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Discussion Starter #1
Alright guys, I've done some searching around and have yet to see an all motor setup that really makes me want to follow it. Specifically speaking, because of a lack of holding power out to redline. Which I really don't understand because K-heads are supposed to be the best flowing honda heads yet.

I've looked at many setups and dynographs and they all seem to have the same story after about 6krpm torque starts dropping off rapidly. This is quite disappointing as, coming from the b-series realm, where your average lsvtec setup on ctr cams will pull trq out to ~7800rpm.

Its my understanding that camshafts have the biggest affect on this, and even the dyno's of a certain high dollar manufacturer share the same story with all other k cam's, the torque just doesn't hold; which in my opinion is totally unacceptable. Holding torque is essential to making big all motor power.

I know this post isn't really a question, more of a rant. So anybody else feel free to throw your opinion in here. :up::down:?
 

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It is an interesting concern.

Stroke has the biggest affect since it is the primary reason for the powerband curve to shift left or right.

So when combined with the right gearing and tires it works out in the end.

In my opinion you are looking for the wrong signs on the dynographs. It is all relative.

Take the extreme example of the 400whp IPS motor



Look where tq is peaking and where power flats out. There are many factors that contribute to this. Stroke first, but you need the right cams, exhaust header and intake along with tuning, ignition etc...
 

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LOL, where are you trying to make power? 15,000 RPM?
Why does a cam need to continue making torque past 7k if the bottom end can't spin that high? It is cheaper to change gearing for most applications, and for those that can't they can only make as much power as the circumstances allow.
 

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I do not want to be quoted out of context though. It all maters and other factors play an important role. What I mean by primarelly stroke.. is in the even that you have a setup with xyz components peaking tq at XXX rpm, stroke would be be easiest way to move the powerband but without the right header and intake.. it will not happen..

Check this out...

99mm K24a with ported head 88m pistons





99mm k24a with 89mm pistons and stock head, stock RBC and 2 liter header



See how the tq dies early?
 

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Discussion Starter #5
Honda motors have always had the reputation of being high revving, peaky motors, I guess I just assumed the new generation motors would retain that charectaristic since it seems to be a great design as proven by previous generation motors. I dont think what I'm asking is unreasonable.

Nikos, that is a very valid point. I will think on this more.

EDIT: wow that 1st graph looks good, only 220trq and over 300whp. Thats nice.
 

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one more 99mm k24a 88mm stock head




another one 99mm k24a 88mm stock head with some tricks



here's a stock frank k24a crv/k20a2 head

 

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Alright guys, I've done some searching around and have yet to see an all motor setup that really makes me want to follow it. Specifically speaking, because of a lack of holding power out to redline. Which I really don't understand because K-heads are supposed to be the best flowing honda heads yet.

I've looked at many setups and dynographs and they all seem to have the same story after about 6krpm torque starts dropping off rapidly. This is quite disappointing as, coming from the b-series realm, where your average lsvtec setup on ctr cams will pull trq out to ~7800rpm.

Its my understanding that camshafts have the biggest affect on this, and even the dyno's of a certain high dollar manufacturer share the same story with all other k cam's, the torque just doesn't hold; which in my opinion is totally unacceptable. Holding torque is essential to making big all motor power.

I know this post isn't really a question, more of a rant. So anybody else feel free to throw your opinion in here. :up::down:?
You are misreading the situation. B-series appear to "pull trq out to ~7800rpm" because they have no midrange. The improvement on the k-series has always been recognized as the midrange power. That is what VTC does for you. So it's not that the top end power is falling so much as the midrange power was dramatically increased.

There really is no such thing as a motor with an infinite torque band. All motors are going to reach peak volumetric efficiency within a certain rpm RANGE. Typically peak torque happens in that area.

Anyhow, if you've tuned b-series motors, you know that depending on how you set your cam gears, you can accentuate the midrange or the top end, but not both. Most people opt to accentuate the top end, which results in a flat looking torque band. But really, it's only optimized at the top end. With k-series, VTC allows you to optimize torque everywhere. That's why you've got the big bump in the midrange.

