Tfi And Fuel Injection Explanation Needed.

[cambeck66]

This was posted in another post and before I run out and drop money on something else, is this true? Sounds like he knows what he is talking about, but I am no expert at these.



Guys, what I am about to say is going to make some people sit up and get angry and for others, it might be a very big wake up call. I have no personal grudges here against anyone and I am not posting this to pick a fight.

As good a Company Dobeck is and even if they have the best customer service in the world, the following will make that not matter. I have nothing personal against them, but they need to step their products up as it is not even close to the competition.

If you look at Dobeck’s web site you will see they claim it is easy to set up and you don’t need a PC and all the good stuff. Whell here are the big negatives.

Dobeck, Noss Boss and similar units with tuning company names on them, can only ADD more fuel. They cannot be set up to supply less fuel that what the stock ECU supplies.

Units like the Yoshi and powercommander can both add and remove fuel.

Well, Dobeck on their web site actually state exactly that, that their untis only supply more fuel, and they argue that if you add more performance parts you will need more fuel, so why bother with removing fuel.

Well this leads me to my LTR story.

I own my own dyno and I do almost exclusively only dyno tuning and race engine building. I have tested LTR’s with Yoshi, powercommander and TFI units, and set the bikes up for both trail riding and racing. I always test them with the cherry bomb, cause seriously, what is the point of running it without a cherry?

The 1st thing that jumped at me is that each time I tested a LTR with a Dobeck TFI, I lost a massive amount of low down torque and RPM. From 2000 to around 5000 RPM, the power is about 5 to 15% less than running the LTR without the TFI and only on the cherry. So, about 60% of your RPM ranges power drops by fitting a TFI. Top end RPM was ok, but not the best.

So, let’s explain why.

Do yourself a favour and download all the maps for the LTR from powercommanders web site. You will also need their software programme to open the files and see what the fuel map is made up of. All for free.

Let’s start with a basic LTR, stock pipe, stock filter, open airbox with cherry. Map M329-003
If you look at the map powercommander uses, 70% of the map is showing negative values. Meaning 70% of the time the stock ECU over fuel the motor. In some cases nearly by 40% to much fuel!!! Also, not a single one of the settings for WOT has a positive value, meaning the bike with this setup is supplying too much fuel at full throttle.

Now, ask yourself, what is the use of a TFI that can only add more fuel?????? It might work for 30% of the time on that bike, but that’s it. For the rest, it is losing power and supply to much fuel.

Now let’s look at say map m329-018. It is for a LTR running a Curtis Sparks full exhaust, Stock air filter, Air box lid removed, with cherry. Here 98% of the map has negative values, meaning at 98% of the RPM range the TFI is useless. Also, not a single positive value at WOT, so again, on this setup the TFI is useless and does nothing but waist fuel and drop power output.

Now let’s look at map (m329-036) which is made for a LTR with HR1 Shorty race slip-on, JE high compression piston, Webcam Stage 1, Pro Design intake kit with K&N filter , Air box lid removed, and cherry. Surely this one will need more fuel as it is running all sort of high performance parts.

Well, NO. Again 98% of the settings are negative and not slight negatives either, in a lot of cases you have to reduce the amount of fuel by 20%. Again, a TFI on this bike is a waist of money.

I actually dare you to look at all the available maps to find one that does not need major reduction in fuel at the low end. Also, on all my dyno map I have built for the LTR, not a single one needed more fuel in the low or mid RPM ranges. In all cases 80 to 98% of the time it needed less fuel.

What does this all mean? If you want to lose power, install a TFI.

Also one major problem I have with this, is that if you supply too much fuel, HP and torque will drop, plus in some cases to much fuel can also lead to engine failure. So there is a very serious reliability risk with the TFI’s, because you start of with a stock ECU that already adds to much fuel, plus now you add a TFI that even adds more fuel on top of that.

In 98% of the time, you will be better of running the bike without the TFI and just use the plain old Cherry. If you want more power than that, go for a powercommander or Yoshi unit.

Sorry to break it to you like this, but that’s the facts. On another make and model bike the TFI;s might be worth while bit on a LTR... you decide.

