DIY Turbo Discussion greddy on a 1.8? homebrew kit?
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Old 02-15-2017, 10:34 PM
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Originally Posted by 18psi View Post
I see what you mean about torque drop off, but I'm not sure I'd agree that a "well working turbo" is one without any torque drop off up top. The way I look at it, if power isn't nosing over, there is still room to push it and the limit is not reached.

I did this on a very conservative CA91 pump gas tune on a 6258


Boost is not really dropping that much (it's shaky due to weak actuator) and power aint dropping, I say it will do 350 on good gas without too much effort
Now there is a tune!

That is a lot better looking than the other plots I looked at....Not in the same ballpark!
The torque is low in the range, but it only drops 50flbs over 3000 rpm...Which is downright amazing compared to the others I have seen.

Why would anybody want a torque curve at lower rpm than this? You are already making almost 10psi and 200Ftlbs @ 3000 rpm? First and second gear tires on fire?
A smaller turbo will move the torque band lower making traction more problematic while punishing you on the shortest of straights.

Does this motor have the VVT head?
I understand it makes boost come on sooner, but offers no horsepower gains at higher rpms?
Does the torque curve broaden at all?

Thanks for commenting!
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Old 02-15-2017, 11:14 PM
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There are factors far beyond the turbo when it comes to motor setup. A squaretop IM will carry torque past 5000rpm better than a VICS manifold, as long as the turbo can carry it. VVT cams will see a slight falloff past 6500rpm in exchange for better torque between 3500 and 5000rpm. You can't just look at a single plot and use it to assume the behavior of the turbocharger. You have to look at lots of data to get a better idea of what the turbos are capable of.

The 5951 will respond better and should still make 250-275whp on top, which is why people here are interested in it.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 02-16-2017, 02:47 AM
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The 5951 will respond better and should still make 250-275whp on top, which is why people here are interested in it.[/QUOTE]


This. If it existed I would have gone this route for the street all day long. I don't plan on switching from my 6258 though.
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Old 02-16-2017, 11:22 AM
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Originally Posted by nbfather View Post
Now there is a tune!

That is a lot better looking than the other plots I looked at....Not in the same ballpark!
The torque is low in the range, but it only drops 50flbs over 3000 rpm...Which is downright amazing compared to the others I have seen.

Why would anybody want a torque curve at lower rpm than this? You are already making almost 10psi and 200Ftlbs @ 3000 rpm? First and second gear tires on fire?
A smaller turbo will move the torque band lower making traction more problematic while punishing you on the shortest of straights.

Does this motor have the VVT head?
I understand it makes boost come on sooner, but offers no horsepower gains at higher rpms?
Does the torque curve broaden at all?

Thanks for commenting!
Thanks, it's an absolute blast to drive, as I'm sure EO2K can attest.
As everyone said it's all about insane fast response (though the 6258 is not lacking in that department either), and I think during normal street driving, you're not necessarily wringing out every gear, so that when you're in 4th/5th/6th at say 2500rpm (think of your typical 45mph city street), more torque down there is always welcomed. Especially when you're running proper 3.6 final drive

*edit: its basically the same reason people throw twin screw's on v8's: no one needs 500wtq at 2500, it mostly results in tire spin in the lower gears, but chugging along effortlessly at 2500 without even revving the engine to propel the car like a locomotive definitely feels amazing.

Last edited by 18psi; 02-16-2017 at 12:48 PM.
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Old 02-16-2017, 11:30 AM
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Originally Posted by Savington View Post
The 5951 will respond better and should still make 250-275whp on top, which is why people here are interested in it.
This will be the best stock-block miata turbo. If I get my car fully tuned NA this year, then perhaps I can turbo it with a full TSE kit next year.
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Old 02-16-2017, 11:39 AM
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Keep in mind that stock rods won't appreciate boost even earlier in the rev range.
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Old 02-16-2017, 12:39 PM
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Yeah, what I had in mind was a rods-only rebuild, but then why not get the 6258... I will be in the market when the whole TSE kit is ready. I have been through 5 other cars since it was initially announced, but I still have my ratty 01 SE that would be perfect for a track-ish build.
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Old 02-16-2017, 05:27 PM
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Originally Posted by Chilicharger665 View Post
Yeah, what I had in mind was a rods-only rebuild, but then why not get the 6258... I will be in the market when the whole TSE kit is ready. I have been through 5 other cars since it was initially announced, but I still have my ratty 01 SE that would be perfect for a track-ish build.
TSE kit IS ready? What'reyou waiting on?
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Old 02-16-2017, 06:20 PM
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Is this about a transmission solution?
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Old 02-16-2017, 07:02 PM
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Originally Posted by Onyxyth View Post
TSE kit IS ready? What'reyou waiting on?
he's talking about a complete turbo kit
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Old 02-16-2017, 08:41 PM
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Originally Posted by 18psi View Post
Keep in mind that stock rods won't appreciate boost even earlier in the rev range.
On the money!
If you are making +- 6 pounds at 2000 rpm a smaller EFR will probably make 10-15 there.....I can only imagine how much boost it would make with a bit of anti lag!

