1999 automatic came with a 4.1. All NB autos did. Might want to count those turns :)
I did, but I'll check my work. Thanks! 
1999 automatic came with a 4.1. All NB autos did. Might want to count those turns :)
I did, but I'll check my work. Thanks!
In reply to Keith Tanner :
A 1.6 4.3 w/ a 6 speed might be pretty fun, you'd be shifting a lot, but it might make up for a bit for the lack of power.
Keith Tanner said:I assume "accomplished racers" means Emilio for a pure dedicated track car on specific tracks, and then his advice gets repeated. If your car has license plates instead of number plates, it's goofy short. I do have a friend who lives in Germany who loves it, but it's behind a stock 1.6.
Yeah, it can work in a dedicated race car because the only time you use 1st is loading it onto the trailer and you don't care about highway cruising at reasonable RPM. With the 6+4.3 you just wind up using gears 3/4/5/6 instead of 2/3/4/5. Sucks on a street car.
An MSM with a 5-speed sounds fine, they can only dream of making enough power to break the transmission. :)
Dang, hearing all the negativity about shifting feel and gearing of the 6 speed has me rethinking my plan. I always thought the 6 speed would be more desirable, but it looks like in the case of the Miata the 5 speed is a better tranny when it comes to driving experience. The last thing I want is the enjoyment of driving it to go away due to the transmission.
And yeah, I'd like to stick with the Miata than buy another car. Im a bit of a Miata junkie and would rather have that than a Corvette, Mustang, etc. I like the driving dynamics of the Miata far better. Plus, its just more fun to pull on a muscle car in a Miata. 
As noted, it's not that the 6 speed is a bad trans. It's just that the 5 speed is very, very good. Keep the 6 speed in good shape (shifter rebuild kits are available from - cough - your favorite aftermarket suppliers) and it'll be fine.
Why do you want a 300 hp Miata? What turbocharger is on the car now?
Keith Tanner said:As noted, it's not that the 6 speed is a bad trans. It's just that the 5 speed is very, very good. Keep the 6 speed in good shape (shifter rebuild kits are available from - cough - your favorite aftermarket suppliers) and it'll be fine.
Why do you want a 300 hp Miata? What turbocharger is on the car now?
Makes sense, speaking of which, I need to rebuild the shifter in my NA.
I mainly want a 300whp Miata because I've always wanted to see what that much power really feels like in such a light chassis. I chose 300whp because it seems like a high HP number (to me) for a Miata, but I honestly would be fine dropping that number down to something like 270whp if it helps preserve things a bit longer. Probably the main reason is because I also have a NA that I plan on dropping a 1.8 into and turbo'ing but want to keep that at a sub 250whp number, so I want the NB to be something a bit different from that. I enjoy my 230whp right now though, its definitely not a slow car.
The turbo on the car now isn't anything special, its a cheap chinese TO4E T3/T4 turbo, so I'd definitely look into upgrading that to a better turbo as well.
Yeah, when someone comes to us with a specific power number like that it's usually determined by "I want 50 hp more than normal" :) I would strongly suggest not getting caught up in the peak dyno power number because that is almost always a recipe for disappointment when you don't quite get there and you get all frantic.
I was mostly interested in the size of the turbo. A T3/T4 has lots of power potential but you're leaving a lot of response on the table given your power number. It's a big, antique design. Running something like a 2560 at your current peak power number might be considerably quicker than what you have now and would not require anywhere near the same level of investment.
Keith Tanner said:Yeah, when someone comes to us with a specific power number like that it's usually determined by "I want 50 hp more than normal" :) I would strongly suggest not getting caught up in the peak dyno power number because that is almost always a recipe for disappointment when you don't quite get there and you get all frantic.
I was mostly interested in the size of the turbo. A T3/T4 has lots of power potential but you're leaving a lot of response on the table given your power number. Running something like a 2560 at your current peak power number might be considerably quicker than what you have now and would not require anywhere near the same level of investment.
You might be onto something here, thanks Keith! I will admit, I am a total turbo newbie, so just threw on the turbo that came with my kit and didn't think about it again after that. The NB is my first turbo car. So a 2560 turbo I'm guessing would drop the area needed for boost to build, which would in turn make the car quicker to accelerate in its current form? Hopefully that makes sense. I definitely would love to have the car accelerate faster than it does now.
Yes, you'll get boost sooner - both earlier in the RPM range and more quickly after you open the throttle - with a more appropriately sized turbo. It's quite possible there are other aspects of the kit that could be addressed as well. Speed (especially on the street) is all about area under the curve - the maximum amount of power/torque available over the widest RPM range.
