Turbo gurus, guide my cash
 

What would be the best turbo for an engine with a ported head, ITB's and 11:1 CR? I'm planning on running it in conjunction with water injection if necessary, but my goals are
- not a ton of boost, 12psi with WI at the very top
-quick spool
-response response response
-torque

I'm thinking I could run a pretty big turbo at low boost for my needs, since the head and plenumed ITB's should flow pretty damn well.

What say you?

You did not mention the most important number... HOW MUCH POWER DO YOU WANT? Are we talking 150whp/200/300??? The most popular turbo below 250whp is the GT2554r. Between 250-300whp, GT2560. Above 300whp, you're looking at a GT2860/71. Once you hit 350whp, we're talking GT30+.

Your setup for 250whp is a GT2560. Quick spool, huge midrange torque, top-end for 300whp. End thread.

thanks! what would be a step up from that, something that could handle 300-350? i wouldn't mind rocking something with a little spool on it at 250hp until I can get tranny gears that won't fly off :D Should I consider the sizes of the intake and exhaust sides of the turbo, or should the regular setup be alright? Edit: edited numbers

edit: The main reason I'm asking instead of just buying a gt2560 to begin with is basically because I feel like my system could spool the crap out of one of those, so I wouldn't mind rocking something that on a stock miata would have a sort of crappy spool. Not a huge ass one like a T30 though.

Edit2: I was thinking something like a T28?

Edit3: when I was talking about 'the size of the intake and exhaust sides of the turbo' i meant the compressor and turbine sizes, and the A/R. I'm not a turbo guy, so I have no real experience with changing that stuff around for different purposes

imho 12psi on a big turbo on a high comp motor is A LOT of boost.

hehe. yeah. :D Edit: 12psi would be max, and thats on aftermarket rods and WI.

I think a GT2860 is what I want. any advice on A/R though? Can you find exhaust manifolds for miatas that mate up to T28s? Edit: I like that the t28 maxes out at around 360hp

with a CR as high as that you will have such a huge dependency on octane it wont be funny
you will need a proper aftermarket ECU and a very smart tuner to handle off boost response (ie high timing values) to on boost behaviour - perfectly possible but the transitions are going to be close - if you get it wrong detonation will be your companion

I vote for a T3 50 trim on an equal length rams horn style manifold with a 3inch downpipe

The T28 is the exact same thing as the Gt2560R.

T28 = Journal Bearing
GT2560r= Ball Bearing

Are you having a custom plenum built for the ITB's? You have to be a little more realistic with power goals man. 350hp on a high-compressed motor is goin to be a tuning nightmare.

did we already kick you out of here for being a ------? I really don't want to read a bunch of ITB garbage. I also don't really give a fuck for the high-compression / FI crap that anyone with an engineering background thinks is garbage.

Basically, you fucked up and you've spent all this money on a slow, NA, ITB queen ride because you wanted to be cool and JDM. Now look at you, you're a bitch. You're also one of those morons who doesn't understand that "12psi of boost" from a pea-shooter turbo is different from a gt45r.

Is this even english? Your girlfriend can spool my balls, rather than letting them sit on her chin.

What viperormiata is saying is with an 11.0 CR you cannot acheive the same boost or HP as a motor with an 8.5 CR on pump gas.

You will always be at a diadvantage to the guy with a lower CR, all other things being equal. That's freshmen class Turbo 101 information.

My guess is you'll probably never see 300HP on pump gas with that lousy CR even with WI, unless the WI gods are really good to you.

I don't know. I'm interested to see you get that working but I'll reiterate ITBs plus high compression plus turbo= tuning nightmare. That's a lot of variables to work with. Adding WI further complicates things and adds another place where a failure would cause catastrophic damage. Plus you're talking about big money now for a setup that might have slightly better response than a similar one without the hassle of ITBs or the danger of super high compression and significantly cheaper. Drop the compression down a point and I think you'll still have the response you want but with a better margin of safety...or get a v8.

My guess is about 220WHP. With any size turbo you pick. You can have it at 3500 RPM or at 7100 RPM depending on the turbo.

Maybe 230WHP.

