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Well.... if you check this out, http://www.hondanews.com/CatID2015?m...43094&mime=asc you'll see they don't call anything VTEC-e other than the lean burn engine. But I'm guessing they didn't say it was your car had the lean burn engine. I'm not sure what the differance between the VTEC-e and normal VTEC is, if there is any at all. Most people on here seem to be thinking they are the same and I tend to agree. I'm not actually saying the VTEC is different, just the way the air flows in, and it's doing this by have the valves at a slight angle and by rifling the intake ports and a slightly different valve design. The actual VTEC system may differ, but I'm not sure how.

 
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Someone repped me for this comment. Funny thing is, it didn't do anything, it's just a grey dot and they didn't leave there name or a comment, so I have no idea if it is a + or -, not that it matters. what's the point in commenting if you ar enot eveng oing to tell if you like it or not?

 
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The cylinder block assembly, piston, crankshaft, cylinder head asembly(including all valve, springs, etc), rocker arm, intake manifold, etc. are the same parts for both HX and EX. I don't see the engine runs in any way different in direction or order. Therefore they should have no mechanical difference except the camshaft, which the EX is about 1mm longer in the secondary(VTEC on) lobe.

In term of fuel and lean burn, I don't know if you have heard about it or not, Honda used to state for the HX like this: ....lean burn up to 60mph(!!)...It makes more sense because even the D17 EX has lean burn up to 60mph also. Try a dyno first, look at the A/F ratio before VTEC engages. I actually asked the dyno guy to run full throttle dyno for me starting at 2000rpm, then read A/F from the dyno, it read about 17.8:1 all the way until VTEC kicks in(full throttle, 2500rpm), which then runs at 13.8 slowly riching out to 12.1 at 6800rpm. I'm sure the readings are correct because it was running on 4th gear, which will take FOREVER from 2000->2500rpm.

If you have VAFC-II, it can prove my point: under full throttle, VTEC Lo->Hi set to 3500rpm, even though VTEC doesn't engage at 2500rpm, the fuel map changes and you will feel a slight pull at 2500rpm.

I agree with the term "lean burn" engine. However, mechanically, a normal engine can't run in lean burn but nobody proved that lean burn engine cannot run normal.

 
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You want to know why EX doesn't have the same fuel economy(I will use FE below, just too lazy to type) like HX at low rpm even though they are at lean burn mode, say, at 60mph cruise?

Engine internally, EX has a little bit more air coming in than HX. Here takes away some FE. Transmission, EX has a shorter 5th gear than HX, the extra rotation per minute means that it has more burning cycle than the HX. Weight, a 79lb different means taking an HX with a young teenage female, which also takes a little. Finally, it goes to the wheel(curb weight doesn't account for the wheel). For I=(1/2)*m*(R^2), HX has light weight 14-in, EX has the 15" Si alloy wheel(03 model). While the wheel is lighter in HX, the dominant part, R, is smaller. So EX has much more roller resistance than HX. All these will transfer into FE function. I can remember the day when I had stock tires, new engine, I could run at 400mph/10gal at 60mph for EX.

 
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Yes, that's what I have been saying... in a nut shell. Their is much more than just the engine to make the MPG go up. So you say the engine takes in less air, how does it do that if it is the same exact internally as the EX?

And I'm pretty sure it runs way leaner, but I haven't bothered to pay the $55 to take it up to a dyno and check the A/F, but the 17.8 is normal for Honda. I know Toyota has gotten engines to run at 22.0, but never produced such an extreme engine, so I don't see why Honda couldn't get 19 or even 20 in the HX. Anyway, I've been saying there is much more than just the engine to getting good MPG. And actually the internals of the transmision are the same exact as the LX and DX, the final drive is way different, but I already mentioned that.

 
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Read carefully, I did say "same except the camshaft, which is about 0.5mm longer" for the EX...

 
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Honda's new K20B clains to have A/F at 60:1....sigh....

 
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Actually you said 1mm, but that's not a concern. So what you are saying is that the engine takes in less air at lower RPMs (below 60MPH, assuming you shift at 3500RPM) and that they achieve this by making the cam lobes longer? To me that sounds like the valve would be open longer hence letting more air in. If I remember right you said the VTEC lobe was the only one changed, yet it only runs lean at low RPMS? Or are you saying that they are using the some variation on the Miller cycle without a supercharger? In that case though the cams would be in a different phase too. Maybe you just understand it better than I

By the way here is Toyota's sight referring to the EFI limit A/F ratio limit of 22:1. http://toyotaperformance.com/af_metering.htm

 
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Yes, it's opening longer due to speed, but it has one valve essentially closed, therefore it takes much much less air and creating swirl for lean burn. It is the same for both EX and HX.

