patrick
Hello
A few years ago, I swapped a S4r fuel ramp on my 851 90 , and clearly it runs smoothly, responds better and iddle very properly ( + heavier valve springs)
The new injector jet type (flow the same) and the airbleed helps for sure.
But it tends to run too rich.
I precise i already slighly lean the fuel map, in the range 2000/4500and 1/7degree to make it run smoother again.
Before having a look on other parameters, i realize that i don't have anymore the vacuum-down tubes connected to the old regulator with this new ramp (and the new regulator) witch normally downs the pressure to 2,5 bar instead 3 bar when you cut the rev.
Do you think it has got influence and should i lean again due to that?
Playing with the trimmer screw could help, but if i lean with it , it staal on iddle when very hot at town lights ( the air temp tranducer is always into the airbox, something i have to modify too)
Many thanks for your knowledge
Patrick
griff851
In a word. Yes. If the injector run time is x, (the time the injector port is open.), then the only way to increase the volume it allows through, is to change pressure either before or after the injector port. By changing the time the injector is open is mapping. Changing the pressure after the injector is cylinder head porting etc. You must therefore re time the injector for the fuel pressure you have to get the best possible burn (hence power) at a given rpm. Trim screw allows for variation in the given regulated pressure to a degree. Increase the fuel pressure too much, and you are out side the trim range and must re-map to bring the trim into a usable range. It is usually a + or - over the whole map. I think it goes something like that. Hope that helps.
An example. If at 11000 the cylinders lean out, but i want it to go to 13000. I have to either put bigger better or more injectors in. I can not change the time the injector is open because the piston isnt hanging around long enough. So i have to increase fuel pressure. Then however the lower rev ranges will be too rich, so a new map would have to be made.
patrick
Hi Griff
i havent see yet your answer, thanks
right, so in theory I'd lean it to the equivalent of the fuel pressure vaccuum drop difference, so 0,5 bar.
witch was 0,5/3= 16% leaner ( in pressure)
but how much in injection time into the fuel map i have to compensate?
I have in head, for a car engine tuning, increase the pressure of 50% means 22% richer.
taking that, a 16% in drop pressure, 'd mean 7% leaner; am i right?
To take no risk i can try in the low/cruising area first, because i don't have co or dyno machine , unfortunetely...
Opinions welcome!
patrick
patrick
Not other opinions or advices ?
Thanks
patrick
ps. i 've found this to check mixture, somebody knows?
http://www.gunson.co.uk/item.aspx?item=1835
BARONROJO
Yes! It has a desperately slow response. A kind oh nightmare to use.
patrick
Ok, i red some comments on it, need time to do the calibration properly and well respect the procedure.
but it costs (only) 140 and the measurement is apparently reliable.
patrick
Hello
Continuing my investigation on the fuel mixture setting,
here is a picture of the spark plugs after 150 km of cruising
Left is the vert. cyl. , it appears a little bit richer than the horiz. but globally twice are not so rich as it was expected.
the horiz. shows a more "red" colour ( i presume it comes from the additives inside the unlead fuel)
However, pipes show a black carbon deposite...
griff851
Is the vert cylinder black like velvet or more oily? Because to my looking on my phone, either the rear is rich (velvet), or you've got a valve guide seal on the way out. The front is a tad lean for cruising. Our fuel leave tan rather than pink. You look at the insulator on the center electrode for fueling clues, the base of the top electrode tells you timing.
patrick
The Vert . richer is velvet (fortunetely) - valve guide seals are quite young.
I did the timing a few years ago, + 10 degrees on the vertical to go to the std spec.
the horiz perhaps would need a few degrees (2/3) according to my measurements but i left like this.
Next week i will recieve my Gunson gastester
i will do a complete procedure, and i should balance again the throttle bodies but at mid revs,
as i have now airbleeds screws for iddle setting
have a nice sunday
patrick
griff851
Sorry, left out ignition in front of "timing".
patrick
Hi Griff
Hei ok, i understood "cam timing"
do you mean " ignition advance" or quality ( poor or good) of ignition ?
ps. To write english, that runs just about, but to well understand it's another challenge for me
griff851
You are doing fine in the english deptment and being Australian we really know how to butcher English. 😁
Because advancing and retarding as well as strengh of spark effect the burn, it shows up around the bottom of the top electrode. Just think of the plug gap as the center of ignition. The fuel air around the lower electrode is relatively stable and not moving much, so it indicates whether your rich or lean. However just outside this zone the turbulant flame front has started, so at the bottom of the top electrode tells you how the burn is going in terms of efficiency which is dictated by the ignition timing relative to the pistons position.
griff851
I learnt all this a while back by watching Bob deal with a 74 GT 750. He started with how much spark he needed and stuck on the appropiate coils, bearing in mind there are not that many amps to play with on the old machines. Then tuned it. It went for 500km and when we checked the plugs they looked still new, with an ever so small hint of deposit. Nice. Which means the bike fuel economy was pretty much at maximum.
So you will need to stick on a set of vacuum gauges and get them throttle bodies balanced. When balance properly you will note that they both dont have exactly the same vacuum. You can hear the differance in the exhaust note between equal and not equal. One is definately sweeter.
The reason why. We sumised its due to the 270 degree firing order, one cylinder works harder than the other, due to the inertia of the crank.
patrick
Good, many thanks for these precious infos
next week , i wiil begin to play and start with proper plugs too.
the timing actually is 121/112 rear and 119/113 front for a spec of 119/112
Was 131/102 rear originally like many bikes!
I am not sure i changed the plugs since...
i will let you know for sure
best
patrick
