Recommendations for my forged rebuild of my B6 engine
 

Hi there,

I am from Germany, so first of all sorry for my imperfect english. :bigtu:
I would be very thankful if you could avoid hardcore slang in your answers because I won't be able to understand that. ;)

I am planning to rebuild and forge my 1.6l 1993er miata engine. After now pretty exactly 10 years with the turbo on the stock engine it is time to forge it and increase the boost a bit. :)

In the beginning some facts about my car and set up.

Maybe 1st a picture of my engine bay:

http://fs1.directupload.net/images/180419/4sla8pg5.jpg

I use a Begi bottom mount manifold with a GT2560R, a Begi racer coolant reroute, a DIY IC piping with stock Subaru WRX STI intercooler, 3 inch FM exhaust, ACT Stage 2 clutch with Fidanza flywheel. For ECU I am still using the Greddy EMU with 360 cc injectors.
I would like to further use the EMU and just upgrade to 550 cc injectors, because I am pretty satisfied with it.

That is the current performance so far at around 10 psi:

In the future I would like to increase to 18 - 19 psi.

Well....I have read a lot about forging the miata engine over the last years, but now my rebuild should start soon and I would like to get the latest tips and advices.

So here the list of parts that I am planning to purchase.
It would be very nice, if you could tell me, if my thoughts are correct.

Pistons: the exclusive wisecos from FM, because they seems to be pretty strong and that are the only ones with a 9:1 ratio for the B6 engine
Rods: looks like it is pretty equal if Manley, Eagle or K1. Am I right? So I would buy the cheapest of that three...
Bearings: ACL rod and main bearings, do I need any further ones?
oil pump: considering the fact that i am planning to delete the stock oil squirters, which should accompanied with an increased oil pressure, I am planning to replace only the stock gears against Boundary ones, right?
head studs: ARP
main studs: also ARP?
damper: would you recommend an ATI harmonic damper? My car have a power steering and I want to use it furthermore. the post about the quality problems with the lastest ATI dampers looks not so nice to me. But it looks like there is no alternative to the ATI one. So there is the question ATI or stock damper.
head gasket: Cometic?
Timing belt: Gates racing timing belt?
coolant reroute: at the moment I use the racer coolant reroute from Begi, which means that the rear water exit is guided to the inner space heat exchanger and after to the upper water hose which guides directly into the radiator. At the track last year I have measured a peak of exactly 230°F at the rear water exit. I think it would be better to upgrade to a real coolant reroute system, or what do you think? Is the QMAX coolant reroute the best system on the market?
But also this system works with guiding the water without cooling from the inner space heat exchanger directly through the exhaust manifold to the water pump. I think it is not good to guide a part of the very hot water from the back of the head directly to water pump without cooling that water down, or am I wrong?
cylinder head: till today I am not sure if I should upgrade my cylinder head or still leave it as it is. what would you guys recommend? Is the stock B6 head good for 18 psi and around 300hp at the fly? Or do I need to upgrade it? Of course it would be a drama, if a valve collapse and destroy my new expensive bottom end. Are the supertech valves pretty much better than the stock ones? Some years ago I had a bad exhaust system installed which has resulted in high backpressure and high EGTs. At that time i was running 2000°F in the collector of the exhaust manifold in front of the turbo. Retrospective I am pretty glad that my valves and my turbo survive these tempertures and work pretty well till today.

Do I have forgotten any important parts?

What do you think about my listing above?

Thanks for your feedback and regards from Germany
Bastian

First responses you will get here is: Are you allowed motor swaps over there (to the 1.8 BP) and are they easy enough to get over there?

^ what he said.

A 1.8 will return significantly more power per euro, if you can get ahold of one. More displacement to spin the exhaust turbine with.
however, if you cannot obtain a 1.8 or are dead set on building that 1.6 for reasons, you seem to be on the right track. 550cc injectors might not leave much room for your psi goals, though. Especially if you can/plan to run E85 in the future.

Thanks for your fast responses.
I don't want to swap to BP engine because in my eyes to potential of a forged 1.6l engine is enough for the small miata. Further I would new a new exhaust manifold, downpipe etc. Really don't want that and also don't need 400rwhp in a miata.

Also I don't want to run E85.

So please help me with my questions in the list above.

Thanks a lot.
Bastian

Ditch the "Racer" Reroute, it's a piece of crap that is "engineered" incredibly stupidly. Put a real reroute on it, doesn't matter which one. Qmax is cool.

For your goals, i'd do the bare minimum necessary to put any old forged rods in it. Isn't worth investing additional money, it won't make more power, it won't last longer, and any day you put as little money as possible in a 1.6 is the best day. Stock pistons are fine. Stock head gasket is fine. Stock head bolts are fine. Stock oil pump is fine.

You literally just want your current engine, with a good reroute, and stronger rods. That's it. Nothing more.

hey from germany also!

first of all: der 1.6er marschiert schon richtig gut!

i agree on putting rods, bearings, gaskets, maybe a rehone and some rings in it and leave it as it is.
1.6l engines are SO cheap here (sold mine for 60 euros, because 1.8), its not worth building it.

