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RSX K24A Swap

400 Views 25 Replies 3 Participants Last post by  gtimportfanatic
Hello all! I’ve decided to finally start my build thread. My intention is to finally give something back to the community, as I’ve acquired a lot of info from here. My goal is to document every step in the process of swapping out the stock k20a2 in my 03 rsx type s with the JDM k24a performance 3-lobe engine. I anticipate using as much pics as possible. @LotusElise What is the preferred method of uploading pics? Attachments or full res in the post? @Them Witches Just wanted to say welcome back and I look forward to your feedback/input!

WHY I’M SWAPPING:

The k20a2 is approaching 250k mi and has seen better days. I had to rebuild it last year. What a learning experience! Thread: Service/Rebuild after low oil pressure K20A2 stock

The engine is currently running great, but I question how well the head was rebuilt back in 2020. There were some things observed that I didn’t care for: valve seats redone with low standard and some valves not sealing perfectly (with new valves). I take the car on long trips frequently, so I worry about the longevity of the worn engine. This, plus the need to do a project, has led me to do the swap. Also, the 2nd clutch has passed 100k mi so, you know… while I’m in there lol.

As a DD, my rsx should benefit from easier drivability with the beefier torque. I hope this overcomes my longing for a high redline, which drew me to this car in the first place. I feel this is one of the best cars for a mix of driving styles and still having practicality. It seems to be one of the last years where the driver has a direct analog experience while still being effective/comfortable as a DD. It’s easy to cruise around with but it makes you work for maximum performance, which I like. This keeps the car exciting and rewarding. Later Honda models became heavier and heavier with more numbing electronics and horrible rear visibility/blind spots. Also, idc what the benefits are, I hate the DBW throttle experience. I decided years ago that I would hang on to my rsx for as long as possible.

WHAT THE SWAP WILL BE:

-Mostly an OEM build since longevity is important to my DD
-JDM K24A 3-lobe engine
-Stock RBB intake manifold
-RDX injectors
-RSX-S accessories including: PS Pump, Alternator, Starter, A/C Comp, Belt tensioner, Crank Pulley, Water Pump, oil cooler
-RSX-S oil pump, oil pump chain and guide (I debated a long while about leaving the stock oil pump, but if I don’t like the type-s pump I will have another project, right?)
-RSX-S oil pan
-Stock RBB2 head, stock cams
-RBC VTC gear limited to 40 deg
-Hasport 62a engine mounts
-09 CSX type S Transmission (107k mi). Canadian Civic Si equivalent with LSD and 4.7 FD, CSS for speedo
-Aftermarket exhaust

There will be some goodies/upgrades here and there, but I will reveal those as the process moves along.

I will post some engine & transmission pics soon. I’m not 100% sure when I will take on this build, but it will be before fall. I have done some things on the engine stand and will post about that soon!
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Very nice move to post here your project @yaggs. Very nice!

What is the preferred method of uploading pics?
Each member has a free amount of storage, premium members have more, mods have even more more ;). You can use a cloud and implement here the link to it. Just set it up properly.

JDM K24A 3-lobe engine
You came from the best engine basis and go now to average? Again one lost to the dark side of power 😇. For a DD it is a good basis, for a race car the K20 is the much better. Longlivety is greatly influenced by engine speed. A 7600 rpm limit would support that.

But to be honest, the fun of the K-series begins at 7000 rpm. That's way I would always prefer a K20 over a K24. Power is a number, I've learned racing on a 60 hp car with easy 700+ kg, giving 12 kg/hp. I've learned a lot regarding how to drive and how to setup suspension to squeeze out more. Any Honda K-series (iVTEC, performance) has a better weight-to-power-ratio. Actually I drive a 12.7 kg/hp (TC) car and have a 2.4 kg/hp (NA) in a far far away garage. Don't miss it really, I am more keen on developing that stuff then driving it, maybe I hide it not to develop fun-related emotions, which create further demand of wanting it to drive ;). Anyway, I am thinking of K-swapping a Miata chassis, something less extreme, 3.5 kg/hp (NA) or so. Of course more low speed torque is fine, but the experience, coming from an average torque, transiting VTEC and screaming to 8600+ rpm is really make me smiling from ear to ear. We will wait and see when you start thinking about pushing the redline ;).
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You came from the best engine basis and go now to average?
I expected this reaction. I've had my fun taking her to 8500k rpm. There is no problem with the k20a2 so i will hang onto it. I can always go back if i strongly prefer it over the k24.
We will wait and see when you start thinking about pushing the redline ;).
I've come to terms with the low redline, in theory anyway. I've considered that 95% of my driving is in the low to mid RPM range so I will actually see real world benefit from the swap. The plan is a 7500 rpm limiter but ideally shifting shortly after 7000 rpm since in stock form, power tapers quickly after that.
The urge is certainly going to be there with a tach that looks like this.
Speedometer Motor vehicle Gauge Measuring instrument Vehicle

