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Potato Camera Operator
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Discussion Starter #1 (Edited)
DISCLAIMER: I'm brand new to this stuff. If I'm dead wrong on any of this, I am more than glad to be told so. Don't pull any punches, and feel free to tell it like it is. I'm looking for a productive conversation, I'm not looking for a bunch of people to agree with my plan and tell me I'm awesome. If you disagree with any of my poorly-built theories, please tell me, and tell me why! I'm excited to do this, but I'm more interested in doing it right than anything else.


I've been waffling from option to option in terms of what I wanted to do with my Focus once I had the funds to get serious with it. I knew I wanted a high-quality and aggressive suspension set-up, which I now have; but I've been unclear on what I want out of the drivetrain. I know don't want extreme power, and I do know I want to keep it FWD. I've considered a high-compression 3.0 Duratec with individual throttle bodies, I've considered a high-compression 4-cylinder with ITBs, I've ever considered putting a built 2.0 in the car because I like the way they rev. For years, though, I've been certain that turbocharging was not the path for this car.

I guess at this point, I'm sick of waiting around to make up my mind, and I just want to get the car where I'd like it. Plus, I've now got TWO other cars I can chase my natural aspirations with (HA! GET IT?). So, I've made a deal which will be pointing my Focus in the direction of forced induction by way of a FocusSport (yes, it's old) turbo system. I found a low-mileage setup with a 28R and water-cooled conversion for dirt cheap, and have decided to pull the trigger. The system has right around 30,000 miles on it, and the seller is confident that everything is in perfect working order. Considering who fabricated and assembled the system, I have a hard time doubting him. Now for the current specs...

2006 ZX4 ST, 2.3L Duratec MTX-75
FSWerks Stage 2
Garrett GT28R (for sale once I have it)
Moving to a Garrett GT28RS (Disco Potato) before install
Bosch 42lb injectors
Water/oil cooled
Standard wastegate
Standard 2.5" downpipe
My own 2.5" mandrel-bent exhaust with only perforated-core resonators, no baffles
Bailey Motorsports diverter valve
GReddy Profec-B electronic boost control
AEM wideband o2 sensor
Torsen LSD
Exedy Stage 1 clutch and lightweight flywheel
SCT XCal 3
205/40-16 Falken Azenis RT-615Ks which are in big trouble once the car is running

The car:



The uses:
Occasional street cruiser: The car is no longer a daily driver and will be driven only in nice weather.
Autocross: Track days/nights are seldom and expensive. I will be filling in the time between them with autocross.
Open Track: The car will mostly see Lime Rock Park and Thompson Speedway in CT.

My Preferences/Taste:
Autocross dictates that I have absolutely as little lag as possible. I occasionally co-drive a car that uses and upgraded turbo with an inlet restrictor (class rules), and lag is an issue. As much as I adore the car, it is downright infuriating in tighter courses. Open road courses and street use do not make lag as dramatic as autocross does, but I'd still like it to be virtually undetectable in these situations.

The Long-Term: I will be installing everything as-is with the GT2871R so that I change the fewest variables as possible before I get the car running with boost. This will make tuning as simple as possible for Raffi, and allow me to enjoy the car and get used to the power. Next winter, I will begin preparing the car for over 300whp, which brings us to the main reason for this thread...

I know that combining high compression and boost has been discussed at no short length on this forum, and would like especially to thank Bryce for his posts on this subject. My understanding of the concept has been greatly improved from what it once was (none at all) already, but I'd like to know more before I pursue this with my own car. I'd really like the static compression ratio of the car to be around 10.5:1 when I build it, and am looking to make somewhere in the neighborhood of 15psi with the GT28RS. My best hazard at a guess for power/torque with this is somewhere around 340whp and 310-330wtq with stock cams and intake manifold. Iv'e got a few questions, though...

1. Can we get into a discussion about how the Cosworth intake manifold affects the torque curve of a forced induction car? I understand how it works with natural aspiration, but I'm not familiar with how compressed induction changes this. My current plans, in the interest of building torque as early as possible, are to keep the stock IM. I'd be more than happy to be talked out of this.

2. High compression. I've briefly looked into this, and I think it is an interesting path to take in the name of preventing lag. When I spoke with FSWerks earlier this week, I was assured that their lowered-compression (9.0:1) builds have proven to be reliable and fun to drive time and time again. I agree, but I'm looking for something that is as responsive and torquey as possible. I was informed that with a bump in compression, a compromise in timing would be their preventative course of action, leading to a possible nullification in peak power gains seen by a bump in compression. I am okay with conservative timing lowering peak power, but will it also negate my proposed gains in responsiveness? Please excuse my ignorance on this subject.

