I was so confused for a moment until I realized it was measuring in newton-meters instead of ft-lbs. That is 222 in freedom units for any of you other Americans.

Twinscroll worth it?
 

I was baffled by the dyno with no way to zoom in because mobile app.

Yeah its in Newton Meters. But as you said its 222 freedoms at the wheels at 4286rpm, and 212whp@5157rpm

Its a virtualdyno run, but al the runs i did over a few weeks where very similair.

But i want something with more power and better spool. altough the spool of this turbo is pretty good.

you're not gonna get much better spool than that even with a t25
more power? sure, tons of options, at the expense of spool

that's a solid street powerband, I'd enjoy it

Gee fellows, is it time for a 2560 for the low end fun, plus something else for top end?

It can't prove that difficult. Can it?

corky

with variable turbine and compressor geometry you can have both...

The answer to both questions is: Borgwarner EFR 6258

I've no experience with the Borg turbo, but hopefully that will end soon.

Strong doubts remain that it will prove much different.

corky

Since that whole what happens in 5th gear thing was brought up like last page, my 6758 makes 2psi if you floor it in 5th at 45mph. That 5speed 4.10 gearing. Of course as always the bigger deal is that it drives like its just a bigger engine when you're over ~4k and into instaboost land. But its still no slouch below that. The EFR twin scroll housings are a bit odd, they seem to have sized them in an attempt to maintain the same boost threshold but flow better up top. which is different from how they're normally used.

A 6278 & a 6758. 45 in 5th is about 2200? And offers 2 psi. The 2860 matches that pretty easy, and the 2560 typically hits 4 at 2000 revs.

A VATN Aerocharger could be adjusted to make 10 psi at 1000, but it was undriveable. Best setting seemed like about 4 to 5 psi at 2k was good, but it was reluctant to make 200 rwhp.

Perhaps a 2860 and a VATN.............. I think I'll pass.

corky

I'm contemplating an he351. VGT holset. Can potentially be controlled with MS3. My buddy picked one up for $150. I think it might be sized a little big for a Miata. Pretty sure it has a hx35 exhaust housing.

Try it for science. Someone here questioned once upon a time the long term reliability of the vatn in a gasoline application, iirc. Nobody here has tried it to my knowledge. These turbos are very common on machines I sell nowadays.

I was very impressed with that one guy with an aerocharger a while ago making 200tq by like 2k and response so fast it was ridiculous. But his power plumetted up top and IIRC that turbo was unreliable

I know of exactly one variable vane gasoline turbo application. The turbos are readily available...for ~$5200/ea

Its a stupid heavy thing. At least 25 lbs. Will be interesting to see if I can build a manifold strong enough.
<br />I'm going to help him with running the vgt controller by megasquirt then search for my own. I've seen a dyno of a supra with his turbo. 20psi by like 2500rpm.

Biggest issue is they want to work at like 25+psi they aren't efficient below that. But I don't have a car that wants to work at 25+psi.

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Then it might be a poor choice? How many reasons does it take to become a bad idea?

Since when does bad idea = not fun? :) I'm going to play with some cheap turbos, just need to build an engine first.
<br />HX-30 if first on my list. Followed by the he351.

aidan - the new and improved faefae

Not sure if compliment or insult... :)

new and improved because your car ACTUALLY runs, so it's a compliment.

he was very entertaining when he wasn't drunk posting

I've seen his posts. Looks like a fun guy. Does he still have his Miata? Just gave up on it?

Is the 2860 or the aerocharger that can make that boost down low also capable of 450hp?

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Is there a Miata transmission solution for 450hp at a reasonable price? Until such time, why would above 350hp matter?

because then we can say we drive 450hp cars even though they've never been past 250 :giggle:

Rx7 trans is pretty reasonable. Ratios just aren't good for road racing so it gets no attention here.

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How about just build a fast spooling 300rwhp 2560 setup? Compromises.

I need to look into this. With the SC it has plenty of torque, just needs longer spaced gears. A much taller 1st and 2nd would be great.

The RX-7 Turbo transmission actually has decent ratios for road racing shifting @7,000 rpm gets you about 4,500 in 3rd (from 2nd) and around 5,000 anything above that except from 1st to 2nd which is low 4,000. Most turbo cars are making almost max boost in those ranges.

Somewhere in the transmissions options thread the rx7 box is dismissed. Not sure why.

Well depending on the amount of power you make (well torque), they can have issues with 3rd gear on track (north of ~300-350 ft.lbs.)

What are you running for a trans?

I currently have a RX-7 Turbo but most likely will switch is out for a dog-gear of some sort in the very near future as I know the turbo transmission will be on borrowed time pretty much right away!

Drop on shifts only really matters for drag racing. The issue when using it for road racing is that you're either too low in a gear or too high in a gear while in a corner.

Do you happen to remember the name of that thread? I searched for it but didn't find it. I've seen it before, and I believe someone (Sav maybe?) posted charts with the RPM drops for each gear for the RX7 and 5 and 6 speed miata transmissions. I wanted to go through that thread again.

Gearbox options and experiences
<br />https://www.google.com/url?sa=t&sour...La1wvNJtMSqHZA

You just shift then? But joking aside, the gearing is pretty standard compared to other 5 speeds. Sure if you have a 6 speed, then you have a close ratio. But I rather not drive a 6 speed on a road course, just too much shifting for my liking. Carry enough speed in the corner, then you won't be too low in a gear.

Thank you sir!

Wildly oversimplified. Carry too much speed and you can't use the low gear, which forces you into the next higher gear. On a box like the Rx7 TII box, that means you're way, way down in the RPM range.

Just read through that thread, thanks again.


From poking around, I've found numbers thrown out of people racing cars with the TII transmission at 350whp reliably. Street cars with more.

I don't know crap about gearing as it applies to track use.

But I do have a question for anybody who has an opinion/experience: Is the RX7 TII transmision stronger than the Miata 6 speed? All other things aside, is it at least a stronger box? It seems that it is from my reading online.

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With a narrower powerboats than optimal I was quite pleased with the 6sp+4.875 combo at the last race (effectively very tight ratios and small drops).
4-5-6 around the whole track (no gears to strip in 5th).
Shifting at 7.5k btw.

1st is a nice trailer gear. :)

Yes, it is oversimplified. However what are you guys considering way down in RPM range here? I am not sure if what you guys are describing really needs to be fixed with the rear-end ratio rather than the transmission. Otherwise realistically the best 5sp option would be something without an overdrive.

Racing RX-7's, if the car is non-turbo, nobody touches the turbo transmissions because of the tall gears and the uber-lack of torque. But with turbo, the torque is not as much of an issue.

After I built the motor the 2560 wasn't enough. So after a lot of research I decided on using the MHI Twin Scroll TD05HR-16G6 10.5T. Reasonable priced, rebuild costs aren't bad. I been super happy with this choice. The spool up is great. (I want your spool data post #219)
That said, the header was a challenge to fabricate, so I would vote yes to a cast manifold for others to try this segment of turbos.
I don't know the answer to this but since most people start with stock motors would this flange fit other MHI turbos so as you upgrade the motor you could still keep the manifold and choose a higher flow turbo as necessary. Also the exhaust spacing between Mitsubishi and the BP4W head is very similar so maybe there are two potential markets here.
For what it's worth, here's the link to my set up:
https://www.miataturbo.net/diy-turbo...o-build-79259/
Cheers,
-JB