Keith Tanner said:Yes, you'll get boost sooner - both earlier in the RPM range and more quickly after you open the throttle - with a more appropriately sized turbo. It's quite possible there are other aspects of the kit that could be addressed as well. Speed (especially on the street) is all about area under the curve - the maximum amount of power/torque available over the widest RPM range.
Interesting, sounds like if I downsize my current turbo, I may well be satisfied with what I have. The current chinese turbo on my car is oil cooled only, and it looks like the GT2560R is water cooled as well, so thats something I will need to look into too. Is there a good resource for learning what different turbo sizes are? For example, I had no idea the 2560 is a smaller turbo than a T3/T4. It would be great to get to learn what size different turbo offerings are and what their pros/cons are.
Garrett changed their nomenclature a long time ago, and T3/T4 is the old way. The 2560 was called a T28 back then, and a 2554 was a T25. The new way is a lot more logical as it actually contains more information :) There are a couple of different variations of T3/T4 and you'll need to know what you have - specifically the turbine housing. Generally, the T3/T4 is what we would have used for a 300+ hp engine 20 years ago. Today, we'd probably use a GT3071R.
Turbo sizing is a deep pool. Luckily, you're dealing with a common, well-understood car so you don't need to reinvent the wheel when it comes to picking the right size for your application. For a given power level (say, "whatever I can do on a healthy stock engine"), there are one or two known good options.
Keith Tanner said:Garrett changed their nomenclature a long time ago, and T3/T4 is the old way. The 2560 was called a T28 back then, and a 2554 was a T25. The new way is a lot more logical as it actually contains more information :) There are a couple of different variations of T3/T4 and you'll need to know what you have - specifically the turbine housing. Generally, the T3/T4 is what we would have used for a 300+ hp engine 20 years ago. Today, we'd probably use a GT3071R.
Turbo sizing is a deep pool. Luckily, you're dealing with a common, well-understood car so you don't need to reinvent the wheel when it comes to picking the right size for your application. For a given power level (say, "whatever I can do on a healthy stock engine"), there are one or two known good options.
Awesome, thank you! I will go out to my turbo now and take a look at the specs written on the turbo (or look up my order), and see what I have. I'll let you know what I find. I had no idea Garrett changed their nomenclature, seems like I really am using an antiquated turbo. Maybe not the best option for my application either, as you mentioned.
I'll attach an image of my dyno run from this past summer when I went to get the car tuned. At the time, I didn't think much of it but now when I look at it, it seems like a smaller turbo may benefit me. You think a GT2560R could change things for the better? I'll get more of my turbo specs for you once I find the info. I appreciate the help so far, definitely learning new things!
EDIT: Forgot to mention, the setup has a full 3 inch exhaust as well.
Japanspec said:Awesome, thank you! I will go out to my turbo now and take a look at the specs written on the turbo (or look up my order), and see what I have. I'll let you know what I find. I had no idea Garrett changed their nomenclature, seems like I really am using an antiquated turbo. Maybe not the best option for my application either, as you mentioned.
They didn't just change the nomenclature, there are are at least 4 different generations of Garrett turbos out there:
- old T25/T28/T3/T4 have a sleeve bearing
- "GTxxxx" have a ball bearing
- "GTXxxxx" are like the GT, but add a newer design of compressor wheel that makes them much more efficient at higher boost ratios. For example, the GT2860RS ("disco potato") tops out at about 270-300 rwhp, but the GTX2860R (of which there are two sub versions) is a drop-in replacement that will do 350-380 rwhp by allowing you to run more boost without just turning it into heat. Same turbine, same exhaust housing geometry, so it bolts up to the manifold & downpipe.
- the new "G series" about which I know almost nothing.
A GT2560 is really well-suited to a Miata that isn't too far from stock. It tops out around 250 rwhp, which matches the limits on the stock rods, fuel pump, and 5-speed pretty well. You can run it on a stock motor for a long time.
For a built motor that's using a 6-speed I like the GTX2860R or GTX2863R, because they top out around the level where you can keep the 6-speed alive by exercising "mechanical empathy".
3071s will do more, but you're giving up spool and joining the transmission of the month club (or doing the BMW swap, about which I don't know a lot, but which doesn't appear to be cheap).
As far as how to compare different configurations of turbos, google "how to read a compressor map" and then hit Garrett's site and start looking at them (might be tricky to find old ones). The chinese ebay knockoff turbo that you have now is likely to be inferior than just about anything that's an actual Garrett. :)
There used to be T25 and T28 ball bearing turbos before the name change came in. The difference between our old T28 "big ball bearing" turbo and the GT2560R is nomenclature only.
