I've written before, I have a 1989 FLHS that will be upgraded in stages.
This year I am upgrading my suspension, and am likewise doing essentially Stage 1 mods, though this includes the switch to a CV carb from the older style carb that the bike came with. The previous owner had the pipes opened up, I have the CV carb and Manifold, and intend to re-jet it as advised here on the board, and to put in a free flow air intake.

But in the back of my head I keep thinking "You probably should put on a better exhaust to do this right, and you need to remember that next year a Cam, High compression pisons, a re-ring, lifters, rods, and Polished/Rebuilt heads are coming in."

I've been doing homework and I keep going round and round.

I'm an Engineer, I know that 2 into 1 is better.

But it's a bagger.

It wants duals. It wants True Duals. I'm broke.

How much am I penalizing myself because of my desire to stay with duals, and will slip-ons provide ALMOST as much power as True Duals, or am I hurting myself again?

Hard numbers are difficult to pin down, and they sometimes conflict.
I'd like to hear from those that have been here before.
What have you done, what are your impressions, and especially from those who have FACTS, what are your results?

I want to be smart, but if I am only a little less smart, I will keep my MoCo duals, and only do slip-ons.

Thanks in advance for any that care to help me nail this decision down.

 

I found a set of true duals on craigs list for $150. Granted I have lost some off the top end but as I hardly ever go there (I just go there to see where she is at about once a year) I don't miss it.

 

I love it when someone says "It's a bagger and they need duals". Originally all harley's had 2-1, it wasn't untill duals became the thing to have on cars that harley started putting duals on their bikes. Just look at the "older/original H-D's.
Take a look at fullsac if you want to get an affordable true dual option. We've put them on customers bike with great success.

http://www.fullsac.com/

 

true duals- a fashion fad.

yawn

twin cams can get away with it as although they don't make much more HP than an evo, they do make better torque.

alot of new harley riders "think" they are somehow becoming OG badboys- last year they had the 28 piece "Live to Ride" numbered edition picnic set.

true duals give away the free power gained by scavenging, which can only happen when cylinder are connected- it's the reason that the car in the driveway doesn't has separate pipes for each cylinder ( "but wait, dragsters and P51's have separate pipes". Yes, as they do not have to produce any power at low rpms and tend to run within a narrow rpm band, using clutch slip and prop pitch to apply that power- the challenge with a motor is making good power at varying rpms, which means that exhaust/intake tuning, ignition, valve timing are all a compromise)


the stock evo headers ( essentially unchanged on the TC's until the new frame 2009) are easily able to support motors over 100 HP. they are a good compromise between torque and HP--- and they are already paid for.

but it's your bike and wallet.

'53 2/1 exhaust


Mike

 

He said it.

 

Hi RaSH, 1990 FLHS here. I used the Fullsac conversion kit for several years, then a new set of TDs, now a 2-into-1. TDs sound great, but having had my bike set up on a dyno with the new TDs and then again by the same indy when I changed to 2-into-1, I can recommend them over the TDs. Admittedly I have an S&S motor, but it gives around 15% more torque in the low/mid range and is much smoother running. Mine is a SuperTrapp Supermeg. Looks good, sounds fine and rides great!

 

Wow, apparently an offensive question, or perhaps it was not artfully presented. My apologies, I really was just looking for advice on the best approach to take in my restore to ride and enjoy project.

This statement especially surprised me given the intent of my request for help in cutting through the fog of information found while doing my homework on the best approach for me to take to bring this bike up to some level of modern standards.

“alot of new harley riders "think" they are somehow becoming OG badboys-“

Nothing could be further from the truth, I’m an older guy that has a chance to scratch an item off my bucket list, and am a caretaker for a bike that is fairly solid but needs some freshening up, fortunately the finances behind this ownership are such that I can justify the investment to provide some performance and handling enhancements that I believe will not make the bike less reliable. My goal is to bring power and handling up to a reasonable level that will not hurt reliability.

But I did also receive responses that helped me narrow down my choices, and I appreciate the help.

From these responses,

“true duals give away the free power gained by scavenging, which can only happen when cylinder are connected- it's the reason that the car in the driveway doesn't has separate pipes for each cylinder ( "but wait, dragsters and P51's have separate pipes". Yes, as they do not have to produce any power at low rpms and tend to run within a narrow rpm band, using clutch slip and prop pitch to apply that power- the challenge with a motor is making good power at varying rpms, which means that exhaust/intake tuning, ignition, valve timing are all a compromise)

the stock evo headers ( essentially unchanged on the TC's until the new frame 2009) are easily able to support motors over 100 HP. they are a good compromise between torque and HP--- and they are already paid for.

Hi RaSH, 1990 FLHS here. I used the Fullsac conversion kit for several years, then a new set of TDs, now a 2-into-1. TDs sound great, but having had my bike set up on a dyno with the new TDs and then again by the same indy when I changed to 2-into-1, I can recommend them over the TDs. Admittedly I have an S&S motor, but it gives around 15% more torque in the low/mid range and is much smoother running. Mine is a SuperTrapp Supermeg. Looks good, sounds fine and rides great!”

I believe that these either provide the answer, or at least I am getting MUCH closer to the answer for my application.

