If EFR budget...
 

A two part query for you:

If you had the budget for a efr 7163 and a chassis waiting on power would you consider anything else (gtx, comp triple ball bearing, ect)?

Why?

I have the chassis, powerplant to support, and have done my research but need to get a new Mani built to insert said turbo and am looking for some other opinions. Thanks guys.

Not really. Maybe re-evaluate your power goals and decide whether you really want/need 500whp, and if you can live with 450, look at a 6758 to improve low-end power.

Although I agree that making sure 500rwhp is something you are actually looking for I would like to add that the testing I have seen of the two turbo's back to back show that the 7163 out performs the 6758 in almost every way because it is a gen 2 design.

EDIT: I also understand that this is a full throttle run and does not provide part throttle or transient response data but my throttle only has 2 positions anyway :party:

https://www.miataturbo.net/attachmen...ine=1404325846

EDIT 2: Not a built bp but the behavioral characteristics are still relevant.

Until there is an acceptable transmission solution I can't really recommend anything except 6258.

So the goal is 300 HP with low boost but also to have the ability to run a higher pressure and not be limited by the turbo or fuel. I feel I have the supporting items to do that before going with a new engine management system and a vvt head (these are the next steps for me).

get the 6258

I made you a chart
https://www.miataturbo.net/attachmen...1&d=1404398699

Gooby plz!

wish I could probab that 10 more times :bowrofl:

Get a 6258.

Along these lines... I already have a Precision 4828 which is supposedly a potato with some better parts. It is on a BEGI cast manifold. Would it make sense to move the precision turbo over to an EFR compatable manifold and fab a downpipe until I can afford to build the motor (hopefully get better spool out of it) or should I just hold off and do the EFR at the same time as the manifold/downpipe? I am at about 230whp now but I feel like I am not hitting 10psi boost until 4,300 rpm or so.

(my spool data:)
https://www.miataturbo.net/diy-turbo...2/#post1140285

Current downpipe is BEGI non-divorced gases pipe that exits to 2.5" and it continues 2.5" to the muffler at which point it exits at 3". I am holding off upgrading the mid-pipe until I also do the downpipe...

If my goal is to improve spool and reduce the amount of parts bought twice, where is the smart money?

Given the following future upgrades: build engine with forged rods, EFR 6758 or 6258, EFR compatable manfold, 3" turbo to tailpipe.

Also, consider that the block is stock for now.

if you want spool your money needs to go to tubular hotside parts and a proper 3" tbe
I'm also assuming you're already running ebc and the wga arm is tight. (forgot your mod list already)

^ Yes.

To isolate one question I asked above, can I mount my current turbo on a tubular manifold designed for an EFR? Obviously it would be a different downpipe than an EFR but if I am going to replace something, i'd rather it be the downpipe. Heck, I might even be able to modify the downpipe to make it work, but then that might be almost as much money as a brand new one?

Sounds like an efr it is. Thanks guys

One point here,

Never use a dynapack dyno to show differences in spool up of different turbos. You can program the ramp rate of the dynapack which allows you to set it to increase RPM's from 2000 to 4000 very slowly, and this will tend to make a large turbo spool at a much lower RPM than it would if RPM's increased at a faster rate. I'm not sure if other load cell dyno's can do this but I know that the dynapack can.

Keith

what is the availability like on these things now?

Stop using this graph please. The 6758 had the TGVs stuck closed on a bank and the 7163 was the pre-release version with the not as good compressor wheel.

This.

What's wrong with a TII drivetrain?

Gearing.

Doesn't look that far off from a miata 5 speed but has a longer 5th. (Going from memory here, haven't looked at the ratios in a couple months)

1-3 are also noticeably shorter.

The gearing is fine, unless you want to shave every second possible from your lap times, in which case I assume you already have a custom gearset for every track.

If you are not into track/autox, the TII/FD transmission is fine for up to 450-500whp.

But if you're not into racing the rx7 trannies are too hard to install, they dont bolt in.

The amount of fab work required to make them work is a small trade off considering the added reliability. I'm going TII because I don't want to deal with blown transmissions every few weeks. I also want to be able to still drive my car after it is making real power without fear of my drivetrain exploding at any moment.

The added time of installing one TII transmission is still less than doing a 5 or 6 speed twice

Yeah, but its a street car. You cant put non-bolt on parts on a street car.

Wut?

Just go with it. It's Leafy being Leafy.


If you NEED a TII/FD trans, chances are you're way faster than he is anyways, so does it matter? :rofl:

I started to write a response but realized he was probably trolling

Like i said... Leafy being Leafy. :giggle:

lol @ "TII gearing is fine"

Which car is faster: The 450hp Miata with the TII/FD transmission, or the 450hp Miata with the Miata 6spd?

How fast is the tow truck that is towing the miata with the 6 speed?

On a track the 2nd one will hold the faster individual lap time.

Assuming it can complete a single lap.

Let's put this another way.

Which car is faster on track:

1) 450hp Miata with an FD trans

2) 300hp Miata with a Miata 6spd


Because these two cars would hold together.

Does anyone actually know of a 6-speed being broken in a street car?

Faeflora









Ok maybe not the best example.

Does anyone making power enough to break a 6spd actually notice the "awful" gearing of the FD transmission in a street car?

Soviet would probably break one, but he doesn't drive it because he's paranoid about it after all the horror stories you track guys have posted. :party:


I'm getting confused though... the big argument FOR the 6spd was track performance when it's holding together.

