Bandit 1200 header

[ivkat]

Hi, i don't know if i have introduced myself yet, but i have just started re-visiting this new kat-riders site after the whole kp situation. anyway i have been restoring my '90 kat 750 for the last 6 months or so, paint, rims, carbs, sprockets, etc, and i need an exhaust. i kind of wanted to do a custom exhaust (unique/availability) , and i heard that i could use a Bandit 1200 header. The header's flanges are compatible but the collector hits the oil pan drain bolt, (could be modified), anyway does anybody forsee any problems with this change (carb/flow issues). thanks for the input in advance, this site has already been paramount to my restoration.

[HIEXWIFE]

now how could you have introduced yourself and you only have 1 post? just kidding. anyway, welcome to KatRiders. i'm sorry i don't have the info you're looking for, but i'm sure someone on here will know. there are plenty of knowledgeable people on here, so don't worry. again, welcome.

[The CyberPoet]

I see a huge loss in low-end torque (which the Kat engine doesn't have a lot of to begin with since it's cam'd for top end grunt) because of the loss of back-pressure from the change in size.

Easy way to calculate it -- measure the inside of the stock header at the exhaust port, then measure the replacement. A little math will lead you to the difference in cross-sectional area, which is the critical value.

Example (values not absolute, just plucked out of the air):
Stock 98+ Kat 600 header: 23mm diameter
Stock 98+ Kat 750 header: 26mm diameter.

Area = Pi (radius^2)
Radius = 1/2 diameter
Thus
Area = Pi ((.5 (diameter))^2)

For the 600, the formula would go like this:
Area (square mm) = 3.14 * (1/2 * 23)^2
Area = 3.14 * (11.5)^2
Area = 3.14 * 123.25
Area = 415 square millimeters

For the 750 exhaust by comparison:
Area (square mm) = 3.14 * (1/2 * 26)^2
Area = 3.14 * (13)^2
Area = 3.14 * 169
Area = 530.6 square millimeters

One more formula to compare the two cross-sections (and therefore the flow rates):
((new/old)-1) * 100 = percent change
((530/415) -1) * 100 = % change
((1.277)-1) * 100 = % change
.277 * 100 = % change
27.7% change

(For those of you who want to jump my case about subtracting one and multiplying by 100 as incorrect math -- I simplified the whole percentage thing down [KISS] for those poor at math).

Thus, the 750 header flows 27.7% more than the 600 header. That's a substancial difference, enough to warrant serious jetting changes under most circumstances. A jump to an 1100 exhaust may induce an even bigger change, one that will take a lot of experimentation to come up with the right jetting for...

On the other hand, simply grinding out the welding seam lip on the same 600 header will net you a couple more mm of clearance on the exhaust, giving you about a 15 - 20% flow change for the cost of a couple dremel grinding accessories (provided you already have the dremel or equivilent).

ONE BIG NOTE:
Back pressure at low RPM's causes the engine to produce substancially more torque; this same back pressure at higher RPM's works against the engine's ability to flow large quantities of exhaust. Thus, it's a trade-off, and depends on where you want to make the power. For a more detailed discussion of back-pressure and how it affects torque/hp/power, see this thread: http://www.katriders.com/forums/viewtopic.php?t=2400

Cheers
=-= The CyberPoet

[duff daddy]

its 2:30 am and i just got out of 9 hours of mig welding and cyber you just KILLED my brain offically

good job on the math though

[The CyberPoet]

its 2:30 am and i just got out of 9 hours of mig welding and cyber you just KILLED my brain offically

Go veg out, man... it's what I'd be doing after 9 hours of welding (that and snorting/blowing out water to get rid of the crap in my sinuses from welding).

Cheers
=-= The CyberPoet

[ivkat]

okay, yeah so it will definately reduce low end torque and require jetting if i indeed find any top end power. thanks for confirming this, i had heard this was the case, but also had heard that engines really in fact did not need a little backpressure in the exhaust to create torque, thus creating my confusion. so my next question is what are my options in terms of custom exhaust or even finding an ssr2 exhaust for the 750? thank you.

