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Old 03-29-2008, 06:39 PM   #1
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Hi all,
I just purchased a 90 turbo miata this week. All in all it seems like a great car, but I have one issue I need to ask about. Thought this would be a good place to do that. It has a Greddy turbo and intake filter, vortech, JDM catback 2.5" exhaust, Racing beat suspension, tokico shocks, Racing Beat front nose and skirts, carbon fiber hood, aftermarket 15" tires and wheels, blah blah blah. The PO spent a bunch of money on the car and I guess lost interest, so I got a pretty good deal I guess. I am in NC, between Charlotte and Asheville. The turbo needs a heat shield or blanket, right now I've just got some insulation over it to protect the M/C and heater hoses. When you get on it, above 4000 when the turbo kicks in it seems to pull pretty well all the way to redline, but if you floor it, it will spool up, then buck like it's running out of fuel, it will go up, then buck, up, buck, in a cycle. If you back off a bit, it smoothes out. I asked the PO if he had this problem and he said it needed 1.8 injectors, the stock ones wouldn't flow enough fuel. This makes sense to me, but I thought the Greddy base kit only was 4-5 psi and that the stock injectors were sufficient. I don't have a boost gauge installed yet, so I don't know what the boost is. Could I be building more boost than the 4-5 psi? I'm a little confused about if the boost stays constant if you let off the gas a bit, or does it change. I guess I'm asking is boost constant with rpm only, or is it dependent on throttle position AND rpm? Could it be afm related, I don't think there is a blow off valve anywhere in the system, do I need one? What about fuel management or timing controllers, I've read the bipes is programmable. I don't have any literature on the greddy kit, so I don't know what all is changed from the stock configuration and where to start troubleshooting. Any suggestions would be appreciated. I've been browsing the faq area and doing some searches, but haven't found exactly what I'm needing, so I thought I would ask here. Any install literature on the greddy would be great. Also any miata members in the Shelby, Forest City, NC area give me a yell, I'd love to meet some of you and get some tips and tricks.

Thanks, Richard G.

Last edited by rlg999; 03-29-2008 at 07:40 PM.
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Old 03-29-2008, 07:29 PM   #2
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First of all, welcome to the forum Richard. Too many questions in your post to be able to answer all and besides I wouldn't consider myself knowledgeable on the subject anyways but I'll try to at least start answering some.

- You mention Bipes; do you have one installed?
- You also say you don't see a BOV; if that's the case you have to get one.
- Maybe you do indeed have problems with your injectors but first you have to at least find out which ones are in there right now.
- I see you live in NC; let's see if Dan (zabac) can chime in here (he also lives in NC) and assist you.
- You need to get yourself a Wideband sensor to at least know how is your AFR.


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Old 03-29-2008, 07:34 PM   #3
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One of your problems is your talking about the Bipes and fueling. The Bipes is adjustable but it's a timing device and has nothing to do with fuel.

As for your fueling, your probably using a AFPR and you need to find out what boost level your running so you can then get a FP gauge and figure out if your fueling enough. Or better yet get a WB and just see what the AF really is. Your 1.6 injectors should be fine up to about 6 psi if you are running enough fuel pressure.

Start with a boost gauge so your not guessing what's happening and then start from there.
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Old 03-29-2008, 11:44 PM   #4
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Yup, need boost gauge. It's quite possible with a 2.5" catback that you're getting a little more than stock Greddy. Boost gauge first. If there was a BOV, you'd know it.

Then, take a look at your Bipes. Go to this website:
Go to Programming Instruction, look at the back of the Bipes and check what the switches are set to and report back.

You need to check your timing.
You need to verify the ratio disc in your Vortech FMU... probably stock.
You need to pull your plugs and clean/gap... or just replace with one step colder now as you're gonna turn up the boost in the near future.
What condition are the plug wires in?
You need to subcribe and post some good pictures of the engine bay, or upload and link them from photobucket or another online media storage. NO CEL PHONE PICS!

Boost will be generated when you place a load on the engine. If you're not accelerating, there's no load, so no boost. The stock Greddy really requires you to dip into the throttle pretty good to get it to spool up. But simply cruising on the freeway at speed there will be no boost present, as simply maintaining speed doesn't really load the engine.

There are plenty of guys in NC on this board. Start a thread in the Localize Yourself forum asking for help and hopefully somebody smart and local can come over and help you out.
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