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Old 02-17-2008, 05:15 PM   #1
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Default Turbo Miata Question - 230cc vs 305cc

Question for you turbo gurus, currently I am running a 1.6 turbo Miata with the stock pump, 1999 1.8 230cc Injectors and a Vortech FMU with a 8:1 disc.

This setup is working fine at around 8psi. What would I gain or lose from switching to some Supra 305cc injectors and either disconnecting the Vortech FMU completely or running a 4:1 rate disc. I will be running the same 8psi.

I like to experiment with different setups hence why I am asking this question.

Please advise, your input is welcome here.
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Old 02-17-2008, 05:35 PM   #2
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I'm gonna say if what you have is fine, and your not looking for more power, and your tune is good, and overall your satisfied with your current power level, why change it?
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Old 02-17-2008, 06:41 PM   #3
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I am not a fan of dicking with things that do not need to be dicked with. Unless you plan to make more power, the only thing the 305s will do is reduce your idle quality.
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Old 02-17-2008, 07:09 PM   #4
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My plan is to run about 11/12psi if possible and I wanted to get some feedback on which setup will provide the best power band across the rpm range as well as the best maximum power output.
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Old 02-17-2008, 07:15 PM   #5
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305s might kill your gas mileage if you don't have a way to control them.
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Old 02-17-2008, 07:29 PM   #6
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My '96 ecu is able to idle 305's just fine and I've been able to get 35mpg highway with them.
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Old 02-17-2008, 11:41 PM   #7
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Quote:
Originally Posted by SamS View Post
My '96 ecu is able to idle 305's just fine and I've been able to get 35mpg highway with them.
Because you have EMB, he's saying it'll suck if you don't have any fuel controller.
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Old 02-17-2008, 11:43 PM   #8
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yeah that was before EMB, sorry should have said that
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Old 02-18-2008, 01:02 AM   #9
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You're running the 6:1 disk now? What timing controls?
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Old 02-18-2008, 07:58 AM   #10
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I am running the Vortech 8:1 disk now, forget to add that I did change the fuel pump a couple years ago, it is not a Walbro but it rated up to 100psi. Also the turbo is a small IHI VJ-11 off the Mazda MX6. MSD Boost retard is used to retard timing on boost.
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Old 02-18-2008, 01:27 PM   #11
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Sorry, missed the 8:1 disk in the OP.

Couple of questions and some thoughts:

When you say your set-up is "working fine", what do you mean? Are you checking AFs?

You should check the output of your fuel pump and get access to a widbeband before you do anything else. Without injector control, you won't be able to dump your FMU at 8 psi just by switcing to 305's. If your fuel pump is working though, with the 305's you'll be able to drop down to the 6:1 or 4:1. You'll need a wideband to see which is the more appropriate disk though.

I'd take a guess and say you're running rich even with the 230s at 8 psi and the 8:1 disk if your pump is capable of putting out 100 psi.
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Old 02-18-2008, 09:35 PM   #12
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Any more comments? I am appreciating the feedback, I havent changed a thing as yet.
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