Adjusting fuel pressure...

[jtucker]

Does anybody know what the pros or cons are to adding something like this to your bike?

 

Evoluzione Fuel Pressure Adjuster

 

Just curious...

[Guest Cliff Jefferies]

Apart from the obvious - remapping the ECU, there is no real benefit for a standard engine. At full throttle and RPM the injector on time approaches 100% on. If due to engine mods, the injectors can't supply enough fuel, you have a few options - higher fuel pressure, higher flow rate injector or dual injector.

[Guest jeremy]

It may or may not have negative effects on the fuel pump also, if you have less fuel at slow speeds flowing through the pump more heat may be built, guess you'd just have to try and see

 

cheers

[emry]

I currently run my fuel pressure at +10psi to combat the pinging. (Don't have a PC yet) I haven't run into any problems so far, 4000 miles at least. This sort of mod is very common on most fuel injected cars, you know the obnoxious ones with the buzzy grapefruit pipes.....

[jtucker]

I currently run my fuel pressure at +10psi to combat the pinging. (Don't have a PC yet) I haven't run into any problems so far, 4000 miles at least. This sort of mod is very common on most fuel injected cars, you know the obnoxious ones with the buzzy grapefruit pipes.....

I was wondering about this. Do you think it's possible that the reason some bikes ping and others don't is because fuel pressure is not consistant from bike to bike?

[Cliff]

The only thing this would be doing is running your bike richer across the board. The richer mixture is what is stopping the pinging.

[callison]

I kind of doubt that fuel pressure varies greatly from bike to bike. Mechanical regulators are a mature technology and the specs for the regulator are pretty tight, something like 42 PSI +/- .5 psi. I am going from memory here, but I'll look it up later. I did run across one 97 California with a cam from a 97 Sporti. He just modified the regulator for a higher pressure to accomodate the necessary fuel requirements and the bike apparently runs just fine.

[dlaing]

The only con I see from increasing the pressure is you might run too rich. But if you re-map the mixture and have mods that require more fuel, than I can only think good things about tweaking fuel pressure.

Jason Tucker(oops, I mean Emry. edited 12/23) running at +10 psi results in 52 psi or an increase of about 24%.

If you convert 24% into air/fuel ratio that is a difference of maybe 14:1 changed to maybe 10-11:1 which is probably too rich. But if he was off the charts before at maybe 18:1, he would now be in the healthy 13/14:1 ratio. Of course it is unlikely that his map is flat, so he is probably too rich in some places while good in others.

Proper tuning and re-mapping is the way to go.

[emry]

I agree with ya'all. While raising the fuel pressure is not the best solution, remapping etc. is much better, it has worked wonders for my bike. Granted it does run a little rich around 3-4 grand, it far out ways the extreme lean conditions that I had before. Also remember that the extra fuel added by increasing the fuel pressure is not linear. At short injector dwell times the increase in fuel volume is minimal but as the dwell is increased the volume of fuel is increased exponential manner. Thus it really only makes a noticeable difference in the higher throttle settings. Which was the only time my bike would ping.

Someone with better math skills could use Boyle's Law to produce a simple graph....

[jtucker]

FWIW, my bike is one of the ones suffering from the pinging problem. I just ordered a pressure gauge just to see where I'm currently at. Will post results when I have them.

 

Emry, you said you had to boost your pressure 10 PSI to get rid of the pinging - do you know what your original pressure was? It would be nice of we could establish a link between the pinging problem and something as simple as fuel pressure...

[callison]

I can't imagine the pressure is too much different than that specified in my Sport 1100i shop manual. 43.5 psi +/- 3 psi while running and 36.2 at rest after the pump has stopped.

3 +/- 0.2 bar and 2.5 bar for the metric specs.

[Paul Minnaert]

The pressure for the daytona is normal 3bar, with a factory C kit ( diferent cams, pistons and eprom) you get a 4 bar valve. So guzzi has done it theirselves.

[dlaing]

Regarding the pingiing problem: I cured my problem by slightly enriching the 001 map in the zone that pinged, but since then by going leaner to improve fuel consumption I am now at a point that was leaner than when I was pinging, and I am now getting no pinging.

The reason for this is that either I am reducing the pinging by reducing carbon build up or something is inconsistent like the TPS, one of the sensors, OR the Fuel Pressure.

So the idea that a lack of fuel pressure is causing the pinging on many bikes is a possiblity.

Can you use and read the Evoluzione pressure meter while driving? It would be interesting to monitor the fuel pressure, especially if the pinging is intermittant(spelling?)

It would be really cool if you could dial up the pressure on the fly(while riding or quickly while pulled over.

[callison]

Daytona's, Centauros, and Daytona RS's use a different TB injector than the Sport 1100i's/V11 Sport models. I'm going to guess that they offer more fuel flow for pressure than ours do, and the TB's can use the higher pressure. 4 bar on a V11 Sport would probably be somewhere near the limit that the fuel orifice can pass and may even be too much. Does anyone have a chart for the various models of Marelli TB's?

[jtucker]

Took a look at the shop manual last night. According to that, it runs at 3 bar. Now, this could be a result of wacky translation in the manual, but the way I read it, it seemed to indicate that if the pressure is running below 3 bar, the fuel may not atomize properly. Also, it said that the pump has some sort of cut-off at 5 bar, which is intended to keep it from overheating if the pressure gets too high.