disturbedfan121

iTrader: (5)

th OP's post of 229.7hp seems about right just based on other number from simliar cars, now i know each car is in itself a variable but still comparatively speaking its right.

now for Ray_Sir_6's car making 20+hp than everyone else's car with the same setup, and actually better setup's too is what i can't believe is correct.

ray_sir_6

iTrader: (1)

It's perfectly do-able.

Why does it need to calculate for drivetrain losses? It's gives WHEEL HORSEPOWER readings! The actual power going to the WHEELS. If you want to know flywheel hp, pull the motor and put it on an engine dyno. It's not corrected for FHP, and it never is.

So I guess the laws of physics don't add up, cause people dyno their cars, then goto the drag strip and run a ET and MPH that states they should be making this much hp/lb, and it is normally pretty damn close to what a Dynojet will read.

Did someone dump a can of stupid in your coffee this morning? You can not HOPE to come up with a spreadsheet from some info on Garrett's website and determine how much whp a engine will make. Unless you work at MIT in your off time, which I doubt.

Start filling out that elaborate formula you copied from some website and start filling it in. Post it here, with exact entries and how you determined them. I am curious what you determined was the VE of a 1.8l motor, vs a 1.6l, plus what fuel you used, and the chemical properties of it (they do use additives nowadays).

Let me know when you want me to bring my motor by so you can tear it apart and weigh and measure EVERY PART, plus flow test it all, and install the turbo speed sensor, plus the dozen+ temperature sensors you will need to get accurate temperature readings...remember, you need one pre-turbo, post-turbo, pre-IC, post-IC, pre TB, post TB, IM Manifold, one for each runner, one for each cylinder port, one for each combustion chamber, one for each exhaust runner, pre-turbo hotside, post-turbo. This is just the beginning, but if any one of these hundreds of THOUSANDS of variables is off, so will your calculation.

OK, now that we know that your "simple" calculation is far from adequate, we'll just have to rely on the small error that dynos allow, cause it is alot easier and faster.

Wow, I am soo glad we have dynos!!

ray_sir_6

iTrader: (1)

Who has a better setup? It's called a good tune on a good standalone. Just like that "torque drop at 6200rpm" that someone said was missing...duh...you tune it out. That's what standalones do. It's amazing what someone who knows how to tune can do when they are using a great ECU.

Thucydides

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.

patsmx5

iTrader: (16)

Wow, for once I'm gonna have to side with ray sir 6 on something..

Turbo's run off the exhaust. They put a restriction on the exhaust. The more restriction, the less total amount of air going in the motor. For example (OMG ray sir 6 will die cause I'm using overly simplified math and inferior compression ratios and it's all probably wrong), if there was a restriction that let no air through the exhaust, you would make no HP. If there was no restriction, you would make a hole lot of HP. But since turbo's run by placing a turbine in the exhaust that presents a restriction as a means to convert various forms of energy into mechanical energy, varying the size of said restriction does change HP numbers for a given PSI of boost. That is, boost is actually a function of restriction.

Thucydides

The simple answer is that Mazda reported their crank horsepower, and you can be damn certain that they made their measurements accurately. And so when someone says they doubled the fuel and air, and got 30 percent more than double the horsepower reported by Mazda, there's a bust somewhere.

But let me give you an opening, Ray, because you haven't really come up with any on your own. There's a difference between SAE, DIN, and any number of other ways of measuring and reporting engine output. Take the hint and run with it; it's might actually be a legitimate reason why my argument isn't entirely valid. You'll actually have to do some reading to see what those differences are, and whether they can explain why your and my numbers disagree so much, but it's a start. There are undoubtedly other flaws, but neither you nor I have found them yet.

Really? Here you're confusing your abilities with mine. Have you looked over their website and checked their calculations? They provide two practical examples of how to use their turbo efficiency charts to choose the right turbo and to calculate expected horsepower outputs. I used one of their examples to check my work, though they also made two errors in their calculations which we won't discuss unless you insist; and besides, they're really quite easy to find. And no, I'm a retired farrier.

Here is my spread sheet proof of their calculations:

Airflow Required
Input Parameter Units Value Notes
H.P. Target 400
Air/Fuel Ratio 12
Brake Specific Fuel Consumption lb/(H.P.*hr) 0.55 Use 0.5 to 0.6 (or higher)

Output Parameter
Flow Rate lb/min 44.0

Manifold Pressure Required (Absolute)
Input Flow Rate 44
Gas Constant - R 639.6
Intake Manifold Temperature Degrees F 130
Volumetric Efficiency 0.92 Use 0.95 to 0.99 for modern four-valve heads
Engine RPM - N 7200
Engine Displacement (Vd) Liters 2 Muliplied by 61.02 in final formula to convert to cubic in.

