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Right Turbo For "Not a Miata"

 
Old 12-26-2017, 06:20 PM
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Default Right Turbo For "Not a Miata"

Been watching this forum because I'm still a massive fan of the Miata.
I almost bought one with the intent of k swapping it etc, only to realize that I couldn't bring myself to pour 2x-3x the amount of money into mods compared to the cost of the car.
But I was also under the impression that most turbo BP motors were putting out 200-250whp. Looks like the flood gates have opened with the EFR turbos, pushing miata's to 300+ whp while keeping an AutoX friendly power band.

I ended up buying an Elise, and I've been mulling over how to make more power, so after looking at several miata EFR dyno graphs I think this turbo might work equally as well on the 2ZZ.
The 2ZZ acts a bit like a B18 honda motor. Makes HP but not much torque, so the 6258 was my first choice (especially as I'm looking for about 400wh on E85, and anything over 300whp on pump is probably fine) But I worry about it breathing well at 8500 rpm.
I'm going to be making the manifold out of sch 10 pipe so I have a bit of flexibility.
So what say you guys?

6258 in theory could hit the numbers but probably with substantial heat
6258 twin scroll manifold would be more likely to hit it and less likely to choke up high
6758 (same as above) maybe slightly slower spool
6758 twin scroll (prob still slower spool despite the twin scroll but probably the ability to approach 500whp on E85

Right now I have a TVS supercharger on the car making about 300whp and it's ok, but it's not nearly enough. Worried about turbo lag. I deff think turbo lag would ruin the charachter of the car, same as it would with a miata.

Thanks guys
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Old 12-26-2017, 07:18 PM
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6258 is all you need. I wouldn't go any bigger than that considering the displacement.
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Old 12-26-2017, 08:29 PM
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6258 an 6758 share everything but a compressor housing (I think???)so go with that. If you find it doesn't fulfill your grandest dreams, grab the bigger housing.
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Old 12-26-2017, 08:40 PM
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Originally Posted by bjorno View Post
6258 an 6758 share everything but a compressor housing (I think???)so go with that. If you find it doesn't fulfill your grandest dreams, grab the bigger housing.
Compressor wheel on the 6258 is 62mm vs 6758 which is 67mm
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Old 12-26-2017, 08:42 PM
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Originally Posted by Goingnowherefast View Post
6258 is all you need. I wouldn't go any bigger than that considering the displacement.
the .64 might choke the motor at high rpm though. How about the twin scroll option?
I haven't seen anyone use the twin scroll 6258, or the 6758 for that matter
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Old 12-26-2017, 11:21 PM
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twin scroll housing of the same size would choke even more. so I'm not sure where you're going with that one
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Old 12-27-2017, 02:36 AM
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I think there's half a dozen 0.64a/r 6258/6758 setups north of 400whp now, so by all means, keep perpetuating the myth that the 0.64a/r EFR B1 turbine housing is too restrictive to make decent power
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 12-27-2017, 07:55 AM
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Greg from thecarpassion channel just made 415hp on a 6258 with the vband 0.8 housing at 20 psi and e85.

look into this option. Bigger housing and vband. And still good response.
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Old 12-27-2017, 08:40 AM
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Originally Posted by Savington View Post
I think there's half a dozen 0.64a/r 6258/6758 setups north of 400whp now, so by all means, keep perpetuating the myth that the 0.64a/r EFR B1 turbine housing is too restrictive to make decent power
Just genuinely asking the question. I figure it might be more of a restriction due to the higher RPM.
After reading Soviet's threads I know the 6758 will do it and probably more, but it's the 6258 that I was concerned with, thats why I was thinking a 6258 with the vband or twin scroll setup like mentioned with the higher .80 AR.

So which would spool quicker do you think a 6258 Vband .80 or a 6758 .64 T25?
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Old 12-27-2017, 08:51 AM
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It won't be a "restriction" but it might not also carry power as well as it does on a BP, mostly because the BP is outdated trash and a 2zz isn't.