I might swap out the cluster to the base model, lol just as a reminder.
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10
Like I said, this will be a picture intensive thread. Here are the pics from JDM of California. I talked on the phone with David at length for 20-30 mins. Very knowledgeable group there. I was initially interested in a later model K24 (06-08) because of the better cams/head. Ultimately, I couldn't justify paying $1200 instead of $800, so I went with the first gen engine. He promised to pick the "cleanest" k24, and I feel like he did not disappoint. Total cost + shipping was $1115. I ordered on a Saturday afternoon and on Monday afternoon I was sent these pictures with the cold compression test. They shipped the following day. Top notch service.
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Engine has approximately 60k mi
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I expected this reaction.
Did I wrote about that before?

I might swap out the cluster to the base model, lol just as a reminder.
Yeah, you need one of these 400 cui capable tachometers.

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Did I wrote about that before?
Lol, only every chance u get!
Yeah, you need one of these 400 cui capable tachometers.
Ok, that is actually quite funny. Well done sir
...so I went with the first gen engine.
Could you please measure the IM runner ID's and length? I have a K24Z3/Z7 IM and wonder if that is not different. The upper part has 280 mm centerline length and 45 mm ID. The lower part is different to yours, actually I haven't this.
Could you please measure the IM runner ID's and length?
No problem, I'll do it in the morning.
I know you can write songs, but I can draw pictures! Don't be jealous of my mad MSpaint skills


Injector base in currently on the engine but i measured 155mm centerline to the best of my ability.
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Wow, that is really knowledge increasing dictionaring stuff. Many thanks for that.

I know you can write songs
Do I? Did I? You made a great job, the basic message is sharp and clear! That means we have here a 42 mm runner with an length of X mm (X is what if you throw a thread in it with an weight on the short side and watch it coming out at the TB flange (flange to bell mouth length)?

Thanks for the upper manifold runner length. I know they are quite different. But I assume there is a pretty cheap upgrade available, to get more power out of that.
with an length of X mm (X is what if you throw a thread in it with an weight on the short side and watch it coming out at the TB flange (flange to bell mouth length)?
It seems i didn't provide the appropriate information. I'll head to the garage in a bit.
But I assume there is a pretty cheap upgrade available, to get more power out of that.
Did you have such an option in mind?
I intended to keep this manifold as it appears to have good low/mid torque. I'm not looking to sacrifice this for more top end power.
Solve for x:
x = 188mm

Keep in mind this doesn't include the injector base (155mm).


I used string with a washer tied to it, marked each length, and measured with washer hanging like a plum-bob (to keep same tension). Measurements may not be exact but should be close
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Some transmission pics (from ebay listing):



Comparison of 'new' trans vs old:

At cruising speed of 80mph, the longer 6th works out to be about 100 rpm less, even with higher FD. 4.7 final drive should work out to quicker acceleration, all other gears equal. Plus there's the factory LSD!

This trans will need some mods to work with my rsx shifter and older VSS sensor. We will cross that bridge when we get to it.
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Very nice move to post here your project @yaggs. Very nice!

Each member has a free amount of storage, premium members have more, mods have even more more ;). You can use a cloud and implement here the link to it. Just set it up properly.

You came from the best engine basis and go now to average? Again one lost to the dark side of power 😇. For a DD it is a good basis, for a race car the K20 is the much better. Longlivety is greatly influenced by engine speed. A 7600 rpm limit would support that.

