How have you solved this??
corpi - 28/6/09 at 07:18 PM
I've got the engine running quite well now, needs some more tuning but that is a matter of time.
engine is a XE with GXRS750 throttle bodies. and MSn Extra 2.0.1
My only problem that i don't think I kan solve just mij tuning MS. is the fact that it is very difficult to subtly crack open the throttle. I
realize that this is (partly??) caused by the fact that the angle of the throttle disk to the throttle barrel is almost perpendicular (sp?). But it
also seems that it takes more effort to get it moving, that it takes once it's moving, (I hope this makes sense) almost as if the low pressure in
the inlet it keeping it closed, and once there is a slight movement the vacuum in gone and it's much easier to open further. so instead of
opening the throttle enough to to idle a few hundred revs higher it goes up 1000 rpm. which makes it a pain to drive, subtly, in a traffic jam as
today proved... or even potter off gently from a traffic light...
Has anybody solved this? I'm using the standard throttle cable arrangement as fitted to the thottle bodies. Which already is a progressive
arrangement.
Ideas??
paulf - 28/6/09 at 07:39 PM
I have the same problem with mine at present, I was running on speed density without the problem but was having problems with larger throttle
openings.I changed to alpha n and solved the problems with fast driving but now have the problem when driving in traffic.
I wish I had kept the auxillary buterflys which i removed as i fancy experimenting with using them at low revs.
Paul.
corpi - 28/6/09 at 07:51 PM
Mine did not have the secondary butterflys (thanks for the name for them, I could not think of it... age :-( )
possibly something like the fast idle mechanism being activated first and when that is fully operational use the main throttle cable, but how to
connect it all..... in a reliable way!
flak monkey - 28/6/09 at 08:10 PM
There was an interesting solution to this common problem with bike throttle bodies posted a week or so ago by fatbaldbloke.
The issue lies in the angle of the throttle plates at and close to idle, meaning that just off idle a very small throttle opening lets in a lot more
air.
However if you can have the butterflies open enough at idle (i.e. past the problem point) you can overcome it.
The way, apparently, is to reduce the amount of advance at idle, meaning you need a larger throttle opening for the same RPM. Then change the advance
bin just off idle to a higher value. The problem this causes is that you will have to run a slightly richer idle (13 ish AFR), but the advantage is
that you will get better off idle performance.
David
corpi - 28/6/09 at 08:54 PM
Cheers David!
I'll try that. I stopped following that thread as I thought it was refferring to issues at higher RPM's
paulf - 28/6/09 at 09:06 PM
I tried it but didnt have much success as the idle wouldnt drop sufficently to allow the butterflys to be opened further.
Post on here how you get on.
Paul.
quote:
Originally posted by corpi
Cheers David!
I'll try that. I stopped following that thread as I thought it was refferring to issues at higher RPM's
fatbaldbloke - 28/6/09 at 09:44 PM
A few tips to try. Firstly, if I may be so bold, forget speed density, relatively high revving small engines need AlphaN. Next, you need to put in
some rows near idle so you can get a smooth transition from cell to cell with a little throttle movement. So, for example, if the idle tps value is
57, and full throttle is say 220 (typical values for GSXR tps) have the bottom row at 57, then the next at 60, and the one above that at 65 and so
on. You need a lot more resolution at the light throttle end than at full throttle. Same sort of row distribution with the ignition map as well.
Now, what I did to sort out the fuel and ignition around idle was create a map purely for testing, with rows at 56,56,58,59, 60 and so on, and rev
columns at 700, 800, 900, etc. So, it's not driveable but you can play with the values to get a decent idle and throttle blip. Once you've
done this you can pick rows and columns to put in the real map that are suitable spaced.
So, whilst I did recommend one solution as retarding the ignition to reduce the throttle, you also need to get the fuelling spot on as well. The
solution is a combination of lots of things around idle. Also, you'll need good flow balancing between the throttle bodies, as this will throw
the idle out as well.
Does that give a few more ideas?
Good luck.
