Thread: X charger fuelling
06-22-2009, 06:56 AM #1
X charger fuelling
I have read the following on here:
> X boats have 42# injectors
>the stock 215 ecu runs injectors at max flow at wot
So the only difference with the fuelling can be the fuel pressure?
So rather than having to buy a RRFPR why not just stick the X boats FPR on? Then it couldn't be any leaner than a stock x boat at wot?
06-22-2009, 07:08 AM #2
The best buy is a Rising Rate for sure.
The RXP has a cruddy FPR, fixed without concern about boost increase, and how it affects the fuelling at higher intake pressures.
I never have been a fan of the 100% duty cycle for any injectors.
Even if you run standard, I think its a good idea to go for a 1:1 RRFPR anyway.
Fuel pump upgrade is a good move to compliment it all.
06-22-2009, 07:12 AM #3
But what is the fuel pressure on a stock 215 engine and a stock 255 engine?
I dont see why there is a need for a RRFPR when the injectors can obviously support the X-SC and an external intercooler at the 255 engines fuel pressure
06-22-2009, 07:39 AM #4
Most injectors need a min of 43.5psi to work as min design.
RXP SC is std at 56-60psi
So here is where the RXP fails.
Say you increase the pressure in the manifold by 5psi, which effectively counteracts the pressure needed to inject fuel in a good atomised spray pattern, and known volume per milisecond opening according to the ECU map.
Effectively the 60 psi now has delivery equivalent of 55 psi.(60psi - 5psi)., so the 1:1 increases the pressure to 60psi plus intake pressure, which will run to 65 psi to keep the fuelling capabilities of the injector as it was designed to be, and in a good spray/atomisation pattern, which is better for combustion etc, plus a known amount of fuel.
The draw-back is the RXP does not know what the fuel/air mixture is, as there is no way provided to monitor this.
The worst part is that injectors get lazy, part-blocked etc as they wear..!!
The HO engine has a big safety margin built in to the maps, and larger injectors. But step outside the "Nice Area", and the A/F can get mixed up, with odd results..!!
A RRFPR will allow you to trim the fuelling more accurately, and as a product, deliver more power via a better controlled mixture ratio.
Go RUDE, it is a good move for the money.
06-22-2009, 07:51 AM #5
So your saying the standard fuel injection on an X boat fails? Because thats all i'm aiming to reproduce, my budget doesnt stretch very far atm!
The point im trying to get across it that the fuelling on the std X boats supports the bigger sc i now have AND the external IC (which i dont have). My ski has the same injectors as the X boat, and works them to their max duty cycle, so the only thing that could cause me a lean condition would be having lower fuel pressure than an X boat, so..
Do the std 255 engines have different fuel pressure to the std 215 engines?
06-22-2009, 08:06 AM #6
Yes, the same pressure.
You have more air going into the engine, and need more fuel by ratio, even though it is not as dense a charge of air, because the charge is not being cooled down.
Seems that if you have a weak mixture, then delivery is down, probably by the pump side of things, maybe blockage on the intake to the pump sock, even a kinked fuel pipe or a duff FPR on the tank.
How do you know the injectors are maxing out, and the mixture is weak?
Check the Pressure at DESS key time if you can.
Fuel pump could be a bit iffi as well, try a Walbro 255. #GSS342.
06-22-2009, 08:12 AM #7
To be honest, I understand the financial constraint, but a Fizzle Intercooler will change your ski soooo much.
Better air-flow through the manifold etc.
I would be careful if you are running lean though. It could get expensive if it goes pop for you.
Keep an eye out for an intercooler on the classified ads here, or post up a WLTB, you never know. I recently changed mine out, and wasn't even out of the ski before it was paid for.
They ARE good intercoolers, and given the bigger charger, this will REALLY make your ski haul-ass for you, with a difference you WILL feel.
06-22-2009, 08:25 AM #8
The RXP/RXT and RXPX/RXTX have different stock ecu maps. Just throwing 42's in will not make it safe to run the X charger + external intercooler in an RXP. You will need a RRFPR.
06-22-2009, 08:40 AM #9
Im not thinking its going lean atm at all, in fact it smells pretty rich, I'm just thinking out loud.
It was on here somewhere I read that the injectors get maxed out at full throttle, someone was trying to add an aftermarket system that looked at the injector pulses and the pulses were gone at WOT as the injectors were always open.
It just doesn't make sense to me that you need a rising rate fuel pressure regulator to run what the stock 255 does with the same fuel pressure and injectors. Yes they have different maps, but if the injectors are full duty cycle at WOT then no map can add more fuel at that point
06-22-2009, 08:58 AM #10
the stock 255 has different fuel mapping and peak RPM's
Users Browsing this Thread
There are currently 1 users browsing this thread. (0 members and 1 guests)
By Shibby1485 in forum Sea Doo Open DiscussionReplies: 3Last Post: 02-16-2006, 09:11 AM
By Jeff C in forum Sea Doo Open DiscussionReplies: 3Last Post: 11-09-2005, 08:00 PM
By SpeedStang95 in forum 4-Tec PerformanceReplies: 1Last Post: 07-30-2005, 04:51 PM
By wwalker in forum 4-Tec PerformanceReplies: 9Last Post: 07-06-2005, 01:36 PM
By Cutter in forum 4-Tec PerformanceReplies: 66Last Post: 07-01-2005, 12:34 PM