But to be honest, the fun of the K-series begins at 7000 rpm. That's way I would always prefer a K20 over a K24. Power is a number, I've learned racing on a 60 hp car with easy 700+ kg, giving 12 kg/hp. I've learned a lot regarding how to drive and how to setup suspension to squeeze out more. Any Honda K-series (iVTEC, performance) has a better weight-to-power-ratio. Actually I drive a 12.7 kg/hp (TC) car and have a 2.4 kg/hp (NA) in a far far away garage. Don't miss it really, I am more keen on developing that stuff then driving it, maybe I hide it not to develop fun-related emotions, which create further demand of wanting it to drive ;). Anyway, I am thinking of K-swapping a Miata chassis, something less extreme, 3.5 kg/hp (NA) or so. Of course more low speed torque is fine, but the experience, coming from an average torque, transiting VTEC and screaming to 8600+ rpm is really make me smiling from ear to ear. We will wait and see when you start thinking about pushing the redline ;).
Your opinion of the K24A always gives me a chuckle. We’re entitled to our opinions i guess, but i’ll take my 250+whp and 190+ft/lbs at 7800rpm over a 2liter engine anyday when in a chassis 2500lbs+. We can have another conversation when the vehicle is 2200lbs or lighter lol
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I have race customers which are very happy with their K20 in their 8th Generation Civic. A short calculation of 1250 kg gives me 2756 lbs. I have no issue to push a K20 to 250 whp, I have proven 266 whp and 179 wftlb are possible with the DAMPFHAMMER concept. But these guys I am talking about race with 210-225 whp in these 8th Gen. Chassis, which is 12 lb/whp only. But they do best times on track in their racing classes, so who can complain about it? Success gives you always a good argument ;). If we talk only about straights business, you talk with the wrong guy. The drag business is not that interesting, drag times are more related to money.
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I intended to keep this manifold as it appears to have good low/mid torque. I'm not looking to sacrifice this for more top end power.
I've talk about a improvement in both directions, so to say a cheap overall improvement in torque. But first we need good geometrical data of your RBB IM.
I've talk about a improvement in both directions, so to say a cheap overall improvement in torque. But first we need good geometrical data of your RBB IM.
I went back and did the string measurements on post #12. Let me know if any more data is needed
We can have another conversation when the vehicle is 2200lbs or lighter lol
I have race customers which are very happy with their K20 in their 8th Generation Civic.
I think we all agree that Honda made 2 great engines here. Like anything in life, each item has it's pros and cons. In this case it is quite literally different strokes for different folks (see what i did there). It just comes down to personal preference and application. What might be important to one person may not be important to another. I think each camp can agree that "the other engine is great but I prefer mine." Which is better is a personal, subjective, choice imho.

OPINIONATED RANT AHEAD:
Personally, I just like to keep an open mind and like to experience different things and change it up once in a while. I will have the chance to experience both engines, in their stock form (mostly). Like I've said, I've had my fun with the k20a2 so now I want to try something different. I have a feeling I will enjoy the engines similarly, but for different reasons. I'm sure I will enjoy not having to downshift to make a pass, but I will miss screaming her up to 8500rpm. Better or worse? A personal opinion, not an objective fact.
The track guys will always be critical of every detail as that is the mindset for any racer to squeeze out every ounce of performance possible. Me: I'm just a guy trying out the different flavors of kseries engines. This "which is better" business sounds like arguing over which flavor is better, grape or orange.
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In other news...
I know some of you guys like to see all those red Honda labels all bundled together so here it is:
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I have race customers which are very happy with their K20 in their 8th Generation Civic. A short calculation of 1250 kg gives me 2756 lbs. I have no issue to push a K20 to 250 whp, I have proven 266 whp and 179 wftlb are possible with the DAMPFHAMMER concept. But these guys I am talking about race with 210-225 whp in these 8th Gen. Chassis, which is 12 lb/whp only. But they do best times on track in their racing classes, so who can complain about it? Success gives you always a good argument ;). If we talk only about straights business, you talk with the wrong guy. The drag business is not that interesting, drag times are more related to money.
My experience with racing is not only drag racing, i’ve done numerous endurance racing using K24 powered vehicles. Needless to say, whatever floats your boat, i will never claim one is better than the other, as long as it fits the purpose for the application and does it successfully , idc
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