montechester
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If I am reading this right, it appears the K24 has a large advantage in HP and Torque until you get into the very top of the rev range. With this kind of advantage down low, and the apparent conservative tune you noted, I'd think the potential for tuning could be HUGE on the new car. I'm sure we'll see what can be done with these soon enough. Thanks for the apples to apples comparison.
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owequitit
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montechester wrote:
If I am reading this right, it appears the K24 has a large advantage in HP and Torque until you get into the very top of the rev range. With this kind of advantage down low, and the apparent conservative tune you noted, I'd think the potential for tuning could be HUGE on the new car. I'm sure we'll see what can be done with these soon enough. Thanks for the apples to apples comparison.
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Not as huge as you think, unless, like Shawn mentioned, you want to risk frying your $500 catalytic converter. Those things aren't cheap. (Coincidentally, I just looked at it, and it doesn't even flow straight through, so perhaps a well designed downpipe would make a bit more power than suspected).
Also, don't forget a couple of points. First, if you start modding the K24, then modding the K20 is also fair game, and a just retune of the K20 will pick up a significant amount of power from 4500-6000 (for a rough visualization, draw a straight line from the K20 power curve at 4500RPM to intersect the HP curve at 6,000 and that will give you an approximation of what the K20 would gain by lowering VTEC). I am not sure of stock base timing on the K20, but I do believe it also gains a little bit in the top and bottom end from a retune. What actually surprises me most is the relatively small torque advantage of the K24 below 3,000 compared to the K20. Yeah, it is larger, but it isn't the same swell of torque that is available from 3,000-5,000. I am curious to know if that is a result of a single exhaust profile(which has to be optimized for a much narrower range of parameters), or other factors in play. Since that pretty much matches the TSX dyno that was posted awhile back, I knew it would look like this, but I would intuitively expect the K24 advantage to be linearly decreasing over the K20 as the revs build. The other aspect of this is that it seems it would dull the response of the car a bit right in the range where people said the torque would pay off most. Yes, it is has a rather large advantage, but it is surprising to see it not really hit maximum until about 3K, which is already relatively high versus daily driving RPM's. The other thing I found relatively surprising was the K20's stock torque rating of about 150 lb-ft. That is pretty significant considering its FLYWHEEL rating of 139 lb-ft. The same could be said of the K24 as well, which is also measuring slightly higher than rated. Even though Shawn's dyno seems to be a little bit higher than many others (could just be due to adjustment or conditions, NOT saying he is fluffing them), it is consistent to see the K20Z3 produce very close to its rated flywheel value at the wheels. I haven't seen enough dynos of these new K24's to say that yet; although the ones I have seen paint a similar picture.
Second, much as we said before, the K24 does have more usable part throttle, lower RPM thrust. Never denied that. However, in a spirited driving situation where that abundance of thrust would have an advantage, the K20 need only be in VTEC to match or exceed the performance of the K24. Above 28MPH, it is 100% possible to keep the K20 there at all times.
Third, keep in mind that the '11 Si's tested were stronger than this one by about 10HP up top. What I would like to see for illustrative purposes is a 100% bone stock K20Z3 dyno with absolutely NOTHING changed except VTEC crossover. I say this because it is surprising to see how much usable power is gained through the midrange with that 1 single change. And, it is a change Honda SHOULD have made from the factory.
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notyper
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Well, not quite. The K20 is actually better in the upper part of the rev range. If I can find the one stock 2011 we did I'll post that too, as it was 8-12 hp better on the top end. Jeff confirmed similar differences when he dyno'd a 2011 press car on a different dyno.
If you want to compare, just shift the K24 curve to the right by 1000 rpm to get an idea of how the cars will compare when accelerating all out.
Leaning out the top end should net a few hp which would bring the K24 up to parity with the K20 on the top end if that doesn't create a cat issue. We're not sure why the power varied so much down low. Is the knock sensor really set up to be sensitive? Is it the nature of the tune for the close coupled catalyst? We don't know. Suffice it to say, IMO, this engine is not ever going to be better up top than a K20 with similar mods (intake to intake, exhaust to exhaust, etc.). But I think it will be possible to increase the K24's advantages over the K20 below 5000 rpm or so with tuning. How much is up in the air.
In terms of how that will make the car perform, in all out driving or on the racetrack, very little differences between the two. In daily driving or having fun in the canyons, the extra midrange of the K24 will make it quicker.
SC
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A77
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I have a copy of dyno results from an Automobile mag test on an 07 Si - and the shape of both torque and hp curves is identical to all intents and purposes. but in both cases the y axis totals are lower - ie a max hp of 180 and torque of 134.
That 2.4 has the wobbliest curves ever - no?
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notyper
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Yep, different dyno. I use a Dynapack which removes the wheels and attaches directly to the hubs. Much smaller losses and much better repeatability/accuracy. But it will read 6-7% higher than a roller depending upon wheel size/weight/alignment.
Typically we see 182-185 whp on a roller dyno for the K20Z3 Si.
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RocketRon
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And the K24 will produce about 180 WHP on a roller dyno, right?
Considering this formula: HP = Torque x RPM
The K20 is superior even if the K24 has more torque as it should considering the larger displacement.
That being said, it's not all about HP...it's about how they are produced. The high revving K20 gives us a taste of the enthousiastic engines that you find in the LFA, GT3 RS, 458...for MUCH less.
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owequitit
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RocketRon wrote:
And the K24 will produce about 180 WHP on a roller dyno, right?
Considering this formula: HP = Torque x RPM
The K20 is superior even if the K24 has more torque as it should considering the larger displacement.
That being said, it's not all about HP...it's about how they are produced. The high revving K20 gives us a taste of the enthousiastic engines that you find in the LFA, GT3 RS, 458...for MUCH less.
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HP=torque x RPM, but you have to put 5252 in there to be accurate.
Really, it is the F1 vs NASCAR debate. Both are fast and fun, but which is preferrable?
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RocketRon
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Owe, I'm not sure on which one is preferrable.
But I know which one is more exotic and exclusive...
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owequitit
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RocketRon wrote:
Owe, I'm not sure on which one is preferrable.
But I know which one is more exotic and exclusive...
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I totally agree. Which is my biggest complaint. I certainly didn't buy my '09 Si because it was the fastest car around. It is not nearly as sad as it is made to seem, but I bought it because it offered something I couldn't get short of an M3 otherwise...
And realistically, it has MORE than enough power to get around town and the highway on a daily basis, and it certainly has more than enough power to bomb a canyon backroad.
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