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Old 12-17-2003, 02:27 PM   #1
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Default Dyno power supply? HELP

I was reading on another forum that 30 amp power supplies are not good enough for Fantom dynos. If they're not good enough then what is? Also, can you test any motor with the facts machine from fantom or only 19 turn and stocks? Any help would be appreciated.
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Last edited by dimples; 12-17-2003 at 02:48 PM.
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Old 12-17-2003, 10:12 PM   #2
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Use at least 17AH lead acid batts for my dyno. Not sure abt why PS cant coupe with the dyno amp demand. It just doesnt work.
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Old 12-18-2003, 05:12 AM   #3
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Dimples;

Hi,

I use a 75 amp Power supply for my Fantom dyno. I run all kinds of different motors on it . from stock to my 7x1 without any problems. the downside is that the P.S. is expensive, heavy.

Thanks
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Old 12-18-2003, 06:46 AM   #4
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wow, 75A.
Is that switching mode?
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Old 12-18-2003, 08:46 AM   #5
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My 19T motors draw at least 80 amps.....I've used battery from my Honda Accord with my Fantom Facts Machine Dyno.....
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Old 12-18-2003, 10:19 AM   #6
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You need to use a lead acid battery when using a dyno. A 75 amp power supply will do the job, and do it well. But there is a few things to consider. Are you using this dyno for modified or stock motors? For modified, a battery will work best due to its large AH (amp per hour). If you get a deep cycle marine battery that supports 1000AH, a 90 amp pull on a dyno with a modified motor will only "tickle" that battery and deliver you better results. A 75 amp power supply has capacitors in it (not very large ones either) that are fast discharge but have nowhere NEAR the storage, or AH of a lead acid battery. Once you begin your pull on the dyno, the capacitors deliver their charge immediately to support the surge, and the rest comes from the FETS (field effect transitors) in the power supply. The FETS make power, but do not have storage ability like capacitors or batteries do, and will deliver irregular numbers through the dyno by what is called voltage ripple. The power supply will make the voltage and the amperage to support your application, but will do so without the filtering and smoothing effects of the capacitors, the amp draw is too much for the built in capacitors to support the draw at that rate. Now we are talking small amounts and percentages here, which may not seem like alot to you, but we dyno these motors in SEARCH of these small amounts and percentages... right? Now some may argue that lead acid batteries will not discharge as fast as capacitors will, which can cause your dyno to read lower across the board compared to other dynos, and this is true. (IE: your motor may read 63 max power on your dyno and 65 on his) But you cannot compare your dyno numbers to anyone elses really, because no two dynos are calibrated the same, regardless of power supply usage. It would be like comparing apples and oranges. A dyno is effective for your personal tuning, and when combined with a log book of what does and does not work when compared to track results, then your dyno is doing you the best it can, with consistent and comparable results pull after pull. If you really want a bas ass dyno setup, you can goto any car audio shop (easiest place to find one) and pick up a LARGE capacitor of ONE FARAD and put it inline between your battery and your dyno, and you get the best of both worlds. This option is still cheaper than a single 75 amp power supply that can run close to 400$. A lead acid battery can be less than 75$ (uses one less plug than a 75 amp power supply and usually doesnt pop circuit breakers at the track like one either! It even comes with an easy carrying handle!) and a one farad cap can be about 50$. Now, if you are using the dyno for stock... this post will be of use, but mostly you will have wasted your time reading it, for it will not make that much of a difference! Stock motors do not pull amps like modified, and wouldnt drain on-board power supply capacitors as bad. The only consideration then is the cost difference between the two setups. Just my .02 and i hope it is of some use...
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Old 12-18-2003, 10:49 PM   #7
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DaveW:

Hi,

I also use a deep cycle battery for my dyno. mpstly for the really deep winds.
as we mostly run stock I decided on the 75 amp ower supply for taking it to the bigger races (some Motels get a little edgey when you haul out a lead/acid battery). I do agree with you about the battery as you can see when the mods are hitting the max of the P.S. the power curve will flatten out.
as for the 1 farad cap. I was thinking about one just in case we go mod full time. (after the motors at Cleveland we might).

yes the P.S. is a switching P.S.

thanks dave
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