This is about the lack of VTC nobody denies VTEC exists on this engine. *I have held the rocker assembly in my hands*

 

Lyon is talking about cam phasing. Where, on a DOHC, you are actively changing the rotating spatial relationship between the intake and the exhaust lobes.

Both GE and GD have a solid cam cog, and they are SOHC, so the intake and exhaust are dealt with on the same cam. Thus they are fixed in position.

 

I got it, that explains the lack of true tuning. I alway get it after I embarrass myself. I wish there was more info from Honda but I think they like it that way.

 

No worries, they are easy to confuse with all the silly acronyms. :-)

 

Found it PERTS MOTORSPORT: DOHC VTEC, i-VTEC AND ADVANCE VTEC

There I go again.

 

So it doesn't go BWAHHH???

 

I would rep ya Silver, but I'm repped out on you already, good find brother.

 

I would but:

 

Thats OK, I am in a good mood anyways and that explains all the problems people are having with coils and plugs. It starts with the rockers and confuses the ecu and then wreaks the coils and plugs in my opinion. My R18 i vtec is quiet like the Fit.

 

I sure hope the "hot" CRZ that is rumored to be in the pipeline will have DOHC and be true i-VTEC...

Two words...head swap.

 

yes yes yes, I have always said that the R18 is more similar to the L15a7 than even the previous l15 engine, everything down to the mild inverted dome pistons. (except the whole atkinson-esque operation (which makes it a decent candidate for FI BTW))
So much of what Ive learned (FI wise) has been from the R18, not from the old l15. Alot of the old l15 gremlins just are not relevant anymore. Did I mention the 'unbreakable' internals (or at least I haven't figured out how yet, I'm talking 16 psi, while getting choked by a tiny turbo, at 13.0 AFR with plenty of knock (which made crap for power btw)) and the loving ecu (yes, she is loving now that I gave her an engine that doens't have a huge compression leak in it...) Anyway, I digress...

Btw, not having VTC is a blessing from an 'ease of tuning' perspective. Ask anyone of our special K friends that have endured piston/valve contact from VTC gone awry. Some K folks would actually build hard stops into their VTC sprocket to keep it from advancing too far. Like this:


The actual tuning itself is not crazy hard but the risk seems to exist.

 

This issue only arises on the k24s. The k24s come with a 25 degree gear....lots more power can be made by tuning beyond 25 degrees, so the 50 degree cam gear is swapped from the k20 I-VTEC engines. I have a VTC gear pinned to 43 degrees in my k24a2. Lots of people don't even bother with this "safety" step.

VTC is a gift from the Honda gods....this is one of the biggest improvements over the B series. I haven't seen anybody on k20a.org complain about VTC being hard to tune...or it going awry

 

Shh, I'm trying to make myself feel better, muahahha. But yea, with a dyno, tuning vtc is pretty darn easy. Same way we determine a vtec crossover threshold. Run with it on, run with it off, where the vtec line crosses above the non vtec line you set the engagement. VTC you just run different degrees of advance.

 

i thought the L15a was a VTEC-E engine?

 

Yep, It is! l15a is vtec-e. R18 is what I'll call atkinson-vtec (2 cam profiles for 1 valve. 1 profile closes after bdc the other profile is essentialy a normal mid range lift/duration, which means it actually lacks a true high rpm profile). L15a7 is back to the 'original vtec' (two cam profiles, 1 high and 1 mid/low, for both intake valves) but with 4 rocker arms per cylinder instead of the old 5.

The 'inferior' (from a pure performance perspective (it's great for mpgs)) design of the r18 atkinson-vtec is the likely reason why it has 20% more displacement but only 11% more power. (disregarding the area under the curve)

(Just 1 more example of how Honda is turning itself into a 'lowest common denominator' company (really though, why would honda make the R18 power optimized, since all of the ethusiasts (except the ultra rare 'underdog enthusiast' (I feel confident I could build a boosted R18 faster than a stock SI at a much lower cost than the base price of an SI, add coilovers and wide tires, and still be under the cost of a base SI.)) would buy the SI)).


O how I love digressions!

 

Since it's a separate lobe, it can have earlier opening, higher lift, and later closing...all 3. And it has zero clearance. That's where the LMS resides.

geo

 

Geo, we were specifically talking about Honda's variable cam phasing system, which is what is often denoted by the i-VTEC moniker. Not Just Fit's in general.

And having a fixed advance on one lobe on a single cam is nothing like VTC, and in many instances will be detrimental to VE.

 

I just watched a ten minute video on youtube that explained the i-VTEC in the R18. In the beginning of the video they said that i-VTEC can control timing and valve throw with one cam.. but through the entire video they never said anything about timing. I'm guessing it's a secret Honda technology

 

Post link, be interested is seeing it.

 

Here's a link to a Honda selling their R18 lol it's a pretty good video

YouTube - ‪i-VTEC Technology‬‏