Lollipops, baffles and backpressure.

Recent threads on variable baffles have got me looking at the whole concept of baffle design. Most pipes can be run without baffles and apart from being deep and very loud you will notice the lack of backpressure, probably meaning less torque but maybe with higher top end speed. Most systems come with removable baffles that have a solid backplate with perforations around the sides to let the pipe breathe. I notice a distinct improvement in backpressure when I ride with baffles in but love the deep thud without. The baffles tend to make the pipes sound a bit raspy with the air being squeezed through that mesh. So rather than making variable baffles I have decided to experiment with a fixed lollipop which is halfway between the standard baffle and an open pipe. I wanted more air flow around the outsides to give the deeper/louder note yet a solid plate to maintain back pressure. I fitted these inside my cut down/turndown tips but they could just as easily have gone straight in the end:





At first the backpressure was so great it bent one of the brackets towards the back so I made them more stubby. The sound is about half way between perforated baffles and open pipes but with good backpressure. I was a bit fed up with all or nothing (baffles in/out) so this is moving towards the optimum: performance vs sound. The plates are standard repair washers - about 70% of the pipe bore. The metal went black within a few miles and it is very hard to see what's in the pipes when you get down and stare. I will see how this one goes but I rode about 30 miles today and liked them.

Well in John it is nice to see you are still cracking on with your experiments.fair play to you.Hope you achieve your goal.

good job john sounds like youv found or fineding the happy medium between sound and performance well done mate

alfie92 wrote:

Well in John it is nice to see you are still cracking on with your experiments.fair play to you.Hope you achieve your goal.

I suppose goals we achieve are measured largely by the amount of fun we have on the way!

Yeah I guess it just a matter of keep playing. You may even find that you get a different sound by doing things like: Having the lollipop to one side rather than centred, having the lollipop cone shaped & so on. Its one of those things that I find enjoyable but then I, like you, love to tinker.

Good one blues.

I like the fact that you can so easily go from baffled to debaffled with the wing nut, you just need to make sur you use spring washers so that they dont vibrate loose & fall off

captain crash wrote:

Good one blues.

I like the fact that you can so easily go from baffled to debaffled with the wing nut, you just need to make sur you use spring washers so that they dont vibrate loose & fall off

Good point - they have not shaken loose yet but I'll sort out spring washers tomorrow.

Boy has this mod made a difference! Bike seems faster, partucularly low down. I love the sound - nice rumble, loud (but not thunderous!) and the note when backing off the gas is very similar to that when accelerating. I found with the baffles removed completely, the low notes irritated my ears when coasting. I sprayed inside and pipe extensions with nice matt black yesterday. I think they will pass for aftermarket baffles, rather than Bluesman bodges now! I can thoroughly recommend this mod - for me this is my pipes with optimum sound/performance. All I need to do now is fit spring washers (thanks CC) and that's me done. One problem - my Harley seems underpowered now!!

Such a simple mod has given back pressure, increasing engine output & a lovely sound all at the same time.
Love it when a plan comes together John

John this thread has really got me thinking about how exhausts work and I have been reading a lot on the subject because of it.
It is reported widely that by modifying the stock exhausts (even with no other mods)the bikes run better and I am an advocate of that. It is also reported that by adding an aftermarket exhaust (even with no other mods), the bikes run better and I am also an advocate of that. What we need to consider though is that small changes to the air flow will be taken in by the engine management system and dealt with but larger ones will go outside of it's capabilities. I believe that with the baffles in your straight through pipes the management system is able to cope but after removal of the baffles it isn't.
The fact that you report that the bike is running better because of the lollipops proves that the bike was running very lean whilst they were used as a straight through only. As we all know very lean is a bad scenario because it will (at some point) cause the valves to become burnt.
As you have not added a fuel processor to compensate for the extra air flow that the engine was dealing with, because of the lack of back pressure. The fast flow that the exhaust were allowing could very well have meant that you were running at less than stock power because the already stock lean bike was unable to make such a big compensation within the fuel management system.
By adding this modification to your exhaust, you may very well have taken the bike from performing at below stock power, to somewhere near peak within the limits of the management system for this level of modification because by adding the back pressure that you didn't have whilst running without baffles you have reduced the leanness of the running condition by reducing the external flow and that is why you have noticed a performance boost!

