Dyno Case Studies

Twin Cam 107" conversion with stock heads

Increasing the capacity of any Harley-Davidson engine has always been a popular way of getting more power, and the Twin Cam is no exception. It is also the case that ported cylinder heads, in particular our Head Quarters heads, adds to the power gain. However, not everyone has the budget available for these higher performance builds, so we have developed a more economical performance upgrade that gets a lot closer to these true high performance builds and easily out performs the more common 103 conversions. The ethos behind this Powerglides exclusive package is to keep the parts and labour content to the minimum without cutting corners, compromising reliability, or sacrificing low speed driveability for the sake of a high peak horsepower number. We offer this as a complete "turn key" package including a dyno tune specific to the bike.

Twin Cam 107 conversion with stock heads

A very effective "Stage 1"

From a performance aspect our first choice for an exhaust system is invariably the 2 into 1 Supermeg from Supertrapp. They always produce an excellent torque and horsepower gain, but most importantly they give exceptional driveability and a very strong mid range pull.

They are also very easy to tune with, either with carburettors or fuel injection. Harley engines love this pipe, and since they also work so well on the bigger performance builds, they provide an upgrade path for future work such as camshaft changes, headwork, and capacity increases.

Being relatively quiet they don't cause issues at MOT time either, particularly as they can be easily adjusted for noise levels.

Dyno graph

This bike is one of the new 2010 Dyna Wideglides which we tuned on the dyno with our Direct Link Flash Tuner software, and the two graphs show the "before" as stock, and the "after" with the Supermeg, SE Heavy Breather air cleaner, and the tune. We're not far off 100 ft/lb of torque here, without going inside the engine, and it looks good too.

FXWG Supermeg Heavy Breather

Difference in jet kits

This low mileage 1998 1200 Sportster originally came in for a service, where we noticed when road testing, how unresponsive it felt, particularly during a moderate roll on through traffic. It also stumbled, typical of the over fueling we see when the OEM CV carb is incorrectly modified.

This bike had the normal dealer fitted "stage 1" kit from this era; SE slip on mufflers, SE air cleaner, and a commonly used jet kit. These jet kits, which also involve enlarging the signal port hole in the CV slide and the use of a lighter spring, have an adverse affect on the way this carburretor is designed to work.

So we put the carburettor back to standard by installing a new, unmodified, slide, stock spring, and stock emulsion tube. To this we added a Head Quarters jet kit which, importantly, doesn't interfere with the perfectly acceptable original design.

This graph shows the incorrectly tuned bike versus the bike retuned here. Whilst this in itself shows a useful power gain, remember that this is achieved using far less fuel, and that throttle response, part throttle driveability, and overall fuel consumption are also greatly improved.

When this bike subsequently returned for it's next service it was refreshing not having the oil smelling of petrol!

Dyno graph 1

EFI "canned maps" rarely work

This bike, a 2003 Fuel Injected Heritage Softail, was bought to us by another shop. The engine was a standard 88" with SE slip on mufflers, SE air cleaner, and the recommended Harley cartridge download (canned map) that the dealers used to do with the Scanalyzer. This bike had very low mileage as the owner only used it on sunny days and enjoyed pottering around the country lanes, with no interest in how much power it made. However, his enjoyment was spoilt by the fact that the bike was awful to ride slowly. The reality is that a "map" developed on one particular bike will rarely work as well on another. There are too many production line variables, not just in the engine components, but in associated parts such as fuel injector flow rates and fuel pressures.

By running the bike on our dyno at different RPMs, throttle positions and engine loads, we could see by monitoring the Direct Link Flash Tuner data logs and the information from the lambda sensors for each cylinder, that the Air Fuel Ratio (AFR) was way too lean on one cylinder at small throttle openings. Additionally the AFR was excessively rich on Wide Open Throttle (WOT).

By correctly remapping the Harley Electronic Control Module (ECM), using the Direct Link Flash Tuner software we were able to completely rectify the driveability issues and also give a useful gain in both torque and horsepower.

Dyno graph 2

Tuning by road testing v dyno tuning

This is a 2001 Dyna Sport that we converted to 100" by boring the crankcases and fitting 4" bore cylinders and pistons, Head Quarters 0039 cams and ported heads. The owner, who is experienced with Harleys, fitted an HSR 45 Mikuni, Crane ignition, a Supertrapp Supermeg with 24 discs, and tuned it by extensive road testing.

The bike ran well, but came back here to see what we could gain with the Dyno

We ended up with 18 discs on the Supertrapp, a leaner needle, larger main jet and a different ignition setting. Even for the experienced, setting up a Harley with this amount of power is both awkward and time consuming to do by road testing. Every change we made had an impact on other settings, and being able to do this by measuring the results on the Dyno is quicker, safer, more accurate, and ultimately yields better results.

Dyno graph 3

Chalk and cheese

This should be a real eye opener for those who have been disappointed with their previous performance upgrades.

This bike, a 2008 Softail Nightrain, already had one of the common SE103 kits fitted with the 255 cams, V&H slip on mufflers and a SE air cleaner. Whilst these cams build the torque very quickly they also rapidly run out of steam above 3000rpm, just as we need to get going.

Rather disappointed with the lack of mid range power, the owner came to us for a solution. For an already lightened wallet, we suggested our 107" kit using Head Quarters parts. This is the biggest we can go without pulling the motor for case boring, bigger cylinders, or a longer stroke crank, which obviously adds substantially to the cost. In fact, the labour content of this kit installation is no different to the one he already had fitted. Another advantage is that we can safely bore the stock cylinders to get this capacity increase, and the stock throttle body and injectors can also be reused.