:up:
 

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Discussion Starter #14
You are misreading the situation. B-series appear to "pull trq out to ~7800rpm" because they have no midrange. The improvement on the k-series has always been recognized as the midrange power. That is what VTC does for you. So it's not that the top end power is falling so much as the midrange power was dramatically increased.
I really don't think it has as much to do with VTC as it does displacement. Disregard midrange power alltogether and your see what I'm talking about; Look at the losses in trq after 6k on a k-series vs a b-series dynograph. There is anywhere between 20 to 30wtrq lost over the next 2krpm on a k-series whereas its around 10-15wtrq on most b-series dyno's. I'm beginning to think this is a flow issue with the head rather than a camshaft issue as thought before.

There really is no such thing as a motor with an infinite torque band. All motors are going to reach peak volumetric efficiency within a certain rpm RANGE. Typically peak torque happens in that area.
I have no delusions in that area. I'm not asking for an infinite power band, I just like the idea of a motor that likes to rev is all. I'd be willing to sacrifice some midrange power to have more flat powerband up top.
 

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Does anyone have a full dyno pull with VTC locked at 0-10 degrees vs the full and final tune they can post? I'll try to get one together tonight if no-one does. That should help greatly illustrate the difference.

The stroke will determine the VE ceiling(Like chunky and Nikos were saying). However, if you look at some 86mm builds, torque has no issues keeping up given the correct cams.

I challenge you to find any N/A B-series making 210lbs of torque at 10,000 rpm and over 230 lbs at 9,000rpm :p :slapsyouinthefacewithaglove: :D
 

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Discussion Starter #16
It hard enough to find a b-series making over 200wtrq. That would be sweet to see what a dyno with the vtc locked looks like though.

And I'm with you, I still think with the correct set of cams torque could be pulled out farther.
 

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I really don't think it has as much to do with VTC as it does displacement. Disregard midrange power alltogether and your see what I'm talking about; Look at the losses in trq after 6k on a k-series vs a b-series dynograph. There is anywhere between 20 to 30wtrq lost over the next 2krpm on a k-series whereas its around 10-15wtrq on most b-series dyno's. I'm beginning to think this is a flow issue with the head rather than a camshaft issue as thought before.



I have no delusions in that area. I'm not asking for an infinite power band, I just like the idea of a motor that likes to rev is all. I'd be willing to sacrifice some midrange power to have more flat powerband up top.
You're still missing the point. The K-series "appears" to fall farther on the top end because it rises higher in the midrange. This is a DIRECT consequence of the VTC adjusting cam phase to maximize power production in all areas. Basically, your eyes are playing tricks on you.

With the B-series, you can only optimize for one area, usually top end. Most b-series motors are not optimized for their full potential in the midrange.

All you have to do is look at a "static" cam angle pull for a k-series motor with the VTC fixed at the cam angle for top end power, and compare it to a pull where the cam angle map was optimized throughout the powerband. You'll see that there is similar top end power, but the pull with a static VTC has a level torque curve that doesn't seem to fall much, However, the pull with the optimized VTC has the appearance of falling more because it made so much more midrange power.

Anyhow, what you're describing is an optical illusion.
 

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Discussion Starter #18
Wow, did you even read what I said?

I really don't think it has as much to do with VTC as it does displacement. Disregard midrange power alltogether and your see what I'm talking about; Look at the losses in trq after 6k on a k-series vs a b-series dynograph. There is anywhere between 20 to 30wtrq lost over the next 2krpm on a k-series whereas its around 10-15wtrq on most b-series dyno's. I'm beginning to think this is a flow issue with the head rather than a camshaft issue as thought before.
I know exactly what you are saying. I'm saying take that and throw it out the window. Look at the dyno's from 6k on and compare (not numbers, losses). The loss in torque is no optical illusion.
 

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Wow, did you even read what I said?



I know exactly what you are saying. I'm saying take that and throw it out the window. Look at the dyno's from 6k on and compare (not numbers, losses). The loss in torque is no optical illusion.
Yes, I read what you said. You're still not getting it. At 6k you're still benefitting from VTC. Only after about 7000-7500 does the VTC get pulled back to around 30deg, which is where most cams make their top end power. If you ran 30deg through the entire RPM range, you would have a very flat torque curve, but it wouldn't be the best that the engine is capable of. Talk to any k-series tuner and they will tell you the same. Without VTC, the torque flattens out into something that looks like a b-series car could have produced.
 
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