93 protege 1.8 BP build
 

I'm building my first motor, it's not going to be for any type of racing other than maybe taking it to a drag strip every now and then to have some fun, and drive to work a couple days a week.

When I started the project I was wanting a turbo, but after some research I've learned I haven't learned enough to take on that much of a project yet. So this is going to be a NA motor with plans for a turbo in the future, wether it's 6 months or a year from now.

After looking around here and a couple other sites, I have some questions about the block and head work that needs done.

I took the head in yesterday to a machine shop adter I disassembled it and cleaned it. They are supposed to mill it .020, grind the valves, do a 3 way valve job, and I went ahead and gave them the new stem seals to press in for me so I should have a good seal on the head.

The block is sitting in my garage and I'm takimg it apart this week. The whole motor only had 90k miles, which is the least milage engine I've ever owned lol..

Anyway, while the block is apart, I was wondering what work I should do to it. When it gets boosted I'm going to run 12-14 psi, which is modest compared to most of the performance motors here.

I was considering boring the cylinders a little oversized, but what would that do to my compression ratio and more importantly, the squish volume, if I kept the stock pistons and rods and used new oversized rings.

I've already ordered a pnpMS unit for the protege, which is probably a massive overkill for an NA motor, but I do eventually plan on boosting the engine, and I dont have stock ecu anyway.

Thanks for reading, feel free to criticize, as long as you throw some good info my way in the process!

DX or LX : SOHC or DOHC ?

I dont know all the differences between the trim levels, but the motor is a dohc from an automatic with a 4 wire tps. I'm matching it up to a 5 speed transmission, and from what I understand, you can just omit a wire on the 4 wire tps to have it act as a 3 wire tps. Also keeping the stock intake w. Vics

Wait, what? Oversized rings? Boring cylinders to change compression ratio?!??!
How did you come up with this stuff.

If you want turbo in the future, you pretty much have to put upgraded rods in it.

Also, "I'm going to run 12-14 psi on it" tells nothing. You could run a small turbo with 15 psi all day long, but a GT30-sized turbo at same 15 psi will bend your stock rods. Gauge horsepower and torque - not psi.

The LX had the DOHC, the DX had the SOHC.
The G25 5-speed from the LX (which is not the same transmission internals or ratios as in the DX, it's stronger; G25 has the same gears and ratios as the Miata 5-speed) will come apart at the boost levels you are anticipating. If you boost at all, you will need a stronger clutch. If you drag with boost even the G25 will probably grenade. The LX and G25 had stronger axles,
even length axles to reduce torque steer, bigger anti-sway bars, etc.

You can spend and break, spend and break,,, or do a lot more research first.

VICS adds noticeable torque at the low end.

How do I know? I still daily drive the '93 Protege LX I bought new and I have the factory shop manual which details all the differences between the DX and LX. The G25 transmission has a separate section from the pedestrian 5-speed in the DX.

If you click this link, it will give you an option to choose oversized rings... it's not anything new. I'm pretty sure people have been boring out cylinders for generations, are you saying it won't affect compression or more importantly, the squish volume, which I don't pretend to know anything about myself because I don't understand it, at all?!

I should have stated my power goals were somewhere between 200 and 230 hp, and to get to that, I need 14 psi, but I don't know how things will turn out, I'm new to turbochargers, but I do know bigger is not necessarily better.

I don't see why I couldn't keep the stock rods, there's only 10+ guys on clubprotege running up to 18 psi on stock rods..why couldn't I?



I know about the G series transmissions, I'm ordering an MFactory differential next week... or as soon as I start to see light at the end of the tunnel for this engine work.... and right now I've got a 2002 Kia Rio 5 speed that bolts to the BP. I'm going to attempt to match the mfactory diff up to its' ring gear, but if by chance it doesn't work, I'll find a Mazda G series somewhere.


I don't really know which way to go with any of this, I could find something else out and change my mind in 5 minutes, or tomorrow..but from what I've seen at Festiva Meets, and what I've read online over the last 2 years, this is the best way I know of going about this. I figured it would be better for me to post what's on my mind, because as stated in a previous post, "I'd rather take a verbal from a nerd with a big e-peen than spend hundreds, or thousands of dollars on stuff I can't use or return." So please, if you have constructive criticism or better ideas, I'd love to hear your thoughts.

You don't need 14 psi for that...well yes and no. It is all turbo size dependant. Small turbo (SR20) 14psi will be most likely between 220-240whp. Bigger turbo (3071) 7 psi might get you at that same level.

Slow down man. oversized rings are for oversized pistons. You said "I want to use stock pistons". I understand that as you want to reuse your old pistons. That just doesn't work that way. If you bore a block, you need pistons for that bore size, end of story.

Now, Miata rods get bent sometime after 250 ft/lbs at the crank. Again, psi doesn't matter. TQ/HP matters. Stock rods are the weakest bottom end part.

i ran a overboosted fwd bp in a mx-3 for years, DONT go above 250whp, it just kill all the fun.

i say dont build it, MS+turbokit,tune it to be super safe@200-220whp, and just enjoy the thing.my 0.02$

Ah hah.. Now we're getting somewhere, so a hone job and fresh rings are probably the best way to go. I dont know why I always thought rings were made thicker/wider but I know better now.

The goal for this car is for me to build a car thats like new, I've already done most of the body work and the suspension is almost all new except the rear struts. I want something fun and reliable, and I definately cant shell out 20-30k for a new car.

If I were you I'd leave the bottom end alone. Rebuilding it is costly, takes time and isn't really needed for your power goals.