recommendations for a turbocharger

I am about to start my first turbo engine build and need some help sizing a turbo. Open to all suggestions. I am building a 2L (or 2.2L) turbo engine with a target of 300-325HP. Its a flat six with a divided bank header setup. I would prefer to have usable torque and driving characteristics as compared with peak HP numbers. This is a driving car that will spend a lot of time on tight twisty backroads. Turbo response and minimal lag are very key parameters for me.

The current design has a twin scroll header with 3 cylinders firing 240 deg apart. I will have equal length primaries with as short of length as possible. I was considering a GT25 as it seems about right for my goals. Maybe GT28 variant but am concerned it will be too big unless I get the A/R correct. I do not want lag. I want quick spool and top-end fill to 7300 rpm.

I can easily go with a twin turbo setup. In this case something small like a TD03/4 hybrid might do the trick and I could size the turbos such that they run in parallel but have boost characteristics like a sequential.

There are a lot of great turbos for the WRX/EVO crowd running 2 or 2.5L engines. I can borrow much from this but am not sure if there will be differences between a six vs four cylinder engine. My thoughts are that the extra cylinders will smooth out pulse delivery and reduce lag.

Additionally I would prefer to have an external wastegate setup. I am concerned about boost creep with an internal wastegate. There are also exhaust pipe and muffler packaging considerations.

Has anyone built such a system? Are there any recommendations for turbos? I am sure you all have your favorites.

Do you already have the manifold? If so what flange is it?

The 2560 will be too small. You're looking at a 2860R-sized turbo minimum, and you'll be pushing it hard. (Which isn't a bad thing.)

Why one big one vs. two small ones?

Cheaper, simpler, and for his power goals, there's no reason to use a big turbo.

EFR6758 is pretty tough to beat. I strongly recommend playing around with BW's matchbot program

One thing many people overlook is a given turbo can flow only a certain amount of air no matter what engine it's bolted to. While the efficiency of the motor it's bolted to certainly plays a large part a turbo can only move a certain amount of air and a certain amount of air can only make so much power. 30-35 lbs/min should get you the power you need, of course the knee point and max ve of the turbo will affect how usable it is. Ignition tuning also greatly affects the spool of the turbo.

EFR6758 sounds perfect for a single turbo set. And if you decide 300hp isnt enough (should take a week or two, lol)you should be able to pump out 400hp on 93 with it. Actually re reading I thought he said 3.2 liter flat 6. With only a 2.2 liter and only wanting 300hp the 6258 would be more than adequate.

Or running twin GT2560R's, but that probably would be more laggy than the 6758.

Meth injection and a larger turbo.

captdownshift wrote: EFR6758 is pretty tough to beat. I strongly recommend playing around with BW's matchbot program

What program is this? My googling didn't come up with anything

Swank Force One wrote: Cheaper, simpler, and for his power goals, there's no reason to use a big turbo.

May have to explain that one a little more.

One turbo will be cheaper than two, but the header to connect them together will be more expensive. Seems very much a wash.

Lag vs. power- thats more about sizing it right over a 1vs2 debate. One turbo can be very laggy, too- if the goal is to make massive power. But I think the window of working of 2 makes the selection a little easier, since it's also more in the window of many turbos.

other than that, I have nothing to add. Even though I've only worked on turbo engines over the last decade, I've never paid attention to them.

Problem with the 1 vs 2 thing with only trying to make 300hp is that ball bearing turbos in the size that you'd want dont exist so you end up with running turbos twice as big as you need.

Also, matchbot http://www.turbos.bwauto.com/aftermarket/matchbot/index.html

alfadriver wrote:

Swank Force One wrote: Cheaper, simpler, and for his power goals, there's no reason to use a big turbo.

May have to explain that one a little more. One turbo will be cheaper than two, but the header to connect them together will be more expensive. Seems very much a wash. Lag vs. power- thats more about sizing it right over a 1vs2 debate. One turbo can be very laggy, too- if the goal is to make massive power. But I think the window of working of 2 makes the selection a little easier, since it's also more in the window of many turbos. other than that, I have nothing to add. Even though I've only worked on turbo engines over the last decade, I've never paid attention to them.

Making a simple Y pipe is going to be substantially cheaper than buying an entire second turbo, not to mention the extra flanges and fabrication from there that will be required.

