Fuel Injection Compensator - 1200 spo

I’m liking the idea of one of these ‘plug and play’ compensators to hopefully reduce the small backfires on low throttle openings on my 1200 sport and to smooth out power delivery throughout the rev range.

Has anyone fitted one of these and what benefits/changes have you noticed?

They are quite expensive for me so any info would be much appreciated before I take the plunge

the one on my breva 1100 smoothed out the throttle at low revs, but it still pops and bangs, wouldn’t want to fix that though,

I suspect its drawing a little air in one of the exhaust joints, and getting a small explosion in the pipe, any compensator that adds fuel to smooth things out ain’t going to fix that, only potentially make it worse,

mine has a pretty open pipe and sounds like a lancaster bomber, not to loud though!

Thanks for that. I guess I’m trying to balance the scales of benefit and cost.

After having had one on your Breva would you buy another if you had a new different F Inj bike?

Surely that would depend on what bike and what it was like in the first place. Do a forum search as this has been discussed several times.

Sure, thanks Brian

By the way, reducing the slack in the trottle cable helps to improve the smoothness. Well it did on my Norge, and others have agreed. Not sure why, possibly to do with overcompensating for the slack.
Won’t affect the popping though. But I find on the Norge this only happens on the overrun when the throttle is completely closed. If you roll it back to the point where it is just a crack open, the popping stops.
I also know one member here who made his own compensator.
Brian UK2014-01-14 09:42:58

Twas I. Fitted it to my Norge with a beneficial outcome. Still pops on overrun a tad but much smoother through the lower throttle range. Will be keeping it on. Could send one for someone to try if they pm me.

Llamaman, are taking about a FatDuc, or similar oxygen sensor modification? I made up my own. It was inexpensive to do, but took some time. See here: http://www.flickr.com/photos/sign216/sets/72157629649665070/

That just using a single diode to drop the voltage?

Yes, a single diode. FatDuc uses a viable resistor, but a diode lessens the voltage without diminishing the current.There are oxygen sensor mods with more complicated circuits, but I kept it simple.

Silicon or germanium diode? I would have thought the voltage drop with a silicon diode being 0.6v would have been too much.

Silicon, I believe. Germanium has been replaced for nearly all diode use. I use Schottky diodes which have
only a 0.15 to 0.4 voltage drop, and this just right to reduce the O2
sensor’s voltage. The diodes that have worked for me; SB3H90, IN5820, BAT48, and similar
diodes with a forward voltage loss of 0.15 to 0.35 volts

Makes more sense, thanks.

Many thanks guys, it’s amazes me how much information, talent and resourcefulness exists on this forum

PM’s sent

Just for general interest on this subject here’s my reply from the pm. Well it can be that simple but there may be a problem oversimplifying it. The output of the lambda sensor switches from 0V to about 0.6V when it has warmed up. The injection control then switches from open loop to closed loop to determine the injection time. The mixture is set initially very weak to meet emission laws so it’s only necessary to fool the system into thinking it’s running a little too weak. The input impedance of the control circuit is very high which means that any resistor placed in series would have to be a high value to have any effect. This in turn means that changes in temperature would affect the amount the input voltage is reduced as resistors are normally thermally unstable.
I have found that the answer is to reduce the input impedance by fitting a resistor in parallel and then using a series resistor made of one fixed and one variable resistor. This gives a reasonable adjustment range to allow you to vary the mixture during the closed loop operation and avoid to some extent the fault warning coming on too long. A simple diode would give a fixed voltage drop and maybe the mixture could be too rich then. If the injection pulse width is monitored using a computer connected to the ECU the changes can be seen. Under practical conditions the unit would be fitted and the adjustment made with test runs.
The fatduc I think works this way but I cannot imagine
how the other system can be any different. The fatduc seems to be a reasonable price but I have my doubts about another much more expensive one.
Incidentally, I was always of the belief that Schottky diodes only attained their low forward voltage drop at currents exceeding about 1mA which in this case would be far too high as the input impedance is somewhere around 700K. Of course I could be mistaken.petethebee2014-01-21 11:55:06

Where did that come from? I bet many resistor manufacturers would like to disagree. If it's that much of a prob use high tolerance ones or even instrumentation types. 1% metal film would be quite adequate, if you want to be really fussy there are 0.1% I believe. In any case that's only about the accuracy of the basic value i.e. manufacturing tolerance. IIRC heat would increase a resistor's value slightly, but I'm sure the effect would be miniscule.

When visiting my link, double-click on each photo to open them up. Below each is a comment section where the real information is.Petethebee, nice data. I think FatDuc really is just a simple variable resistor. Schotkky diodes worked for me, but I’m a simpleton. I use plug chops to check the mixture. Resistors in parallel hold promise, but I had a hard time getting data on the current produced by the O2 sensor, to calculate resistor values. Diodes are a simple answer to provide the voltage drop. I am eager to hear what you find out.

Yes MikeH you’re quite right. It was a passing thought I should have let pass.
Sign216 I think you’ve misread me. petethebee2014-01-21 13:33:37

54 pence, might be able to afford that.http://www.maplin.co.uk/p/3a-schottky-barrier-rectifiers-n91ca Nothing to stop anyone just soldering it into the Lambda wire, save the cost of the connectors.
Brian UK2014-01-21 14:31:46