Thanks grbrown you provided the numbers that proves to me that the 2 into 1 is the better solution with 15% better torque in the range that I am going to run my bike in over the “True Duals” consideration.

Great info. Scratch the TD consideration, and save a ton of money by doing so.

The other info provided was equally enlightening, the scavenging effect along with the opinion that the original factory exhaust is good for 100 H.P. is likewise the type of information that I was seeking. As noted, next year I do intend to have the motor freshened up based on a compression and leak-down test done by my local indy. But it was judged ride able and not an immediate problem, so this will be delayed until the end of this next riding season to spread out my cash outlay during any one period of time.

Presumably the scavenging effect of the existing header set will close up some of the 15% gain between TD’s and 2 into 1’s, and as noted they are already paid for. This may very well be my best “Bang for the buck” option.

Now at the risk of again raising ire, does the fact that a previous caretaker punched more holes in the pipes indicate a need to look for replacement pipes to bring this back to factory back-pressure, or perhaps find well regarded slip on replacements as a cost effective alternative to the 2 into 1’s? Or should I be O.K. with these? They aren’t completely drilled out, but I took them off the bike and peered into them and they do have some holes in the plate that I’m sure are extra. I’m not a “Loud” for the sake of loud guy, and if these holes are hurtful I’d rather address it.

Thanks again.

 

hey the "OG" wasnt a crack at you. I apologize if that's how it came off.

That was more a reference to the 4 posts a day on the touring board that start with:

"I did this to my bike and it doesn't run right, f**k**g H-D "

such awesome mods include, removing a brake disc and caliper, lowering the bike until it scrapes and the rear wiring is ripped out, the paint is burned off the fender and the tire is holed by the seat bolt...

or "I put true duals on and now I have to slip the clutch at stop lights"

and stuff like that from guys with a couple of wrenches and no manual.

Your 89 is a great bike, you really don't have to do much to it.
Yes, the CV carb is a GREAT swap, and inexpensive, cams if you want ( hmm, reliability/result?) rings etc if it needs, plenty of 100,000 mile + evos with untouched motors out there.*
The brakes are acceptable, but you may find a multipiston caliper and front suspension upgrade ( less dive) worth while.
the lifters may need replacement earlier than other motor parts, and that invariably leads to a mild "bolt in" ( needs to alterations to the valve train) cam

on to your question:
...it's not so much a matter of "flow" or "backpressure", but deliberate tuning of the exhaust tract, flow & velocity

and also keeping the gasses heading in the correct direction, and controlling harmonic pulses. which can push past open valves on the intake stroke and push the intake charge back out the air cleaner ( 'reversion")

there is a lot of science/physics to this

It is possible to get acceptable results by drilling or punching holes, and alot of guys do this as a 1st step as the stock mufflers are likely to get tossed anyway.

--- it would be pretty difficult to get horrible results short of making them into straight pipes too, so that's the good news

supertrapps' engineers have written that in an "open can" exhaust with no packing behind the baffle, exhaust gasses can eddy and change direction resulting in a lower net flow rate through the exhaust, dependent on rpms

But I have not had the magic luck with the drill and I've had mufflers ready to go on bikes when I get them.

Most riders look for sound ( which is subjective both the to rider and the observer) and performance is secondary

I look for mild performance gain available through free-er flow on the ins and outs, with complementary tuning. I keep the mechanicals near stock for reliability and mpg

while i do enjoy a louder than stock exhaust note, all day touring shows that loud pipes get boring and fatiguing, and i like being able to hear the radio


GR and I use supertrapp type pipes which have a disc system to tune the pipe to the motor and the rpm range of interest**

the exhaust note is also controlled by this tuning.

These mufflers have the potential to get high ranking for power while controlling sound.

while the supertrapps are spendy, the made for screaming eagle nightstick is very similar and can be retuned with a disc and endcap swap to be very similar to the supertrapp supermegs ( which is what I am doing on my latest bike, I bought 2 used for under $200)


Mike


* My 95 FLHTC went over 80K and was running like a top when I sold last year ( got a new bagger). My ex-CHP 88 FXRP went over 70,000 hard miles and was re-ringed. This bike I did the CV carb swap and before after dyno runs showed 3 HP gain, before tuning- just need spigot adapter, new cables and spacers for the air cleaner mount at the heads


**in town I tune for torque, as i will be starting from a dead-stop or trying to zip through traffic. I keep these same setting for canyons.

when touring I re-tune the pipe for HP ( move the power up in the rpm range) as the motor will be turning 3000+ rpms all day long, with just a couple of gas stops

 

I have the fullsac true duals on my '89, with Cycle Shack slip-ons. I made this conversion over four years ago, so I've been living with it for a while. While there may be some slight performance loss there, it is more than made up for with other improvements that have been made to the motor, carb and ignition. And it sounds great.

 

RaSH,
If you are interested in one of the top exhausts for A HD V-Twin go to RB Racings site. Most of the pipes at bonneville and other top speed events that hold records are his pipes. The guy is a spectacular engineer and each pipe is built for your bike. There is a waiting period, they are a little pricey, and don't call and try to talk to him for hours and argue as he will hang up on you. That's why I say go to his site, read and you will get an education. I have his pipes on both of favorite bikes and have one for the new custom I am building. Hope this helps.