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  1. #1
    RightOnTarget1's Avatar
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    Exhaust Cooling Flow Rates

    I'm designing what I hope will be an inproved external intercooler setup for my 2007 Speedster 150 SCIC 215 and one thing I need to know is how much water is passing through the stock system so I can keep the same amount flowing to the exhaust system (manifold, J-pipe jackets and waterbox).

    I figured that if I could measure the amount of flow coming out the flush line, I could calculate the total system flow and it would give me a baseline to compare against in the future.

    I rigged up a 5/8" hose to the flush nozzle and ran it to a bucket in the passenger compartment. A friend and I did two runs replicate runs at each of several RPMs and measured flow rate and temperature.

    I haven't yet looked at the holes at the bottom of the j-pipe jacket. When I find out their number and size, I should be able to get a good estimate of total flow and the head needed in the jet pump to push that much flow through the yellow orfice. If anyone knows the size and number of j-pipe jacket holes, it would save me some time...

    In the stock system, I had 9.2 GPM coming through the flush nozzle at WOT increasing 26F (The temps are incidental, but interesting. I always measure everything I can.).

    Please find the data in the attached spreadsheet along with my current configuration.

    I just thought some other might find this useful/interesting. I will add more as I get data.

    Thanks,
    Jim


  2. #2
    PEST!'s Avatar
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    Why waste the time?? There are several that will work already. Riva Rotax and others

  3. #3
    R88ory RXP's Avatar
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    Quote Originally Posted by PEST! View Post
    Why waste the time?? There are several that will work already. Riva Rotax and others
    Im betting he is going to run 1 line for the Exhaust and everything else then 1 big 1 that dumps straight out the side so that he has massive flow throught the IC for better cooling. The way I read it he isnt going to try and make a new IC but a better way of supplying water to it for optimal cooling. R88

  4. #4
    RightOnTarget1's Avatar
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    Quote Originally Posted by R88ory RXP View Post
    Im betting he is going to run 1 line for the Exhaust and everything else then 1 big 1 that dumps straight out the side so that he has massive flow throught the IC for better cooling. The way I read it he isnt going to try and make a new IC but a better way of supplying water to it for optimal cooling. R88
    That's the idea. I must not have written it clearly (Sorry. Writing is not my long suit.). I'm working with a Chinese Type 3 intercooler (Same as XSPower). Its a cross-flow exchanger so it needs to have maximum water flow to minimize the outlet air temp. I don't know what the pressure drop on the waterside is, so I wanted to determine what the stock baseline exhaust system flow is so that I can maintain it when I add the IC and do things like use a green orifice or remove the orifice and split the flows, etc.

    I haven't seen any posts with actual water flow measurements, so I thought others might be interested.

    Thanks,
    Jim

  5. #5
    RightOnTarget1's Avatar
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    Attachments lost

    Well, I attached the data and a photo, but it appears to have disappeared. Let me try again.
    Thanks,
    Jim
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by RightOnTarget1; 12-16-2009 at 11:36 AM. Reason: Inserting table didn't work...

  6. #6
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    You will gain efficiency by going to the external IC as is, and the flow DIRECTION will determine its ability to remove the heat from the air charge effectively...

    HOWEVER, when switching to this IC setup, the incrimental gains for air charge temp and density based on water flow rate through the IC and its exchange rate are pretty much NULL, due to the constant supply of cool lake water.

    Plus any gains you see will be tough in a boat, compared to a ski. Many people have done flow direction testing in the past, and the gains the were seen were TINY. They were running with larger modifications (larger SC, air intake, ECU's, etc)....So on a stock ski, or in this case, a stock BOAT...the gains will not be seen in water flow, only in the adaption on the IC itself.

    The gain you want is not water flow, but water COVERAGE. Ample coverage and flow within the core will give you the best exchange rate.

    Also, mounting the IC in such a way that will reduce trapped air in the water passage, plus integrating a vent line to remove trapped air will ensure that the core is always WET.

  7. #7
    RightOnTarget1's Avatar
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    Quote Originally Posted by Danny View Post
    You will gain efficiency by going to the external IC as is, and the flow DIRECTION will determine its ability to remove the heat from the air charge effectively...

    HOWEVER, when switching to this IC setup, the incrimental gains for air charge temp and density based on water flow rate through the IC and its exchange rate are pretty much NULL, due to the constant supply of cool lake water.

    Plus any gains you see will be tough in a boat, compared to a ski. Many people have done flow direction testing in the past, and the gains the were seen were TINY. They were running with larger modifications (larger SC, air intake, ECU's, etc)....So on a stock ski, or in this case, a stock BOAT...the gains will not be seen in water flow, only in the adaption on the IC itself.

    The gain you want is not water flow, but water COVERAGE. Ample coverage and flow within the core will give you the best exchange rate.

    Also, mounting the IC in such a way that will reduce trapped air in the water passage, plus integrating a vent line to remove trapped air will ensure that the core is always WET.

    Danny, I always enjoy reading your well thought out, quantitative posts!

    I am laying the foundation for further modifications in the future, so I want to get the IC set up correctly first. Though I merely have a lowly boat , I appreciate all the performance I can get from it and I can tell that I am IC limited now.