-yes I'm building a plenum for the ITBs
- I'm not opposed to dropping CR, but only if its impossible to get 12psi, which I don't think it is impossible. I'm still researching though. I'll be happy with whatever HP 12psi gives me.
- the tuning doesn't really scare me. maybe it'll turn out to be impossible to tune the itbs on a turbo, but i'm gonna give it a shot first, and if it doesn't work I'll sell them and swap out a regular single throttle body style manifold
- yeah sorry about not knowing what a T28 is, I don't really know that much about turbo systems yet.

the biggest reason I'm doing what seems like a complicated setup is that I'm working with what I already have, and I think it might just turn out awesome.

Hustler, eat a dick.

Still though, the reason I started this whole thread is basically to ask, if you have a really high flowing motor, does that affect what turbine/compressor setup you should run, or A/R?

Edit:
Even if the number is low, I think the dyno curve will look mighty interesting. I'm fine with those kinds of numbers. I know you guys don't like the idea really, but give me a chance to do it and see what happens, I think it might turn out pretty fucking mean.

why 12psi? Why did you choose this magical #?

You need to sell the motor and ITB set-up and buy a stock motor. 230whp is easy on a stock motor, almost impossible on yours.

so thats a "no" on whether or not I should worry about A/R and turbine/compressor housings?

Edit: Just noticed this
This is what I was looking for. Thank you. I'm tempted to run 10:1 because this is tried and true on NB's, but 11:1 doesn't seem impossible, people just seem scared of it.

static compression all depends on power goals. and the trade-off with output and spark angle. As for turbo sizing, its basically been beaten to death over the last 20-years on our old-ass motors and old ass turbo systems. Its not rocket science anymore, pick your output goals, determine where you want those targets, then buy that turbo. If you want 230, that's a gt2554 or gt2560 (where do you want the power) on a stock-ish motor. You probably have a fairly bad-ass NA motor, but its a waste of time and money to change directions on that motor. Sell it and buy a stock-ish motor, or build a motor like mine for $2k.

do you have a plan for this car? Street? Autox? Road Racing?

uhmm, yeah, but its not anything anyone wants to hear about on this forum, lets just say the most important things are responsiveness and midrange torque
hustler, I have to say, i really appreciate your civilized and intelligent answer. I think I'm gonna run a season on it non-turbo at least, but in the meantime I'm gonna start stockpiling turbo parts and figuring out what I want to do.

here's a perfect guide for your cash: send it to me:)

lets say I run a gt2554; it seems to me like that thing would be damn near insta-spool on my setup, so the wastegate would open pretty fast. Would I need to run an external wastegate to not choke things up on the top end?

it would help

search?
google?

Seriously. Nobody on this forum can tell you what turbo to run. You have to decide what's best for your goals. It takes a lot of time/research to get a good grasp of what will work within your criteria. All anyone here can do is say "XX turbo for yy to zz HP, etc".

And FWIW, all the flow shit in the world will only help spool so much. You gotta remember the average pent roof DOHC engine (ie-your motor) has ~92% VE around peak torque, which you will surely be spooled by. You will never reach 100% efficiency, so everything in the world you do to increase flow is looking for that last 8%. IE-you won't see a 1K RPM decrease in spool time because of your setup from flow gains alone.

I'm gonna say put a GT2560 because it will spool 'well' and be "good for" 250-300whp. But that's just an opinion from someone on the internet who's never even seen one in real life, much less drove a miata with one.

Thank you. I had no idea about that. That's basically what I was looking for with this thread.

savington runs this turbo at 230whp on a 1.8 and it sees the track as much as anyone here.

+1 That's just some dumb dumb questions you're asking.


why on EARTH do you care how many PSI you are running? I'll tell you what, put in some maxed out 750cc injectors, swap cams for something with a whole lot less duration, and I'm sure you can run 12 psi. At 57 horsepower. AT THE WHEELS!!!11!

The reason no one wants to talk about ******** is (with rare exception) the *******s know jack shit about how a car works.

11:1 is a joke. You're really better off without a turbo. You *HAVE* to pick a power goal.

It's like going to the walmart to get something "wrapped in plastic". Think about what you need first, in very, REAL terms. Then maybe someone can say something. Not being rude here, but you don't strike me as any tuning genius, so no one is going to recommend something you can "figure out" to you.

Do me a favor, show me a dynosheet for the monster you already are driving. The only real answer to your question is this: Buy a second motor, build it for a turbo. Then swap them. You'll have an IRTB set up, and you'll have a fast set up, you can use whichever you want without having all these losing compramises.

