What turbo is the right size for you?

[Voltwings]

Ok, i've had a thought on my mind that im having a hard time finding some solid answers for and am hoping we can reach some sort of consensus here.

Basically a friend linked a turbo kit that a company made for the new dodge dart, a 1.4L motor rocking a 35R. Naturally my first thought was "lawl, peak spool at 5k." Well apparently, the clever people over at wherever it was fitted this 35R with a small AR so the turbo would actually spool. So i did a little investigating on the smaller displacement car forums (honda, VW...) and apparently this is not that uncommon. Take a Garrett 35R, precision 5557 / 6262 ... whatever and slap a small .48, .55, .63 AR on it to help with spool.

My thought here is basically you want the flow of a big turbo, but a set up that will spool sometime today. This perked my interest, because i know fitting a larger AR to a given turbo will increase top end performance, which raises the question: Which is "better" (more on that later)? A large 35R sized turbo with a small AR, or a small like 2871 with a 1.06 AR or something. Obviously i picked turbos at both ends of the spectrum so if that analogy is a bit off, please feel free to elaborate, this is all just hypothetical at this point.

Now as far as "better" is concerned, i guess it would all come down to power delivery and user preferance. If you have a small displacement engine you are probably revving really high with a big turbo, so spool really isnt your concern, just top end flow. However, why use a big ass turbo with a small AR at that point? i suppose its because a smaller turbo with a larger AR still wont flow over a certain point, and thats the reason we dont see 1.06 AR 2871's making 450+ whp or whatever. I'm semi rambling now so i suppose ill stop and let those smarter than i chime in. Hopefully this can help someone decide which turbo is going to be best for their application. Thanks.

[Tomas]

[Voltwings]

/thread.

[SarcasticOne]

The new 3576 looks really good IMO

Sent from my Galaxy Nexus using Tapatalk 2

[sidekick]

Originally Posted by Tomas

Do any companies actually make hotsides like this though? I've never seen a .48AR GT35 or a 1.06AR GT28. I know you were using those as hypothetical examples, but I think the real problem is that no one makes hotsides for applications like this. Bigger turbo = most people want a larger hotside. I also believe that if you go really big on one side and really small on the other, that the wheels will be mismatched and that could actually hurt performance. For example, if you match a very large compressor wheel with a small turbine, you end up with surge problems since both wheels will want to spin at different speeds.

I'm no turbo expert, so feel free to correct me, but that's just my 2 cents.

[Voltwings]

Originally Posted by sidekick Do any companies actually make hotsides like this though? I've never seen a .48AR GT35 or a 1.06AR GT28. I know you were using those as hypothetical examples, but I think the real problem is that no one makes hotsides for applications like this. Bigger turbo = most people want a larger hotside. I also believe that if you go really big on one side and really small on the other, that the wheels will be mismatched and that could actually hurt performance. For example, if you match a very large compressor wheel with a small turbine, you end up with surge problems since both wheels will want to spin at different speeds. I'm no turbo expert, so feel free to correct me, but that's just my 2 cents.

No I feel you're absolutely right, I may have exaggerated a bit too much. I have seen 30r kits for the neons with .48 AR, but not a 35r. And the largest I've seen for a 2871 is a .82, but I feel that still falls within lines of this question you know since those turbos are gery close in size anyways.

[silvapain]

My turbo is like my cock: small and ineffective.

[rfinkle2]

Choke is one thing (the bigger the turbo in most cases, the less chance of choke), surge is another.

Even without mating a small a/r to one of the larger turbos, the chance of surge is just too high for me to risk it.

FP HTA turbos are an exception. They specifically design their larger 30 series and 35 series to be much more resistant to surge, AND operate without damage or causing less damage than the standard Garretts in surge conditions.

[Mizzle]

God damn it people.

It's "piqued my interest," and "too high for me to risk it."

lazy fuckers. Carry on.
<3

[rfinkle2]

Originally Posted by Mizzle God damn it people. It's "piqued my interest," and "too high for me to risk it." lazy fuckers. Carry on. <3

Fixed. for my mizzle.

[Downmented]

Hopefully this can help you out or anyone else.

Big Turbo Spool characteristics


Also, when you go with a smaller A/R hotside you will sacrifice top end power but gain initial boost. So yes, putting a smaller hotside on will help spool sooner, but it does not pay off in the end.

