I'm pretty sure Garrett doesn't have a room full of dynos and motors it tests these turbos on. They have specialized test equipment that tests the turbo itself, not what it does on a motor. They use sponsored drivers for their real world testing. You should see the data sheets they ask their drivers to fill out after every race.

I haven't had time to read this entire post yet, but here is a datalog in case anyone cares. The turbo is a ball bearing, GT2860rs. Full boost seems to be about 4200rpm. This dyno is really bad, but does seem to give a good ball park. And you can see immediate changes while having a safe place to tune. My friends and I are really the only ones who use it. Its $80 per car, no real time limit.

As for me, the car hauls ass and I am totally thrilled. Anytime a miata is out destroying "compensating" cars is good for all of us.

Attachment 210822

Looking at Ray's plot against a couple other Greddy setups, I say it's feasble at 6.2psi.

I'm pretty sure both these plots were at 7psi or so.

This is that7guy's setup, like i said, I believe 7psi, but an obvious drop in boost after 5K like most greddy wastegates. On the stock ECU. Spool-up is identical. Looks like that same power could have been had if boost held.
http://www.boostedmiata.com/dynos/sevan_vs_ray.jpg


This is Mach929's plot. EMB piggy. Again very close here...and IIRC 7-8psi
http://www.boostedmiata.com/dynos/phil_vs_ray.jpg

This is one long thread. I'm up for dynoing my car on a free day. The map I am using is so off. I have cruise in pretty good. But as soon as I hit boost, 10afr's. I had it better until I used megalogviewer. It sent everything way rich.

I think the only thing I learned in this whole thread was the explanation of why different turbo's make different hp on the same boost. That helped me alot. I was brain storming on that.

But other than that. it ran together into la la la la LAAAAAA! LOL


I need booby's after that.

Sorry, won't be free. It is a business, and I don't own it. We could do 3 pulls with A/F for $40.

You still up for a run?

thats a good price lol

Yea, thats cool.

As far as the pulls, thats cool, but I need to get the tune in better before I dyno.
I'm about to go oustide and reflash my firware and try to work toward brains spark map he sent me.

Cool.

It was brutal out there, and I had to do a bunch of off road driving and get paid a lot for it, but I'm back.

Yes, that would be my definition of fucked up.

But about your game and your equation. You forgot to make the correction from DIN to SAE, so your formula should look like this:

246 = (x + 14.7 / 14.7) * 116 * 1.15
1.844 = (x + 14.7) / 14.7
27.1 = x + 14.7
12.4 = x

Correct?

Here's the upper half of my spreadsheet of the same set of equations:

Airflow Required
Input Parameter Units Value Notes
H.P. Target 218
Air/Fuel Ratio 11
Brake Specific Fuel Consumption lb/(H.P.*hr) 0.5 Use 0.5 to 0.6 (or higher)

Output Parameter
Flow Rate lb/min 20.0

Manifold Pressure Required (Absolute)
Input Flow Rate 19.98333333
Gas Constant - R 639.6
Intake Manifold Temperature Degrees F 106
Volumetric Efficiency 0.97 Use 0.95 to 0.99 for modern four-valve heads
Engine RPM - N 7500
Engine Displacement (Vd) Liters 1.6 Muliplied by 61.02 in final formula to convert to cubic in.

Output Parameter
Manifold Pressure (Absolute) PSI 20.4

Boost Pressure Required
Input Manifold Pressure (Absolute) PSI 20.4
Atmospheric Pressure PSI 14.7

Output Boost Pressure Required (gauge) PSI 5.7

So, Ray, you are absolutely right and I do believe your numbers are correct. I therefore retract all of the bad things I said about you; you have my sincere apologies.

On the other hand you've more than completely proved the value of a good and thoughtful analysis for helping spec a turbo charger. And while this might be completely unimportant to you, me, the brain, and everyone else who has completed their first turbo motor build, there are lots of folks who come on line and ask, "which turbo should I pick and how should I pick it".

I think the best answer to this question is study the books, study Garrett's website, run a calculation or two of your own, and then come on over to the site and ask what results others have had with similar goals to yours. Obviously, and as you've just proven, the closer the variables are to real life the closer your results will be to real life.

In my case, and because I didn't want any unreasonable expectations for my own system, I repeatedly chose conservative input parameters. This gave me a conservative view of output that was below what was reasonable for a carefully designed and built motor. For my purposes that was fine; but it did cause me to not fully understand what your motor was capable of.

But hey, it was great fun and I learned a lot from a bunch of folks. Hopefully there are others who learned as well.

Regards,

Jim

I'd say it's impressive if not amazing at a 10.5-11 afr. I'd figure that near rich for three times the boost on good pump gas. :dunno:

any more pics of your setup?