would think that runner length and runner area both contribute to this, and therefore larger intake manifold ports play an additional role other than port velocity. Then again large sheetmetal intakes have two variables: large diameter and short length runners. Which of the two help more and which is a possible hinderance despite horsepower gains? It is pretty well established that short runners will move the power band up because of pressure stacking and timing of that pulse through the valves. And even if port velocity is the most significant factor, that doesn't mean there isn't a lower threshold for port size to support a certain horsepower. I would definitely agree though that the stock 1G manifold is too large for off boost / low rpm conditions.

Blame it on the Cyclone.

oh sure, doesn't everyone!

I'm banking on the fact that slightly opening up the short runners diameter will help up top. And I didn't go with anything more than a stage II head port where things were only smoothed and port matched, nothing was opened up. But like everyone else who has spent time and/or money I'm trying not to bias my view.

Ken Young

ahains · Dec 17, 2003

One note on the large VS small port argument; it is not just the size of the port, but the size of the valve as well.

If you increase the port size a bit but keep the same valve, you will most likely see a slight increase in flow on a flowbench without the valve in. But if you run the same test with the valve in place, you will see that any flow gain is trivial, and there is a noticeable velocity drop.
If you increase the port size and the valve size then your amount of flow increase becomes more significant, to overcome the loss of power from velocity drop.

I haven't been around DSMs all that long, so I don't know how the 1G and 2G valves differ.. I think what would be an interesting fact for someone to throw out would be the ratio of valve diameter / port diameter (at its narrowest) on both generations.

Thanks,
Adrian

Fourdoordsm · Dec 20, 2003

Re: Re: F/I vs N/A

TEC said:
In one application (NA) air is being pulled into the head by the engine, in a forced induction application the air is being forced into the engine by the turbocharger, this is the major difference.

Port shape, runner shape, runner length, become more important in a NA engine because of this. NA engines need to have a balance between velocity and amount of air flow, due to short timing events (the piston moving in a downward motion) in which the air is actually allowed to enter the combustion chamber. The most common mistake in porting a NA head is to open the ports and runners too much which hurts the velocity of the air entering the port which means less air will actually have the chance to make in thereby hurting performance. The author of this particular article is making the point that velocity is more important than size, which I am inclined to agree with.

However, in a forced induction engine, velocity becomes less important because the air is being compacted into the runners and pressed against the back side of the valve by force of the turbocharger. While engine timing events are still important, the constant pressure induced by the turbocharger greatly downsizes the loss of velocity that would be typical on a NA head due to larger ports and runners.

To ignore this would be to throw out years of research and belief concerning head porting for application. This is why most places port differently depending on the intended use of the head...one style of porting for a nitrous head, another method for a turbo head, another for a NA head.

First off, I don't port heads for a living, so I am not an expert.....

But you are wrong about FI being different than NA in this respect. In an NA car there is 14.7 psi of positive pressure (atmospheric pressure) on the intake manifold side of the valves and a vacuum on the cylinder side of the valves that is created when the piston moves down the bore. It is this 14.7 psi differential pressure that forces air into the cylinder when the valves open.

Put it this way, if I run a crappy little Honda engine with a massive 4 psi of boost then the only difference is I have 18.7 psi of differential pressure between the piston and intake manifold instead of 14.7 psi differential pressure. It is that DIFFERENTIAL that causes flow in either case...just a little more intense in a FI application.

Keith

lancerman · Dec 21, 2003

Update on 525whp on stock internals.
The 525 was at 28psi. The cylinder head has been ported. The small ports retained. At 22psi car picked up 35whp.

AEM was added next and the following was layed down.
Still on stock bottum end stock intake.
400whp at 15psi
500whp at 22.5psi
550whp/450tq at 27psi
envelope not pushed not knowing how much power the stock bottom end can take. gt turbos continue to make power to 35psi

there is a gt bb turbo on the car but I dont know which one. Last I talked to him he wanted to try the gt3037r. He may have went with the gt3040. It is not a big gt35r. Regardless of turbo used the numbers still suggest 2g intake port size is superior to 1g port size. Motoman theories correct IMHO.

EVO 8 head vs 1G head

TEC

Will's Fiero

DGFTurbo

99GSTRaptor

noreaga0221

Will's Fiero

noreaga0221

Will's Fiero

noreaga0221

Will's Fiero

outbost

91eclipsegsx16boy

Will's Fiero

DGFTurbo

91eclipsegsx16boy

magnus

kengsx

ahains

Fourdoordsm

lancerman

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