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Sportster Motorcycle Air intake, Carburetor, EFI, Fuel, and Exhaust Problems, advice and/or how tos for Sporster and Buell motorcycle carburators, Electronic Fuel Injection (EFI), Air Intake, Fuel and Exhaust.

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  #1  
Old 22nd April 2018
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Default Stage 1 results

16 Roadster, DK outlaw intake, SE slip-ons, powervision tune. 75.6 torque, 73 hp. Seems rather typical. But then I see Hammer Performance has a stock 1200 with intake, tune, cycle shack slip-ons getting 84 hp?! This is shown in the cams section to compare to the jackhammer 570 making 5 more. CS really going to flow that much better than SE? More tedious tuning.

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Old 22nd April 2018
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How are the baffles?
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Old 22nd April 2018
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Untouched. Didn't really want to go loud and over the years SE slip ons have faired well in pipe comparisions I have seen, particularly for torque.
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Old 22nd April 2018
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That motor's not happy at all. Notice how choppy the sheet is. Although I can't read the "Smoothing" number - is it set to 5? Sometimes guys turn it down in a deliberate attempt to make the chart choppy, to get fractionally higher numbers. So if he turned it down, that could explain it.

The Correction is STD, which is another thing some shops do to make the numbers look a little better. Although as you get into higher CF's, for example at high elevations, it'll actually turn around on you and SAE will show bigger numbers. But at 1.04, STD will look better, probably by 1-2hp.

In any event, yes, it's a low result. I've seen lots of stage 1 EFI 1200's that were north of 80, not just on our dyno either. Even the carb'ed stage 1 1200's can approach 80. And there are lots of potential reasons why yours is so low.

The number one thing that jumps out at me when I look at that sheet is that it's run number 001. That suggests that the bike wasn't properly worked and tuned, it was rolled on the dyno and one pull done.

No bike is going to show a good number that way, especially an EFI bike. Anytime you do a key-off/on cycle and start the motor, it goes through a warm-up cycle that includes throwing a lot of timing at it. It also throws fuel at it, although that can be disabled in the tune. I might be revealing a little too much here, but understanding what the ECM is doing is pretty important to getting a big number out of the bike. I always set up the PV to monitor both AFR (requires the wideband kit) and spark advance, both cylinders, and I keep an eye on both during the pulls.

Even more important though is temperature management, so the engine temp is also on the display. On a carb'ed bike I have a laser thermometer gun handy and keep an eye on the temp right next to the spark plugs. It' not about just having the motor at the right temp, either, but having it be at the right temp after being at a higher temp. It's called the "heat soak" effect and knowing how to manage it is not only how you get a big number, it's also how you get enough repeatability to be able to make changes and accurately evaluate small differences in the result. If you don't have repeatability, you can't tune, because you'll get fooled and end up out in the weeds.

Anyway, you don't get anywhere near where you need to be in one pull. The results change on their own, with no changes on your part, through multiple sets of pulls until you've built heat into the motor and the oils and you're playing the heat soak effect, and that can take a dozen pulls or even more, depending on the temp where you start out. When starting with an even moderately cold bike, I'll run it up into top gear and just let it cruise for awhile, to help get some heat into the motor and the oils.

Again, I'm probably revealing too much. But I can tell you this for sure. The numbers we show don't come from rolling a bike on a dyno and doing one pull. And none of these big result numbers from us or anyone else come from doing it that way.

There are other factors at work here too, for example it sounds like you used a Dynojet canned pull. I think that's just a disaster when it comes to tuning these bikes. That's just my opinion, however, it's based in fighting a lot of issues. Do this some time. Open your bike's original tune in WinPV, then hit "Load Compare" and load up a Dynojet canned tune and look at all the differences.

Quote:
Originally Posted by 09Nightsterrider View Post
over the years SE slip ons have faired well in pipe comparisions I have seen, particularly for torque.
HD has offered a bunch of different slip-ons over the years, some good and some not so good. I don't think they even sell anything anymore except EPA legal stuff, do they? I don't know, I don't pay that much attention to their stuff.

But anyway, you have to keep in mind that power is torque times rpm, literally that's the formula (divided by 5252, but that's a nit, think of it as torque times rpm). So the way you make big power is to make torque and rpm at the same time. Or in other words, place the torque over on the right hand side of the dyno sheet. Presto, the power number goes up.

If your spark advance and afr are correct, then torque is really a function of cylinder fill. Therefore the shape of the torque curve is a map of your cylinder fill.

So look at the shape of your torque curve to understand what the motor is doing. Yours comes up pretty good, peaks at about 4000, holds pretty well to 4500 or so, and then rolls over and dies on top. The motor is running out of breath on the top side.

So what's causing that? Could be anything between the air cleaner inlet and the exhaust outlet. I'll tell you something to look for, I see this on probably half the bikes that are brought to me for dyno tuning. Make sure your throttle plate is reaching it's stop when the throttle grip is twisted as far as it can go. I've literally found more than 5hp for guys by adjusting their throttle cables, although typically it's more like 1-2hp. It's a common mistake though.

The way yours pulls pretty decently and then dies on top, though, generally means restriction. One very simple test you can perform while it's on the dyno is to just pull the air cleaner off, to verify that's not it. I don't have any reason to believe that's your issue, don't get me wrong. Although I've never tested that particular air cleaner, I'd be astonished if it choked a motor at 73hp. But I'm of the school that everything should be verified, take nothing for granted.

When you see an issue that's only occurring on top like this, lots of times that indicates pumping losses. You see this for example when you stick baffles into drag pipes. Drag pipes have so little volume that baffling them tends to choke them down and the top end power suffers.

But you also have to watch for poor diffusion. Lots of pipes will push back, then pull, then push back again, as you sweep through the rpm range. There's a long technical explanation behind why they do that, but I won't bore you right now. Bottom line, when you see a torque curve that has peaks and valleys, you know that's what's going on. Ideally you'd like the torque curve flat, indicating nice consistent cylinder fill over the rpm range. A flat torque curve will generate a straight diagonal power curve, up and to the right.

Which kind of gets back to your torque comment. Lots of times a torque curve with peaks and valleys will have a higher peak torque figure than a flat torque curve. I submit to you that the shape of the torque curve is really much more important than the peak number. Flatter is better. Broad parabolic shapes are good too. Peaks and valleys are bad.
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Old 22nd April 2018
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Thanks for your detailed response! Smoothing set at 5. I do assume the SEs are restrictive, they are rather quiet and epa compliant. It is a canned tune from dynojet. I have 1 from fuelmoto, I have been trying to compare the two for performance and mpg. So many folks say they still get 48+ mpg with a stage 1 and tune while I can't get more than 43 on rural highway driving.Local dealer was offering a $99 tuning special. Figured that was cheap enough for a pull alone. Tech stated that he was not familiar with powervision, which surprised me, and that he was surprised how well it ran as most he sees are way off . He stated that he did not change anything as it was running well and there was little to gain. An effect of the price charged perhaps. When you say that the engine is not happy. Are saying in is in danger of harming itself, or just that is not reaching g it's potential for performance? Thanks
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