    The main point of this exercise was to find out how much water was really flowing through the system now. I have not seen any other measurements and it is hard to look up the tunnel at WOT. I have seen some others suggest it was 2-3 gpm.

    I am planning to install a "Type 3" intercooler mounted vertically with water inflow at the bottom and outflow at the top and air in and out at the bottom. This will keep the core completely full and minimize the condensation issue (Warm, moist air, cold water, causes condensation to puddle in the IC.).

    As you and I discussed in another thread, I think, GreenHulk provided some numbers for IC Air in (250 F), IC Air out (104 F) in 90 F water. Assuming 18.1 gallons per hour fuel (100% duty on 3x38lb injectors) and a 12.2 AFR, that's 1390.8 lbs wet air/hr. You've got to move 9 GPM to get your water outlet temperature down to 101.1 F. On a cross-flow exchanger, where the air flows across the water (The incoming air can meet a low temp part of the core where the water is near the inlet temp of 90 F or the air can flow by the other end where the air is near 101.1 F. (I know you know all this, but some reading might not.)), you need a really big exchanger to get the air temp down near the approach temperature. In this example, the average effective water temperature is 95.5F. You can't get cooler than the average temp and it takes a pretty big exchanger to get close. The more water you can flow, the lower the average temp and the more cooling you can get.

    Think of it this way: you are absolutely correct (Of course, .) about coverage being important. You want as much heat transfer area as possible working for you. However, as the water in the core moves closer to the outlet and the water warms up, it stops cooling as effectively (less delta T) and the area becomes more and more useless. By flowing more water, you make that warm, less effective area smaller and get more heat transfer (Increased flow also increases the heat transfer coefficient, but we are probably gas side limited anyway.).

    I'm aiming at being able to supply at least 10 gpm to the IC with full coverage. I am not expecting a big absolute performance boost from this step. I am, however, expecting to see less fade on warm days.

    When you did your excellent air side flow tests, did you happen learn of any water side flow data?

    Thanks,
    Jim

  8. #8
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    One thing to remember is that when the throttle is varied, there will be different flow volume. When the pump goes through chop, there is different flow volume.

    Also, you have to factor in exchange rate of the water and the core. If the water is moving too slowly, it will soak up a lot of heat, and retain that heat as it travels through the core, thus reducing the efficiency...IF it moves through to fast, it can not soak up the heat fast enough to be efficient...

    PLUS, you can only push so much water through the core passage before you can't push any more. Water isn't like air, it can't compress.

    Concentrate on getting air in/out of that motor as effectively and efficiently as possible. Its only then will you see the benefit of water flow rate at a measurable level...

  9. #9
    RightOnTarget1's Avatar
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    Quote Originally Posted by Danny View Post
    IF it moves through to fast, it can not soak up the heat fast enough to be efficient...

    PLUS, you can only push so much water through the core passage before you can't push any more. Water isn't like air, it can't compress.
    Danny, thanks! I really appreciate your insight and your experience. With regard to the flow variations. I didn't mean 10 GPM constantly. I meant at WOT... One way to help deal with variaions is to use an oversized exchanger so that you have excess area available to help soak changes.

    If you don't mind, though, I would like to respectfully disagree with you on the two points quoted above. I don't think it is really possible to move water too fast through an exchanger. The higher the flow rate, the higher the heat transfer coefficient on the water side will be, the greater the average temperature difference will be, and the greater the overall heat transfer will be. There is, of course, a practical limit (pressure) and with gas/liquid exchangers, the gas side coefficient is usually much lower. That's why you usually have fins and extended surfaces on the gas side.

    Also, I think you may have it backwards on compressible flow. As I understand it, in theory, the more pressure you put on water, the faster it will flow. Gases, on the other hand, will increase flow rate with pressure up to the sonic velocity and then it doesn't matter how much pressure is applied, no more flow.

    I picked 10 GPM because the Type 3 exchanger has 1/2" NPT water side inlet and outlets. 10 gpm is a reasonable flow rate for 1/2" pipe (~10 ft/sec is a rule of thumb - this is 10.6 ft/s.). I don't know the pressure drop charateristics of the core yet, but I assume the designers sized the inlets and outlets correctly.

    Sorry for nitpicking. You are correct in your main point that air flow through the engine is the main thing. I'm just building the foundation for upgrading my SC and exhaust systems.

    Thanks,
    Jim

  10. #10
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    If you can find a way to measure the flow rate through the RPM range using variable size of hoses, at the same time measure the air intake temp before/after along with before/after the IC...do a side by side comparision, then we have data to rely on...

    When I talk about compressible flow, I'm talking about physical compression. Yes, you can increase water flow by increasing pressure...but there is a limit to how fast you can move an object that is solid (molecule level, compared to air) before youmeet physical restraint. Air can compress inside a cavity, water can not...

    You make some excellent points, yet I can assure you that water flow through the IC has been investigated. If gains were found, then individuals would be talking about it and its benefits. not saying you are wasting your time, but you might want ot consider people have been down this road before, so unless it proves worth while, it is not pursued anymore.

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