12.5 psi 1.6 230rwhp - Page 4 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 09-30-2008, 11:36 AM   #61
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Originally Posted by Thucydides View Post
At the same inlet temperature and pressure any given motor will make the same hp. That's a simple mass flow problem. What folks are failing to realize, and apparently you are too, is that the primary difference in why one turbo will make more or less hp at a given boost is inlet temperature; it's a very significant factor. You use a bigger turbo (within reason) to lower intake temperature at higher flows and pressures.
WRONG WRONG WRONG WRONG WRONG!!!!!!!!!!!!!!!!

That's what you are missing. Boost is a function of restriction. Bigger turbo's have a less restrictive turbine and more volume of air for a given PSI. Boost is a measure of restriction, not a measure of total flow. Stop posting and read up my friend.
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Old 09-30-2008, 11:41 AM   #62
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Thucydides doesn't wants to play my guess the boost level game?
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Old 09-30-2008, 11:53 AM   #63
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Drivetrain losses do go up almost linearly with HP. This is not B.S, this is fact. IE, you might have 17% drivetrain losses at a RPM X and 200 flyhweel HP, so you are at 166whp and you lost 34HP to drivetrain losses.

If you double your power to 400 flywheel HP at X RPM, you don't just subtract 34HP. Not hardly. Fact is the losses are pretty much linear. It might be 16% or it might be 18%, but it's still a percentage. Frictonal losses are proportional to the forces causing them (IE, two gears rubbing against each other).
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Old 09-30-2008, 11:54 AM   #64
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So would I.
Dyno day? I could swing that. Saturday is the norm for them, but I am sure I could work it in during the week if that was needed. I've already wasted enough time trying to discuss this over, so lets let the cars do the real world proving. When it's over and I have proved what I said, we can all have a good laugh. Hell, might be able to get Brice to use some of his tuning skill to try and clean up a few of the DIY tunes so MS doesn't look so bad.
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Old 09-30-2008, 11:55 AM   #65
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This has been very interesting, funny, and enlightening. I've definately learned quite a bit, and I've got a greater appreciation for what dyno's (good dyno's) can do.

I still believe some of claims out there should be questioned, but I was also off on my own calculations and suspected as such. I mentioned that to Ray when I pointed out there's a difference between SAE and DIN hp measurements; I've not definitively nailed that down but at one site I saw the number of 15% as the difference. If that's the case, and I correct for the way Mazda reports their hp ratings to the way U.S. dynometers report their ratings, most of the differences flat out disappear.

Brain, when I run my slightly less simple numbers for your 1.6 (the ones which take into account intake losses) at 13 psi I get 234 hp. Now of course you're reporting RWHP so I'd add 17% and get 274 crank hp.

Similarly, if I took the 234 hp calculated crank hp, and adjusted it for the different rating systems, I'd add say 15% and get 269 hp, for a difference of 1.8%. As little interested as you are in math I know you understand 1.8% isn't that much Brain. Frankly, I'm amazed things are that close. I'd have been satisfied to have been within 10%, but who am I to complain when things are better than I'd expected.

Anyway, I've got to leave for work otherwise I'd check into things and tighten things up a bit. For those who have the time or inclination there's a good article here:

http://en.wikipedia.org/wiki/Horsepower

Regards,

Jim
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Old 09-30-2008, 11:56 AM   #66
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Thucydides doesn't wants to play my guess the boost level game?
Those are dyno graphs...they are NEVER right.
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Old 09-30-2008, 12:00 PM   #67
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WRONG WRONG WRONG WRONG WRONG!!!!!!!!!!!!!!!!

That's what you are missing. Boost is a function of restriction. Bigger turbo's have a less restrictive turbine and more volume of air for a given PSI. Boost is a measure of restriction, not a measure of total flow. Stop posting and read up my friend.
Yep, you're absolutely right. There are two components to turbos, the compressor and turbine, and they both influence efficiency and power.

But keep thinking about it Pat because you're only partially correct and I've given you that part above. The part about a given pressure/temperature in the intake manifold still holds true. The fuel and air available to burn and make hp is the same given the same conditions at the intake. There was a discussion about this some days ago; go have a look and see if you still hold your position. What I didn't mention, and that you've pointed out, is that losses after the exhaust valve opens also plays an important part.

No need for me to stop posting and read up so long as you're keeping an eye on things.

But for the rest of you, are Pat I the only ones here who can see both sides of the issue? Do I not only have to explain your mistakes, but mine as well. I'm way too easy on you guys.
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Old 09-30-2008, 12:01 PM   #68
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Brain, when I run my slightly less simple numbers for your 1.6 (the ones which take into account intake losses) at 13 psi I get 234 hp. Now of course you're reporting RWHP so I'd add 17% and get 274 crank hp.

Similarly, if I took the 234 hp calculated crank hp, and adjusted it for the different rating systems, I'd add say 15% and get 269 hp, for a difference of 1.8%. As little interested as you are in math I know you understand 1.8% isn't that much Brain. Frankly, I'm amazed things are that close. I'd have been satisfied to have been within 10%, but who am I to complain when things are better than I'd expected.
Hmmm...you don't even know what kind of diff and tranny fluids he is running. Those change the % of drivetrain loss. I've seen stock SM cars make 6whp from changing to a better fluid. That's on a 120whp car, too. Then they also make more power after the fluid is warm, normally 3-4whp. That's why the SM crowd does 3 pulls before they start making changes, to get the driveline warm.
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Old 09-30-2008, 12:01 PM   #69
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Thucydides doesn't wants to play my guess the boost level game?
I don't mind playing, it's just that my boss expects me to be somewhere. I'll play later.
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Old 09-30-2008, 12:02 PM   #70
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Originally Posted by Thucydides View Post
Brain, when I run my slightly less simple numbers for your 1.6 (the ones which take into account intake losses) at 13 psi I get 234 hp. Now of course you're reporting RWHP so I'd add 17% and get 274 crank hp.

why did I only make 190rwhp at 12psi on the other run shown?
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Old 09-30-2008, 12:02 PM   #71
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Those are dyno graphs...they are NEVER right.
Of course not; manufactures only post them to confuse us.
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Old 09-30-2008, 12:03 PM   #72
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Drivetrain losses do go up almost linearly with HP. This is not B.S, this is fact. IE, you might have 17% drivetrain losses at a RPM X and 200 flyhweel HP, so you are at 166whp and you lost 34HP to drivetrain losses.

If you double your power to 400 flywheel HP at X RPM, you don't just subtract 34HP. Not hardly. Fact is the losses are pretty much linear. It might be 16% or it might be 18%, but it's still a percentage. Frictonal losses are proportional to the forces causing them (IE, two gears rubbing against each other).
Glad you agree with me. I thought this one was obvious also. A freebee from Brain.
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Old 09-30-2008, 12:07 PM   #73
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Of course not; manufactures only post them to confuse us.
All of them in this thread are from individuals, not manufacturers.
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Old 09-30-2008, 12:10 PM   #74
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why did I only make 190rwhp at 12psi on the other run shown?
Because something was fucked up. Right?
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Old 09-30-2008, 12:16 PM   #75
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Because something was fucked up. Right?

nope. ran perfectly well. Unless by fucked up, you of course mean too much back pressure, not an ideal AFR, and less than ideal spark timing.
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Old 09-30-2008, 12:17 PM   #76
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Originally Posted by patsmx5 View Post
Drivetrain losses do go up almost linearly with HP. This is not B.S, this is fact. IE, you might have 17% drivetrain losses at a RPM X and 200 flyhweel HP, so you are at 166whp and you lost 34HP to drivetrain losses.

If you double your power to 400 flywheel HP at X RPM, you don't just subtract 34HP. Not hardly. Fact is the losses are pretty much linear. It might be 16% or it might be 18%, but it's still a percentage. Frictonal losses are proportional to the forces causing them (IE, two gears rubbing against each other).

poor attempt at humor; trying to dig up an old thread where this claim was made before...
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Old 09-30-2008, 01:00 PM   #77
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Ray, how can you not know the difference between compressible and non-compressible fluids, using the properties of one to illustrate the other, and still want to be involved in this thread. But beyond that, Ray, don't you know that flow through an orifice is related to pressure and cross sectional area (plus a bunch of not so unimportant entrance and exit losses), and that the reason a fire hose flows more than a water hose at 10 psi is because it's got a larger orifice. Your intake's throttle plate is a variable orifice, and manifold pressure is measured beyond the plate; figure the rest out on your own.
I thought we were doing "back of an envelope" explaining? I'm still laughing at how your "formula" still has the generic "enter this for a 4v, or this for a 2v" in it. Not much of a formula if you don't even enter the values. That's why I asked to see your formula, the one where you input the numbers, and you can explain where you got the numbers from. Don't let us simple people have to guess the right numbers to input. I want to see your work. I guess we are gonna go down to a 3d grade level now, so you can understand.



