Fuel Injection, mech vs electronic

[oj]

Which system is better?  Naturally asperated and running at WOT for a brief time.

[SPARKY]

In my limited opinion it is going to be determined by the air delivery system more than how the fuel is delivered.

[manta22]

OJ;

Running at WOT the two should be equivalent if set up properly. The electronic system gives far better fuel /air accuracy at part-throttle.

Regards, Neil  Tucson, AZ

[Milwaukee Midget]

Generally, I agree with Neil, but here's a thought -

Air density changes constantly on the salt, and it's not unreasonable to expect it to be different 4 miles down track.

Additionally, air speed around your air inlet can have an impact on the air density your intake sees. 

What may be "spot on" at the starting line might be a lean condition at speed at WOT at the 4 - or maybe too fat.

An electronic system will monitor and accommodate such changes during the run. 

IMO, I'd rather let the computer do the fine tuning real-time.

[oj]

How long will the O2 sensors last and what about oxigenated fuel?  Can I run alcohol or is that considered 'fuel' and changes the class? 

[Milwaukee Midget]

How long will the O2 sensors last and what about oxigenated fuel?  Can I run alcohol or is that considered 'fuel' and changes the class? 

My O2 sensors lasted an event on leaded 119 octane.  Event gas - 3 grades available, which are the only gasolines allowed at Bonneville - includes an unleaded option.  Alcohol is considered "fuel" in LSR at Bonneville.

It varies from year to year as to which gas is available and as to how ERC formulates their products - they're always working on their formulations.  Often, it's little more than a change in the suffix letter with minimal changes to the effectiveness.

Can't remember what was available last year - maybe somebody else can answer?

http://www.ercracingfuels.com/sxs1.htm

[oj]

How long will the O2 sensors last and what about oxigenated fuel?  Can I run alcohol or is that considered 'fuel' and changes the class? 

My O2 sensors lasted an event on leaded 119 octane.  Event gas - 3 grades available, which are the only gasolines allowed at Bonneville - includes an unleaded option.  Alcohol is considered "fuel" in LSR at Bonneville.

It varies from year to year as to which gas is available and as to how ERC formulates their products - they're always working on their formulations.  Often, it's little more than a change in the suffix letter with minimal changes to the effectiveness.

Can't remember what was available last year - maybe somebody else can answer?

http://www.ercracingfuels.com/sxs1.htm

Thanks for that, I was wondering. 

[kiwi belly tank]

How would you like to heat your home, with a coal burning stove or a temperature control on the wall?
  Sid.

[wobblywalrus]

It is common practice on bikes to use the O2 sensors only for mapping and to disconnect them and let the mixture trim be adjusted as needed by the environmental sensors.

[RidgeRunner]

    Electronically controlled direct injection is opening the door to a whole new world for gas engines.  If I had the means that's where I'd be applying them.

    Yes Sid, going from my wood stove to a thermostatically controlled wood pellet stove a couple of years ago brightened the light I'm seeing  

                     Ed

[wobblywalrus]

My 2013 street Triumph has a Keihin EFI system.  Sometimes I tweak the mapping a little bit in the shop.  Then, the engine is turned on and idled for 10 to 20 minutes to get up to operating temperature at closed throttle opening.  The EFI takes a reading from the O2 sensor when the engine is fully warm to adjust the fuel trim for closed throttle.  Usually this is between 15 and 20 minutes after the engine is started.  Then it is time to go riding in order to set the trim at partial throttle opening.  Off I go up the freeway to a neighboring town.  About ten minutes after I leave the ECU takes an O2 reading and it adapts the part throttle trim.  It takes another reading on the way home.

What this says is that if the bike was raced at Bonneville the O2 sensors would not be used by the ECU during the race.  We bike guys realize this, and often set the mapping on a dyno using the shop O2 meter stuck up the tailpipe instead of the bike's O2 sensors.  Some guys toss the sensors and do not use them at all.  In my case, with leaded gas, the jetting is set on the dyno based on torque and horsepower readings.  Sometimes we do not use an O2 sensor for the dyno work.  This elaborates on a previous post.  It is possible to dance around the o2 sensor and its issues.  This makes electronic fuel injection more attractive.     

