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Engine analogy: dual channel vs. single channel on 939-pin Athlon64: it can run either way, lean(single channel) or rich(dual channel) but performance gain is 3%.

Cam analogy: Windows XP, with a slightly bigger hard drive upgrade on XP. Not really a big difference.

 
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OKay, they are basically the same engine, and I know all D17's with Vtec, have the same style of cams (slightly different profile), then why does the HX motor make 10 hp less? Is 10hp lost just from the slightly different cam profile and slightly different ECU A/F ration?

 
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Yes, and due to the different exhaust manifold too. Again, it's the working concept, you can have a lean burn engine (by design) running rich to produce more power, but not vice versa. You can't just lean out some engine to save fuel.

 
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http://automobiles.honda.com/models/...me=Civic+Coupe

 
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HX has less power because of fuel/ignition maps, cam profile, and the exhaust manifold. Put a EX ECU, Cam, Exhaust on a HX you will then have a EX.

VTEC-E (HX,EX)

 
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And a very different tranny gearing, A/C, power windows, power locks, keyless entery, sunroof, different rims and a couple other little things I forget. It takes alot more than what you say to switch models.

 
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I feel more dumb reading this guys...

 
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hahahah I almost posted that exact same thing........... I quess that makes 2 of us

 
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It also depends on what you do with the parts from each vehicle you can mix and match and make more power..........for example i have an hx with an ex motor in it....stayed with the HX tranny Ecu and Ignition system and with no other mods than a homemade intake system built off of what the car had in it stock and a catless exhaust i now have a good amount more power and better gearing/gas mileage than that of a stock HX or EX

 
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He ment horsepower. If you do that a HX will have the same power as a EX. This was never about sunroofs, and rims.

 
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True, but if you leave the HX tranny you will still have some bad gearing, hence not as much power to the tires, and a far slower car than an HX. And actually all the stuff I mentioned I said because it drops the weight of the car down and reduces parasitic loss to the motor, so if you are talking about speed and power to the tires, they count, but I did digress, sorry. My point was, you just can't slap an HX motor in to an EX and call it an HX or vise versa.

 
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Well, swap an HX motor+tranny+ECU in EX will make it a damn heavy HX with sun roof and EX alloy wheel plus ABS. Those things keeps the EX much heavier than HX anyway.

 
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PLEASE, please...

This was never about the trim level differences between EX/HX - Just let it go.

In fact, this whole thread should just die since the controversy was *obviously* not solved

 
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It's solved, but it's also a fact that some ppl don't want to accept.

 
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I watched The Big Lebowski yesterday. I love that movie.

 
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can someone summarize the findings?

 
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Basically, VTEC on the 7thgen is all the same. HX has a different cam and ECU than the EX. The cam on the HX causes more swirl in the cylinder than the EX so it can run a little leaner, when the VTEC isn't engaged. That's about it for the engine. Just don't think you can put an HX cam and ECU into an EX and get better gas though, the tranny on the HX is the same as the LX/DX but with a different final drive. Everybody agree on that?

 
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Agree.

Does DX/LX/HX has a lower rpm than EX when crusing at 70(3400rpm, that's stupid and noisy)?

 
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With my auto trans EX, 70mph = 2998rpms (just below vtec light).

 
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Wow, I've read the entire SOHC VTEC sticky and this one but I still don't know the kick-in RPM or EXACTLY what the VTEC-E does at certain RPMs. I know it's to help save gas, but do we get any HP or torque gains? It does engage a hi-cam does it not? I would think that would give us some gains...

Tell if this is right or wrong PLEASE because this is what I've taken from the two threads and I think it just foked me up more...

Under WOT: from 0-3000 we get better gas milleage until VTEC engages and engages the higher cam.

Not under WOT: from 0-4900 we get better gas milleage until VTEC engages and engages the higher cam.

Also, what is the VTEC light I see you talk about gear? Is it sumthin you installed?

 
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Yes, taller gears means lowwer RPM's for the same speed. The LX/DX have a little lowwer, not sure how much, but I know my aunts HX is around 2500-2700 at 60

 
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Wrong. Under WOT, you get better gas mileage up to 2500rpm, when VTEC (load sensing type) engages high cam. Not under WOT, up to 3250rpm, when VTEC (electrical threshold) engages high cam. Interesting thing is, if you are driving a manual EX, crusing at 70mph, you are always on high cam mode(just like me, 3400rpm cruise), but it still use much less fuel than auto running at 27xxrpm(as gearbox said as in low cam mode).

