Engine Management
 

I am planning on turbocharging my Miata this weekend. It is a 1996 1.8l. I have been researching it for a couple of months, and I have a couple of questions. I plan on running very low boost (3-5 psi) just because I have an older car and I am just looking to make it a bit quicker. I have been reading the miataturbo wiki, and from what I gather the only engine management I need it an adjustable fuel pressure regulator, is this correct? Is there any way I can go about setting it up without a wideband o2 sensor? I hadn't realized one was necessary, I have a narrow band air to fuel gauge installed now, but I was told it was useless. Is a wideband o2 sensor 100% necessary, or can I get my Miata tuned with a narrow band and just by adjusting the afpr? Also, do I need an intercooler for such low boost? I have an intercooler, just not the piping. I was planning on running it without one for a while, and eventually I might get to putting it in. Bad idea?

Sorry about the wall of text, just trying to get a bit of help. BTW I am not completely alone on the install, a friend of mine will be assisting me, I would just like to gather a bit of information myself before I take the plunge installing it.

Thanks!

EDIT: Just to be clear, I am not worried AT ALL about getting 100% out of my turbocharger. I just want the car to be reliable after it is installed, and I am worried that without the wideband o2 I will not be able to tune it properly.

No you don't need an intercooler at those pressures and you do need a wideband or tuned on a dyno that has a wideband.

Great, thanks for the fast reply!

Is there any way I can make the car safely drivable until I can get the car dyno'ed? It is my only car so I want to be able to drive it safely until I can get it there. And would I just be better off buying a wideband and doing it myself?

Put it on right before you go to the dyno and drive out of boost to get there or get a wideband.

OK, just one last question. Do you have any estimate on what it should cost to get the car correctly tuned from a professional? I believe the only thing needed is to set the AFR correctly, but I may be mistaken.

You might want to look into MegaSquirt, just do an advanced search and think it over.

$200-300 for the AFR tuned on a dyno. Remember you have to retard timing 6* if using a pressure regulator.

Is that necessary when running such low pressure?

Sure is! Also, there's not much tuning they will be able to do if you all you have is a fuel pressure regulator. The stock greddy turbo kit uses no intercooler or engine management. It runs just under 5psi, and it uses a rising rate fuel pressure regulator to deliver more fuel. It also states that the timing needs to be dropped on the motor to 6 degrees TDC. You also will want to upgrade to 91 octane fuel.

https://www.miataturbo.net/attachmen...7&d=1109983009

Also, do you have a wastegate that will run 3 or 4 psi? That's pretty low for a wastegate to be down to. Most are going to start at 5psi or more.

So all I need to do is drop the timing to 6 degrees and I can use just the AFPR for the engine management?

And as for the wastegate, I bought a manual boost controller, when I purchased it I assumed that it would allow me to drop the boost lower than what the wastegate was set at. Am I incorrect?

Just to be clear I have an external wastegate.

You use a boost controller to raise your boost. You can't go lower than what your stock wastegate spring is set to. And as far as the AFPR, it will still need to be adjusted to make sure you are getting the right amount of fuel into it. On the greddy kit they did all the tuning and included a FPR that was meant to give the proper Air/Fuel ratios. Because yours is just a generic adjustable one, it will have to be dialed in.

Would I be okay driving the car ~20 miles to the dyno if I have a new 4psi wastegate spring, untimed ignition, and my afpr set near what the stock would be? I'd rather pay to have the ignition timed, but if I need to do it myself I suppose I can look into it.

Look you 100% need a wide band O2 sensor. They cost less then you will spend at the dyno. Only after you get it installed and get used to watching afrs stock should you even considering putting on the rest of the kit.

Somebody here once compared building a turbo car to the scientific method, when you test a hypothesis you don't have more then one variable at once, same with a turbo build. Do it one step at a time, see the result and make sure everything is as it should be before you go to the next step. Also, be prepaid to spend money in order to do things right. That seems to be a recurring theme here.

Which is more expensive than a wideband purchase.

Buy an AEM Eugo. They are $200 shipped.

Set the timing yourself, it is very easy. Do a search.

You should also have a boost gauge to make sure you are not overshooting your target.

Seriously, if you are gun shy about setting your base timing, there's no way in the world you should be putting a turbo on your car.

Yeah you should be fine provided you don't go near making any boost, just drive it like a slow poke. Also I suggest from now on using 91\93 octan. If you haven't already fill your tank with 91\93 and run out whatever 87\89 octane is in before throwing the turbo on it. Also if you never do invest anything else I suggest alteast invest in a J&S safeguard latter.

Thanks for all the help. I guess my plan is to order the AEM wideband kit for 200, buy an ignition timing light, and do everything myself. And the safegaurd latter sounds awesome, but is there any options that are any cheaper? I've dropped quite a bit of money into my car as it is, but it seems like a solid investment. Thanks!

I would skip the AEM and get a SLC DIY, same price and offers way more features with it or if you don't want to DIY.
I would look into the new innovate product, MTX iirc.
http://www.diyautotune.com/catalog/i...844-p-467.html