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Yup, it's so simple it is funny, though I still don't think I've made it simple enough for you. Let me work on that a bit and I'll get back to you.
The funny part was how it DOESN'T work.

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Ummm, Ray, the y-axis of the chart is pressure ratio, not pressure in bars. Perhaps that's where your confusion comes from, and why your numbers never come out correct. And ray, are you saying an normally aspirated Evo, that makes 280 HP stock, will only gain 20 more HP at 18 psi? **** those Evo's and their lame *** engines.
The pressure ratio is the ratio of the compression of the air from the inlet to the outlet. It starts at 1 cause that is atmosphere pressure (1 BAR), which is what you will see on the inlet side of the turbo. If you compress it .5, that makes it 1.5BAR. The pressure ratio is BAR. I was forced to use 280hp cause your formula doesn't show if it's rated or actual horsepower. That is what they are rated at from the factory, but they actually make 220-230whp on the dyno. At 18 psi they can make only 300whp (yes, that 30 on the bottom is a good indicator of air flow for whp, but, again, all cars are different, it's just a guide) depending on tune and other variables. So it just shows that your simple calculator can be close, but also WAY OFF just depending on the variables. Same as my butt-dyno, but I don't consider that to be a viable way of determining hp.

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Here I agree with you, if the dyno's properly designed, built, and operated.
Guess what, our is.

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I agree here 100 percent also, and this is the primary point of my argument. Not that dyno's are bad, or that they are inherently inaccurate, because they're neither. But don't kid yourself; Garrett either owns or has access to the best engine test equipment available, and that includes dynomoters. The difference between them and your local dyno shop is that Garrett has a vested interested in accuracy; not so much for Joe's dyno's.
Show me where on the Garrett website it has a dyno graph of a Evo9 MR w/ Greddy Easy cams, GT35R, 9:1 Wiseco pistons, flashed ECU, and a 5-spd swap. I'm willing to bet they don't have one. They are just giving a way to get an idea of what the turbo CAN make, not what it WILL make. The only way to know what a setup will make is to take it to a dyno. I have one of those "desktop dynos" on my computer, and they are close, but are only as good as the variables you put it. So, again, let me know when you are read to spec my motor so you can have the right variables.

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So far you've not done a very good job correcting anything. All's I've seen is a basic lack of understanding of even the most simple principals combined with the usual number of stupid errors.
I see the same in your posts. You have yet to give the variables to backup your formula you think is more accurate than a dyno.
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Old 09-30-2008, 02:02 PM   #78
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I'm not very interested because I don't care about math on paper. But since you are playing....how much boost were these two 1.8Ls run at:

Plot 1:
246.52 / 212.45

&

Plot 2:

268.12 / 223.62

I'll play I guess.

Boost power = ((boost + atmospheric)/atmospheric))*stock HP

car in plot 1 made 116rwhp stock.


I believe if i did the algebra correctly, that comes out to 16.5psi?

246 = (x + 14.7 / 14.7) * 116
2.121 = (x + 14.7) / 14.7
31.2 = x + 14.7
16.47 = x

correct?


or how about the hard way...

MAPreq = Wa * R * (460 + Tm) / VE * N/2 * Vd

(30.7 * 639.6 * 560) / (.95 * 3500 * 109.8) *this assumes 100*F in the manifold and 95% VE.

10996003.2 / 365085 = 30.12psia - 14.7 = 15.42psig


or the really simple way...

(new HP / stock HP) -1 x 14.7 = 16.47psi again
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Old 09-30-2008, 02:26 PM   #79
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Did the formulas from Garrett Turbo 103.



HP = 218 flywheel hp
A/F = 11
BSFC = .5

Therefore WA = 19.98 lb/min



WA = 19.98
R = 639.6
Tm = 106 (datalogged)
VE = .97
N = 7500
Vd = 97.632

You come up with 7233031.728 divided by 355136.

That equals 20.3669, but you have to subract atmosphere, which is 14.7

So that equals 5.6669 psi.

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Well, viewed the logs, boost sits between .39 and .43 BAR. So that is approx. 5.7psi to 6.2 psi. That was WG only. We have now hooked up the boost solenoid, and are running .061 BAR (8.8psi).
So the math says my dyno is right.
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Old 09-30-2008, 02:50 PM   #80
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I was looking at two greddy plots I have here, both around 7psi. If they didnt drop boost, everything before 5252RPM looks very close to yours.


can you send me the .drf file of your runs so i can compare?
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