DIY Turbo Discussion greddy on a 1.8? homebrew kit?
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Old 02-21-2017, 09:41 AM
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Originally Posted by Savington View Post
Could be, but that would surprise me since it's a radial tire. It's a substantial reduction, over an inch of circumference loss IIRC. I don't actually have a good theory for why the GPS speeds are lower than the calculated speeds, but I do have a bunch of repeatable data that shows it to be true
If you ever have a chance to get more data, a dot on the rim with a dot near the edge of the tread on the tire, a bight sunny day and a camera with a fast shutter speed will give a great data point.
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Old 02-21-2017, 11:49 AM
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How fun it'd be to use digital image correlation on a tire to measure full field strain and deformation. Just need Vic2D/3D and one or two high frame rate cameras Photron SA1 etc.
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Old 02-22-2017, 02:22 PM
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Originally Posted by Savington View Post
Oddly enough, tire deflection ends up making the tire shorter, at least in the 140-150mph neighborhood. Maybe 180+ would change that, but the data I have says you need about 6% more RPM than you think you do to reach a gear-calculated speed.

That makes sense, we use 3.636 in Europe and every car i know makes 10km/h aprox. less than the gear calculator gives @7200rpm 6th gear. Never understood why.
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Old 02-22-2017, 03:03 PM
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Theseus had a 7400rpm limiter, 3.909s and a 6sp. Gear calc says 153.7mph at redline in 6th, GPS said ~146.2mph every time.
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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 02-22-2017, 03:37 PM
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I wonder if it's a result of intentional unilateral tolerancing. Ever notice how every car's speedo tends to be a little too optimistic? I have to think it's driven by liability concerns of the manufacturer which make them tolerance the speedo to over report speed rather than under report speed. Perhaps the gear ratios and therefore top speed of a gear at a given RPM is also slightly unilaterally toleranced to avoid exceeding the limit of the design envelope. Just an armchair conspiracy theory.
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Old 02-22-2017, 05:47 PM
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Originally Posted by wackbards View Post
I wonder if it's a result of intentional unilateral tolerancing. Ever notice how every car's speedo tends to be a little too optimistic? I have to think it's driven by liability concerns of the manufacturer which make them tolerance the speedo to over report speed rather than under report speed. Perhaps the gear ratios and therefore top speed of a gear at a given RPM is also slightly unilaterally toleranced to avoid exceeding the limit of the design envelope. Just an armchair conspiracy theory.
Speedometers lie, but this is a comparison between a gear calculation and the GPS measured speed. The ECU's RPM signal doesn't lie (not the tach, but the one that drives the rev limiter), because it has to be accurate for the engine to run properly.

You can't really tolerance a gear -- count the teeth and that's the ratio.

I don't know how accurate GPS measured speed is, though.

--Ian

(edit): One other thought, if you're getting a few percent of tire slip, then that would account for some of it.
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Old 02-22-2017, 06:30 PM
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My data is from a 10hz antenna fed into a Racepak, then extrapolated to 20hz. More than accurate and repeatable enough to clearly show a discrepancy between "what is" and "what should be"
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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 02-23-2017, 07:26 PM
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Originally Posted by Savington View Post
Have you called and spoken with me yet? I could clear up a lot of your misconceptions in a ~20 minute call.
Not yet Andrew! I gave you a call when I had a free moment the other day, but you were busy.
This wont happen for another year or so...I am not in a huge hurry.

We are going to bolt the suspension/safety stuff together and he is going to spend the spring and summer doing HPDE, autoX and, spending the rest of his money on instruction.
The plan is to allow him time to establish solid control of the car before adding power. If that takes two years so be it.
I would also like him to get some wheel to wheel experience before the turbo, but that is still being discussed.
Once the turbo goes on the plan is to run it at lower boost until he connects with the power and feels good control over it. (one of the reasons I was talking about a dual port boost solenoid).
I suppose a smaller spring could be supplemented.

For those that asked?
I have a 580hp Sunbeam Tiger, and used to have a 740hp Cobra...Not to mention a host of scary fast longer wheelbase cars.
To me the 350hp Miata I drove was edgy and a sporty ride, but was completely predictable....A long way from the Tiger.
My son of course is not in the same boat....and there was no way he was going to drive that car.
See my above comments to Savington, but the plan is to work him into the power as slow as it required.

Eo2k,
If it was me I would have to know how much power I could make.
There has to be some curiosity there?

Thanks for all the comments as always!

Jamie
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Old 02-23-2017, 07:58 PM
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I have tempted him to come down and do a "ALLOFIT" tune on e85 dozens of times now.

If he ever bites, I will be sure to share the videos
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Old 02-24-2017, 01:31 AM
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Originally Posted by 18psi View Post
I have tempted him to come down and do a "ALLOFIT" tune on e85 dozens of times now.

If he ever bites, I will be sure to share the videos
Haha!
That would be awesome!
The torque would be insane!
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Old 02-24-2017, 12:12 PM
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Psssht! Who needs a turbo? 300hp N/A BP. Suck it, Trebek!

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Old 02-24-2017, 12:42 PM
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Originally Posted by EO2K View Post
Psssht! Who needs a turbo? 300hp N/A BP. Suck it, Trebek!

Pretty sure both Emilio and Savington have debunked their HP claims in this thread here.
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Old 02-24-2017, 12:46 PM
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sarcasm is hard to convey in a post
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Old 02-24-2017, 01:55 PM
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"A little shy of 350hp".....A little short!
I am a little short of 12 inches....I am closer to 12 inches than they are to 350hp!

Your link didn't work for me Shuiend.
I would enjoy that read!
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Old 03-05-2017, 02:49 PM
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For a while now, this forum has been reformatting urls so they do not link properly

https://forum.miata.net/vb/showthread.php?t=630740
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Old 03-05-2017, 08:28 PM
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Emilio: "Cutting edge K Series 2.5L spun to 11k in drag cars are just hitting 395whp on VP Q16 gas. A stock K20A2 head flows a bit over 40% more than a BP4W."

Or said another way....

Savington: "350bhp from a naturally aspirated BP on gasoline is a monumental pile of BS."


Priceless!
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Old 11-08-2017, 10:26 AM
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Any update on the 5951 from SEMA this year?

Still a mid-2018 release?
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Old 11-08-2017, 02:43 PM
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No 5951s on display at BW this year. Rep said they are still in progress, no ETA, definitely not a mid-2018 release.
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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 01-23-2019, 04:59 PM
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Any updates on the 5951?
I haven't seen anything recent about it.
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Old 01-24-2019, 02:54 PM
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I would also like to know about what happens with this turbo. Seems to fit exactly with what my goals are.
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