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  1. #1
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    G43 Rev limiter rpm? Geo coil mod = pointless?

    Hey guys, so I've stumbled upon some pretty interesting info. Thanks to DonavonLeeder, we've finally confirmed the geo coil rev limit: 13,950 rpm (no load). This was tested on his twin RC, so port limited rpm was defiantly not a factor here. (I think he ended up at almost 17k when he swapped out for an LH coil.)Name:  IMG_1451.jpg
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    I've been doing some pretty extensive work on my g43 and was recently able to go out and test. On flat(ish) ground my gsr40 put down a repeated GPS speed of 45mph (10" tires, 9/76 gearing). Which equates to roughly 12,780 rpm. On the stock g43 coil.

    Now, 1,170 rpm seems like a pretty large discrepancy, however, given that my test was with 180lb rider weight. I'm quite positive I'd make up those rpms with no load, unless the rev limiter cuts in first.

    I'll be ordering a tach in the days to come, just thought I'd share this info. When searching, many people believe the stock g43 coil limit is 12000-12500. The fact I'm already over that number (with a rider) is pretty interesting.

    What do you guys think?
    *******Pedding since '02********

  2. #2
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    My Tsi with Pacsales pipe and Ada 58 carb kit would bounce off the rev limiter hard all the time

  3. #3
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    Quote Originally Posted by EvoSpeed View Post
    My Tsi with Pacsales pipe and Ada 58 carb kit would bounce off the rev limiter hard all the time
    Thanks for the input EvoSpeed, What was your gearing, wheel size, and top speed?
    *******Pedding since '02********

  4. #4
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    Quote Originally Posted by Anon View Post
    How are you caculating your speed and rpm? With a smart phone app or with a actual gps? There are alot of factors. Wind resistance, tire pressure, tire ware, gear ratios, port timing, carbon buildup wonkey coils with burnt out rpm limiter chips. Sometimes when grinding a geo coil's pickups to clear a 40 flywheel the rev limiter memory chip or whatever black majic inside the things over heat and can change what rpm the limiter kicks in.sometimes it can be drasticly lower or even higher.

    So from what ive read, some people feel the rev limiter kick in quicker with a rocket key and stock 43 coil, and a geo coil with a rocket key is too advanced and causes overheating. So would retarding the timing with a stock coil raise the stock limiter from 12,500 to something higher? Man all this timing and limiter jargen makes me realize why its so much easier to just go eton and rc or lh coils. Has anyone tried to fit a g62 stock coil and capactor to a 43?
    Some very good points. It's done with a phone GPS and calculation to convert to RPM. It's pretty accurate actually, I've used it for years. On a related note, I don't believe a rocketkey would change the limiter, unless it's causing the motor to physicality turn out more RPMs.
    *******Pedding since '02********

  5. #5
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    Quote Originally Posted by dsport View Post
    Thanks for the input EvoSpeed, What was your gearing, wheel size, and top speed?
    Gearing was either 8/76 or 8/72. Climbed every hill in SF with 160 pound rider. On both flat and downhill would easily hit rev limiter so I learned to ride ready to lean back

  6. #6
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    On my chain drive Geo engine...
    The limiter definitely cuts in at 16K

    I believe the G43 is 14K..

    A Rokit key will not alter the Rev limiter..

    ANON- I run a G62 source coil and HT coil.
    ... J.
    There is nothing that cannot be fixed with a good cup of Tea.

  7. #7
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    Quote Originally Posted by MrTea View Post
    On my chain drive Geo engine...
    The limiter definitely cuts in at 16K

    I believe the G43 is 14K..

    A Rokit key will not alter the Rev limiter..

    ANON- I run a G62 source coil and HT coil.
    ... J.
    Mr. T, the picture below is the gz25n14 geo coil rev limit. Maybe there are multiple renditions. N23 having a higher limit perhaps? I'll get some more definitive data soon.
    *******Pedding since '02********

  8. #8
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    Quote Originally Posted by Anon View Post
    Attachment 31639 im working on a few 40s now 1 has a lh coil 2 have gz25n23 coils 1 has a stock coil. I have 2 gz23n14 coils too un modded. I have a tiny tach that reads up to 29,999 rpms somewere i need to test. The 2 hk reed 40s are high rev'ers so ill see what the limiters hit at. Ill put a rc coil on one to see how a lh vs rc coil on the same engines run.
    Nice racer pipes

  9. #9
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    The G62 coil has variable timing..

    Black Cherry Le Mans..

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    There is nothing that cannot be fixed with a good cup of Tea.

  10. #10
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    I haven't found the limiter on the grey coil...

    The grey is used on the 26cc marine engine.... So I assume it is either high or doesn't have one..

    The Red coil has 2 degrees more maximum advance than the grey..

    More advance does not always mean more power..
    I covered this in length in another thread..
    As an engine becomes more efficient, it needs less advance.. Not more.
    More advance at lower Rpm can mask an inefficient engine.

    The race Karts have automatic retard as the Rpm rise.
    The engine is very inefficient at the lower end, so has lots of advance..
    As the rpm rises, and becomes more efficient... The timing is retarded. (reduced)
    ... J.
    There is nothing that cannot be fixed with a good cup of Tea.

  11. #11
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    Hey how did the testing go with the coils? From the first post I have gathered that the Eton cover with an LH coil may be the best way to get more RPM's from the LH, but what about the RC coil or is it the same as the LH with the 16k limit? Also have you altered your port timing for the increased RPM's?

  12. #12
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    Quote Originally Posted by Codexfab View Post
    Hey how did the testing go with the coils? From the first post I have gathered that the Eton cover with an LH coil may be the best way to get more RPM's from the LH, but what about the RC coil or is it the same as the LH with the 16k limit? Also have you altered your port timing for the increased RPM's?
    I don't remember seeing an improvement after swapping to an RC coil. I'm going off old memory here, but I believe >17k RPM's are possible with the LH coil.
    *******Pedding since '02********

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    That's good to know, I have an Eton cover with a new RC coil mounted up. What did you time the flywheel to?

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