[mattkosem]

I've got a K20Z3 in my EG at the moment, with some uncertain lifespan concerns. If it ends up poorly, I'll likely want to consider a K24. An issue I had, right out of the gate, with the Z3 setup was the intake manifold to hood clearance though. With the RBC, I'm stuck with the K20 in the lower holes and still had to make some adjustments to avoid the hood.

I noticed that this VTEC Academy video series put their K24 into the top holes though:

This was with an Accord engine with considerably less power than I'm looking to have. The fact that the intake manifold has the angle it has makes it a non-issue for hood clearance, and the rest of the fitment challenges are apparently sortable with hood trimming. Nevertheless, this RAA manifold apparently has a low ceiling for power and isn't really an option as a result.

Someone was nice enough to make a page picturing most of the options side-by-side. It looks like all of the Honda manifolds have the same problem. The Skunk2 manifold doesn't tilt upwards, but it's tough to tell if it needs to tilt further downwards to clear. Anyone running one of these on a k24 on an EG in the top position and clearing the hood?

--Matt

 

[mattkosem]

Evidently, the RBB has similar fitment to the RAA but flows better. There appears to have been a SuperStreet article with side by side dynos of it and the RBC, but I can't for the life of me get the images to load...even in the wayback machine. 🤦 It is seemingly showing it having better midrange than the RBC (no surprise with longer runners) and who knows what elsewhere.

Some folks over here had a discussion, and it seems like the theory is that a k24 will make better power on an RBB than an RBC until maybe 7-8k, which seems like a fair limitation for a k24 that's expensive to rev past 8k anyways.

--Matt

 

[Kowalski999]

For your case maybe it is better to use modded RSP manifold. They pop up on ebay for 150-300$ price range from time to time (used).

 

[LotusElise]

There appears to have been a SuperStreet article with side by side dynos of it and the RBC, but I can't for the life of me get the images to load...even in the wayback machine.

K20a.org has all and more: Katman's Dyno Adventures! | Honda / Acura K20a K24a Engine Forum.

 

[mattkosem]

For your case maybe it is better to use modded RSP manifold. They pop up on ebay for 150-300$ price range from time to time (used).

Huh, that sure does look like it ticks all the right checkboxes! Thank you for sharing!

K20a.org has all and more: Katman's Dyno Adventures! | Honda / Acura K20a K24a Engine Forum.

Nice thank you!

 

[LotusElise]

Nice thank you!

You are welcome. The S2 Street IM is shorter in depth then the RBC or RRC. Make sure you get the bracket for the RSP IM too (IM to block bar), I've seen a few broken RSP runner, especially on light cars, which tends to oscillate torque at lower vehicle speeds and have jumping tires, hunting for grip.

 

[mattkosem]

After finally finding a pic of a K in an EG with an RSP I'm not sure the RSP is gonna fit my car. It looks pretty close to the front there, with no rad at all, and I've got a huge full width rad in my car. Another pic seems to suggest the same, as does this one. The manifold itself might fit by a hair but, even if it did, the TB and TPS seem like they wouldn't.

It definitely seems to sit a bit lower, but that sucker is huge! Seems like I'd have to switch to something like this for it to fit.

I reached out to VTEC Academy and they said the Skunk2 pro intake manifold makes decent power with good clearance.

 

[mattkosem]

Well, thanks all, I think that's plenty of options. Seems like that leaves me with:

1. The cheap option - RBB - $100-150 - apparently able to support ~250whp on a k24 with some porting work
2. The middle of the road option - Skunk2 Pro Series - $400-500 - apparently able to support at least 250whp as provided
3. The best option - RSP & tucked rad - $700-1000 - apparently able to support at least 260-270whp (and maybe nearly 300whp with porting)

The HP limits are obviously caveated with the right motor and tuning, and are from varying dynos probably with varying corrections, so take them with a grain of salt..but all are seen on multiple data points. I didn't look super hard on the Skunk2, so it may have more headroom than stated, but there are lots of >=250hp dynos on various K motors with it. 1 and 3 appear to trade some midrange for top end, but 3 seems to be a proven option for a good top end either way. There's little chance in me spending enough to get past 250hp either way, so they're probably all viable.

