Ok. I know the exhaust thing have been beaten to death. Which one is best? Everyone have their own opinion about the pipes they like and the reason for it. I am not going to say which one is best. I have tried a slightly different opinion. I did some searching of my own and went to all the web sites I could find to look at the HP and torque outputs listed by the exhaust manufacturers.

1st I looked at the HP figures. Ok, not all dynos will give the same readings, but what I have found is that they all punch out about max 44 to 48 HP. The RPM where these exhaust deliver the max HP are slightly different, ranging from a max at 6400 to 7200 RPM. This is not actually what I wanted to talk about. For all intensive purposes they are all about the same, small differences. So if you look for HP then they all will give you good HP.

2nd I looked at Torque outputs. This was more difficult to do as most of the guys do not publish the torque outputs of their pipes. I was able to find torque outputs from MBRP, Yoshi, DMC and GYT-R. Please if you have any other makes, share them. What I have found is that the torque outputs are very much different!

They all list the stock motor's torque output, but they are all showing different values. So much for trying to compare the values, BUT they all seems to agree about the shape of the stock torque curve. So t0 make all equal I looked at the shape of the curve at different RMP.

Let’s start at 3000 to 4000 RPM.
Stock pipe. Starts of then output drops at 3500 and picks up again at 4000 RPM to give the same level of torque as at 3000 RPM
Yoshi pipe does the same. Start at 3000 and then drops round about 3500 rpm and then picks up more at 4000 RPM. The figures at 4000 RPM is more than at 3000.
MBRP and GYT-R starts of at 3000 and keep rising rapidly to 4000 RPM. NO drop at 3500 Nice smooth increase all the way.
DMC. This pipe starts at 3000 and jumps massive to 4000 RPM. Again no drop in torque at 3500. Reaches MAX torque out put at 4000 RPM.

Now at 4000 to 5000 RMP.

Stock pipe rises slowly form 4000 to 5000 RPM. Nothing serious, but an increase.
Yoshi pipe very similar curve as the stock pipe. Increase all the way, but nothing major. MAX torque at 5000 RPM
MBRP and GYT-R. Torque curve stay about flat. Slight gains, no losses in torque. MBRP MAX torque at about 4500 RPM., GYT-R about 5000 RPM
DMC pipe. Serious negative torque curve. Loosing torque as RPM increases.

5000 to 6000 RPM output.
All pipes have a more or less flat torque curve between these RPM ranges. The only one actually showing a slight improvement in torque is the stock standard pipe, but it is much lower than the rest.

6000 to 7000 RPM range.

All pipes showing very negative results. Ending up at 7000 RPM at more or less the same torque value as what they started out at 3000 RPM.

So, my conclusion. All increase torque over stock, but the pipes with the best and flattest curves are the GYT-R and MBRP pipes. These two pipes also give you the biggest and best spread of torque across the RPM range. Yoshi does well and also have a nice flat curve, but starts with a dip in torque and making torque later than the rest. The DMC makes masses of torque at 4000 RPM, but then looses it very quickly and stay stable at 5000 to 6000 RPM. This gives you a very spiky torque curve and is not flat at all. The DMC also do not have a smooth HP curve. I believe the trinity pipe will give very similar results as the DMC as they seem to look the same.

Ok I am not going to slam DMC or any other pipe, but to me if you need low down torque go DMC, smooth torque all the way go with BMRP and GYT-R and higher RPM torque go Yoshi.

I would love to see the rest of the torque curves form guys like Sparks, WB, trinity and the rest.

 

I completely agree, and good review with the info hunting. I rarely care much about hp curves when I talk to a company, I ask, can I see the tourqe curves, cause tourqe is what gets power to the ground, not hp. But a lot of these companies just don't do the tourqe curve...shame[img]i/expressions/face-icon-small-sad.gif[/img]

 

Some of the differences could be due to jetting, it's not easy getting them dialed in at the lower RPM range.

 

Torque is what gets you there.
I would like to see the torque curve of the GYTR head pipe which is smaller than stock.

 

I KNEW IT.........my friend tried to tell me that nobody makes an exhaust with smaller head pipes........
but I thought that it would be excelent for MX cause it would be high torque........
it looks like to me that the gytr, alba, and fmf all have smaller headpipes.........
am I correct?

 

I got all the dyno results from the manufacturer’s web site.

Here are the links

Yoshi "http://www.yoshimura-rd.com/dyno.asp" Click on " 01-02 Raptor Slip On System” to download the PDF file. Their Dyno reads very high. Even their stock raptor makes very high figures
DMC "http://www.dmc-on-line.com/RAPTOR660.html" Their Dyno reads way low, not sure why.
GYT-R "http://www.yamaha-motor.com/accessories/assets/500/gyt5lp9301aldyno-500.jpg" They don't have values, but its easy to figure out what the values are if you know what the stock raptor puts out and using it as a base.
MBRP For the life of me I cannot find it again, but it might have been on 14min web site or Bob Craycraft's web site.

 

From what i could find Alba, White Bro's, CT, Trinity, FMF, Bills, Pro Circuit and MBRP Regular uses the same size as stock. Gryadon, Big Gun, Sparks, Yoshi and MBRP full race use larger than stock headers. I don't think GYT-R header will be smaller than stock. The difference between stock and GYT-R headers are the length of the dual pipes coming out of the head. They GYT-R dual pipes are longer than stock and join much later into the larger single pipe. You can change the torque of the motor by changing the length of the header pipes. The longer they are the more torque you will get a lower PRM. You can also change the diameter of the pipe to get the same result.

 

HP is a derivative torque...torque is what it's all about.