I'm not ashamed totell you why I went that route ...

Because my dealer told me.

I had no idea i needed this **** if I wanted to upgrade my exhaust. Air in ... hot air out. That was my understanding of the whole mess. So I got what the dealer said I needed. ... A higher flow air filter and a download to go with the pipes. I still don't completely understand the difference b/w the "DOWNLOAD" and all these other options you guys are talking about. PCIII, SERT,.. what do the acronyms mean? How do they differ? What do they really do? technically I mean... really I'd like to educate myself.

My understanding is that I've got a computer on my bike that controls the amount of fuel and air into my engine. When I change my exhaust, why does this have to change?

If someone wants to take the time to explain this to me in this thread ... great! ... Meanwhile, I'm goin' to do some searching!

Ray.

 

You could ask the same question about almost anything. Why buy a four wheel drive and not put mudder tires on it to get the most traction. Why buy a V8 car and not put headers on it to get the best mileage.
I stayed with the HD download and my bike runs great. I don't care if there is a few extra ponies that I am not getting. I switched all my oils to syn and the operating temps went way down. Heat is not an issue for me.

 

Bear with me ... I've been reading and this is what I've got ... some questions?

Howdoes Electronic Fuel Injection control combustion in your engine?...........

Thefirst thing worth noting is thatunder normal conditions, the ratio of air to gasoline needed for complete combustion is 14.64 : 1. (According to what I've read)

With that known, we can use EFI to control the amount of fuel wesupply to the engine in order to maintain that ratio. How does this happen? The amount of fuelis controlled by how long the injectors are allowed to stay open. (AKA pulse width) This"time" is calculated by measuring the amount of airentering the engine and applying it to the ratioabove. If we only ever ran the engine under ideal conditions, this is all the information that we would need.However, since conditions change (i.e. engine load, temperature, etc ...) so to does the optimal air/fuel ratio for combustion. Anywhere from 10:1 to 18:1.

To control this ratio under ever changing conditions, the ECU (Electronic Control Unit)usessensors to monitor the amount of air entering the engine (MAP sensors)as well as the amount of oxygen in theexhaust (O2 sensors) to fine tune the fuel deliveryand maintain thecorrect air/fuel ratio. (There are other things measured and used, such as engineload, rpm, crankshaft position,system voltage,etc ... butI don't think their discussion adds anything to this post)

Upon further reading I found some examples of formulas that the ECU might use to calculate the pulse width for the injector.Along with the formulas were "look-up" tables that contained data (or factors) which had to be used in the formula to accountfor different conditions and loads. I am guessing that it isthese factors that differ according to what sort of performance download you choose to use on your motorcycle.Different managemet systems use different tables with different values. My understandingis that your ECUis set up with"stock tables" to begin with to achieve the best reliablity,mileage and emissions out of your engine.

With all that being said, I can see how changing the air intake would effectcontrol of the fuel/air ratio, because with a higher flow filter, the same change in throttle valve position would now equate to more air into the engine. In order to make this calibration you would need "new tables" that were generated through analysis of whatever filter you decided to install. That being said, Istill don'tsee how changing the exhaust alonewouldrequire a change of any sort to the ECU.

Unless we make a modification that directly effects the amount of fuelor air into the engine, the amount of O2 in the exhaust (which is what we measure) should remain the same, regarless of what pipes we've got bolted on.

 

OK this is the way I understand it 1rst, your fuel injection is controlled by a computer, the computer is programmed with a map or fixed set of instructions which tells it how much fuel to spray at any given RPM.When these things are stock that amount is dictated not by what will make it run the best or make the most horsepower but what will make the EPA happy.The newer "closed loop" system can adjust a small amount by itself to compensate for different temperatures, altitudes, humidity, whatever but no where near enough for a free flowing intake and exhaust.Harley tries to correct this with a "download" which is just a slightly richer map for the computer (it tells it to spray more fuel) it works OK for most bikes with minor changes in the intake and exhaust like slip-ons and a SE filter.
A Screaming Eagle Race Tuner (commonly refered to as a S.E.R.T is another device which includes an interface with your stock fuel injection computer and the software to create your own map or install one of the other included (canned) maps.The advantagres of the SERT are that because it's desiged by the same people that designed your FI computer it allows you to make the most adjustments and leaves no hardware behind. The disadvantages are it's a little complicated and requires a computer to use.
The Power Commander 3 or PC3 is an aftermarket stand alone device that bypasses your stock FI computer.It can make many of the same adjustments as the SERT but not quite all and stays connected to your stock wiring under the seat.Most say it's easier to adjust than the SERT I wouldn't know I have a SERT.
Then there's the DFO,TFI and a host of other piggyback systems that allow you to add fuel to certain RPM ranges these are the simplest as they require no computer to tune they usuall have a few screws or buttons and that's it.They give you more adjustability than a download but nowhere near as much as a PC3 or SERT people that don't like messing with computers like these set ups, the down side is that if your having a problem in an area they can't adjust your just screwed.
Last but not least there's the latest combination tuner/wide band o2 sensor type units like the Thundermax with auto tune this combines the tuning capabilitys of something like a PC3 with a wider band O2 sensor and software that allows the computer to tune itself for a wide variety of conditions.Most of the people I've heard from that have this type of system like it and think it works great the only downside I can think of is it's the most expensive.I hope this helps you out I typed this up at work an my boss is starting to look at me funy so got to go.

 

Thanks for the info Ed. I checked out the info posted in the tech section of the forum and answered a few other questions I had.

