Fuel Injection v Carbs

[The Stranger:Me]

Once again, from the Fazer forum.
As previously mentioned we have as members 2 riding instructors from California Superbike School and one from Total Control. These guys tend to be very informative.
We also have 3 well known engine performance tuners. Dale Walker of Holeshot Performance, Ivan of Ivan's Performance Products and Marc Salvisberg of Factory Pro.

Ivan and Marc - think Shaun and Robert, but without the love. Makes for some interesting and heated threads.

Anyhow, below is a post from Ivan (as yet uncontested by Marc). I find his comments on FI v Carbs interesting particularly as they come from a (mostly) well respected tuner. I have edited out Ivan's comments about Factory Pro product so as not to incur the wrath of Marc

What a lot of people don't realise is that the EFI systems used on most motorcycles is not as fuel effecient as well tuned carbs.

With carbs, the engine will draw fuel as needed as load conditions change.

EFI that has only 2 inputs..
(throttle position & rpm and a MAP sensor which is only effective at 10% throttle openings and less because once the vacuum drops below a certain point the sensor cannot be a viable source of info)

The injectors will only do what they are programmed to do under the ECU/PC3's control, regardless of on-the-road load conditions; weight, up hill, down hill, 2 people 1 person.....
In other words the same throttle position gives the same amount of fuel regardless of the actual load condition.

The same is not true of carbs, because fuel flow is dependent on airflow (especially CV carbs) and different load conditions will give a different fuel flow at the same throttle position.

The only area that EFI is better than carbs is at very large throttle openings below 4000 rpm, when valve overlap and pipe design can cause trapping efficiency problems and tend to cause bogging when trying to tune for max power because the charge wont stay in the cylinder.
With EFI, some of the fuel can be trimmed away to lessen the trapping efficiency effects.

Efi systems take away control from you and give it to them (the manufacturer). With control over the fuel and timing, they can keep emissions where they want them and keep your front wheel on the ground....
and satisfy the EPA's requirement of "tamperproof" . And with fly by wire (Yamaha's YCCT), they can control the throttle too.

This will also prevent you from damaging the product while it's under warranty, ie: broken transmission parts, clutches and other drivetrain parts, fork seals and anything else that you can imagine. This makes the insurance companies and the EPA happy, and they can make the internal parts less costly due to the less stress that they will be under.

The new V-max is fly by wire, just like the R1 & R6..... TAMPERPROOF !! and it will have it's lower gear neutering as well..... all this for $18,000.00
(what a great deal !!)

Ivan

[imdying]

What a lot of people don't realise is that the EFI systems used on most motorcycles is not as fuel effecient as well tuned carbs.

Well that's such a broad statement that it can't help but be wrong

With carbs, the engine will draw fuel as needed as load conditions change.

As with EFI...

EFI that has only 2 inputs..
(throttle position & rpm and a MAP sensor which is only effective at 10% throttle openings and less because once the vacuum drops below a certain point the sensor cannot be a viable source of info)

Only two? orly?

Basic Suzuki (for example) EFI has:
Intake Air Pressure (IAP or better known as MAP)... basically 'load'
Crankshaft position... engine speed... RPM
Throttle position... throttle opening %

And some others for compensation:
Camshaft position... which piston is firing next... adjust injector or ignition time per cylinder among other duties... also lets the ECU know if the bike should be accelerating or deaccelerating
Atmospheric pressure sensor... is the bike up in the hills or near sea level
Engine coolant temp sensor... is the bike cold or stuck in traffic
Intake air sensor... is the bike breathing hot or cold air
Oxygen sensor (narrow band)... does fuck all but can be used to keep the cat warm
Battery voltage... can correct the injector time if the battery is getting flat or the alternator or RR is getting flakey
Starting signal... is the bike being cranked?
Speed signal... couple with the cam position sensor, lets the bike know if it's going up or down hill (among other things)
Tip over sensor... time to stop, we've crashed the bike!!!
Over rev limited signal... top to cut the injection, the bike is overrevving

Only 2? That's three for basic injector timing, and another 10 for compensation due to external issues by my count. There may be others... would need a workshop manual on a particular bike to get a firm count though.

The injectors will only do what they are programmed to do under the ECU/PC3's control, regardless of on-the-road load conditions; weight, up hill, down hill, 2 people 1 person.....
In other words the same throttle position gives the same amount of fuel regardless of the actual load condition.

Well we've obviously disproved that already.

