Fuel Injection Question..

[degrom]

With Fuel injection engines...

If I change the exhaust to a flow better and the air intake to breath better.
Why do you have to Dyno it after all the modifications?

Does the engine management system not compensate for the changes in the system and keep the mixture in balance?

[Kwaka14]

Kawasaki use a throttle position indicator as opposed to an airflow meter so the dyno thing is required, I'm not sure if that applies to all injected bikes but definitely an issue for the ZX12 also

[degrom]

Kawasaki use a throttle position indicator as opposed to an airflow meter so the dyno thing is required, I'm not sure if that applies to all injected bikes but definitely an issue for the ZX12 also

That makes perfect sense!!! So the computer does not calculate the mixture then,it just reads its memory and see what amount of fuel is needed at the current throttle position...

[sAsLEX]

That makes perfect sense!!! So the computer does not calculate the mixture then,it just reads its memory and see what amount of fuel is needed at the current throttle position...

Correct, to make a truly self adjusting system would require lots of sensors and computing power which will add to weight and cost so they don't do it.

[The Stranger:Me]

With Fuel injection engines...

If I change the exhaust to a flow better and the air intake to breath better.
Why do you have to Dyno it after all the modifications?

Does the engine management system not compensate for the changes in the system and keep the mixture in balance?

You don't have to and no, in general the fuel injection won't automatically compensate.

Unless you have a Power Commander (or similar) you can't adjust the A/F ratio anyway.

However, if you do put it on the dyno you can check it's not too lean (unlikely) and if you dyno it with a PC you can probably get better performance from it.

[degrom]

Mmmm...(Kwaka12R) But I am looking at a Honda and this is what the manufaturer is saying:

The essence of this system is the continuous use of several variables to control the injected-fuel quantity. Technically, the PGM-FI is an n-alpha mapped injection system, meaning that the basic variables are the engine speed (n) and the throttle angle (alpha). Based mainly on those measurements, the system looks upon its fuel map for the fuel delivery corresponding to the n and alpha of the moment. The computer then adjusts this fuel delivery according to four additional variables; airbox pressure, engine coolant temperature, intake air temperature and atmospheric pressure.

This process of recalculation of fuel delivery is repeated many times per second to ensure continuously correct mixture for conditions, and to provide optimal performance and remarkably crisp throttle response over a wide operating range.

[The Stranger:Me]

Mmmm... But I am looking at a Honda and this is what the manufaturer is saying:

The essence of this system is the continuous use of several variables to control the injected-fuel quantity. Technically, the PGM-FI is an n-alpha mapped injection system, meaning that the basic variables are the engine speed (n) and the throttle angle (alpha). Based mainly on those measurements, the system looks upon its fuel map for the fuel delivery corresponding to the n and alpha of the moment. The computer then adjusts this fuel delivery according to four additional variables; airbox pressure, engine coolant temperature, intake air temperature and atmospheric pressure.

This process of recalculation of fuel delivery is repeated many times per second to ensure continuously correct mixture for conditions, and to provide optimal performance and remarkably crisp throttle response over a wide operating range.

I think you will find though that the scope of that adjustment is somewhat limited.

An example of a mechanism of which you speak is the O2 sensor in the exhaust. It is designed to keep the A/F ratio optimised for the catalytic converter, not for performance and comes into play only at low RPM. It is there so as the manufacturer can pass their emissions tests.

It is sometimes necessary to disable this to correct the mixture when you set up a PC as the fuel injection will continually try and adjust the ratio back to optimal for the catalytic converter, not the bike.

[vifferman]

Kawasaki use a throttle position indicator as opposed to an airflow meter so the dyno thing is required, I'm not sure if that applies to all injected bikes but definitely an issue for the ZX12 also

That's kind of right... although on the Honda at least, there is a MAP sensor.

