1100 exhaust modification

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crowesnest3

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I'll start with maybe I shouldn't chop up a good set of stock pipes but that aside looking to "undress" my 1100 more to the "cafe" world, have a set of head pipes I was thinking of running 2 into 2 and fit with some "standard" baffeles, but was looking at whats there now and was seeing might look "right" if I cut the stock pipes at their widest part right around the axle nut! @ a 4" dump!, but that might be really a little loud? Any thoughts on how one might baffel that or maybe just don't and be loud? Gotta say I'm still a little perplexed by the ongoing theory/understanding that modifying the pipes does little in the performance category, its mostly just look and rumble. If you're looking to tweak the performance of your car engine you go to the air and fuel intake and then open up the exhaust so that the engine gets both a good inhale but and equally good exhale. So whats up with the "doesnt make much difference" to the "wing" ..... oops sorry two questions not one, anyway look forward to the thoughts and opinons ...... Crowe ..... :Egyptian:
 
2 into 2 as in 4 pipes? or 2 into 1 as in stock configuration? No baffles will be pretty loud. JC Whitney has some baffles that are of a few different sizes. If the goal is look then the field is pretty open if you want performance then I'd go with early cams and carbs and minimal baffles for a little back pressure. Once the carbs are tuned then back pressure can be added until decel backfire is minimal. That should give you some very nice performance while retaining stock like dependability. Assuming the ignition is up to par.
 
yes as if 4 individual pipes is one approach the other being the two into one stock system but cutting them at their widest point around the axel nut ... a 4 " dump, basically the same size as the Jardines except shorter. How to baffel that large size? if at all? Been reading with great interest Joedrum's variious head and cam configurations and they are certainly interesting and even tempting, but I'm not quite ready for that step. Anybody explore ram air systems ala "vmax" or velocity tubes tied into the airbox? Yes a less restrictive aircleaner for sure, synced carbs and Dan's CBR coil conversion for hotter spark before moving into the big leagues by switching out heads n cams. The snow has gone out finally so had a chance to run my "new" 84 interstate which needs some tlc especially a carb sync but definitely a smooth and comfy ride then ran my first baby 80/1100 around the "rural block" @ 8 miles, boy my 1100 is a lot more aggressive than the 1200, my imagination? Maybe cuz the stator is dead on the 1100 not as much drag .... haha .... back to the pipes ....Crowe ... :Egyptian:
 
forgot something, recently watched Joedrum's flic on the 1200 with 1100 heads etc, now that bike has a real good bark and then noticed he was running out of the head pipes, no mufflers ..... hmmmmm ..... so what is loud? Less back pressure here make things better? ..... Crowe..... :Egyptian:
 
The only problem with too little back pressure you loose some of that beautiful torque!
 
Nothing gained by cutting out the end baffles besides a lot louder and maybe even less power.

Just like a car, a lot comes into play with reduced back pressure.
Have to make it breath better on the intake side as well as mod the timing and valve/intake flows.

I don't completely understand it all but one mod can increase high end while another can increase low end torque.
I think the entire assembly as stock is well designed with the exception of the spark, easy gains possible there.
 
Cutting them as you describe will I think allow the stock baffles to come out. If they do you will effectively convert the mufflers to megaphones and it will be very loud. If the air filter and box are not altered you may just lose power and gain sound.
 
hmmm im not going to say much but I disagree with oldwings if theres a problem in exhast its almost always from restriction ....its obvious to me that oldwings like flow and very little back pressure to none ...all motors are different ...with total overlap in oldwing cams to only 10 degrees that is about all the back pressure needed ...motors with more overlap have greater need for backpressure ....a strait pipe will produce back pressure the longer it is the more back pressure period ....you can tune just about any exhast set up empty of baffles and plumbing with length of the final pipe exit ....this whole theory that back pressure is required for performance is bull ....if true dragters would have them period ...that's how it is to me
 
I've never understood the whole concept behind back pressure.
Most vehicles I removed it lost power.
They sounded like they had more power but that was as far as it went.
I don't know, try it and see.
 
the best way tis theory works is in vucume ...the longer the pipe less vacume ...I actually tuned up my avcume advance with the length of the hose to steady it its pull ...worked great ....this is all opposite from exhast but same thing really ....the longer the pipe the more back pressure it put on the exhast system ....
 
