Head

[Maitre_Te_Te]

Hello.
I have a second 1nz head and I want planing and polish it for more hp. (planing at it max) I think that it make more compression, then more hp! Polish just for the flow. It's a great idea? I think that I can have a gain about 6 bhp!

[RHDVIPbB]

To be honest, you won't see that much of a gain.

[cali yaris]

6 bhp is about 5 whp, that gain might be possible, if the ECU can handle the changes. I think you should do it, then we will all know.

But ONLY if you dyno before and after.

[ddongbap]

Hehe. He said head.

[Maitre_Te_Te]

Originally Posted by ddongbap

Hehe. He said head.

he he, yes beacause I talk french, not english and this forum is the best that I have find on the web then, I try to talk english! But I know this is not a very good eglish so, you enderstand me and this is a good begining!

[yaris-me]

I think you would be better off getting a better intake and exhaust manifold.

[RHDVIPbB]

Originally Posted by yaris-me

I think you would be better off getting a better intake and exhaust manifold.

Now with both of those and some head work, you will see some gains. Any way to get the air flowing smoother in and the exhaust gasses out of the engine is better overall.

[Maitre_Te_Te]

Originally Posted by RHDVIPbB

Now with both of those and some head work, you will see some gains. Any way to get the air flowing smoother in and the exhaust gasses out of the engine is better overall.

Ok great, but anywat, at the same time, I will put a headers and a 2" resonator back

[ddongbap]

Originally Posted by Maitre_Te_Te

he he, yes beacause I talk french, not english and this forum is the best that I have find on the web then, I try to talk english! But I know this is not a very good eglish so, you enderstand me and this is a good begining!

No no, you didn't do anything wrong. Here, in America, head is also a sexual innuendo.

[Loren]

Without someone who REALLY knows what they're doing and a flow-bench to test it on, I think you're just as likely (if not more likely) to decrease the performance of the head as you are to improve it. Modern computer-designed heads are pretty hard to improve upon.

I'd mill it to the limit for more compression and call it a day. UNLESS you're putting turbo on it. Then it makes sense to open up the ports to flow more are. (there's a difference between NA flow characteristics and forced induction)

[06silveryaris]

If you can just clear whatever molding imperfections it might have in the intake side that might cause turbulance. Keep it minimal. Something very popular here in PR is polishing the chambers like mirrors, people claim it reduces carbon build up but I have never had it done on any of my cars.

[Loren]

I seem to recall that you actually want some turbulence on the intake side. Some minor imperfection on the surface of the intake tract creates "laminar flow", increases the intake velocity, allows more air to move into the cylinder quicker, yadda yadda. Polishing the exhaust ports is good, however.

Carbon build-up shouldn't be an issue. If a person is driving their car hard enough to NEED this kind of modification, it's not going to have carbon build-up. And if you don't drive it that hard... why bother?

[Maitre_Te_Te]

polish intake and exhaust this is just what I want to do for more flow. After, I have 2 breech, I want to keep one original and second, do a test with polishing and high compression!

[cali yaris]

Great, this will add to our knowledge of the 1NZ motor -- what works, and what doesn't. The OP has a spare head, why wouldn't we encourage the test?

I understand turbulence and laminar flow. I have never heard that porting and polishing the intake ports is a bad idea. What's your source, Loren?

[Tamago]

Originally Posted by cali yaris

Great, this will add to our knowledge of the 1NZ motor -- what works, and what doesn't. The OP has a spare head, why wouldn't we encourage the test?

I understand turbulence and laminar flow. I have never heard that porting and polishing the intake ports is a bad idea. What's your source, Loren?

the issue with polishing the intake side of the head has more to do with fueling than laminar flow issues.

a mirror finish is more likely to encourage the fuel to "bead up" and stick to the ports, causing uneven combustion..

OP, i started porting a 1nzfe head, there's a LOT of metal that can be removed, but again, without an exhaust manifold with larger main pipes, you're kind of limited to improvements. the angle at which the air exits the exhaust side of the head was notably sharp, i altered this angle and gave it a much smoother curve.

then i threw the head in the trash ;) no telling if it would have been a better setup.

[Loren]

Originally Posted by cali yaris

I understand turbulence and laminar flow. I have never heard that porting and polishing the intake ports is a bad idea. What's your source, Loren?

Honestly don't remember. Did some research when I was thinking about doing a Miata head years ago, and more recently (2-3 years ago) when I was looking at doing the Spitfire head.

The info is out there. Smooth, but not polished intake. Smooth and polished exhaust. As I mentioned, perhaps different for a turbo application. For a turbo, you just want the BIGGEST opening you can get to force air into. NA, you want velocity, and bigger is not always better.

I'm all for experimentation, but if an experimenter takes a head and does a bunch of port work to it in addition to milling it for higher compression... if it works well, how do we know WHICH PART of what they did worked?

In the name of science, separating the mods and testing each of them is the way to go. Test. Mill the head and reassemble. Test. Do some light port smoothing (no polishing). Test. Polish the exhaust ports. Test. Polish the intake ports. Test.

That's the only way to truly learn what works and what doesn't.

As has been mentioned, the limiting factor for making HP on the Yaris is RPM. It makes 106 hp from the factory at about 6,000 RPM. Balk if you want, but that's really not bad. Without raising the rev limit, you're not going to gain much. Skimming the head might gain you 5-10 hp. I honestly doubt that the ports will require much smoothing, so there won't be much to gain there. (for an NA application) Same with polishing. Just not much to gain.

If you put engine management on it that will allow you to raise the rev limit and get control of the fuel and spark in the 5-8k range, then you can make more power (assuming the engine holds together). But again, you stand to gain more from tweaking the intake and exhaust manifold designs than by porting and polishing the head. The factory manifolds are tuned for maximum torque and efficiency in the cruising range (around 3-4k RPM). To make power at higher RPM requires a much different set of manifolds.

And then you end up with a Honda. 200 hp from 6-8k, but no torque below 5k. Meh.

[cali yaris]

Sorry Loren, but your theory or whatever you are basing your opinions on here (it sure isn't first hand experience with a Yaris or 1NZ motor) aren't valid or correct. And the misinformation you are spreading is, frankly, counter-productive.

As has been mentioned, the limiting factor for making HP on the Yaris is RPM

This is simply untrue.

From simple bolt-on mods (10-20 hp) to fully built turbo motors (300+), the car makes more power without changing the rev limit. I've pushed the motor pretty far now, and at 310+ whp, it STILL doesn't make power over 6000 rpm. Raising the rev limit does not make more horsepower.

If you put engine management on it that will allow you to raise the rev limit and get control of the fuel and spark in the 5-8k range, then you can make more power (assuming the engine holds together)

Incorrect again, from first hand experience.

[Tamago]

Originally Posted by cali yaris

S
This is simply untrue.

From simple bolt-on mods (10-20 hp) to fully built turbo motors (300+), the car makes more power without changing the rev limit..

horsepower is a mathematical representation of torque and rpm.

horsepower = torque X RPM/5252.. if torque remains constant, as rpms rise, horsepower rises... this is how a hayabusa can make such great horsepower, because it revs well over 12,000rpm and is still able to breathe.

raising the rev limiter will allow you to make more power mathematically, because the engine is spinning faster. whether or not the stock 1nz can breathe efficiently enough at a higher rpms (and all obvious problems with high rpms on a stock head being ignored) is another story.

also remember, you can't use your boost as an example. boosted cars don't need to rev to all high hell to make power, because their torque curve can get flatter sooner.

hondas make high horsepower because they can breathe efficiently at high rpms without failure.