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GT-40 Performance Upgrades Help |
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Rlbarrasjr 
Newbie 
Joined: July-27-2018 Location: 70122 Status: Offline Points: 9 |
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 Posted: July-20-2019 at 7:58pm |
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My understanding from everything I've been through is that 300M is a better tune and can be used on the older models and benefit.
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DHMcFadin
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Joined: May-27-2019 Location: Austin, Texas Status: Offline Points: 312 |
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Posted: July-20-2019 at 8:01pm |
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Does the 300m give the engine a little more umph?
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Rlbarrasjr
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Joined: July-27-2018 Location: 70122 Status: Offline Points: 9 |
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Posted: July-20-2019 at 8:06pm |
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Best I can tell is it's a safer tune. A little richer and better idle. You probably won't notice any power difference
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gt40KS
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Joined: August-05-2017 Location: Wichita Kansas Status: Offline Points: 943 |
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Posted: July-22-2019 at 12:07am |
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Right now I'm running the computer I put together with the add on chip and the 300 tune. Most of the reason I opted to try this was the possibility of evening out the idle. I first ran the new engine on the 300, then for comparison switched back to its stock 290 computer. Honestly, I really couldn't tell any difference between the two and it really did nothing for the idle. I have switched back to the modified computer with the 300 tune but certainly not because of any perceptible performance gains. More because, as Rusty says it's supposed to be a better, upgraded tune which I took to mean the air/ fuel mix, timing and the like was more refined.
Performance increase? No. Better fuel economy? Not that I can tell. Smoother, more consistent idle? Hard to say for me since I had what seems to be a host of problems causing idle issues. They appear to be solved now but was it at least partially due to the tune? Anybody's guess. |
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JCCI
1995 Ski Nautique GT40 |
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lewy2001
Grand Poobah 
Joined: March-19-2008 Location: NSW Australia Status: Offline Points: 2234 |
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Posted: July-22-2019 at 10:18pm |
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The GT40 uses batch fire injector firing and this likes a nice rich idle mixture. I spent many hours playing with idle mixture and timing on my Megasquirt DIY setup. Had always planned to change to sequential firing but have never got around to it maybe this year
 There is no power advantage with sequential fire injectors just a better idle.From memory when I went above 13:1 the idle was erratic around 12.5 to 12.8 seemed to produce the best idle with a bit more timing. If I get time I will bolt my O2 sensor and EEC1V back on and see what the difference there is in the 290 compared to the 300 tune. Maybe just send it all over to Keno he loves R & D 
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If you're going through hell, keep going
89 Ski <a href="http://www.correctcraftfan.com/diaries/details.asp?ID=5685" ta |
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KENO
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Joined: June-06-2004 Location: United States Status: Offline Points: 10641 |
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Posted: July-23-2019 at 9:47am |
Send it to Joe, we seem to do all our R&D on his boat
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DHMcFadin
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Joined: May-27-2019 Location: Austin, Texas Status: Offline Points: 312 |
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Posted: August-08-2019 at 1:59am |
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Turns out I already have the 300m. Are there any other hardware upgrades I can make to this engine. I have seen threads throwing around 400 hp but there is no context. Is there anything else I can do to get the horsepower up?
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lewy2001 wrote: