AutoRacing Technik CL9 Project Teaser *Updated With Sound Clip On Post 1*

[Chris_F]

A straight through single outlet 2.5" should flow better than a 60mm being split into two.

Some guys in the states are running 2.5" single systems and making over 230whp on the k24. The peak power of a single outlet 3" system is usually 5-10hp more than a 2.5" system. The only reason you'd run a 2.5" system on a k24 is if you're a bit worried about noise levels (trust me, even a 2.5" exhaust is pretty loud), or can't have the car tuned to take advantage of the extra flow. Generally speaking the k20/k24's do better with a 3" system (but it also helps if you have a header with a large collector that can take advantage of the 3" diamtere)

Euroaccord13, what was your previous setup? I'm suprised a skunk2 dual exhaust would outflow a single outlet exhaust? Isn't the function of a dual outlet exhaust to reduce noise (exhaust gasses pass through two end mufflers)

In relation to cams, with a k24a3/k24a2 you can use cams, valve springs and retainers that are designed for a k20a2 you just need to use some k20a2 spring seats.

[Suntzu]

You will probably experience the same issue as my previous single set up (currently on Skunk2 Twin system), that is not enough flow, same as why JTune has came up with such a nice twin outlet system, there simply isn't enough to flow the exhaust gases with my camshaft and RBC set up on top of all the other mods.

So basically your saying ( and chrisf is saying) that a 2.5 inch system is not big enough!??

I was actually thinking a 60mm or 2.38 inch single system would be good for my mods with RBC etc.

I might get a quote on 2.5 inch into dual in mild steel with 2 x twin loops. Might get expensive though.

Im sure i will get some gains from exhaust. Im definately making more power than the 06 tsx and they have a 57mm into a 47mm twin system ...up a fair bit from the stock 52mm system on our cars but only making a few more kw, so Honda justified the bigger exhaust some how....

[Chris_F]

the bigger exhaust on the 06 tsx is used because it has the more aggressive cams (the most aggressive OEM k-series cams you can buy). The 06 tsx also has a bigger throttle body (64mm i think).

2.5" into 2 x twin loops will flow less than a 2.5" single outlet with 2.5" straight through muffler. When it comes to having a custom exhaust made with Y joins you also have to be careful. The quality of the Y join is going to be really important to how the exhaust flows so the exhaust shop will need to know what they're doing.

Don't get me wrong though Suntzu, all I'm saying is that 3" is generally considered ideal for the k-series if you want to make as much power as possible (also assuming you have the supporting mods like a race header with a large diametre collector). Most of the guys in the states are running 3" setups on dedicated drag cars so they have different requirements and dont need to make as many compromises (such as comfort/sound levels). So of course a 2.5" system is big enough it's just not ideal when every last hp is critical. A single outlet 2.5" exhaust will still outflow the stock exhaust by a hell of a lot.

For reference, I made 125kw atw with my old j's racing exhaust and that came with 60mm piping and a ~50mm internal diametre rear muffler (on the same day a stockish DC5R made about 115kw atw).

With stock cams, stock VTC and stock throttle body you really won't realise the full potential of a 3" system anyway. You may still gain 5+ peak hp but you'll probably end up sacrificing 5 decibles at the same time.

I'd really like to hear more about euroaccord13's old exhaust setup. I'm suprised that a skunk2 dual outlet exhaust would outflow a single outlet exhaust??

[power_of_dreams]

I can't see any torque figures in the OP, am I missing something?

[Suntzu]

the bigger exhaust on the 06

2.5" into 2 x twin loops will flow less than a 2.5" single outlet with 2.5" straight through muffler.

Hmm. i dont want a single with a cannon though. That because it will be loud, and very ricey. Both things I have to avoid at all costs.

Do you reckon a 2.5 inch with quality mid muffler and resonator onto single Twinloop ( quality, quite brand?? suggestions) will flow a lot better than stock and not be too loud.

Thats my plan at the moemtn anyway 2.5 inch, resonator, muffler, twinloop mufller in mild steel.

Any ballparks on a cost for this you reckon?

[Chris_F]

Hmm. i dont want a single with a cannon though. That because it will be loud, and very ricey. Both things I have to avoid at all costs.

Do you reckon a 2.5 inch with quality mid muffler and resonator onto single Twinloop ( quality, quite brand?? suggestions) will flow a lot better than stock and not be too loud.

Thats my plan at the moemtn anyway 2.5 inch, resonator, muffler, twinloop mufller in mild steel.

Any ballparks on a cost for this you reckon?

A setup like that shouldn't cost you anymore than $900.

Supercat and Magnaflow are both respected brands, well priced in Australia and have 5 year warranties. I'd go with one of those. A good exhaust shop will be able to reccomend you a muffler, just tell them you don't want a canon and want it as quiet as possible.

