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Thread: PWM for Fuel Pump Operation (CTS-V Pump)

  1. #1

    Default PWM for Fuel Pump Operation (CTS-V Pump)

    I tried searching and maybe bypassed the threads pertaining specifically to fuel pumps and the PWM+/- from the Dominator.

    I currently have a control module from a company called VaporWorx, but not sure I need to use that, or if I can just use the Dominator to send the PWM signal to the pump directly. Part of the trick with this is, I have two CTS-V Modules in he car and the controller is MAP referenced to turn the second pump on. I would prefer to have the Dominator handle this, as I don't have to tee into my already complete boost control lines to send a reference to the control box.

    Does this require a custom I/O channel to be set, set with PWM + or - and label as "fuel pump 1" & "fuel pump 2" for example? What's the best way to go about this?

    Another question pertains to Boost-A-Pump usage and increasing signal voltage to "overdrive" the pump. Can the Dominator send a higher voltage than +12V or is that set?

    Thanks for the help! William
    1969 Camaro - LSX427 TT

  2. #2

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    I'm familiar with the VaporWorx setup and I would do yourself a favor, and just use Carl's control module for it. It is a nice piece of hardware and works flawlessly. One, the primary pump you're closing the loop off the pressure transducer right back by the tank. Everything is well thought out, and OEM reliability.
    I just switched to it on my Nova and love it. Eliminated my return line, simplified my plumbing, never a pressure drop (so far). Datalogged fuel temperature, and no increase in temp over using the return line so far.
    Tom

  3. #3
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    The big challenge with PWM, is that you ALWAYS need an external controller or a solid state relay to provide the power or ground side to the main component being controlled.

    The Holley PWM outputs are just like all the rest of the outputs. MAX amperage draw of 2 amps.
    2 amps is plenty for an LED or a small light bulb (and some smaller solenoids like the ones used for Boost control), but not near enough for most other devices.
    Also, you need a relay (with a built in diode/resistor) to prevent any flyback voltage that might come off of the main device.
    Flyback voltages can be in several hundred volts, and momentary spikes of more than double or triple of the normal amperage draw of the device.

    The challenge with a non return system is that it doesn't support a lot of power (when compared to a return style regulator).

    The Dominator Outputs should not be used to directly drive a fuel pump. You will need a relay, which means that you can only get more voltage if you have an external device (such as a boost a pump) or a higher voltage battery/alternator setup.

    Me personally, I always avoid "boost-a-pump" setups. They are just a band-aid to the bigger problem, of the fact that you really need more pump to begin with, or a double (or even triple) fuel pump setup.

    I would much rather have a dual in-tank pump, than have a "boost-a-pump" setup.
    Last edited by S2H; 12-28-2015 at 11:53 PM.
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  4. #4

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    That makes sense on still needing a controller.

    As for returnless, this system has several cars over 1000 RWHP with no issues with fuel pressure. I have dual in-tank pumps. It's just two CTS-V pumps. If these can't support the power I want (which is one concern since they have issues above 65 psi without Boost-A-Pump, people are maxing them around where I'll be at), I'll be swapping these for 3 Walbro 485s.
    1969 Camaro - LSX427 TT

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    Quote Originally Posted by will69camaro View Post
    That makes sense on still needing a controller.
    Yeah, the Holley ECU's PWM± Output operates the control unit, not the electric component itself.
    Example: http://documents.holley.com/flyer_brushlesspump.pdf (Holley EFI Brushless Ultra HP & Dominator Fuel Pumps With Controller - Page 2)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  6. #6

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    Thanks for the info Danny!

    The more I read up on the Dominator, the more excited I am to get to use it on the running car. So many options!
    1969 Camaro - LSX427 TT

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    Quote Originally Posted by will69camaro View Post
    That makes sense on still needing a controller.

    As for returnless, this system has several cars over 1000 RWHP with no issues with fuel pressure. I have dual in-tank pumps. It's just two CTS-V pumps. If these can't support the power I want (which is one concern since they have issues above 65 psi without Boost-A-Pump, people are maxing them around where I'll be at), I'll be swapping these for 3 Walbro 485s.
    1000 HP on who's dyno?
    If they aren't in the 7s in the 1/4 mile, they aren't even close.

    The problem becomes that you suck the rails dry faster than the returnless system and PWM pump can keep up with it.

