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

For a gt2560r forget about pistons, arp studs, oil pump, head job...

just get ANY rods, even eBay rods, new rings bearings and seals, with a hone and mazda head gasket. Done.

this is exactly what I have and I pushed my 2560 to 17-18 psi with zero problems and zero oil consumption.
Did 4000 miles, 2 track days and 4 autox events with zero issues.

I have about $700 in my block, it held 264hp with zero issues.

with the money you have left over buy an ms3 ecu and proper 640cc ev14 injectors.

Thanks for this chart but of course I know that more displacement results in more power and especially in earlier higher TQ and HP. That don't need to be discussed. :)

I am driving a 300whp 2.0l Turbo hot hatch as my daily and of course this pushes so much earlier than my miata does. The miata has a total different engine characteristik but I like it a lot that its get stronger and stronger with every rpm.

http://fs5.directupload.net/images/180421/pkdcfxs7.jpg

As displayed in my dyno chart above it gains power till the limiter above 7000rpm. :)

Again, if I would change to BP engine I would need to buy a new exhaust manifold and downpipe, need a different ECU etc etc...don't want that.

I have already written that in my second reply but it looks like that there are no build NA6 engines in the US. :(

I just hoped to get some answers to my questions written down in the first post...

You did get answers to all of those questions.
Perhaps you didn't read anything you wanted to hear?
Upgrade rods and rehone.
Everything else is unnecessary and futile if you aren't going to properly tune what you have.

Bastian,
You seem like a smart guy so I'm going to be really honest with you.
You have bad plans and plan to waste a ton of money on a garbage engine, because you want to save a fraction of the cost retaining parts that fit this crappy engine. You came here hoping we would tell you the plan was good. We won't. We don't lie around here

It's not just about displacement. It's about head flow, manifold flow, everything.

If you are required by law to have that engine, then ok. But if not, then don't waste money on it.

It only feels like it makes lots of topend power because it makes little down low. Compared to the newer BP's its worse everywhere. Compared to other modern engines its a complete turd.

Ok guys, you won't stop preaching the NA6 is "garbage".
Propably it is really much worse than a BP or modern engine. But that is not surprising, because the design of the NA6 is more than 30 years old, so of course it can't be that good like more modern or modern engines. Because the development moves on. My EMU is also far also not that good like the latest stand alone ECU. Thats also not surprising.

BUT: As written, I like the current engine characteristik of my NA6 a lot, because it is NOT ONE OF THAT MODERN ENGINGE, that kicks your ass at around 2000rpm, and runs out of power at higher RPM. It is more like an N/A engine, that always needs to keep at high rpms.

As the post #20 shows, the BP characteristic with T25 in comparison to the NA6 with T25 is totally different.

While my current set up reaches his max. hp at the limiter (7200 rpm), the BP with T25 (like shown in post #20) reaches his max. hp at around 5500 rpm, holding this maximum till 6000 rpm, and then start losing power with every rpm.
Of course the areas under the graphs of the BP engine are a lot of bigger than the areas of the NA6 engine, which means that it is stronger in total, especially at lower rpms, but again, I like the characteristic of the NA6 far more, although it is accelerating slower.

In the fact that I am using my miata 100% for pleasure and NOT for winning any trophys, the total amount of areas under the graph is not that impoertant.

But to be honest, I don't know how the characteristic of my current NA6 set up with GT2560R will change, if I increase the boost from 9,5psi to 19psi.
I am pretty sure, the graph will more looks like the BP graph from post #20 because the turbo will run out of efficiency at higher rpms, so the power can't increase till the limiter.

But because of you are also preaching it is not economically to upgrade my engines with forged pistons, lets compare three scenarios:

1st: only upgrade rods, bearings and new rings and rehone cylinder

working hours:
- engine needs to take out
- bottom end needs to get stripped completely
- piston and old rods need to take apart
- old pistons needs to get cleaned
- assembling old pistons with new rings and new rods
- assembling bottom end and head
- put engine in

material / engine builder:
- head gasket 50$ stock / 100$ cometic
- head screws/studs 120$ stock / 120$ ARP
- main studs ARP 100$
- plan head and block 150$
- flexhone cylinder 50$
- new oem rings 200$
- forged rods 400$
- acl rod bearing 50$
- acl main baering 80$
- new timing belt, gaskets and seals (like oil pan, valve cover, intake/exhaust manifold etc) 300$ (?)