3. My current plan is to use either Cosworth or Carrillo Super A-Beam rods simply for the sake of using the best equipment possible. The Eagle rods offered by C-F-M do bring up a very interesting question, though. Are the others, which are 3x the price of the Eagles, truly worth the added cost in my application, or are the Eagle rods already excessively strong for a 330-370wtq application (I'd liek to give myself some room for growth if I decide to up the ante)?

4. I am confident that I will be able to make the Exedy Stage 1 clutch last at least through next season, as I drive in a pretty conservative manner. I don't power shift, I seldom drop the clutch, and I know how to rev match properly. If I decide to change the clutch in the future, is the Exedy Hyper Single pleasant to use on the street? The car will be seeing a lot of track use, but I still want it to have some damn manners on the street,

5. Ricer Question: Above all, I want this car to be fun; a overall visceral experience. If I can safely tune the car to make fire as much as possible, I'd like to do so. This isn't a show queen, but I will admit that a vehicle shooting fire on overrun will legitimately make me cackle. Ray's tow vehicle shoots 2 and 3-foot fireballs out of the side exit routinely, and there's pretty much nothing on this planet more enjoyable. It is to my understanding that if the car is tuned to be a bit lean on overrun and a bit rich on tip-in, fire will be encouraged. Is this true?


Proposed engine build: Here is what I'm thinking will net solid results and an enjoyable drivetrain. If you see any issues with this, please let me know what you would do differently. I'm open to any input!

-GT28RS
-3" turbo-back with wastegate exiting into downpipe
-Carrillo Super A-Beam or Cosworth connecting rods (will the Carrillo rods come with bearings?)
-Ranger crankshaft
-Cosworth main bearings
-FSWerks 10.3:1 forged pistons
-Head skimmed .030"
-Siemens 60lb injectors
-Stock camshafts
-Stock valves
-If applicable, upgraded valve springs
-ARP fasteners throughout
-Either stock or Cosworth intake manifold
 

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Potato Camera Operator
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Discussion Starter #3
I like where this is going. I am interested in a price on the gt28r when that time comes.
I think we can work that out sooner than later. If we are currently friends on FB (I think we are), I will start a group chat with the seller of the kit. Maybe we can work out some crazy-ass deal which works for all of us. If we are not friends on Facebook, make it so!
 

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Absolutely go with the aftermarket IM cosworth or otherwise.

Skip the high dollar rodsthey are way overkill for your goals. the Eagles will do just fine for your build.

High compression is the way of the future. These motors respond way better to compression or boost than they do timing. Top speed was running 12:1 compression and 93 octane until about 550whp. Although I don't know that they would recommend going that extreme to a customer.
 

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Potato Camera Operator
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Discussion Starter #5
Absolutely go with the aftermarket IM cosworth or otherwise.

Skip the high dollar rodsthey are way overkill for your goals. the Eagles will do just fine for your build.

High compression is the way of the future. These motors respond way better to compression or boost than they do timing. Top speed was running 12:1 compression and 93 octane until about 550whp. Although I don't know that they would recommend going that extreme to a customer.
If I were to go about building my own intake manifold, I'd think a reduction in plenum size and slight increase in runner length in comparison to the Cosworth would help produce low-end torque, yes?

How much do you know about the Eagle rods? My concern is that the prints and spec/standard lists for the parts are all trade secrets, meaning I can't make a true comparison of the three on paper. My goal, when upgrading the car, is to use only parts which are engineered to as close to OEM standards as possible. Though I know the materials are higher-strength and the basic dimensions are proven to provide increased strength, I just wish I were able to really rip into these designs and start to understand why each manufacturer decided to design their parts in the way they did. I guess my only bet is to go by real-world results at this point.
 

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I know that pretty much every 500+ whp build on this board has been done with eagle rods. That is enough for me, I wouldn't think twice about it. I talked to a guy at eagle years back that said they have 4 cyl customers doing 900+

You don't need to get crazy with the IM for what you a are trying to do, certainly not a smaller plenum. Don't worry about the torque you will have plenty.

More than 250wtq will overwhelm the stock size tires anyway. Putting down more torque than that to the wheels requires larger 235 or 245 tires and a boost controller that will do boost by speed/gear. The novelty of roasting the tires wears off quickly. When set up correctly my car would barely haze the tires in first and second, then hook and go like stink in 3rd and forth. I wasn't able to put down more than about 350-375 torque to the wheels on street tires even in 4th gear.
 

