hey everyone, was looking into buying a 02-05 civic si and was wondering what is the difference between the k20a3 and k20a2 besides one being in the civic si and one in the rsx type s. and i did search couldnt really find anything. just curious thanks.

 

quite a bit of difference
not sure how detailed you want us to get
it's like comparing a v6 stang to a GT

 

a looot of difference. k20a2 has more power.. and it has real I-vtec and not the I-vtec-fuel efficency that the civic si has. But as aco512 said it's like comparing a v6 to a v8..

 

K20A2
• Found in:
o 2002-2004 Acura RSX Type-S and 2002-2005 Honda Civic Type R (EP, European)
• Displacement: 1998 cc
• Compression: 11.0:1
• Power: 200 hp (149 kW) @ 7400 rpm
• Torque: 142 ft•lbf (193 N•m) @ 6000 rpm
• Redline: 7900 rpm

K20A3
• Found in:
o 2002-2005 Honda Civic Si
• Displacement: 1998 cc
• Compression: 9.8:1
• Power: 160 hp (119 kW) @ 6500 rpm
• Torque: 132 ft•lbf (179 N•m) @ 5000 rpm
• Redline: 6800 rpm
o 2002-2006 Acura RSX
• Displacement: 1998 cc
• Compression: 9.8:1
• Power: 160 hp (119 kW) @ 6500 rpm
• Torque: 141 ft•lbf (191 N•m) @ 4000 rpm
• Redline: 6800 rpm

The K20A3 only has i-VTEC (i.e. performance-profile cam lobes) on intake, whereas the K20A2 has i-VTEC on both intake and exhaust. Also, the "i-VTEC" of the A3 engages at 2200 RPM; with the A2, it's ~5800 RPM, ergo real VTEC.

 

what happen if i put K20A2 on my base model rsx?

 

do mean slap an A2 head onto the A3 bottem end or put the whole motor into your car?

 

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.
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).

 

thats exactly what i wanted, i was really wondering why it was less hp and tq. thanks for all the mustang regrences but its a little different v6's and gt's dont have the same motor with less hp. but thanks for the help.

 

keep in mind that although the k20a3 doesnt have the same HP or Torque of its more accurately designated i-VTEC sibling doesnt mean it isnt a wicked fun car to drive.

Just let personal experience in the car guide you. If you like the power output, then its the best engine for you. You can always swap out for another K series engine later if it becomes unbearable down the road.

 

from what i found out if you fully build the k20a3 with forged pistons etc... a3 block is the best choice since it doesn't have oil squirters.

 

im not worried about the lack of hp and tq. was just curious. im not crazy about the rsx looks. i will most likely gonna get an ep3 civic, and i dont wanna go crazy just something fun to drive with good gas mileage ill probably just do i/h/e.

 

Great Post hawaiiancb74!


Ok, but More details needed...

say he wants to put the A2 head on the A3 engine... to get an actual TRUE Vtec -with added Torque...

What are the required steps?
Will he have to replace a lot of peices like Pistons, injectors, ECU, Etc...
i notice the compression is different... will that hurt the bottom A3 half if he doesn't upgrade?


i'd love to know all the details! Thanks

 

It is possible to run an A2 head on an A3 block but from what i've read and found out (you can check clubrsx as they have a thread completely on that) that it's a big pain in the *** but it is possible. IMO to much work just to get the A2 to work correctly on the A3.

 

my mechanic has the swap, and suggested i try it instead of chopping into a turbo- and all the intercooling stuff... its my DD, and i want reliability- but faster!
He said he could squeeze the K24 into this ep3... just harder to do, but more HP!
(i dont know about that?!)

So... where does the K20A or K20A1 motor play in all this?
is that "interchangeable" like the A2? or something completely different?

or is that the Type R- JDM version?
i thought it put out 200HP Stock!

great thread, hope you get the ep3!


Modified by WyldRice at 5:21 PM 6/12/2007

 

K20A
• Found in:
o 2002-2005 Honda Civic Type-R (EP3)
o 2001-2006 Honda Integra Type-R(DC5)
• Displacement: 1998 cc
• Compression: 11.5:1
• Power: 220 hp (162 kW) @ 8000 rpm
• Torque: 152 ft•lbf (206 N•m) @ 7000 rpm
• Redline: 8500 rpm
o 2003-2006 Honda Accord Euro-R
• Displacement: 1998 cc
• Compression: 11.5:1
• Power: 220 hp (162 kW) @ 8000 rpm
• Torque: 152 ft•lbf (206 N•m) @ 7000 rpm
• Redline: 8500 rpm

The K20A is only found in JDM vehicles; the UKDM Civic Type R uses the K20A2.

 

k20A is like the bigger brother of the k20a2 and the k20a3 is like the red headed step child. lol

 

OK, So why all the threads and talk about A2 this, A3 Swap that...

Why dont we all run A1's and go like (the OLD) Nascar...
"as much as you can get out of stock"

if it fits... whats the problem?
is it imposible to find? Cost too much? ...???


Also... Is there a certain HP level / Mod level = where your car becomes "Illegal" for street use" ?

(just wondering... i get in enough trouble! and i dont need an "Excess Engine" ticket if i get this thing over 350hp... )
LOL!

 

Actually people do try to get as much out of stock. Reason everyone doesn't run K20A's is because they didn't come with the cars in the USA and they are to expensive to afford for the average person to just slap in yo car. No there isn't a HP level for a street car. you could make 1k HP (even tho there are already cars that do that) and still be street legal as long as you pass DoT regulations you're good to go.

 

i did find someone who did i think type s cams on a stock k20a3. i was just skimming through so i didnt really read into it looked like it made good numbers something like 200whp with race header and k-pro. is that swap difficult?

 

i think you may have found that one on the crsx forum. To much they had to do to make it work correctly but yes he made something like 200 or something. IMO it is a difficult thing to do but this is only my opinion.

 

another reason is it might cost me 6 grand to get and install and get working a k20a but for the same amount of money i can make my k20a2 king kong and beat the tar out of its older brother, ... as i did , i bored my block and put in ITR .25 over pistons in and now im better than the normal type r k20a, and with all the aother stuff i threw money at i dont even consider the k20a competition as stock.

 

a2 is more powerful?

 

No the k20A is more powerful stock.