Just to be sure that D17 VTEC has nothing to do with a engagement point. The point is not fixed, but from 2300rpm to 3200rpm, these are the engagement thresold RANGE. You can get your car at WOT, shift out from 1st(engaged at 2500rpm minimum, first engagement of high cam) and down to 2nd, 2300rpm, VTEC still on high cam. But you can't start at 2nd and wish it to engage at 2300. It just don't work this way. The FIXED engagement point is 3250rpm, so it's the electrical thresold. But our system also have pressure sensing, which detects pressure from throttle body.

 
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Exceptional recap!

Damn, I'm glad this is over with... but watch, now someones gonna come in and say that YOU'RE wrong

 
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Always prepared for this kind of argument

 
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If that's the case, why is there a sound change (ALWAYS, unless my engine is cold) at 4,900 RPM on my manual '05 EX SE?

When WOT, the sound of the motor always becomes more aggressive and louder at 4,900 RPM... and it's always 4900 RPM at WOT, never lower or higher. Any sound change that occured when not at WOT would be impossible for me to hear with just my intake, so I can't comment on that.

If VTEC is engaging at 3,200 RPM or whatever at WOT, then what is this sound I hear? It's certainly not secondary runners, our plastic crap manifolds aren't hiding a set of those, I don't think.

It's this more aggressive intake growl after 4,900 RPM I hear every single day that makes me doubt some of the material in this thread. The change in sound is so sudden that I really doubt it's engine/intake harmonics but rather opening secondaries or VTEC engagement. What do you think?

 
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I always thought that too! I dunno tho, someone please come back on this^

 
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1. You have to realize that D17 is a small engine. Small engine is always louder in any ways.

2. 9.9:1 is supposed to be mid-high compression, which means the sound at high end will be somewhat aggressive.

3. Factor in timing and stuffs. The more timing advance, the more aggressive the sound would be, even intake cam does not change.

4. Higher rpm will change intake and exhaust velocity. Intake and exhaust sound level is solely a function of velocity, nothing else.

5. Engine at near maximum torque will change sound, because it produces more work and therefore change the valve airflow velocity.

6. You hear something at a specific point doesn't mean it happens at that specific point. ie. turbo. You sit on a bus, it starts normally, but you can't hear turbo "kicks in" until 3000 or 4000rpm. But what? Turbo is always on, even at 100rpm(I don't think you can turn off the exhaust turbine if you can turn off the intake compressor).

7. All OHC engines has a tendency to change sound to more aggressive type at higher rpm(also including (3) and (4)).

8. For D17A engines, you have to have gold ear to listen to cam profile change. If your ear is trained to listen to engine sound, like me, you can hear cam profile sound change around 2500rpm 3/4 throttle. WOT will just create too much noise for the intake and you can't hear anything.

9. If you believe VTEC kicks in around 4900rpm, grab a VAFC-II, set VTEC engagement Lo-Hi to 4900rpm. I am sure it will not stall your engine, but just grab a timer also to see how long it takes for you from 2000rpm to 6800rpm on 1st gear(Do not do it at neutral because the engine doesn't have load).

 
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ya I hear a sound change around 4k+ but its prolly due to higher airflow. Kinda like an intake is louder when more air flows through it.

 
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Interesting thing is that, I study aerospace engineering, one way and the only way to control engine noise is to keep velocity leaving the exhaust nozzle very low. That's why we now have turbofan engine instead of turbojet, which >60% of the thrust comes from the fan(does not get passed the nozzle), not the engine(which passes nozzle). Because most of the sound from engine is the AIR NOISE, not ENGINE NOISE. You actually will not hear quite alot of real engine noise in real life.

 
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I understand your points, but I'll still be skeptical until I see proof myself.

I've heard more than one engine and I know what an engine sounds like. I've been in a few other SOHC VTEC cars and the similarity between the sounds of hitting 4,900 RPM and the SOHC VTEC engagement (or secondary opening in a DOHC VTEC 3G GSR) is uncanny.

I'm just curious, but where did you get the information about the engagement from? If I read the source, it'd probably sell me.