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Engine Mods

Chris.

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Engine Mods

Honda's K20A engine is a technicle marvel. Pumping out almost 110 bhp per litre (in jap tune), from just two litres. Not only does this engine feature multiple cam profiles (vtec) it also has variable intake cam timing allowing excellent low down torque (unlike the s2000).

THe UK CTR has a "detuned" version of the K20A engine -the K20A2. The UK CTR produces less power, but better torque. It does not rev as high and also has a more restrictive emissions system.

The K20A2 also differs internally, having less wild cams, lower compression pistons, lower-rpm optimes intake tract and the absence of a slip differential. It also has a lighter flywheel.

The K20A2 runs a little rich in stock form. This means that increasing intake efficiency can improve power. Cold air intakes work well as they do not suck in under-bonnet heat. Short ram intakes benfit from heatshields or cold-air ducting.

The aforementioned intakes can seem to reduce throttle response. Using a sealed cold airbox gives you excellent throttle response and more power. You won't get more than 10 bhp with a CAI/airbox if you're lucky.

The K20A2 exhaust is quite good, and replacing it won't help power much at all. You will need a larger diameter if you plan to tune it further though. 2.25 to 2.5 maximum unless you want to use forced induction... Good for about 5 bhp

The manifold and cat are very restrictive. However a decat pipe won't help that much. You need a proper longtube manifold which replaces the cat. The UK car must meet stricter emissions laws for 2005, and loses power as a result. Using a manifold will make from 10-15 bhp.

An ECU retune is probably required after the manifold to account for increased scavenging. All in (intake/manifld/exhaust/ecu) will leave with about 220-225 bhp max.

Uprated cams which feature higherlift and duration will help a lot from here on. Jap J20A cams will increase bhp (with ecu retunes) to about 235-240 bhp. TODA spec A improve on the K20A cams to 250 bhp and have better torque from low-mid revs. Cat Cams 902 have even better low down- but lose about 5-10 bhp compared to TODA As. TODA cams also require stronger valvesprings to allow a safe 9000 rpm re limit.

You can then help breathing a little more by adding a jap intake manifold and a larger throttle body. Makes a small difference and increases high rpm efficiency.

Getting over 265 bhp on a stock head in naturally aspirated form is going to be difficult. None produces cams at present which take advantage of cyl head work. Besides, there is no more room on the piston to accommodate bigger cams. From here its expensive forged pistons and the like...

That's 221 bhp per ton on a CTR

THe mods also increase torque by about 20%. Coupled with CTRs short gearing and light weight, makes this a very rapid car. Addition of a lightweight flywheel helps a lot too.
 
Awesome thread thanks, some great info in there. Fancy doing a similar review of the B16a engine?? :lol:
 
I'll do one for wheels at some point - if you want, as a lot of pics have disappeared, and there is a lot more material to sample/showcase via google etc.
 
I'll do one for wheels at some point - if you want, as a lot of pics have disappeared, and there is a lot more material to sample/showcase via google etc.
Sure mate. :)

Offsets and sizes can becaome quite confusing for people who don't really know much about wheels so it'd definitely be useful.
 
Quick introduction to: Bolt on N/A mods


Part 1: Induction

The following information refers to either aftermarket or OEM parts that can be bolted to the K20 motor in the UKDM CTR. Engine internals such as: pistons, rods, valves, and cranks for example, are not considered ‘bolt-ons’
This sticky is by no means comprehensive; it is designed to cover the basic theory behind what works and the alternative component options.
NOTE: This is not a sales pitch, vendor names and manufacturers can be looked up on Google.



Intakes
Usually the first stop, and rightly so, replacing the stock intake system for an aftermarket item provides great gains on the K-series. On a stock car between 3 – 9hp improvement is possible. Options include:


Short Ram Intake (SRI, under the bonnet open cone / panel)
Pros include ease of fitment, snappy throttle response, and great sound, but can ingest warmer air from the engine and increase intake air temperature as a result.
AEM-24-6105C.jpg



Cold Air Intakes (aka CAI or long arm intake)
Provide a good volume of cold air, sound great with the open cone and make good power. The only drawback is the cone is placed low down behind the front bumper and can be exposed to water if the car is driven through deep puddles; luckily various bypass valves and splash proof covers exist on the market to remove the risks of water ingestion by the CAI.
INJ-RS1476P.jpg

