Here i go again ..

[garry55]

thats the one - thanks !
I'll bookmark it now

[garry55]

having read shed-loads on this subject (it was going to be ANOTHER project ), I would just like to post my all-time favourite quote, the reason why I shelved the idea....................

"Don't work so well on motors that use a lot of harmonic wave interaction as all the pulsing and reverse flows really mess with the sensors. Don't get me wrong, it can be done, but mapping a motor who's rev range covers several harmonic ranges is a proper PITA - usually can get 1 harmonic range to fuel just lovely, it's the others that'll be the issue.
Processing power has moved on greatly, but it's still difficult to cater for a motor that can 10 fold increase it's fueling demands in a 1000rpm step. "

Prove me wrong, Dave !

then sell me a working system for my V4..................

[Suzukidave]

We are lucky enough to have a list member with a working FI already setup on his GT750 viewtopic.php?f=21&t=9565" onclick="window.open(this.href);return false; .. his last hurdle seems to be adapting a charging system that has more output to cover the loads of the new systems .

[garry55]

I'll settle down and read that tonight at work - cheers Dave

[tz375]

having read shed-loads on this subject (it was going to be ANOTHER project ), I would just like to post my all-time favourite quote, the reason why I shelved the idea....................

"Don't work so well on motors that use a lot of harmonic wave interaction as all the pulsing and reverse flows really mess with the sensors. Don't get me wrong, it can be done, but mapping a motor who's rev range covers several harmonic ranges is a proper PITA - usually can get 1 harmonic range to fuel just lovely, it's the others that'll be the issue.
Processing power has moved on greatly, but it's still difficult to cater for a motor that can 10 fold increase it's fueling demands in a 1000rpm step. "

............

Cool quote but what does it mean in relation to EFI? It suggests that fueling requirements change as a result of harmonics which makes some sense in as much as in a steady state, airflow will change from one state to another with changing harmonics and a two stroke lives by harmonics or at least by pressure waves. So is it suggesting that the real issue is that airflow changes so much that it's hard to adjust for it? In which case, how does a simple carb cope with those variations?

I would have thought a bigger issue was the duty cycle from low load to high load and the fact that on a large 2 stroke the fuel demand is so large at the top and so low at the bottom that it probably needs twin injectors to cope. Small flow injectors would be OK at low load and would exceed 100% duty cycle at higher loads and large injectors for the top end would not react fast enough at low loads, requiring twin injectors to cover the range.

My head hurts again......

[garry55]

thats the very reason it's my favourite quote - I don't understand it
which made me realise I shouldn't start messing with things I know very little about.

[Suzukidave]

The thought we went with the R1 ( 1000cc) throttle bodies w CV and the larger injectors would cover the fuel demands of the 750cc engine but the problem we are thinking could be encountered is the injectors with the MS system i have need to fire in batch so they squirt 3 times each rev and that may reach the limit of the injectors at close to stock red line . It would be so nice if i had a seq setup

[garry55]

I would have thought a bigger issue was the duty cycle from low load to high load and the fact that on a large 2 stroke the fuel demand is so large at the top and so low at the bottom that it probably needs twin injectors to cope. Small flow injectors would be OK at low load and would exceed 100% duty cycle at higher loads and large injectors for the top end would not react fast enough at low loads, requiring twin injectors to cover the range.

so how does a simple carb cope with those variations?

The favoured trick for ensuring the smooth running of my twin-injector-per-cylinder Ducati 996 motor is to disconnect 2 of the 4 injectors..................

[ja-moo]

Sometimes, going backward can move you forward. Get that baby going with carbs, see how she runs, and work out the EFI later.

And my take on the "quote" is the sensors are taking a reading of what's flowing over them, if it's going back and forth, I don't think it has enough time to "read" what is going on, or things are changing faster than it can collect data.......

[tz375]

You could be right John, but in any two stroke or 4 stroke there are multiple pulses (waves) in the inlets and exhaust tracts. 2 stroke waves are stronger and maybe if a sensor is too fast to respond it may have issues with 4 or 5 complete waves per engine cycle. Admittedly the first wave is the strongest, but sensor response time or sensitivity may be an issue.

I like the idea of running it on carbs first to get all the chassis and related issues fine tuned and then switch over to EFI. It would be nice if Dave had access to a dyno with fuel measurements as well as exhaust gas analysis like the DynoTechResearch guys do on sleds. That way he could get the baseline set up on carbs and know the fuel flows at different parts of the RPM-Load (TPS) "map" to use to set up the injector tables.

[ja-moo]

Just taking an educated guess. Plus there are twice as many power pulses than a 4 stroke, and depending on how well the pipes work, there is fresh mixture up to a foot into the pipe, that would be very "confusing" to a sensor most likely made for a 4 stroke.......

[Suzukidave]

Which sensor are we talking about here ?

[tz375]

Good question Dave. No Mass Airflow Sensor, so that's not an issue. Temperature sensors are not affected. TPS is not an issue either. MAP Manifold pressure sensor - that one would potentially be all over the map That would be a problem if you were using automotive style Speed_load tables, but not if you use a straight Alpha-n table. There's another option and that's Alpha-N hybrid that factors in MAP, but I'd go with Alpha-n and pressure fluctuations would not make any difference.

[Suzukidave]

I sent what was said to my son who was to be my tuner and his reply " I was already planning on using a hybrid alpha-n with a map at high load, only going pure alpha-n if it didn't work right. Far as I'm concerned, MAF would be the way to go, just no way to implement it without ditching the whole induction and airbox setup we have now. The o2 sensor would be very short lived. Everything else is normal operating conditions."

[Suzukidave]

Today i got in the mail step 1 in doing a step backwards .. a stock GT750 wiring harness .. now to strip off the miles of FI harness . Nice thing will be the R & R from Oregon Electrical will plug right in