Ok I'm a noob to Cycling with a better credit score than sense, but I love riding. When I got my 2010 Street Bob, I had a B&H Big Radius 2n2 put on and the Stealership said I had to put on the SE Ventilator AC. They also said since it was a Dyna it did not need a new Fuel Computer but just a download.

I hated the look of that oversized spam can. So, I changed it out for the SE Stage 1 and did a sick moded cover like Shockwave. The bike was skipping and bucking like a old beater before the AC switch and is now a touch worse. So now the two questions.

1. Is there a way to tell if they even did the download to start with?
2. Would switching from the SE Ventilator to the SE Stage 1 require a new download or even a new fuel computer?

Thanks in advance and this site is a double edge sword for sure. Great place for help and ideas, but I have seen about 20K stuff I would love to do to my bike now.

Go4Boy
2010 Street Bob Denim Black, slowly blacking out and going retro

 

If they're giving you a stage 1 download, that's technically designed for the stage 1 SE air filter, and SE slip-ons, and generally works "okay" on most things in that ball-park. It's still designed to be EPA friendly, and street legal in all states, so it's still a very lean tune, like stock. If any of the components you're using (and I think they are) allow more air-flow than than the SE street legal stage 1 stuff, you're going to be even leaner.

1. You're bike should run decently and cooler than if they hadn't done the flash, but you probably don't have the equipment to "know" for sure.

2. No. The stage 1 flash they gave you is the same less-than-ideal tune you'd go with.

You don't need a new "fuel computer", what you really need a tuner (a devise that plugs into, or piggybacks onto your ECM), and then to get your bike tuned.

 

I heard last Sunday from from local HD mechanic That 05 Dyna's and up all have a S.E.R.T and are all tuned to have AC OR Pipes [not both] replaced with high air flow components. The ECM will make the minor adjustments it needs to compensate for the mod. Pipes PLUS AC mods compound the "misadjustment" and would need a download or remapping. This is what I was told at the Stealership. I read a bunch of posts on it over the last couple of days but become more and more confused.

 

No. That's wrong. SERT stands for Screaming Eagle Race Tuner, it's a physical box that allows a PC to talk to the ECM and upload a new map.

He was right that the stock map can typically adjust for the minor change in air flow that comes from changing JUST pipes, or JUST intake. That also means you'll get basically no performance increase from them, it will just be as if the air is a little thicker.

Why are you confused? Your ECM has a map in it based on your engine, and the intake and exhaust system it's designed for. It regulates how much fuel is delivered for a given engine speed and throttle position so that you hit a desired air:fuel ratio for a given engine speed/throttle position. It's based on how much air it thinks can move through your engine, and how quickly. When you just change the exhaust or intake, you're not really increasing that much how much air can move through the system, since it's still clogged up at one end or the other, so your ECM's stock model is still in the ball-park. Once you change both, a significantly higher volume of air can move through your system, so you will need to deliver a significantly higher amount of fuel. If you have your stock map, there's no way your ECM can know this, since it's just delivering fuel based primarily on your throttle position and engine speed (except for the narrow range in the 07 and later models where the bike is in closed-loop an it has 02 sensors helping it out).

 

Herr Monk - I've got to say, that's a great response. From all the threads that I've read (which is why I don't need to post) that appears to be the best explanation...and not just right or wrong.

 

THANKS for the response and clearing that up Herr Monk!! To clarify: here is what the HD dude based his opinion (for my bike) 05dyna, V&H short-shots, SE high flow AC and S.E.R.T.... My first question to him "do I need a down-load if put a heavy breather on it?" he said "no" do you agree Herr Monk? Then he went into the whole spiel about other dynas and years.

 

This post is not very clear.

So you already have a SERT (a little black box that plugs into your ECM and your computer)? Maybe you have it and your dealer is holding onto it for you? (Some dealers like to do that, I like to keep control of my own stuff).

If so, has your bike been dynoed, or did they load a canned map via your SERT?

The "downloads" are "flashes" which are EFA friendly canned maps made to go with the "street legal" SE accessories, but they are "good enough" to use with similar pieces of hardwear.

If you have a SERT the best route would be to get your bike dynoed with your new piece of equipment and get a new custom map made. IF you have a SERT and can't spend that kind of money what I would do is go in search of a map, either online, or a canned map on the SERT software CD that is the same setup/nearly the same setup as you have. Them maybe pay for a baseline reading on the dyno to make sure your A/F ratios are in the ball-park.

If you don't have a SERT, I would recommend not going with a flash, and buying some kind of tuner (I like the SERT, but other brands are fine), and either getting a custom map made (dyno tune), or find a canned map online/through the software that's close to what your setup is.

In all likelyhood, if you dealer has a dyno, they've probably already made a map for someone with your new setup, or something almost like it. You could either ask if you can contact that person, and then ask them for a copy of their map, or see if the shop will sell it to you directly on the cheap (most won't).

 

I do have a SERT but I'm not sure if the bike has been Dynoed, I bought the bike from this dealer with the short shots and the SE hi flow AC. I want to make sure that when I put the SE heavy Breather on I gain and not lose performance.

 

I don't know what the airflow volume characteristics are on either filter. Is your engine stock 88? There's only so much air an engine of a particular size can take in without forced induction. The difference in flow characteristics for a stock engine likely means you won't be getting much more air in than you already are (like sticking a stage II airfilter, which is basically what you're doing, on an un-modified stock engine won't get more air in than a stage 1). I'd say that if your bike has been correctly tuned for your current pipes and intake, the difference in adding a slightly more open intake won't be that great. And from a safety point of view, you're probably fine. From a performance point of view, you need to figure out the differences in volume of air between the filters, but my guess is that even with a tune, you're not going to see much improvement. Again, a really open heavy breathing filter is over-kill for a stock engine that can only move so much air through it at a time. The biggest difference will likely be aesthetic.

 

Thanks for the advice Herr Monk, things make a lot more sense now.