I've learned that pressure waves reflected back up an exhaust can restrict or improve air flow into the engine. (Wasn't completely aware of this phenomon)

That being said, I was under the assumption that HD EFI systems measured air flow at the intake to control fuel. Thus I assumed the ECU could compensate for this 'fluctuation' on its own. Apparently not the case. The article I read states that none of the HD EFI systems use "airflow sensing to extablish the fuel mix"

In fact, and again according to what I've been reading, the newer TC engines on HD's use MAP (manifold absolute pressure) sensors for control. When I read this, I naturally thought that this was a way of measuring the airflow. I was incorrect again, it actually uses manifold pressure to calculate the load on the engine. It is this "load", combined with many other inputs that is used by the ECU to look up values in a Fuel Map tablefor calculating injector pulse.

(Just for info, EFI systems used on EVO engines and pre 2001 FLH TC's used an "Alpha-N" system. I.E. they use throttle position to determine load.)

https://www.hdforums.com/m_299510/tm.htm

This link above gives a good explanation of EFI and some of the options for upgrades.

The post by Special EDis about how I understand the different options.

The SERT is a toolyou can use to actually"customize" the fuel map for the EFI. It takessome real knowledge to use effectively.

The dealer download is a chip upgrade that provides abit of abetter fuel map to help increase performance.Onequestion I wasn't able to answer... Are their differentdownloads for different air filters and exhausts, or is it only one generic download? I would like to think the chip ugradeI receivedwith the V&Hwould be different thanhad I installed SE slip ons.?.?.?

So far, from what I've read I would have to agree that an Engine Management Software system like SERT is the best option. However, I'm not convinced that it is necessary for my set up. The answer to the question in blue above may change my mind on this!

 

Nightrider's unique design to quickly and simply richen the closed loop fuel mixture on your TC96/103/110 engine from 14.6:1 to 14.2:1. This results in cooler exhaust temperatures. Recommended for bikes with upgraded exhaust and intake. http://www.nightrider.com/parts/

 

It is worth it. I had the local indy do it after I installed Cycle Shack slip-ons and Ness Big sucker ac. They recommended also installing a Yost power tube (probably wouldn't do it again, would go with using the sporty needle as had been discussedon here many times) so I had them do that and they rejetted based upon a typical exhaust and AC change.
Bike ran real rich (knowing what gas mileage was before and checking it after helped confirmed it), so I had them dyno tune it, they charge by the hour $65/hour. It took 1-1/2 hour but they only charged me for an hour. They told me every bike is different and what jet sizes works on most bikes may not work well on others. Makes sense.

The bike runs good now and I know it's setup right with the right air fuel mixture, which to me is better than guessing which jet size is correct thru trial and error.

 

No, but i will give you my stupid experience. Have 2009 Dyna Lo. Also have a 2006 carb Sporty Lo 1200. Have V&H straight shots, Big Sucker A/C, and rejetted the carb on the sporty. Runs great, sounds great, and I love riding the twisties on the Berryessa Road (and other great riding in North Cal ) on the Sporty. Since I had a good experience with that system on the sporty I did the same with the Dyna. My dealer told me when I bought the A/C that any changes would affect my engine warranty unless I did a Stage I download. EVerybody I talked to said it was a waste of money (and it was), but I was concerned about losing the warranty. The bike ran fine, got good mileage (my 96 engine was getting as good mileage as my buddy's Dyna with an 88). Only thing that bothered me was the popping on decel - sounded great on the accel, but sounded like Chinese New Year on the decel. I was told it might be a leak. I tightened everything I could find, even put a sealer on the slip ons - which will make them a bitch to take off now. Still popped. I took it to a local Harley tech (not a dealer). he rechecked for leaks and found none. He suggested I buy a PC an have it dyno'd. I ask my dealer about it, and he poo pooed the PC and said I needed a Race Tuner. His price for the Race Tuner and Dyno was nearly double my tech's price for the PC and Dyno. I bought the PC V tuner, had it dynoed - still popped. I took it back to the Dyno tech and he put another custom map in it - popping was reduced, but it ran like ****. Faded badly in the 2500-4000 rpm power band in 2nd, 3rd, AND 4th gear! I went back to him a third time - he futzed with it for an entire day - and got it running ok (certainly no improvement over where it was without the PC V) but it still popped. He gave up, said I have gotten more than my money's worth and he refused to work on it any further. I then called the manufacturer of the PC V, and he advised me to use one of the maps that came with my PC - but said he didn't think it could be mapped to eliminate the popping and that I needed different pipes. I put in his map - it now runs fine again, but still pops. And the worst thing of all - gas mileage is terrible - down at least 20%. I have called a half dozen Harley dealers, half a dozen independent Harley techs, and an online "expert". consensus seems to be that the V&H straight shots dont work well with the Dyna EFI no matter what map is put in - too much air flow. They advise different pipes - Rush or Bassani 2 into 1 and another map to accomadate pipes which allow less air flow.
Anybody have any experience with Rush or Bassani's on their Dyna? Sure wish I had just left it the hell alone. Its the gas mileage that burns me the most right now - and I cant get it back to the mileage I was getting w/o the PC V. Oh, and the plugs, which I check frequently do not indicate anything other than a good mix - certainly they dont look like its a lean burn. I now have to decide - do I chase another piece of advise (get new pipes) and throw more money at it, - or do I just pull the PC V out, pull the Straight Shots off and go back to stock? Still have all the stock parts.

 

Probably should have started a new thread rather than burying your question in a 3 year old one where the TS has been banned at least twice.