Performance and quieter pipes

[Chris S]

Have I missed something somewhere? I was always under the impression that if I wanted to improve the performance of my Harley I needed louder (less restrictive) exhausts. I have ridden my 2001 Heritage for years on a stage 1 with Screamin' Eagle slip ons which were there when I got it. It was a bit loud but not uncomfortably so. I recently added a cam swap and the noise is too much now. (Love the performance form the Andrews 37 cams!)
But can I keep the performance if I put some stock pipes on? I have no problem losing a few horses, its not a race bike. All I ever wanted was to get some power when I opened the throttle rather than lots of noise and slight acceleration.
Apologies if this is a stupid question but I have no interest in making lots of noise. I just want to enjoy my bike and not piss people off. There are enough idiots on the road with no consideration for others.

I originally posted this query in a quiet baffles post, it was suggested I start a new post on this topic. Having said the above I am not keen on the look of Supertrapp exhausts on a Heritage . Manufacturers quiet baffles do not seem to be much of a solution if I read the post about baffles right. But surely a stock restrictive exhaust will stifle any performance mods?

 

[Fast Lane]

Re: Performance and quieter pipes

But can I keep the performance if I put some stock pipes on?

No.

But surely a stock restrictive exhaust will stifle any performance mods?

Yes it will.

I'm asked for exhaust recommendations more than anything else and my answer is always the same - it's impossible to recommend any particular system because there are many factors to consider and everybody prioritises those factors differently. For the vast majority of riders the sound is at the top of their list. This is why the exhaust is always the first component to be changed on a new bike. We all love that sound. With that in mind, what I consider to sound great will not appeal to everybody. The sound that you hear from the exhaust system is the sound of the exhaust gas leaving the cylinder head. Exhaust system design encompasses the length and diameter of the headers, the bend radius of the headers, any steps in diameter and cross sectional area, whether two seperate pipes into one collector then a muffler, or there are two seperate pipes with no connection to each other and the differing lengths of each one. The sound of the exhaust gas leaving the port is determined by how much pressure is still contained within the combustion chamber when the exhaust valve opens. An early opening cam will have a sharp crack to it, a later opening cam a dull thud. I once imported a D & D Fatcat from the states which cost me ?800 and it worked very well in performance terms but I hated the sound. So much that I put it on Ebay and it sold a month later for ?150 - I hated it that much. Other folks love performance and every other aspect of the exhaust is irrelevent. Others have to look right no matter what it sounds like or how well it performs. The one system that I see consistenly high numbers from is the Super Trapp Super Meg but as you've already said you don't like the looks of it then that's no good to you. I've just fitted one to my 114" Heritage and I like the look. The sound is too quiet for me as I'm used to a Thunderheader but I can live with it for the performance. To get back to your question - yes a stock exhaust will restrict any performance modifications. The exhaust is a major player in the big picture. I've seen both torque and horsepower increase and decrease dramatically on the dyno due to even small exhaust changes such as baffle modifications. The exhaust can either make or break the build. A recent change on a 1275 Sportster from a RSD Tracker to another system brought a 19 HP gain. As you say the 'quiet baffles' that some manufacturers sell don't do much at all. Also be aware that that vast majority of commonly available exhaust systems are designed for stock engines. Once you go down the performance route the flow characteristics become more influential on the final TQ and HP curves. What's the rest of your build? If you have the TW37 cams in an otherwise stock 88" engine then you're nowhere near the potential of those cams ...

 

[Fostlongstrider]

Re: Performance and quieter pipes

I have V & H pipes on my 2006 Heritage and they appear to have balance pipes between the two separate main exhaust pipes. At the last MOT there was a note of "Loud pipes" but that was the first time that had been mentioned on an MOT and I have all the MOT certificates.
I get what I call good acceleration when I wind the throttle on and I don't think the exhaust is too loud.
I certainly get more than "slight acceleration" and not a lot of noise!!

 

[Chris S]

Re: Performance and quieter pipes

No.



Yes it will.

I'm asked for exhaust recommendations more than anything else and my answer is always the same - it's impossible to recommend any particular system because there are many factors to consider and everybody prioritises those factors differently. . . . . vast majority of commonly available exhaust systems are designed for stock engines. Once you go down the performance route the flow characteristics become more influential on the final TQ and HP curves. What's the rest of your build? If you have the TW37 cams in an otherwise stock 88" engine then you're nowhere near the potential of those cams ...

