Stock IM vs RBC IM

hotdogjohnny said:
That's not quite what I had in mind as weighing in. I know that Vit works like a fiend for his customers, so I'm confused. Does he have upset RBC-swap customers (I doubt it) complaining about his etune, when the problem is the RBC? Did he see RBC swap etunes that revealed a pattern of poor results, drop-outs in the power band, etc., so he decided in good conscience, "I'd better let folks know about this." This is probably what's happened. He saw a pattern emerging, he's an honest guy, so he's telling people, in effect, "Don't bother with this mod."
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There is a pattern, every single RBC car lacks a TON of mid range. It's just not there -- the graphs don't have it, even blatantly obvious by looking at the tune it's not there. There are some gains way up top, but nothing that I would say makes the car "faster".

Bulkybear said:

View: http://youtu.be/r-ql_Iqe8fQ


It looks like this guy gained a bit of power


View: http://youtu.be/N5j4cV0wquo


This guy says he tuned with you @VitViper. Looks like he gained a ton of power. I'm confused :(
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I don't see anywhere there that actually shows he gained any power... I'm sure the butt dyno is the best dyno (but not really).
 
@hey_mikey i guess the improvement i feel would predominately be the throttle response but the k&n also helps in that area. As far as hp increase goes maybe 1-2hp nothing i can butt feel but the response in throttle definitely.

@VitViper said it himself with PRL cold air, zdx throttle body and adapter with rbc you gain approximately 5hp up top but lose 20hp midrange. so whats better 5hp up top in an already low reving 2.4L or 20hp in a motor designed for lower-midrange torque?!
 
@VitViper what about using older generation k24 intake manifolds from previous 2.4 liters could either of those be a possibility for gains mid to higher up?! like the K24A2 thats a great 2.4L!
 
Vit just made it SUPER clear that the RBC mod is NOT the way to go. Thanks Vit for bringing this to light !!
 
So many people have purchased the wrong setup. How sad is it that this issue is now being brought up after these Si's being out since late 2011
 
VitViper said:
There is a pattern, every single RBC car lacks a TON of mid range. It's just not there -- the graphs don't have it, even blatantly obvious by looking at the tune it's not there. There are some gains way up top, but nothing that I would say makes the car "faster".



I don't see anywhere there that actually shows he gained any power... I'm sure the butt dyno is the best dyno (but not really).
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I understand the butt dyno is not accurate and can sometimes just fool you. But in that second video where in the description he said you tuned him he spun all of 1st, 2nd, and some of 3rd like nothing. Either hes lying and has more mods than he states or his tires are gone because my car does not do that. I spin 1st and scratch 2nd on most roads.
 
Our '04 Honda Element also uses this motor in some vtec form/165hp. Has a non-RBC manifold. Has good low and mid range power.
 
I don't know if that will be worth it. I think we got a good manifold stock. Just get the intake and throttle body.
 
Nah if the rbc can boost hp by that much even if it looses midrange then our intake is restricting. We just need one thats built for our motor that provides those increases and doesnt starve our midrange.
 
Bulkybear said:
Nah if the rbc can boost hp by that much even if it looses midrange then our intake is restricting. We just need one thats built for our motor that provides those increases and doesnt starve our midrange.
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yeah the stock manifold is probably more restrictive than the rbc, but without resorting to a variable-length intake manifold, you'll have a hard time finding one that'll be good for both midrange and high rpm because what's good for one isn't good for the other. as you mentioned, high rpm flow is best with short, fat runners that reduce restriction to get air to the head as fast as possible, but such a configuration sucks for midrange, which is probably why the RBC loses torque. you can bolt on a lot of different manifolds, but finding meaningful gains will probably be more luck than anything until someone properly designs one for this motor. and even then, i still think they'll find it hard to make large gains because the stock manifold is pretty good to begin with.

as far as multi-stage manifolds go, a lot of manufacturers still use multi-stage manifolds with their performance motors. but nowadays they're more likely to use variable valve timing and lift systems like vtec to help flatten the torque curve. instead of the added size, weight, and complexity of a multi-stage manifold, they can just get more flow (up to a point) by opening the valves longer and wider to make up for the flow restriction that would normally come with longer runners. that's probably why honda doesn't really use them even though they've been used on other k24 versions before.