Plus if you want an efficient 300hp with twins, you want two turbos that are efficient to 150hp. Not easy to find. There's more 300-350 turbos available to use than 150-175. So, twins would be more work, more money, and less selection. Not a single upside to it besides getting to tell your friends your car has twin turbos.

In reply to Swank Force One:

The way he's describing the system, it does not sound like a simple Y.

Plus- where does it go? Ok- for a subie, the plumbing all comes together in a reasonable spot. But even then, keeping them separate is not all that hard. Moreso- one does not have to firgure out how to plumb a crossover tube and still have the turbo someplace in the engine compartment.

As for turbos for 300-400hp- Find a crashed Ecoboost F150. There are two of them right there- spool fast, and can support 400hp. Last I checked, we sold 300k of them last year- seem like they would be incredibly common.

To say that there are no upsides except for bragging makes me think that it's not a well done system. Ours work great. And even those can be a lot better.

The SHO and F150 are fine with twins. Not sure how a single turbo would make either one of those better.

evildky wrote: One thing many people overlook is a given turbo can flow only a certain amount of air no matter what engine it's bolted to. While the efficiency of the motor it's bolted to certainly plays a large part a turbo can only move a certain amount of air and a certain amount of air can only make so much power. 30-35 lbs/min should get you the power you need, of course the knee point and max ve of the turbo will affect how usable it is. Ignition tuning also greatly affects the spool of the turbo.

Turbo newb question: what sort of timing tuning decreases spool/boost threshold time? More or less advance and what load/rpm/throttle conditions?

More advance, always. Tune to knock threshold or mean best torque under all conditions.

alfadriver wrote: In reply to Swank Force One: The way he's describing the system, it does not sound like a simple Y. Plus- where does it go? Ok- for a subie, the plumbing all comes together in a reasonable spot. But even then, keeping them separate is not all that hard. Moreso- one does not have to firgure out how to plumb a crossover tube and still have the turbo someplace in the engine compartment. As for turbos for 300-400hp- Find a crashed Ecoboost F150. There are two of them right there- spool fast, and can support 400hp. Last I checked, we sold 300k of them last year- seem like they would be incredibly common. To say that there are no upsides except for bragging makes me think that it's not a well done system. Ours work great. And even those can be a lot better. The SHO and F150 are fine with twins. Not sure how a single turbo would make either one of those better.

Those are bigger motors. To make full use of twins at his power goal with his motor, he'd need a pair of like... GT15s.

I think the question to ask is: If many of us can get lightning fast response out of a single turbo making 300hp on a tiny 4 cylinder, why are twins necessary in 300hp cars?

Don't get me wrong, i'm not against twins. More turbos = more better as far as i'm concerned. The world needs more turbos. It's just not something i'd mess with with this low power goal. Especially since a true twin setup rarely spools faster than a single setup anyways, since you're splitting the motor in half.

also, on the plumbing of a single versus twin, you're going to have to fab a collector either way, whether it's before a single turbo or after twins.

hairbrained: what do the maps for the vw vvt turbos look like? I can't recall if it's the tdi's or the 1.8t gas engines that got them, but if you're set on twins, those might work well.

bluej wrote:

evildky wrote: One thing many people overlook is a given turbo can flow only a certain amount of air no matter what engine it's bolted to. While the efficiency of the motor it's bolted to certainly plays a large part a turbo can only move a certain amount of air and a certain amount of air can only make so much power. 30-35 lbs/min should get you the power you need, of course the knee point and max ve of the turbo will affect how usable it is. Ignition tuning also greatly affects the spool of the turbo.

Turbo newb question: what sort of timing tuning decreases spool/boost threshold time? More or less advance and what load/rpm/throttle conditions?

Retarding the timing gets the turbo spooling, launch control systems retard the timing to the point of building boost without load.

evildky wrote:

bluej wrote:

evildky wrote: One thing many people overlook is a given turbo can flow only a certain amount of air no matter what engine it's bolted to. While the efficiency of the motor it's bolted to certainly plays a large part a turbo can only move a certain amount of air and a certain amount of air can only make so much power. 30-35 lbs/min should get you the power you need, of course the knee point and max ve of the turbo will affect how usable it is. Ignition tuning also greatly affects the spool of the turbo.

