Yeah all that should be the same as the rest of the NB setups.

 

I'm trying to figure out the nicest, most polite way of telling you to stop asking really stupid questions in every "turbo kit' thread and start reading up about these cars and what the differences are.

Pro-tip: new product announcement threads are not the place to learn the basics of miata's. Bombarding vendors with completely clueless questions is also a bit unfair because you're forcing them to spoon feed you the most basic of info, with no guarrantee of them gaining your business/money.

I mean this in the nicest way possible. Please learn a little before waving money around and making clueless decisions.

 

As an EFR6258 owner, I can't say enough great things about the turbo. My question is, for a more track intended application around 300whp, would you recommend the 6258, or jumping to the 6758 for lower boost and lower temps. How's the spool and response difference between the two?

 

No specific "MSM version", but that's because once you strip the MSM manifold/turbo/downpipe from that car, it essentially becomes a normal NB2. Ergo, the kit will fit MSMs just fine. It will essentially be a standard NB kit with slightly tweaked oil lines.

I wouldn't upgrade to a 6758 until ~350whp. To fully answer your question, let's put the idea of "inefficient at higher boost" to rest, because it's a relic from the years of old Garrett GT-series compressors. The EFRs are extremely efficient at high boost. To show this, let's look at compressor maps.

Footnote: Pressure Ratio is calculated by adding boost pressure to atmospheric pressure at your altitude, then dividing by atmospheric pressure.

Sea level:
14.7psi = 2PR
18.4psi = 2.25PR
22.1psi = 2.5PR
25.7psi = 2.75PR
29.4psi = 3PR).

I am also using a brutally simplified formula to quickly convert from wheel horsepower to corrected airflow (whp / 9.1 = lb/min). A real engineer can do the real math if they'd like, but the simplified formula gets us close enough for this discussion.

Garrett GT2560R Compressor Map
WN3PKd4.jpg

Here's a GT2560R compressor map. Most people run that turbo at ~250whp (~27.5lb/min) and ~15psi (~2.0 PR). Plotting those points on the compressor map puts you at ~72-73% efficiency, and it's clear that you're starting to fall off the upper edge of the efficiency island.

Let's say you decide to max that turbo out and seeing ~18psi(~2.25 PR) at around 300whp (~33lb/min). Plotting that point on the 2560R compressor map has you at the very, very edge of the published map, at an efficiency of ~68%. This is why you rarely see more than 300whp from 2560R setups, and the people who do make 300whp typically have fully optimized cars (2.0L shortblocks, ported heads, etc).

Let's look at the EFR6258 map in comparison, and plot the same points.

BorgWarner EFR6258 Compressor Map
NlhAMsp.jpg

At 15psi and 250whp, the EFR hasn't even gotten started. Efficiency is 74-75% and you're at the very bottom of the efficiency island. Adding boost doesn't harm efficiency at all. At 300whp (33lb/min) and 18psi (2.25PR), you're square in the center of the efficiency island at 75%. You don't even begin to run off the edge until you're well north of 20psi and 350whp.

The EFR6758 takes this idea (high boost efficiency) and turns it up to eleven.

BorgWarner EFR6758 Compressor Map
KT7oihY.jpg

Even in the low 400whp and mid-20psi range, the EFR6758 is still able to maintain >70% efficiency, which is huge for our ability to make big power on a relatively small-displacement engine.

So the short answer to your question is this: No, you don't need to step up to a 6758 for a 300whp track car. At 350whp, I would consider making the jump.

I have yet to drive a 6758, but from what I have been told, the difference is minimal. Once I have the 6258 dialed in a bit better, I will spend a week or two on the 6758 to get an idea of how much laggier it is. I am expecting a minimal response change and maybe ~200rpm of delay in the boost curve.

 

Wow, I just learned a lot, thanks! Nice to actually be able to understand the compressor map, and how to figure that stuff out. Sounds like the 6258 will be the best option for most people, as I understand a 300whp track car is not exactly reliable, 350 is just

 

Great info, Andrew. Now if only someone would make a transmission solution for boosted BP's that survives anything other than Cars and Coffee at 300+ whp

 

could a garrett t2 also be mounted to this? I've already got a turbo set up but I really like this manifold.

 

Anything with a t2 flange could be mounted to it. The rest of the kit wont work though.

 

It's a standard T25 flange, so any Garrett with a T25 turbine housing (2554R, 2560R, 2860RS, all the GTX28s, and some GT3071s) will bolt up. You'll need to build your own downpipe.

 

A bit of thread drift..

We have a customer we are building an "everything" engine for. Billet crank, the works. It'll be an SSM autocrosser. I learned he had an FMII with a GT2554R and suggested he talk to Andrew about an EFR 6258 TSE kit so he can fully utilize the capabilities of the engine. A few calls later and the plan now appears to include a 6758 based TSE kit. I then suggested he start researching transmissions so he could turn the boost all the way up. If the 6758 happens, I think we'll see a genuine 8000rpm 450whp with fantastic spool and a torque plateau like no other.

 

: party: arty:a rty:

 

Wow, with two of you behind the project, this will be a hit like no other.
Too bad its an autocross car, rather than track focused car: with the power and your ingenuity I can speculate Formula Mazda laptimes would be possible.

 

Isn't the 6758 "wasted" on an autocross car?
ie. Wouldn't a 6258 be better suited?

 

What has been posted before on 6258 vs 6758 is that spool time between them is expected to be minimally different, on the order of 300ish rpm. So the real reason to not go 6758 is that there's no solution for a transmission for a 400whp miata that's driven to anything other than cars and coffee. Bundy in autocross trim has 300whp, and with 275 Hoosiers he eats 6 speeds.

For a dedicated autocross car of the magnitude being discussed here, though, the individual in question may have the resources available to source custom solutions that are impractical / out of reach for the rest of us. He'll only need two gears and reverse.

 

SSM cars need to make more power than a 6258 would be capable of, and the 6758 gives up very little to the 6258 in terms of response.

 

There is the jerico 4 speed, quafie 5 speed (which works for bob now), and there is also a T5 option (not begi, the ebay one discussed.). Its just a matter of how well they actually work.

 

I have a question in regards to the manifold design.

With this setup being focused towards the track crowd and EFR's, why go with a T25 turbo flange over a V-band?

I was looking into possibly switch my 6258 over to the 7163 IWG V-band and noticed that all the B1 frame EFR's offer a V-band IWG option now, but just with a bigger A/R.(i.e. The 6258 with the t25 has a A/R of .64 and the IWG V-band option is .85)

Wouldn't the V-band be more reliable the the track, or would the increased A/R kill the spool and powerband that these turbos are known for?

 

Because the bigger A/R ruins the sexy spool.

 

From the first page.

 

God damn it... Sorry guys, I just read through this thread before posting too. I need to stop sucking at life. Maybe I need glasses or reading lessons. Thanks for sharing though.

If someone could just delete these last posts so they don't clutter this thread with stupidity that would be appreciated.