If the goal was 300-350whp, i'd say 6258. At 400whp, i'd go 6758.
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Old 12-27-2017, 10:02 AM
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Originally Posted by concealer404 View Post
It won't be a "restriction" but it might not also carry power as well as it does on a BP, mostly because the BP is outdated trash and a 2zz isn't.

If the goal was 300-350whp, i'd say 6258. At 400whp, i'd go 6758.
Lol the 2zz is pretty trash too but it does rev higher.. but many would rightly prefer the old B18 honda motors to them.
Thats why when I saw you guys making really good numbers with spool to match on the BP motors, I got hopeful.

Ari's car is a good example of a setup that would be perfect, makes 375whp on a mustang dyno on pump, and I'm sure could be pushed to 400+ on E85

Thats already pushing the limits of the transmission on these cars (after replacing 3rd and 4th)
But I see a lot of Miata's falling in that 300-350 range with the 6258 and remember I already make around 300whp so I don't want to go through the trouble, just to end up where I already am. Thats why I'm asking questions on this forum.

It seems this forum is the only one with experience with the smaller EFR turbos. All other forums are talking about the larger frame EFR turbos.
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Old 12-27-2017, 10:13 AM
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There are more than a few guys with 400+hp running the 6 speed. If you are concerned about the trans you can always put a bmw trans in there with a getreg diff but then again you are in 5k to do that. You should be fine with a 6 speed and 350hp even 400 if you arnt super abusive to it.


If the goal was 300-350whp, i'd say 6258. At 400whp, i'd go 6758.
and this I 100% agree with

Last edited by matrussell122; 12-27-2017 at 01:50 PM.
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Old 12-27-2017, 11:10 AM
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I wouldn't say the 2zz is trash. It is if you expect it to make #TEXASwhp unopened. But the head flows extremely well, and the general design of it is from an entirely different universe from the BP, and it shows.
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Old 12-27-2017, 01:35 PM
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Originally Posted by borka View Post
Greg from thecarpassion channel just made 415hp on a 6258 with the vband 0.8 housing at 20 psi and e85.

look into this option. Bigger housing and vband. And still good response.
Nope, Greg is on the small 0.64 housing
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Old 12-27-2017, 01:37 PM
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Mat was saying the BP is trash and the 2ZZ is a great motor. I loved the 2ZZ in my friend's Celica. One of the valves tried to occupy the same space as the spark plug at 198,200mi though....
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Old 12-27-2017, 01:53 PM
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Originally Posted by x_25 View Post
Mat was saying the BP is trash and the 2ZZ is a great motor. I loved the 2ZZ in my friend's Celica. One of the valves tried to occupy the same space as the spark plug at 198,200mi though....
Thats not what i was saying that was "concealer404" I have no personal experiance with 2jz motors. But I do know the bp has bad harmonics and flow properties that make reving to 8500rpm really hard on equipment especially for long periods of time.
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Old 12-27-2017, 02:17 PM
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Originally Posted by Ls1Rx7 View Post
Just genuinely asking the question. I figure it might be more of a restriction due to the higher RPM.
Higher RPM won't cause a restriction in and of itself, though. Increased airflow will, but the increased engine speed in and of itself won't do anything. If you have two engines making the same power, one spinning at 6k and one spinning at 8k, the airflow into the turbine is the same because the power is the same. It's hard to separate mentally because increased RPM almost always means increased power, but the power/airflow increase is what makes the difference. You don't need to increase RPM to increase power - you could add displacement at the same RPM and you would need to go larger on the a/r to reduce the restriction, for instance.

Since we are talking about a defined power figure (400whp), that defines our airflow requirement, and we don't have to worry about RPM.

With turbine A/R you are playing with backpressure and flow. Small A/R builds backpressure early (read: spools early) and maintains that pressure as power and flow increase. Large A/R is lazy on the bottom but allows for more turbine flow on top, which promotes flow through the entire engine. If you are worried about spool, you generally want to stay small. Sometimes that's not true, and the factors at play in making that decision are really, really hard to model (like, only OEMs do it).