[atvfreek]

Originally Posted by Voltwings Ok, i've had a thought on my mind that im having a hard time finding some solid answers for and am hoping we can reach some sort of consensus here. Basically a friend linked a turbo kit that a company made for the new dodge dart, a 1.4L motor rocking a 35R. Naturally my first thought was "lawl, peak spool at 5k." Well apparently, the clever people over at wherever it was fitted this 35R with a small AR so the turbo would actually spool. So i did a little investigating on the smaller displacement car forums (honda, VW...) and apparently this is not that uncommon. Take a Garrett 35R, precision 5557 / 6262 ... whatever and slap a small .48, .55, .63 AR on it to help with spool. My thought here is basically you want the flow of a big turbo, but a set up that will spool sometime today. This perked my interest, because i know fitting a larger AR to a given turbo will increase top end performance, which raises the question: Which is "better" (more on that later)? A large 35R sized turbo with a small AR, or a small like 2871 with a 1.06 AR or something. Obviously i picked turbos at both ends of the spectrum so if that analogy is a bit off, please feel free to elaborate, this is all just hypothetical at this point. Now as far as "better" is concerned, i guess it would all come down to power delivery and user preferance. If you have a small displacement engine you are probably revving really high with a big turbo, so spool really isnt your concern, just top end flow. However, why use a big ass turbo with a small AR at that point? i suppose its because a smaller turbo with a larger AR still wont flow over a certain point, and thats the reason we dont see 1.06 AR 2871's making 450+ whp or whatever. I'm semi rambling now so i suppose ill stop and let those smarter than i chime in. Hopefully this can help someone decide which turbo is going to be best for their application. Thanks.

It all comes down to power goals and what you want your throttle response to feel like. 99% of my driving is from 2500-5500 rpms so a smaller frame turbo fits perfect (2871-3076). Now if I am building a 1/4 mile car, I would want a 3582 and let her rip as every gear will be at the top of the rpms. A 35r will still spool pretty darn good (20+ by 4k) but again, user preference and driving is the major key.

[rfinkle2]

This is theoretical, but look @ how much air can be consumed by a 2.3 ltr engine @ spool.

Many of the turbos that are larger frame are way into the surge portion of the compressor map theoretically @ least.

@atvfreek; last minute I had CP-E switch my order to the gtx3071.

[Celestspeed3]

If you want to know what turbo is right for you use @BlueStreak; calculator. Then you can graph it on a compressor map and have an estimate on how it will perform. I know they have maps for the turbines but I'm not sure how those work or the relationship between the two. With the all the data that we have via ten billion data logs I don't see why we couldn't estimate the power band of any turbo and any hotside on a motor with stock cams. I know PNP heads flow more but unless all the porting was done by he same person in the same manner or by CNC it would be hard to compare them in my opinion.

[rfinkle2]

Originally Posted by Celestspeed3 If you want to know what turbo is right for you use @BlueStreak; calculator. Then you can graph it on a compressor map and have an estimate on how it will perform. I know they have maps for the turbines but I'm not sure how those work or the relationship between the two. With the all the data that we have via ten billion data logs I don't see why we couldn't estimate the power band of any turbo and any hotside on a motor with stock cams. I know PNP heads flow more but unless all the porting was done by he same person in the same manner or by CNC it would be hard to compare them in my opinion.

Bluestreak's calculator here:

http://www.mazdaspeedforum.org/forum/foru...5/#post1354795

[atvfreek]

Originally Posted by rfinkle2 This is theoretical, but look @ how much air can be consumed by a 2.3 ltr engine @ spool. Many of the turbos that are larger frame are way into the surge portion of the compressor map theoretically @ least. @atvfreek; last minute I had CP-E switch my order to the gtx3071.

You will be more than happy with your power goals on the gtx3071. IMO there is no reason to go larger than that unless you a) have plenty of fuel, and b) you want more than 430-450 hp.

[rfinkle2]

Originally Posted by atvfreek You will be more than happy with your power goals on the gtx3071. IMO there is no reason to go larger than that unless you a) have plenty of fuel, and b) you want more than 430-450 hp.

I was feeling peer pressure to use the 3076. LOL. But I secretly e-mailed CP-E and asked them to switch. Sshhhhh!.

