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  1. #1

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    Pulleys and fueling (long)

    I want to give a little information on why using the larger injectors with the 1 to 1 pulley or maybe even the 1.05 is not ideal and explain why after the install gas mileage sucks. First, a little background on ecm tuning and strategies.


    Most manufacturers spend a lot of time matching fueling requirements to air requirements. Meaning the amount of fuel per injector cycle is tested and known and what ever they use to determine air flow (maf or map) is also tested, calibrated, and monitored for accuracy. There is a lot that determines pulse width calculation. Mass of the injector, spring pressure to overcome, time for the injector to get full open, time for the injector to get close, battery voltage, and some other things I am sure I am forgetting, but the point is the oem considers all of this in the fuel mapping table and injector selection. This is done so the oem can build a fuel and air curve for mass production and the accuracy will be repeated within some tolerance repeatedly. What the Kawi is lacking and what every oem of autos I have seen is feedback for fuel trimming and a/f fine tuning. The Kawi does not have this ability. This is important because when barometric pressure, humidity, elevation, and temperature changes(to some extent) the Kawi cannot adapt. The only thing the Kawi can do is go to the programmed lookup table and determine injector pulse width based on the sensor inputs and has no feedback to know if it is right or wrong.


    Now consider adding the pulley and ask when does fueling requirements change? The fueling requirement only changes at WOT and the immediate transition to WOT. The pulley does place more load on the engine at all rpms, but it is negligible when it comes to fueling requirements. Besides, as a rider it is compensated for by throttle input, so in the end loading for the same speed is basically the same. This concept is important to understand or the rest of this will make little sense.


    The larger injectors are rated at 62#/hr @ 70psi according to r&d's web site. This in itself is hilarious to me because most injectors get rated at 40psi or 43psi. Anyway, when you convert the larger injectors to a more realistic base pressure of 43psi(manual stock fuel pressure listed) they equate to around 48#/hr injectors and at 37#s they are still around 44#hr/injectors compared to 38#/hr stock injectors. What this means is at all throttle positions and loads below or the same as the oem level you are over fueling the ski by 44/38 = 15% over fueling. A quick example of a forum member (Harry mentioned after installing the pulley mileage went from 80 miles/tank to 68. That is right around a15% reduction in mileage. I know he had engine problems shortly after but the math does work out. Others have reported the poor fuel economy after install. I have better mileage or at least the same mileage as before) It is important to remember there is nothing that tells the ecm fuel pressure has been lowered or the injectors are larger. Basically, nothing tells the ecm to compensate for the additional fuel or the dynamics of the new injector. If you cannot adequately monitor and meter fuel delivery you will chase the tune all day long. It will be impossible to get it right in all areas. For the rec rider this lack of fuel metering equates to poor fuel mileage. Now if we consider using stock injectors nothing has changed for fueling requirements except at WOT so the ecm is calibrated and knows exactly how much pw is required for the air flow entering the engine. Provided the ecm recognizes the additional air flow and it falls under the limits of the sensors monitoring air flow. My experience is with the 1 to 1 the ecm does recognize and can compensate for the additional air. I think with the 1.05 to 1 the stock injectors will still handle the fueling, but at this point the rising rate of the regulator will be a requirement. More on that as time goes by and the need arises.

    Feel free to correct or discuss anything I have written. I may of made some mistakes in my conversions or overlooked something.
    Last edited by spaulding; 06-16-2008 at 10:10 AM.


  2. #2
    Formerly Ultra250 TN Aquaholic6801's Avatar
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    I dont know all the sceintific aspects of this, but isnt the why the R&D pulley kits also comes with a Fuel Programmer? you can adjust the AFR in three RPM ranges,like when they change mapping, EX......you can adjust for idle to 3500 RPMs,3500-6500 RPMs and 6500 to WOT, those are just examples and can be changed to your own liking............and the AFR can also be changed with in those adjustments..............

  3. #3

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    Quote Originally Posted by Ultra250 Tn View Post
    I dont know all the sceintific aspects of this, but isnt the why the R&D pulley kits also comes with a Fuel Programmer? you can adjust the AFR in three RPM ranges,like when they change mapping, EX......you can adjust for idle to 3500 RPMs,3500-6500 RPMs and 6500 to WOT, those are just examples and can be changed to your own liking............and the AFR can also be changed with in those adjustments..............

    yes, that is true, but the fuel controller cannot take fuel away and it cannot add to a max injector output. It goes back to if the ecm does not have an accurate map of fuel delivery per injector cycle you will have to make sacrifices in the tune.