Thanks for your reply Fast Lane - the motor is a stock 2001 88B with Ness big sucker air cleaner and Revtech DFO fueller. Exhaust is the Screamin Eagle slip ons (without the crossover pipe, I have both types but found in the past that accelration was better on the solos). At 26K I had a look at the cam tensioners and decideed they had to be done. I was always disappointed with higher end performance so seemed obvious to do the cam at the same time and Andrews recommended the 37B cam. The descriptions online seemed to fit with my requirements.
Done the deed and Wow! that woke the f***er up. I am sure there is more to get out of the cam, as yuo say, but for now I want to keep it to 1450cc. There are less and less twin cams going to be around and the 88 is going to get rarer all the time. I would rather get what I can out of it and leave it there. Ported heads may be worth doing in the future. At the moment the injectors are away for cleaning as the cam swap highlighted a bit of a misfire at lower revs.
Clearly the exhaust has to be right too hence the post. The fact that anyone can buy an exhaust and not find it suits their needs makes this post useful for sharing more experience on this topic.
It is interesting that Supertrapp use the 2 into 1 set up. Does the crossover pipe on stock exhausts have 'performance' benefits? Because that is not my experience (limited though that is!!!)

 

[seanofmacc]

Re: Performance and quieter pipes

Its always going to be a balance of sound, looks and performance.
I no doubt lost performance by keeping with my 2000 correct SE silencers after a performance engine build but was willing to live with it because i wanted it to look like it should have 20 years ago. To be honest it goes like the feckin clappers and sounds glorious. Is the extra few HP worth it and the shit loads of pounds to upgrade to a "proper" exhaust system? Nah not a chance
In all honesty you are never going to be on the edge of your performance curve anyway

 

[Fast Lane]

Re: Performance and quieter pipes

the motor is a stock 2001 88B with Ness big sucker air cleaner and Revtech DFO fueller. Exhaust is the Screamin Eagle slip ons

I am sure there is more to get out of the cam, as you say

The 37B grind is the wrong cam in a stock 88" engine. You have only 8.5:1 static compression ratio which results in less than 160 psi cranking pressure. You need about 9.8:1 for that cam profile to become efficient. In a stock 88 the Andrews 21 is the one to go for. The Andrews 48 is better than the 21 but you need a valve spring change to run it with the early cylinder heads. If you really want to stay at 88" displacement and keep the 37 cams then I'd suggest a pair of HD part number 22864-00 domed pistons and a pair of 3.975" x 0.040" head gaskets which would get you right at 9.76:1. Or a better solution is to go to 95" as most others do and then that opens the door to much more performance potential.

There are less and less twin cams going to be around and the 88 is going to get rarer all the time

Actually the opposite is true - all of the dealerships and Ebay are full of Twin Cams as many people have traded them in or are selling them so they can buy the newer M8 engined bikes. Now is a good time to buy a Twin Cam.

Ported heads may be worth doing in the future

There's not much value in ported heads in an 88" street application. The bore diameter is too small to benefit from a bigger intake valve unless you rate horsepower over torque and ride above 5200 RPM regularly. The exhaust port is terrible on the 99-05 castings so that can be improved and the chamber can be cut to increase compression but that's about it.

the cam swap highlighted a bit of a misfire at lower revs

The misfire is the result of the fuel table being a mile out in the Revtech fueller. They're very dated nowadays and were next to useless when they came out. A decent tuning device such as a Power Vision and an appropriate flash or dyno tune will make it feel like a different bike.

It is interesting that Supertrapp use the 2 into 1 set up

Not just SuperTrapp but all performance V-twin exhaust designers utilise the two into one design as it's far superior to anything else in terms of both torque and horsepower development. Have a look at D & D, Rinehart Racing, RB Racing, Dragos Dragula, Rush Wrath, Bassani Road Rage, Burns Stainless NhB systems etc - they're all two into ones.

Does the crossover pipe on stock exhausts have 'performance' benefits?

Not really. It might in a different application but all of the other components in a stock engine such as the cylinder heads, cams and throttle body have no performance characteristics anyway. You could fit the most efficient exhaust system there is onto a stock engine and it wouldn't make any difference as there's not enough gas being allowed to reach it due to restrictions in place earlier on in the combustion process ...

 

[David Barnby]

Re: Performance and quieter pipes

No.



Yes it will.

