Rebuilt SR20DET Turbo Selection

[Quiche2192]

So I've completely rebuilt my SR but I'm having trouble deciding which turbo to get because of a couple reasons I'll explain. Let me share the setup:

- 400 WHP goal
- 9:1 compression ratio
- 93 Octane pump gas
- Stock intake and exhaust manifolds
- Stock ECU with RS Enthalpy tune

Here's the thing that's holding me back:

- I really want to maintain the stock exhaust manifold. Don't want to deal with cracking manifolds, and I like the subdued bottom mount.

- I've been looking at the G25, and the GTX2867R Gen II. Mainly looking at the GTX2871, because they make a drop in for the SR.

- I keep hearing the G25 is worth it, so I looked and they only offer a T25 version of it with a .49 A/R. Is that too small of an A/R and will it cause back pressure? Where can I find more detailed technical info about this?

- With the smaller A/R, if back pressure is no issue, would it make sense to go with a G25-660, instead of the 550?

https://imgur.com/IfplzM2

[pacotaco345]

400 wheel is pretty ambitious on pump gas with a bottom mount turbo.

To make big numbers on pump gas you need cool-ish air coming out of the turbo with big boost and as little backpressure as possible. 93 octane will be knock limited, and a stock t25 frame turbo with a small exhaust housing will create backpressure and raise EGTs, even something as modern as a g25.

A t3 twin scroll top mount gtx3071 is probably the best option for making 400 wheel with relatively good response, a turbine housing that won't restrict the motor and a manifold that will spool the turbo.

If you lower your power goal to 350 the 2867 on a stock manifold would be an excellent option, or if you run some better fuel that same turbo will make 400+ easily. Take it from someone with a flex fuel bottom mount SR. Mine makes 330 on pump and 410 on e70 ish. This is all with a gtx2860 gen 2.

[burnsauto]

Two factors that will help you make your decision. How much boost you want to run, and when you want it to spool. The 660 in theory would make the same power on lower boost compared to the 550. I'm always a fan of slightly oversizing the turbo, just so you're not pushing the thing to the limit, but the 550 seems to be in that ballpark, where the 660 would be a bit overkill for 400 hp. As far as the A/R's, I looked into it a bit, and comparing it to the 2871R, I see that they run larger trims for the 550/660, but that seems like a really small A/R compared to the 2871's smaller .64.

If it were me, I'd be leaning more toward the 2871, it's a tried and true size that lots of people use to hit that power level, and with the smaller A/R I hear that the spool up isn't too bad, but with the larger one it can feel a bit laggy.

This may of helped, it may of not, but good luck on your decision either way

[Kingtal0n]

The 2871 w/ 64 small exhaust back housing + poncam 256

for almost 20 years ,
Ideal 350rwhp range for stock bottom end sr20det (92-02) for novices

You can push 2871 to 400 Ive even see 420-450rwhp but it takes alot more experience and careful considerations, tuning, heat control, etc... (It costs more and there is more chance to make a mistake) for the extra 50~ hp.

I recommend sticking near 350 until you become a master of tuning sr20det engines then try the 400~ range on a T25unit if thats still your idea of a good time

Top mount varieties are generally superior in almost every way except cost. It can spool superior, make more power, control heat better, easier access, everything gets better. Even the turbo can be reduced to 1/3 cost (brand new Borg Warner unit IMO). However the placement and fabrication aspects, combined with required knowledge of bracing and flexibility in the plumbing (so nothing will crack) and vibration damping make it a difficult job and may lead to breakage and leaking if the owner/installer is not familiar with all of that setup involved. It can also be difficult to find a top mount manifold which has good access to certain parts (a/c stuff, wastegate positioning, turbo feed lines access, bolt tightening access, etc... can be dicey on a LOT of versions)

other thoughts:
once we pass the ~440rwhp barrier an old 2.0L is stretched a bit thin in a daily driver situation (If thats your goal)
I recommend for up to 400rwhp the 2.0L Is a great engine
For 450-650rwhp I recommend the 3.0L 2jz-gte (daily drivers around 3000lbs its great)
And for 650-1000rwhp use the L33 Engine (5.3L From 2005-2007 Silverado)

All of those engines can keep OEM stock bottom ends so there is no down time, no machine work, etc... And they are all similar priced and will easily go 200,000 miles with the stated power in capable hands

[Quiche2192]

Wow, thank you so much for the great replies everyone!

