Exhaust, tell me why....

[sirch345]

Dyno runs here cost more than drugs.

I was wondering if there was a reason to why this was restriction was in place. A blanket dont touch it without reason does not help much.

But I will crawl back into my hole like a good little new member.

Dyno runs are not cheap in the UK either unfortunately.

I understand what you are saying, but the reason I didn't add to my first post was because Lloydie beat me to it, by posting it is a tuned system.

The standard system is a tuned system

Also a quick reply to stop you going ahead before it was to late.

Over the years I have been involved with the Firestorm/Superhawk I have read for's (as in that link you tried to post from the OZ site) and against removing that restriction, but I haven't come across any hard evidence to say it's an improvement to remove it. That's where a dyno of before and after would have been ideal. I'm not sure it that information is available in the archive that Hawk mentions.

There's no need to crawl back into your hole,

Chris.

[8541Hawk]

Well to add a little more personal experience with exhaust systems now that I have run the Akro full system for a while and have it dialled in as good as I can get it.
First adding a flo-commander really did help with the "fine" tuning. No real "power" gains per say but it does say a little time if you are a anal as I am about your carbs.

So as far as the restriction- no restriction argument I have stated the info I was given. Of course I got it about 3 days after I had removed the restriction so..... all I can say is the stock header with a set of slip-ons (once you clean up the welds at the mounting collars) Does give the best ridablity with stock compression pistons, no matter what other mods you do.

I haven't had the bike on the dyno since I mounted the Akro system but while the bike "feels" like it makes more power down low, the bike is not as "smooth" with it. So it might just be the weight difference coming into play as IMHO stock compression really doesn't have enough gas flow to take advantage of the larger header. Though the front end comes up real quick if you get a touch frisky with the throttle. Once you get past the 5-6K range then there is a definite power advantage to the full system.

The reason for saying the low end might just be weight is there really is that much of a difference. My full system with the cans mounted weighs less than the stock header without the rear cylinder link pipe, at least by my cheap bathroom scale....

So IMHO by what I have run myself, if you have stock compression then they stock header (once cleaned up) will give as good if not better performance than anything else you can run. The stock mufflers have to go but other than that it is a good system with or without the "restriction" personally I would leave it in but do whatever lets you sleep the best because it really isn't "notable" either way. You might see 1-2 hp on a dyno chart but you will never feel the difference in my experience.

If you up the compression, it is a whole different ball game as the optimum tube size is larger with the higher gas pressure. Which system to run is up to you and do your research as not all aftermarket systems are created equal IMHO. Also the good ones are getting tough to find and are quite dear if you do find one.

Of course YMMV

[NZSpokes]

Thanks Hawk.

Im coming to the conclusion Im expecting a bit much of the set up. I do track work as well and want a very strong top end. And a strong low end for commuting. All on a stock motor.

So im thinking about running 2 sets of carbs. Thats a story for another day.

To me the stock pipe is very restricted, especially the rear cyl. But if it works with stock low comp then so be it.

[VTRDark]

want a very strong top end. And a strong low end for commuting.

That's wanting the best of both worlds. Carb work wont affect things too much, it's engine work you need for any real gains, especially cams/timing if you want to play around with the position of peak power. but you would have to sacrifice either top or bottom. The two carb idea is not a bad one. Maybe have one set up for K&N, Piper or some other high flowing filter for some little gains on top. Then the other set of carbs set up for OEM filter to give more low/mid.

(:-})

[Stephan]

Strong top is useless on this bike, unless whole bike is heavy modified. It is still too slow comparing others. I prefer track riding on street ready bike :-)

[tony.mon]

High comps, decent cams(not too high a lift) an ignition advancer and a system will give you what you need. You don't purely need top end- you'll always lose out to a decent 1000 IL4- but you will, with the above, be able to gt out of corners quicker and make them work hard at catching you on the straight before holding the inside line annoyingly at the next corner.
The craic on a track day with these is not being faster than everything else, but making it real difficult/impossible to get past you

[Stephan]

Hi Tony, currently I have spare engine and think about JE pistons. In my engine I run ex cams on intake. Is it worth to do some grinding on intake or do I need welding? I will slot the cam wheels for adjustment for sure, and think about slight change on ín, ex profile I would leave as it is.

[tony.mon]

The " 2 pairs of exhaust cams" makes very little difference, if any- but every little helps, I guess.

I had some cames re-profiled. They ground away the base circle to leave a higher lift, and I gained approximately 1mm of lift and 10 degrees of dwell. They need thicker shims than a normal cam set to compensate.

Slotting cams will only help if you carefully set them up with lobe centres set to a specific point, and dyno the results each time to see what the difference is.
This isn't the sort of game that can be tested using the seat-of-the pants evaluation method.

If you're also fitting high comp pistons you will also need to check piston to valve clearances around tdc

[Stephan]

thanks for info :-) So if I understand correctly, just grind away the base circle is enough, and there is no need change profile? For the decent performance.
I want adjustable cam wheels just for fine tuning, my mechanic says there is some space to get better settings with current cams.

[tony.mon]

thanks for info :-) So if I understand correctly, just grind away the base circle is enough, and there is no need change profile? For the decent performance.
I want adjustable cam wheels just for fine tuning, my mechanic says there is some space to get better settings with current cams.

Grinding away the base circle leaves a wider lobe, and so you could increase dwell as well as increasing lift.
Or you could just increase lift.

I'd discuss it with the cam grinder- they normally have a pretty good idea of what's possible and what advantage there is.

I'd also ask your mechanic what changes he is proposing- advance or retard on either or both inlet and exhausts, and whether he proposes increasing or decreasing overlap, or leaving it the same?
If he can't give you specific information, and explain why he thinks that it will be better and why, I would find someone else.

You will either get more torque and less horsepower, or more horsepower and less torque- it's difficult to find a change in settings that just makes more power everywhere. If that existed, maybe Honda would have done it?
On the other hand, if he finds a "magic bullet" let the rest of us know, will you?

[Stephan]

You will either get more torque and less horsepower, or more horsepower and less torque- it's difficult to find a change in settings that just makes more power everywhere. If that existed, maybe Honda would have done it?

Yeah, japanese engineers know their job, that´s why we all ride bone stock bikes ... :-)

Regarding adjustable cam wheels, my mechanic said there is space to set valve clearances more accurately, that´t all.

Right now I have no idea which way to go with cams, I will go deeper into when it will be actual. Before that time, I try to gather some relevant info, and you are one of a few who can give.

[VTRDark]

For lobe separation angles and inlet and/or exhaust advance or retard effects, here's a good guide to what effects what.
http://www.compcams.com/Pages/413/cam-t ... angle.aspx

(:-})

[Stephan]

thanks Carl :-)

[tony.mon]

That one's in the library, good man, Carl

[VTRDark]

Here's another one, Camshaft calculator. Found it when doing the valve opening and closing times diagram



https://www.rbracing-rsr.com/camshaft.html
Scroll down the page

There's a few different calculators on the net which I tried, but found the above simple and easy to use.

As most of us know the exhaust, cams, pistons, timing etc all work as a team and when one thing is changed it has an effect elsewhere. Whether that is going to be a negative or positive effect is something else. Now here's the question, timing and exhaust pulses! When one is designing a high performance engine, should one choose an exhaust system and design the engine around that to get the most from the exhaust pulses, less waste. Or should one design the exhaust system around the engine/timing.

(:-})