He's from mt gambier Davo like me

Yeah bike goes ok. Was expecting a bit more. If you go by Harleys advertised power out puts it's a bit low. Had I heard of Hoody a bit earlier I have given him my budget and said go your hardest. Live and learn I guess. Won't be spending much for a while just put stinger wheels on and true track.

Where do you live Dynoharley, Edenhope ? Ride through there a bit. Is that Avatar a picture of your bike. Cops give you any grief over the turbo. My wheels below. 

 

Hi Dynoharley (Davo is it ?)

Yeah it's the crate 120r. Had Horsham Harley fit it when I bought bike new 12months ago. Have the SE manifold and 58 throttle body. After talking to Dan Kiddo ( not sure if that is spelled right.) from Narracorte I wish I had gone the hurricane heads pistons etc..  I thought about going turbo but was worried about the cops with such an obvious modification. As I said I have used up my cash for a while but I would love some more grunt. Ride for a while to get some value out of what I have spent then see what more can be done. Acceleration is what I like I have enough top end. Thought 120 cube would be a tire shreader  but it's not much better than the 110cube cvo's from the show room.  When is the edenhope pub run I like having a beer with like minded people if anyone is invited of course.

Cheers Dutchy.

Dutchy, those headers are holdng you back at least 5 hp compared to a set of Fatboy headers. 

Hi Ando,

Getting 118 horses 118 torque rear wheel. Was expecting 130ish horses and the same torque. I just want to make something clear though because now that I reread my post sound like I was not happy with install or set up. I think Brett from Horsham did great job as bike runs smooth and is excellent on juice I use about .5 to 1ltr per tank more than guys on standard bikes. I think that the Harley Davidson company has inflated figures on this engine. 

Dutchy    

Hi Lushy,

Was going to call you when I am cash up again and ask what your suggestion would be on pipes then get you to dyno it. But I did not want to waste your time until I was ready to roll in cashed up. I originally had Vance and hynes big radius 2 in to 1. Was not happy with them as it did not seem right. Then I listened to some one I should not have and played with the baffles in that pipe. Then cleaned out the standard headers of valve and cat, put on s&S slip on.

Cheers mate for your interest.

Dutchy.

Thanks Ando,

Sounds like there is potential in my engine left then, Thanks for the feedback makes me feel better know I can make further changes in the future. Have been told by others there was not much more that could be done to make it go better.

Dutchy your last statement there is some pretty bad info lol, who the hell told you that?

Daggs I'd rather not say that where everyone can see. I don't like bagging people especially if they have helped me out. I will message you on FB. You going to edenhope ride.Got and dates on that. I'm getting edgie I recon I 've only done about 600 or 700km in the last fortnight. Waiting for some good weather which cone sides with days off. Been caught in the rain  a lot lately.  

Ha ha yeah all good mate, I didn't really mean fir you to say who, like I said check the interstate forum for info on the pub run, it's a good weekend for sure!!

Exhaust is definitely the make or break of any combo ,sweet running stock up to high performance street {track exhaust is a different topic}| ,stock headers without cat or butterfly will handle over 130 + hp no problem ,part of its about gas speed {300fps} this is not difficult to calculate,

Piston speed X Bore squared 60 Pipe id squared

You will find the 1.625” stock id pipe capable of some decent numbers when coupled with a high flow muffler like a S&S taper turbo with a 27mm baffle spread, I know it works as this is what I run on my bike, Its not ear bleeding loud or blatty for lack of a better description, we know we are nearing the limit of the pipe in my situation but I am turning more rpm than most. The US or Japan market rear header is desirable in my case as it has not got the cast in restriction of the butterfly assy.
A change of just 1mm in pipe id makes a big difference to the 300fps calculation, its time for a few guys to get the calculator out instead of the catalogue!!!
Pipe lengths are a bit of a given but this needs to be addressed as well if you are aiming for a number,, at least have them the same length if nothing else,, Short pipes peak late if the engine can get near the rpm the pipe dictates and long pipes peak early and nose over with rpm, the stock length system is actually doing you a favor when you do the math..
Pipe manufactures get far more market slice from pretty than performance.

The calculation did not come out as i entered it ,,it goes Piston speed over 60 multiplied by engine bore squared over pipe id squared .

Thanks Hoody I recon if I try to work those numbers I am sure to stuff it. So I think when I am ready to ask Lushy to tune it I think a will ask you or him which pipe to buy. Bit short on the dollars at the moment but it still goes ok until then. What's funny though. With the 120r, standard headers (fat bob.) no cat or valve and S&S slash cuts, it's one of the quietest bikes among the guys I ride with. That's until about 3500rpm then I'm told it's one of the loudest. Also had some guys say it sounds like a twincam until then and a Vrod after.

Has anyone had any experience with the hurricane heads and 12 to1 comp pistons on the 120r (also has different cam). I was talked out of it as I was told it would not run very when on pump fuel on the road. ( or a view on it )

Cheers Dutchy

  Piston speed is fpm and most of what I put up is in imperial    ...When we did my Sporty some years back we found the pipe to be restrictive ,bear in mind this was 100 cu/in  designed to turn well over 7000rpm {a bit in the same vein as the 106 this post is about} ,the difference between 1.5/8” and 1.11/16” {.062”} is a full 7% pipe cross sectional area increase ,I did make the 1.687” id pipe with an adjustable slide tail pipe to tune length ,,I rode it around the block, it was ear bleeding loud  ,,, I decided that my rego/licence was more important than the top number.