[oj]

We tune with EGT, each cylinder.  If we used an O2 (and don't because of leaded race gas) the O2 is in the collector and would read a combination of 4 cylinders of an 8cyl.  But then, we can't change the tuneup as it goes down the track either - well, just a little. 
But my experience is drag race and just a few seconds at WOT.

[wobblywalrus]

All of my experience is limited to modifying the keihin street system to something that could be used for LSR.  Like said, there are other sensors that the control unit uses to keep track of things.  The O2 sensor is used every 10 minutes when at partial throttle so it is a minor player on the triumph.  The other sensors do most of the input that is used more of the time and they are not sensitive to lead in the gas.

These comments about how us bike guys deal with the O2 sensor is all I can contribute.  I do not know much more about EFI and zip about mechanical injection.  In the desert racing world it is not unusual to start out on a freezing cold morning at one elevation and to go through lots of temperature and altitude changes throughout the race.  EFI gives a competitive edge 'cause of its ability to adapt to conditions.

Conditions do not change as much at B'ville, although they do.  It sorta gets down to personal preference, ability, and how much an extra little bit of power is needed.  I am real bad at electronics so the mech system would be a better fit if I had to set it up.  The EFI would work better if someone smart set it up and my involvement was minimal.  The human factor is important.  The most accurate and precise system is no better than a simple one if the folks working with it cannot figure it out.

[Stainless1]

Density altitude only changes about 5000 ft through the day.... and depending on how long you are in line it could screw your tune unless you guess well.  Oh, unless you are blown alcohol and then you can run a little rich and be ok...  We ran an AEM by cylinder data system on Max's Liner (blown alcohol mechanical injection) one year... the data kept telling us it was lean... the drag racer influencing Max's tuning decisions said it was rich... the hole in the piston told us never listen to drag racers at Bonneville....
So an aftermarket EFI, MOTEC, FAST, AEM and a variety of others can tune by cylinder, update on the go to compensate for manifold ram air pressure and make your tune whatever you pick.  Leaded fuel will not kill your O2 sensor in several years of racing.... ours has survived 5 years, start with a really good lab grade Bosch sensor... you can limit it's adjustment range should it decide to die suddenly from lead poisoning.  You can use EGT and O2 in each cylinder to influence your tuning decisions to ensure you are getting all you can from your motor...
We used to be carb guys, used weather station to pic jets 5 back in line... thrashed to get them in the 4 carbs and driver in on time... Now we use the MOTEC, get our coaching from Dave Dahlgren at Engine Management Systems, he can set you up from start to finish.  Appropriately for the Voodoo of EFI, he is located in Mystic CN... 

[jacksoni]

Tune-ability has been well covered here with EFI getting the vigorous nod. If you are talking HP mech and EFI in the same manifold are going to be pretty close though either have the possibility of changing injector location and there may be some atomization/spray pattern differences that might make a small difference for which dyno testing is the only solution. People also talk about when to inject the fuel- on an open valve, a closed valve, a hot valve half way or any way you can think of with EFI. Part throttle might make some difference. WFO high rpm not so likely as the duty cycle is going to likely be more than the valve open time duration so you become not too much different than MFI.

Many folks will argue whether a carb and EFI can be equivalent or which is better HP wise. Fuel economy and part throttle and driveability and especially emissions aside (who cares about that at Bonneville) with a right tuneup it is going to be a toss up. There are lots of folks who will say a carb will win a HP battle. The problem with those tests (my opinion) is that air flow and manifolding become more important and they cannot be apples to apples comparison. And Stainless mentioned the tune issue with a carb when the DA shifted a bunch while in line trying to get a carb right. And yes holes in pistons and burned valves are a problem if you don't get it right and blame the gasoline off the ERC truck. (have seen that happen). An then there is my crewmember/friend who built a car in Maryland and was tuned here, last minute deal and loaded and left for Bonneville with nary a spare part or jet or plugs and barely a screwdriver in the tool box and set a new record off the trailer with no tuning adjustments. YMMV

With a MFI you need about 3 wires (ok run a mag)- Ign switch and starter button. With EFI fuel and ignition, you will have about 50. You pays your money and takes your choice.....