We fitted a better exhaust, a V&H Blue Proof Pro Pipe (we couldn't find a black Supertrapp at the time) and reused the SE air cleaner, although there are better ones out there. We then tuned the bike on our Dyno using Direct Link Flash Tuner.

When looking at this chart remember that the lower (black) curves are from this same bike as it came in as a "performance" 103. With our 107 kit the power is all in by 5800rpm, which is still below the safety limit on the Twin Cam B motors. There's a 30hp increase here! But the best thing is that unique Head Quarters torque curve, this bike just pulls and pulls, and there are no low speed driveability issues either. Priceless. Yeah, chalk and cheese.

Dyno graph 4

Dyno tuning Vs aftermarket "fueler"

Harley fuel injection is very sophisticated in the way that it works, and tuning even a mild performance build, requires the level of technology that we have invested in.

Because of this expensive investment in both equipment and experience, most of the market is trying to convince itself that simple plug in fueling devices can deal with it. That is most definitely not our view (we won't tune with them), and this bike illustrates why, very well.

This Harley is a 2007 Dyna Streetbob that the owner had very competently upgraded himself to a 103, with S&S cams, Supertrapp Supermeg and a Ness Big Sucker air cleaner. Whilst we prefer the Head Quarters cams in our own work, these S&S 510 profiles are a good choice, and certainly better than most of the offerings from other suppliers. The exhaust and air cleaner are also ones that we commonly use. So the combination of parts is a good one.

Unfortunately the "brand X" plug in fueler was nowhere near up to the task, so the bike came here to be tuned our way. The difference in the torque curve is astounding, and remember that this "before and after" is purely the result of a good tune, compared with a bad one. No parts were changed (other than throwing the fueler in the bin). It was all done with the dyno, years of Harley tuning experience, the Direct Link Flash Tuner software, and the computer. Welcome to the 21st century.

Dyno tuning Vs aftermarket fueler

Bolt in camshafts for the 2011 FLs

The 2011 FL models, which are the Roadkings and Electraglides, now have a 103" engine as standard, as well as a new software level in the ECM. We have developed, on our Superflow dyno, a parts and tuning combination that maximises torque at low rpm, gives a 33% horsepower increase, and dramatically improves throttle response!

Other than installation of the Head Quarters camshafts and new Torrington cam bearings, no other engine disassembly is required, which keeps the workshop labour costs under control. Exhaust system is our favourite Supertrapp Supermeg, so the bike is not excessively noisy either. The DBW (Drive By Wire) throttle bodies, used on all FL models since 2008, have a low rpm throttle lag programed into the ECM from the factory. As part of our Direct Link Flash Tuner dyno tuning procedure, we can also remove most of this, which improves drivability when trickling through heavy traffic. This is a very cost effective performance upgrade for those who wish to go further than a "stage 1", but would prefer not to have the additional expense of major engine work.

The 2011 FL models, which are the Roadkings and Electraglides, now have a 103 engine as standard, as well as a new software level in the ECM

Twin Cam 88 95" Torque Monster conversion with stock heads

The Twin Cam 88 to 95 conversion has always been popular. However, most of these more common conversions do not give a high torque figure. By utilising a wise choice of components that interact well together, coupled with some assembly "tweaks" and our tuning experience, we have developed a kit that hits 100ft/lb at just 2750rpm. There is no cylinder head port work required with this conversion, and the stock valve springs are retained. Neither is there any need to spend money on an expensive carburetor, as the 40mm CV is also used.

The key components here are the Supertrapp Supermeg and the Head Quarters 0034 bolt in cams. We use Head Quarters forged pistons with a 10-1 compression ratio, and machine the existing cylinders. A Head Quarters jet kit and programable ignition allows us to deal with the tuning correctly. For the Delphi EFI models, the stock throttle body and injectors are kept, and we tune on the Dyno with our Direct Link Flash Tuner software. needless to say, the throttle response is exhilarating.

The Twin Cam 88 to 95 conversion with stock heads

Twin Cam 88 95" Torque Monster conversion with ported cylinder heads

For those who desire serious top end performance AND a quick torque build, one of our conversions with Head Quarters ported cylinder heads is the way to go. Most other suppliers' conversions build big horsepower at the expense of low down torque. Not with these conversions, we have it all. Very docile and driveable through traffic, a nice roll on, and the big horsepower for those who need it. We have these available in different compression and camshaft configurations to suit different models and riding styles. We recommend retaining the CV 40 carb, although this bike has the HSR42 fitted. Again, the Supermeg is the prime choice This graph shows our Sport Touring build, HQ 10.5 compression forged pistons, HQ 575 cams, HQ lifters, adjustable pushrods, and programmable ignition. Bike is a 2003 Dyna.

Twin Cam 88 95

Harley-Davidson Screamin Eagle 120R

We are already working with this new engine, and although available ready built as a "crate" motor, there are a number of other components that must be upgraded. Engines of this type absolutely MUST be correctly tuned. We are already there with this, and we can perform both break in and tuning on our dyno utilising our Direct Link Flash Tuner tuning software which also allows us to run (and record) live dataloging as we tune. We cannot stress enough, how important the tuning is, on engines of this nature.

This is the B version that we installed in a 2010 Fatboy. Not for the faint hearted!

Harley-Davidson Screamin Eagle 120R on the dyno


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