[Nyborg Garage]

I would certainly try it.

Sent fra min E5603 via Tapatalk

 

[malkolm666]

Tried the Skunk2 Ultra street intake. Made less power and torque upp to 8000rpm. Made 305hp (versus 303hp). Peak torque went down 5nm. Proberbly its still my header/exhaust that is holding it back. So far my ported RRC is doing its magic. The skunk2 I should only use on a bgger motor or in a chassi that needs the TB to be on the other side, like in a S2000 or a Miata MX-5.

Above 8000rpm it wanted 3-4degrees more VTC and 1degree higher ignition.

 

[an2ny888]

was the skunk2 street manifold ported?

 

[malkolm666]

The Skunk2 ULTRA street was not ported.

 

[LotusElise]

Tried the Skunk2 Ultra street intake. Made less power and torque upp to 8000rpm. Made 305hp (versus 303hp). Peak torque went down 5nm. Proberbly its still my header/exhaust that is holding it back...Above 8000rpm it wanted 3-4degrees more VTC and 1degree higher ignition.

Very good investigation, proving in tendency what deibral also found out, but deibral compared both ported, the RRC and the S2US IM. The information about the 8 krpm characteristic tells much about the RRC, which simply begin to loose impulse height because of plenum size and bell mouth design, while the VE support of the S2US IM keeps up the level.

Concerning the header sizing:

...4, My header starts with primaries of dia 45mm for 12", then it steps up to 48mm for 12.5", the secondaries is dia 51mm and proberbly like 6" long now. Collector is starting at 2,5" and smooth and nice expands to 3".

...I think that the current header suits K20 better then K24. You are talking about outer diameters, right? If so, primaries are to small in my opinion, and so are the secondaries. 48mm to 50mm primaries, 54mm secondaries and 60-63mm Merge is what I would use, but the rest of the exhaust should be at least 70mm or more. If you can't make the secondaries bigger, make them longer.

drmo, I am not sure about that, otherwise the Formula One V10 (300 ccm/cylinder) headers had to be very huge. To make my point more clear the following:

• header designing is much about impulse and pressure wave timing, both is strongly related to diameter and length of the header, but also to it's obstacles, where reflection points where created. E.g. every step is reflection point, stepping a header right has pretty much to do with: step height, distance from valve and where it is located in the header system
• header performance has in addition much to do with header fabrication quality and technology. Inappropriate mergers destroy much of the reflection power and increases the flow resistance coefficient of it. The point here is all of the reflection and flow efficiency is not manily related to how much curves there are (lever arm is pretty low, we speak about Mach 0.6-0.9 peak!) it is much about obstacles: steps, welds, conjunctions, swirl, timing of flows to merge. These are the lever arms to work first.

A 500 ccm cylinder works pretty efficient for almost sense making header design in a certain engine speed range, but here we don't see that special area, we should see in the midrange region, where the small size header creates great impulse. Why not? Length doesn't fit that range by supporting the scavenging efficiency there or the reflection efficiency is down for other reason. From my point of view, here we have a combination of both: 1st and 2nd point. The length design is pretty much related to the end of the engine speed range, the diameters support more the impulse build up on the midrange, but also we see now resonance, which is likely related to the fabrication technology and design. Both in combination lead to a reduced VE level, which is still very good but not at optimum for an K-series. But you are right, the bigger diameter would fit better the short runners for primaries and secondaries...if they were adapted to the diameters (= longer) the midrange would be at least about 6-10 Nm higher. So, there is no general rule for diameter sizing of runners, its more a question of harmonizing parameters with the specification paper requirements. That said, what is the aimed torque curve, malkolm666?

 

[an2ny888]

So a bigger primary tube isn't always better than a smaller one?
i noticed that aftermarket k swap header makers size their products differently.
Skunk2 alpha kswap header has 45mm primaries, while plm has 48mm
Toda headers also have 45mm primaries , for both k20 and k24 applications

 

[LotusElise]

So a bigger primary tube isn't always better than a smaller one?...

