Engine Rebuild Upgrade questions.

[ivan]

I have an NA and my 1.6 engine is apparently showing its old age since being recently turbo charged and I've been told to prepare for the day it goes. Coincidentally a friend of mine has an NB8 engine that had a spun bearing and is now in pieces.

My question is what components should I be upgrading if I decide to rebuild this engine?

My car is track only, turbo with 135kw atw, running 11psi. I don't foresee power numbers getting much bigger than this, maybe 150kw max. I want a reliable engine that can take the stress of track work. However, I don't want to fall into the trap of upgrading everything just because I might as well as the bill quickly adds up.

For labour and components I would put a loose budget of $1500-$2000 (not inc the cost of engine).

Of course new seals and bearings would be on order, but what of things like forged pistons, rods etc. Are they just a waste of money at the power levels I'm working with?

Also, with the megasquirt pnp, can I retune the car using the existing computer?

[davekmoore]

Some parts for serious boost will cost less than Mazda parts, so you might as well have the better ones. Standard rods bend once you go much above 11psi.

This thread might be worth looking at:

viewtopic.php?f=44&t=58784&p=758820#p758820

[emily_mx5]

i would source a good condition low km NB8A engine and swap that in, and not bother about rebuilding an engine.
it is incredibly expensive, and really only worth it if you "need" the strength.
150kw is totally fine on a stock motor.

MS (or any ecu for that matter) can be retuned for whatever your new needs are.

[project.r.racing]

However, I don't want to fall into the trap of upgrading everything just because I might as well as the bill quickly adds up.

This sentence defeats the whole purpose of the thread. If you dont want to do upgrades, then just buy another low km engine.

[spikes]

As emily_mx5 said, it would be wiser to get a low k NB8A engine and swap it in.
Flyin Miata sells a complete kit to do the swap.

Stock internals can handle up to about 210kw, so for your 150kw goals you will be fine.

[project.r.racing]

Just realized after a reread that you are thinking of going NA6 to NB8A engine. Just remebers that you exhaust manifold will need to be different. You exhaust will also need to be lengthened due to the turbo dump being slightly more forward in the car. Just some others costs involved that may not have been thought of.

[hks_kansei]

If you're going to get a shop to rebuild the engine, and you're upgrading, $1,000 won't go that far.

My GF has a quote to rebuild the bottom of the engien in our other car (non MX5) and it's just over $1k
That includes:
Acid dip, Bore, hone, deck block+head, bearings, cam, pistons, rings, rods, replace bolts/studs, balance, assemble.
That's using factory stuff, so no upgrades like forged etc, and only includes the bottom end. The head is our problem.
It's also a lot less complex than an MX5 engine (and he got a box of loose parts, so no need to pay for disassembly)


And yeah, as Ryan said, also budget to have to re-do manifolds and probably a heap of pipework.
And since you asked if the megasquirt can be tuned, I'm going to assume you'll need somebody to tune it as well (which means either pay a shop, or find a local guy to volunteer)



What is the B6 doing that makes you concerned?
Wouldn't it be better (if cost is a factor) to either give it a quick tidy, or just replace it with another one?

[bigdog]

Everybody throws about horsepower figures in relation to engine longevity - IMHO it's more about your boost curve and torque figures - you can damage an engine without making large power numbers. The weak point in our engines is the rods, and a good set are not too pricey (I'm using Eagle rods from the US for example), so I would look at doing that at a minimum. The rest is up to you and how far you want to go. I would budget $3500 - 4000 (if you are getting a shop to do the machining and assembly, an includes you buying all the parts) if you want to replace rods and pistons with upgraded parts, this would include a full set of ARP studs and bolts and all your gaskets, belts, hoses etc. My own rebuild cost me $3000 in machining and parts, I had Wilkins Engineering do the machining and bottom end balancing and assembly, I did the head and final assembly myself. Remember there always little things that you haven't allowed for that you find along the way too

As others have said, a standard NB8 motor can handle turbocharging quite successfully (so long as the boost curve and torque curve are reasonable), so it's really up to you.

[ivan]

many thanks for the information people.

My first thought was just to get a low km NA6 engine and call it a day. Then my mechanic suggested I may as well go NB engine if I was going to replace mine (he is experienced with MX5 and said it wouldn't be much more work).

Then...I called my friend who I knew had an engine lying around and he told me I could take it for free. As mentioned it is currently disassembled, but complete.

That's why I'm tossing up a few different options now. Considering I have an NB engine for nothing and could potentially be just a spun bearing, I am wondering the cost of doing a mostly standard rebuild with some upgrade parts if they will improve longevity.

If I could rebuild it for say $2k then I would prefer this to spending over $1k on a low km engine that could have a problem with it.

Dann, can you confirm if new log manifold and dump pipe would be required?

[ivan]

hks_kansei,

The engine actually feels fine to me but on dyno the power curve is showing something strange up the top end. It's in my garage thread and i think there is a dyno chart there. The tuner thinks the engine is just a bit tired and plays up esp when it gets hot.

[NitroDann]

Yeah you will need a new log and POSSIBLY dump for a 1.8L swap.

Dann

[greenMachine]

hks_kansei,

The engine actually feels fine to me but on dyno the power curve is showing something strange up the top end. It's in my garage thread and i think there is a dyno chart there. The tuner thinks the engine is just a bit tired and plays up esp when it gets hot.

Unless it is in the hydraulic lifters (which I know stuff all about), that sounds more like an ancilliary problem rather than a pistons, rods, rings problem. Chasing these can be time consuming, tricky and potentially expensive if it is last thing that you replace that turns out to be the problem. On the other hand, what you are considering is not cheap either.

It could be plugs, leads, coils, sensors (esp cam/crank), O2 sensor (if you have one), ... If you elect to stick with the B6, you have little to lose by stepping through those (and any others that you can identify), as you will be able to reuse whatever is replaced but found not to be the cause of the problem. Alternatively, you may be able to borrow components just to try out, which obviously reduces your costs.

I am assuming that the problem can be replicated fairly easily - if not the choice narrows.

[NitroDann]

I agree with green machine.

Dann