[silvapain]

Originally Posted by rfinkle2 I was feeling peer pressure to use the 3076. LOL. But I secretly e-mailed CP-E and asked them to switch. Sshhhhh!.

I'm glad you did. I think you'll like the responsiveness and earlier spool of the GTX3071 a lot better.

[Celestspeed3]

Originally Posted by atvfreek You will be more than happy with your power goals on the gtx3071. IMO there is no reason to go larger than that unless you a) have plenty of fuel, and b) you want more than 430-450 hp.

That interesting you mention that. With the GTX3076 on @Fobio; car it seems like anything more than that is only really usefull in higher gears (5 and 6). I have the same setup for my other engine and without extra fuel you really can't "use" the turbo to its fullest. @magesticbluento; has the same setup except he will have a GTX2867, it will be very interesting to see and compare the power curve once I install everything for him. I was debating trying a GTX3582 but I have a feeling it wouldn't do much good on the MS3 chassis for road race, the powerband might make the car impossible to drive with so much torque at the high end. Things seem to be moving slowly on the port injection front and that's really what I want to start playing with.

[helmetface]

Always trying to reinvent the [compressor] wheel huh @Voltwings; ?

IMO- 30r's and 35's with properly mated hotsides will still spool just fine. Look through the big turbo characteristics thread. Those with a proper setup are seeing amazing spool times. I am on the side that prefers a slightly smaller hotside, I like(read: LOVE) response! And I will sacrifice a little top end for it. However, the GT3071's mated with a ~.60 gives it plenty of room to breathe and is still small enough to get that bitch heated.


Unless you're dealing with VGA turbos or certain twinscroll setups you can rarely increase spool AND top end with hardware alone.


*edit* Fuel is more of an issue than anything here, people love the idea of these bigger turbos but really without fuel the BNR3 is perfect. Having a GT30+ with no extra fueling is like a slower spooling BNR3 with a little more top end.

[Voltwings]

Originally Posted by helmetface Always trying to reinvent the [compressor] wheel huh @Voltwings; ? IMO- 30r's and 35's with properly mated hotsides will still spool just fine. Look through the big turbo characteristics thread. Those with a proper setup are seeing amazing spool times. I am on the side that prefers a slightly smaller hotside, I like(read: LOVE) response! And I will sacrifice a little top end for it. However, the GT3071's mated with a ~.60 gives it plenty of room to breathe and is still small enough to get that bitch heated. Unless you're dealing with VGA turbos or certain twinscroll setups you can rarely increase spool AND top end with hardware alone. *edit* Fuel is more of an issue than anything here, people love the idea of these bigger turbos but really without fuel the BNR3 is perfect. Having a GT30+ with no extra fueling is like a slower spooling BNR3 with a little more top end.

Haha this question was partially based off a lot of the information that came up in that BNR alternative thread. Basically I know how turbo's work, as I'm sure most of us do, but what many people (including myself) don't know is WHY they work, so to speak. Hence the various hotside discussions haha, being that our drop in options are limited, and hell even aftermarket options with lack of manifolds, all of us basically end up running the same damn turbos so our scope is kind of limited.

[Celestspeed3]

Originally Posted by Voltwings Haha this question was partially based off a lot of the information that came up in that BNR alternative thread. Basically I know how turbo's work, as I'm sure most of us do, but what many people (including myself) don't know is WHY they work, so to speak. Hence the various hotside discussions haha, being that our drop in options are limited, and hell even aftermarket options with lack of manifolds, all of us basically end up running the same damn turbos so our scope is kind of limited.

With the CPE Tial setup you can run just about any combination you want. So this now opens up the discussion to a lot more people than before. Granted there is only the one manifold.

It's too bad full race doesn't make a twin scroll T4 manifold. If you wanted to sacrifice your AC uou could move the alternator to the front of the motor and have enough room for one of the larger EFR turbos. I'd be willing to try his out. My fiance hates AC and she has no problem with me removing it.

[Downmented]

Originally Posted by Voltwings Hence the various hotside discussions haha, being that our drop in options are limited, and hell even aftermarket options with lack of manifolds, all of us basically end up running the same damn turbos so our scope is kind of limited.

Another reason im glad i went top mount, i have allot more options as to what im able to run now that im not limited to the stock flange, i personally couldnt imagine doing a t3/t4 on stock location, but thats just me. That CPE manifold with the V-Band option should seriously be a consideration to ANYONE (with a ms3 of course) considering going BT.