TOTAL = ~ 1550 $ + a lot of work




2st: upgrade rods AND pistons, bearings and new rings and rehone cylinder

working hours:
- engine needs to take out
- bottom end needs to get stripped completely
- assembling new pistons with new rings and new rods
- assembling bottom end and head
- put engine in

material / engine builder:
- head gasket 50$ stock / 100$ cometic
- head screws/studs 120$ stock / 120$ ARP
- main studs ARP 100$
- plan head and block 150$
- bore and hone cylinder 250$
- forged pistons 600$
- forged rods 400$
- acl rod bearing 50$
- acl main baering 80$
- new timing belt, gaskets and seals (like oil pan, valve cover, intake/exhaust manifold etc) 300$ (?)

TOTAL = ~ 2200 $ + a lot of work



3st: upgrade to BP engine, new pistons and rods, bearings and new rings and rehone cylinder

working hours:
- search for a BP engine and pick it up
- NA6 engine needs to take out
- BP bottom end needs to get stripped completely
- assembling new pistons with new rings and new rods
- assembling bottom end and head
- put BP engine in
- integrate downpipe to current 3" FM exhaust
- integrate BP engine to my car, don't know if it also works with EMU?

material / engine builder:
- head gasket 50$ stock / 100$ cometic
- head screws/studs 120$ stock / 120$ ARP
- main studs ARP 100$
- plan head and block 150$
- bore and hone cylinder 250$
- forged pistons 600$
- forged rods 400$
- acl rod bearing 50$
- acl main baering 80$
- new timing belt, gaskets and seals (like oil pan, valve cover, intake/exhaust manifold etc) 300$ (?)
- new downpipe and new manifold 800$
- BP engine 800$
- BP conversion parts 200$

TOTAL = ~ 4000 $ + a lot of more work


Have I done any mistake in my calculation?

For me, option 2 looks like the most "economic".

Of course option 2 will never reach the efficiency of a BP set up.
But I have a bottom end thats good for 400rwhp (which not mean that I am planning to realize such an amount of power), so I never need to get worried about my engine and at the moment I don't need to touch the electronics/ECU.

Just a further "story". The current installed exhaust manifold is my 4th because the others were crap and cracked all the time. I am happy that Begi finally has sent me manifold, that has a durability of more than 3 month....
That is also a reason, why I don't want to start with a new BP manifold and downpipe. Moreover I like this bottom mount system. I don't know if there is a bottom mount exhaust manifold for BP engines available at the moment?!

I have some money left over, that I would like to spend in my miata, more concrete in my engine. It is also a many years dream of mine to totally renew and forge my own engine.

But there is some difference between 2200 and 4000$...

Maybe you can understand my thoughts a bit better now?

You cant be saved.

my BP engine was 250€ in RUNNING condition - even if it wasn't, if you rebuild anyway, get a cheap one.

i think turning up the boost that much with an EMU is going to be even more expensive than your option #2
and you end up with #3 anyways :likecat:

Agreed

Don't give up. Maybe a hurricane will force him to change, like me :-)

Most cost effective route would be to fly to my house, buy my pre-built LNC 1.6 and return home with it in overhead storage.

We understand your thoughts just fine. Don't insult us by assuming otherwise. You are about to make a bad decision and you're looking for our approval. You won't be receiving it. If you aren't going to heed the advice you ask for, I'm unsure why you felt the need to ask for it.

Scenario #1 sounds a lot better to me if you MUST do something. That way you can save $700 towards an eventual Scenario #3, or better yet, put the $700 towards real engine management.

Alternatively, presenting a BP swap as only costing $1800 more than the option that you're illogically wanting to do, really just makes a point FOR the BP swap. The end result will be at least $1800 better. Maybe even $5000 better.