I'm asked for exhaust recommendations more than anything else and my answer is always the same - it's impossible to recommend any particular system because there are many factors to consider and everybody prioritises those factors differently. For the vast majority of riders the sound is at the top of their list. This is why the exhaust is always the first component to be changed on a new bike. We all love that sound. With that in mind, what I consider to sound great will not appeal to everybody. The sound that you hear from the exhaust system is the sound of the exhaust gas leaving the cylinder head. Exhaust system design encompasses the length and diameter of the headers, the bend radius of the headers, any steps in diameter and cross sectional area, whether two seperate pipes into one collector then a muffler, or there are two seperate pipes with no connection to each other and the differing lengths of each one. The sound of the exhaust gas leaving the port is determined by how much pressure is still contained within the combustion chamber when the exhaust valve opens. An early opening cam will have a sharp crack to it, a later opening cam a dull thud. I once imported a D & D Fatcat from the states which cost me ?800 and it worked very well in performance terms but I hated the sound. So much that I put it on Ebay and it sold a month later for ?150 - I hated it that much. Other folks love performance and every other aspect of the exhaust is irrelevent. Others have to look right no matter what it sounds like or how well it performs. The one system that I see consistenly high numbers from is the Super Trapp Super Meg but as you've already said you don't like the looks of it then that's no good to you. I've just fitted one to my 114" Heritage and I like the look. The sound is too quiet for me as I'm used to a Thunderheader but I can live with it for the performance. To get back to your question - yes a stock exhaust will restrict any performance modifications. The exhaust is a major player in the big picture. I've seen both torque and horsepower increase and decrease dramatically on the dyno due to even small exhaust changes such as baffle modifications. The exhaust can either make or break the build. A recent change on a 1275 Sportster from a RSD Tracker to another system brought a 19 HP gain. As you say the 'quiet baffles' that some manufacturers sell don't do much at all. Also be aware that that vast majority of commonly available exhaust systems are designed for stock engines. Once you go down the performance route the flow characteristics become more influential on the final TQ and HP curves. What's the rest of your build? If you have the TW37 cams in an otherwise stock 88" engine then you're nowhere near the potential of those cams ...

Have discussed with Alex many times on this topic. For a Softail there are few performance options beyond 2:1 and he lists all / most of those. The Supertrapp is the best compromise (must send you a few extra discs Alex) with its proven performance ability balanced by not having the ?best sound?

on the touring bikes and slips-ons I think the OEM silencers without cats are as good as anything aftermarket. Just look inside, they have the same wrapped baffle set up with a straight through path. Aftermarket versions do away with the wrap and increase the baffle diameter to increase noise. There is some engineering in the Reinhart (And a few others) baffles with spiralled lipped apertures instead of holes in the baffles which provide return waves to the gas flow but without stepped headers and the Louvre applied at the header power difference is likely to be marginal.

My Fastlane engined touring bike surprised everyone on the Dyno (including the CAM maker) with its stock silencers mounted on the V&H Power Dual header system. Even if most of the baffle wrap got blasted out in the process. At NOS 80 quid a pair is no great loss.

An interesting test is to use a power vision autotune. I switched the silencers to the CVO silencers which are chambered, not baffled. Looking at the Autotune VE adjustments to achieve the AFR map I could see if there was more or less flow. The buggers are far quieter and the VEs indicated more fuel had to be added to match the increased ?A? part of the AFR ratio. Would have to put it back on the Dyno for performance differences but that will obviously have to wait.

V&H guys told me when I called them that their market is looks and sound improvers not performance. True performance (as measured on a Dyno) searchers form a small part of the market the guy said. You need to understand that most customers have no clue and report on forums how life got so much better after they dropped a grand on their new shiny set up.

My beautiful V&H Propipe 2:1 fitted to my Fastlane engined Softail got changed soon after to a Supertrapp which has far less attractive bends and not a sexy sound but with its stepped headers, wrapped baffles and disc based tuning ability represent a no brainer when trying to do things right.

 

[Halal Tim]

Re: Performance and quieter pipes

Have to agree with you on the touring set up.
I run a 103 street glide. Alex did a street tune on the heads, and a set of andrews tw57cams. K&N filer in stock housing, with breather bypass hose. I am using a stock header, modified by fullsac USA. Basically they cut the cat section out, and replace it with an X crossover design. A decat stock header works nearly as good. (I got the fullsac cheap, on ebay).
I use cvo end cans, with baffles from a set of kuryakin krusher silencers. Of you could use the fullsac baffles.
This set up was recommended to me by Boz at powerglides.
Like Alex, he knows a bit about what works, and what is a waste of money.
Looks stock to the naked eye, and has all the relevant oem numbers stamped in, incase plod get a tad interested.

Makes 107.5 bhp at the wheel, and 114.6 torque.
Pulls like a train, and is not loud. For real world touring, thats a good set up.

 

[Buck]

Re: Performance and quieter pipes

Cams are generally the answer, much more so than increasing cubic inches. If you are going to do cam work though it is a good idea to look at a better camplate as well to sort out your oil pressure and prevent sumping.

 

[Fast Lane]

Re: Performance and quieter pipes

Cams are generally the answer, much more so than increasing cubic inches.

Wrong way round - displacement is the foundation of any performance build and has a greater influence than anything else providing the heads can handle the additional air flow. The more displacement you have the more compression is available. The cam timing events combined with the air flow characteristics of the heads move the peak volumetric efficency to a particular area of the RPM range. These two factors dictate where the VE peaks and the exhaust system controls the shape of the curves as seen on a dyno chart. The cam choice has to be matched to the available compression which is dependent on displacement.