as a side note, the k24 in the tlx will have a newly designed two-stage manifold plus a tune to run on premium gas, but even with those changes, it only netted 17 hp compared to the Accord's k24. and no that manifold won't fit on the Si, because the new k24 in the TLX is based on the new accord's k24, which is very different from the Si's
 
since the dyno charts posted show the flow restriction only becomes an issue above 7000rpm (which is above redline), if you really wanna stick to NA power, your best bet is probably to spin the motor faster. i.e., balance the motor to make it safely rev higher and then work on increasing the flow with a better manifold and a better cam profile. maybe then you'll start to see the kinda numbers you're hoping for.
 
I was referring to the old k24 in the tsx, same motor as ours. If they have any aftermarket intakes available they should work for our car. The problem with the rbc isnt that it sacrifices midrange for top end. Its that it is designed for the 8th gen Si k20 which makes all its power between 6k and 8k rpms. So its tuned for that rpm range. Our motor makes all of its power between 4k and 7k. So if we take the same principles of the rbc but just tune it for our motor we should be able to get all the gains of the rbc and not lose any midrange. This is only theory but it should apply. I wouldnt think a multi stage intake would be required, just more parts for our specific motor.
 
Bulkybear said:
I was referring to the old k24 in the tsx, same motor as ours. If they have any aftermarket intakes available they should work for our car. The problem with the rbc isnt that it sacrifices midrange for top end. Its that it is designed for the 8th gen Si k20 which makes all its power between 6k and 8k rpms. So its tuned for that rpm range. Our motor makes all of its power between 4k and 7k. So if we take the same principles of the rbc but just tune it for our motor we should be able to get all the gains of the rbc and not lose any midrange. This is only theory but it should apply. I wouldnt think a multi stage intake would be required, just more parts for our specific motor.
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which principles are you referring to? 4000 rpm has much different optimal flow requirements than 7000 rpm. you're taking about a 75% increase in volumetric flow from 4k to 7k rpm, while 6k to 8k rpm is only a 33% difference. if you could apply just one "theory" and make the perfect manifold then what you're saying would work, but you can't. the "principles" that make the rbc great for the k20 at 6k-8k rpm aren't all encompassing, so you can't just take an intake that's "tuned" for high RPM and extend those same "principles" to make a good all-around manifold. if that were the case, multi-stage intake manifolds wouldn't work as well as they do because all you would need are short low restriction runners. nobody wants to design a manifold that sacrifices anything, but as a consequence of the different requirements you have to compromise somewhere and either optimize the design be good at one range or the other.
 
for what it's worth, browsing the TSX forums shows that a bunch of them showed lost low- to mid-range torque with RBC swaps as well...
 
hey_mikey said:
which principles are you referring to? 4000 rpm has much different optimal flow requirements than 7000 rpm. you're taking about a 75% increase in volumetric flow from 4k to 7k rpm, while 6k to 8k rpm is only a 33% difference. if you could apply just one "theory" and make the perfect manifold then what you're saying would work, but you can't. the "principles" that make the rbc great for the k20 at 6k-8k rpm aren't all encompassing, so you can't just take an intake that's "tuned" for high RPM and extend those same "principles" to make a good all-around manifold. if that were the case, multi-stage intake manifolds wouldn't work as well as they do because all you would need are short low restriction runners. nobody wants to design a manifold that sacrifices anything, but as a consequence of the different requirements you have to compromise somewhere and either optimize the design be good at one range or the other.
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You know more about that than I do that's for sure. But what im trying to say, being non technical, is that the rbc is designed for a different motor that operates at a different complete rev range as our motors and thats why its only gaining peak hp on our cars. Im pretty sure an intake for our car could be designed that would sacrifice low end torque for high end hp and would work well. This is what the rbc does for the 8th gen. Problem is the high rpm power on the 8th is at a rev range our motor cant even reach. And the low end torque it sacrifices is in our high end hp range. What the rbc does show us is that gains can be achieved with an intake that breathes better. Im wondering if an intake thats tuned the same as our stock one but breathes better would give us a better high rpm power band? I want to clarify im not arguing with you. I just dont understand this the way you do on a technical level.
 
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