Then theres the fuel issue, but this isnt about fuel now is it

[rfinkle2]

I had to give up on trying to be different. For the price, the atmosphere kit really can't be beat.

I started to piece a bunch of parts together, but in the end, was wasting time and money, only to arrive @ having to spend more time and money to have everything custom made.

That may be OK for people who have days off during the week, but like said in other thread, "I ain't got time for that". LOL

[Lex]

You will never find a concrete answer since the turbo size is application dependent as well as preference dependent.

When building the car and choosing a turbo it is good to be informed about the choices and the pros and cons.

I don't see many people upgrading a street car needing more than a BNRS3 or GT(X)3071 from the current offerings.

[Celestspeed3]

Originally Posted by Lex You will never find a concrete answer since the turbo size is application dependent as well as preference dependent. When building the car and choosing a turbo it is good to be informed about the choices and the pros and cons. I don't see many people upgrading a street car needing more than a BNRS3 or GT(X)3071 from the current offerings.

That's been something I've been going over in head constantly. For time attack is it better to use a larger turbo (gtx3582 0.82 hotside), a gtx3076 1.03 hotside, or a gtx2867 hotside. I think I may surge the smaller turbo even with a big hotside. But it all depends on the powerband and whether or not the car can put the power down. Lets be honest a dyno queen is impressive but spinning tires even at the track is slow and embarassing.

[Voltwings]

Originally Posted by Lex You will never find a concrete answer since the turbo size is application dependent as well as preference dependent. When building the car and choosing a turbo it is good to be informed about the choices and the pros and cons. I don't see many people upgrading a street car needing more than a BNRS3 or GT(X)3071 from the current offerings.

i suppose you're right, and to narrow the scope of the question to two similarly sized turbos might make more sense. 2871 v 3071.

In terms of spool nearly identical, but lets assume the 2871 had a .82 hotside and the 3071 had a .55 (for the sake of argument).

1. is it unreasonable that the 3071 would outspool the 2871 in this case?
2. Would choking up the hotside of the 3071 effect performance enough that the 2871 would actually make more power?
3. Seeing as how the 2871 is small enough to spool well enough on its own, would the large hotside give it enough top end to match the 3071 (or at least get close), or is the compressor simply done once you reach the max it can flow?

I understand that i am speaking in a great deal of generalities, but i imagine there have to be some sort of "do's" and "dont's" associated with this you know?

[sidekick]

^ I want to hear what people have to say about that. Does anyone have any good links ( @rfinkle2; lol) about choosing hotsides/turbos in general? I hear Corky Bell's book is pretty good, but isn't it more geared towards the basics?

[Downmented]

Originally Posted by Voltwings 1. is it unreasonable that the 3071 would outspool the 2871 in this case? 2. Would choking up the hotside of the 3071 effect performance enough that the 2871 would actually make more power? 3. Seeing as how the 2871 is small enough to spool well enough on its own, would the large hotside give it enough top end to match the 3071 (or at least get close), or is the compressor simply done once you reach the max it can flow?

You have to take the actual flow capabilities that the smaller turbo is capable of, because even with the 28r having a larger hotside and the 30r having a smaller hotside, the 28r just cant flow enough to out perform the 30r.

[rfinkle2]

Originally Posted by sidekick ^ I want to hear what people have to say about that. Does anyone have any good links ( @rfinkle2; lol) about choosing hotsides/turbos in general? I hear Corky Bell's book is pretty good, but isn't it more geared towards the basics?

Bluestreak's calculator (link above) is based on Garrett's formulas which are based on engine size, brake specific fuel consumption, and include pressure drop and some more detailed calculations while accounting for HP goals.

The automated version of bluestreak's calculator:
Garrett Boost Adviser | Turbobygarrett

A quick and dirty on matching HP / engine size and compressor:
http://www.lovehorsepower.com/joomla...id=4&Itemid=88

[sidekick]

So now that we have the above info, does anyone have a compressor map for the BNRS3? Or does no such thing exist?

[rfinkle2]

Originally Posted by sidekick So now that we have the above info, does anyone have a compressor map for the BNRS3? Or does no such thing exist?

Compressor map courtesy of cld12pk2go.

