What type of exhaust for power. (2019)

This will be fun to try. I could just temporarily block the crossover.
Come on Spring!

Glen

Get one of Mike's 2EX1 Maney style pipes he makes.

He says it adds ~5bhp in the middle.

I think with any exhaust system, there are always kadency effects. The crossover might provide a dead area containing mixture waiting to be stuffed back into the combustion chamber at certain revs.

gortnipper said:

Get one of Mike's 2EX1 Maney style pipes he makes.

He says it adds ~5bhp in the middle.

Click to expand...

If you had been reading! You will have noted that that is Storm42s starting point! Different manufacturer, same dimensions.

The modelled NRP straight pipes are mine on a 750, they are 1.5" ID and the modelling says...oh no it doesn't!

But only a dyno run of the different systems will tell.

I should note that I currently have a different profile cam fitted and the engine does not match the exhaust as well. Message is change exhaust to suit cam. But it would be best to do dyno runs before changing anything else.

For personal preference I might like to leave teh exhaust how it is and go back to the cam profile I was using!

storm42 said:

Hi Steve, how are the ribs, and the bike? hope all is well, are you considering Gedinne this year?

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Ribs are improving, not much pain left, and breathing improved. But my general strength is down at the moment, gardening and moving fire wood are a challenge!

I need to start an exercise regime! Not my favourite activity.

I am beginning to get into the workshop doing stuff for all race 3 bikes and hopefully I have bought all the parts I need to sort the Norton at leasst for the first event I have planned for it!

I haven't ridden any bike since September, but my guess is many on here are the same. I plan to ride my road bike next month to see how that goes. Then I am looking at going to the CRMC race meeting in June at Pembrey, to test my Suzuki and parade the Norton. After that I will have a better idea what I might be able to do. And how my wife copes with it!

If it goes well and my doc is ready to sign me as fit I shall probably get my French licence sorted and run at Carole in July.

Gedinne would be nice, but not ready to commit, I have choices on a licence for that.

acotrel said:

I think with any exhaust system, there are always kadency effects. The crossover might provide a dead area containing mixture waiting to be stuffed back into the combustion chamber at certain revs.

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Even if that did work with an original head, it probably doesn't work with D ports! (Fullauto).

SteveA said:

If you had been reading! You will have noted that that is Storm42s starting point! Different manufacturer, same dimensions.

Click to expand...

DOH! Mind like a sieve sometimes..

For the record - Moto55UK said he got better performance with a long 11-3/8" intake tract from the head (not the valve) to the end of the velocity stack. This is for a 920 with 37mm carbs and assuming that bigger proportions work better.

I tried 1-1/2" pipes on my 750 cafe racer and got zero improvement. For an all out racer things are different. Ron Woods used 1-3/4" pipes on his 84HP short stroke. Harley also used 1-3/4" pipes on their 90 - 100 HP XL 750s with huge ML cams and D ports. The HD ML cam is even bigger than the Sifton 480.

Perhaps a dyno run is incapable of demonstrating differences in torque which are within the repeatability of the equipment ? It might be better to have two exhaust systems, one with the crossover and one without and then ride the bike over a very twisty road circuit which you know very well, using the different systems. Then assess the points at which the bike is better and where it is worse, taking into consideration the revs. and gearing. The gearbox is a torque converter. With exhaust systems, I have always found it to be suck it and see. I have Paul Dunstall's race tuning book. In the book I have, he did not use 2 into 1 exhausts. When I made my first, I expected it to work with a tail pipe diameter the same as a header pipe. I immediately lost 2000 RPM off the top of the usable rev range, then I started cutting the collector back and welding on bigger tail pipes. I got it to the stage where I had only lost 1000 RPM - but at that stage, my lap times reduced significantly because I was then able to ride the bike without it biting me.
I notice from photos that most of the modern 2 into 1 exhausts use the same diameter tail pipes as the two header pipes. I don't think you get the best, that way. But with a big thumping motor, who can tell the difference, even with a dyno - unless you actually ride the bike ?

If you use a Paul Dunstall type exhaust system with separate pipes with megaphones, you will certainly get best power. But I would not do it with my bike because I rely on being extremely fast in corners and don't worry too much about the guys who get past me at the ends of the straights. You will always get those if you ride a Norton. You just go under them at the next corner. My Seeley 850 with the 2 into 1 and the heavy crank and close box, is an extremely easy ride. A lot of the guys in the class in which I ride, use 1100cc methanol-fuelled CB750 Hondas. Al of them are out on the ripple strips when coming out of corners - but going down the straights, they are extremely fast. One of these days, I am going to fit new tyres to my bike. The ones I used the last time I raced were 10 years old. Steering geometry is the key to going fast on a Norton.

SteveA said:

Ribs are improving, not much pain left, and breathing improved. But my general strength is down at the moment, gardening and moving fire wood are a challenge!