After reading Soviet's threads I know the 6758 will do it and probably more, but it's the 6258 that I was concerned with, thats why I was thinking a 6258 with the vband or twin scroll setup like mentioned with the higher .80 AR.

So which would spool quicker do you think a 6258 Vband .80 or a 6758 .64 T25?
Depends on how you define spool. I think the .80a/r is going to respond worse, since that larger turbine will take more time to pressurize, and that extra time will be directly felt by you in the driver's seat every time you open the throttle. Most people define spool in that way.

The only factors decreasing the response on the 0.64a/r 6758 would be the increased compressor wheel inertia and the slight decrease in low-speed efficiency of the turbine wheel, but having driven both (6258 and 6758 in 0.64a/r flavor) the difference is small.

Twin-scroll only helps at low RPM where the exhaust pulses are separated. At high RPM they blend together. A small-A/R twinscroll housing would outperform its single-scroll sibling at low RPM and perform virtually identically at high RPM, but small A/R housings don't need help down low. Large A/R housings, on the other hand, need help, so that's where twin-scroll housings focus. Add twin-scroll to a large a/r and the low-end performance increases, but the twinscroll pairing doesn't do anything to address the increased turbine housing volume. That increase in volume is going to hurt response across the powerband.

In general, large A/R setups do well on larger engines. Larger engines can produce the airflow to spool up earlier, and the response loss is reduced because the increased volume is filled faster by the larger engine. Larger engines also run less boost to make the same power, so you want/need less backpressure to power the compressor and promote flow in boost.

Your entire mantra is about spool. You are coming from a PD blower and you're concerned about response loss. I think you would be foolish to upsize the A/R off the bat. If you want an EFR, do the 0.64a/r 6258 and add boost. If it's a street/autocross car, you will never be in power long enough to cause heatsoak issues. For a track car, I would do the 6758 to gain the compressor efficiency at 400+whp and deal with the small response/linearity loss on the street.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".

Last edited by Savington; 12-27-2017 at 02:33 PM.
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Old 12-27-2017, 02:17 PM
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The 2ZZ is a great motor.
Why are you only making ~300HP with a TVS...are you stock block?
Don't get me wrong I'm all for the EFRs but your already half way there on the TVS?
Are you on the NY tri-state? Would recommend seeing Waldir over at Intermecanica to show you some things / tell you some things that likely few on the forum know about the Elises.

post some more specs....
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Old 12-27-2017, 03:42 PM
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Originally Posted by Savington View Post
Higher RPM won't cause a restriction in and of itself, though. Increased airflow will, but the increased engine speed in and of itself won't do anything. If you have two engines making the same power, one spinning at 6k and one spinning at 8k, the airflow into the turbine is the same because the power is the same. It's hard to separate mentally because increased RPM almost always means increased power, but the power/airflow increase is what makes the difference. You don't need to increase RPM to increase power - you could add displacement at the same RPM and you would need to go larger on the a/r to reduce the restriction, for instance.

Since we are talking about a defined power figure (400whp), that defines our airflow requirement, and we don't have to worry about RPM.

With turbine A/R you are playing with backpressure and flow. Small A/R builds backpressure early (read: spools early) and maintains that pressure as power and flow increase. Large A/R is lazy on the bottom but allows for more turbine flow on top, which promotes flow through the entire engine. If you are worried about spool, you generally want to stay small. Sometimes that's not true, and the factors at play in making that decision are really, really hard to model (like, only OEMs do it).



Depends on how you define spool. I think the .80a/r is going to respond worse, since that larger turbine will take more time to pressurize, and that extra time will be directly felt by you in the driver's seat every time you open the throttle. Most people define spool in that way.

