Neon01

Hey all, new guy here. First a little background on me - I'm an engineer working government acquisition (education is aerospace and systems eng). Love cars, have a problem buying and selling too many, have been a BMW nut ('99 M3 track car, '04 M3, '03 330i ZHP, '05 M3, and now '09 M3 sedan over the last 7 years) most of my adult life. A friend of mine did a DIY turbo miata build some years back and really got me interested in them, so (finally) here I am. I've had a small amount of wrenching experience - notable jobs include a turbo rebuild and full hose replacement on my '88 RX7, brake system replacements, sway bar installs, and probably the biggest was that I had to rebuild the entire top end on my '99 M3 track car when I bent some valves money shifting it in turn 17 at VIR full course.


I've been looking for a mostly-built turbo miata to be a daily driver to keep miles off my M3 and be a fun/project car. I recently found a car on the classified section on this board and after lengthy talks with the owner I've put a deposit on it and pick it up this Friday.

Here's the one, FYI: https://www.miataturbo.net/cars-sale-trade-6/1994-mazda-miata-%246500-58322/

I have to thank the seller for his extreme patience with me - I'm a very picky buyer and I've asked him dozens of questions, requested pics, compression tests, the works. He's responded to all of my emails and phone conversations with nothing but patience and understanding. At first glance the car appeared to be something of a Frankenstein's monster, but after talking with the owner and seeing how fastidious he is and his great knowledge of cars (he works for Borg Warner), I feel a lot more comfortable. His build thread is here: https://www.miataturbo.net/diy-turbo-discussion-14/1-8l-diy-turbo-set-up-borgwarner-efr-6258-a-56871/

My goals with the car, as I mentioned before, are reliability and a fun car that I can daily drive and take my son out in for back road rides. Maybe occasional auto-x too. My M3 is for the track though, so I don't see myself tracking this one.

My "to-do" list for this car is pretty long - first thing is to reinstall the AC as he is giving me all the components. I'm sure I'll be posting in the appropriate forums asking for advice soon, but in the meantime, glad to be here!

samnavy

iTrader: (7)

No pics, no location in profile, no signature... is this your first ******* time joining a forum? HAHA, welcome NOOB, fix your **** or suffer my rath!

Nice buy on that black one... v-band DP FTW. Already tapped for EWG as well, and those charge pipes are huge. Be sure and let us know how it runs when you get it.

Neon01

Seeing as how I don't own it yet (technically), I figured you'd give me a pass on the pics and sig I'll fix the profile though.

Sorry for the ignorance, but what's a v-band DP? And I believe the turbo has an IWG already, is it really beneficial to change that to a EWG (and can that even be done without switching to a different turbo)?

Will do on checking back in.

samnavy

iTrader: (7)

Dude, pics of your M3, who cares about the Miata!

The downpipe is held to the turbo by a large t-bolt clamp, instead of a bolted flange. This is generally considered superior. The turbo had an INTERNAL WASTEGATE (the long rod connected to the small can mounted to the turbo itself) mounted, where the wastegate itself is internal to the turbine housing on the turbo. On the manifold, you can see just aft of the turbo between the #3-#4 runners, a blockoff plate. The plate is where you would mount your EXTERNAL WASTEGATE.

You can convert from internal to external by welding the internal wastegate flapper shut, and then mounting an external actuator to the manifold. The dump from the external wastegate is then routed through a separate tube into the downpipe. External wastegates usually provide superior control over boost, especially at higher boost levels (15+psi). If you're not seeing any boost control issues, then leave it alone. Common boost control issues are spikes and creep. Even at that, often a different actuator can help.

93BP-T

V-band FTW! Im in for pics as well and nice score on the miata
Welcome.

Neon01

I see, thanks for the info re: exhaust and WG, that's good news. I know a (very) little about wastegates and their function, but didn't really give much thought to converting this to an EWG setup - maybe I will though. Also, it seems that if you weld the WG shut on the BW turbo that's in there, that might impact resale if I want to switch someday. Couldn't I basically achieve the same thing just by disconnecting the vacuum line from it? After all, it's essentially a large spring in a can that's keeping it shut without the pressure to open it, right?

I'll probably be turning boost _down_ if anything, to decrease the likelihood of blowing up the motor - which is still running with stock internals. Compression numbers averaged around 150 psi with a max differential of 12 psi, which seemed decent, if a little on the low side. I'm gonna try to start setting aside money to rebuild the motor in case it does go (or before ).

I've attached some pics of my current ride that I snapped at a local meet recently.

samnavy

iTrader: (7)

If the wastegate spring was strong enough, it could theoretically hold the actuator shut, but in reality, the energy of the exhaust flow will force that door open, which will kill boost, and therefore energy in the exhaust... actually, I'm not sure what would happen.

How a wastegate works is basically:
At idle and up to a certain psi, all of the exhaust flow is routed through the turbine housing. The wastegate actuator provides a path around the turbine housing, letting some of the exhaust gas bypass the turbocharger completely (in an external setup), or simply routes it around the turbine wheel but still inside the turbine housing (internal). The wastegate actuator, whether internal or external is held closed by a spring that is on one side of a diaphram inside the wastegate actuator can. The other side of the diaphram is open to boost, either tapped into the compressor housing, charge pipes, or intake manifold. When that line becomes pressurized, it forces against the diaphram and compresses the spring, pushing on the rod and opening the wastegate, allowing some exhaust gas around the turbo.

shuiend

iTrader: (24)

According to some test that have been done on the EFR the internal gate can hold something like 30psi. You will not need to convert to an external wastegate. I have seen that car in person and it is an ok setup. I think the power it makes for what it is is awesome.

stratosteve

iTrader: (1)

Forest Hill....I am ~25 minutes from you. Check out lowes in abingdon on a friday evening. Your son would probably love it (if he likes cars).