[EuroAccord13]

First set up was only an axle back, then we found restrictions in the mid pipe, then a custom one was fabricated to help flow the exhaust gases better, it was ok with the RBC and intake modifications and base tune, then the camshafts went in, there wasn't enough flow and hence the Toda headers was purchased (processed very efficiently from Adrian @ Toda Australia) and then the Skunk2 Cat Back was installed as well.

What Chris F has mentioned is true, 3 inch is too much for NA applications if its is not going to be modified hardcore.


What we've found with the single vs. dual outlet system is the same as what JTune has found, in short, the flow is much more optimum for the application I am using.

Mind you, there is nothing wrong with the single outlet setup, but it does have a limit to it if you are going to push maximum gains.

My original plan was to push for HP but with all the power and no traction, it's useless hence my goal has been changed to having the car going for torque instead (Read my Dynograph) which would be good for track days. The one I went to a few weeks ago proved that the torque I have in the car helped as I was able to pull and match the end speed of RX8s, WRX STIs and Liberty GT, and even outrunning some of them them around the track, only losing out on corners due to the extremely wet track.

[Suntzu]

I might just get a local company to fab up a copy of the skunk2 dual setup with twin loops. That might be better then in terms of noise/power. I think its a 60mm to dual 50mm no mid muffler hen cannons..i think..

Id get the proper skunk2 but the exchange rate and shipping make it unviable.

Thanls for the advise.

[Chris_F]

EuroAccord13, sounds like your current mods and tuning have made a big difference to the real-world acceleration of the car

What we've found with the single vs. dual outlet system is the same as what JTune has found, in short, the flow is much more optimum for the application I am using.

Mind you, there is nothing wrong with the single outlet setup, but it does have a limit to it if you are going to push maximum gains.

I'm still not sure why a dual outlet system would flow more than a well designed single outlet exhaust? Maybe the single outlet exhaust you initially tested had poor flow for a differnet reason (type of muffler used, workmanship etc.)

All of the high power k-series in Australia and in the US all use single outlet exhausts. The JDMYARD k24 is using a 3" single outlet exhaust and is making 178kw atw. I've also seen other cars in the states running single outlet 2.5" systems making 230whp or more. I still doubt a single outlet exhaust would be more restrictive. By adding a Y join all your doing is splitting the exhaust gasses, forcing them to travel through two mufflers and ultimately reducing the velocity of the exhaust gases/flow.

If I remember correctly, Jtune designed a dual outlet exhaust for cosmetic and noise reductions reasons. Since the product was "inteded for a mature market". I'm sure their design flows really well but I have a feeling it'd flow better if it was a single outlet 3" all the way through.

[integral90]

I'm still not sure why a dual outlet system would flow more than a well designed single outlet exhaust? Maybe the single outlet exhaust you initially tested had poor flow for a differnet reason (type of muffler used, workmanship etc.)

Just taking a stab here, but could it be to aid initial back pressure and then an easier release towards the end?

[Chris_F]

^ doubtful, if that was the case why would all the high power K-series in Australia and the states be using straight through 3" exhausts with a single outlet?

I'm talking about cars making anywhere from 200whp with simple bolt ons and tuning all the way up to cars with 340whp (All NA). They all run single outlet exhausts. There are no k-swapped cars making more power with a dual outlet exhaust. Surely if there was an advantage the workshops and private tuners in the states and Australia would have started using such a setup. Call me a skeptic but I'm just not convinced that a psuedo dual outlet exhuast can provide any benifit on a 4 cylinder car compared to a well designed single outlet. Why would companies like FEELS, J's Racing, Spoon, Amuse all offer a single outlet exhaust as their "high power" model. None of the dual exhausts on the market that I've seen tested have shown more than a 2-3whp gain.

I'll be having my car tuned with a standalone ecu soon, so it'll be interesting to see what sort of gains I can achieve with the single outlet setup.

[EUR003act]

^ doubtful, if that was the case why would all the high power K-series in Australia and the states be using straight through 3" exhausts with a single outlet?

I'm talking about cars making anywhere from 200whp with simple bolt ons and tuning all the way up to cars with 340whp (All NA). They all run single outlet exhausts. There are no k-swapped cars making more power with a dual outlet exhaust. Surely if there was an advantage the workshops and private tuners in the states and Australia would have started using such a setup. Call me a skeptic but I'm just not convinced that a psuedo dual outlet exhuast can provide any benifit on a 4 cylinder car compared to a well designed single outlet. Why would companies like FEELS, J's Racing, Spoon, Amuse all offer a single outlet exhaust as their "high power" model. None of the dual exhausts on the market that I've seen tested have shown more than a 2-3whp gain.

I'll be having my car tuned with a standalone ecu soon, so it'll be interesting to see what sort of gains I can achieve with the single outlet setup.

what about if you ran custom headers that went 4 -> 2 and then kept twin piping down to two seperate canons

lol

IMO twin exhaust is only for sound level and looks...