Just my opinion

Mr Intruder wrote:

John this thread has really got me thinking about how exhausts work and I have been reading a lot on the subject because of it.
It is reported widely that by modifying the stock exhausts (even with no other mods)the bikes run better and I am an advocate of that. It is also reported that by adding an aftermarket exhaust (even with no other mods), the bikes run better and I am also an advocate of that. What we need to consider though is that small changes to the air flow will be taken in by the engine management system and dealt with but larger ones will go outside of it's capabilities. I believe that with the baffles in your straight through pipes the management system is able to cope but after removal of the baffles it isn't.
The fact that you report that the bike is running better because of the lollipops proves that the bike was running very lean whilst they were used as a straight through only. As we all know very lean is a bad scenario because it will (at some point) cause the valves to become burnt.
As you have not added a fuel processor to compensate for the extra air flow that the engine was dealing with, because of the lack of back pressure. The fast flow that the exhaust were allowing could very well have meant that you were running at less than stock power because the already stock lean bike was unable to make such a big compensation within the fuel management system.
By adding this modification to your exhaust, you may very well have taken the bike from performing at below stock power, to somewhere near peak within the limits of the management system for this level of modification because by adding the back pressure that you didn't have whilst running without baffles you have reduced the leanness of the running condition by reducing the external flow and that is why you have noticed a performance boost!

Just my opinion

Yes that all seems to make sense. When I had my 7500 service I asked the mechanic to show me the plugs. We both agreed they looked the perfect colour. This was after I had been running with the baffles in for 2-3 thousand miles. Probably in the short time I ran without baffles the engine was struggling a bit although it did sound good. Now I have replaced the open pipes with my 'lollipop' baffles, as you say, the bike is probably running near peak. It will be interesting to hear how other members are getting on as I know a few have the same HH short cuts and at least one is running without baffles. I am more than happy with how they sound/perform now but it is nice to have a bit of a tecnical thumbs up too - thanks for that. I noticed today when adding the spring washers that the new baffles rotate nicely and quick too into the almost 'no baffle' situation. I will be honest and say I may use this setting now and then for vanity reasons - there is a guy where we all meet locally who likes to think he has the loudest pipes in the universe (straight through Raasks on an 800 Marauder actually!) When I pulled along side without baffles last week (large bore short cuts almost like no pipes at all!) his face went green, so I think mine may have put his nose out a bit. Just a bit of fun really to amuse the boys! Most of the time though I like things a bit more civilised and with a bit more consideration to the bike, to boot!

I love this lollipop Mod.
It gives such a wide diversity to the exhaust with it's simplistic design, allowing the ability to switch from being a nice neighbour to a bad arsed biker in the space of a minute.

Yes actually if you used a slightly bigger washer you could almost have sounds in the complete 'quiet bike' to 'noisy fecker' range. I think my quietest is more in the 'lively' category.

I've just came back from the garage.

I decided to follow John's design before I give in to more spending and making it more complex.

In short...the bike sounds worse.
Idle turned from deep rumble to "pat pat pat pat pat pat" and under throttle it appears just slightly quieter but lost the rumble too.
In addition the exhaust started spitting water. I never saw that but I guess that was the result of engine warming up and condensation gathering on lollies since they're in the way of gasses.

I'm quite disappointed after all the work and money spent...

Tomorrow I'll take it out and thrash it a bit...maybe the difference will be higher up.
For idle...no lollies is a definite winner.

MarcinG wrote:

In short...the bike sounds worse.

That's a shame, They look like you've done a nice job

Perhaps think of the lollies for quietening the bike down to leave/arrive back home almost silently. Doesn't really matter if they sound rubbish for a mile or so then stop and open them right up. I never really experimented with mine much on the open road although they seemed ok on tickover. Looking back on all this sound control business I have become a bit philosphical. It's probably impossible to have a quiet bike and a noisy bike in practical terms - it is one or t'other I suspect. I was never totally happy with a lot of noise nor with stock levels. It's probably something about having the balls to run loud all the time but I found my sense of social responsibility crept in now and then and made me feel uneasy. Perhaps the answer is with the correct degree of baffling to get a 'noisyish' sound. The American electronic baffle is probably the only practical soluition but expensive. I can't help thinking it must be bloody horrible living next door to someone with a noisy bike but I just love the sound of full on cruiser pipes.

I honestly don't know what the answer is here - maybe there isn't one!