FBB
corpi - 29/6/09 at 07:04 AM
Thanks FBB,
I tried Speed density and am now trying AlphaN which is so far much better, except it seems to exagerate this problem.
But is have to fix an electrical issue first! On the way to work 3 times all electrics died a second or 2, alternator light glowed, however i had
enough speed to continue. Then idling. in the carpark, just before i switched off it died again, and would not start, (starer does nothing, no
lights. emergency lights flikker at a high frequency and there is a sound like a relay opening and closing rapidly. some things, wiper washer work.
marker lights work, the dipped lights gives the relays sound again switch the light off and on again a couple of times and fiddle around with the
ignition switch the lights switch and a few others, and suddenly the lights work again, as does everything else... including the engine.
no fuses blow, Nothing is wired without a fuse. Lights and emergency flasher are on different fuses.
very weird.... if I get home.... it will mean an evening upside down under the dash :-(
[Edited on 29/6/09 by corpi]
[Edited on 29/6/09 by corpi]
fatbaldbloke - 29/6/09 at 08:15 AM
quote:
I tried Speed density and am now trying AlphaN which is so far much better, except it seems to exagerate this problem.
This gets a bit tricky, but here goes....the shape of an AlphaN map is very different from a Speed Density map. At low rpm, say 1250, you can flow
the maximum amount of air that the engine requires at quite a low throttle opening, maybe only a quarter of the available movement of the butterfly.
What this means is that if you open the throttle further no more air actually flows as the engine is getting all it can handle anyway. What this
means to the map is that you will increase the fuelling value (VE value) from the bottom row, and up a couple of rows, but you then get to a point
where regardless of increasing throttle position you don't want any more fuel. So, the working part of the fuel map is largely triangular. with
the upper left hand corner doing nothing. What this means is you need to shift the distribution of row values so you have more at lower tps and fewer
at the higher tps values.
You can see the effect on a datalog if you look at the manifold pressure and throttle position at no load. Just slowly increase the throttle and
you'll see the MAP value go from about 50 kPa up to a maximum, around 98 kPa, with little throttle movement. At the point the MAP ceases to
increase with further throttle increase you have reached the value where you are not increasing air flow any further irrespective of how much throttle
you give it.
Does that make any sense...you need to almost throw away any progress you made with Speed Density and start again as the VE table works in a
completely different way.
corpi - 29/6/09 at 09:37 AM
I'm using MSnE2 so i have % throttle opening. Makes no real difference, but should I start with 1%, 2%, 3%, 5%, 7%, 10%, 15% and then in biger
steps? Or even higher resolution it the first couple of steps? I don't know if decmals are accepted.
fatbaldbloke - 29/6/09 at 12:44 PM
I'm using an MS1 which has 12 rows available. Converting my ADC values into percentages gives rows something like 0, 2, 4, 6, 8, 11, 14, 17, 21,
33, 50, 75, 100.
For speed I'm using 500, 1000, 1500, 2000, 2300, 2600, 3000, 3500, 4000, 4500, 5500, 7000.
corpi - 29/6/09 at 08:31 PM
While looking for the elctrical gremlin tonight i left the engine idling to see if I could reproduce the sudden death syndrome. No luck.... it kept
working perfectly :-(
I tried setting it op the way you said FBB. and it seems to work, I gave the idle screw one turn out, and then tried to get it idling at about 900
RPM, I had to go to 3 degrees advance to get it to 1000-1100 RPM fidling with the VE to get Air/fuel about 14.0 anything else and it wouldn't
idle properly.
TPS are 0, 2, 4, percent and RPM 700, 800, 1000
I kept the 3 degrees up to about 3000 RPM at 0% TPS. What I find is that it takes quite long to slow down to idle after blipping the throttle.
The GOOD news is that pick up on blipping the throttle is much better. and it looks like you can gently open the throttle now. I did not actually
drive though, except for 2 yards back and forth.
The princpile seems sound no now for the fine tuning :-)
I've had enough Exhaust fumes for one night... Garage doors where wide open but what little wind there was blew into the garage...
Thanks everybody Especially FBB for putting me on the right track!!