I would say so, e.g. while a primary runner ID of 43 mm would be great on a stock near rallye engine (peak power around 8.2 krpm) within a 4-2-1 header system a primary runner of an 4-1 for a fast circuit racing engine (peak power around 8.8 krpm) of ID 45 mm or stepped 44/47 mm could be of help. All depending on the length of the runners. Concluding that, it is hard to say the ID of an runner has to be of xx mm for that displacement, as application purpose, engine speed range, cams, head port flow, and a lot of thing flow into the equation to adjust a header for its engine to the optimum.

Just a sidenote of great importance. Designing the optimal header setup is also and always related to what pipes sizes and material is available within budget and time. Just imagine my exaggerated example, you could fab a header with spec'd 44 mm ID-primaries, but there is only a 52 mm OD pipe available and the application is high speed circuit racing (Formula 2 chassis). The more than double weighting runners would give you an higher and more side loaded barycenter and a bad thermal expansion in the bends. So it would be quite smart to choose e.g. an available in time ID 43 mm/OD 46 mm pipe and to adapt the cams or IM or the CAI to compensate there bit higher wall friction due to the higher velocity of gas (= impulse), which may reduce the high end VE beyond 8.5 krpm for an 500 ccm piston displacement.

 

[malkolm666]

Just for a sidenote, I tuned a B18c4/B18c1 on the same dyno, got 153hk. Stock engine, stock header, stock cat. Engine was running fine and couldn’t see any abnormal smoke or oilconsumption.

Mods: 2” exhaust, AEM CAi and Hondata s300.

 

[Baz]

To add some numbers to this topic

EM2
K24A3 stock engine
CAI intake
OEM EP3 4-1 header + cat


231,5 HP / 276 NM

 

[katman]

cool post Malk!
I wonder how a Skunk Pro series manifold would do for you over the RRC.

In my intake manifold shoot out testing back in 09, a skunk pro manifold did pretty good especially top end power over the RRC (at least on my stock block 2 liter). The Ultra street manifolds seem to not do as well on stock block/compression from what I've seen (you're results back that up) though interesting to see how the Ultra street didn't help much on your K24. You figure a k24 would want that.

Have you thought about playing with injectors? and I assume you're on stock 310cc injectors during this testing?

 

[malkolm666]

Hi katman, my comp is pretty high with over 13. Its 13,2-13,4:1.
I think there is something holding the power back, my first thought is the ebay-PLM-header, second though is if the TB is to small. Its proberbly that restriction somewhere that dont make the Skunk Ultra street any benefit.

My injectors is modified oem ones, ~500cc and Im running E85.

Was it back in 09? Really? Haha times just flies! Feels like 3-4years ago!:blur:

 

[zof484]

If you have 72mm tb its big enough.
I tested 65->70mm on k24 and k25 and gains werent that big.

We just tested pracworks carbon manifold on k20. Stock 62,5mm was better than 70mm hybrid racing tb. 70mm lost top end. Midrange was same.
Probably some velocity stuff.

I also tested ported rrc vs ported ultra street on k24 and k25 and
results were similar.
S2 gave more top end vs rrc but lost everywhere else.

You need better header.

 

[bysleeper]

Nice thread. I also have a CL9 so very helpful!

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[LotusElise]

...In my intake manifold shoot out testing back in 09...

It was one of the first articles I read in 2013 about IM and their effects on engine performance, I was fascinated about your results :up:

...my comp is pretty high with over 13. Its 13,2-13,4:1...Im running E85.

What does ignition timing tell you about how it like it with that fuel, malkolm666?

 

[malkolm666]

Yesterday I got my new header to test sent from Zof484 its a big tube 4-1 with megaphone. Its gonna be exited to test on my dyno.

 

[drmo]

Yesterday I got my new header to test sent from Zof484 its a big tube 4-1 with megaphone. Its gonna be exited to test on my dyno.

Excited to see the results

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[mdhira1]

what red line?

 

[Rb85]

Great post

 

[malkolm666]

Redline 8500-8600rpm.

Thanks!

 

[GoThanh]

Any results with the new header?