Quiet And Free Flowing Exhaust...

[rallyeash 155]

I'm looking at exhaust options for the K20 309 but I don't really want anything loud as the 205 is loud and I'm building the 309 as a more refined vehicle. Yes there will be induction hammer with Vtec and tb's but I don't want a boomy exhaust. Must be getting old!

I'd happily run a standard 309 GTI exhaust but will restrict the potential 225hp...

 

Any good suggestions? I could take it to a exhaust company and I did that with the 205 but it also wasn't cheap. Needs to be 2.25 / 2.5' ideally.

 

A quiet aftermarket item with a 2.5 exit would be ok, a larger bore oem would be my preferred.

Edited February 4, 2015 by rallyeash

[stef205 92 1 Cars]

Mine is or was around 89db but it is fairly complex system. Was made by my friend and had a big box made to sit where the spare wheel was. In total it is a 3 box sytem.

[Batfink 201]

You will need custom. Get at least a two box system. A 2.25" will probably suffice for the power and will be quieter than a 2.5" like for like... For good power you want to make sure the backboxes do not run a smaller internal tube compared to the bore of the exhaust. This forces gases into the wading but can reduce power a smidge. Run as straight as possible to get the best power. Theres plenty of space at the rear to fit a decent custom box so I dont think its going to be difficult.

[B1ack_Mi16 67]

I have some experience from when I built my 205. At first I bought a stainless resonator muffler type, well to be honest it was insanely loud, didn't seem to dampen the sound at all.

 

The orginal exhaust was of course very nice sound-wise but very restrictive.

 

Then threw together a 2.5" Simons universal system, not much care taken at all, but bought the absoloutely largest mufflers (straight through type) i could find.

And the car is dead silent from the exhaust side, I was actually surprised how silent it became, as it's still straight through.

 

Can't be said about the inlet induction hammer though, but as long as driving on small throttle openings it is actually silent apart from beeing stripped out and lots of road noise etc.

 

You can see them here.

 

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[Batfink 201]

Just one look at that resonator one and i'd have said it would be loud lol

[welshpug 1,666]

Merlin Motorsport do those Simons silencers.

[rallyeash 155]

Merlin Motorsport do those Simons silencers.

They do I though that could make my own system.

[kyepan 291]

Free flowing and silent - same as what i wanted, I used long life exhausts - i specced free flowing and silent, the original one they did was pretty quiet, not much drone. decent sized boxes. they took it apart to fix a minor issue and it wasn't the same afterwards, but originally it was great.

 

Thinking about the exhaust a bit more holistically.

 

If you go for short manifold primaries - 12 inches, you'll be looking at a peak at 6krpm, if you go for something nearer 22-23 inches you'll get a peak at 3500 and then seven, which will make for a bigger fatter punchier wad of torque mid way up the range, then another hit as the vtec kicks in.

 

Have a look at my engine build thread and you'll get an idea of the manifold, and there is a better pic of the exhaust on the deathstar project thread in the first couple of pages.

 

To give you an indication - fitting throttle bodies and the fancy long primary manifold gave me about 25 ftlbs of torque mid range from 2500 rpm-6000 rpm, it also got rid of the usual dip at 3500. Most MI-16's are peaky buggers, and this makes it more like a tuned 8v, nicer to drive in non bats*it crazy mode, and generally quicker. So what i'm saying is a bit of time and effort on the manifold will yield a much more mental fast thing!!

 

Granted when vtech kicks in you need free flowing but before that it's all about pulse tuning.

Sandy may know more about the relative effects of manifolds on the K20.. but it's an engine so it will be broadly similar.

[Sandy 191]

Alot of K20 tuners are OBSESSED with peak BHP and are using rolling roads to find it, the transmission loss correction of which tends to amplify the effects of high RPM changes, in an unrealistic way, so what';s avilable is generally perverted towards that end. As Justin says, it is an engine and the VTEC profile is all you should really be concerned about, because that's where all the power comes from. With the standard cams and bodies, it will pretty much be better on VTEC as soon as there's enough oil delivery to switch it; the cams are like a mild race profile, so the manifold design should be based on that. I designed a manifold for an fairly standard S2000 engine in a wild spaceframed Mk2 Escort a while back and the grunt it produced was remarkable for the spec, the guy that built the engine was unhappy though, because it was producing the power he'd projected, but at around 8400RPM instead of 9 ish as he expected, which he said wasn't right. No pleasing some people. (That's exactly what Jesus said Sir)

Edited February 26, 2015 by Sandy

[rallyeash 155]

To update this thread, I built my own in the end.

 

2.5' pipe and Simons silencers

 

 

 

 

 

 

How it'll fit

 

[rallyeash 155]

Sandy, do you think that's more because of the way Jap tuning is and the following it has.

 

For example you start reading up on the K20 and many people are claiming 250+ on a standard K20 with a 'skunk 2' inlet, standard tb, exhaust system and a Hondata. I've put it down to the way of the Japanese tuning world and cannot see how you can simply add 50hp when the 2.0 production engine is already 200hp.

I'm happy with 225hp with the bodies, anything more is a bonus.

Edited February 26, 2015 by rallyeash

[welshpug 1,666]

there are variants of the k20 running nearer 220 bhp as standard I believe!

[rallyeash 155]

Yes the K20A is just over 220HP.

 

The K20A2 found in the UK EP3 civic is 197hp and what I have. However still many people claiming large figures on a lightly fettled EP3 civic.

[Sandy 191]

People's idea of what a good power delivery is varies, just pulling lots of revs doesn't make a car fast, but it might sound fast and the poularity of you tube vids of screaming engines that sound gutless to me, tells you all you need to know about that. Rolling road softwares tend to exagerrate high RPM gains, because the Tx loss curve is always drawn as a aconstantly climbing curve with a perpetually increasing growth rate; which isn't actually representative of the true losses. The net effect is that high revving engines tend to show more power at high RPM on the rollers than they do on an engine dyno; it's pretty much a universal truth in my experience.

I can see a really well honed K20 package on standard cams being able to make around 240bhp, but to do that efficiently with decent mid range, it would have to be on well designed and developed ITBs with a really good exhaust manifold, rather than the crude stuff that's typical. Given the amount of people tuning that engine, it stands to reason that a few might be cracking that code; but if they are 5 gets you 10 that some are on the high side of the RR error and the rest are just claiming it to be competitive.

Edited February 28, 2015 by Sandy