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I believe he's not talking about increasing torque at full boost, but more so when it's actually not in boost at all. That's some of point of going high compression. Out of boost, it should drive the same or even better than the stock naturally aspirated engine. The Cosworth intake sacrifices low end torque for more top end pull. He may be thinking of a happy medium between the stock intake and the Cosworth.
 

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Potato Camera Operator
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Discussion Starter #8
I know that pretty much every 500+ whp build on this board has been done with eagle rods. That is enough for me, I wouldn't think twice about it. I talked to a guy at eagle years back that said they have 4 cyl customers doing 900+

You don't need to get crazy with the IM for what you a are trying to do, certainly not a smaller plenum. Don't worry about the torque you will have plenty.

More than 250wtq will overwhelm the stock size tires anyway. Putting down more torque than that to the wheels requires larger 235 or 245 tires and a boost controller that will do boost by speed/gear. The novelty of roasting the tires wears off quickly. When set up correctly my car would barely haze the tires in first and second, then hook and go like stink in 3rd and forth. I wasn't able to put down more than about 350-375 torque to the wheels on street tires even in 4th gear.
Thank you for all of your input. The Eagle rods are starting to really look like a good option, and I did see on their site that they rate the rods for 900+ HP in a Duratec application. That's a pretty confident number.

I would think a smaller plenum would help build torque sooner, but please correct me if I'm wrong.

I've got 3-piece wheels, so widening them to fit more rubber as needed is not an issue.


I believe he's not talking about increasing torque at full boost, but more so when it's actually not in boost at all. That's some of point of going high compression. Out of boost, it should drive the same or even better than the stock naturally aspirated engine. The Cosworth intake sacrifices low end torque for more top end pull. He may be thinking of a happy medium between the stock intake and the Cosworth.
That's pretty much exactly my point. I'd like the car to retain solid torque off-boost, which to my understanding will also help it spool the turbo as quickly as possible.
 

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I believe he's not talking about increasing torque at full boost, but more so when it's actually not in boost at all. That's some of point of going high compression. Out of boost, it should drive the same or even better than the stock naturally aspirated engine. The Cosworth intake sacrifices low end torque for more top end pull. He may be thinking of a happy medium between the stock intake and the Cosworth.
But an increase down low comes with an increase in midrange torque which brings traction problems once the torque goes up beyond 250ish to the wheels. If you want more down low go with a smaller turbo that will give more boost sooner. I would reccomend an aftermarket short runner IM for ANY turbo Build regardless of your target goals.
 

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You want just the opposite with the IM. Turbos like big plenums and short/fat runners. The plenum is more important here than the runners. The point of different runner sizes and lengths is to manipulate air velocity and intake air pulses. With a turbo forcing air into the engine, this becomes obsolete. So you just run short runners to get the air to the valves as fast possible with the least amount of restriction. The Cosworth isn't even ideal but it's the best option we have.

As for tires, I'm looking to run a 255-275 tire up front on the street with widened fenders. This would also be overkill for you though. Find a good set of 235/40r17 summer tires to run all around.
 

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I guess what they are saying is you're screwed if you want any bottom end torque when out of boost, or running a smaller turbo so you have bottom end via boost but you'll sacrifice the top end for that. Either that or they still don't understand what you want out of it.
 

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What we are saying is he doesn't need it. I had a set up like he is talking about, stock cams and intake all the way from 250tq/250hp to 450/450 and it sucked. When I changed my setup and made 240/310 300/400 and 430/560 it was way better. sR Performance and I are speaking from experience you guys are theorizing. When you have 350hp on tap you won't be putting around at 1200-2000 rpm trust me. Even so the turbo is always making boost all long as you are on the gas. The turbo you have selected will be small even for your goals. I wouldn't go smaller than a 2871 on a 2.3. Like I said I reccomend the aftermarket IM regardless of your hp goals
 

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I made 230whp/215wtq with the stock head and IM. Swapping o
to a 2.3 head and Cosworth IM, I made 284whp/229wtq at the same boost pressure, had a much broader torque curve, and got better traction than it did with less power and torque simply because the stock plastic intake was spiking torque at low rpm which broke the tires loose where as the Cosworth brought the torque in gradually which allowed the power to be put to the ground much more effectively and keep traction. The factory 2.0 head and intake made more torque only where it spiked at about 3300-3600rpm. The Cosworth manifold made more torque everywhere else including out of boost.
 