Turbo newb question: what sort of timing tuning decreases spool/boost threshold time? More or less advance and what load/rpm/throttle conditions?

Retarding the timing gets the turbo spooling, launch control systems retard the timing to the point of building boost without load.

No, retarding time doesnt make the turbo spool faster. retarding timing to the point that most of the air to fuel mixture is in the exhaust when the spark goes off will spool the turbo, but its hard on the exhaust valves and turbo AND it will still make less power while under load than just running all the timing advance that you can. Running anti-lag like that should be reserved for trying to make boost in no load conditions, like just before launching and during shifts and only when racing.

Leafy wrote:

evildky wrote:

bluej wrote:

evildky wrote: One thing many people overlook is a given turbo can flow only a certain amount of air no matter what engine it's bolted to. While the efficiency of the motor it's bolted to certainly plays a large part a turbo can only move a certain amount of air and a certain amount of air can only make so much power. 30-35 lbs/min should get you the power you need, of course the knee point and max ve of the turbo will affect how usable it is. Ignition tuning also greatly affects the spool of the turbo.

Turbo newb question: what sort of timing tuning decreases spool/boost threshold time? More or less advance and what load/rpm/throttle conditions?

Retarding the timing gets the turbo spooling, launch control systems retard the timing to the point of building boost without load.

No, retarding time doesnt make the turbo spool faster. retarding timing to the point that most of the air to fuel mixture is in the exhaust when the spark goes off will spool the turbo, but its hard on the exhaust valves and turbo AND it will still make less power while under load than just running all the timing advance that you can. Running anti-lag like that should be reserved for trying to make boost in no load conditions, like just before launching and during shifts and only when racing.

It's an oversimplification to answer the question without getting deep into tuning theory. My main point in offering this tidbit was that the ability to tune the timing can take away some of the lag. When I say "tune the timing", I don't mean retarding it across the board I mean retarding those VE bins at which point you are trying to generate spool. When I say "retard the timing" I mean less advance not necessarily after TDC.

Synopsis; if you are building a turbo car, have a way to tune ignition, have it tuned and you will get much more out of it. Hope that clears some of this up.

No, when you're trying to spool the turbo while actually under load, IE in gear, more timing advance spools faster and generates less lag. This isnt a concept subject to debate.

Yes, advance to speed up spool up, retard to build boost for launch. Sorry too many things going on at once. The Synopsis is still the key point I was trying to get across and still very much correct.

Tuning is the easiest part once I get the engine running. I am leaning towards the single turbo setup for simplicity. I Have the header sections that will get cut up and a Y pipe welded with appropriate flanges. However, if there is a reasonably priced stock turbo from a junkyard I would go for the TT setup just for the coolness factor. @bluej brought up a good source in the VTG systems. EFI would make this easy to control as its probably a PWM signal to open and close the actuators.

While 300HP is the goal I would certainly be happier with more. That would be the minimum number. I would like to reach this at or below 1bar of boost. The engine is from a Porsche 911. Lots of info for the larger motor builds that are tried and true with excellent results. The car has a target of 2200# and will have a gearset that is as closely matched to the power band and torque approximations.

I want to build a small, quick revving, high rpm motor. There is a possibility that it could also transition into a class limit of 2.1L turbo (due to boost multiplier) depending on how far down that road I go. There used to be poor turbo technology and therefore selection for small bore motors. I thought there would just be a larger collective audience than the air-cooled forums.

What are the small 1.6L engines using these days. Lots of examples of modern small displacement engines putting out 200HP with a single. They spool quick and die off about as fast. Maybe a twin would extend the dynamic range. I guess I need to start looking at some compressor maps.

Speaking of maps. I looked at the maps for the Borg Warner EFR6758 referenced above. It has a very small peak for efficiency. I will get some numbers and see how it lays out and the knee.

The car will be primarily street and backroad driven. So a little high rpm heat from the turbo charge will not happen that often. And I have rrom for a pretty large IC to cool things down. I am not against MeOH/water or potentially water-air IC thought it gets crowded in the engine bay.

If you think the efr map is sad looking you're going to be terribly disappointed at anything else you look at. BW makes the best compressor's in the business, they're always multiple generations of tech ahead of garrett. And Mitsu and Holset havent really come out with new compressors since the early 90s.