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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 07-31-2008, 01:43 AM   #1
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Just a forewarning I am new to having a turboed car so any tips would be helpful, but this is my second Miata.

I just bought this last week and it came came with a turbo, but when i checked under the hood i found a horror. so I took it in to fix it up and give it what it needs. I had the exhaust made yesturday and it turned out better than I could have imagined. So far I have a HKS SSQV on order and an intercooler and piping from a friend. should be ready to go on by this weekend. Here are some pictures of the car with its crappy pvc setup that came on it.




I need(want) this out, any recommendations, its an AFM from and RX-7






Nice dual tips sounds great


After I have the setup finished I will more than likely need the turbo rebuilt to fix any damage from driving without any blow off or by-pass valve.

But before I go for the night I have a few questions for all of you.
  • What temperatures should I be looking at right out of the turbo? I saw it reach 1,200 so just wondering because its starting to discolor the paint on the hood.
  • How steady should the A/F ratio be? Im not sure where the gauge pulls the info so i'm not sure how accurate it is either.
  • What would be the best Idea for the AFM?
  • I am looking into a Megasquirt ECU, but is it really worth it? The car is in really bad need of a tuning the way it is now.
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Old 07-31-2008, 03:08 AM   #2
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Yes, go megasquirt. Mspnp is easy, relatively cheap, and very effective. Do it.

You can even recoup some of the money by selling the FMU/AFM.

Other than the clusterfuck under the hood, looks like a clean car. Dont worry though, sounds like you are on the right track.
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Old 07-31-2008, 10:19 AM   #3
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Yeah, it doesn't look too bad to me. You need to make yourself a heat shield- just search for it here, lots of examples.
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Old 07-31-2008, 10:34 AM   #4
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OK, it is a 1.6 car, so no emissions to worry about here in NC, go MS for sure.
There are a few of us around NC than could even help you out.

As far as the turbo, if it was running at the stock 5.5psi, that really doesn't call for a bov/recirc, I don't think you should waste money on rebuilding it, unless it really is blown and needs a rebuild.

Get a MS and a WB02, get the thing running smoothly and delete the AFM, and run new IC piping and you have yourself a nice little car.

ps-list your location in your profile and a short sig about your car.
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Old 07-31-2008, 11:03 AM   #5
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That AF gauge is worthless (narrowband)... and I wouldn't trust a VDO gauge any farther than I could drive over it. You need a boost gauge that also includes a vaccum side. The EGT is nice and you don't see one in hardly any Miatas, so you've got that going for you. I like the filter placement in the nose.

I agree with skipping the BOV for now. If you're sticking with 5-6psi, then spend the money on MS. You can VTA with the MAF still in place anyways... well, you can, but boost recovery after shifts will suck, as will anywhere in cruise, it'll buck and shake off boost if it leaks even a little.

Compression and leakdown tests are mandatory.
Buy some 1.8 tan-top fuel injectors from the classifieds.
Fuel filter.
Motor mounts.
Seafoam the intake.
And no matter what, DON'T TURN UP THE BOOST WITHOUT AN INTERCOOLER AND MORE FUEL!
Your brake fluid looks like sludge.

What kind of maintenance records did it come with?
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Old 07-31-2008, 11:35 AM   #6
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Sam, have you seen the enginebay, lol, and you dare say maintnance record? I hope you meant Home Depot reciept...


DXO-but Sam is right, you need to do all the basic maintnance before you go upgrading anything, and those gauges are worthless. When you buy MS and a WB02 you will get a real A/F gauge to go with it, Autometer vac/boost gauges are easily found in the classifieds every now and then. You cannot see those yet, but you will soon.
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Old 08-01-2008, 01:47 AM   #7
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Right now its just regular maintenance until I get the parts for it. The brake fluid was just changed this morning along with the oil, water pump, timing belt, seafoamed everything, etc

As for the turbo its not 5.5 like Zabac said. it pushes [email protected], but thats just where the wastegate cuts it off at, so im still expecting the bov and intercooler here tomorrow.

as for sam's responce i did get under the car today and took a look, I was expecting some wideband sensors but was really disappointed, so im going to try and track some down this weekend.
I have been looking around for some injectors, I have a friend who just upgraded the injectors in his RX-7 but didnt know if they would be the right fit.

I to like the way the air filter is atm but its going to have to be moved to install the intercooler, not sure where im going to put it. i took the cruise control out today so that gives me some more room to play with.

Oil cooler is strapped in all ghetto style in the front so it needs to be relocated.

I even thought about a 1.8 swap for some more torque. The guy was willing to sell it to me for $600 with only 100k on it.
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Old 08-01-2008, 10:30 AM   #8
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Definitively a project, but it should be a fun one.

Skip the 1.8l at the moment, that would put you pretty much back to nothing since then you would need a new manifold and re-work your DP as well.
Clean everything up first and get the MS in there, that should keep you busy for a while.
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Old 08-01-2008, 11:03 AM   #9
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Your manifold won't work on a 1.8, so unless you're going to upgrade, don't bother yet.

You need 1.8 TAN-TOP's from a 94+ Miata. It's been shown that the largest injector the stock ECU will idle are 330's. The common "large" injector we run around here are 305cc Toyotas becasue they're easy to find. You won't be able to run any injector from an RX7, they're too big.

