Engine Build - Not sure if it will be NA or Turbo!

[daffyflyer]

Go n/a!!! mmmm! imagine a 8k screamer! get ITRBs later on

Yeah, I sold out

If I could afford a full all out NA motor I would, but turbo just looks too good

[Szemen]

JUDAS! jk jk.

So instead of buying 11.0:1, you'll be lookin at the 9:1's won't you? I was so lookin forward to seeing someone build a NA screamer so I can judge how much I need to spend

[daffyflyer]

Yeah, good point, but i think you can guess the price for a good NA motor is LOTS


Nah, not getting pistons anymore, going by carco's advise and using stock pistons with forged rods :>

[daffyflyer]

Off to the shed to decarbonise pistons/ports, and perhaps polish some casting marks out of ports/manifolds, Pics to follow :>

[Fuzzlet]

Wow this is the second time this car has made someone turn a simple rebuild into a turbo build....If you are going to keep standard compression ratio, I would go forged pistons. As Jeo said - Do it one, do it right. You dont want to have to rebuild an engine in 12 months because you've cracked a piston. Eg:

Initial build of my engine was gonna be approx $6 for a non turbo screamer. It went to $10k when I decided I'd run a small amount of boost through it. It eventually went to $15.5k when I wanted to be able to run higher boost in the future

[adamjp]

The main difference between NA screamer engines and turbo engines seems to be in the actual engine preparation.

NA engines need to have head work done to optimise their potential and the builders take this into account by spending $1000 to $1500 on head work. Turbo builders seem to think that head work won't get them anywhere so they don't bother, and spend $1500 on a turbo of some sort.

Camshafts are necessary for a good NA engine and they will set you back around $1200. They will also improve a turbo engine but many turbo builders skip this part to keep the cost down.

Pistons are pretty much the same price for both - although turbo ones tend to be more available.

Good rods are cheaper for a turbo engine as the heavier designs are needed for a turbo. For an NA engine it is all about engine speed so you want lighter rods that don't have to be quite as strong. Fortunately an NA can use carefully selected stock rods.

For the average $4k spent on an engine build, the NA donk will put out maybe 110kw if you are lucky. The turbo engine will be pulling 175kw. With head work it might go to 190kw or better and good cams will add another 15-20kw (yes head work and cams will improve a turbo engine more than an NA donk - flow IS flow).

If you are after the BEST you will spend more on a turbo engine than an NA - but you will have possibly twice as much power! As fuzzlet has indirectly pointed out, turbo power gets as large as your wallet will allow. IMHO $15k on an engine is too much, particularly when that much power will be stressing the rest of the drivetrain so much that reliability (read breakages) will be poor. But they be your wheels and your $$$.

And yes, I am still going NA.

[daffyflyer]

Thanks for all the info.

How weak are the stock pistons, how often do they fail under 10-12psi?

I have heard that it is mainly the rods that are weak, and the stock pistons are pretty tough.

I was only hoping for 120kw ish with the NA build so its not like i want to empty my wallet for 200kw+ now, im thinking around 160-170kw would be good.

All up budget about $6000 now i guess, with all asembely labor done by me and most likely a good second hand T25 turbo.

Took the crank to get ground yesterday too.

[adamjp]

I couldn't speak to the strength of the stock pistons as I've never run a turbo on my engine. For your BP engine you can get ACL pistons for a turbo BP for around $500 within this country. Talk to Greg at ProEngines (or your engine builder) about what he would sell them for.

You might want to have a lurk around turbomiata.net

You will find that plenty of guys in the US have used the Belfab rods to good effect in turbo MX5 engines. I can arrange a good deal for you on a set of them.

I'd be surprised if a simple turbo build would set you back $6k, particuarly with you doing the spanner work.

[daffyflyer]

I couldn't speak to the strength of the stock pistons as I've never run a turbo on my engine. For your BP engine you can get ACL pistons for a turbo BP for around $500 within this country. Talk to Greg at ProEngines (or your engine builder) about what he would sell them for.

You might want to have a lurk around turbomiata.net

You will find that plenty of guys in the US have used the Belfab rods to good effect in turbo MX5 engines. I can arrange a good deal for you on a set of them.

I'd be surprised if a simple turbo build would set you back $6k, particuarly with you doing the spanner work.

You have PM.


Yeah, Dunno about the $6k, its more of a maximum, and it does include some fixing broken stuff, and getting one of the nice BEGi Manifolds (Not that cheap!)

[Juffa]

As already suggested get yourself onto miataturbonet and do some research. They have a very comphrehensive FAQ section. Make sure you read that before posting any questions as they will tear you a new one for any 'newb' questions.

The amount of boost that a stock engine can handle is based on a lot of variables. Flyin' Miata state 12 pounds is about the limit, but there there are people out there running high levels. Things such as fuel management, timing, intake temps and so forth all need to be considered.

The setup I have was recorded at 122Kw at the wheels by the previous owner running 9 pounds of boost. I have made several changes since then, but have not had her on a dyno to tweek the tuning.

J

[daffyflyer]

As already suggested get yourself onto miataturbonet and do some research. They have a very comphrehensive FAQ section. Make sure you read that before posting any questions as they will tear you a new one for any 'newb' questions.

The amount of boost that a stock engine can handle is based on a lot of variables. Flyin' Miata state 12 pounds is about the limit, but there there are people out there running high levels. Things such as fuel management, timing, intake temps and so forth all need to be considered.

The setup I have was recorded at 122Kw at the wheels by the previous owner running 9 pounds of boost. I have made several changes since then, but have not had her on a dyno to tweek the tuning.

J

OK, will have a look at miataturbo


Also note its not a stock motor, it will have forged rods, im just not sure about pistons

[Jeo]

Any progress Andrew?

[ampz]

This reply is more for Daffy (threadjack), what destroys pistons is detonation. Keep that under control (good ecu and tune) and your pistons should have a fairly good time.
I bent a standard rod when the wastegate jammed shut (use correct circlips on your wastegate arms and not a bent pop rivet please)
How much boost is needed to bend one? about 25psi plus (ecu logged 28 so its a guess).
With correct fueling and cooling (air-air, water-air, water/meth injection) you can run more boost than the driveline can handle in its factory configuration.
I see no problems running 12 psi on standard internals. I do but that is me, i take no responsibility if you break your bits.
My setup (very 2nd hand turbo kit and 200000km plus engine) ran 115KW with 300nm from 1800rpm with 6 psi. Haven't measured it at 12 but it is faster for me it is scary faster, the car needs a very gentle touch on anything other than bone dry streets, my gf prefers to drive it at 6psi, but that feels very, very slow flor me now boost is addictive

[daffyflyer]

Looking for a new house at the moment, so need to save for bond etc.

Looking at going in for the wiscos + rods GB though...

[daffyflyer]

Getting Bearings and Gaskets ordered today, and picking up crank (now ground 10thou under) this arvo