I need to start an exercise regime! Not my favourite activity.

I am beginning to get into the workshop doing stuff for all race 3 bikes and hopefully I have bought all the parts I need to sort the Norton at leasst for the first event I have planned for it!

I haven't ridden any bike since September, but my guess is many on here are the same. I plan to ride my road bike next month to see how that goes. Then I am looking at going to the CRMC race meeting in June at Pembrey, to test my Suzuki and parade the Norton. After that I will have a better idea what I might be able to do. And how my wife copes with it!

If it goes well and my doc is ready to sign me as fit I shall probably get my French licence sorted and run at Carole in July.

Gedinne would be nice, but not ready to commit, I have choices on a licence for that.

Click to expand...

Glad you are recovering and the will to ride is still with you, hopefully see you at Gedinne and if I can find time for a holiday, hopefully I could rent your cottage and my wife could do some exploring in your area.

acotrel said:

If you use a Paul Dunstall type exhaust system with separate pipes with megaphones, you will certainly get best power. But I would not do it with my bike because I rely on being extremely fast in corners and don't worry too much about the guys who get past me at the ends of the straights. You will always get those if you ride a Norton. You just go under them at the next corner. My Seeley 850 with the 2 into 1 and the heavy crank and close box, is an extremely easy ride. A lot of the guys in the class in which I ride, use 1100cc methanol-fuelled CB750 Hondas. Al of them are out on the ripple strips when coming out of corners - but going down the straights, they are extremely fast. One of these days, I am going to fit new tyres to my bike. The ones I used the last time I raced were 10 years old. Steering geometry is the key to going fast on a Norton.

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Al, I cannot find your post, but I remember you have concerns about going into your TTi box, I have posted a thread about the TTi and as you will see, they come apart like a cassette box, nothing to worry about, take the clutch off and everything but the sleeve gear comes out.

https://www.accessnorton.com/NortonCommando/tti-gearbox.29681/

worntorn said:

This will be fun to try. I could just temporarily block the crossover.
Come on Spring!

Glen

Click to expand...

Or make a valve?

I posted this before, but ages ago I made a valve in the crossover tube, that I could operate with a choke lever on the handlebar.
Assuming it made any difference in power, then riding at a constant speed and opening/closing the valve should have made the bike accelerate/decelerate.
Nothing happened..

ludwig said:

Or make a valve?

I posted this before, but ages ago I made a valve in the crossover tube, that I could operate with a choke lever on the handlebar.
Assuming it made any difference in power, then riding at a constant speed and opening/closing the valve should have made the bike accelerate/decelerate.
Nothing happened..

Click to expand...

You appear to rely on the cable just to open/ close, with no strong spring to keep it closed. The exhaust gasses will overcome this, if you really want to know what's it like to have the exhaust blocked up, push potatoes hard up the ends and feel the lack of power!

Did it make a difference to perceived acceleration?

ludwig said:

Or make a valve?

I posted this before, but ages ago I made a valve in the crossover tube, that I could operate with a choke lever on the handlebar.
Assuming it made any difference in power, then riding at a constant speed and opening/closing the valve should have made the bike accelerate/decelerate.
Nothing happened..

Click to expand...

Did you notice a reduction in noise at all with the valve open?

ludwig said:

Or make a valve?

I posted this before, but ages ago I made a valve in the crossover tube, that I could operate with a choke lever on the handlebar.
Assuming it made any difference in power, then riding at a constant speed and opening/closing the valve should have made the bike accelerate/decelerate.
Nothing happened..

Click to expand...

Wouldn't you have needed a valve at each end for the results to be conclusive?

Bernhard said:

You appear to rely on the cable just to open/ close, with no strong spring to keep it closed. The exhaust gasses will overcome this, if you really want to know what's it like to have the exhaust blocked up, push potatoes hard up the ends and feel the lack of power!

Click to expand...

This is a crossover pipe, so there would be alternating pulses either side of the flap!

Bernhard said:

You appear to rely on the cable just to open/ close, with no strong spring to keep it closed. The exhaust gasses will overcome this, if you really want to know what's it like to have the exhaust blocked up, push potatoes hard up the ends and feel the lack of power!

Click to expand...

Perhaps you are not reading it like I am? What I see is the bowden (choke) cable is used to close the flap, friction and even hand pressure on the operating lever will help keep it closed, the spring is there to provide an opening force when the bowden cable is allowed to return to slack condition.

SteveA said:

Wouldn't you have needed a valve at each end for the results to be conclusive?

Click to expand...

Maybe, but for me the results were conclusive enough to ditch the ever cracking balance pipes.
I believe Norton introduced the balance pipe together with the quieter bean can silencers.
My test was with open peashooters.
baz: the sound changed, but quiter ? .. hard to tell while riding the bike.
Anyway, it is all a long time ago. Still have that pipe lying around somewhere.
If worntorn likes to repeat the test, he can have it..