The graph below shows what i am talking about with top end flat lining ,the two upper lines were stock 1.5/8"id  headers with cross over with S&S taper turbos unmodified {red} and good old Jimmy boys from Outer Cycle in Melbourne {blue} not much diference is there,,,, the lower black line is a set of show room floor stockys that after a bit of tuning made nearly 100hp ,i rode it like that for a while ,the motor was louder than the exhaust and it would lift the front wheel just rolling the throttle on from the lights,,,,

I Just saw an old fart with a white helmet on a Sporty pulling monos ,,,that can't be happening!!

Lushy and i tried 3 exhaust combos that day to see where it would take us and give us something to work from ,,,we are still testing and trying out today .

 

 

Hoody , when I run the formula as you described, I get 437.2
Piston speed at 6600rpm approx 5000fpm
bore 4.125"
pipe 1.8"

Not sure if my calc is correct, but if 437 IS the number can you explain to us what that would tell you and what unit of measurment are we calculating, is it FPS?
Cheers for the great info.

1’

Average piston speed is defined as follows,   Stroke in inches multiplied by RPM  divided by 6  ,so if you have an engine with 4.625” stroke and using an rpm of 5300 for the calculation it would be   4.625 x 5300 divided by 6 =4085fpm

2,

This was always going to be a can of worms but here is a brief description and I will keep it brief  ;,,   The piston speed we want is the speed generated at the mid of shift point so lets call top of shift  5800rpm and bottom of shift  4800rpm ,{5800+4800 divided by2 =5300} mid point rpm is 5300rpm ,so ,stroke  is  4.625”  x  5300 rpm is 24,512 divided by 6  = 4085fpm piston speed ,,Your bore {4.125”} squared is 17.01 and if you used a 1.15/16”, 1.937” id pipe which squared is 3.752  the calculation will go {4085 x 17.01=69,485} 69,485 divided by {60 x 3.752=225.12} 225.12  = 308fps this is more than acceptable .

.I know a lot of people think the rpm figure I used was low but bear in mind your shift point is just after peak torque not at peak limited rpm ,  ,if you shift after peak torque at a point that puts the engine back  into the middle of its peak torque you will generate a higher spool up rate in the engine hence optimal acceleration on the track ,,,you actually lose time by over rpm’ing the engine as the engine takes longer to get there ,that is why sometimes in a race you can  out run another bike at the launch {if the launch and traction are the same} but see the other guy reel you in a bit at each shift till he is unfortunately passing you slowly but surely passing you, in this circumstance it would be beneficial to short shift if it is known your engine performs better than the other ,,,Its not all about horsepower it includes a good level of riders skill..

Here’s one to ponder,,, ET is rider skill, traps mph is horsepower.

 

Cheers, I understand some now.
So, an actual calc showing an fps higher or lower than 300fps tells us what? Is 300fps our goal? Is this where pipe ID comes into play, to speed up or slow gas flow?
And if you were tuning exhaust for the track, using higher rpm calcs, is 300fps still our goal?
Once again, thanks for taking the time. Helps me a lot to understand whats going on at the noisy end.

Having a gas velocity in the 300fps +  or -  10 fps range at an rpm that is mid of the shift point as discussed earlier is more to do with optimizing cylinder scavenge and minimizing exhaust gas reversion into the inlet tract at the intake valve opening point ,this phenomena is even more pronounced as we go up in valve overlap timing associated with performance cams ,so we can generate a condition if the pipe is too big, velocity will drop and exhaust scavenging will be reduced  and if the pipe is too small  the velocity will increase to a point where friction between the pipe wall and the exiting gas is high and increases back pressure .

The origin of these calculations is based in recorded race tuning data available in a number of very good publications.

All that said it’s a starting point not a rigid rule ,it will get you closer, sooner to where you need to be,it may even help avoid unexplained power issues ,its better in street engines to err a bit  smaller than ideal as this will give better low and mid spread power .

It was many years ago at a drag meet that I saw an evo engine that was supposed to be the “be all and end all” of expensive parts and effort no end, launch from the start line with what appeared to be fuel stand off at the ram tube ,and hearing it falter then clear ,it stuck in my head till I got to talk to a person I knew from circuit racing, after describing the observation he asked questions about the exhaust among other things  and he pretty much nailed the problem as it was ,I knew the guys running the bike and told them of the discussion ,they said the pipes were supplied by a recognized performance exhaust fabricator ,,,they changed to smaller pipe with a longer length from the same fabricator ,,bingo ,,no reversion and a solid gain in performance,,,That guy gave me a lot of good advice some of it is here in this post..

 

Sounds like a properly set up shift light could help with acceleration. Also sounds like I will be more interested in torque than top end horsepower. For me it's the acceleration that I get off on. Love dropping back gear or two and blasting past cars, trucks & bikes. Just can't quite stay with the 1000cc jap sports bikes. Well until 220 anyway.