[quadracer786]

great info

[CQR]

As a general rule the most power(not economy) is achieved at around 12.5:1-13.5:1 air fuel ratio. That ratio is fat enough to give good power and to keep things cool. That would be at a WOT condition. It would be way too fat for idle. A 14.7:1 AFR is the best for emissions but is too lean for power and reliability. The AFR on a dyno sheet is a very important factor for mapping. Just My .02

Clint

[Freez]

I wrote the write-up.

I use 13:1 as the base line to start setting up the EFI.

If the map sais the PCIII is removing something like 40% of the fuel, then it means that the stock setup is most likely supplying a A/F ratio of around 11:1. that is way off the charts rich. Then on top of that the TFI will add even more fuel, taking the A/F closer to 10:1.

Looking at all my dyno runs, the LTR will actually make more overall power without the TFI than with it on the bike.

The cherry bomb by itself supply the fuel you need for most upgrades. In fact a little too much and you need a powercommander or a yoshi box to lean out the mix to get an A/F ratio of around 13:1.

I joked with a guy once. I told him the LTR will make more power with the TFI sticker on the bike than with the unit itself, and it is actually true.

I don’t have anything personal against the TFI, and the can work ok on other quads, but on the LTR it is a power killer. The TFI should have never been made available for the LTR, because of they tested it, they would have found it messes up the power.


One more bit of info.

The Yoshi unit also has quite a few limitations and I have personally run into them on LTR's. The Yoshi unit will only allow you to add or remove up to a maximum of 20%. On a few LTR's I have done, this limits me especially at the low end of the rev range and the bike keeps on running rich.

Also, the Yoshi unit only adjusts for every 500 RPM, where the PCIII adjust every 250 RPM. The Yoshi unit also has less throttle positions than the PCIII.

The PCIII (powercommander) has more than double the setting than the Yoshi unit and it also does not have a limit on how much fuel you can add or remove. Well I have never run into a limit myself.

Also, Yoshi unit needs a special programmer and it cost money, where the CPIII programmer is for free.

[cambeck66]

I wish my sponsors carried the PCIII. I think they only carry the PIM. I'll have to do some serious looking. At least I will have a brand new TFI to sell, off set some of the cost. Where are the best places to get a PCIII?

Cameron

[schl48]

thats a good post. the facts are the ecu supplys all voltage to run the quad. spark,fuel and so on and all the programmers do are intecept the signal from the ecu and send it to the injector. so if u can't get enough fuel from the ecu u are sol. u would need software to reprogamm ecu. now if we got the software thank of the millions these companies would lose and we would save.
this also bring up another point once cherry bomb is installed that should be all the fuel u could get so if you're not lean with a programmer u can't be lean with cherry bomb.

[rivermobster]

Quote:

As a general rule the most power(not economy) is achieved at around 12.5:1-13.5:1 air fuel ratio. That ratio is fat enough to give good power and to keep things cool. That would be at a WOT condition. It would be way too fat for idle. A 14.7:1 AFR is the best for emissions but is too lean for power and reliability. The AFR on a dyno sheet is a very important factor for mapping. Just My .02
Clint[/b]

I'm with this guy ^^^^

To me the ONLY thing that matters with your motor on a dyno is whats coming out of the pipe! HP numbers are a pure calculation, they dont mean a damm thing. Torque numbers are the only other thing that matters, and a slight change in tire pressures can skew those as well.

Personally, i have no idea what those numbers on a fuel map actually mean, but i have been turning wrenches for over 30 years, and i have NEVER built (up) a motor that has needed LESS fuel than it did when it was stock!!!

Hey Freez, if your the guy with the dyno, is it a DynoJet Dyno? How bout you post some run files with the torque and a/f numbers overlaped. I've been wrong before, so I'd sure like to see wacha got...

[jstanely]

When i had mine on a dyno we had to take away alot of fuel.these bikes run rich when there stock and when i put on a dasa fuel airfilter cp 13.7 and pc3 we still had to take away fuel.It all depends on ur elavation.

[rivermobster]

Quote:

When i had mine on a dyno we had to take away alot of fuel.these bikes run rich when there stock and when i put on a dasa fuel airfilter cp 13.7 and pc3 we still had to take away fuel.It all depends on ur elavation.[/b]

what elavation are you at? im close to sea level, and they are lean as hell down here!! you would think the air pressure sensor would compensate...

[jstanely]

I think im around 2400 feet or something like that.Talkto driver311 he stays on a dyno and has also said he has to take alot of fuel out of diff rpms on the ltr.