bike carbs on xe16

[aaronc190]

could i just plug out all the ecu bits apart from the one for the spark pugs? and put bike carbs on the engine??:confused: :confused: ...

[meritlover]

yes.....

but dont expect it to run well.

you still need almost the same sensors/ecu inputs to run correct ignition as you do the injectors.

youl likely end up making more power and better fuel consumption with the OE injection system if you try that.

[aaronc190]

could i not just set up the carbs(jets,pressure,etc) and disconnect plugs that are not needed??

only need a spark...

[meritlover]

ok then if you want.:roll:

yes all you need is a spark. but it matters at what point it occurs at....and the only way the ECU knows what point this is, is to have all the necessary inputs from the engine. if it doesnt happen at the right time...the performance will be rubbish, and you could well damage the internals.

when switching to carbs, the only thing the engine doesnt need is the injector plugs, which you'll be removing anyway and the Idle control valve. yes you could remove a lot of others like purge valve and egr, but the ECU will show an error, illuminate the MIL and probably set some weak 'limp-mode' value for the ignition anyway to make the car run like a 2 legged dog.
which goes back to my previous point, that it will likely be better running the OE management.
you will also melt the cat' and your lambda sensor. which will also screw up the timing.

[aaronc190]

whats the best cheap system to do the timing?

[meritlover]

best and cheap arent really two words you could use together to choose a management system.

some sort of 3D management would be ideal, like Mega-Jolt.
something that uses TPS,RPM,CTS would probably be enough to get it running fairly well. dont use MAP as the vacuum change will be too great for a given throttle input and will cause it to hunt. and with no plenum it will probably have a lumpy signal from the intake valves anyway.
youl have to make sure you fit a TPS to the carb spindle though and calibrate it to the ECU. or you will only have a flat 2D system.

youl probably have to spend some time/money getting it mapped too.

[Adam]

Megajolt can do it for around £150.

You can use the std ecu yes but it will be running in limp mode, with fook all advance, and probably be slower than the std engine.

[aaronc190]

could i by pass the limp mode?

[Adam]

No

And its mapped completely wrong for a bike carb'd engine.

[meritlover]

totally,
and its probably totally useless anyway. as if your using CV bike carbs, the throttle input might be 100% but the slides wont open until the vaccuum conditions suit, so your getting the wrong timing as the ecu thinks your getting maximum cylinder filling...when your deffinately not!

[Stuart]

you can use MAP on the small plenums, but you need to have a good ECU strategy that lets you pick where in terms of crank rotation you sample the MAP sensor so that you are at the bottom of the intake pressure trough ;)

How about mr Arron, you just ignore us, fit the ecu and find it runs gash.... would you then believe us? lol

[meritlover]

you can use MAP on the small plenums, but you need to have a good ECU strategy that lets you pick where in terms of crank rotation you sample the MAP sensor so that you are at the bottom of the intake pressure trough ;)



higher up the RPMs the pulses will smoothen out anyway and if youve got lairy cams that are causing you idle problems, your probably only worried about the high RPM/load performance anyway.
easier to employ a 'timing-lock' function to come it at say 1500-800 rpm and fix the timing at 12 deg BTDC ofr example to hide a lumpy idle. cylinder filling will be poor due to pressure pulsing anyway, but no amount of clever MAP sensing will make up for the fact that theres hardly any air in the cylinders, so at least a fixed advance will stop the timing dancing round the load sites at idle.
fueling can be fixed round those sites too, and the idle valve can be used to control the speed (even if it is working harder than it normally would)

[Adam]

How youd get the std idle valve into a bike carb setup though, would be quite a task.....

[Stuart]

at near WOT (and revs) the MAP should be as close to 1bar as possible ;) so looking for the trough is irrelevant there.

I'd do the bulk of Idle control with spark (ie chuck fcuk loads in) and then a tweak of air and fuel as they act far slower

[meritlover]

sometimes we do it that way, but you often need lots of advance to compensate for poor filling, but you still have the problem of the map dancing due to pulses....hence why the ICV is used as well.

all depends on the setup, but i dont know why youd want to run a small plenum with bumpy cams anyway....so this discussion is pretty pointless.lol

[meritlover]

How youd get the std idle valve into a bike carb setup though, would be quite a task.....

you are correct, but we're talking about plenums,

[Stuart]

ITB's/Individual cars are small plenum ;)

[meritlover]

small runners, its not really a plenum of 'free air' its just a means of connecting the ITBs to the head. which is inevitable.

[aaronc190]

sound i was just wondering wat would happin anyway if i did try it...