I don't understand [email protected] Does that mean you're not hitting 10psi until 5k? I think I know why... 10psi non-intercooled IS A VERY BAD IDEA. I can't imagine what your charge temps are, but it has to be running stupid lean because stock blue-tops won't fuel past about 7psi on the stock fuel pump. Once you reach about 7psi, there's no more fuel... and more boost just means lean which means no power which means no spool. I'd also pull your cat and have a good look at the guts.

Tell me you've read the FAQ... It's the sticky at the top of this page... lots of good info you're either forgetting is in there or haven't read yet. Click on the FAQ and read the whole thing.
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Old 08-01-2008, 11:50 AM   #10
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Sam, he wants to run MS...

DXO-look at the part number on the RX7 injectors, and then search here
https://www.miataturbo.net/forum/showthread.php?t=10821
to see if they are plug and play.
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Old 08-01-2008, 06:29 PM   #11
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i have read the FAQ and im aware of it running very lean at the top end, im just saying the turbo is pushing that much so im getting a bov for it. Ive sourced some larger injectors for it and should get them next week.

As for the cat there is none. I replaced the actuator for now until i get the injectors, borrowed it from a friend. to keep it below 6psi.

Im constantly changing out things on it and only get to check this about twice a day so sorry if im slow to respond.
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Old 08-01-2008, 06:33 PM   #12
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Quote:
Originally Posted by DXO View Post
i have read the FAQ and im aware of it running very lean at the top end, im just saying the turbo is pushing that much so im getting a bov for it. Ive sourced some larger injectors for it and should get them next week.

As for the cat there is none. I replaced the actuator for now until i get the injectors, borrowed it from a friend. to keep it below 6psi.

Im constantly changing out things on it and only get to check this about twice a day so sorry if im slow to respond.
Smart move...you're going about it the right way, I wish I could criticize you, but so far so good. I wish I had some free time, I'd offer help, but I am moving this weekend and weekdays are a no-no for me, I work 12-15hours a day.
Maybe we can have a tech day sometime soon.
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Old 08-02-2008, 01:08 AM   #13
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thanks, i might could use some help on some things. My personal specialty is really with computers but cars have always caught my attention and I teach myself most what I know. I do have a really good friend that is a mechanic but he lives in Greensboro and only comes down on the weekends. Hes been lots of help with everything but like I said he isn't around. It's not been very long since I started working with cars and I can't say I know a lot, but I'm willing to learn all I can.
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Old 08-02-2008, 01:22 AM   #14
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Just take your time and read as much as you can on here, lots of very good information.
I go to Greensboro frequently, I am from there sort of...well, high point.
Where does your friend work, I may know him.
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Old 08-02-2008, 01:31 AM   #15
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City Electric, he lives in Jamestown and goes to GTCC for automotive. I get lots of contacts from there and a few more elsewhere. That hes really helped with everything.

Last edited by DXO; 08-02-2008 at 01:45 AM.
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Old 08-02-2008, 10:13 AM   #16
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I have just now got around to this vortech unit in the engine bay and was wondering if it is doing the engine any good or if it could hurt performance in any way

Here is the page for the unit:
http://www.vortechsuperchargers.com/...p=31&cat_key=5
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Old 08-02-2008, 10:28 AM   #17
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Old 08-02-2008, 10:47 AM   #18
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Salisbury steak today
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Old 08-02-2008, 05:47 PM   #19
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Nice project, to fine tune with some good upgrades.
And what a stupid people excist? No BOV will destroy your turbo in the end
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Old 08-02-2008, 06:05 PM   #20
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DXO, that Vortech piece is critical for fueling the engine.
The stock engine computer is not capable of adding fuel for the additional air you provide it when in boost.

Your year Miata uses a return-style fuel sytem... there is always fuel circulating through the fuel rail at a specific pressure. The pressure is controlled by a small device on the back-side of the rail called the FuelPressureRegulator (FPR). Fuel enters the front of the rail and exits the back through the FPR. Pressure is constant. The computer knows what that pressure is and is programmed to squirt the fuel injectors for a specific amount of time at a specific engine RPM and specific load to provide a specific amount of fuel for a stock engine.

When you add more air to the engine (ie. boost), if you dont' add more fuel, you run lean, then you knock, then your engine cracks a piston or throws a rod.

What the Vortech does is pinch off the return line to the tank causing pressure to build up in the rail. The computer can't sense the increase in fuel pressure, and continues to squirt the fuel injectors at the same rate it normally would. But since there's more pressure at the injector, you get more fuel... and that's the simplest way to mechanically increase your fuel. You'll notice a vaccum line running to the Vortech that's tapped off the intake manifold. There is a diaphragm inside the Vortech that pinches off the return line more and more as boost rises. You can increase fuel pressure in the rail only until the limit of the stock fuel pump is reached. 80psi for the stock fuel pump.

The diaphragm in the Vortech is adjustable in its' RATE-OF-RISE... meaning for every 1psi(boost)=12psi(fuel pressure above stock pressure) of 45psi(I think that's stock). You can get 6:1 8:1 10:1 12:1 discs to fine tune your in-boost fuel pressure.
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