In the weantime - Well done Marcin, yours look neater than mine!

PS I still think the easiest way to escape quietly is a piece of wood rammed up each pipe and taken out before the bike senses something is wrong and just stops!

Yes, that was the idea John... put them in, leave, take them off when clear of moaners, hence the wing nuts. Too bad they haven't done much noise wise...still loud as hell...

Thing is, after wrapping the baffles I completely fell in love with the way they sound... idle is glorious, under acceleration is brutal and odd blips when coming to stop are just pure awesomeness. It just grows on me every time I go out.

Social responsibility... does my head in as it makes me feel uneasy as well...but I like my neighbours and communicate with them a lot regarding what will be happening (they've been warned already that Sunday morning won't be quiet when I'll leave for Peterborough)
I could easily say "F*ck it" and run loud and proud but that would be short lived... As a husband, father and professional progressing some form of viable career, the last thing I'd like is the neighbours, council, Police (or mix of) trying to make my life a misery legally.

I envy everyone that don't have that problem and run loud and strong.
Maybe one day...

Regarding design, thank you. I tried my best to make it look "clean".
I actually build it in such way that it fits in one of the baffle screw holes so no modifications were made to the pipes.

Conclusion...Jardines are untameable
Designation - mainly for events
Daily rides - welcome back stock

Unless they make Peacemakers for Intruders, I'm screwed :)
I guess I need to stock up on gaskets and some spare cylinder screws for pipes.

MarcinG wrote:

I envy everyone that don't have that problem and run loud and strong.Maybe one day...

It's like living next to a train track, Once you get used to it, You don't even notice it

Marcin they are not untamable mate, your nearly there but your lollipop is to small. If you want to quieten them down just for short distance runs, leave only a couple of millimeters of gap around the edge, anymore than that and they wont work that well to allow you to escape your neighborhood without being detected.
By the way, you have manufactured them really well from what we can see.

Good job matey, like dave says though the lollipop will need to be a lot bigger and it will only be usable in reality for a short distance to get you a mile or two away from home if you go big enough to make them very stealthy as when you restrict the airflow that much your engine will be running richer than Richard Branson if you give it to much throttle

Hmmm bigger you say. John's don't appear bigger.

The exhaust is roughly 7,5cm... I can see washers that are 7 and 7,5.
I reckon it would have to be 7,5 to fully fit into the pipe and then perhaps drill 2 or 3 small holes.

It would be literally to ride down the street...half a mile...then I can't be asked what ppl think.
What's the downside of running rich for that period? Will I ruin the engine or plugs?
Saying that, running with Jardines as they are produce very strong pressure pops when the engine is idling.... strong enough to push your hand away a tad... is that due to unrestricted flow and..is that something going wrong?

My pipes were 6cm I think. I used a standard repair washer from B&Q. If you can't get big enough washer, you need one cut from sheet with a hole saw. Try the timber idea - it's so easy - I used 2 pieces of batten in each pipe, wedged in, 6 inches long, painted black - so easy to put in and out - nearly silent - only rode 1/4 mile and then removed and the reverse if necessary on return. When the pipes are cold you can put virtually any secure material in the end as long as the pressure won't shoot it out. Good luck with the lollies if you persist with that one!

MarcinG wrote:

Hmmm bigger you say. John's don't appear bigger.

The exhaust is roughly 7,5cm... I can see washers that are 7 and 7,5.
I reckon it would have to be 7,5 to fully fit into the pipe and then perhaps drill 2 or 3 small holes.

It would be literally to ride down the street...half a mile...then I can't be asked what ppl think.
What's the downside of running rich for that period? Will I ruin the engine or plugs?