If you are going to do cam work though it is a good idea to look at a better camplate as well to sort out your oil pressure and prevent sumping.

Not really - the cam plate just supports the cams and the oil pump. Wet sumping occurs when the oil entering the crankcase is more than is being taken out. This depends on the efficiency of the scavenge section of the pump. The only component within the Twin Cam engine that's dependent on pressure is the piston cooling jets. As long as there's 12 psi to open these then any higher pressure is not required. I've had a few customers with 99-06 stock oil pumps who have been unpleasantly surprised when I've fitted oil pressure gauges at their request and they see barely above zero psi at idle. Flow rate is much more important than pressure in these engines ...

 

[Buck]

Re: Performance and quieter pipes

Really? I was told by a tuner in the U.S. that cams were a better choice than going with more cubes, although I think we were talking about improving ridability so it may be apples and oranges, he also said that a camplate upgrade was sensible for pre 2006 machines and I was sure it was to do with sumping. However I will bow to your superior knowledge, you do it for a living after all.

 

[Fast Lane]

Re: Performance and quieter pipes

I was told by a tuner in the U.S. that cams were a better choice than going with more cubes, although I think we were talking about improving ridability so it may be apples and oranges

My understanding is that 'ridability' is all about throttle response at lower RPM. Throttle response is governed by fuel delivery and ignition timing. Poor response/control at low speed usually indicates that the tune is a mile off (which all downloaded tunes are) or in a carbed bike it's not set up correctly. A cam change to the wrong profile will often make low end throttle control more difficult. Try a long duration, late intake closing, high lift cam in a stock engine as an example. The cams or more cubes discussion is very situation dependent. In my position I'm regularly asked to come up with a performance bump for customers with a stock 88" or 96" engine and a limited budget. In that case a displacement increase wins every time. The MoCo have a warranty system in place that they have to protect at all costs - they will try anything to get out of a warranty claim. With that in mind all of their stock production engines are very tame in terms of compression. This is to minimise any stress on the major components and avoid anything that will involve a claim. The performance of a stock engine is mediocre at best. Once you've ridden a performance engine a stock engine will send you to sleep. You crack the throttle open and nothing happens - but the engine will outlast the warranty which is good for business. In value for money terms a displacement increase will yield more torque and horsepower in a stock engine than a cam change. The stock cams are low lift, low duration and are just good enough for the engine to run but they can handle more compression. If you changed the cams only in a stock engine then you'll find that in order to increase the corrected compression (which controls the amount of pressure exerted on the piston crown during the combustion stroke) the cam choice is very limited. Another advantage of bumping displacement is that further down the line if you want to change cams there are many more choices available to match the increased compression. A disadvantage of changing cams only in an otherwise stock engine is that again if later on if you decide to go with a displacement increase then you'll also have to change the cams you fitted earlier. Cams chosen to maximise performance in a stock engine won't work with more compression. I mentioned situation dependent earlier on. In some cases a cam change is the right choice - say for example you have a 103" stock engine. The cams fitted to the 103's are exactly the same as those fitted to the 96" engine. In this case the stock 96 has about 9:1 compression and the 103 about 9.5:1 - both of which require different cams to become effective. The stock 103 would benefit from a cam change.

he also said that a camplate upgrade was sensible for pre 2006 machines and I was sure it was to do with sumping

There must have been some confusion here. The function of the cam plate is just to support the cams and oil pump and direct the flow of oil to and from the pump. The only time I change the cam plate is if the cam drive system is being changed from chain to gears. In that case I prefer to use Feuling plates and pumps as the manufacturing tolerances are much finer. These finer tolerances are beneficial to ensure correct gear lash but in the stock chain drive system there is that much slop that these dimensions are not that critical. You might as well stay with the stock plate if you're running chain driven cams. The early oil pumps do scavenge less and flow less than the later revisions but saying that I've never personally come across any oil starvation issues in the early motors. Sumping is possible - the early pumps are pretty weak. There is an o-ring where the pump joins the plate in the early motors. I think that some of the sumping reports have come from people who didn't seat the o-ring properly allowing oil to bypass and fill the crankcase.

 

[Buck]

Re: Performance and quieter pipes

I?m quite happy with my 96ci , I have the screaming eagle air filter and Rinehart true duals plus I have a Power Vision, not convinced about the exhaust however and am thinking of going with S&S duals that moves the rear pipe under the bike and gives equal length down pipes for both cylinders. I did make changes to something I know a lot about, suspension, fit single rate stiffer springs up front and slightly modified Ricor Intiminators. Despite people saying the rubber mounts on the swing arm causes the shimmy, it is really down to the front end being too soft. I went through the Dragon in North Carolina with this setup and surprised the hell out of a few sports bike riders.