12.5 psi 1.6 230rwhp
09-30-2008, 10:36 AM
#61
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.
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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09-30-2008, 10:53 AM
#63
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).
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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09-30-2008, 10:54 AM
#64
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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09-30-2008, 10:55 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
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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09-30-2008, 11:00 AM
#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.
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.
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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09-30-2008, 11:01 AM
#68
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.
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.
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09-30-2008, 11:03 AM
#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).
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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09-30-2008, 11:17 AM
#76
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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).
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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09-30-2008, 12:00 PM
#77
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.
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.
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.
Here I agree with you, if the dyno's properly designed, built, and operated.
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.
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.
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09-30-2008, 01:02 PM
#78
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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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09-30-2008, 01:26 PM
#79
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.
So the math says my dyno is right.
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.
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).
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09-30-2008, 01:50 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?
can you send me the .drf file of your runs so i can compare?
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