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2002 DC5 Type S
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Discussion Starter · #641 ·
I think that is the key point. It is responsible for this massive torque peak at around 6000 rpm you see on most RRC dynos. Past 7000-7200 power hardly climbs anymore.
My CNC ported RRC had the same characteristic. I did not like it for this reason in my Elise.
seems like they are they same IM for the most part except the runners are larger on the RRC. It may work better on my PRB-1 head with DIC. I want to open up the RRC and port it like the RBC I did.
 

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Arouse the DAMPFHAMMER!
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The runners are the same length b/t the two.
You call this equal length? Let me see were is it...
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These are equal runner lengths 😇.

But serious, 10 mm equals to about 160 rpm. In addition to that the different VE over the runners and angle varies also the pressure wave reflection efficiency and bulge expansion at the reflection moment. I would not wunder if we talk about an Runner discrepancy of the RRC IM of around 300 rpm between #1 and #3.
 

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Arouse the DAMPFHAMMER!
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Id like to see a production replica of Joe Macs 8.5 manifold.
Do we have such ;)? Finally the IM technology bases on laws of nature, so similar efficient IM should look the same, shouldn't it?

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The DAMPFHAMMER IM my look similar and may use similar looking technology, but from an design standpoint it is a different approach. Joe fought against the 2-number world of the US: ftlb and hp, therefore his designs had much bigger runners. In Europe we had most of the time smaller runners on any NA race engine compared to the stuff which is sold in the US K-series aftermarket, as in Europe midrange power is still a good nice to have. BTW, according the SuperFlow's formula Joe used to calculate the runner length for different orders of the harmonic row the runner length would be 304 mm long. Anyway, design-wise these are equal length in hardware.
 

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Arouse the DAMPFHAMMER!
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would not go as far as calling names or making this anymore confusing, except buy your own and make your own measurements. This is extremely zoomed in. I can do them in a more detailed manner...
You mean you compare the 8" marking in green of both IM (flange surface till green line)?

Indeed the differences are outside the center lengths, which are - now proven - equal from a outside runner perspective. The torque curve differences came from other differences and I am not sure how much of those just came from tuning itself. Really fair comparison you can do only if you tune both perfectly. We have a tons of threads and dyno result to that and we all saw both, the RBC or the RRC in a bit better position. But in counts, the RRC won more often. The reasons for this are at last not only we have here more K24 tests then K20 tests.

The bit bigger runners of the RRC need a better scavenging, engines with a less efficient scavenging demand system immanently smaller runners. As the head ports already flow more then most engine setups need the velocity build up is essential.

As a side note, works teams like SMS or Zakspeed of Opel (also known as Vauxhall), who used the 86x86 Opel engine with the code C20XE for the STW racing series, which had about 300-310 hp (2-Liter-NA) while the intake ports just flowed 280 or less [email protected]" and the ITB diameters were only 46 mm! Of course BMW, Renault, Peugeot, Audi, Mercedes, Volvo, Rover, Ford and Honda were on that party, which was the best time for NA racing. It was the series nearest race series which made it to millions of spectators. In England it was the BTCC, in the US the NATCC, here in Germany it was the STW or DTM, where the I4 bangers in the 2.0 liter area ruled the racing Sunday of millions (except NATCC, maybe in the US the I4 sound is not attractive). If you have the time and the patient (German comment only) see the most important race of the STW in 1998


The competence for racing in that field was massively high. I love that smooth high speeding at the edge of the suspension capability. As power wasn't that high to other racing series, failures of driving were catastrophic, see the Aiello (Peugeot) in the early race.

In the US aftermarket you rarely get K-series ITB's of that size, but here in Europe in the 90'ies 300 hp at flywheel at or below 8500 rpm out of a 2 Liter engine were standard. That was or was almost 30 years ago. The K-series stock intake manifolds have already 46-48 mm diameter on a 200 hp level.
 

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Arouse the DAMPFHAMMER!
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