We'll see what this season holds once the snow is gone and tracks are open. All 3 of these seem like potential ways to get my k20z3 into the upper position, too, which is a nice option to have.

--Matt

 

[LotusElise]

The best option - RSP & tucked rad - $700-1000 - apparently able to support nearly 300whp with porting

The RSP has the biggest clearance demand of all. Especially if you lay back the engine over the 9° standard engine vertical axis angle (e.g. CRX enginebay to win more hood clearance). The depth of it is 278 mm, better distributed as lowered at the most far point. The S2 Street IM is almost 30 mm shorter and can compete almost with the PRB/PRC. The RSP IM is quite good, but I never saw it supporting "almost" 300 whp. I am interested in an example.

 

[mattkosem]

The RSP has the biggest clearance demand of all. Especially if you lay back the engine over the 9° standard engine vertical axis angle (e.g. CRX enginebay to win more hood clearance). The depth of it is 278 mm, better distributed as lowered at the most far point. The S2 Street IM is almost 30 mm shorter and can compete almost with the PRB/PRC. The RSP IM is quite good, but I never saw it supporting "almost" 300 whp. I am interested in an example.

Clearly not typical. The lion's share of better ones are mostly in the 260-270 range, but there are a couple out there.

Prototype Intake Manifold & Header Testing on K24...

Ill start this off with the K24(2381cc) i built a while back... it was one of the motors used in this test... click the thread below for more specifics... basically its a simple build k24 http://forums.clubrsx.com/showthread.php?t=716776 1st Graph TEAL PLOT - Ryan fitted a RSP intake manifold...

www.clubrsx.com

RBC vs RSP(euro type R) intake manifold

Jaas but let's compare oranges to oranges. Ported RBC on my setup made 301HP/301Nm. We can assume on the RRC basis that porting gave 13HP and 8Nm. So Non-ported RBC would be like 288HP and 293Nm. Still - same setup, same dyno, only change was manifold. Dyno had DIN 70020 correction. I have rev...

www.k20a.org

There are a couple different >300 dynos on the first one. The second one is anyone's guess. The chart doesn't indicate correction or specifically say wheel. As with all dynos posted on internet forums, take them with a grain of salt. I wasn't attempting to suggest that any of these figures are common, just assess the peak figures I was able to find after a few minutes of investigation on each.

--Matt

 

[mattkosem]

Looking out at other available options, the Skunk2 Ultra Street also seems like it might be an option too. It doesn't seem to tilt down quite as far as the Pro Series but, from what I can tell from pics/videos I'm able to pull up it seems like the plenum might sit nearly an inch below the RBC too. 🤔

Pracworks seems to make a special 20° version of their manifold meant to deal with this situation too, but it seems like it may have clearance issues with the water pump on a K20.

Either of these options looks like it would require something like this, because of the z3 situation.

 

[yaggs]

Slightly off topic, but this is a really good informative video for spotting fake dyno results. Especially for those that are unfamiliar with them.

 

[LotusElise]

Slightly off topic, but this is a really good informative video for spotting fake dyno results. Especially for those that are unfamiliar with them.

This is always a good point to look at it, but please be aware of hp/ftlb, hp/kgm as well as hp/Nm or PS/Nm have all crossing point at different engine speeds. This is because power is only a non-measureable magnitude, which is calculated on many ways: 1 hp = 1.34/1.36 PS = 0.72 kW and as well as the torque, which can be measured has a different correlation to power: 1 ftlb = 1.356 Nm or 0.138 kgm. The crossing point is mathematically easy to calculate, you just calculate the engine speed where Torque and Power equals to 1. Following crossing points are available:

• hp/lbft = 5255 rpm
• kW/Nm = 9549 rpm
• PS/Nm = 7022 rpm
• hp/Nm = 7126 rpm
• hp/kgm = 699 rpm

The balance point is simply the unit correction multiplied with the residual factor 1/(2 Pi), for example engine speed = 60 * 1000 * 1 / 1.34 / 1.356 / (2 x pi) for the hp/ftlb example as the power and torque units has to be corrected to the SI units Watt and Nm. You can be more exact if you use the SAE definition of the kW into hp ratio.