INJ-SP1477P_1.jpg


Carbon or Kevlar Airboxes – externally fed type
Replaces the stock airbox and receives cold air from behind the bonnet via scoop or a feed from a location close to the front of the vehicle. Good power and minimal risk of water damage but less noise (take this as a pro or a con as you see fit), often the most expensive variety on the market due to the choice of material.

thumbep3_airbox.jpg

Civic-type-r-install-b-small.jpg


Aftermarket Airbox

Simply replaces the stock airbox with a smoother poly or carbon item that has less internal restriction. Very low noise levels, higher cost and lower power improvements.

sstp_0807_12_z+2002_honda_civic_si+mugen_airbox.jpg


Velocity stacks
Can be added to most tube based SRI’s and CAI’s to speed up airflow through the intake and improve power and volumetric efficiency.

vs300600_5.jpg


Throttles
The factory throttle body diameter on the UKDM K20 is 62mm. The stock throttle is considered adequate until all of the other bolt on’s have been implemented. It is then common to see between 3-6hp with the right tune.
There are two main upgrade paths for the throttle, OEM overbore or Aftermarket big bore. The first option can provide 2mm more diameter at the outlet (64mm) tapered to a larger opening of around 68mm. This is a good option a mild NA motor and speeds up airflow through the venturi effect. Big bore throttles tend to start at 70mm and go upto 74mm (or even larger for dedicated drag racing manifolds) These throttles are great for more race focused motors that need the extra air but can affect part throttle and low speed drivability on the road (they are very sensitive!)
The throttle is connected to the Inlet manifold and often requires that the port is matched to the size of the throttles outlet.

in_3.jpg

skunk2-k-series-throttle-body-70mm.jpg


Inlet manifolds
Thanks to the various K-series sub-types in other vehicles and markets, there are a number of OEM Inlet manifolds that can be swapped onto our motors that will make additional power & torque (as much as 12hp peak in some circumstances)

RBC
Found on the Accord EURO R, needs to be modified to fit but is often sold pre-prepared. Good £ / hp mod that works well on even a stock vehicle. Unfortunately requires chopping of the slam panel and can interfere with the bonnet stay due to its length and height. Also It can move the positioning of your air intake so that it might foul the battery tray or gear selector on the gear box.

rbc-intake-manifold.jpg


RRC
Found on the JDM 8th gen Tyre R, same story as the RBC – it requires modifications to fit. The exact steps required are outside the scope of this article! The RRC is argued to make even more power than the RBC thanks to its runner profiles.

rrc-intake-manifold-package.jpg


PRC
Found on the JDM Integra Type R. Less hassle to fit than other options but produces less power.

3353075290_bbc5372492_o1.jpg


Aftermarket
Often fits 1st time with a little modification to water routes, makes similar power to the RBC but costs more than the OEM options.

skunk2-k-series-intake-manifold.jpg
3c536079268ee780a3ec839350864d61.image.150x112.jpg


Poly gaskets
Proven way to keep intake temps down and avoid power loss – also quite cheap.
IMG_0421.JPG
 
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i have a question is it safe to run rrc / rbc on k20a2 with hondata airbox mod without tuned ecu (kpro - k100)?
 
I'd say so as long as you keep the stock manifold and car. As always, it's a safe bet to get a dyno run done and get the AFR read.
 
Whats the furthest you could go safely without ecu? I don't mean optimal power gains, just safe fuelling etc
 
FN2`s can gain 7hp~10hp through the entire range using an EP3 oil pump. Fact proven on many cars. Never understood how and why, but that`s true.
 
FN2`s can gain 7hp~10hp through the entire range using an EP3 oil pump. Fact proven on many cars. Never understood how and why, but that`s true.

It's an FD2 oil pump that's used bud.

The reason is you are changing the oil pump for one that does not have balancer shafts in it. There is less mass for the engine to turn, so it reduces parasitic loss.

This is my car when it had the conversion done when it had light breathing mods. The Flashpro tune was left unchanged.

Dyno180111.jpg


Decent uplift in torque too.

This is a picture of the difference in the oil pumps borrowed from Staffs Deltic's thread.

20130404_125556_zps6bcfcde0.jpg
 
No, the EP3 pump doesn't have balancer shafts either.

It was just something Honda introduced on the FN2 to make it more "refined."

The FD2 pump is supposed to be good to over 9k without cavitation though, so I suppose that would be the only benefit.
 
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