custom exhaust w/o camshaft duration

Question

custom exhaust w/o camshaft duration

mekial2222 (Automotive)

(OP)

13 Aug 08 16:07

I know I've seen afew questions on here in regards to making a custom exhaust, but what if you can't find the camshaft duration? I have a 1982 kz1000p that I would like to make a 4-2-1 system for... I thought this type of engine would be popular enough that someone would know something about it or could give me a jump start with some info they found about it. here is all the relavent information I can find for it;

Displacement 998 cc
Bore x Stroke 69.4 x 66.0 mm
Compression Ratio 9.2:1
Power 88HP@9000rpm 112Ft-lbs@8000rpm

and I ran one of those cfm calculators you can find online and got this for the intake;
CARB CFM vs RPM
140.98 @ 8,000 RPM
158.60 @ 9,000 RPM

I found a calculator online in regards to exhaust cfm and got these numbers;
(1200/540)*140.98 intake cfm= 313.28 exhaust cfm
the 1200 and the 540 were values they gave to get a multiplier for the intake cfm...

is there any help out there for this? or am I just shooting in the dark? Any info will be appreciated. thank you.

evelrod (Automotive) · Answer 1 · 2008-08-13 21:33:25

Really don't have my paperwork on my '77 KZ 650 Custom but, from memory I used 1 1/4" x 13" primary into 1 3/8" x 13" secondary into a single 1 1/2" exhaust to a Supertrap. It was a little noisy, but not totally unbearable for a 37 year old rider...Too much for me now from a four banger. The bottom end and mid range saw dramatic improvement...by the seat of the pants dyno. I know that is not what you were asking, but it should give you a start. I used the same basic setup on our 1600 Lotus twincam, just larger pipes diameters, full sized muffler (Dynomax Turbo) and, much longer tail pipe. It works well in this application, too.

There are several proprietary outfits making exhaust systems such as this. Have you checked them out?

Rod

BrianPetersen (Mechanical) · Answer 2 · 2008-08-19 23:04:55

If it is critical for the purpose of analysis, you can always measure the camshaft duration, at least with good enough approximation for this purpose. Take the valve cover off, put a dial indicator on the valve or rocker arm or whatever else you can get access to. Take the crankshaft end cover off. Rotate crankshaft until the valve opens by 1mm, mark where that happens, rotate crankshaft until the valve is 1mm away from closing, mark where that happens, measure.

evelrod, your primaries sound too short by quite a bit, but the diameters sound about right. If anything, the primaries should be a little smaller inside diameter than that.

evelrod (Automotive) · Answer 3 · 2008-08-20 14:33:05

Brian, there was this little ground clearance problem with the bike. The rev range on the 650 was 10 to 13,000 rpm and the 1600 TC was 6500 to 8500. We did all the cut and try work on the car on a dyno but the bike, done several years earlier, was just 'make it fit' approximation...It worked very well, though. Much better than the OEM pipes.

Oh, by the way, I got the "13" dimension from Cosworth!

Rod

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custom exhaust w/o camshaft duration