Marcin I have just been chatting to dave (Mr Intruder) on the phone and he said he suggested a 2mm measurement to make the pipes relatively quiet enough to ride away from your house in an un noticed way as it would appear you want to reduce the volume a lot so that you can't escape your area without pissing off your neighbors. He said don't forget that if you use a large diameter lollipop that nearly fills the exhaust you have the option of turning the lollipop which will increase the flow which would also have the same affect as reducing the size. The standard way is to stop the sound from going straight out of the rear by making it change direction or restrict its flow and therefore the noise. As you have already added new packing to the baffles which does 2 things with the first being restricting the air flow and the second being making the flow change direction by filtering it, you only have one option left and that is to reduce the flow by a lot.
Although the bike will be running very rich, it will only be for short periods of time so there will be no downside apart from lack of power under anything other than very steady throttle. You must remember though that as the hole gets smaller so to speak, the bracket part needs to become strong to withstand the pressure or it will just fold, so when you get it to an exceptable level don't give it a handful of throttle just to see what it like under higher revs as it isnt being made to be used for normal riding it is being made just for a low rev, stealthy departure, you can easily strengthen the bracket by doubling up the metal bracket thickness by using 2 bits together. The other thing he said to rember is that as you will in affect be restricting the inward flow of air through the filter by reducing the outward flow, your are actually activating a forced external choke, so you will probably not need to use your manual carb choke when starting it so if you go for a very reduced flow lollipop you really need to start riding the bike as soon as you start it, so don't warm it up at all before riding it, just start and go. Also as the reason for this mod is solely to get away quietly it is better to forget what the actually sound is like as that is not the purpose of this mod
Its like anything matey, trial and error is the only way but it is always going to be easier to take a bit off of the lollipop than add a bit, so start with a very restricted flow as suggested and then adjust that as needed

Hi Marcin looks a neat job,good luck on your quest.

Here we go with another "wait up until you test it all".
I was out today for a ride...loud.
When I returned home I though...it's early enough and I shall give the lollies another go, this time outside, not in garage.

Installed them, fired the bike up... shock.
Idle sounds OK. Went for a quick around the block... under throttle sounds fantastic!
Spoken with the neighbour, loves them.

It turns out the garage was the culprit.
Outside they sound very nice and the top end ear hurting bark is gone alltogether.

Woohooooooo I tamed the bloody Jardines after all!!!

With current setup/size, I think I'll be more than OK to ride with them as they are. In fact, I will ride down to Pborough tomorrow with them on.

Need to tighten them up and pack some tools for the road though...don't want to loose them on my way :)

MarcinG wrote:

Need to tighten them up and pack some tools for the road though...don't want to loose them on my way :)

Glad you sorted them mate put a bit of lock nut on the threads to stop them vibrating loose.

good job mate maybe see you there a little earlyer

Glad you sorted the problem out Marcin.

ace!

Marcin the Jardine tamer aka (the wizard.)

Not quite... 15 miles in, one lolly broke from pressure (yes, because I went over 60mph :P )

So they did the job...while they lasted

Pipes are coming off now for:
- gaskets check-up
- so I can remove the rattling screw that I broke off while trying to remove baffle
- and so I can work on my lollies Mark II (really enjoying that now)

I don't want to tweak the design much so I'll most likely go for double brackets. Also, I'll try to sort of a way to heat up the steel when bending and they let it air-cool so it's more flexible (so I've been told)
The only issue I see with having 2 brackets together is the clearance... so if that fails...then it's drill time!

Just a thought obviously dont know if it will work, but if you drill four small holes equally spaced out in your washers to relieve the pressure it may work.

Good thought...but I don't want to make it any tad louder...

Pipe diameter is 7,5cm.. washer is 5cm.
2,5cm gap is (I think) a nice medium to both keep the noise down and keep the bike happy.

For now, just reinforcing the build.

Later, we'll see :)

Possibly reverse the second bracket to form a triangular shape if the double bracket fails - (it may well do at 80mph):



This might be a bit fiddly to fit but I doubt it would bend, at any speed!

This is the type of bracket you need marcin, They're very strong because of the V in the angle, it takes a lot to bend them! readily available from most hardware shops in various sizes

simbo wrote:

This is the type of bracket you need marcin, They're very strong because of the V in the angle, it takes a lot to bend them! readily available from most hardware shops in various sizes

Just the job!

Well found Sim.

"Heavy duty angle bracket" they're called I think.

Brilliant find, thank you... I'm off to Wickes today.

Jardines are off...
...but only for mod mark II :yeahman:

And I'm back in business for evening cruising so woohoo.

It appears that the gaskets I bought will be good maybe for one more change... not much life out of them but then again I don't think they design them to be used several times ;D

Lollies Mark II done.

Now awaiting Carterton event. Sweet.

MarcinG wrote:

Lollies Mark II done.

Now awaiting Carterton event. Sweet.

Carterton event? More info please Marcin.

This one my friend. Mentioned a while ago.

Is the placement toward the end of the pipe important? I did this mod, but installed them about 7in up the pipe and after hearing them...