Power gain with a new exhaust

[tkm433]

So I iwas really bored and decided to do some research into aftermarket exhaust. So I only got as far as the M4 line wich as far as I can see is one of two aftermarket systems that I can find for the Hawk.(That is new and I can actually order) The other one being D&D which is all over ebay but it appears that they are no longer being made since their web site does not list them.

I found this info on the M4 site where they show a Dyno chart for their pipe and the stock setup on an NT650.
http://www.m4exhaust.com/products/flash/M4_Exhaust.html

NT650
Box Stock H/P=59.3 TQ=38.1
M4 Full System H/P=60.8 TQ=39.9

That is an increase of H/P=1.5 or 2.5% gain
Increase of TQ= 1.8 or 4.7% gain


Now I do not know if they just bolted their system onto the Hawk and did not touch the carbs or if they did do any carb adjustment???? That i do not know and that could be good or bad depending on what they did for the test. It would be good since if they just bolted on their pipes and stayed with the stock Hawk carb settings their might be room for more gains in power and it shows that their pipes produce more power than stcok but it is bad if they did adjust the stock setup to produce as much power as possible on the dyno becasuse the number do not reflect the reason to spend $500 plus on an exhaust system.

The torque curve looks good for the Hawk between 3500 and 6000rpm with the M4 exhaust and that is where most of us use the bike but the overall numbers in my view do not justify the cost. Yes, I do not have to buy them.

As I said I was really bored????????????

[MasterBates]

hmm. see what hord says, id get a new exhaust anyways, the stock is too quiet for me, plus its not that great to look at.

[nomoduc]

If you go to Hord's website, i thought our bikes were 40 something hp stock and like 52 with filters and jets????? Hmmm

[Tusk]

Like Lynn said... checkout http://hordpower.com/ and study the "Dyno Charts" linky.

That should curb your boredom for a while.

[Hordpower]

Their dyno chart is f'd up. That chart is from Robert Pandya's Hawk, which had a mildly built engine. I think it compares a TBR pipe to the M4 or something like that. I wish they didn't even have that chart posted because it is worthless.

On a stock engine with stock airbox expect ~3-4hp peak gain by going to the M4 and a 1.0 jet kit. Midrange gains are substantial. Add Uni filters and a 3.0 kit and the gains are more like 5-6hp over stock.

[juicedstang999]

Their dyno chart is f'd up. That chart is from Robert Pandya's Hawk, which had a mildly built engine. I think it compares a TBR pipe to the M4 or something like that. I wish they didn't even have that chart posted because it is worthless.

On a stock engine with stock airbox expect ~3-4hp peak gain by going to the M4 and a 1.0 jet kit. Midrange gains are substantial. Add Uni filters and a 3.0 kit and the gains are more like 5-6hp over stock.

So how much will you gain with the M4 shorty under engine, "ala Buell" uni's and a 3.0 kit? I did my own back to back comparison test on the street W/ the M4 full and a M4 shorty system and it def. pulled harder even at lower RPM's W/ the shorty system. I was just curious if you have had the chance to test an under exhaust on the Dyno and if it is even worth the effort and loss of my hearing? I know by nature, most twins love a short, free flowing exhaust.

[Hordpower]

I haven't been able to do any scientific, same bike, back-to-back tests of std. length vs. under engine exhaust yet. But I agree with what you say, I have been able to infer that the shorter exhaust makes more midrange power. Maybe when I get RichG's bike done, I can do some quickie tests of short vs. long.

My own Hawk made tons more midrange with a short tailpipe and short/large diameter muffler vs. a std. M4 tailpipe and muffler, but I don't consider it a relevant test because that particular engine setup is off-the-chart different from most.

[Rich G]

I haven't been able to do any scientific, same bike, back-to-back tests of std. length vs. under engine exhaust yet. But I agree with what you say, I have been able to infer that the shorter exhaust makes more midrange power. Maybe when I get RichG's bike done, I can do some quickie tests of short vs. long.

My own Hawk made tons more midrange with a short tailpipe and short/large diameter muffler vs. a std. M4 tailpipe and muffler, but I don't consider it a relevant test because that particular engine setup is off-the-chart different from most.

J.D., feel free to dyno my engine combo with different exhaust systems! I'd love to know too...