I dont see mixing an n/a built engine with a turbo as a good idea. its doable for sure, but stupid imo.

Seriously man, you have to take all this negativity with the best intentions. The motor in your car is the EXACT opposite of what you need for boost. It sounds like a fun setup don't get me wrong but, really, just buy a stock motor and do whatever you want to it but keep it efficient for boost purposes.

As far as turbo sizing it all depends on what you want. You need to SEARCH and ask around for people opinions on what they think their turbo is good for.

EX. I'm running a 2554 because I will be autocrossing every month and will need the instant spool. However, when I move to Orlando, and only drive on highways, I will switch to a 2871 and put my motor to good use.:cool:

Good luck man!

now that everyone is dogpipiling this kid and trying to poz this unsuspecting neg, I have to say "you're learning now. Just stop posting the NA/******** shit, please."

down like a clown charlie brown:cool:

Run a 3071, With compression like that you should spool it very well and make good power per psi.

You can turbo a 11:1 motor. Most guys would be running alcohol w/ that compression ratio. But, with pump gas you better have a dead on tune. It won't be very forgiving.

Methanol Injection is a must on this car if you are running pump gas.

Consider running aftermarket cams w/ a tad bit more overlap to reduce the Dynamic Compression Ratio.

Hey now, don't come in here using big words and fancy terminology for ideas that are not understood by the vast majority of the forum. ;) That's a whole 'nother thread...

And OMG you offered someone advice...

I know, don't get used to it:) :giggle:

I always try to find my answers on google as well as the forums before asking any questions. Here is what I found in like 5 minutes, and yes, it has been discussed on other forums before:

MotorSports Digest
Dyno results, high compression and E85! - E85Performance.net - Discussion Forum for All E85 Car Owners
High compression engines and boost - Honda-Acura.net
High Compression vs. High Boost – Superchevy.com Tech Talk Forum

What I take from the reading I just did is that 12psi on 93 octane and 11psi = smoking crack or piss poor ignition timing and no power gain. I say either get that thing running E85 and a gt30ish turbo and do the 12psi you want, or get the same turbo and stick to around 5-6psi ... which will still likely put you at 200whp, but at the ragged edge. WI might help, but only to a certain point.

Did you not see the clever walmart comment? You don't go shopping for something red, you go shopping for something to play your BlueRay(tm)s. You need to pick a HP and ask how do I get there given these constraints (i.e. I want to run 11:1 or I am a huge retard with no more right to be on God's Green Earth than an impotent three toed sloth).

Don't say "I want to run 12 psi" cause what if 12 psi turns out to be the very worst number you could ever choose.

Please listen. Many of the people here are internal combustion engineers, work for NASA, or other such things. And then there's the folks who aren't even me. :-) Most of them are smart, too.

Analogy Fail

(You're obviously not married.) ;)

EWGs are more important at low boost levels than at high boost levels.

(I am making these numbers up.)

To make 230whp on a 2554R, let's say you need to run about 15psi. 15psi is about 75% of the airflow of the motor through the wheel, and 25% through the wastegate.

At 6psi, you only need to run about 40% of the air through the wheel, which means 60% through the wastegate.

Thus you need more wastegate for lower power levels and less boost.

Dude do you already have 11:1 cr, or are you about to build it?
If you haven't built it yet, forget it.

If you already have the motor built. I would try a thicker head gasket, and less boost. And mabe the cam settings the guy was talking about.


Futher more, CALL BEGI, tell them the setup you have, and they will tell you your limits.

They will help you decide what turbo you need, and what boost to run, for said hp.

DO not attemp this without talking to them and FM.

reading comprehension ftl

Yea, I just read over the first post again. Man that is high compression.

I was thinking exactly that when I wrote it, but assumed it would be sexist to mention the elephant in the room.

Er, where I said reduce flow till you're at 50 hp? Yeah. My point was high manifold pressure has very very little to do with power output. Small enough valves and all that pressure won't go anywhere.


talking to Bell and FM is the best advice so far, except all the people saying build a second motor.

I wonder how many of the posters in this thread, that have given negatives on turbos and high compression, actually have experience to back up their negatives. The whole thread here seems to bring enjoyment in bashing the OP and not bringing wisdom to an area of unknown to majority of the group.