The problem with bikes is that the negative pressure in the intake manifold can't be measured accurately when the throttle is wide open, because of the multiple throttle bodies/intakes and the large valve overlap of the engine. Conversely, using just the throttle position sensor doesn't work too well at very small throttle openings. So, (on the VFR at least), the computer uses two different kinds of maps - one for the MAP sensor, and one for the throttle position.
The VFR is also a bit tricky in that the V4 configuration means there are differences in cooling, fuel requirements, so it uses 8 different maps altogether - 2 for each cylinder. The ECU reads data from 9 sensors then determines the fueling from reading the appropriate map's data. If the O2 sensors aren't disabled, it uses those at low revs/small throttle openings (in 'closed loop') mode to determine the fueling directly from the EGO levels. The trouble is, the ECU is set ultra-lean to satisfy Euro3/4/5 limits, so the bike ends up with a lean surge, and an awkward hesitation as it switches from 'closed loop' to mapped mode.

You don't necessarily have to get your bike dyno'd if you change the airfilter and/or zorst - it depends how much of a difference it makes. There are quite large margins built in to the fueling so the engines don't blow up if the owner changes anything. For anything but Harleys (no offence intended, HD owners), the engine is pretty much optimally tuned already, so aftermarket airfilters and zorsts don't actually improve 'breathing' much anyway. If your bike has O2 sensors, then the low revs/small throttle fueling is taken care of already.

However, apart from potentially mental fueling in 'closed loop' there's also usually a mid-range dip built in because the emissions testing (noise and exhaust) is carried out at fairly specific revs, so the manufacturers do stuff to cater for this, so the engine gives the appearance of saving the whales and cooling the planet, but only if you don't look past that sweet spot. If you go for aftermarket ECU-fiddling mods in conjunction with dyno-tuning, you can often get rid of this annoying mid-range dip (subject to mechanical constraints, such as cam profiles). That's a big advantage.

[degrom]

My other question was about Ram Air-Intakes..

How will it effect the bike if you build a Ram Air-Intake for it?
(It will definitely take away the negative pressure in the intake manifold)

[craigs288]

My brother put a different exhaust on his XT and that is injected but only runs off the TPS. Him and his friend stuck the gas sniffer up the pipe. I can't remember if it was leaner or richer, but they adjusted the TPS position until the exhaust was similar to the original setup.

[Pancakes]

My brother put a different exhaust on his XT and that is injected but only runs off the TPS. Him and his friend stuck the gas sniffer up the pipe. I can't remember if it was leaner or richer, but they adjusted the TPS position until the exhaust was similar to the original setup.

The TPS will be one axis and revs normally the other. Messing with the TPS is a pretty brutal way of fixing fuelling. If it worked it was just by chance that that system happened to be ok with it. Fuelling isn't linear so you can't really just raise or lower the sensor to enrich or lean out the motor and be confident it will work.

[imdying]

It's a typically Kiwi bodge

[Pancakes]

It's a typically Kiwi bodge

Yeah until it dies then "that Jap stuff's shit ay bro?"

It's liek when people ask what to do to mod their S2000 (Honda car) and it's the most powerful car/L ever! Methinks smarter people have already had a go at making them fast before they were even built?

[The Stranger:Me]

Methinks smarter people have already had a go at making them fast before they were even built?

Maybe they are smarter people, but there is no doubt that some smart people can obtain decent improvements with very little work.
Just in the process of tweaking the Fazer now. I have 10hp more out of it and know from others that it is easy enough to get another 10. Don't really need it but hey it's not hard to gut the cat and install smaller sub throttle plates.

[imdying]

Yeah until it dies then "that Jap stuff's shit ay bro?"

It's liek when people ask what to do to mod their S2000 (Honda car) and it's the most powerful car/L ever! Methinks smarter people have already had a go at making them fast before they were even built?

Yeah mate, doesn't even have to die though... rough idle (doesn't no it's idling so doesn't use the idle map), heavy gas consumption, flat spots, vibration, all potential results from a misadjusted TPS. To each their own though, but you won't catch me doing it.