In reply to codrus (Forum Supporter) :
Suddenly something I'd read recently about a completely different species of engine just clicked.
Somebody chose a GTX(90210)R turbo for a restricted stage rally engine because of the efficiency at high pressure ratios. 20psig manifold pressure requires around 3-4:1 pressure ratio when the turbo is pulling inches of vacuum between the restrictor and the compressor wheel. IIRC he said he was logging 10-15 inches and was tapering boost down to 12psi at redline using turbo vacuum as a guide to the power choke point, trying to keep the turbo from overspinning and requiring more power to turn than could be gained with additional boost.
Thanks for the additional information guys! I still have a lot to learn with turbos..especially with Garrett and how they classify them. Seems like the GT2560R may be a good change for my setup and see how that changes the feel. For some further specs on my current turbo it is a:
T3/T4 TO4E .48 A/R 50 trim, here is a link to the exact one I bought:
https://www.amazon.com/gp/product/B07WS6CYY7/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
Not entirely sure what the .48 A/R 50 trim means, but it looks like the GT2560R I found that would fit my inlet/outlet is also a .48 A/R:
Of course, its sold out currently and I still need to save up money anyway. But that has the exact flanges that I need to be a direct bolt in to my current setup, minus the need to modify my setup for water cooling.
I'm rusty on this - but I'm pretty sure a T3/T4 has a T3 flange on the turbine, a GT2560 has the smaller T2 flange. This would require modification/replace the of the manifold. I'm not sure what the T3 flange options are.
Water cooling is dead easy to add. It's literally replacing one water line with two.
Keith Tanner said:I'm rusty on this - but I'm pretty sure a T3/T4 has a T3 flange on the turbine, a GT2560 has the smaller T2 flange. This would require modification/replace the of the manifold. I'm not sure what the T3 flange options are.
Water cooling is dead easy to add. It's literally replacing one water line with two.
Ah okay, that may be a little bit of an issue then. The link to ATP says it has a T3 flange, but I guess that may be referring to the 5 bolt part, not sure. I guess I could get in contact with Garrett and confirm.
T3 refers to the input flange on the turbine - the part that bolts to the manifold.
Keith Tanner said:T3 refers to the input flange on the turbine - the part that bolts to the manifold.
Ah okay I had that mixed up a bit, thank you! Yeah so looks like the ATP Turbo folks are claiming the turbo to have a T3 flange, which from the pictures looks like it. Of course, theres no measurements on their site, just pictures and the claim that its a T3. My current turbo definitely has a T3. Hopefully the combination of the GT2560R and maybe some grippier tires can give the car quicker acceleration. That would be nice to have. I'm sure the fact that its an actual Garrett will make a difference as well, since who knows what kind of manufacturing the cheapo turbos go through.
Or go Borg Warner EFR 6258, and you'll never have to think about spool, or buying another turbo. Perfect size for wanting 300whp and the response is unmatched by anything else. If you already have a BOV, you can run the SXE compressor cover for an even wider powerband. It is available with a T3 flange.
Of course, the price is what it is.
The shape of the EFR may be a problem - iirc it's longer and you can't always just drop it in place of a Garrett if you have a firewall. Depends on the manifold design in that case. It would require a new downpipe.
My suggestion here is to forget the 300 hp thing because of the requirements for a new engine build and new transmission and rear end, and just build to within the capabilities of the stock parts -but better. So "300 hp capability" is not really necessary.
I'll be THAT guy .. If you've got a good running car that stays happy at 230 hp and you're thinking about going to the track, hit the track first, then plan upgrades.
You may find that your oil is getting too hot, your current intercooler isn't up to task, etc, at your current power levels. Or you may find that you have a great running car, but the suspension is letting you down, or the driver just needs more experience.. all of a sudden, that $8k you were going to spend upgrading becomes better spent as entry fees and consumables (tires, brakes, safety, etc.).
And you'll have a helluva lot more fun!
I'll add to that, if you're in driving distance of New England, let me know and I'll show you the best track time for dollar options around here, and I can instruct you when you get there :)
In reply to Keith Tanner :
IIRC, you won't have room for a downpipe with an EFR on a 'typical' T25 manifold. Kraken makes both normal and 'low' mount EFR cast manifolds and downpipes.
The other problem with an EFR is you'll be hard pressed to keep it under the torque threshold for stock rods.
In reply to WonkoTheSane :
+1 on getting to the track and bullet proofing what you have before making more power. You'll likely find the cooling system, and probably parts of the turbo system will need some attention for continued, reliable track use.
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