EFR 6258 vs 6758 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 11-11-2014, 03:16 PM   #1
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Default EFR 6258 vs 6758

So right now I have the 6258 at 17psi making 311/285. I am very happy with the numbers, but I am reading more and more that the 6758 can make more power, and the loss of spool is marginal. Who's made the upgrade and what have you noticed? What kind of power can the 6758 make on similar boost?

IIRC the outside dimensions are identical so it would just be a straight bolt-on swap.
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Old 11-11-2014, 03:19 PM   #2
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You need a 7163.

Do it.

For great justice.
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Old 11-11-2014, 03:30 PM   #3
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I don't want to re-do my manifold and exhaust. I also don't see a need for the kind of power it can produce in such a small car. That's why the 6758 is kind of an idea. Not something I'm guaranteed to do, but if I knew I could sell my 6258 (3000mi) and get a 6758 with marginal difference in cost, I would consider it.
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Old 11-11-2014, 03:33 PM   #4
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I think soviet is the only one.
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Old 11-11-2014, 03:45 PM   #5
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Funny how Russians think alike hah
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Old 11-11-2014, 03:46 PM   #6
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I just went straight for the 6758 after soviets experience.
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Old 11-11-2014, 03:53 PM   #7
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I went for the S366.
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Old 11-11-2014, 04:04 PM   #8
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Are you stuck on 17psi for some reason? The 6258 should be able to make more power as you increase boost, if more power is what you are after. It would likely be less expensive than buying a 67 and taking a loss on the 62.
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Old 11-11-2014, 04:34 PM   #9
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Quote:
Originally Posted by Mazdaspeeder View Post
I don't want to re-do my manifold and exhaust. I also don't see a need for the kind of power it can produce in such a small car. That's why the 6758 is kind of an idea. Not something I'm guaranteed to do, but if I knew I could sell my 6258 (3000mi) and get a 6758 with marginal difference in cost, I would consider it.
The 7163 is on the same frame as the 6258 and 6758. I believe it is a direct swap turbo. You would want to verify that but I am 95% sure that is the case.
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Old 11-11-2014, 07:44 PM   #10
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How much more boost can I run with 93 octane and ~8.6-8.8 compression?
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Old 11-11-2014, 07:49 PM   #11
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All of it.
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Old 11-11-2014, 08:08 PM   #12
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Pretty sure FM proved that the GT2560r is just as good so why don't you just get one of those?

(I can't tell if I laid the sarcasm on thick enough so I wrote this footer)
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Old 11-11-2014, 10:33 PM   #13
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Which one does the Trackspeed Engineering kit use? I would use their R&D and follow suit (since we laying on sarcasm).
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Old 11-11-2014, 11:27 PM   #14
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Funny thing is that listening to people on this site, looking at Soviet's thread, and the mythical TSE turbo kit, I just decided to put together my own package. I love driving this car, it feels incredible. So really, how much boost? My timing according to tuner is still pretty conservative.
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Old 11-11-2014, 11:36 PM   #15
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How much boost? All of it.
How much timing? All of it.

But seriously, I'm only half joking here. If you're at 17psi, that turbo should handle well into the mid 20's, and if your timing is conservative, you should be able to bump that up another 5* or more depending on load.

The issue then becomes with fueling: you can only go so far on pump gas. Then you need water/meth/etc or run e85 or race gas.

Then you will start running into much more important problems, like replacing grenaded transmission, diff, axles, etc.
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Old 11-11-2014, 11:42 PM   #16
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I already have an MSM diff with the bigger axles, and it's a puddymod stage 2 cryo treated and with 3.63 mated to an MSM 6-speed via a super miata driveshaft, and fm lvl2 clutch, if that matters.

I get 93 octane, will talk to tuner and see what he thinks.
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Old 11-11-2014, 11:51 PM   #17
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At over 400whp, all that stuff will be pretty much at or past the limit.

Also something to consider is uncorking more power with more flow. Like a squaretop or honda mani, tb, and maybe even cams.
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Old 11-11-2014, 11:55 PM   #18
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Quote:
Originally Posted by concealer404 View Post
You need a 7163.

Do it.

For great justice.
That's what I'm doing lol. Just picked it up today
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Old 11-12-2014, 12:17 AM   #19
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Quote:
Originally Posted by 18psi View Post
At over 400whp, all that stuff will be pretty much at or past the limit.

Also something to consider is uncorking more power with more flow. Like a squaretop or honda mani, tb, and maybe even cams.
I was considering the squaretop or the Honda d or h series manifold. I have 2" intercooler piping but that's plenty large, it's the same size as the cold side exhale port (I forget the name) on the turbo

Weight reduction is another idea. Might want to ditch ac. Anyone know what the compressor and condenser are worth in lbs?
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Old 11-12-2014, 12:20 AM   #20
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2" ic piping, if I'm not mistaken, should max out near 400hp at full tilt assuming no sudden bends or anything
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