I see that 400 HP is a lofty goal. I have limited experience with all this, so I didn't really have a perspective on my power goal and setup. But now I have a better idea.

I did not consider the temperature as a factor when considering top or bottom mount, so thanks for pointing that out.

I do value reliability and simplicity way more than performance. I also value response over top end HP numbers. I'd be very happy with anything over 300 HP to be honest.

I'm leaning toward the GTX 2867R Gen II. Any thoughts? Would a GTX2871R be another good option? I think the 2871 would be slightly more laggy than the 2867, and the 2871 would have a bit more top end, right? I'm wondering if the 2871 would be a good compromise. Any notable improvement with the Gen II GTX's over the Gen I GTX's?

[burnsauto]

Gen II's have improved compressor wheel/compressor housing vs. the Gen I's. They should flow more and spool faster than the Gen I's (in theory, other factors - the rest of your engine setup - come into play). The GTX2867R would be a good turbo for the 2.0. With the smaller .64 A/R I think you should hit the power levels you're going after. The Larger A/R will hit higher numbers, but be more top end. With these smaller engines, it's always a compromise, so it all comes down to the type of driving the car will see, and build the engine around that idea.

[PoorMans180SX]

The .49 housing is not too small.

This is SR20, BC264 cams, and the G25-550 with .49 T25 housing on E85. Makes 285whp on 91 octane on a conservative tune.



The 2871r is a laggy bitch that is far surpassed by newer turbos. GTX2863, GTX2867, and even the GTX2860 Gen II are far superior turbos IMHO.

[burnsauto]

lol, a laggy bitch. One of the better descriptions of a turbo I've heard.

[pacotaco345]

I'll still stand by gen2 2860 is the best turbo you can put on an SR. A gen2 2863 or 2867 will have a little more headroom but these turbos are so efficient now it's crazy.

The lower line is on 93, the higher line is on e67. It was also about 100* in the shop where the car was being dyno'd.
Untitled by pacotaco345, on Flickr

[Kingtal0n]

93 octane gasoline is good for at least 340lb-ft and 410rwhp for a 2.0L

Even using 17 year old turbo tech such as 50-trim and 60trim style journal bearing $300 rebuild pieces of shit turbo can make those numbers.
A 50 trim will give 300lb-ft of torque around 4000rpm easily and top out 400rwhp no issues. And a turbo shop will give you that wheel free because nobody wants it since 15+ years has gone by. And this is 93 octane fuel gasoline only.

For alcohol the minimum power is 500rwhp otherwise you would just be using gasoline. And there is no reason to see a gasoline 2L making less than 400rwhp. It doesn't make sense from a promotional point of view. At low power, alcohol is merely a clean burning fuel and a safety margin, not a performance enhancer.

Turbos have not gotten much more efficient. In the old days they are (64 to 67% baseline) up to 74% to 76% efficient. Now they are up to 75 to 76% efficient. They gained maybe 1-2% over the last 10 years or so. The big difference in turbos now isn't efficiency it is capability, metallurgy, design process, material science, etc... engineering and materials properties have increased their flow rate while maintaining a low wheel mass which allows them to support more power and spool more quickly- but it does not improve their efficiency as compressor adiabatics for impeller style pumps impart heating of the air due to friction which cannot be negated in the design of the turbo or compressor but rather has to do with the air interacting with itself and surroundings under the circumstances of compression.

