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#1 ·
K20A VTEC breakdown

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-Originally posted by Targa250R-



The K20A3 does not have a standard DOHC VTEC valvetrain as we know it from the B-series engines - the K20A3 should actually be called a "DOHC i-VTEC-E" engine, because it uses a VTEC-E cam setup. The K20A2 is the "real" DOHC i-VTEC engine, utilizing the standard DOHC VTEC cam setup we're all familiar with. To help you understand the differences between the K20A2 and K20A3 engines, I've included the following information from a post I made elsewhere:

Allow me to evaluate. Let's start out by defining some terms:

VTEC - Variable valve Timing and lift Electronic Control. At low RPM, a VTEC engine uses a normal cam profile to retain a smooth idle, good fuel economy, and good low-end power delivery. The VTEC mechanism engages a high-lift, long-duration "race" cam profile at a set RPM value (i.e., ~5500RPM on the B16A) to increase high-end power delivery.

VTEC-E - Variable valve Timing and lift Electronic Control for Efficiency. This system isn't really VTEC as we know it. At low RPM, the VTEC-E mechanism effectively forces the engine to operate as a 12-valve engine - one of the intake valves does not open fully, thus decreasing fuel consumption. At a set RPM value (i.e., ~2500RPM in the D16Y5), the VTEC-E mechanism engages the 2nd intake valve, effectively resuming operation as a normal 16-valve engine. Note: in a VTEC-E engine, there are no high-RPM performance cam profiles; this engine is supposed to be tuned for fuel economy, right?

VTC - Variable Timing Control. This is a mechanism attached to the end of the intake camshaft only which acts as a continuously variable cam gear - it automatically adjusts the overlap between the intake and exhaust cams, effectively allowing the engine to have the most ideal amount of valve overlap in all RPM ranges. VTC is active at all RPMs.

i-VTEC - intelligent Variable valve Timing and lift Electronic Control. This is a combination of both the VTEC and the VTC technologies - in other words, i-VTEC = VTEC + VTC. Currently, the only engines that use the i-VTEC system are the DOHC K-series engines.

Now this is where things get tricky - Honda uses the term "DOHC i-VTEC" for two different systems: The first system is used in the K20A2 engine of the RSX Type-S. The second system is used in the K20A3 engine of the Civic Si.

The First System (K20A2):

This system is pretty close to the older DOHC VTEC engines. At low RPM, the K20A2 uses a normal cam profile to retain a smooth idle, good fuel economy, and good low-end power delivery. At 5800RPM, its VTEC mechanism engages a high-lift, long-duration "race" cam profile to increase high-end power delivery. The only difference between this i-VTEC engine and the older VTEC engines is the addition of the VTC system. The intake camshaft has the automatic self-adjusting cam gear which continuously optimizes valve overlap for all RPM ranges.

Here we see an image of the intake cam lobes of the K20A2. Notice there are 3 lobes; the two side lobes are the low-RPM profiles, and the center lobe is the high-lift, long-duration profile which engages at 5800RPM. Basically the same setup as the old VTEC engines we are familiar with.



Now here we see the VTC mechanism - the gear on the end of the intake cam that adjusts valve timing (overlap) automatically on the fly.



This system is used in engines powering the JDM Honda Integra Type-R, Civic Type-R, Accord Euro-R, and the USDM Acura RSX Type-S and TSX.

The Second System (K20A3):

This system does not really conform to the "DOHC i-VTEC" nomenclature, as Honda would like us to believe. As I mentioned in my previous post, it actually should be called "i-VTEC-E," because it uses a VTEC-E mechanism rather than a standard VTEC mechanism. At low RPM, the VTEC-E system effectively forces the engine to operate as a 12-valve engine - one of the intake valves does not open fully, thus decreasing fuel consumption. At 2200RPM, the VTEC-E system engages the 2nd intake valve, effectively resuming operation as a normal 16-valve engine. There are no high-RPM performance cam profiles; this engine is tuned to balance fuel economy and power, rather than provide pure performance. On the intake cam, there is the VTC mechanism which basically is an automatic self-adjusting cam gear used to continuously optimize the valve overlap for all RPM ranges. This being a VTEC-E system - and not a true DOHC VTEC system - is the reason the K20A3 redlines at a measly 6800RPM, while the K20A2 is able to rev all the way to 7900RPM.

Here we see an image of the intake cam lobes of the K20A3. Notice there are only 2 lobes - there is a nearly round one used only for the low-RPM disabled intake valve, and then there is the regular lobe used by the other valve at low-RPM and by both valves at high-RPM:



This system is used in engines powering the USDM Acura RSX base, Honda Civic Si, Accord 4-cylinder, CRV, and Element.

