907ie misfire - maybe a cure???

[Laddie]

I'd have to take the bike apart to take a pic - but I'll explain...


the MAP sensor is the air pressure sensor on the outside of the air box. [not to be confused with the ATS -air temp sensor]
The Prt03 map sensor is held on the box by three points. It looks like this:
http://www.zetecinside.com/xr2/pictures ... manual.pdf

there is a short hose that comes from the air box to the PRT03 MAP sensor. The hose is what needs to be damped - NOT PLUGGED. A ciggie butt pushed in tight will work OK.
You still need some air flow - but just restrict it enough so it's hard to push air through.

a quick side note to this is that the only EFI models that use the manifold pressure are the 907, 851 and 888. All the others Ducatis after these the air pressure used in the map is only ambient. maybe Ducati worked out the difficulties with monitoring the manifold pressure on a big vee twin - particularly at low RPM. The 851 and 888 are more "performance" than touring - so it's unlikely they encountered the same low RPM issues.

The idea is to take the intake stroke vacuum pulse out of the line...the air box vacuum will still get to the sensor - just the instantaneous variations will not be present. It is possible using a longer hose will work or even using a small tight aperture...the ciggie butt worked for me.

Please let us know how it works for you...

I'm sorry it doesn't cost more - you can send me $230.00 if it makes you feel better...

[Tamburinifan]

Perfect thread f learning ie, newbie as I am. Thx, Laddie!

The idea is to take the intake stroke vacuum pulse out of the line...the air box vacuum will still get to the sensor - just the instantaneous variations will not be present. It is possible using a longer hose will work or even using a small tight aperture...the ciggie butt worked for me.

So why not let the 907 MAP sensor take ambient air like later Ducs if the fluctuations in pressure are what mess things up? You tried?

[Laddie]

hmmm...wht not use atmospheric???
You should ask Ducati that...

well, the manifold vacuum is BIG variations in pressure / vacuum compared to atmospheric fluctuations. Automotively speaking it's fairly common to use engine vacuum for (say) spark advance and fuel control - particularly for acceleration purposes. Only probably the last 30-40 years that atmospheric pressure has been used for accurate fuel adjustments.

It seems on the 907 that the TPS controls both spark advance and fuel for instant acceleration. There may be some use of the vacuum for spark advance but this isn't apparent with the blocked MAP sensor tube. I'd need to review the ECU map and algorithm to see how vacuum affected the advance (if at all).

In the over all scheme of fuel injection it has been common to use EFI systems with turbo chargers - this definately DOES require the manifold pressure to be monitored and in these cases the MAP sensor will be up to 2 bar pressure monitoring range. You might find the Weber-Marelli system is just another continuation of these systems. I dunno - I just work with what's there...

as far as I can determine it might be possible to just use ats rather than manifold pressure but this would probably require a modification to the sensitivity of the air pressure sensor.
to use atmospheric would require the complete ECU map chip to be re-written to those values..which are significantly different to manifold.

It would probably be easier to use a later model system like a 916 or similar but this would need modifications to the pick up sensors on the crank.

we are starting to get to the WOFTAM scale there.
Waste Of Fucking Time And Money.

[Tamburinifan]

OK, just asking, newbie as I am.

[Tamburinifan]

WOFTAM scale or not, I`m testing the butt thing tomorrow.

I am NOT willing to accept that the basically same engine as in my Monster work function properly in 4th at 70km/h around/below 3k RPM. Period.

Only difference is liquid cooling (a +) & the injection (the bad guy?).

[Tamburinifan]

200 km butt test trip today.
Small but significant improvement! In 3rd at 50km/h, 4th 70km/h,
not perfect but better, not stumbling to pieces. Noticeable better rideability around 3000 RPM.

I have original exhaust, original airbox & lid w KN filter and FIMchip,
14/39 gearing.

Your on to something, Laddie!

[Laddie]

OK - maybe we're on the right track...

now check your vacuum balance between cylinders on the throttle bodies at 3,000 rpm. I hope you have 2 x guages for this - and check they are matched, [connect both to a single tee fitting and make sure they read the same through the range] just to be sure.

the instructions only tell the mechanic to set the bike up (and TPS, too) with the throttles FULLY shut (then adjust to idle)

I suggest that you balance the throttle vaccum for both cylinders at 3,000 and check a few other RPMs, too - say 4,500 and 6,000 (but look for BEST balance depending on how hard you ride and what engine speed you most commonly use)

re-set the idle balance (if necessary) with the air bleed screws

I found that with the air bleeds fully shut and the throttles both set at FULLY shut (then after adjusted up to idle with the idle screw) that at 4,000 RPM I had a significant (10%+) imbalance between the cylinders...it doesn't make much sense but that's what I found.
I re-balanced at 4,000 and re-set the idle balance with the air bleeds (isn't that what they're for?).

the bike did run better after I did this BUT the misfire was still there occasionally...the ciggie butt was a later addition.
I don't generally ride at 3,000 RPM (I think the engine is laboring too slow at that speed - particularly in the higher gears).

make sure the ciggie butt filter is quite tight in the tube - it should be very hard to blow or suck any air thru - but do not block it off completely.

[Ducman]

How were the injectors? The filter wouldn't stop all the shit from the tank. Sounds like they (the 907's) run lean in cruise mode. The fuel injection in them is pretty stoneage by today's standard. I have a new ST3 that hiccups now and then the wrench told me the Euro 3 specs have the engine leaned out. I don't usually run the 907 much below 4 grand as it seems to be happier closer to 4.