The same is not true of carbs, because fuel flow is dependent on airflow (especially CV carbs) and different load conditions will give a different fuel flow at the same throttle position.

Much the same as EFI... except there's many more things carbs cannot compensate for... Lets take coolant temp... oh, carbs can do that... that's right, it's called a choke. Don't know about you, but I sure don't miss having a choke...

The only area that EFI is better than carbs is at very large throttle openings below 4000 rpm, when valve overlap and pipe design can cause trapping efficiency problems and tend to cause bogging when trying to tune for max power because the charge wont stay in the cylinder.
With EFI, some of the fuel can be trimmed away to lessen the trapping efficiency effects.

Sure, that's the only place they're better

Efi systems take away control from you and give it to them (the manufacturer). With control over the fuel and timing, they can keep emissions where they want them and keep your front wheel on the ground....
and satisfy the EPA's requirement of "tamperproof" . And with fly by wire (Yamaha's YCCT), they can control the throttle too.

Right... cause changing jets and needles is sooo much harder than using a TEKA box or a PCIII or (insert favourite EFI tuning tool here)

This will also prevent you from damaging the product while it's under warranty, ie: broken transmission parts, clutches and other drivetrain parts, fork seals and anything else that you can imagine. This makes the insurance companies and the EPA happy, and they can make the internal parts less costly due to the less stress that they will be under.

Yes, this is true, an EFI system will generally help you prevent carnage.

The new V-max is fly by wire, just like the R1 & R6..... TAMPERPROOF !! and it will have it's lower gear neutering as well..... all this for $18,000.00
(what a great deal !!)

No such thing is tamper proof... so it's outside of the authors capabilities, that doesn't mean it's outside of everyones... Won't surprise me if we see FBW piggyback units (like a PCIII) in the near future, assuming enough bikes come out with it to make it worthwhile (and assuming the developers actually find sufficient gains to make it worth bothering with in any case).

[vifferman]

Yeah, what he said.

Basic Suzuki (for example) EFI has:
Intake Air Pressure (IAP or better known as MAP)... basically 'load'

Due to the dynamics of the airbox and intake system on bikes, and their small engine displacement, this doesn't work very well on motorcycle engines at low revs, so that's why O2 (and other) sensors are fitted to augment the IAP sensor. So the article was at least right for that bit of information.
As long as the sensors are working correctly (and if they aren't, the EFI will generally pick up errors), the EFI will keep working faultlessly mile after mile, year after year, with no maintenance needed. Carbs on the other hand do need adjustment and maintenance, and things such as needles, slides etc. can wear and stuff up your fuelling. If the injectors don't get clogged, there's virtually nothing to wear out in an EFY system.

[dhunt]

Right... cause changing jets and needles is sooo much harder than using a TEKA box or a PCIII or (insert favourite EFI tuning tool here)

I think this is the biggest advantage of a EFI system over carbs. It has turned a hardware problem into a software problem. We do this all the time with our products. The advantage of this is it is cheaper/easier to fix software problems and generally easier to design. Which allows you to customise your product (in this case the motorbike) to suit the customers needs/regulations without having to do another hardware cycle (which is both expensive and slow).

[Ixion]

If the injectors don't get clogged, there's virtually nothing to wear out in an EFY system.

Injectors wear. So do throttle bodies and their associated spindles and such. Fewer things than on carbs, granted.

But EFI depends totally on the supply of magic smoke . If it leaks out foir whatever reason you are TOTALLY stuffed. Whereas carbs, whatever goes wrong can almost always be fixed with the BLOODY BIG HAMMER. And maybe replacing a few bits.

[imdying]

Due to the dynamics of the airbox and intake system on bikes, and their small engine displacement, this doesn't work very well on motorcycle engines at low revs, so that's why O2 (and other) sensors are fitted to augment the IAP sensor. So the article was at least right for that bit of information.

Whilst I don't totally disagree on that point (although tecnically it's incorrect as high valve overlap and short intake runners are more responsible rather than airboxes), it's worth noting that even the best carbs struggle when they have a weak vacuum signal. Additionally, the granularity or resolution on MAP sensors has increased dramatically in the last 20 years, and continues to do so, where as carb development for sportsbikes is essentially dead. In other words, EFI keeps getting better (although to be honest, that problem is pretty much academic these days in any case). Also additionally, it isn't unusual for an EFI bike to run multiple IAP/MAP sensors, which also (like the cam position signal) allows for offset cylinder tuning.