In turbo decision it is ultimately the application which calls for flow rate (mass rate) throughput and adiabatic targets. For example in a drag racing app with nitrous/2-step if the target power is say 1000rwhp you would choose a compressor capable of supporting 120-150lb/min (higher wheel mass than necessary) to keep the operating adiabatic island near a comfortable center point while negating the additional wheel mass by using nitrous and spark strategy. However in a street application for 1000rwhp that will never see a race track or nitrous you would want a compressor which can only flow roughly 105 to 110lb/min to minimize wheel mass. The question of 'when will it spool' and 'which turbo is more efficient' is never considered in those efforts because mass throughput and application supersedes whimsical desire for a faster spooling turbo which may not exist (it won't be easy to tell without comparing each turbo in the exact application and situation since they are all so similar in the same mass-rate range)

[Kingtal0n]

Example: 50-trim and 60-1 on an sr20 using 93 octane gasoline in 2007


Notice full boost around 4000rpm and approx 300lb-ft of torque near 15psi of boost for the 50trim turbo and it maxes out near 400rwhp on a dynojet

The 50trim turbo cost around $300 or less. Somebody gave me the wheel free locally in fact for this test. Thus, the least performance or minimum performance any sr20 should have using gasoline fuel and a free turbocharger (very inexpensive) is shown.

If you intend to sell somebody on the idea of a $2000 turbo, while there is no question that garret makes the best turbo in the world, it should be a significant upgrade over the 50-trim 'free' turbos from 15 years ago. In other words, I wouldn't pay an extra $1700 for an additional 40 or 50rwhp if that is what was being offered, with similar or even slightly superior spool. Not to mention you can rebuild a 50-trim journal bearing turbo as much as you want while the BB garret units are one-time use. Too much $$ lost for too little gained and if the goal is using gasoline only then there is no purpose or reason for the 450+rwhp capable units anyways (mass-rate supersedes all)

[PoorMans180SX]

I can see what you're saying from a budget perspective. However, I still disagree with you on your "less than 400whp is pointless". Have you ever driven a two liter with a new tech turbo at 300+whp? It basically feels like a small block V8. It presents it's own challenges to be sure, but boy does it make it fun. I'm sorry but your 50 trim plan will never do that. Taking until 5000rpm to make over 300lb-ft just isn't impressive.

[Kingtal0n]

Originally Posted by PoorMans180SX

I can see what you're saying from a budget perspective. However, I still disagree with you on your "less than 400whp is pointless". Have you ever driven a two liter with a new tech turbo at 300+whp? It basically feels like a small block V8. It presents it's own challenges to be sure, but boy does it make it fun. I'm sorry but your 50 trim plan will never do that. Taking until 5000rpm to make over 300lb-ft just isn't impressive.

50trim T3 style turbo can be as fast as newer turbo. You can't go by torque because cam phase, tuning, the entire setup will mediate torque and at low flow rates, none of those turbos will be blowing hot air yet (sub 5k is same temp air for the most part) so there is almost no difference for low rpm performance between them. My graphs are almost 20 years old and that plays a role in what I was doing back then. Also keep in mind 350hp at 4000rpm is 450lb-ft of torque, so any turbo can rival "SBC torque" approaching 3500-4500rpm ranges given they all flow more than 350hp.


The new garret stuff isn't better because it spools faster than X. An old T3 turbine housing is extremely efficient, even compared to new stuff, because efficiency is only increasing 1 or 2% over the last 15~ years. The weights of the shaft are similar and energy is energy, exhaust is exhaust, there is no magic bullet for that.
The new garret is superior because it can support more flow rate on the top end and highly boost with less leaking, superior manufacturing, etc... they are more tightly designed, balanced, better materials in theory, small changes to the housing and wheel, stuff learned from computer aided design and stress testing over many years.

I tuned a couple small turbine garret versions and they do not impress me for the price, turbine is too small, boost too high, and the packaging from mazworx sucked although that isn't garret's fault. I found myself being fickle with the meth addition rate approach 25psi of boost, very hard with Power FC to blend the maf tuning for a stand-alone meth system into that. But I digress

The turbos that impress me are the physically large EFR and similar variety, may not spool so fast but give the 2L 3L the top end it deserves without the tiny turbine and high boost pressure. And they are much cheaper, BW turbo you can $450 for the unit or around $800 complete I think. And they support any power you want top end with as big of a turbine as you want... I'm a big turbine fan


I never suggested anybody buy a 50 trim turbo btw, I am not even sure where you would get one these days or if they exist. I was just comparing the 'free' turbos with the $2000 turbos in a comparison contrast situation. If I knew this day was going to come I would have spiked up the boost a bit on my original graphs to show 350lb-ft of torque before 4000rpm to get you guys some idea. It is absolutely easy and possible I was just being careful in 2007 as a new to 2L tuning, heck I just found out what a skyline is around those years and still had an SBC in a car somewhere.

