Fuel System Question Theroretical

Discussion in 'PSI Superchargers Tech Questions' started by Comax Racing, Dec 22, 2010.

  1. Comax Racing

    Comax Racing Member

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    If a person has a flow meter and fuel pressure sensors on a data logger, plus Davenports jetsize software is it absolutly essential to get the system flowed? Would the datalogging coupled with the software not act as a flow bench? Provided you start out with a very safe tuneup and then work your way up using the data from the car?

    I realize there is no real substitute for baselining your system by having it flowed on a calibrated flow bench but theroretically is it possible? Just curious.

    Corey
     
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  2. aj481x

    aj481x Member

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    That will work, use the modifier to match what you recorded.
     
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  3. JustinatAce

    JustinatAce Member

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    It will work, it just may take a while to get it honed to where one of the fuel system gurus could get you in the first pass or two using their experience. The thing that worries me is how things get affected in the balance of flow when decent size changes are made in nozzles or the return loop.
     
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  4. secondwindracing

    secondwindracing top alcohol

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    what I would do is give Mike Canter a call I have his Number but I rather not give it out unless Mike said he did not care just some respect for the other person, I usally call him at the first of each season for a brush up on the davenport...lol..he is very helpful on the fuel system..Dave
     
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  5. Mike Canter

    Mike Canter Top Dragster
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    Corey the answer is absolutely yes. Nothing theoretical about it. We do it all the time. You can take all the data at 8000 or 9000 RPM in high gear and calibrate Jetsize in one pass. From then on every pass is the same as a flow bench run. Your fuel pressure sensor should be before the barrel valve because Davenport's Jetsize automatically assumes an average loss across the BV.
     
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  6. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    flowed

    Yes and Yes.

    Yes the car theoretically becomes a flow bench.

    No two flowmeters are equal. No two boost tranducers are equal.

    Go ask any 'top' tuner in alcohol or pro mod. I bet you every one of them will tell you to get your fuel system flowed. Not just the pump and plug the numbers into jetsize.

    I've done it both ways. I might have won a lot more rounds when I was driving if I hadn't decided to do exactly what you're talking about and play the flowmeter/jetsize game.

    It's way cheaper than the money they charge too! The odds are stacked against you getting it right off the bat rather than having it right.

    I personally use Randy Anderson. First full lap to the finish line with Fosters car (second pass - air line broke on the first) 5.68/252.

    There's a reason why the experienced guys swear by flowing a system.
     
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  7. Comax Racing

    Comax Racing Member

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    Fuel System

    Thats what I was hoping, over winter I plan to outfit the car with all the equipment listed in my initial question. I have a tune-up that was working pretty well and plenty safe, never really saw the need to flow a system when you have a 4 wheel flowbench strapped to your ass every run. Only downfall I can see to my method is as was stated earilier, I won't have the "fuel system guru's" to give me a tune up.

    Thanks
    Corey
     
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  8. TOL

    TOL Active Member

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    Record the specific gravity of the fuel you are using, and add a fuel temp thermocouple to the data mix, and monitor a few different pressure locations, and you should be repeatable. Probably advisable to have the system flowed as a baseline to work from, initally. You could also add one precision wide band oxygen sensor (a quality one) and keep tabs on your exhaust gas lambda at one fixed repeatable location. The precision WBEGO sums a lot of the variables/errors.
     
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  9. Mac

    Mac Member

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    If I was you.... I'd send your fuel system down to Davenport have it flowed and go pick it up when it's done and Les or Shaun will walk you through everything and you will learn more than you can imagine from those two guys. Why risk it when you have one of the best blown alky tuners around in your own "backyard" v
     
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  10. Mike Canter

    Mike Canter Top Dragster
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    The Hoffer fuel flow sensor is real accurate and even more accurate if you get the calibrated flow sheet with it and put that data into your data logger. Yes, it is possible that two flow sensors can be a little (very little) different but I have enough calibration sheets on file that you can see very little difference from one to the other. Not enough that I would worry. Even without using the calibration sheet data the Tuning Modifier in the Davenport software will calibrate Jetsize to your flow sensor right away. The crazy thing here is that most people that flow a fuel system use a Hoffer flow sensor just the same as what you can buy to go with your data logger and most have it tied to a Racepak to record the flow data so what is the difference. Sorry guys but telling me that a data logger with a Hoffer flow sensor is not as accurate as flowing a system on a flow bench is just not correct. The Hoffer flow sensor is a highly accurate flow sensor that is used in applications that require far more accuracy than our fuel systems require. One thing that will increase the error in your fuel system is not using flow calibrated jets in all the nozzles and bypasses. It is crazy to get a system flowed and then be using uncalibrated jets.

    One of the major problems is knowing what to do with the flow data once you get it and that is the whole trick. That is what a tuner you paid is going to tell you. Not knowing what to do with the data is what destroys the motor not the fuel flow data gained with your own flow sensor.
     
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    Last edited: Dec 22, 2010
  11. secondwindracing

    secondwindracing top alcohol

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    Im sticking with Mike..been there and done it..Dave
     
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  12. Comax Racing

    Comax Racing Member

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    Fuel System

    All the answers here more or less say that yes it can be done only with data from the car but its a good idea to get it flowed. I was wondering about the accuracy of the flow meter concept, if its off then there could be problems. Well, seeing as how Davenports is only about a 2 1/2 hr drive for me, I'll take the advice everybody has given and let them set my system up the first time.

    Thanks
    Corey
     
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  13. Mike Canter

    Mike Canter Top Dragster
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    Corey, please understand that the accuracy of the Hoffer flow meter is excellent and not a problem when used with a data logger. Many of us use it in conjunction with Jetsize and have zero problems. If you don't know how to use the flow data then that is a problem that a professional tuner can help you with.

    With the Hoffer flow sensors the repeatabily accuracy is +/- 0.1% and is typically at +/- 0.05%. Linearity is +/- 0.5% and typically +/- 0.25%. These sensors are validated for accuracy before they leave Hoffer. So with that type of accuracy and flowing 10-13 GPM you can compute just how accurate they are. I will tell you this that it is way more accurate than what you need.
     
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    Last edited: Dec 23, 2010
  14. aj481x

    aj481x Member

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    First the info in Jetsize must be exactly what you observed on the car, it doesn't even matter if your sensors are not particularly accurate as long as they do the same thing every time. Jetsize does not in anyway provide you with a "tuneup". After you establish a baseline running the air correction factors will tell you how to duplicate that run under different weather conditions. After a baseline is established then the flow information lets you figure other combinations that you might want to try. Every time the car runs better, re-set the baseline. You have to also consider that almost everyone opens or closes some jets going down the track so this has to be considered. One place Jetsize is a big help is that it will let you make changes to maintain your fuel pressure when the weather calls for more or less fuel. As an example, on our car we never run a main jet less than .080 or more than .085 at any track. If jetsize calls for anything else we will adjust the nozzles and pump sizer.

    Jetsize is a great product but like all tools it relys on the operator.
     
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  15. JP

    JP Member

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    The main fact is the car actually becomes an accurate flowmeter and when used with a good baseline and program like jetsize accurates changes can be made. However you need somebody that has experience and knowledge on fuel systems after all the datalogger will be displaying information. Not knowledge. ....
     
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  16. Comax Racing

    Comax Racing Member

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    Ya, I'm new to Jetsize and tuning with a logger so I think I'm going to bite it and let Les and Shaun point me in the right direction. I'm into this new engine for a lot of money and the few extra dollars to flow the system seems well spent. Rather than burning something or worse.

    Corey
     
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