[dhunt]

But EFI depends totally on the supply of magic smoke . If it leaks out foir whatever reason you are TOTALLY stuffed. Whereas carbs, whatever goes wrong can almost always be fixed with the BLOODY BIG HAMMER. And maybe replacing a few bits.

Yes what ever you do don't let the smoke out. You can't put it back in again.

You've got to remember most modernish bikes already have a CDI/TDI unit which has smoke it in. So now we just have a box with a bit more smoke in it. Electronics is also getting more robust these days (translates harder to let the smoke out) which also helps.

[imdying]

But EFI depends totally on the supply of magic smoke . If it leaks out foir whatever reason you are TOTALLY stuffed. Whereas carbs, whatever goes wrong can almost always be fixed with the BLOODY BIG HAMMER. And maybe replacing a few bits.

This is somewhat true.

On the one hand, carbs will continue to run a bike if they're sick, they'll just run the bike like a piece of crap.

On the other hand, EFI will continue to run the bike if it's sick, they'll just keep shutting down higher functions and limp home until something fatal gives up the ghost.

Injectors clog, but then so do jets. Neither system is aware of it, although with a wideband O2 sensor an EFI system could perhaps be made aware of it. They don't though, it's pretty unusual for an injector to clog suddenly (filters are good), they are more likely to gunk up over time due to lack of maintenance resulting in a sedimentary buildup.

Of course, if some part of an injection system dies, a bikes dashboard will usually give you a fault code that lets you know which bit actually died...

Given the places people like the Stromtroopers have taken their DL bikes, it is safe to say that the reliability of EFI in adverse conditions is certainly no longer in question.

[vifferman]

Whilst I don't totally disagree on that point (although tecnically it's incorrect)

This is somewhat true.

On the one hand..
On the other hand....
...it's pretty unusual ...
they are more likely ..
...will usually ...

Stop prevaricating, Man! Don't beat around the bush!
Try this:
Bullshit!
Bullshit bullshit BULLSHIT!!

[imdying]

I have a certain amount of respect for each of you, and I'm doing my very best to supress my often hostile nature. As such, I don't want to slam anyone simply for sharing information/opinions; that wouldn't be very nice.

It's worth noting that on a such a broad topic such as 'carb' and 'EFI', there are few absolutes. What you said was not entirely baseless, from my limited understanding I know that there have been cases where airbox resonance has affected sensors in the past.

It is safe to say though, that modern sensors and ECUs are now more than capable of dealing with the high update frequency and fine granluarity of information sent and recieved in modern small displacement injection systems.

[avgas]

haha i had the same argument.
I dont really care which one - im a fan of the tech stuff, but i currently ride carby'd. For one simple reason - i like to adjust my idle depending on when and where i am riding.
EFI on anything is bound to have its strengths and weaknesses for one simple reason - it is discrete control on a slightly unstable system.
Rather than going in depth with why this is bad, i will just say the following:
- KISS works on items you wish to control, it is inefficient on the items you don't care about, always has been always will be. This is the sales pitch of new technology, they cant claim to do a better job (especially if you happy at the current level), so they have to claim that they have a more efficient way of doing it.
- External control (i.e. in this case) will always be more effective than internal elements. However this is double edged sword as the external elements can be defective.
- Blaming the tools NEVER fixes the problem.

[geoffc]

I know that Fuel Injection wins over Carbs, but I love the big Carbs on my VTR1000. To me they add to the personality of the bike. Both my 'Cages' have F.I. but...who cares about them.

[imdying]

i like to adjust my idle depending on when and where i am riding

You needed give that up... setting the idle on your EFI bike is the same as on your carb'd bike... you turn the knob.

I know that Fuel Injection wins over Carbs, but I love the big Carbs on my VTR1000. To me they add to the personality of the bike.

I have RGV250, it has carbs, they do all they need to do Sure changing jets is a pain, but I'm not racing it, and it's really not that difficult after a little practice.

[vifferman]

You needed give that up... setting the idle on your EFI bike is the same as on your carb'd bike... you turn the knob.

I tried turning the knob - it hurt too much.
The Cakemixer has a Special Stealth Screw (hidden 'neath a rubber plug) that adjusts the doohickey (technical term).

[avgas]

On the other hand, EFI will continue to run the bike if it's sick, they'll just keep shutting down higher functions and limp home until something fatal gives up the ghost.

You are right on the above statement.....if the bike is currently running. If its not and you have to go through boot sequence, its a different ball park.
rule one - never water blast fuel injected bike.
took me 1 hour to dry out air intake enough to start bike.
However some would argue this was a good thing.