Already Boosted - Now What?
 

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:

https://www.miataturbo.net/attachmen...ine=1445221410

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!

If the answer isn't "Miata", then it's "more boost."

There's no way we could even guess as to the power it makes. A terrible way to guestimate: half a bar of boost (50% above atmospheric pressure) might mean 50% more horsepower than stock. So, 115hp x 1.5 = 170-ish horsepower... This number is based on some wild assumptions, the most glaringly wrong of which would be a well tuned system.

Rising rate fuel pressure regulators and naive boost-referenced timing retard doesn't really lend itself to being called "well tuned." That doesn't mean you're lying; it seems reasonably well put together to live for three years and multiple track events. Your methods are effective (i.e. they get the job done) however they aren't likely to be called efficient.

Moving the needle to "well tuned" would mean a standalone, larger injectors, and a moderate quantity of dedicated tuning time. Even with 8psi, you've probably got another 15-20 hp lurking under hood just from getting the tuning nailed down to a science.

As you push boost higher on that turbo, heat will become a larger issue. Rather than chasing higher boost, consider other methods that allow higher air flow at the current pressure levels. I'm not good at all with the Miata NA parts; does the NA motor have reasonable forced induction cam options? Or maybe just clocking the cams slightly differently using adjustable gears? Changing the pressure differential can help too; focus on optimizing exhaust flow on the hot side, focus on keeping velocity up and reducing total surface area (aka: reduction in plumbing length) on the cold side. Also consider cooling modifications; getting air to pass through the intercooler more efficiently can be an easy win if you know what you're doing. (eg: do NOT build a "funnel" to your intercooler, it doesn't work that way.)

Had to create a new profile, can't seem to get it to send me a password reset.

I never said the car was well tuned or efficient, I simply stated the facts of the setup. You made the assumptions there, so what exactly am I lying about? Yes a FMU and retarding the cam sensor "works" but isn't a desirable option for more power. But, to it's credit, this is the out of the box solution that Greddy themselves includes with the install of this kit when it was new. My question giving what I'm already working with - what is the smartest route for 250whp goal?

-MS PNP
-Bigger Injectors
-Actual FPR
-Bigger DP
-ARP Head studs
-Built bottom end?

I appreciate the information in the last paragraph, I'm planning on a new front mount setup with simplified piping compared to what I pulled from the car.

250 is pushing it with a Greddy and a 1.6. Lots of people have done 220ish though.

As to your list:
-MSPNP ==> Yes
-Bigger Injectors ==> Yes
-Actual FPR ==> Not needed. Remove the Greddy FPR and use the OEM.
-Bigger DP ==> Yes
-ARP Head Studs ==> Yes
-Built Bottom End ==> Don't waste money on a 1.6. If you plan to do this (highly recommended for real 250+), then you should go ahead and 1.8 swap.

You need to upgrade your diff.

Forgot to update - I just picked up a torsen 4.10 with axles and shaft out of a 95 1.8

I know you didn't. You asked what you were making, I gave you a example of how to guess, and I stated that my terrible guess was also based on terrible assumptions. What the hell dude, where did I ever say you were lying? Specifically, I said that you weren't lying because your rig has held together for so long even after an autocross, which pointed to it being entirely effective if not efficient. Jesus shit man, chill out. I drive a Miata too, you know?
Hornetball beat me to the punch, so I'm just going to start with "yeah, do what he said."

Go MS3 and MS3X, pay attention to the quality and balancing of the injectors you purchase, skip the AFR, go big on the DP and pay some attention to the wastegate dump + merge into the DP.

And I also agree about the 1.6 based on a shit-ton of reading in this forum: don't throw money away on that mill. If you're aiming for 250whp, nuy a used 1.8L, freshen the cylinder walls, do a VVT swap, grab some upgraded FleaBay rods, drop compression a bit with a different set of pistons, tune like a bauce and boost until you're blue in the face.

NC idiot statement time: I thought I remembered the 5spd was the stronger transmission option for the NA/NB series, at least until the Asin 6spd showed up in the MSM's. EDIT: NC idiot statement indeed :D Sounds like the Asin 6spd showed up in '99, and is the strongest transmission option available to you. If you go 6spd, you'll want a taller final gearset in the diff. I believe there's a 3.63 Mazda-stock RP option floating around in the wild for your setup.

Sorry, I didn't type that to come across as sounding like I was pissed. I was just repeating what you typed - nothing meant by it.

So you're a fan of the separated gases DP that merges farther down the line?

From my research, the 5speed in the 1.8 NA has a better second gear synchro than the 1.6 NA trans, and may use a two pin shifter bracket vs. a one pin in the 1.6....but otherwise they're essentially that same.

This is all great information, thank you for the input!

For folks running external wastegate, yeah. Now that you mention it though, I don't know if you're running an external wastegate. Bad assumption counter ++1.

Everyone has opinions on how important the "smaller things" are: spending time on efficiently sized intercooler, keeping cold side plumbing to a consistent diameter and to a reasonable minimum length, attention to detail on head -> manifold -> turbo plumbing specifically with runner length, diameter, merge collector, wastegate methodology, also downpipe diamager EWG merge method, blah blah blah.

What I generally find is that most people see all of these things as "small changes" compared to the overall power you'll gain with boost. Rather, what I see them as individual small opportunities that, when combined, result in an overall more efficient way of achieving a similar goal.

I could produce 240whp on 18 pounds of boost by just tossing a ton of parts together, or perhaps end up with 240whp on 15 pounds of boost by paying more attention to the details -- taking longer, perhaps spending more, but the result being less heat, less boost, and a more efficient result.

My methods are not universally praised :D and therefore will not necessarily reflect the opinions of others on this forum and elsewhere.

5 speed is weaker. Asin 6 speed showed up in 99.

Thanks aidandj for the education; I've now edited my post accordingly :likecat:

What a beautiful color for a valve cover.


Now swap in a v8

FTFY :party:

Too bad, it's the better way of doing it. My OCD won't let me cut corners which is why I want to do it right the first time.

Hey I like it. It was a brighter pure white but the clear I used glazed a bit and now we joke that my valve cover looks a perfectly light toasted marshmallow in certain light haha.

FTFY&Me

When I read blown v8, I thought instantly, a destroyed crying shredded piston.

1.6 can make 240- 250 whp "relatively" easily and safely.

We ran up to 270 but it was definitely getting a bit hairy and close to the edge of easy and "relatively" cheap to run so pegged it back to 250 ish....

A 1.6 Miata running 250 HP at the wheels is a very quick and fun race car that can humble many more powerful and exotic cars.

you will be under intense pressure to swap to 1.8 here but it isn't necessary for your goals.

If a 1600 is what you have, run it till you use it up would be my suggestion. Only additional cost that you will not reuse when / if you swap to 1.8 is the manifold. Any downpipe you use will be easily modded to suit 1.8 by a competent exhaust shop.

Small T28 or big T25 on a 1.6 will get you to those figures. Decent injectors, Intercooler and ECU are all required but will swap over to 1.8 if you ever do upgrade. Despite what people say, the stock coils are perfectly adequate on either motor.

6 speed is a must around that power level.

I really like it