As always appreciate the discussion, if you really want a nice comparison maybe dig up some more dyno graphs. I've seen one from Enthalpy where he tuned like 600lb-ft out of a stock 3L by 3200rpm or something ridiculous I forget what turbo though. Its nice to compare.

[PoorMans180SX]

I think when most people use the term "efficient" they're talking about the flow rate per wheel size. That's the advantage of new technology. These smaller turbos are outflowing old-school turbos of quite a bit larger size, both on the compressor and turbine side of things. You can't argue that the inertial advantage of a smaller rotor group isn't significant when it comes to response time.

I'd agree that the bigger EFRs are the most impressive turbos I've experienced. The first time I drove a car with an 8374 on it, I thought it was a bolt-on upgrade turbo it was so responsive.

This is definitely an interesting discussion to me. I don't know if you can really factor in budget though. There are plenty of great budget turbos out there, but a reliable turbo system pretty much ends up costing the same price regardless of the combination. If you go T3 you need a good top mount manifold, if you do twin-scroll the same, hard use bottom mount setups need special studs and the stock manifold will probably crack eventually, etc, etc. Seems kind of a moot point.

I think it really just comes down to what the car is for and what kind of torque curve you want. I like a really snappy turbo for street cars, it's much more fun to have that kick in the ass torque whenever you need it IMO. This only really happens with small turbos or a medium turbo with a divided exhaust housing.

[Kingtal0n]

Originally Posted by PoorMans180SX

I think when most people use the term "efficient" they're talking about the flow rate per wheel size. That's the advantage of new technology.

Exactly why I keep saying efficiency hasn't changed much-
1. is there are more than 1 type of efficiency?
2. the term 'efficiency' with respect to pumps and turbos has always been adiabatic efficiency
2.5 Adiabatic efficiency is what fluid mechanics book will discuss for all pages when it says 'efficiency' this I have taken to be the correct use for the term (but not it's only use)
3. Be aware of the difference flow rate per wheel size, and adiabatic efficiency.

All compressor wheels have roughly the same efficiency island (around 76% usually) potential thus they are all equally efficient for more than 20 years

Flow rate is a setting for fluid velocity through some area and when temperature and type of fluid is included the density is known which gives mass fluid rate, thus 'corrected' numbers you see on compressor wheel maps are highly variable depending on input temperature, making temperature a key component of adiabatic efficiency discussion AND flow rate in mass or velocity.

The limitation of a wheel to higher or lower velocity is part of it's construction. Flow rate per wheel speed size is a function of integrated engineering approaches and has little to do with adiabatic efficiency, which hasn't changed.
Adiabatic efficiency varies with wheel speed and pressure, Which are flow rate volume and pump head respectively.

TO give an example why this distinction is important, consider two identical turbochargers.
Two turbos are identical except one cannot exceed 40,000rpm, and other can spin 80,000rpm.

Do we say the one that can spin a higher is more efficient? Not generally. Just because it can spin faster does not make it more efficient unless the speed limitation has something to do with friction. There are multiple ways to ruin a shaft and disrupt energy transfer which is the point of this discussion. If we say the limitation is due to metallurgy; i.e. the wheel is made of some cast material which would disintegrate after 40,000rpm, then it has nothing to do with efficiency, It might be more well constructed or something like that instead of being more efficient.
Although there is more to flow rate than wheel speed, it was a easy way to show why 'efficiency' can be mis-used when the device in question is dependent on so many variables.

