Building B6T need opinions
 

Hey guys,

Im hoping someone can give me some advice for a project im building. I just picked up a 1988 323GTX which has the B6T in it. The motor is currently blowed up. Yesterday I picked up a 93 B6ZE out of a Miata with a manual in it. IIRC the CR with the MTX is ~9.4:1 whereas the Auto is 9:1?

The motor that's in the 323 is a 7.9:1 motor and it will run 15lbs boost with the stock intercooler all day long. Im on a budget now and im wondering if I can run the turbo on the B6ZE with lower boost or if I should pull the low comp pistons and bottom end stuff out of the the old B6T?

Thanks for any replies, this is my first turbo motor I've done and need all the help I can get :)

Nice first post. Let me direct you to the search function. It's in the top right of you screen. It has magical powers.

I rebuilt the engine in my 323 GTX using miata pistons (9.4:1 variety) on the GTX rods in a miata block. Here are my observations, your results may be different.

I have to pull so much base timing to keep it from knocking that I haven't decided if the higher compression pistons are worth it or not. Right now i've got the distributor retarded as far as it will go, ~8*BTDC base timing. I'm still getting a slight knock at high rpm/high load. However, i'm just running the base 7psi right now. I'm running plug wires that are older than dirt and need to work on the gap for my plugs and probably still have some shitty old gas and still haven't replaced the probably ancient fuel filter.

My conclusions so far are that if you plan on going full stand alone (I do) in the future, go ahead with the miata pistons. If you intend to keep the stock GTX engine management, even just a re-flashed chip, maybe dont upgrade the pistons. 15psi is probably going to be just a bit too much.

My conclusions may change after I drive the car more though. I've only racked up about 30 miles on the new engine so far so there are lots of possibilities for my ignition issue that you may not encounter.

He posts on club protege so i'll vouch for him. He's asking something that isn't as easily answered as you might think.

I have been thinking about going with MS but I haven't decided yet, right now I really need to get the car running ASAP. So if I can use the B6ZE for now to build up the B6T anmake it bullet proof then I will. But I don't want to do this twice as well so im kinda torn.

I was planning on swapping the long nose crank as well as the GTX rods to the new motor. Oh and as for the turbo its got a IHI VJ-11 on it.

Thanks :) it seems like mt.net gets more daily traffic then CP aswell.

If it were me in your shoes, I would do one of two things:

1. Swap over the low comp pistons if they are salvageable.

or
2. Disconnect the WG actuator and run with no (or very little) boost until a proper motor is built or you can get some real engine management.


It depends on a lot of factors, but if this is just about making the car run while you build a beastly motor, I would go with #2. You get a car to drive with minimal work.

I honestly don't mind doing the work, its what I do for a living my family owns a shop where we rebuild and build custom show cars. ;)

Isn't there a way I can adjust the wg to open earlier to keep the boost down or even a manual or electronic boost control?

You can't go lower than wastegate pressure (in theory). Shimming the actuator will lead to less boost, but it will also make the car run like dogshit as you will never have a proper seal.

If you don't care about the work, then just rebuild the b6t or throw what you can into the b6ze. Thicker rods and lower compression pistons in a turbo motor are never a bad thing (within reason).

What exactly is "blown up" on the motor currently?

I just went for a drive and cannot detect any more detonation at all when hauling ass up a freeway onramp all the way to redline. I'd say the old gas is starting to get burnt up. Go with the miata pistons and GTX rods with the long nose crank. Re-ring, new bearings, a quick and dirty hone and you should be good to go. Thats how i've built both my miata and GTX and both run great. Actually, I didn't even hone the miata motor. Just threw on new rings and bearings and it has great compression.

Try at stock boost first then turn it up gradually from there to make sure you aren't going to induce any detonation. Just dont forget to turn down the distributor!

My car as it sits..... Is running Auto Pistons on Stock Miata rods. While being force fed a by a 2560R, the car at 10lbs runs like crazy. Although I am on AEM I get no knock or anything other than a slipping clutch. Thankfully my gtx decided that before I bought it to eat the rings. So now I have two options..... New/Used bottom end, or Gtx rods, rering, quick hone, bearings, oil pump.

The"blowed up" motor has no Compression on 2 cylinders. I think its cause the PO put the VJ11 on and messed with the wastegate to get more boost then necessary. I havent had a chance to pull it apart yet though, I think it was also over heated cause there wasnt much coolant in it when I drained it all out.

After thinking about it some more I think I am going to invest in an MS system. are there any suggestions for that? Im also thinking some 440cc injectors to go along with everything. but I still need it to pass smog

Well now you're opening a can of worms and its going to take some reading. Start here:

http://www.spitfireefi.com/files/GTX_MS_Install.pdf

Thanks for the link but im still not sure if its the best idea, Im just gonna stick with what I got and freshen up the B6ZE with some new gaskets the low comp pistons and gtx rods and the long nose crank. I just need the damn thing running and my stepdad is starting to get on me about it

well if this help...i have a mazda 323 with a b6t swap. IM running auto miata pistons, stock rods, with a stock vj14 for now. i rebuilt my motor, hot tank, bore .20 ova, honed, arp head bolts and rod bolts, 94 mx3 crank (long nose) all new seals and gasket, oil pump, t.belt and water pump. I have 460s tuned with vaf...runs rich in boost but car runs fine. Ill be going ms in a month or less.