I for one will encourage the OP to research the positives. Look at cam profiles, there is a lot that can be archived by controlling cylinder pressures, with camshafts. To all remember that as you retard timing you will probably increase torque (seems to me the first post was asking for that) Water/meth injection can certainly be a player in a program such as this.

Yes this concept will see the need for major tuning, but since the OP is IRTB experienced already, I would bet he has done some of that.

This project is out of the box thinking, and I wish good luck to the OP. Everyone told me that 13:1 compression and a ton of nitrous on my bigblock chevy would lead to disaster, funny how none of the non believers could keep up to me.

Perhaps some positive responses other than drop the compression or build a new program?


Ron

^+1 Agree

Ron, I am just going to assume you did not do that on regular fuel right? Anyway, we love to talk about this stuff, but I hate having to be the one doing all the research ... or rather, I should say the OP could have looked into it more.

The OP doesn't seem to have the right idea about what to ask, how to ask it, a goal, or any proven experience tuning. You can buy IRTB's on chinabay for $300 and have a car slower than stock. He at least had an aftermarket EMU.

It's why I, perhaps without sugar, cream, and a cherry on top, have asked for a dynosheet on his car.

If he hasn't done that before, then it IS too big a task for him. If he asks 3 sensible questions, I'd be in full support.

Can you explain this?

I'd like to see something good there, too. I know it's true, certianly it helps spool - so much so I couldn't keep my system under 18 psi till I advanced the timing, now I can hold ~12.

I think the idea is that there are still burning elements, or at least less time for the charge to cool in the cylender, by the time you exhaust. Higher EGTs, more spooling energy.

But I'd like to hear it anyway. Learn me something.

+1

I also want to know how combustion behind LPP increases torque. If you're talking about stove-piping a turbine, then have fun for the two track days it lasts. We build cars to last 100k miles, not 2-hours on a racetrack.

I like this guy. My general consensus from this thread is that its doable, but the majority of people think its a retarded idea because its not the way they did it.

Oh, and the guy who wanted a dyno sheet, I would love to dyno my setup, so if you can recommend me a good dyno place that knows megasquirt within 300 miles of nashville, TN, I would appreciate it. I've yet to find one.

How far are you from DIYautotune?

i talked to them, they said there's no dyno time available, they said they have one 'mostly for R&D purposes.'

No, we think it's a retarded idea because we all have more experience than you do with turbos and we understand the physics behind WHY it's a retarded idea. You should either go back to ClubRoadster and fellate the ITB crowd some more, or shut your yap and try to understand WHY it's a dumb idea.

Compressing an intake charge 11 times increases pressure. PV = NRT. Increase the pressure, maintain volume, and temperature skyrockets. In case you skipped Turbo 101, big temp = big knock = big boom. This is true whether you compress the air in the cylinder or in the compressor of a turbo.

The difference is that when you compress it in a turbo, you have a couple of good ways to remove heat from that charge. Intercoolers are 90-95% efficient, and water injection is 100%+ efficient. This means that no matter how hard you compress the air, whether it's 2:1 (14psi) or more, you have the ability to remove that temperature increase from the intake charge, down from the 250+ degrees to around 80 at the throttle body with a decent intercooler, or 40-50 with water injection.

At the end of the day, the cylinder will only tolerate so much pressure for a given volume at a given temperature. Because you are essentially unable to remove the heat that occurs during compression, turbo owners generally reduce compression and increase the pressure elsewhere (in the turbo). Yes, you can run 11:1 and a turbo at 10, 12, 13psi. It's doable. Will you make a lot of power? Mabye, with a huge turbo. Will it be an easy car to drive? No. The turbos that are kicking hard at 13psi produce WAY too much heat to be stuffed into an 11:1 motor, and the turbos that will keep the heat out at 13psi aren't kicking hard until 20+.

You also have to worry about EGTs. You're going to have to back the timing off so far with 11:1 pistons that you may not be able to even obtain 13psi before the EGTs are so high you're melting pistons.

You WANT your 11:1 motor to be able to handle boost because you don't want to build it again and admit your mistakes. We are not going to coddle you into thinking that you didn't make those mistakes. Boosting 11:1 motors is doable, but not intelligent.