Or are we saying that the superior geared but weak 6spd is better than the stronger FD trans on the street where gearing doesn't matter, and better than the FD on track where strength does matter?



I think the point a couple of us are trying to make is that if you're making too much power for the 6spd, the FD/TII trans is a solution that's available NOW that will hold pretty much any BP on the site, and costs peanuts. Ideal? No. Better and way cheaper than replacing a 6spd 4x a year? To many people.

The last FD tranny I saw costs just as much as all the other options we have that are just as strong as the FD tranny. 2-3 grand.

So get a TII trans. Jesus.

My FD trans cost me $600 and i had my pick of 4. These are not expensive transmissions, stop shopping on ripoff.com: The Leading Ripoff Site on the Net.


HAHAHAHAH, i didn't even click that that was a real site. Whoops.

*raises hand*

local kid sheared his 6th gear clean off the shaft

had crappy all season tires too

Bryan/FAB9

Looking at the gear ratio's, the RX7 transmission matted up to a 4.3 rear end wouldn't be a bad option at all. Now if you had a Miata that came with the 6 speed 3.909 rear end it would be pretty steep gearing!

If you are making 500 HP I don't see the RX7 transmission gearing with 4.3 rear end being an issue.

Keith

I would have pointed to the 3.9 or the 3.6 for the RX7 tranny. The FD tranny with a 4.3 is like having the 1st 3 gears from a 6 speed with a 4.10, then the 4th from a 5 speed, and a highway gear.

FAB9

If you give me a new 6 speed I'm sure I'll be able to break mine in short order.

The RX7 transmission with a 4.3 is like having the 1,2,3 of a 6 speed with a 3.636, not with a 4.1. 4th is a 1:1 gear, so it is the same no matter what rear end, and 5th will be a highway gear with what ever rear end you pick.

Stock 6 speed with 3.636 rear end at 7000 RPM (best combo for 6 speed)
1st 34.7
2nd 57.6
3rd 79.4
4th 103.9
5th 130.6
6th 155.0 and 80 mph = 3600 RPM

RX7 TII with 4.3 at 7000 RPM
1st 34.8
2nd 60.1
3rd 87.0
4th 121.1
5th 168.4 and 80 mph = 3300 RPM

RX7 TII with 4.1 at 7000 RPM
1st 36.5
2nd 63.0
3rd 91.3
4th 127.0
5th 176.6 80 mph = 3200

If you put the 3.636 gears in there with the RX7 transmission you are going way tall. If car was making enough power you would top out at 200 mph!

Not every Miata out there is a race car you know.

topping out at 200 sounds perfect for a 500+ hp miata.

Oh absolutely. Our cars are so stable and planted past 100.

But almost all of the cars breaking 6-speeds are :)

https://www.miataturbo.net/attachmen...ine=1404937437

I don't get it. Whats wrong with the RX7 T2 gear rations?

https://www.miataturbo.net/attachmen...ine=1404976008

On the street? Nothing. But when every tenth of a second matters on track, the drop from 2nd->3rd->4th is too wide. Compare the TII 2nd-3rd-4th-5th to the 6-peed's 3rd-4th-5th-6th, the 6-speed has much closer ratios.

If you can find a circuit racing gear set for it like this Our Website

But at that point it's probably cheaper to get one of the custom gear sets that will fit into a Miata transmission (5 or 6 speed) so I don't know how promising that is as an option.

but does the drop matter if I'm still on 400ftlbs torque curve? In my mind wide rations with good torque = less shifting = quicker

Torque doesn't make you go fast, horsepower does. And even if you make 400ft-lbs from 4000rpm to redline, it's still gonna be faster at higher RPMs.

Thrust math beggs to differ. If you have 400ftlbs, perfectly flat from 4000rpms to redline you're going to accelerate at the same rate from 4000rpms to redline. If you change gearing to keep you at higher rpms, then you're going to have better mechanical advantage on the ground and more thrust because of the gear ratios not the fact that you're at higher rpms.

Can we not use EBC to make a flatter HP curve?

is the point that I am missing that if you can get a bunch of low mid you should already have it?

Dann

EDIT: Leafy just because you explained it in a long winded way doesnt make you righter, thats what he was saying regardless, I think.

Then what about with 4.875 R&P? I do have those also

https://www.miataturbo.net/attachmen...ine=1404995640

4.8 seems excessive. If i were to do it with a BP, i'd go with a 4.3 or a 4.1 with the knowledge that you should be making enough power to shred 6spds on the regular.

MFactory® Competition Products - Gear Calculator





But this.... this is my jam right here.

https://www.miataturbo.net/attachmen...ine=1405002021

TQ and good gearing wins races. The thing is, that is almost the same thing as saying HP wins races.

The V10 F1 cars made fairly pathetic TQ next to say a Viper. But since they revved to like 17K, they could use gearing that would have a Viper topping out at 40 MPH. IIRC the rumor was that they would run 9s pretty easily, with only 300WTQ AFAIK

tl;dr The key is to have good TQ multiplication at all times. Having relatively wide gearing splits is not automatically a bad thing if you have the TQ band to match, and you get good multiplication from an aggressive rear gear. That TQ band has to be flat and extend to high RPMs. You can then stay in TQ, run decent TQ multiplications (aka not having to get into lower multiplication/high gears early on), and not have to shift so often either.