 
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the title of this thread needs to be edited from (solved) to (still the most anoying topic, that no one will ever agree on)

 
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Because we love VTEC, and nobody wants to accept the fact that Honda puts a rich burn VTEC-E into the EX. I didn't either, and I went through the whole process to figure it out....

Let me edit it....explain it....VTEC-E meant to be a lean-burn, 12-valve to 16-valve high lifting variable intake mechanism. A rich-burn VTEC-E means that it uses 12-valve(high+low lift) to 16-valve high lifting(both intake high lift) variable intake mechanism while ONLY maintaining a near 14:1 ratio for high lifting operation.

 
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A more interesting fact is that, Honda puts this type of mechanism into almost all type of engine, except that, they can't put the exact same mechanism into other cars. K20A3 and K24A for US Accord uses the same mechanism as the D17A for intake valve plus a VTM on the intake side(I don't name it as DOHC-iVTEC, just name it "DOHC VTEC-E with VTM), therefore they don't make too much power either.

 
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Lets just say we have vtec, it engages at some conditions, and gives smooth transition between low and hi rpms

 
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Okay, so how do we get around puddling when the other intake valve is closed?

***Edit: I see essentially closed now.

But I am still not convinced the HX doesn't run leaner

 
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I just can't do that...lol

I'm one of those super annoying people that always asks why and how. It's my job

 
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So what you are saying is that maybe the HX just doesn't lift the VTEC valve as far open as the EX, hence less air into the cylinder?

So then this could cause a higher cyclic velocity in the chamber than the EX, hence meaning it could possibly run leaner (or just simply use less air, whatever) and get better MPG when VTEC is not engaged.... am I getting this right now?

 
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Yes, the velocity is a little faster in HX than in EX, because the vacumm pressure is still the same. For both engines, swirl effect actually serves as a small, very small compressor within the cylinder, creating a little bit higher pressure than other engines, therefore it will use less fuel. ie. The dominate part of a closed system is pressure and temperature. The higher velocity in HX means it has a little more energy(will turn into torque after ignition) available too. Every SOHC VTEC Hondas today are using the same idea in low end to generate more torque and save fuel, even for those V-6's.

 
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BTW, lean burn needs both high pressure and low temperature in order to work, otherwise engine will knock.

 
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Jrfish,

I do believe that Honda initially has some plan to extend the technology of V6 VTEC into the D17 Civic EX, but later they find out that it doesn't work.

If you had read my older post, you may notice that I was talking about hybrid VTEC, which is SOHC, 5 cam lobes per cylinder, just like the older Civic EX. But interesting thing is that, the two low speed lobes are not identical, or I should say, no where get closed in term of lifting. For example, it may be 35 and 32mm for low speed and around 37mm for high speed lobe. 35mm is considered a normal non-VTEC lifting, while 32mm is almost closed, so the car is running at a true 12 valve mode. The system change over from 35/32 to 37 at 3500rpm. These engines are seen in all J30 and J32 V6 engines. But I guess Honda found out that putting 35/37/32(pri/mid/sec) in the Civic the car's low end will suffer completly(35/32 doesn't do anything good for small engines), then they decided to put 37/32 and dropped the 35, and put the change over point well below 3500rpm(again, size issue, too much torque drop beyond 3000rpm). The idea is still the same anyway, it's just the engine size that matters. So thnking of VTEC-E? Well, VTEC-E is still VTEC, but it really depends on whether it is lean-burn or normal-burn. Lean-burn it will run just like a lean-burn, normal-burn it will run like ordinary VTEC, but with the power band shifted all the way down instead of holding it high on top.

One more thing I have to bring out is that, the intake velocity of our car is way too LOW than other SOHC VTEC engines, that's why we don't hear the roar(sucking in air) like V6 VTEC combined with intake.

 
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Okay... I can accept most of that, but why is this hybrid VTEC any different than the older VTEC in older EX's that had 5 lobes per cylinder? I always thought that the older VTEC motors had three different cam profiles for the intake. I though they simply moved to the current system to save valve train weight and rotating parasitic losses to the engine, I suppose you are right also though that it would shift more power down low.