Output Parameter
Manifold Pressure (Absolute) PSI 41.1

Boost Pressure Required
Input Manifold Pressure (Absolute) PSI 41.1
Atmospheric Pressure PSI 14.7

Output Boost Pressure Required (gauge) PSI 26.4

Pressure Losses
Input Manifold Pressure (Absolute) PSI 41.1
Estimated loss Comp. to Manifold PSI 2 Use 1 to 4 psi (very efficient to fairly restrictive)

Output Compressor Discharge Pressure PSI 43.1

Input Pressure loss before Compressor PSI 1 Use 1 to 2 psi (very efficient to fairly restrictive)
Atmospheric Pressure PSI 14.7

Output Compresser Inlet Pressure PSI 13.7

Output Pressure Ratio between Discharge and Inlet 3.14

Data for Use with Turbo Charts - Maximum HP Data Point

Pressure Ratio between Discharge and Inlet 3.14

Flow Rate lbs/min 44.0

Alternate R.P.M. Data for Use with Turbo Chargs
Background Values
H.P. Target 400
Boost Pressure Required PSI 26.4

Input New Engine R.P.M. 5000
Input Volumetric Efficiency % 0.98
Input Manifold Pressure (Absolute) PSI 41.1 Note - example mistakenly uses 43.1
Input Engine Displacement (Vd) Liters 2
Input Intake Manifold Temperature Degrees F 130
Input Gas Constant - R 639.6

Output Flow Rate at new rpm value lbs/min 32.5

Those who take the time to read through Garrett's "Tech 103" link will recognize the example and the results.

You know, we can go on like this forever, Ray, and I'll have a better answer for everything you present than you do for my arguments, but it's pretty clear you won't recognize the value of simple calculations because you can't appreciate or understand their strengths and limitations; I suspect you also have the same appreciation for dyno's for exactly the same reasons.

But here's the difference between you and I, Ray. I understand completely perfectly well just what variables are concerned both with simple calculations, complex calculations, and dynometers, and how much each of those variables can can degrade the results. Some variables are critical, some are relatively unimportant, and some can be ignored. The folks who designed the Dynojet did exactly this when they decided where to cut corners and where not to cut corners. They paid great attention to the critical stuff, compromised on the relatively unimportant, and ignored others. No dynometer is a perfect system, and neither is a calculation.

In the vernacular, I know just how fucked up my calculations are, and how fucked up your dyno numbers are. But I understand that, and therein lies the difference.

Thucydides

Don't worry pat, I half *** covered that earlier:

"I already understand that depending on the volume delivery either of those turbos might be in a more efficient range and have a lower temperature, so one or the other might generate different horsepower values, but we're talking extreme cases not a comparison of two well chosen and designed turbo systems."

I should have expanded that to include extremes of exhaust efficiency. Nobody's building 300 hp turbos with 1" exhaust systems. We assume that everybody who expects good results will build a system designed to deliver maximum performance. The calculations don't assume stupidity on the part of builder, but I suppose that's another variable I shouldn't have left out.

And certainly, the builder who's got an exhaust system which matches his engine output will get better results than the owner who ran out of budget and kept his exhaust system stock. But then my calculations assume 95% volumetric efficiency throughout the system (except for my simplified calculation which assumes 100% and gives about 5% higher HP figures), and so proper equipment is a given. But the reality is that this probably over estimates the output of a turbo engine for the reasons you stated earlier, though I'm not certain one way or the other.

patsmx5

iTrader: (16)

Thucydides, ray sir 6 has a very unusual way of looking at things, including compression ratios. Conservation of energy says one thing, ray sir 6 says another. He insist he's right, and two motors he's seen "prove it", but the math just doesn't add up. So I pretty much give up trying to reason with people that refuse to consider something rational. If you have any doubt, look into the "FI and compression ratios" thread in the performance forum.

I will say this though: Your number from post 28 are not correct. That is, your assumptions are wrong. You say his initial HP is 116. What you neglect is that that's the stock engine. I guarantee you if he were to tie the wastegate open and dyno the car with no boost, it's gonna make more than 116 flywheel HP. Why? Cause of all the **** he's done to increase the power his motor makes. See where this is going?

Thucydides

Golly gee, I can't wait. But first, another Valium.

I see what you're thinking, Pat, but I've assumed a very high volumetric efficiency for his motor (95% for Garrett's calc's, and 100% for my simplified calc's) and so I'm not sure he's gotten beyond those figures. But it's possible. Anyway, glad you're hanging tough. I'll be the first to admit it's a long and fairly pedantic argument I've made.