15-16psi on that 2560 should be enough, everything above is just hot air without real gains.
do you have COP's in there? would be good!

edit:
do NOT build that head, just new valve stem seals, oem valves are pretty tough

Sorry, but I can't really comprehend your argumentation...:dunno:

It sounds like the BP is such a different league in comparison to the B6. I think we are talking about 0,3l less enginedisplacement?

Is it really true, that the stock pistons are good for 18psi and so around 300hp at the fly? Till today everybody told me that the limit for stock pistons and rods is around 240hp at the fly...?

In the german Miata forum there is also often written about very high oil consumption after a head gasket change. The main opinion about this problem is that the block starts unbending if the head is taken apart which results in oval cylinders. Haven't you observed this phenomenon in the US often?

That is the reason why I think it is a lot of better to bore the block after taking the head away and the pistons out.

And the bolts and gaskets needs to renew, so the price difference between new stock and new ARP is not that big, same for head gasket.

And I have no COPs, I think the EMU can't handle them.... :(

Don't get me wrong, I am really interested in your opinions, thats why I am asking, but I can't really understand why it should be such a "senseless" investment to do a clean and strong B6 building.

Thanks again :)

And better head design. It's not that it necessarily makes more peak power (though it does, a bit), it's way more area under the curve.

Everyone told you wrong. Or you're confusing what they were telling you about rods with pistons.

Smells like BS.

Do not bore if you don't have to. Hone absolutely. It's likely that your block could use a hone job after all these years. But, the reason given is incorrect and BS.

ARP is not necessary for your power levels, but head studs are cool because they're re-usable. There is absolutely zero advantage to a cometic head gasket in this application. You are free to waste your money on it if you'd like, of course.

Stock ignition should be fine.

It's not necessarily senseless to want to do a cheap refresh and make sure it can handle a little more. It is completely senseless to spend a lot of money on one, because it's inferior in every way to the BP (which in itself isn't great either.) You need nothing more than forged rods to hold your goals and anything your turbo will ever dream of putting out. So, anything more than that is just money wasted for zero gain.

What is BS?

Bullshit.

In your opinion, what is the reason for the high oil consumption after a head gasket change at so many engines?

I don't think that actually happens. I've changed a head gasket or dozen and have never seen that scenario occur. I've also never seen it happen on this forum.

If it happens in Germany but not here, i'd be forced to suspect geographic location having something to do with it.

It's common to see increased oil consumption on old bottom ends if the head is rebuilt. The increased cylinder pressure caused by valves that actually seal will overwhelm a worn-out ringpack that was marginal before the increase in cylinder pressure. It has nothing to do with the head gasket.

I mean, we're talking like... completely destroyed heads, and not something that would happen with a typical skim 'n' go for head gasket purposes only, right?

If you are ONLY changing the head gasket, there is literally no reason why the engine would burn oil afterwards. German forums are just as bad as UK forums, apparently.

Stock pistons with the oil squirters are capable of handling turbo power, as they are also used in the B6 turbo engines.
Most important thing to keep your pistons in one piece is not to detonate. Using forged pistons gives you more tolerance to detonation.
If anything: your tune must be good to keep your pistons alive, even with forged pistons. If your tune is good, stock pistons should be able to survive around 300 hp on the flywheel.

So instead of spending a lot of money on the engine, you might want to invest money in your ECU and tuning to keep the engine alive.
I would spend the money on another ECU, good ignition and good injectors (EV14) before spending money on forged pistons, oil pumps, ARP hardware and harmonic dampers.

That sounds like utter bullshit. The most likely causes are bad piston rings or bad valve seals. Maybe someone just used crappy valve seals when replacing the headgasket?
When you are doing this kind of work on an engine it is always a good idea to hone the block and use new piston rings.

this.

i also don't see a fully built 400whp+ engine without proper engine management

Guys, I see your point of view.....and I also agree that it won't be a mistake to upgrade my ECU.

But at the moment, I want to rebuild my engine. Please understand that I don't want to start a further project with a new ECU now.

And again depending the question about forged pistons.....
....till today I am always driving my miata with some scary feelings that the my rods could torn up every second because they were used at the end of their max. load-bearing capacity.
So I don't want to open my engine now, put some stronger rods into it, increase the boost and then powering the pistons near at their max. load-bearing capacity.
In that case I would again have that scary feelings depending my engine, that I definitely don't want.

Maybe also in some years my turbo will break down and it makes sense to upgrade to a little bit bigger one, then it is very soothing to know, that I have a strong bottom end that can easily manage some extra power.

I also found that post:

https://www.miataturbo.net/engine-pe...-needed-80200/

with that answer depending forged pistons or not:

So running 280rwhp should be really the limit for the stock pistons? Or are the BP pistons that weaker then the NA6?

Forged pistons sound fun. You should get some.

Just so you understand below is a dyno that shows the difference in area under the curve between a 1.6 and a 1.8 motor. Short of the initial cost of the motor, all the inside parts cost exactly the same to build. So if you are going to spend several thousand dollars on parts, to us it makes sense to spend the extra bit up front to get the large increase in area under the curve.

https://cimg5.ibsrv.net/gimg/www.mia...f30e907187.jpg