[The CyberPoet]

okay, yeah so it will definately reduce low end torque and require jetting if i indeed find any top end power. thanks for confirming this, i had heard this was the case, but also had heard that engines really in fact did not need a little backpressure in the exhaust to create torque, thus creating my confusion. so my next question is what are my options in terms of custom exhaust or even finding an ssr2 exhaust for the 750? thank you.

Customizing: Grind out those weld seam lips, send it out to be jetcoated.

Replacement: Find a good aftermarket exhaust (or a rusty one and send it out to be jetcoated).

Cheers
=-= The CyberPoet

[HIEXWIFE]

Area = Pi (radius^2)
Radius = 1/2 diameter
Thus
Area = Pi ((.5 (diameter))^2)

For the 600, the formula would go like this:
Area (square mm) = 3.14 * (1/2 * 23)^2
Area = 3.14 * (11.5)^2
Area = 3.14 * 123.25
Area = 415 square millimeters

For the 750 exhaust by comparison:
Area (square mm) = 3.14 * (1/2 * 26)^2
Area = 3.14 * (13)^2
Area = 3.14 * 169
Area = 530.6 square millimeters

One more formula to compare the two cross-sections (and therefore the flow rates):
((new/old)-1) * 100 = percent change
((530/415) -1) * 100 = % change
((1.277)-1) * 100 = % change
.277 * 100 = % change
27.7% change


Cheers
=-= The CyberPoet

hey Einstein.......E=MC2 beat that.

[The CyberPoet]

hey Einstein.......E=MC2 beat that.

Enjoyment=MotorCycle^2 :P

How's about I blow your mind... provided this concept even makes sense to you:
C turns out not to be a constant for E=MC^2, but a localized constant which varies with both the age of the universe and the location.

Cheers
=-= The CyberPoet

[illinoiskat]

So, how much wider are the 1200 header pipe diameters? And is it the orfices out of the enigne that would be restictive or the stock header the restriction. Hmm what about an EXUP valve? jk

[The CyberPoet]

So, how much wider are the 1200 header pipe diameters? And is it the orfices out of the enigne that would be restictive or the stock header the restriction. Hmm what about an EXUP valve? jk

I've never seen the measurement for the 1100/1200 headers, so I have no clue.

The header would be derestrictive if you put the 1100/1200 header on, I would think; as soon as the gas passed the exhaust port, the pressure would drop rapidly (as it hit the larger pipe), changing the back-pressure and increasing the speed of the outbound gases. There might be a second restriction area at the collector, but I don't know for sure... Trinc said something about finding this when he went to the 750 header on his 600.
I don't know how you'd control an EXUP valve, or where in the config you would stick it -- and calibrating would be a biatch -- but it would work. In the old-old days, before the EXUP valve, some manufacturers used springs on a flap inside the exhaust somewhere by the tail pipe connector -- you'd change spring tension to change the resistance on the flap and "retune" that way.

Cheers
=-= The CyberPoet

[md86]

hey Einstein.......E=MC2 beat that.

Enjoyment=MotorCycle^2 :P

How's about I blow your mind... provided this concept even makes sense to you:
C turns out not to be a constant for E=MC^2, but a localized constant which varies with both the age of the universe and the location.

Cheers
=-= The CyberPoet

What if C A T really spelled dog ? :-k

[md86]

Okay , wait a minute now . E=MC^2 . Okay , E = energy , M=mass , and C = (I believe) acceleration . Now , how does the age of the universe and location effect accelaration (provided "C" is IN FACT acceleration ) ? Standard rate of acceleration of a falling object is what , 32 ft per second squared , right ? So what would it matter if where this took place , if the object is still accelerating at the same rate ? I never took physics or anything , so this is all crap left over from high school many years ago , but I'm kinda curious now ...

[illinoiskat]

Umm no C= speed of light. E = m c^2 C = 3.0 X 10 ^ 8 m/s It is stating that if you lose mass it will be turned into to energy. This can be seen in our every day life in nuclear power plants. The fuel rods go into a reactor heavier than they come out. The difference in mass is proportional(sp?) to the amount of energy that was released.

[md86]

Okay then , the spped of light is 186,000 ft per second or something , right ? Seems to me that would be rather consistant no matter where you are in the univers ...