Alternative fuel pumps for FI KTM990

[bkshovel]

Ok fellas, fer us dumb ol' country boys that speak psi. instead of nm. What kind of pressure are you talking about? If I understand correctly the pump you're working with puts out 43gph at 45psi free flow. I gather that' not enough. Summit sells a pump that is 43gph at 85 psi free flow, part # sum-g3138. It's also cheaper, $81.95. I've had good luck with Summit's stuff as far a quality. It looks like a twin brother measures 1.87 x7.25. Probably comes out of the same factory. This with a bypass regulator and a return line to the tank to keep the fuel and pump cool? Am I out of line?

[Head2Wind]

Originally Posted by bkshovel

Ok fellas, fer us dumb ol' country boys that speak psi. instead of nm. What kind of pressure are you talking about? If I understand correctly the pump you're working with puts out 43gph at 45psi free flow. I gather that' not enough. Summit sells a pump that is 43gph at 85 psi free flow, part # sum-g3138. It's also cheaper, $81.95. I've had good luck with Summit's stuff as far a quality. It looks like a twin brother measures 1.87 x7.25. Probably comes out of the same factory. This with a bypass regulator and a return line to the tank to keep the fuel and pump cool? Am I out of line?

just so us other ol' country folk are not misunderstood, you cannot have "free flow" and 45psi of pressure.... in that if you have a open hose to atmosphere coming from the output of the pump I would call that "free flow" with no head pressure on the pump. In my understanding this is the pumps full on capability to move X number of Liter/Gallons of fuel per minute/hour. So, as described, the Summit pump will flow/pump 43 gallons per hour at a 85 pounds per square inch pressure. Which in this application, given the horse power rating of the engine, this pump would be able to deliver enough fuel to the injectors/engine to support the roughly 100 horse power that the LC8 produces. HOWEVER, we still need to REGULATE that pressure down to a usable level, in this case the stock pressure is 3.5 bar (50.7632082 pounds per square inch), so if we chose to use a fuel pressure regulator that is set at 3.0 bar (43.5113213 pounds per square inch) the fuel rail pressure would be reduced by roughly 7.2 PSI, a ~4.3% reduction in pressure, will result in a reduction of flow through the injectors.

So we either chose to create a system that bleeds the pressure off into the tank prior to the fuel rail or we do it at the end of the fuel rail, which in most cases for high performance (IMO) is best (end of rail pressure regulation/dump/drainback). The stock system dumps the fuel directly back into the tank at the pump assembly, and "dead heads" the fuel rails at the injectors. So the only fuel that flows is the fuel that is injected, which can lead to higher fuel temperatures at the point of injection and all the fun that comes along with that.... Again, in a high(er) performance application, cool(est) fuel and cool(est) air is best for maximum performance with current fuels and technologies. third beer for the day watching the hockey game so I might be off a bit.....

[PowerCell]

I run a custom adjustable pressure regulator set at 51 psi...

[bkshovel]

Thanks Powercell. That's what I was asking.

[PowerCell]

These are a direct drop-in into the Cannondale FPR housing...

http://www.eurospecsport.com/product...regulators.htm

[madbiker1]

I just pulled a fuel regulator out of a 1992 BMW 325i with an e36 engine that looks exactly like that. 3.5 bar I believe as well.

[jeremyk]

Not sure if this has been mentioned yet, but running at a lower pressure will screw up air/fuel ratios under "open loop" operation (i.e. full throttle). In closed loop, the O2 sensors will likely detect the lean condition created by not enough fuel (~40 PSI vs ~ 50 PSI) and may be able to correct. However, most FI systems go into an open loop mode under full throttle and no longer use O2 feedback. They use "fixed" look-up tables in the ECU to determine proper air/fuel ratio and those tables are based on a assumption of 50 PSI fuel pressure.

[bikyto]

I thought I'd bring this back to life.
A few years have past and I was wondering if any reliable solutions have been used and if these could be shared with everyone.

Thank you in advance!

[gefr]

According to my findings there are plenty of replacement fuel pumps with the needed diameter of 38mm. Length is usually shorter at the large dia part, but can fit. The same goed for the connections area and the intake side. Small modifications are needed but not to difficult. The major obstacle is the power consumption. All the car fuel pumps I saw have power consumption close to 6Amps. This prooves too spendy for our electrical corcuit. So when driving in traffic and the fan comes on, the voltage plunges and the motor starves from fuel. I have yet to find a fuel pump with car fuel pump dimensions and motorcycle fuel pump consumption close to 3,2amps rated at 3,5bar and flowing 35lit/hour. Most of these little babies come in smaller packages. Maybe they can fit with some transormation. Still searching.
Cheers.

[Vicks]

Gefr, i know i replied to your query on my thread that i never had any issues with voltage drop on the toyota fuel pump retrofitted into the stock assembly on my 990 but now that i think of it, my dual battery setup might have had a hand in this. It might have prevented the loss of pumping capacity when the radiator fan kicked in.....

[gefr]

Thanks Vicks
I ask for fuel pump specs and the chinese feed me with whatever they have in hand.
I start leaning to the possibility of using a 3bar fuel pump, as long as it draws close to 3,2Amps. I think I saw such a pump. I think It is worth it even if the dia=30mm.
I am contacting suppliers that say they can upgrade fuel pressure to 3,5bar on items they quote at 3.0bars.
Cheers.

[jeremyk]

One trick to get more power to the pump would be to use a relay in the circuit (triggered by the stock fuel pump "hot" wire) and run a dedicated, larger diameter wire from the battery to the relay to the pump. This might be enough to take care of the drop in power when the fan comes on.

[gefr]

I didn't think of that. When it comes to electrics I am totally numb.
Thnx.

[Vicks]

The limiting factors could be either the crappy stock wiring (quite a few ppl have reported about changing out the wiring completely with higher gauge copper wires) OR the stock battery capacity being just enough to handle the FI and electronics on the bike. It does not hurt to just replace the FI pump wire with a higher gauge one and check if that helps.

You can also ensure that the battery is fully charged up and then see if the pump still stumbles when the rad fan kicks in. By this you can eliminate these causes and narrow down the issue.

[gefr]

I read:
14,2V engine running, no lights
13,8V lights on
13,2V lights on + heated grips
12,4V lights on + heated grips + fan on but it is not stable and plunges occasionally under 12V.