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Potato Camera Operator
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Discussion Starter #14
I'm looking for the car to be as responsive and usable as possible. I had originally posited that big low-end torque would be the answer to that, but I think I may have been barking up the wrong tree.

Thing is, even if I make stock torque below 3000rpm, that's not a big disappointment, as the car has plenty of grunt down there to begin with. If I'm going to just spike boost in the lower-midrange and blow the tires away, I won't be making any use of it.

Sent from my SM-G920V using Tapatalk
 

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Potato Camera Operator
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Discussion Starter #15 (Edited)
I'm going to be upgrading the turbo when I install everything, so I've got a few questions:

-I'm in the air between a GTX2863R with a .86 A/R turbine housing, and a GTX2867R (.64 A/R). I'm leaning towards the GTX2863R since the smaller compressor should help it spool a little faster than the 67 in spite of the larger turbine housing. Can anyone corroborate this? This has been an interesting debate between Chaz and I over the last week or so.

-Will either of the aforementioned turbochargers interchange with the turbine housing off of my GT28R? I know the wheels are different, but I cannot seem to figure out if the wheel profiles were changed, not just the internal dimensions.

-Talk me out of Garrett and into Precision Turbo. The cost is certainly lower, but I'm a strong believer in the use OEM quality or better whenever possible. If you can talk me into the belief that Precision turbos are of equal or greater quality than Garrett, I may consider the more cost-effective option. Value is not at ALL a priority with this project, but I also don't like spending money for the sake of spending money.

-My power goals currently are right around 300whp, and Vik seems to think that a 3" exhaust is not at all necessary. I have a tendency to agree with him. Thoughts?
 

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Go with the 3067 in a .63 ar. I have determined this is the perfect turbo for a primarily street driven focus.

Forget precision turbos Garrett is the way to go. I've never seen any problems out of a Garrett bought new, I've seen lots of precison, comp and other "performance tuned" turbos that's don't last long and are nothing but trouble.
 

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Discussion Starter #17
Go with the 3067 in a .63 ar. I have determined this is the perfect turbo for a primarily street driven focus.

Forget precision turbos Garrett is the way to go. I've never seen any problems out of a Garrett bought new, I've seen lots of precison, comp and other "performance tuned" turbos that's don't last long and are nothing but trouble.
Thanks (as always) for the feedback, Jared. So you feel the smaller A/R with a larger compressor is the way to go because it'll spool faster, or because it'll have smoother power delivery? Keep in mind, the car will be used in competitive autocross, so I'd rather have the power available way down low and not use it (keep the car off of full boost) than to not have it as an option.

That's pretty much exactly what I wanted to hear about Precision, as it was what I had suspected was the case.
 

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The gtx3067 is supposed to have lighting fast response. I think with the 2.3 you will be better off with the 30 and a .63 ar than the .86ar in the 28. If you had a 2.0 I might would go with the 2863 for what you are trying to do with the car. The 2863 is just too small for the 2.3.
 

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Thanks (as always) for the feedback, Jared. So you feel the smaller A/R with a larger compressor is the way to go because it'll spool faster, or because it'll have smoother power delivery? Keep in mind, the car will be used in competitive autocross, so I'd rather have the power available way down low and not use it (keep the car off of full boost) than to not have it as an option.

That's pretty much exactly what I wanted to hear about Precision, as it was what I had suspected was the case.

I'm going to second this. You're going to spool at a decent rate, have a nice, linear boost curve that's usable, and you'll be able to pedal modulate power on corner out. The smaller A/R should allow you to be in boost by 3k. Find the compressor map for this and we can verify. I'd grab it but i have to go back to work in 15 minutes and i don't have time to punch more numbers.

What are you doing for your differential? Without a proper diff, forget corner exit at autocross speeds, you're going to immolate the inner tire. Also, we'll have to work on your footwork, but we can practice that in Miss Daisy for smooth pedal inputs, Mr. I spin. All this being said, for autocross in a somewhat light FWD car, anything over probably 240wtq you're going to have the option of lighting the fronts in 1st / 2nd gear at whim. There is power, and there is usable power. Track days are different.

What i don't want you to do, is do all this work, spend all this money, and have a car that's physically slower around the cones than when you started. Autocross isn't about sledgehammers, it's about scalpels. (Coming from the owner of a guy with too much horsepower but neener neener).
 
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