Savington, you usually know your shit and I respect you, and I think you're right with everything else you said, but as far as this stuff ^^, that sounds like an awful lot of speculation. Also, all the other stuff you mentioned is true, yet only one side of the story. There are also upsides from running high CR. I could sit here and say that the engine will probably have better x characteristics under y circumstance than a regular engine, but that would be speculation as well. I need to do more research and see if anyone has ever actually done this before, and get some actual information, rather than opinions. I was hoping some people would be able to pipe up with info like that from this thread.

Even if I didn't have my block done, I think I'm still gonna run the 11:1 N/A for one season, then slap a turbo on and see what happens. if its impossible to tune and get running right, then I'll either sell the turbo or the engine. End thread. I'm sick of arguing about it. I'll just note that some MT guys think its stupid, and one party will be telling the other 'i told you so' if it turns out to be awesome, or is a pain and blows up.

tell that to the engineers at toyota, nissan, subaru, mitsu, vw, and chevy to stop lowering static compression in their turbo cars. I'm pretty sure they'd like to save millions in development adjusting the NA motors to lower-compression "FI-motors."

Pretty much everyone on earth understands the relationship between static compression, spark, and charge density...its just the math involved in engineering that scares most end-users away.

Apparently you firmly believe that you're right, and everyone who's done this before, including engineers, is incorrect. Show us how fucking brilliant you are, we're waiting. Now please excuse me, I have to smoke the tires in 3rd gear of my 8.6:1 compression slug.

I smoked your mom. In third.

It only sounds like speculation to you because you don't have a fucking clue what you are doing!

Most of these bastards on here have read a fucking book or two on turbos and preparation of engines to accept them. Why don't you give it a try?

Why don't you go look it up, Hyper Jr.?
Instead of telling everyone who has studied this crap for years why they don't know what they know.

Yeah, you're the only smart one and the whole world is lying to you just to fuck with you.

You want to keep peak cylinder pressure around 14* ATDC. At some absolute temperature around 1250K, gasoline will spontaneously ignite in the presence of oxygen. BMEP is important.

These are facts. Here's some more

For maximum efficiency, you want to stay below 1250K and maintain peak cylinder pressure around 14* ATDC. This doesn't change NO MATTER WHAT!

You take in air that has some absolute temperature. Then you compress it. During compression the air is heated from the change in pressure (PV=nRT for ideal gases) as well as the turbo's adiabatic efficiency. Then you cool it using an intercooler (aftercooler), where the intercooler will reject a certain percentage of heat, bring the charge temp down closer to ambient.

The intake valve opens and the piston begins to descend, creating a vacuum. A delta P. This creates a void and the charge flows in. As the piston reaches BDC, the charge is still flowing in, but the piston reverses and begins to ascend. However the charge entering the cylinder has a mass and a velocity, therefore it has an inertia and will continue to fill the cylinder. The intake valve closes at 47* ABDC on your motor IIRC and now compression begins. Granted all the while the charge is being heated as the piston, cylinder, and combustion chamber are hotter than the charge.

So you compress it however much the actual compression ratio is after the valve event. It gets even hotter. Of course the fuel evaporates and this phase change removes some heat from the charge depending on the mass and heat of vaporization of the fuel. And of course heat is still being transfered from the surroundings to the charge until it's compressed to a point where it's hotter than the surroundings, then the heat transfer process reverses.

You send a spark to ignite the mixture to begin combustion in such a way as to:

Have peak cylinder pressure ~14* ATDC
Not light the mixture too soon as to cause knock or create peak pressure before 14*ATDC as this induces more negative torque than positive.
Not have the mixture light too late as to cause peak pressures to be after 14* ATDC.

YOUR PROBLEM: You put the compression to high and there's too much heat in the charge. So when you try to light it at the required advance to maintain peak pressures around 14* ATDC, you get knock, forcing you to retard to maintain safety at the expense of performance. Guess what? This is the point of diminishing returns with high compression. The point where you can not advance enough to maintain peak pressures at 14* ATDC. Now you retard timing and loose a lot of power.

Doing so is not ideal. Increases EGTs, reduces efficiency, causes more heat to be rejected into the cooling system, etc. And less HP.

So if any of this is new to you :giggle:, consider "accepting the norm" and continuing your research on high comp, low boost engines.

Disclaimer: the above is a very broad, general description. It's in no way complete.

that is what we call physics :fawk:

you guys are wrong. High compression turbocharged engines are faster with retard spark.

This is insane. What is the point of asking for our opnions if you already made your mind up before posting!

Just blow your motor man.