It is important distinction because,
No matter how much 'better' turbos get the need to intercool 200, 400, 800(or any number)hp worth of air isn't changing because adiabatic efficiency is always similar (no free lunch)

These smaller turbos are outflowing old-school turbos of quite a bit larger size, both on the compressor and turbine side of things. You can't argue that the inertial advantage of a smaller rotor group isn't significant when it comes to response time.

Load and time spent under load is an important aspect to this discussion. With a load dyno you can hold a engine at low rpm and load it for as long as it takes to build to some huge boost number and then say look I made XYZ at 2500rpm or something stupid.
So when we start looking at dyno graphs and trying to compare response or spool character, it must be done using the same exact dyno situation and dyno electronics and dyno roller weight and vehicle tires/drivetrain/etc and gear ratios. Otherwise the load will be inconsistent and the turbo will look better or worse on paper because if the load is reduced the engine will accelerate more quickly and the turbo will appear to spool slower. This is why 1st gear spool is always terrible looking on paper and why a 5th gear overdrive dynopull can make the turbo look like is spool really fast on paper.

All my dynos are always done on dynojet. This keeps load from the roller weight consistent at least. And dynojet calculates power from roller mass so there is no fooling it. To compare cars more equally.

I recommend anybody interested in 'turbo spool' consider these things carefully.

Now- about the response and fast spool behavior, I don't see that it makes much difference for daily drivers or drag cars anymore, maybe some other racing applications where exact gear ratio situations (coming out of a specific corner) require fine tuning that last 500rpm of spool from the turbine... but in most daily driving situations you can just downshift or avoid being at a very low rpm in the first place. A stock turbo can blow the tires off of first gear, response is unwanted after some point. The onset of boost should be tire sparing and keep the car from spinning so a slower rate of boost building is desirable and fine-tunable in the best situation. IMO daily driving favors a larger turbine lazier spool when the power at 2L is around 400rwhp+ because it ensures lower EGT and wider tuning window, safer on gasoline especially.

This is definitely an interesting discussion to me. I don't know if you can really factor in budget though. ....Seems kind of a moot point.

Ah, you got that right. Turbo can be free still can cost 5k for a setup.
In future issues, potentially blown turbos, engine failure -> turbo replacement, stuff like that happens and its nice to be using a more affordable unit.

I think it really just comes down to what the car is for and what kind of torque curve you want. I like a really snappy turbo for street cars, it's much more fun to have that kick in the ass torque whenever you need it IMO. This only really happens with small turbos or a medium turbo with a divided exhaust housing.

it looks like a 'small' turbo these days is 500hp and they seem to do well with response and tolerate a wide range of abuse. 500 is apparently 'low' power now

[PoorMans180SX]

Originally Posted by Kingtal0n

Load and time spent under load is an important aspect to this discussion. With a load dyno you can hold a engine at low rpm and load it for as long as it takes to build to some huge boost number and then say look I made XYZ at 2500rpm or something stupid.
So when we start looking at dyno graphs and trying to compare response or spool character, it must be done using the same exact dyno situation and dyno electronics and dyno roller weight and vehicle tires/drivetrain/etc and gear ratios. Otherwise the load will be inconsistent and the turbo will look better or worse on paper because if the load is reduced the engine will accelerate more quickly and the turbo will appear to spool slower. This is why 1st gear spool is always terrible looking on paper and why a 5th gear overdrive dynopull can make the turbo look like is spool really fast on paper.

All my dynos are always done on dynojet. This keeps load from the roller weight consistent at least. And dynojet calculates power from roller mass so there is no fooling it. To compare cars more equally.

I recommend anybody interested in 'turbo spool' consider these things carefully.

Now- about the response and fast spool behavior, I don't see that it makes much difference for daily drivers or drag cars anymore, maybe some other racing applications where exact gear ratio situations (coming out of a specific corner) require fine tuning that last 500rpm of spool from the turbine... but in most daily driving situations you can just downshift or avoid being at a very low rpm in the first place. A stock turbo can blow the tires off of first gear, response is unwanted after some point. The onset of boost should be tire sparing and keep the car from spinning so a slower rate of boost building is desirable and fine-tunable in the best situation. IMO daily driving favors a larger turbine lazier spool when the power at 2L is around 400rwhp+ because it ensures lower EGT and wider tuning window, safer on gasoline especially.

