Under Engine-Exit Exhaust

[mogiman]

one of those shorties like the gp bikes or the ones that the gsxrs use ,off the lastest models that sit by the swing arm that would keep your cog lower take weight away from the rear and also keep heat away from your shock and you still have the ground clearence and would prob be a lot easier to tune!!!

[imdying]

There will be an optimim header length. The end of the header doesn't need to be the start of the muffler.

Not even that easy Look at the 999, asymmetrical exhaust system... I think the 999 powered Vyrus is something like 700mm long for the back header, and nearly 2m for the front one.

[Toast]

Cheers for the input, people.

I just read the Sports Production rules though, and it seems that 'The location, appearance and profile of the silencer must remain as original', so that puts that plan to rest.

It also says, unfortunately, that 'Wrapping of the exhaust system is not allowed', so it looks like I'll be doing the HPC coating thing come Nationals time.

[Gremlin]

I looked at the idea for my road bike when deciding on a new muffler... thought a full under engine custom system would be neat.

Problem was pipe length... either you do a full loop under the engine for length (and I had no room for that) or you run a box similar to the gixxers, underneath the engine (I say similar, coz you don't want the cat and shit). In the end, for me, the time and effort involved, coupled with the unpredictable outcome didn't make it worth it.

Got an expensive small side pipe, and had it tuned up... Never looked back

[HDTboy]

Cheers for the input, people.

I just read the Sports Production rules though, and it seems that 'The location, appearance and profile of the silencer must remain as original', so that puts that plan to rest.

It also says, unfortunately, that 'Wrapping of the exhaust system is not allowed', so it looks like I'll be doing the HPC coating thing come Nationals time.

I'm glad I completely read the thread, cause I was going to point that out.
If you're looking at a new exhaust system, why not go Ti? the Leo Vince on Chris's bike runs cold enough to touch most of the time
Titanium pipe and carbon muffler, runs cold as, and nice and light. Don't ask what it cost though

[cowpoos]

I'm glad I completely read the thread, cause I was going to point that out.
If you're looking at a new exhaust system, why not go Ti? the Leo Vince on Chris's bike runs cold enough to touch most of the time
Titanium pipe and carbon muffler, runs cold as, and nice and light. Don't ask what it cost though

what did it cost?

[Toast]

I
If you're looking at a new exhaust system, why not go Ti?
Don't ask what it cost though

And that's all that needs to be said

I spoke to the guy from HPC. He said that their regular coating will give a 20% reduction in radiant heat (much greater reduction of internal exhaust heat, apparently), and their 'Extreme' coating will give about a 60% reduction in radiant heat.

I'm thinking go for the Extreme stuff where it passes the shock, and the other coating for the rest of the exhaust.

Supposedly the cooler exhaust temps means greater rate of flow for exhaust gases, so that'll probably do something to the fuelling? Another learning experience coming up...

[vifferman]

Isn't the undertail exhaust to make the person behind's draughting less efficient?

Apparently, having the exhaust umm... exhausting into the slipstream reduces drag noticeably. Although I couldn't see how on a bike with a fairly unaerodynamic lump sitting on it a small thing like that really figured.

What'd HPC quote you for the coating, Mr Toast? I could do with the headers and cat coated (they're a bit crappy looking). And they're one of the few things I haven't modded yet....

[Toast]

The price list for the standard coating is:

Motorcycle / Jetski / Kart
Exhaust System
HiPerCoat ™ Exhaust Coating (up to 700°C)
Exhaust Pipe Price
Exhaust Pipe $19/ft
Single w/Muffler $123
2 into 1 w/Muffler $145
3 into 1 w/muffler $200
4 into 1 w/muffler $245
2 into 1 no muffler $78
3 into 1 no muffler $139
4 into 1 no muffler $178
Dirt Bike 2 into 1 no muffler $49
Muffler $73
Muffler less outer case $50
Two Stroke
Expansion Chamber $89
Exhaust colour options: HiPerCoat Polished, HiPerCoat Satin, Semi Gloss Black, Cast Iron Grey
Used, Rusted or zinc pacifated parts will need a chemical strip:
Single Pipe $17 Chrome stripping service available POA
2 into 1 $23 Chrome Strip is essential for parts to be HiPerCoat Polished
3 into 1 $34
4 into 1 $39
Dirt Bike 2 into 1 $17
Expansion chamber $28

The Extreme coating was a fair bit more expensive, about 2.5 times I think.

[Pancakes]

...................Supposedly the cooler exhaust temps means greater rate of flow for exhaust gases, so that'll probably do something to the fuelling? Another learning experience coming up...

Air has viscousity and weight like fluid so for gasses fluid dynamics still apply, think, cold air = cold honey and warm air = warm honey and now you'll see why the same volume of hotter air will be easier to force out of the exhaust constrictions than colder air.

(don't ask me to build an exaust that works but I can tune loudspeakers quite nicely)

Apparently, having the exhaust umm... exhausting into the slipstream reduces drag noticeably. Although I couldn't see how on a bike with a fairly unaerodynamic lump sitting on it a small thing like that really figured.

What'd HPC quote you for the coating, Mr Toast? I could do with the headers and cat coated (they're a bit crappy looking). And they're one of the few things I haven't modded yet....

Yeah I thought that too, how much of a difference can it make but I guess for SUperBikes its not HOW MUCH difference but ANY difference and the mod will get the nod.

[Maido]

I had an 04, 05 and now have an 07 CBR600, That I have raced at nats for the last however long, I never had trouble with the shock over heating.
Keep in mind it should only really get hot in there when the bike is idling before or after a race when there is no air moving past. I realise there will be a small low pressure area beneith the rear cowl but I don't really think it is enough to cause the shock to overheat.
As said earlier Ten Kate seem to be able to set record laps throughout the race which is usually a good indicator that is works ok.
As far a weight goes and keeping a low COG, the heaviest bit of that exhaust system is the headers (stainless) and they are quite low, the only bit of that system that is Ti is the muffler housing so it probably evens out the weight distribution.
We also ran the full HRC with arrow system on the 04 and 05.
Also you are bang on the money as far as keeping to the original configuration and looks as far as rules are concerned.

I was thinking about getting a custom under-engine exit exhaust to solve both of those problems. However, someone who used to tune bikes on dyno's told me that with such a short exhaust the bike would become very difficult to tune, and likely lose a lot of its mid-range power.

Realistically with the current NZ rules the only thing the Honda has engine wise above the other brands is a fat mid range, they don't share a peaky high HP that the other 600's have, so losing that would definately put you at a disadvantage.

As far as exhaust systems go, we dynoed that system against 2 other 600SP Hondas that were running the larger diameter Arata exhaust, which also feature nice tapered headers (one was Haydens BWH bike) and they were all within about 1HP and 1Nm torque and all had the same shaped curve.(meaning I should be able to ride as fast as Hayden, now why is it that I can't!!)

The thing we picked the most performance in with the 04 was the cam timing, I would suggest you look at that if you already haven't. (The 05 was pretty close to where we wanted it from std)

If you need to know anything racing wise about them just give us a PM, cos there isn't many being raced in NZ, it is hard to get info on them.