But hey, if you're just looking for someone to agree with you and parrot your own ideas back at you, i'm your guy for that, too. Just tell me and i'll start doing it. I charge one Like Cat per post.

Just remember guys, in the last two years we get one retard like this, for three others who listen to good advice.

.

Ryan, stop offending or whats wrong with you?

Because really everybody in this thread is recommending to swap to the BP, I am thinking over it!

What exhaust manifold and downpipe would you recommend?
Also, what ECU would be the easiest one to handle?

It should be possible to control the BP engine with 1.6 ecu and EMU in beginning with the FM swap kit?

The best ECU choice for the Miata is the Megasquirt. I recommend the MS3 Basic from MS Labs in Greece. They are forum vendors here.

FM makes a good cast manifold for the 1.8, since you are already looking at their site.

Kraken makes good manifold and downpipe kits. Good prices and quality. Plus he is in Europe

If you want to keep the 1.6, just do rods and hone/re-ring and move on with your life. The 2560 at like 16-18ish psi is plenty of fun and you're going to get out of its efficiency zone past that. Given the 1.6, I doubt you'd hit 300. Stock pistons will be fine. Run that for a while, blow it up, and use those rods for the 1.8 build provided they survive.

Or just enjoy the current setup without any of this headache. Totally up to you.

The folks on here are very much of the 'do it once, do it right' mentality, which is why folks aren't telling you what you want to hear. If you're spending that much money anyway, the 1.8 shouldn't add that much to the cost. I'm sure you can recoup a fair amount of money selling the 1.6 turbo setup you have there.

This is what I'd do.

Hey guys,

thanks for your answers again! :)

I checked out some things the last days. And I am still not sure, what to do! :noob:

I got offered a 1.8 Kraken downpipe (1 piece SS) and manifold, together 650$. Sounds good.
I also found a BP engine, out of a 10th anni NB, for ~ 470$.
I also read a bit about stand alone ECUs and come around, that a MS3 mini would be a nice solution for my application. What do you think?

And or better but finally I have done a 100miles trip on small and curvy country lanes that has demonstrated once again to me, that actually my car is fast enough for its current field of application. :rofl:

So maybe I should really only upgrade my B6 with rods and ARP studs, which both could be reused at a BP. (if I do that step sometime in the future)

And before I put that rods in, I install a MS3 mini with 550 cc EV14 injectors and COPs, which should result in a better driveability of my miata.

In the step of chaning the rods, what would you recommend to renew?

- hone cylinders
- new oem piston rings (where to purchase them? in germany I find one adress that offers them for around 285$.... :eek:)
- new acl rod bearings
- new head gasket
- new arp head and main studs
- new timing belt
- QMAX coolant reroute
- Anything else you would recommend to renew? Should I renew the main bearings?


Sorry for beeing still that undecided!!

I have really also thought about a BP swap intensively as shown above, but I think I don't want to spend 5000$++ (BP engine, manifold, dp, MS3, injectors, piston, rods, seals/bearings/gaskets, new reroute, money for engine builder, hydraulic ramp use etc etc) for such a complete upgrade at the moment.

Thanks for further responses. :)

If it was me, I'd stick with the current motor, leave it totally as it is apart from some larger injectors and probably replace the EMU with an MS3. Turn the boost up a bit, to whatever is considered a reasonably safe level (13-14PSI?) for a 1.6 with stock rods and your turbo and enjoy it as is with an eye on doing a 1.8 swap in the future.

With the thousands of Euros you've not spent on the 1.6, watch the for sale sections and hoard 1.8 bits that you are going to need, get it all built up over time and then maybe swap over one weekend in the future. Keep an eye out for high mileage/mildly broken engines (blown head gasket, low compression etc) that can be picked up for very little money - you save a fortune and it doesn't really matter on previous condition (as long as it's not too broken!) as you are rebuilding it anyway. Other option would be to buy a rusty NB, keep the bits you need (engine, gearbox, diff etc) and part the rest out, you will probably pay for most of the engine build selling off a good hood, wheels, brakes, interior etc..