Cheating with torque curves has manifold options, the upper one is a beginner failure, to easy to catch. The one you can't see without relation to references is the factorized or offsetted one. BTW, the used correction norms, like the SAE J1349, DIN 70020 or ISO 1585 are all different in a ballpark which can be significantly different. Not all use the same reference point, so even if you know the norms for correction of the figures measured, there is still room to play with. Comparisons should be done only in one room: norms, dyno, weather. All other has to be seen with a bigger tolerance .

 

[mattkosem]

Thanks for sharing. 👍

Personally, I take any dyno I see that doesn't show hp (or cv or ps) and lb-ft, show them crossing at 5250rpm, and declare the correction with a grain of salt right off the bat if. I know, yank attitude and yank units, 😂 they are pretty pervasive either way. Neither of the examples from the RSP have the details I "trust". The one from the RSX form is close, but there's no 'wide view" of the RSP setup so it's a meh in my eyes 🤷.

I tend to only apply such scruples to situations where I actually plan to buy something, and tend to want to see it comparing to something I already have if possible...and both on the same dyno on the same day. In this case I'm not immediately planning to buy any of these things and was just really summing up a sweep of largely unvalidated data points. I'll adjust the post above so random googlers don't get the wrong idea.

The video seems to have missed an opportunity to call out that different brands of dynos, even with the "same" correction, may produce numbers that disagree.

--Matt

 

[Kowalski999]

This is rsp vs rbb on stock cl9 k24a3.
Before it had reflash and some crap cai induction and after is with swap to rsp manifold.
Went from 207chp to 216chp.

 

[Kowalski999]

This is one cl9 with same parts as mine regarding engine just have rsp vs my china ported s2 pro street.
B.s. Cai vs my custom air box
Trashy Dc sports header vs serge header (weaponR copy)
Some b.s. 63mm exaust (modified stock it think with 57mm twin exit ) vs my 70mm single exit.
254chp vs 229chp

 

[Kowalski999]

Regarding dyno charts that are on the internet, I did a lot of research... stuff that I see in USA on dynos that are spitting WHP numbers I hang that on cats tail. That means nothing to me.
This is one example why it is useless for any data comparison

Dynojet 15% over mustang and dynapack 10% over dynojet... lol you can end up with 20-30% difference in result when you compare this dyno vs that dyno.

What I want is to have data from dyno that can measure Engine HP and I want to have multiple stock cars on that dyno.


date: 04.2019 cl9 60k km vs date: 06.2018 cl9 300k km

Date : 07.2019 cl9 250k km / date: 08.2020 cl9 90k km

With this dyno you can use data for comparison and testing modifications.

Also I have 3 seen prints from 3 Bapro dynos for stock fk8, one in Serbia made 299hp, Second in Belgium made 301hp and 3rd in Austria made 304hp.
3 different locations / 3 different cars / 3 different Bapro machines / 3 different circumstances regarding ambient temp/humidity/kpa. When you see that than you can be certain that that company can make good dyno machine and that data can be used.

And than I see things like this... Stock cl9 making 201chp and 208chp after reflash... In a dream land vs 190chp stock and 198 chp reflash. Not to mention lack of accuracy of power curve.

I'm tuning engine not wheels and there fore I want to see data that my engine is making and I have that data for all of them mods lol.

 

[mattkosem]

I contacted the respected local Honda tuner I'm hoping to work with next and explained my situation and goals. I figure I'll either keep going with a k20 and try to get it in the top position of the mounts, maybe picking up a bit more power, or end up with something new and still want to fix that clearance issue. Either way, they'll ultimately be the ones tasked with implementing the tune to reach my power goals so I figured just asking what they'd prefer and have experience with would be better than throwing parts at it myself and potentially ending up with something they don't prefer.

We'll see what they come back with.

--Matt

 

[mattkosem]

Haven't heard anything back so far.

In other news, though, @katman suggested that fitment arcs lower than an RBC/RRC...more like a Pro Series over here: DC2-R K20A with Skunk2 Pro Street Manifold

If I get ghosted by the tuner, maybe picking up one of them will be my next move.

--Matt