The only factors decreasing the response on the 0.64a/r 6758 would be the increased compressor wheel inertia and the slight decrease in low-speed efficiency of the turbine wheel, but having driven both (6258 and 6758 in 0.64a/r flavor) the difference is small.

Twin-scroll only helps at low RPM where the exhaust pulses are separated. At high RPM they blend together. A small-A/R twinscroll housing would outperform its single-scroll sibling at low RPM and perform virtually identically at high RPM, but small A/R housings don't need help down low. Large A/R housings, on the other hand, need help, so that's where twin-scroll housings focus. Add twin-scroll to a large a/r and the low-end performance increases, but the twinscroll pairing doesn't do anything to address the increased turbine housing volume. That increase in volume is going to hurt response across the powerband.

In general, large A/R setups do well on larger engines. Larger engines can produce the airflow to spool up earlier, and the response loss is reduced because the increased volume is filled faster by the larger engine. Larger engines also run less boost to make the same power, so you want/need less backpressure to power the compressor and promote flow in boost.

Your entire mantra is about spool. You are coming from a PD blower and you're concerned about response loss. I think you would be foolish to upsize the A/R off the bat. If you want an EFR, do the 0.64a/r 6258 and add boost. If it's a street/autocross car, you will never be in power long enough to cause heatsoak issues. For a track car, I would do the 6758 to gain the compressor efficiency at 400+whp and deal with the small response/linearity loss on the street.
Thank you thank you thank you. More of the detail I needed, So the larger AR especially on the T4 manifold you think will negate the benefits of the Twin scroll option, might as well just keep it simple and stick with the .64 regardless of which I went with, correct?

Originally Posted by Zsanz View Post
The 2ZZ is a great motor.
Why are you only making ~300HP with a TVS...are you stock block?
Don't get me wrong I'm all for the EFRs but your already half way there on the TVS?
Are you on the NY tri-state? Would recommend seeing Waldir over at Intermecanica to show you some things / tell you some things that likely few on the forum know about the Elises.

post some more specs....
Yes, car is on the stock motor with a TVS1320 and a small A2W setup, and I'm based in the Boston area so tri-state isn't far.
I've tried exploring the TVS route but the company that sells the kits (BOE) and their owners don't seem to want to work with me. They do remote tuning, and they won't tune for methanol and they keep reiterating that short of spending 25-30k (lol) I just can't get where I want to go. They are the only ones who can flash the factory PCM so I need them come emissions time. But otherwise I'm basically trying to get as far away from them as possible.
Now if I go standalone, which I'll need to do anyway, then I can get it tuned elsewhere, still swapping pullies is a big difference than just turning up a boost controller. and the pully isn't very accessible in this car, but yes you're right all I would need to turn up the wick is a large front mount heat exchanger.
Bottom end would need to be built either way, and stand alone would be needed either way. So thats a wash.

They wouldn't explain why, but the current vendor is saying I'd only get to about 325whp with lower compression bottom end on pump, mostly claiming that the TVS being essentially a giant fan becomes less efficient at higher pressures. I can understand this but the honda guys are still getting 400whp out of them on E85. it would be easier to keep this setup in the car, but seems difficult to make power with more boost, going this route.
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Old 12-27-2017, 03:54 PM
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Originally Posted by Ls1Rx7 View Post
Thank you thank you thank you. More of the detail I needed, So the larger AR especially on the T4 manifold you think will negate the benefits of the Twin scroll option, might as well just keep it simple and stick with the .64 regardless of which I went with, correct?
Yes, that would be my guess.

Remember that the entire system matters when it comes to response. The big swoopy equal-length header does you no favors when it comes time to pressurize it on throttle application. Everything that promotes flow (equal length long-tube headers, big A/R turbine, big turbos) hurts response. One of the big reasons the EFRs are so successful on the Miata platform is because Miata guys generally build towards responsive setups with small + unequal manifolds, small turbos, etc. The EFR just happens to have some trick materials and a bitchin' compressor wheel which allows it to respond like a small turbo and make power like a big turbo.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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