[Laddie]

I haven't had the exhaust gas analized lately but both are a nice darkish tan colour at the moment - so i expect I'm not too far off the right mix for my riding...the vaccum and mix balance is real good - not one backfire or fart even under 7,000 RPM down to idle deceleration.

The exhausts have been soot-black when we tweaked the ECU trim up and also when I played with TPS settings...as you do...

as for the injectors, my new tank is clean as possible - no rust at all...
I would recommend to occasionally check the V point in the side floor of the tank - both sides. (this is the V at the intersection of the tank, front and rear fairing).
This is an obvious corrosion point and a lot of shit [and any water] collects there. The original tank I had rusted through at that point - both sides. If you see any bubbling in the paintwork at this point you're in for some problems...

I highly recommend that part-time riders add isopropyl alcohol (or metho) to the tank once in a while to disperse / burn off any collected water / condensation in the fuel. For long term storage it would be better to drain the tank. I lined my other tank with epoxy resin [Megapoxy] - it will never rust out now....

I will make a separate post on tank corrosion and repairs...

the inline filter is original Duc
I have an ultra-fine cloth over the fuel pump, too - the wire gauze was a bit loose in my opinion.

If the injectors foul it will usually cause rough running at various rev. ranges - mainly higher revs where the engine starves for fuel when it needs it and "iffy" throttle response...but to run rough at 3,000 RPM (and down) is unlikely a blockage because the injector flow is pretty low at this speed.

[Tamburinifan]

If the injectors foul it will usually cause rough running at various rev. ranges - mainly higher revs where the engine starves for fuel when it needs it and "iffy" throttle response...but to run rough at 3,000 RPM (and down) is unlikely a blockage because the injector flow is pretty low at this speed.

Good to know, I was suspecting dirty injectors.

The exhausts have been soot-black when we tweaked the ECU trim up

That also affects mileage alot, I get 40-50km differences playing w that! Fiddling w/o proper analyzer...

I don't generally ride at 3,000 RPM (I think the engine is laboring too slow at that speed - particularly in the higher gears).

I agree, but it shouldn`t almost be stumbling to pieces at 2500-3000RPM in 3rd/4th gear!
As I said before, I see no reason besides malfunctioning injection
that this bike shouldn`t run as smooth as f e my -97 900 Monster.
Almost newer in 6th now w 14/39, I will probably try 14/41gearing.

[blakduc1]

All Good information. I am still finishing the service/valves and such on this bike and it is not ready to crank yet, but when it is I will be loking for a cig butt! ---- Would it make any difference if that tube was not hooked to the air box? Or if the top was off the box? I think someone said the best hp was gained from removing the snorkle intake tubes and leaving the air box top on. But anyway the problem evidently is not from being starved for air, but from pressure readings as you have said.

Thanks so much for all the input and explanation. ..And I like paying LOW bills for Duc work for a change...........

dp

[Laddie]

removing the snorkels will allow a bit more more air to pass more easily...
I anticipate it would have little effect at lower RPMs but would permit more air available to the engine at open throttle - but the airbox vacuum would be reduced when the throttles are cracked..

how this fits in with the fuel map (and any related spark advance settings) is anybody's guess. I had expected delayed throttle response by restricting the hose to the MAP sensor - I expected the MAP sensor would control spark advance and fuel...but it didn't make much difference,

I think we need to credit Ducati with some expertise with the air flow design and in writing the associated map.
Modifying the design [like removing snorkels] might make some HP difference but I think we need to consider that Ducati has to pass emission controls etc to be able to sell the bike - many after market modifications don't take responsibility for the emissions.

I'm sure if most guys could get a 10% HP increase but doubled to CO emissions that they'd still do it.

The MAP sensor just monitors the vacuum in the air box.
Taking the box top off, removing snorkels or removing the MAP sensor hose will just result in the bike thinking the engine manifold vacuum is at some higher pressure (or lower vacuum) than it actually is - or is set for in the ECU map design.

The bike will probably idle OK with the MAP hose off (must admit, I haven't tried) but the fuel mix will not be right at higher RPM or wide throttle openings.
How much this will be wrong I'm not sure...the TPS does a lot of the work for the ECU...

It would be helpful if Ducati or Ultimap or one of the after-market chip guys could explain how much the MAP sensor effects the algorithm.

You can try running with the MAP hose off - the hose can be re-fitted if you have small hands or an available kid you can get to do it. Let the bike cool down first - it's tight and twisty to get to.

[blakduc1]

Laddie, Is this MAP thing the blue thing on the back side of the airbox with the little hose going in it? That hose looks too small in diameter for a cig butt -- but I guess the but is compressible --did I say "butt" too many times?

dp

[Laddie]

the MAP sensor has a hose line to it.
it is held on in 3 places - one screw is the box vacuum outlet to the sensor. I have a blue one and a black one...so the colour may vary.
the plug has 3 contacts

squueze the butt into the hose fairly tight

I'm really hoping that this gives a good result for you.
I need someone else to find a significant improvement to prove the theory. Don't let me down...lol.

if it works phase 2 will be to determine just how much damping is needed - then maybe looking at a sintered filter or something that gives consistant results. It may be as simple as a needle jet size restriction or even a number drill...

[Tamburinifan]

The bike will probably idle OK with the MAP hose off (must admit, I haven't tried)

Took it off last night and you are right, idles fine. Couldn`t notice any change when revving either but it was on centerstand, no riding.

Also sprayed all ie/electrics connectors I could see w superquality electronics spray, incl MAP sensor. It felt a little smother but som of those connectors are a bit vague.

That hose looks too small in diameter for a cig butt -- but I guess the but is compressible

Btw, I managaed to squeese in 2/3 of a butt before my test ride and that helped.