Why EFI Vehicles Need To Be Tuned

Terry1955 · #1 12-03-2005, 07:57 PM

For all the people that don't quite understand why you need a Race Tuner (SERT) or Power Commander (PCIII USB) for your Harley please read this. This was not written by Harley (who makes the SERT-Race Tuner). I favor the Race Tuner but will concede that the PCIII is also a good piece of equipment. But PLEEEEEEEEEEEEEASE...Don't use the HD download

Why EFI Vehicles Need To Be Tuned
The need for "re-mapping" a fuel injected bike only arises when internal and/or
external engine components are replaced with non stock components, i.e. air
cleaners and exhaust systems. When components are changed on an engine to
any non stock or "performance" part you alter the way that engine moves air in
and out, thus altering the Volumetric Efficiency. If the V.E. is altered the stock
ECM fuel settings continue to deliver fuel at a base-line rate unaware that the air
delivery has changed. With the fuel delivery unchanged and the fact that this
engine is receiving more air there is a lean condition created that will most likely
cause engine damage due to higher heat levels in the combustion chamber. A VTwin
engine is just that, two separate cylinders in a "V" configuration which
generally speaking will cause these cylinders to flow air at a different efficiency
rate. This effect is mostly caused by a non tuned exhaust system that flows air at
different rates from front to rear thus changing the volumetric efficiency.
With the advancements and complexity of today's fuel injection systems
simplicity is not necessarily advantageous. The need to compensate for fuel
delivery to a modified engine ideally would be performed by the original engineer
or programmer of the ECM since they would be the one most knowledgeable on
this system. Since this avenue is not available to the average consumer, a
method of putting a "Band-Aid" type programmer (HD Download) to compensate
for the modifications is the easiest solution, however it is not necessarily the best.
Installing a "Band-Aid" on a system with this complexity can sometimes create a
whole new realm of problems that the original engineers could not have
anticipated.
The Dyno Jet Power Commander unit with it's 126 fuel adjustment cells and 126
spark timing cells offer simplicity that cannot always compensate for the high
demands of a modified V-Twin engine. Especially when the cylinders have a
different V.E. rate, this also offers a "Band-Aid" solution at best.
The H-D EFI Race Tuner Kit offers 220 Volumetric Efficiency adjustment cells for
each cylinder along with an Air Fuel Ratio (AFR) adjustment table that has an
additional 120 cells for a total of 560 fuel adjustment cells. There are also 220
cells for each cylinder to compensate for spark timing, fuel enrichment cells for
cold start and cranking enrichment for easier starting. With these extra tables and
cell adjustments there are over 1000 adjustments that can be made. Also
consider the advantages with having the ability to set your idle mixture as well as
idle speed and having access to your own rev limiter which is adjustable from
4000 to 7500 RPM.

__________________________________________________ _________________

The Dyno Jet Power Commander does not alter the stock rev limiter. That is why
many people use the Stage 1 Download along with it. The Stage 1 Download
raises the rev limiter to 6200 RPM.

ThudMeister · #2 12-03-2005, 08:11 PM

It's not just EFI bikes, the EXACT same thing happens to carb bikes, we just have to change jets.

Terry1955 · #3 12-03-2005, 08:25 PM

I know Thud, it's just that you guys aren't having the problems that us EFI guys are having. Carbs are so simple to adjust or modify compared to the Fuel Injection. No more tinkering in the garage. Gotta have a laptop, dyno, etc. etc............

Terry

ThudMeister · #4 12-03-2005, 09:40 PM

Once you have the purchased all the EFI goodie$$, loaded the software on your laptop, and install your own dyno, its easy.

[sm=drooldude.gif]

I was shocked how much I had to spend on my first EFI bike, and I am a gadget freak.

Grover · #5 12-03-2005, 10:21 PM

OK if a man buys a HD Race Tuner, can the indy shops dyno it or do I take my bike to a HD stealer with a dyno?

Terry1955 · #6 12-03-2005, 11:57 PM

Grover,

Any certified dyno tech that has the HD Sert software (actually he should be able to use yours) and understands it should be able to dial in your bike. I'm lucky that I have a good dealer with a great dyno tech.

Terry
[sm=biker2.gif]

Grover · #7 12-04-2005, 01:21 AM

Does the software come with the SERT?

Terry1955 · #8 12-04-2005, 02:09 AM

Yes Grover,

The software comes with the SERT. When you get the map you want it is saved on your computer. You can pull it back up and modify it at any time. There are also a ton of canned maps (kinda like PCIII) where you can pick the closest one to your modifications and just download it to your bike. When you unplug the SERT from your bike you leave nothing hanging on. Very clean. The SERT is registered to your bike and can't be used on anyone elses bike.

Terry

airfuel · #9 12-06-2005, 01:07 PM

Great article, just a clarification.

The PC3 usb model has the ability to map 225 individual cells per cylinder. (maximize map resolution)
It also has the ability to map each cylinder individually so you can take care of the differing VE from front to rear. (advanced map)

It also has the ability to do the same with regard to timing with each cylinder.

Both are great tuning tools but in the end it comes down to who tunes them.

John

bobcowan · #10 12-06-2005, 03:28 PM

I don't have my new bike yet, and havn't played with the racer tuner yet, so I could be off base here. If I'm wrong, terry, please correct me. Over the last year, I have have been gaining experiance with aftermarket EFI. I have installed an 8 stack EFI with a haltech computer on my V8 Ford. I realize there are a lot of differances between a water cooled V8 and an air cooled V2, but it seems that the concepts would be similar.

Moving from a carb to EFI is more complicated. There's a learning curve. There are also differant tools and parts you need to do the tuning. But there seems to be some misconceptions about that.

1. EFI is easier. I can change the jetting without ever taking off my seat belt. Drive a little, punch a few keys, drive a little, punch a few keys. It doesn't take long to dial it in for perfect drivability. You can easily go too far and make it too lean/rich. But then in a couple of key strokes you're back in the right direction.

2. You don't need a dyno. Actually, I've not found a dyno to be overly helpfull for a street vehicle. But a good A/F meter is really helpfull.

3. Data logging is extremly valuable for the street driver/rider. You can see where your A:F is where you ride most. Then you tap a few keys and make the appropriate changes. Better than a dyno, IMO.

4. Closed loop is the ideal. To have the comuter adjust for changing situations is a huge leap in technology. But that only goes so far. Max adjustment is only 15-20%. And you don't want it for WOT. And if you have a radical cam it doesn't work well at idle, either. But for general driving/riding this is the way to go, no question.

5. Same goes with timing. Add timing until it pings, then back off a couple of degrees. It would be nice to make changes according to climate, altitude, etc. The problem I see is that you set it for ideal conditions to make most power, then have to back off because something changed. But you're on the road and don't have your lap top. A smart rider will be somewhat conservative, I would think.

Like I said, I don't have my new bike yet. But I'm looking foreward to playing with the new computer system.

But that's just my opinion. I could be wrong.