Special note: The K20A3 engine used in the Acura RSX base has a slightly different intake manifold design from the K20A3 engine used in the Civic Si. The RSX engine uses a dual-stage manifold, similar in concept to the manifold of the B18C1 in the old Integra GSR. It uses long intake runners at low-RPM to retain low end power, and switches at 4700RPM to a set of shorter intake runners to enhance high-end torque. This accounts for the extra 9 ft-lb of torque in the RSX (141 ft-lb, vs. 132 ft-lb in the Civic Si).

Here is an image showing just how this dual-stage manifold works. On the top, you can see the low-RPM (long) runners are in use, and on the bottom, you can see the high-RPM (short) runners in use.



Myths:

1. The i-VTEC engine engages VTEC gradually, and not suddenly like in the old VTEC engines.

Wrong. The i-VTEC engine "engages VTEC" at a single set RPM, like always. Whoever started this rumor is a fucktard. Read the definitions above.

2. VTC engages at a set RPM.

Wrong. VTC is always activated. Read under "VTC" above.

3. The K20A3 engages VTEC at 5000+ RPM.

Wrong. Technically, there is no "VTEC" (as we think of it) in the K20A3 engine - it uses a VTEC-E technology, which engages at 2200RPM. Read under "The Second Sytem" above.
 
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#52 ·
so whats the story lads can the land of oppertunity offer me something tha i cant get here or is it a case of he dont matter-i've already said the car does 205bhb on a dyno its a k24a3 with 3 lobes on the intake and exhaust but hondata simply wont give me any sort of deal -----all i want for xmas is a chip of some sort
stressed--
pat
 
#53 ·
K so far to date on the handling qualities of the tsx (euro r)

if you toe out the back wheels the back of the car tends to take a wider line ie. as if it's always about to let go.
whereas if you camber in too much eg a deg or so the car will always feel(especially through rutted sections)like the back wants to follow the ruts-not very comfortable as the back wobbles a bit but still very taught
for me (and this has been a year in the making)one of the best set ups for everyday driving is to...
toe the front out half a deg each side ie good for tire wear (make sure whoever is doing it that they're lift is straight and level,
and keep the back as straight as you can.now if you've lowered .as i have on h-spec springs (nice for an all round drop)you are going to have to take into account camber changes on the rear ---it is inevitiable
The front is ok ....maybe a small bit of toe out (to keep the steering taught)
whereas the back is a totally diff story
firstly we are dealing with a 5 link multi adj sus set up
which means that the boys at honda have been getting paid big money to come up with the best solution for the lads that get it wrong.
which is good---for my mum.
now how do you improve on a set up that has millions invested on it?
fact is you dont
you attune it to your driving preferences-.
so what have we got so far ,
as far as i can see there are 3 choices
1.be a mummy ,drop the kids off to school,pick up the shopping and never respect the tsx for what it is and trade it in in a few yrs when the newer model coms out.
.2.get your few quid together and get it lowered ,stiffer rear roll bar and wala one of the best handling saloons on four tires (and i haven't even started on the engine yet).
3 get paid to make it into a race car ie full sus set up chassis rewelding lowerd to a speed bump defying height strip it out and give it all the bells and whistles.

unless you have got a 100,000 to spare i reckon the most of us are going to fall into the 2nd position. so that leavs us with the conundrum ---softness OR stiffness
now AS i dont want to wake the kids before they get to school and i still want anyone who gets in to say that it's nice and comfy -yet i still want to nail it on that flyover on the way home and the 2 miles of nice country (but ruff) roads on the way home.ie handling with comfort are my main priority .
so what was i to do i wanted it to handle as good with 2 adults in the back as it does on its own,so i started measuring things and swing movements.
Firstly the rear you are dealing with a 5 link independant suspension set up on both
sides,
what this means is if you were any good at trigonometery means that you simply cant get the sufficient adjustability by just moving one point(ive seen some kits that offer just the 1 adjustabe parameter which just doesn't work because there are 4 links arguing with it.
so that leaves us with a certain brand with allows us to adj the 2 bottom bars,
which is really good for us --meaning
adj----camber
adj ----toe
what more do you want
if you take a pentagon which ha 5 sides ,you cant move 1 without affecting the other 4 sides ,that is the kind of sus system that we are dealing with,so we infiltrate by buying 2 adj arms which gives us the freedom to adjust the toe and camber
so the best advice after all that and from experience
is
lower the car by 1.5 in all round.
the front will need a small bit of adj (depending on driving style)toe it in for quick corners (.5deg) but a wafty feeling around 120 will be noticable.tho if that doesn't suit toe it out abou half a deg for a nice stable feeling up through the gears and a nice planted feeling at 120mph.
The back is a diff story.
like i said its a 5 link independant sus were dealing with,
meaning u cant just adjust 1 parameter without moving the other 4solid links unless u buy the 2 lower adj arms,
what this does for us is that it gives us the freedom to adj every perameter(good or bad)to our liking
from what ive found
a deg in toe causes the back to follow ,like whenever you go over a rut you have 1 side of the back going through the rut ,a slight loss of traction for a split sec and the other side then tries to steer towards it (not a nice feeling)
so i went back and got the back toe'd out a deg,
Good
felt alot more stable in between corners but it felt like the back was always just about to let go .
so that leades me to believe that the best set up fof the accord/tsx
with a 1.5 drop all round(taking tire life into account)is
front toe out .25 a deg from std
rear -keep it as straight as you can ie camber/toe
You can stray from this if you like just dont forget that the chassis you are dealing with is 1 of the stiffest chassis you can buy on the market today so try to keep the back as straight as you can ie
camber -.5 deg
toe 0.0
i know its fairly uninventive but if you have a set up that works better for everyday driving lets see it
 