I'm really talking about actually driving the car. While we can extrapolate some data from a consistent dynojet figure, it's really all about how the car actually goes down the road. Downshifting takes a lot longer than pressing down a pedal, and it's much easier to shock the drivetrain into wheelspin. If I can simply push the throttle down and accelerate, that's ideal.

Yeah I'm used to driving 300-800whp Evos and STis on the street. These guys aren't afraid to spent some good coin on sticky tires and awd makes the traction thing a lot less of an issue.
Speaking hypothetically, I get if you're on 235 400tw tires or something, but if that's the case I'd say build your wheel and tire setup for the power you're making.
On the other hand, maybe learn to control your right foot and the car? Breaking traction might be easy, but it's also not hard to learn some finesse. I'd rather be able to break traction at all times than to not have the power when I want it without having to make a gear change. There's always unexpected situations in daily driving, like you didn't see that car while you're pulling out, etc. You can't always account for being at low rpm.

I totally get the tuning window aspect of it, pump gas can be a fickle beast when it comes to big, low rpm torque swells and boost spikes, especially if the intercooling system is sub-par and heat soaks. I still think a conservative tune with nice low-end grunt is more fun to drive than something with an S2000 like powerband on the street. I've driven 450whp Evos that feel lethargic even though they basically have a linear powerband after ~4500rpm. The bolt-on 18K cars are much more fun, and make the same power when switched to E85. Then again, my friends 2.2liter 7670efr makes 450+wtq and feels like the perfect hybrid of the two. There's about $6k difference between the two setups though.

[Kingtal0n]

Originally Posted by PoorMans180SX

I'm really talking about actually driving the car. While we can extrapolate some data from a consistent dynojet figure, it's really all about how the car actually goes down the road. Downshifting takes a lot longer than pressing down a pedal, and it's much easier to shock the drivetrain into wheelspin. If I can simply push the throttle down and accelerate, that's ideal.

Yeah I'm used to driving 300-800whp Evos and STis on the street. These guys aren't afraid to spent some good coin on sticky tires and awd makes the traction thing a lot less of an issue.
Speaking hypothetically, I get if you're on 235 400tw tires or something, but if that's the case I'd say build your wheel and tire setup for the power you're making.
On the other hand, maybe learn to control your right foot and the car? Breaking traction might be easy, but it's also not hard to learn some finesse. I'd rather be able to break traction at all times than to not have the power when I want it without having to make a gear change. There's always unexpected situations in daily driving, like you didn't see that car while you're pulling out, etc. You can't always account for being at low rpm.

I totally get the tuning window aspect of it, pump gas can be a fickle beast when it comes to big, low rpm torque swells and boost spikes, especially if the intercooling system is sub-par and heat soaks. I still think a conservative tune with nice low-end grunt is more fun to drive than something with an S2000 like powerband on the street. I've driven 450whp Evos that feel lethargic even though they basically have a linear powerband after ~4500rpm. The bolt-on 18K cars are much more fun, and make the same power when switched to E85. Then again, my friends 2.2liter 7670efr makes 450+wtq and feels like the perfect hybrid of the two. There's about $6k difference between the two setups though.

Well first consider not all cars are manual. There is a very narrow window of manual transmission cars with a broad range of power used in a similar manner- I assume mostly street 300-500hp fooling around stuff.

I understand the scope is lightweight rwd 2L~ cars but the turbo specific behavior has to reflect the sort of use, whether it is indeed "street" car or used in some kind of racing. The racing efforts where rules are in use will need reflect the efficiency range of the turbo used, with support from fuel quality in that range. While street stuff may not need to be perfectly dialed in since ever situation is random or can be random from light to light. And highway roll racing stuff can be 40mph or 60mph or whatever.
thats the issue with street setups- anything goes or can go. It isn't the same corner and downshift (or not downshifting with the right turbo) in every single race or trial.