Bnr is as close to this trim version of the 2871 as can be found:

[atvfreek]

Originally Posted by rfinkle2 Compressor map courtesy of cld12pk2go. Bnr is as close to this trim version of the 2871 as can be found:

That is what I've been using as well. And it mostly certainly flows 45-50lbs/min

Sent from your couch

[TiGraySpeed6]

To me, this conversation, tho excellent as an exercise and topic of conversation in and of itself, is more directly related to the platform capabilities first.

Frankly I was amazed to hit the fuel limit wall on the BNR with my decidedly not optimum intake and exhaust configuration. Add to that the inherent limits of the stock bottom end and, to me, this conversation very quickly becomes one of price- simple bolt on $1200ish or go for it with engine build, custom intake and exhaust and supplemental fueling.


Oh, and thanks for the links finkle!

[Voltwings]

Yeah, its hard to speak broadly enough to cover the topic, but specific enough to make it relevent. Basically, fuel aside, engine internals aside, as far as strictly making X power over X power band, the fastest way of getting from point A to point B, which turbo application is "better?" Small turbo with large AR, or big turbo with small AR. I'd hate for this to be the end of the thread, but the consensus seems to be that even with the larger AR a small turbo cant flow enough to match a larger turbo.

[rfinkle2]

You need about 25-26 psi and high octane fuel for 400 hp. (as if you didn't know, just for thread purposes).

@26 psi you need to flow > 50 lbs / min. (which the BNR has the capability to do, albeit probably maxing the turbo pretty much @atvfreek; @TiGraySpeed6;?).

[TiGraySpeed6]

I maxed around 45 lbs/min, but again that was stock MAF dia
(+/- 345 g/s)

g/s to lbs/min (might be other way around, but can enter either unit to get the other)
Convert pound/minute [lb/min] <?> gram/second [g/s] ? Hydraulics ? Fluids ? Mass Flow Rate ? Compact Calculator

[sidekick]

Originally Posted by rfinkle2 You need about 25-26 psi and high octane fuel for 400 hp. (as if you didn't know, just for thread purposes). @26 psi you need to flow > 50 lbs / min. (which the BNR has the capability to do, albeit probably maxing the turbo pretty much @atvfreek; @TiGraySpeed6;?).

I plotted a few different pressure ratios on that GT2871 compressor map for the BNR and it was running out of breath by 21 PSI according to the compressor map. I know that's just theoretical, but what's up with that? It was landing off the map at 21PSI @ 7K. Aren't a lot of people running quite a bit more boost than that at redline with the BNR? Maybe I'm not looking at it quite right.

[rfinkle2]

Originally Posted by sidekick I plotted a few different pressure ratios on that GT2871 compressor map for the BNR and it was running out of breath by 21 PSI according to the compressor map. I know that's just theoretical, but what's up with that? It was landing off the map at 21PSI @ 7K. Aren't a lot of people running quite a bit more boost than that at redline with the BNR? Maybe I'm not looking at it quite right.

The compressor maps we are looking @ are all standardized to an atmospheric temp that noone in msf is experiencing running the BNR (at the moment IIRC).

Lower ambient temps shift the entire map to the right.

A combo of methanol injection and e85 will shift the compressor map right a touch (by a margin I don't think is quantifiable), in combo with the compressor map not being 100% accurate, but it is the best we got tbh.

Point being, the max speed line on the compressor map accepted as closest shows the BNR to be good for ~45 lbs min. in SAE corrected ambient temps (which I believe are in the high 70's (f). )

Add an upgraded compressor housing and BNR's secret sauce and a little fudging is necessary.

[sidekick]

Originally Posted by rfinkle2 The compressor maps we are looking @ are all standardized to an atmospheric temp that noone in msf is experiencing running the BNR (at the moment IIRC). Lower ambient temps shift the entire map to the right. A combo of methanol injection and e85 will shift the compressor map right a touch (by a margin I don't think is quantifiable), in combo with the compressor map not being 100% accurate, but it is the best we got tbh. Point being, the max speed line on the compressor map accepted as closest shows the BNR to be good for ~45 lbs min. in SAE corrected ambient temps (which I believe are in the high 70's (f). ) Add an upgraded compressor housing and BNR's secret sauce and a little fudging is necessary.

I see, so essentially, it is just the sum of a few discrepancies throwing everything off? I figured it had something to do with the maps themselves. Oh well, it still gives a pretty good idea of which turbo will suit your goals the best.