And besides, what would I know? Six months ago I'd never driven a Miata, and three months ago I didn't know you could turbo charge them. Never though about a turbo until two months or so ago, and I've never been to a dyno. And my worst offense of all is I've never (intentionally) driven my wife's own turbo car in boost (Joe told me not to). So by all means, and this goes for everybody BUT RAY, read every and anything I write with great suspicion, though I'd never let anyone use these facts against me in an argument.

Jim

Gcat

I just want to make sure I have this correct.

With your overly simplified math, you are stating that

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

So we will say we have a gt32 @ 15lbs with a 1.6 = ((15+14.7)/14.7))*116 = 234 HP

Also lets say we have a GT42R @ 15lbs with the same formula on the same engine, even though you would probably never spool the sucker lol..I'll amuse you. Well look at that you are making the same HP. 234 HP.

You are stating that they will both make the same HP b/c of some HUGE restriction between the throttle body, manifolds, head, cylinder volume, exhaust, etc etc. While math and science can take you pretty far, experience using both usually takes you farther.

Your math= the fail, no matter how you look at it.

YOUR math states that if the OP changed his turbo to a gt35r @ the same PSI he would still make the same HP. I just want to make sure that is what you are stating and I didn't overlook your "simplified" math lol

UrbanSoot

iTrader: (24)

i vote ban!

Gcat

Ban for what? lol I dont think anyone in this thread, no matter how new or old they may be is really out of line one way or the other.

UrbanSoot

iTrader: (24)

nah.. i was just joking. other then that, ive seen a whole bunch of dyno plots of miatas do similar numbers at similar boost with similar setups.

m2cupcar

iTrader: (5)

It would definitely be interesting to see ray's car on the same dyno with some other cars from the forum.

Thucydides

Well, you'd have to look waaaaay far back to see that I realize the difference between different turbos making different hp at the same boost because of difference in efficiencies, and as a result, in compressor outlet temperatures. But in your case, and assuming your hypothetical GT42R could spool, you'd be running into efficiency problems on the left side of the chart, generating more heat than the 32, and making less HP. Didn't see that coming, did ja.

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.

Breaking news! Hold presses!

Braineack

iTrader: (62)

I made 230rwhp at 13psi....at only 6K to boot. Can't call BS on this dyno....Certified annually by Miataturbo.net.

I'd argue drivetrain loss is more like a static 25rwhp, no 17%.

Thucydides

So would I.

Thucydides

Wonderful. Are we talking 1.6 liter or 1.8 liter?

For a 1.6 liter at 13 psi you'd expect to make around 220; with a 1.8 liter at the same boost you'd expect to make closer to 240. But isn't is interesting to see that in less time than it takes to type this I predicted your engine's power within 5%. Not bad, considering I haven't yet finished my first cup of coffee. So common, man up and admit you can predict turbo power with an abacus.

And when you say 229rwhp, are you saying uncorrected or corrected. What correction factor did they use and what variables (barametric, driveline, etc.) are "corrected"?

I think you guys are not standardizing your standard corrections, and in fact I'll bet most of you don't have a clue what correction factor is being used. Is it 1.01 or is it 1.15? Big difference; I have thought you'd be more interested in this.

But here's how to look at this. If you're going to build a car from scratch, and let's say you're not familiar with that engine but need to spec a turbo. You're not going to slap on a dozen different turbos to see what works best; are you?

You'll check out Garrett's site, run the numbers, and narrow the choice to two. If you can beg, borrow, or steal those turbos you'll try them both out. If you're like most of us you'll ask at a place like this which one is best. The point is crunching the numbers is a worthwhile and economical approach to narrowing the field.

Now, if I had installed my turbo, and wanted to fine tune it, or see what differences I might get with different intakes or exhaust systems, I'd put it on a dyno. But I'd ask for raw numbers and make my own corrections, thereby eliminating the biggest variable of all; the BS factor.

Braineack

iTrader: (62)

you can see in my sig I have a 1.6L. You can also clearly see the numbers were uncorrected.

Here's the SAE corrected plot:



same motor, same turbo, same manifold, same boost (more or less)....

lets see, the 190rwhp run was 0.95 CF, and the 219 run was also .95 CF


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:



&

plot 2:





I find this funny.

Thucydides

Hmmmm. That's interesting. So your saying a Miata's driveline losses are 25 hp at 800 rpms and 7500 rpms, and the same whether you're generating 5 hp or 585 hp. Interesting.

I'll tell you why they're not. Friction isn't a constant, it's a variable that changes semi-linearly with stress. And secondly, heat, the product of friction and pressure, varies linearly with power input. So there's no way driveline loss is static. It's also not linear, but for our purposes something between 15 and 20 percent is probably close enough; I split the difference.