Exhaust systems is something I know a little about. First of all there is no real accurate formula that I know of for exhaust pipe diameter. What we do know it that too big of pipe will cause a loss in power, and why is that. One the exhaust valve opens we have a very hot exhaust gas that is an accumulation of few unburned hydrocarbons (fuel), carbon monoxide, carbon dioxide, nitrogen oxides, sulfur dioxide, phosphorus, and the occasional molecule of a heavy metal, such as lead or molybdenum. These are obviously in a gaseous form and will be under a lot of pressure trying to get out that exhaust valve and into the manifold. Us old hot rod guys once thought the bigger the tube the better, not so. Exhaust gas is very hot and we want to keep it that way. Why you ask, cold air is heavier than hot air and a pipe that is too large will allow cold air in and increase the backpressure and that increases the amount of energy needed by the piston to push the exhaust gas out. We do know for engines producing 250 to 250 hp generally pipe diameter should be three inches and the big hp goes to about four inches other than truck engines will run five and six inches because of the big displacement. So you say why even have a exhaust manifold on the hot rods, well that cold air hitting the exhaust valve would be very damaging to the valve eventually and here again we have cold air trying to keep the hot gas in the combustion chamber.
So what about our 1100, 1200, 1500 wings? We need to keep the exhaust gases hot all the way to the end of the pipe, if not we are going to loose power. There is a lot more to exhaust systems, and the gurus in the engineering departments probably have some exotic math formula to figure just how much back pressure they want or don’t want. The other side of it is manufactures are cheap, they will take the path of least expense in most cases, that is why you can improve performance with headers, and high quality mufflers.
 
Oh, this is good stuff, I'm even the kind of guy who'd like that formula! But to stay simple (?) if i"m understanding what has been said to this point the ideal would be to keep the exhaust gases hot for flow, thus my thought of doing 4 into four sounds the right direction yet be careful not to restrict that too much for fear of creating too much back pressure .... making the engine work to hard to get rid of the hot gases. My thought of cutting the stock system on the 80/1100 comes from thinking .... gotta be careful of that thinking shit ..... "the" non stock headers on the market are the Jardines which 2 into one with the final pipe size being around 4", yes there is a baffel in there. Stock pipes 2 into one around 4" but then back down to @ 1.5" with a baffel. Thats where I come up with the stock system cut back to the 4" pipe with probably some kind of baffel, remember somewhere out there reading of merely inserting a large washer, another was building up a baffel using a container stuffed with steel wool ..... did something like this waaay back as kid racing go karts.......and to be honest and forthcoming I am thinking that assuming it doesn't adversely affect the performance, that 4" dumps terminating around the axel nut would look "bad ass" on a "cafe" style GW and I'm not spending $ on a custom system ................... and yes looking to do something with the airbox and agree with Dan a little more ignition punch (CBR coils?) would be good. Hey, I've gotta pull the engine out to replce the bum stator before anything else, last year I ran it around locally like a "hybrid" wired in a yard tractor battery and kept my travels under 140miles. This year have a "new" old 84/1200 that I can just ride, but no chance I'm not gonna start messing with that too, if only to deal with TLC issues...... crowe ..
 
Speaking from experience so far running the cbr coils, any way you can make the spark hotter/fatter will improve running.
I really think this is a worthwhile mod no matter how it's done, cbr or neon coils and others.

Mine will start right up no choke.
It needs choke to keep running but before the cbr coils it would not start unless I gave it FULL choke, back off the choke it would die.
 
you are thimking good crowsnest you just described my mongrel exhaust system that exactly what I did ...and yes did modify the airbox ... and yes did improve spark with dyna coils picups and wires ...this 79 outran all early oldwings and 1100s it came across even tho 78-79 cams are the mildest of all oldwings including 1200 cams ......later on I put a stock 1100 exhaust on it and it dam near wouldn't run ...it lossed all kinds of power ....the ignition system on hooch is the moded mongrel ignition and its performing well with the strait jerdines pipes ...front part only no 4inch cans ...so im totally convince where I stand on this issue its always some tweaking to do but to say one way only is just plain wrong ..
 
Dan what damages exhaust valves is being subjected to cold air. Lets face it those valves get very hot and if they are cooled too rapidly it can cause cracks of the valve face and seats. I'm no expert on exhaust systems but I think I understand the basics pretty well. I was once told the trick is to get the exhaust gases out as quickly as possible without subjecting the exhaust system to cold air. However excessive back pressure will cause a loss of power due to the energy required to push the gases out. So it becomes a balancing act.
 
joedrum":1gku9h5f said:
....this whole theory that back pressure is required for performance is bull ....if true dragters would have them period ...that's how it is to me
Click to expand...

OldWrench":1gku9h5f said:
...well that cold air hitting the exhaust valve would be very damaging to the valve eventually...
Click to expand...

And THAT'S why drag cars run zoomies...they ain't worried about valve damage, since the valves don't survive that long anyway. Full throttle engines don't like any backpressure...backpressure means more piston power is used up pushing the exhaust gasses out the pipe...which is counterproductive to quick ETs.
Pipe length has a lot to do with where the torque curve maxes out, too. For Oldwings, I can't see the need to modify the exhaust in search of more power, unless you plan on racing.
I'd like mine to be a little louder, but it ain't worth the effort in relation to the return on performance or fuel mileage, for me. :wave:
 

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