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Discussion Starter #1
Hey guys,

New to the forum. I've had my MX5 since February. I bought it already boosted, here are the specs on it that are relevant, left suspension & misc out of it:



1992 Mariner blue Mazda Miata MX-5
123k miles
1.6L DOHC
Rotella T6
5-speed manual
Stage 2 clutch
Stock VLSD rear end
Motul Fluids

Turbo goodies:
Greddy turbo manifold
Greddy TD-04H 15G turbo
Godspeed intercooler with custom piping
Manual boost controller set at 8psi
TurboXS RFL blow off valve
Vortech FMU with 6:1 calibration disk
265cc injectors out of a 1.8L
Walbro 255Lph fuel pump

Interior:
HKS turbo timer
Autometer boost gauge
AEM uego wideband gauge

Exhaust:
Turbo blanket/exhaust heat wrap
2.5" turbo back exhaust
Borla muffler

This is my first turbo Miata, so I'm new to the platform. I've owned many turbo subaru's and others. The car currently is tuned by retarding the timing using the cam angle sensor and fueling is controlled by the vortech flu with the 6:1. AFR's look good under boost and idle, and the car has been boosted for 3 years on this setup. Doesn't burn or leak anything. Has seen a lot of autocross time as well. Not sure the MBC is still functioning, dialing it up doesn't affect boost levels so I'm pretty sure it's running waste gate spring pressure only.

What do you think this setup is currently making? What would it take for a reliable 250whp? I believe that is about the limits of this turbo ~18psi not to mention the 5 speeds and the stock rods. I'm pretty sure I already have the core pieces needed for a 250whp goal, just looking for suggestions and guidance from those with experience in the platform. I'm also sure an actual engine management is going to be needed as well as ditching the air control box and going with a speed density type setup.

Glad to be part of the forum!
 

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Super Moderator
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Here's a list of parts that need to be replaced:
Stock VLSD rear end
Greddy turbo manifold/downpipe
Manual boost controller set at 8psi
Vortech FMU with 6:1 calibration disk
265cc injectors out of a 1.8L

The best way to upgrade a Greddy kit is to get rid of it before it cracks. Replace with Artech or Flyin' Miata. Get rid of the bandaid fueling system and pick up a Megasquirt of some sort. At 8 pounds you're probably making 150whp at most.
Welcome!
 

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Beggars can't be choosers.
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Hit up Zerek for a new manifold.
 

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Now what?
Inconel turbo to manifold studs.

There are better (much more modern) turbo systems out there than the Greddy, but it can serve you well if you want to stick with it.

You need to drop the Vortech fuel pressure riser like a bad habit if you want to run more boost than the kit was intended for (~5psi, which you're already over). Get a megasquirt ECU and good injectors (265's won't cut the mustard) and never look back.
 

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Herpity Derpity
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Throw away the entire motor/trans/turbo. Buy 1.8 and returbo it. : 3gears: :haiguyths:
 

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Discussion Starter #6
Thanks for all the feedback so far guys.

No, I'm not throwing away the motor and starting over on a 1.8. For my goals of 250 whp, the 1.6 is an adequate companion.

I know the VLSD needs to go. I'm looking at a Torsen 3.9 as the replacement. I also know the vortech system needs to go as well and a Megasquirt setup needs to be used. What size/brand of injectors should I run for 18psi, which I know is about what the 15g is capable of. I'll look into Zerek for manifold options. But at this point I'm safe to assume the 15G is capable of getting me to where I want to be, or do i need to go with a bigger turbo. If so, what's a tried and true replacement for 250whp?
 

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Lonely White Girl
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Thanks for all the feedback so far guys.

No, I'm not throwing away the motor and starting over on a 1.8. For my goals of 250 whp, the 1.6 is an adequate companion.

I know the VLSD needs to go. I'm looking at a Torsen 3.9 as the replacement. I also know the vortech system needs to go as well and a Megasquirt setup needs to be used. What size/brand of injectors should I run for 18psi, which I know is about what the 15g is capable of. I'll look into Zerek for manifold options. But at this point I'm safe to assume the 15G is capable of getting me to where I want to be, or do i need to go with a bigger turbo. If so, what's a tried and true replacement for 250whp?
3.9+5 speed sucks donkey dicks. Get a 4.1 or 6 speed+3.9
 

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Discussion Starter #12
And I've seen meth hookers who are scabie free. But that doesn't mean I'd take a chance with the one on the corner now.
Like the one in your sig? :D

I know it's not the norm, but just stating with a quality tune and managing factors it's not out of the question.
 

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Like the one in your sig? :D

I know it's not the norm, but just stating with a quality tune and managing factors it's not out of the question.
If you don't bend a rod at the track with that power level, you're probably not pushing the car. That's even a recipe for disaster on the street. Generally 200-220 wtq is considered pushing the boundary on a track car.
 

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Like the one in your sig? :D

I know it's not the norm, but just stating with a quality tune and managing factors it's not out of the question.
Nah. She is only running 9psi. But its a bigger snail than what you're running.
 

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Discussion Starter #16
If you don't bend a rod at the track with that power level, you're probably not pushing the car. That's even a recipe for disaster on the street. Generally 200-220 wtq is considered pushing the boundary on a track car.
Do you know of a tuner around our area who specializes in the platform?
 

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If you want to retain the same plumbing etc the Abe with ARTech makes a replacement manifold and downpipe for the GReddy setup or he can do a custom setup. Abe is a great guy that makes automotive artwork at a reasonable price.
 
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