This reveals an overwhelming issue of torque management, or simply boost control per speed or RPM or Throttle position. The faster a turbo spools the more difficult it is to control the boost with your right foot, the more important it is to control the power using electronics instead of your right foot. The more emphasis on modern closed loop boost control and wastegate operation becomes. Small, high flow turbos using high boost are excellent candidates for manual transmission cars when the boost control is dialed in properly to match the current use, per gear and terrain.
Boost control as that can be difficult for the average enthusiast, and anybody whos ever tried to hold the boost halfway between 0psi and 25psi to maintain traction with any kind of turbo is going to realize it isn't possible to keep boost pressure as a steady line with the right foot alone.

So it isn't really a turbo issue, its a control issue. High boost pressure is not bad for an engine- but the fact that it needs to rise so high in such a short time can make it difficult to control, and maintain through gears, its it's own problem and set of issues.

Whereas a larger turbo running less boost and spooling a bit more gradually is far easier to control, both from electronic point of view and with the right foot. It may be more 'civil' in a street application and predictable as well.

It depends on how far the owner operator is willing to go in terms of control theory, micro controller management, frequency response, that sort of thing will determine how well the small peaky spiky graphs will work for your car.

added:
In other words, if someone can conquer the issue of boost control to make exactly the amount of torque(boost) needed at any given instant, that is a real time traction control for max torque, ideal torque for any situation at random on a street
Most turbos and especially with alcohol fuels can boost 30 to 40psi to make any torque desired for it does not tax mass flow rate to make a high peak torque

also added:
personally I would not put a turbo less than 50lb/min on any 2L
the smallest turbo for any car is 50lb/min is my basic tenant for all 2L+ no matter how they are used in 2500-3500lbs vehicles.

Application sets the turbine. Drag racing buy the biggest turbine. Long racing situations, overdrive gears you want to keep the EGT as low as possible so the largest turbine lowest pressure wins at constant output. On the highway all the time, use a large turbine for those 80mph roll races. Especially in drag where the driver never lifts from the throttle, it just gets up and stays up, none of this talk about response makes any difference. The less strictly drag the smaller the turbine gets until its small enough to produce boost on the coldest day after a cold start at some freezing temp outside while not being on a highway, stuck in normal traffic stoplight stuff. Your coldest environment has the smallest turbine for those cold stoplights waiting for the heat to start working. The engine can light that thing off at some 40*F to give you boost with 2L on those days from the factory.
The environment (temperature) is critical design factor in cars which frequent those climates.

[Mikester]

I wouldn’t call 400 a lofty goal, just one that needs to have the right stuff in the right place. IMO, it’s a fun and fairly dependable hp level for a properly built & tuned SR… key words being properly built & tuned. It can be done all day long on 93 pump gas and your engine will need to be able to breathe.

But I do agree with some of the above comments about the 300-350 hp range. Mine makes 385 on a Mustang dyno (over 400 on dynojet?) on pump gas. It’s fun as hell in boost but no fun spending most of the time in turbo lag. On the street, a smaller turbine with faster spool is way more fun. I run the Tomei MX8270. Fits nicely in the stock location. But in retrospect, I almost wish I had gone with the MX7960 or a 2871, lower overall power, but much faster spool, equaling more fun factor on the street.

Mike

[Mikester]

One other consideration is the drivetrain. KA/SR/CA transmissions get pretty sensitive to breaking with higher hp. Mine lasted lasted several years at 280-300hp. Lasted exactly two launches at 400 lol. On the third, the output shaft snapped like a twig. RB25/VG30 tranny might be worth adding to the list for a 350-400 goal.

Mike

[burnsauto]

OP: Small, to the point question without a lot of detail.

Zilvia :

[Quiche2192]

Originally Posted by burnsauto

OP: Small, to the point question without a lot of detail.

Zilvia :

Haha, love it! I think I'm going with the 2867R gen 2; the SR20DET drop in version. I'll be happy with 300HP. More important for me is the quick spool up. Thanks for all the info everyone!

[kouki_018]

So what did your numbers look like??