With 10+PSI on tap the temptation will be to roll on at at low rpms...Which will induce LLSPI ( Low Speed Pre Ignition) with stock pistons.
Those stock rods will fold in days.
Timing wont fix it as LSPI happens before the ignition event. The only fix it is to go pig rich at WOT under 2500ish rpm....Not a long term solution

Hard to say 100% before it gets here, but rods and pistons are pretty much going to be essential.
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Old 02-16-2017, 09:33 PM
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Even with the 6758 having a few psi at 2k rpm in 5th gear made it temping to roll on at like 45mph because noises.
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Old 02-17-2017, 12:49 AM
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Originally Posted by nbfather View Post
On the money!
If you are making +- 6 pounds at 2000 rpm a smaller EFR will probably make 10-15 there
Ah, no. Not only do 6258s not make 6psi at 2k, a 5951 isn't going to tack on 4psi to that. Maybe 1psi at best over what a 6258 can do down low.

With 10+PSI on tap the temptation will be to roll on at at low rpms...Which will induce LLSPI ( Low Speed Pre Ignition) with stock pistons.
Those stock rods will fold in days.
Timing wont fix it as LSPI happens before the ignition event. The only fix it is to go pig rich at WOT under 2500ish rpm....Not a long term solution
LSPI is virtually unheard of in port-injection engines. It's only become an issue in GDI engines with tons of static compression and tiny, tiny turbochargers. Way smaller than the 5951 being discussed here. On a 9:1 port injection motor, it's a non-issue.

Hard to say 100% before it gets here, but rods and pistons are pretty much going to be essential.
I think that's a hugely premature statement to be making, based on dubious assumptions at best. We're talking about a 59mm/51mm wheel combo. 2554Rs use a much smaller compressor wheel than that (54.3mm) with a turbine that's not much bigger (53mm), and nobody complains about rod-bending torque or LSPI in those. You can even get a version of the T25 thats smaller than that, and I've used that turbo successfully on a stock engine. Everyone here swore up and down that EFR6258s would blow up every stock motor too, and that never came to fruition either. Should you be tuning a small turbo to the ragged edge on pump gas? Probably not. Is it a foregone conclusion that a small turbo will bend the rods on a stock motor? Hardly.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 02-17-2017, 09:22 AM
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Originally Posted by Savington View Post
LSPI is virtually unheard of in port-injection engines. It's only become an issue in GDI engines with tons of static compression and tiny, tiny turbochargers. Way smaller than the 5951 being discussed here. On a 9:1 port injection motor, it's a non-issue.
Is it a non issue because of the lower compression and port injection? Or because neither turbo will make more than low single digit boost down that low? How about if there was a supercharger or something capable of making 8-10psi at those TPMs? 15? 20? Or is that just a matter of tuning like higher RPM where you just need to get timing and mixture right?

Sorry for all the questions, I have never heard of this before at all. Itcs these tidbits of info that I don't know that I don't know that keep me reading these threads. Will have to do some googling later on it.
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Old 02-17-2017, 01:26 PM
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Originally Posted by x_25 View Post
Is it a non issue because of the lower compression and port injection? Or because neither turbo will make more than low single digit boost down that low? How about if there was a supercharger or something capable of making 8-10psi at those TPMs? 15? 20? Or is that just a matter of tuning like higher RPM where you just need to get timing and mixture right?
All of the above. You need a very small engine, a very small turbo, a cam profile designed to make lots of boost and torque right off idle, direct injection so your fuel spray disturbs the oil layer on the cylinder walls and creates a homogenized fuel-oil mixture, and an oil with high calcium levels (apparently). The short answer is that it's never going to be a problem for us.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 02-17-2017, 03:28 PM
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Originally Posted by nbfather View Post

Why would anybody want a torque curve at lower rpm than this? You are already making almost 10psi and 200Ftlbs @ 3000 rpm? First and second gear tires on fire?
This, 100 percent. Only people who tune these cars desire this, and fail to acknowledge a characteristic called diminishing return. "My goal is to have all my torque before 2500 RPM and accept a massive amount of torque loss over the last 2500 RPM of my power-band, because torque wins races and I am way too literal!"... Give me a ******* break ha. But seriously, a 6258 (on any 1.8 Miata engine, I.M. aside, cam aside) spools plenty fast enough, and damn close to optimum. Torque 1000 RPMs sooner than a 6258 will not gain you anything.
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Old 02-17-2017, 03:36 PM
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It may not gain you anything. But a lot of people want torque right off the bat.

Look at any new turbo car. Torque asap, and choke up top. Just cuz you have some idea of what "everyone wants" doesn't mean you are right.
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Old 02-17-2017, 03:39 PM
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Originally Posted by NBoost View Post
This, 100 percent. Only people who tune these cars desire this, and fail to acknowledge a characteristic called diminishing return. "My goal is to have all my torque before 2500 RPM and accept a massive amount of torque loss over the last 2500 RPM of my power-band, because torque wins races and I am way too literal!"... Give me a ******* break ha. But seriously, a 6258 (on any 1.8 Miata engine, I.M. aside, cam aside) spools plenty fast enough, and damn close to optimum. Torque 1000 RPMs sooner than a 6258 will not gain you anything.
Must be painful to be ignorant
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Old 02-17-2017, 03:47 PM
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Originally Posted by aidandj View Post

Look at any new turbo car. Torque asap, and choke up top. Just cuz you have some idea of what "everyone wants" doesn't mean you are right.
I have always considered this an American automotive culture thing. How do you want your shirt, plaid or striped? One not necessarily better, just personal preference.
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Old 02-17-2017, 03:48 PM
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Of course its preference. I'm just saying there are obviously people that want it. Where NBoost seems to believe everybody is exactly like him and only wants max power.
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