#55 ·
Can someone answer this question for me? A guy on Honda-Tech asked and I really have no idea. Thanks

"I have been throwing around the idea of trading out the B for a K in my R. i saw your bay shot in the spoon thread. if in fact its your bay. I was wondering if its possible to do maintenance on the motor without completely removing it. i notice the timing chain is very close to the shock tower. changing out cams/chain or any type of work on that side of the motor seems inmpossible without dropping the motor. is this assumption correct?"
 
#57 ·
what about the k24z3?? does this conform to the k20a3 rules too?? great information....i thought my k24z3 has vtec around 3500 rpms. this engine doesn't seem to comply to what you stated above, or in the 1st post....
 
#58 ·
heyy i know this is not the place for this question but i cannot post threads for some reason so hopefully someone will help me out. i have a k24a1 motor i plan on using stage 2 brian crower cams. i was wondering what numbers i could expect out of this setup? also with a setup like this do i need to use k-pro? i know kpro is always recommended but do i need to to work. i plan on purchaseing kpro when i begin to piece together my custom gt35r turbo kit. thanks
 
#65 ·
Not if you have a Type R :worship:

Speaking of, I couldn't really find much on the engine in my car? Being the JDM model it's good for approx 215hp and revs out to 8,500rpm but does it use i-VTEC or real VTEC? I ask because it doesn't seem to TEC as hard as my old B18cr used to
 
#66 ·
i-vtec IS real vtec,only better


the reason it does'nt seem to "tec" as hard is it is a much smoother engine. If you were to tune the vtec crossover to a higher rpm and detune the mid-range a bit K-series vtec would hit just as hard as b-series vtec..but fortunately we have the better tuning from the factory and we have a much better midrange.
 
#69 ·
the K20Z3(originally found in the 8th gen civic si) is drive by wire,there's only a wire that branches off the engine harness that goes to the throttlebody.
 
#71 ·
once the Z3 is in another chassis you don't have to utilize the DBW,you can bolt the correct throttlebody on and the cable bracket and be good to go. Yo
 
#72 ·
I have a question, I'm new at modding engine so don't laught at me...
I currently own an Acura Csx with the K20Z2 engine and auto transmission.
I was wondering if I could swap a k20A type r engine but keep my transmission... I know someone who currently sell only the engine.
What would I need? Is it feasable?
 
#76 ·
K20 need help

Hello guys I hace an ep3 stock motor k20a3 and my car won't pass 4000 rpm I was digging about what could be wrong with my car so I did my homework and it seen to be some problem with the oil pressure I already change my oil y change the vtec selenoid twice I even change the conector and still my car won't pass 4000 rpm the strange thing is that sometimes he wakes up normal and after 1 day it goes again with the problem si I don't know if something it's broken for good I don't think so because then it would never pass 4000 but some days he does do you guys use to have this problem or do you guys have something that it can help me?
 
#78 ·
All good time!
My question is on replacing the camshaft on к20а. I have a motor к20а 160л.with. honda stepwgn . Can I approach the camshafts from Honda Accord cl7 what is the difference between phases, angles? CAN THEY BE DELIVERED WITHOUT ANY FIRMWARE, IF NOT THEN WHY? We need a professional answer. Thanks in advance.
 
#81 ·
2002 K20A...K20A...04 -...05
The year is to unprecise, sorry.

My guess: on a higher probability these are different cam sets. The first must be a 14110-PRC-000/14120-PRC-000 and the donor engine is likely a 14110-PRC-030/14120-PRC-030. The last part number set has a revised intake cam lobe profile and need a slightly different calibration.
 
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