All you listed for the 1.6, will cost more and yield less than a 1.8 swap. Your new list is not any more smart than your first ones. You say the power now is good. then you want to put rods in a 1.6 and ARP hardware on a NON TURBO engine WITHOUT MEGASQUIRT 3.

Save yourself here. tell us how much power you want, and we will tell you the cheapest, most reliable way to get there. But i can save even more time. You said you dont want to spend 5k. so that leaves pretty much one option. a 1.8 swap. then add small things over time; header, intake, megasquirt 3 etc.

I dont see any indication that you need rods or any other internal mod for what you want, other than it sounds cool to say " I have a forged rod I have forged rods"

I think there was a bit of a loss in translation going on - I read that as he wants to keep the current GT2560R and put it on the rodded/arped engine and turn it up to 18-19PSI.

He's already turbocharged on the 1.6, Ryan.

IDK why he wouldn't build the 1.8 while still enjoying driving the 1.6 and then swap it in when he's finished putting it together. That way he can take it slow and not spend a bunch of money at once.

crap. totally missed that. sorry op

EDIT: yep, i thought this was another thread, had a very similar build list. My apologies for interjecting without knowing.

Finally I travelled 560 miles yesterday to pick up a BP engine:

http://fs1.directupload.net/images/180430/s72xgfsm.jpg


So, you recommend opening a new Thread named "Recommendations for my forged rebuild of my BP engine" or shall we go on in this one?

Because now I need some advices for the build of this engine.

Thanks guys!

Isn't the recommendation pretty much the same?

Just run with appropriate pistons to accomodate your new block.

PLOT TWIST

One thread is good enough.

I don't think so. The engine should be good for around 350rwhp.

So what parts would you recommend to purchase?

Manley rods should be ok.

But what pistons? Wisecos or Supertech? Go for 85,5mm bore? 9,5 or 9,0:1 ratio?

Manley rods, Supertech or Wiseco pistons @ 83.5mm or 84mm bore size. ACL main and rod bearings, ARP head studs, ARP main studs, OEM Mazda Head gasket. If the head looks good just put new valve seals in it and plane it flat. Kraken manifold and downpipe with your GT2560R, MS3 w/ 640cc flow force EV14 injectors.

edit : Do 9.0 : 1 pistons because you want to run high boost on pumpgas. Also do not bore out past 84.5mm with boost, keep it ideally at 83.5 or 84mm

edit #2 : A boundary Oil pump wouldnt be a bad idea either, I went with one. Once you pass 250whp on a stock pump it gets a little too close for comfort if you know that I mean

Do not bore for power. Run smallest pistons you can. Pump gas = 8.6:1 pistons.

You don't think what? What do you mean the engine should be good for 350whp?

There is a formula to what a lot of people run with relative success. Choose one and run with it. I personally went with 84mm supertech 8.6:1. The rest is pretty standard miata turbo prescription. All the hard work has been done and is documented in past threads.

step 1: ignore this bad advice

Wrong

Right

^What they said.

lol, ok because 8.6 and 9.0 are VASTLY different. OP good luck with your build.

One lets you hit MBT on pump gas, the other doesn't. Pretty different.

You all were telling him to run stock pistons previously in the thread, which are at least 9.0 CR most of them are north of 9.4:1. Why cant you hit MBT on 9.0:1 pistons? You would run slightly less boost and be able to achieve the same power numbers at the lower boost due to the higher static compression ratio with the same timing # you would have on the 8.6CR. With less boost you should be able to achieve MBT on either would you not?

Yes, because putting pistons in a 1.6 is stupid. Also: Different motor.

Timing is everything on a BP. Compression is not. This isn't like... a new thing.

That's actually a significant misunderstanding of how it works.

I understand how it works its Maximum brake torque, its when the engine makes maximum torque with a certain amount of ignition advance. Im not going to clutter up this OP's thread though, but it sounds like you guys have a lot of evidence suggesting that 8.6 is superior to 9.1 so Im not going to argue since Im probably wrong.