R&B Racing LSR Primary dia.

[laserp]

I,m settling in on the LSR C style. I have a SE 103 CI on my 02 Softale. SE HTCC heads, 251 cams, SERT, running Rinehart Shotguns. Right around 100 HO, 108 Torque. The question is 1.75" or 2" primary pipes. Anyone have any real experiance to help my decision?

[frisco-rigid]

Hey Laser

I have experimented with larger OD header pipes and many many diff muffs and baffles etc etc, over many years..

I always find more seat-of-the-pants power from 1.75" headers about 30" +-..
Actual length is kinda up to the rider to experiment with cuz inches, cams and intake and timing make it near impossible to recommend a definate length..
Cut and run,, cut and run,, cut and run,, then if need be weld some back on..

Then I've always gotten more perceived power from a muff or Good Baffle at the end of those pipes..

My 2 113" S&S motors came with a 1.75" recommendation as did my 127" from Ultima..
I also run 1.75" with my 120" and the 93" shovel..

That's been my Hands-On experience..

BUT,, I've heard some good input about those "stepped" pipes..
Have a ball

[laserp]

Frisco, Thanks for the great feedback. Your consistant with what R&B recommends. They say go to 2" over 120, unless you are going for a drag bike, with high compression and looking for high end HP.

What's your experiance/opinion with 2-1 VS. 2-2 Pipes regarding performance? My goals are to reduce rider noise fatigue ( 1 of my pipes dumps out at my ear), improve my high end w/o sacking my low end torque, along with getting O2 ports for an A/F meter. Of course I also want it to look good too.

[frisco-rigid]

GadZoooks---
You don't want much do ya..!

Actually I am NOT consistant with what R&B recommends, I stay with 1.75" with my 120" and 127" and am very happy.. And I run fairly quiet muffs..
I once read where Donney Petersen also likes 2" + with BIG motors but we cannot always agree, I get better perfomance with my 1.75"..
Larger OD might enable a wee more high-end but robs from bottom end..
How often are you waaay up there..
Free flow muffs with correct length and correct A/F and timing-- that's where the power is.. You're EFI huh, not as easy for you as for me..
Are those Shotguns baffled or muffed,,,, and I bet they're short too huh..
That ear will like old-style (down low) 2-2 of correct length with muffs..
If your muffs/pipes/exhaust is too loud you might be losing power,, Noise Does Not Equal Power..

Getting 02 sensors/gauges is interesting, I have them on 2 vehicals but not sickles.. I did tune my 390" somewhat with it but, I dunno, I find myself looking at it too much..

I was going to do it with my sickle motors but after thinking about it prob won't.. I jet very successfully by Plug Color and Seat-of-pants.. However----
Wrightturn has or is going to install on his sickles, get some feedback from him on that.. Hellooo Wright------

I have experience with 2-1 OEM style but Not the newer Performance units..
I have heard good about them..
I cannot run them cuz of my Kick-Only motors with floorboards,, they don't make for both..

Gee, I wish I had more for ya but there is No single majical part or procedure for Big Power,, gotta do it all together.. Sounds like you're on the right track though..

[unclepsycho]

Holy Moly Frisco !!! You kicking a 120" and a 127" ??? That's gotta be fun.
I built a bike with my buddy and it was a 95" kick only, and that was a challange. made for long pit stops on the road trip when she didnt wanna fire right up after a gas stop. I had to put compression releases on my 100" to help save the starter......

[frisco-rigid]

Hey Unc

Yes, all the sickles I've built are Kick-only and I only ride what I build..

The 120" is 10.5 - 1 and fairly easy cuz heck, I've been kickin for years..
It actually starts a wee better with points and I've found no diff tween points and Elec. ign.'s when it comes to performance..
Sometimes at a short stop like for gas they do get a wee tempermental (especially in Our Summer Heat) and require some coaxing for sure..
For Kickin,, perfect tuning is essential, I'm sure you know that..

I put the 127" in Magnolia Blosoms old FXR.. She must use the Comp-releases to ease the starter too..
It'll go into a Kick-only after she totally breaks in all the bugs, there's been a few.. And then there'll be another Big motor..
At 61 I figure I'll try to run us outa gas before this new Pinko-Commie totally shuts us all down..
Yeah Baby..!

[HarleyCruiser]

Originally Posted by laserp

The question is 1.75" or 2" primary pipes. Anyone have any real experiance to help my decision?

You tune your exhaust to match the RPM range where you want the performance.
And if you want around town performance or bragging rights on the dyno.
When you get too large a dia, the velocity of the exhaust flow is to slow at low RPMs.
When the velocity falls off so does the scavenging effect.
Scavenging is like a siphoning affect.
The advantage of a 2 into 1 is that it helps scavenging at low RPMs.
Each cylinder helps the other by keeping the exhaust flowing, instead of stopping and starting, this kills scavenging.
The larger pipe helps in higher rpms, where the smaller pipe will surpassed it optimum velocity, and instead of scavenging, the exhaust has to be pushed out the exhaust.
This causes excessive back pressure.
The dia also determines the sound of the exhaust, so if you are tuning your exhaust to match your sound preference, then it is a different story.
I like the look of that particular 2 into one.

[laserp]

Frisco - Man, you have an old school style to admire! Got any pics of your sickles? I'm with ya on the 1.75 primes. I ordered up a set of the R&B LSR's - went C style, turn out, 45 down. I'm hearing some horror stories about cust. service...keeping my toes crossed.

The A/F meters is the engineer in me.. Probably kidding myself that I'll be able to tune, but I am pretty up to speed with the SERT and mapping. Right now, I got a kick ass map for my bike, done by R&R, I don't know about a fish, but they can tune a bike! Great crisp throttle, very nice torque curve...no dip, very convex from the get go. I'm hoping that adding the pipes will require only minor mods to the map. I'll end up taking back to them for a final tune, but I want to be able to control my own destiny to a point. I'll try not to stare at them too much.

Hey HarleyC - excellent explanation for me, I'm somewhat of a laymen when it comes to engine performance details, but I'm learning.

Oh... Frisco, my Rineharts have baffles, pipes are not too short.

[frisco-rigid]

Hey las

Aahh shucks, thanks......

It really does sound like you're on the right track..
Especially that you want to control your own joy, yeah baby..!
You'll be doing the exhaust install and set-up of the 02 sensors huh, good man..

I'll be anxious to hear how it all comes out..

I posted a photo of my 93" Shovel back in '05 but I have no idea how to find it after this forum has been changed a couple times..

[Wrightturn]

Hey guys,

Haven`t done much with the A/F meter lately. When you set up the O2 weld it closer to the exhaust port. I am bartering for some dyno time to calibrate the meter. I have a gear drive conversion coming up on an 08 and already have a pipe welded. Going to tune the PClll with the A/F meter and confirm on the dyno. Mixture and load will be much more interesting.

In my spare time (?????) I will learn to use my camera and post pictures.