    So the first injector in the rail is fine, and the last one doesn't have enough fuel. We see a lot of ashtrays from returnless systems.

    The more pressure you have, the less total flow you have. (They are an inverse of each other.)
    Pressure is a measure of the restriction. (This is why a pump can be rated at 2200 HP for carburetors, and only 1200 for EFI.)
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  8. #8

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    Well Mark Stielow has one making 1000+ with identical fuel system. Not sure on the dyno, but being GM performance manager in Detroit, I bet he has sufficient access.

    Plenty of cars make 1000 RWHP, and don't run 7s. I'm expecting over that, and won't be in 7s for sure. Different setups.

    We'll see how mine works. I'm not shooting for the moon right away, and will add a return if it can't handle it. Right now my fuel pressure is taken off the "dead head", so that will be the first place to lose.

    Pressure is the issue I'll face with CTS-V pump. They have an internal bypass that doesn't allow over 65 psi. Start adding boost, and the injector differential will drop.

    I have a few challenges ahead of me.
    1969 Camaro - LSX427 TT

  9. #9
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    If they aren't in the 7s, they aren't making 1000 HP to the tire.
    At 3460 lbs, at 900 rear wheel horsepower, a car will go 7.90 all day long if the suspension is right.
    The shop car does it all day long at around 900 to the tire when we use the lowest boost settings on it.
    (The settings we use when we do no-prep and legal street races.)

    But that is not a debate for this forum.

    And yes, the big challenge will be the internal bypass at 65 psi.
    The CTS-V pumps, are good to around 700-750 to the flywheel, before they are out of flow.
    If you think it can do more, simple physics says that 330 LPH (what the CTS-V pump claims to do, which is typically only in optimal lab conditions) is just not enough to do more than that. And even with a boost-a-pump setup, they still are done around 800-850 at the flywheel.

    And don't get me wrong, that still makes for a very stout and fun toy.
    But it's not nearly as safe and capable as a return style multiple fuel pump system.
    (Or even better a belt drive/cable drive pump.)

    The only solution for the internal bypass if you insist on using the CTS-V pump, is to try to run it at 43 psi, and use a larger injector.
    Of which, it's already been proven in many Engine Masters challenges, that an oversized injector that you can control getting all of the fuel into the cylinder while the valve is open, makes more power & torque, than if you have an injector flowing static open (100% duty cycle), and it sprays while the valve is open & closed.

    At that point, you will run out of pump before injector, which will still be around 750 flywheel horsepower. But you at least have the option of upgrading the pumps without having to change the injectors at that point.


    Also to note. Holley EFI version 4, has the ability to control a direct injection fuel pump.
    The table can be used to control any PWM fuel pump controller, and to target a fuel pressure.

    The table is in fuel pressure PSI, and you can set the axis to whatever values you want.
    (I suggest the axis be RPM & manifold pressure - kPa or psi, whatever you are most comfortable with.)
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  10. #10

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    Mad you said debate for another forum. The cars in talking about aren't drag cars. Can't say a car doesn't make the power by comparing it to a situation with so many variables. I don't doubt a properly setup car car go 7s with 1000 RWHP.

    I have TWO CTS-V pumps. The guy who made the controller for it (VaporWorx) has done independent testing trough his business, and gets repeatable results of 485 lb/hr @ 13.5V & 60 psi. That's what his controller is setup to run.

    Going with BSFC of gas being ~0.6, gives capability of pumps to make 800/ea.

    I'm planning to run 60 psi, but with boost it'll end up being around 43-45 psi across the injector. Or of the reason I ditched my ID1300s and went to the new ID1700.

    Noted on V4 controller. I'll play around with those tables some to see what I can do. For now I'm sticking I guess with VaporWorx setup for now. And if it doesn't do what I want, or the V pumps don't work out. They'll come out for 3 Walbro 485s. And if I can't keep pressure, I'm not beyond adding a return. Just not in the initial plan.


    Just did some digging on another forum, where I asked the question on these pumps. Stielow is making 1000 flywheel, but it's a blower motor and on E85. He used a Boost-A-Pump on one of the pumps to get the additional fuel he needed for E85. Said the V pump is sensitive to voltage. 13.5V = 485 lb/hr while 15.7V is 615 lb/hr.
    1969 Camaro - LSX427 TT

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