full akrapovic or fcrs

Killerwhale · Post by **Killerwhale** » Mon Dec 11, 2006 7:57 am

cheesie wrote:as far as what I know or have read if your header pipes are to big you will loose a lot of low rpm punch as the engine needs some back presure, I am not sure what is the best system for two cylinder engines but on four the 4-2-1 is best for overall power and a 4-1 will see better results at the top end on a four cylinder engine the colector box has a big part to play, when one cylinder has expelled the gas the inertia helps helps draw a fresh mixture into the next cylinder giving closer to 100% volumeteric efeciancy how do the standard headers colect togerther I see on pictures that the akra flow nicely into eachother with no sharp bends or big steps in pipe diameter

IÃƒâ€šÃ‚Â´ve put on a "supercan" wich welds onto the pipes with 10mm holes, in low/mid revs when exhaust pressure arenÃƒâ€šÃ‚Â´t up to velocity the cans extra volume is used and with more exhaust pressure at higher revs exhaustgasses passes thru.
Never heard of it before but as i got it real cheap i tried it and it worked great! ....not to pretty though as there was no room on the inside of pipes!

jpe · Post by **jpe** » Mon Dec 11, 2006 8:19 am

cheesie wrote:how do the standard headers colect togerther

OEM headers don't connect at all. It's two separate pipes all the way...

bobtrx · Post by **bobtrx** » Mon Dec 11, 2006 9:20 am

Sorry jpe but standard headers have a cross over pipe between em

jpe · Post by **jpe** » Mon Dec 11, 2006 10:23 am

bobtrx wrote:Sorry jpe but standard headers have a cross over pipe between em

Of course they do

Even took pictures and sold mine and still don't know how they look...

burty · Post by **burty** » Mon Dec 11, 2006 10:27 am

How much bigger diameter are the Akropovic headers? If at all?

Post by **phuk72** » Mon Dec 11, 2006 10:30 am

Generally speaking, 1 exit pipe is for top end power and 2 is for torque.

Loads of science around exhausts involving flow of air, how the gasses cool, back pressure etc but I wouldn't worry about it too much.

Again a generalisation but standard headers do not flow the gases as best they could and the aftermarket stuff is better at this (and hence releases a bit more power). Have a look at the Micron site and read up on the serpent headers and see what they are trying to achieve.

TBH, if we are talking only power gains (on a stock motor) then it probably ain't worth going beyond standard headers and some decent end cans.

jpe · Post by **jpe** » Mon Dec 11, 2006 10:58 am

burty wrote:How much bigger diameter are the Akropovic headers? If at all?

Stated previously in thread (means I wrote earlier that I don't remember). Think it's 6 or 8 mm

burty · Post by **burty** » Mon Dec 11, 2006 1:14 pm

I measured the o/d of mine this morning and a rough measurement came out at 39mm. The headers on my Tuono are 45mm o/d. I agree that with the TRX the port size is perhaps a limiting factor ( do wonder if that's a legacy of an engine that was what...650cc in it's initial design) Anyway the fact that Akropovic's headers are bigger after the bend implies that there's something to gain there. Of course whether different headers are 'worth it' is always going to be a matter of debate.

trixynut · Post by **trixynut** » Mon Dec 11, 2006 2:40 pm

I have a Renegade full system 2 into 2 which seems to have what looks like standard bore downpipes from the cylinders to just past the bend under the engine (about the first 30-40cm) then they increase and stay at that diameter up to the cans.

Over the years, I've had my bike on the dyno four times, and the figures (from my fading memory!) were something like:

Standard 78bhp
add scorpion cans (end cans only) 81bhp
add FCR 41mm carbs 86bhp
swap scorpion cans for full renegade 2-2 system (downpipes and cans) 90bhp

As the scorpion cans were not that different to the cans on the Renegade full system, this implies the FCR carbs perform better with a full system with bigger bore headers, maybe!

Dave.

cheesie · Post by **cheesie** » Mon Dec 11, 2006 7:05 pm

thanks for the replys on this

Post by **phuk72** » Mon Dec 11, 2006 8:14 pm

this implies the FCR carbs perform better with a full system with bigger bore headers, maybe!

Simple physics really - more air and fuel in means more gases out and they have to flow properly. IIRC Renegade systems work (extremely well) by creating airflow that essentially sucks the fuel into the system by tapering the pipes.

Post by **Kevtrx849** » Tue Dec 12, 2006 1:37 am

Standard headers are 38mm, Over are 42mm. 5hp increase just there. Lost low range drive with the overs. Akra system has no dead spots across the range.

CYA, Kev.

burty · Post by **burty** » Tue Dec 12, 2006 9:27 am

So we've established that the standard pipes are probably undersized.

Killerwhale wrote:
IÃƒâ€šÃ‚Â´ve actually confronted some of the makers of pipes why they donÃƒâ€šÃ‚Â´t do downpipes for the TRX and the reply has been that the originals are so oversized so it wont do much difference.
....but thatÃƒâ€šÃ‚Â´s answers from 4 makers...and there are hundreds of Ãƒâ€šÃ‚Â´em!

That sounds like an excuse not to bother. Maybe it's a demand thing really.

Post by **phuk72** » Tue Dec 12, 2006 10:03 am

I'd guess that it is a supply and demand issue. Can't imagine anyone wanting to do the R&D as the costs would not be recouped.

cheesie · Post by **cheesie** » Tue Dec 12, 2006 7:20 pm

anyone had thier bike on the dyno with full akra and standard carbs sorry for the questions but I like discuss a subject to death to get the best picture