    If your base is at 35psi you are still overfueling the ski everywhere but maybe WOT. Because the ecm has no feedback and no idea the injectors are larger it goes to the lookup table calculates pw based on load and the injector values of the stock injectors and fires the injector. This will always overfuel the ski until you get the larger injector to act like the stock one. The only way you do this is by lowering pressure.

    On the high side I found the powershot does nothing for WOT fueling. I know of one other ski where the person found the same thing. It is their choice to post and confirm what I am saying. When I look at boost pressure and consider how the ski appears to be mapped I think there is no more pw for the ecm to give and the powershot cannot give more than available.

    I am willing to bet as power gets added to the ski everybody is raising pressure to get WOT a/f within range and none have much success in using the powershot to get it there.
    Last edited by spaulding; 06-16-2008 at 07:26 PM.

  4. #4
    sidenote - you are getting 74 mph, if that is a true GPS 74 mph (which I'm sure it is / not questioning you) then you are doing a lot right. From what I've seen, it takes a great deal to get this beautiful big beast up to that speed. I assume this is on glass with a 2 degree wedge and a riva rideplate and in cold weather?? I'd be interested to know your full setup. All the best

  5. #5

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    Quote Originally Posted by Socaloffshore View Post
    sidenote - you are getting 74 mph, if that is a true GPS 74 mph (which I'm sure it is / not questioning you) then you are doing a lot right. From what I've seen, it takes a great deal to get this beautiful big beast up to that speed. I assume this is on glass with a 2 degree wedge and a riva rideplate and in cold weather?? I'd be interested to know your full setup. All the best
    I did 73.3 Saturday in Florida off the trailor with full tank of gas. I did 74+ repeatedly one evening last week. riva plate and wedge + repitched solas.

  6. #6
    Beagleman62's Avatar
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    Quote Originally Posted by Socaloffshore View Post
    sidenote - you are getting 74 mph, if that is a true GPS 74 mph (which I'm sure it is / not questioning you) then you are doing a lot right. From what I've seen, it takes a great deal to get this beautiful big beast up to that speed. I assume this is on glass with a 2 degree wedge and a riva rideplate and in cold weather?? I'd be interested to know your full setup. All the best
    Socal.........
    Cold weather?????
    JW lives in Florida

  7. #7
    Silence! I Keel You! earthshaker's Avatar
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    Great stuff here

  8. #8
    I am seeing the same things as jason. The fuel controler seems to do nothing at wot, i am now trying the 1.05 pully but i will be using the rising rate reg and a turbo smart boost controler to get my afr correct at wot. I will set a base fuel presure of 38psi and control the higher presure required at wot with the boost controler.
    Hopefully this will work

    rob

  9. #9

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    Your not the only person who had negligible results out of the fuel controller.

    Everything you said makes sense and has been observed by friends doing similar projects. My mate fired up his 250x bolt on turbo kit last night and is going down similar lines to try and avoid running an aftermarket ecu for "stage 1" rec style kit for cost reasons.

    I soo much want to get outa stock class.

  10. #10

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    Quote Originally Posted by australian ultra View Post
    I am seeing the same things as jason. The fuel controler seems to do nothing at wot, i am now trying the 1.05 pully but i will be using the rising rate reg and a turbo smart boost controler to get my afr correct at wot. I will set a base fuel presure of 38psi and control the higher presure required at wot with the boost controler.
    Hopefully this will work

    rob
    This idea is really the best solution to meeting fueling requirements above the 1 to 1. If you let the rising rate do its job the stock injectors or any injector will act larger as fuel pressure increases. The sc the 250X has boost will be almost immediate so with the rising rate fuel pressure will be equal to base pressure + boost pressure and fuel pressure increase will be immediate. Most likely fuel pressure will be way to high. On my ski if I did it this way fuel pressure would be 59psi and a/f would be off the chart rich.

    So the solution is let fuel pressure rise, but bleed off excessive pressure until you have enough to fuel the engine. Effectively you will be able to set pressure under WOT to what you want. If I still had a working wideband I could set my base at 38psi and let the rising rate of the regulator bring pressure to 45psi. I would just have to bleed off the excessive pressure.

    The biggest question I have left to answer is what is the range of the Kawi map and what does the ecm do when it is exceeded. The best solution is to go to a default fuel table that allows fuel pressure to control a/f.

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