So since the lean burn VTEC-e engine runs with a slightly more cyclic effect, can you agree that it can burn leaner than the normal VTEC? And of course drawing in this more restricted air causes more power loss to the engine, hence a little lower power output on the HX. Keeping this in mind though, I am not sure what engines early 7thgens, but I know that Honda says the current EX has VTEC, not VTEC-e, and the HX has VTEC-e lean burn engine, so I am only speaking of current civics, because I have an '04 right now and really don't know much about the earlier ones.

 
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First of all, there's no difference between 01 or 05. They are completely the same.

A twelve valve system has three roles.

First, to reduce air intake and charge velocity to make lean-burn possilbe.

Second, to generate more available torque at lower rpm therefore increase efficiency. Studies has found that the the most efficient point of crusing is where the peak of torque graphs is. Simply because it uses a specific amount of fuel, not too much more from nearby rpms, but produces maximum work.

Third, to smooth out power curve, so that you don't feel a jolt or some handling issue when older VTEC poses the problem. Eventually it completes the straight line by having the "jump" at 4500rpm removed, connecting it to lower rpms.

Talking about the 5 lobe hybrid VTEC, it actually appeared in almost every SOHC VTEC engine and DOHC VTEC engine except D17s. Even older B16A has the hybrid(34/36/32) setup. However, the original VTEC, even for SOHC, like D16Y or D16Z, or B18C, H22A, they have only 2 lobe profiles. Not really, but the pri/sec profiles are just too close(<0.5mm) and can be ignored by us, at least.

Once again, there's actually not too much difference between VTEC and VTEC-E, if the VTEC-E is not in lean burn mode. Here's how. At 16-valve mode, both valve are lifting around 37mm on the VTEC-E, while VTEC lifts the rocker at around 37mm also. What's the difference then? The only difference lies at the low end when VTEC is disengaged. You save a little more fuel and produce more torque for VTEC-E design. But see? It really not making much different if the car is not truely lean-burn. You already know the FE of DX and LX, right? They are same of the EX now.

Think of it anyway, a design is a design, it doesn't always mean they are idential in all aspects. Analogy? All female(or all male) are same design in every aspect, but they are not identical in every way they work.

 
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I want to buy a Chinchilla

 
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my words

 
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D17's have VTEC-E (going at 2-3k rpm) (with one valve shut before VTEC-E kicks) Here is a link to prove d17's have VTEC-E http://www.hondanews.com/CatID2015?m...asc&archives=t
here is a link that explains what VTEC-E is. http://www.leecao.com/honda/vtec/sohcvtece.html

 
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BUt somewhere between '01 and '05 they switch from the VTEC-e engines in the EX to the normal VTEC eninge in the EX, here's the link that proves that http://www.hondanews.com/CatID2015?m...43094&mime=asc I think this has been the greatest source of confusion, one person saying EX have the VTEC-e while other say it doesn't... really depends on what year you are talking about.

 
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The best way to look is into parts, every year, 01-05, both HX and EX has the cam head/block spec listed as SOHC VTEC, and every part number is the same. So HX has SOHC VTEC too? Not really. But it just suggested that both engines (HX and EX) are the same, in term of mechanical.

 
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where does it say this? That sounds just more like an overview of the head and valvetrain.

 
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Are you serious its still the same. Look at all the part number since then. I use to have a 04 d17a2 motor it had VTEC-E like all other d17's. The d17 is built for economy, not racing. They all have VTEC-E and it is lame, it engages at 2.5-3k Take you valve cover off. inside you will see that you have only two rocker arms on the intake. If so you have VTEC-E (or no VTEC at all(DX/LX)) buddy, end of story. If you have Three rocker arms you have regular VTEC (d16). If you have three on the Intake and the exhaust side then you have DOHC VTEC and you have a (b16,b18,k20a2,h22).

 
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Dude.... I was just wundering why Honda says the '01 EX has a VTEC-e and the '05 has just VTEC. the other guy said that the VTEC-e form the HX had a slightly different cam profile too. I don't have a 7thgen civic valve cover to take off either

 
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Yes the HX has a different cam profile. But the EX and the HX are both two lobe cams. profile is how high and long each lobe opens the valve. They are both VTEC-E