12.5 psi 1.6 230rwhp
 

I finally "finished" my miata. Thank you to all the guys here who have really gone out of their way to help a total stranger. Especially to Brain for doing so much for my MS piggyback. I have owned this car for six and a half years and it is finally bad ass. I have no regrets having to sell my 94 rx7, I might not have gotten this far on the miata.

The dyno is crappy (and not steady state :mad:) but we have used it on a variety of cars and it gives a decent number. It gave my downpipe only 45K mile perfect running extremely well maintained FD rx7 197whp which is probably about 15 less than other similar cars.

I went from the dyno to the 1/8 mile dragstrip and ran a 8.7 with bouncing off the rev limiter in first gear. I am not quite used to the new power. The stock vsld hasn't exploded yet after 8K turbo miles and over a hundred launches at the strip, many with BF drag radials. I am going to drain the fluid again soon and do some chunk checking.

At 12.5 psi: (I was at 208whp at 10psi.)


Attachment 210839

Cody from www.lovefab.com (recently hit a raccoon with my new lip at 85mph on the way to the dragstrip :crx:)

Attachment 210840

nice man....very nice

lucky friggin ms owners...how I envy you

Post your slip from the 1/8 mile. Nice numbers.

Will do, need to figure out my scanner at work tomorrow. Those damn students need to just leave me alone. Annoying adolescences. Just ask a smart kid. :hustler:

you're bigger turbo and .5lbs of boost beats my hp by 10 exactly

The turbo was new, $500, and sitting on the shelf. Otherwise, I would have chosen yours for spool.

Tune is very conservative, I insisted because I don't like change. Change of the inside my engine kind.

Conservative? I am running a smaller turbo and making 190whp at 5.5psi. I am still tuned very conservatively as well. The more I see outputs from MS cars, the less I like it.

can i see the dyno chart for that? i'm gonna have to call bs. is your motor fully built?

what motor? 1.6? 94-97 1.8?99-00 1.8? or 01+?

wow on 5.5psi? holy shit, id love to see that too

Or the more dyno plots you see.. you'll wake up and realize they don't read exactly the same.

You sound like FM and how the Hydra can provide a gazillion more HP just by swapping from the Link to it.

The MS is extremely capable... and I'll use it a thousand times before an AEM due to the cost. Just not worth going to such an expensive EMS. (yah yah, go ahead and cry again about the MS fanboys and blah blah this and blah blah that)

nice man nice

Oh, and the car was heat soaked and is running a smooth flowing but quiet 2.25 inch exhaust. (which I thought was a 2.5 inch for a while, but I am still happy with it)

I am unable to scan the timeslip, the software just errors when I push the scan button.

60 ft 1.921
1/8 8.771
mph 77.799

This dragstrip is really low quality. There is an EVO that has a best of 8.9 and an 08 Mustang GT that runs 9.3 with a good launch. But its $5. And its local. I still think my mph should be higher, but I don't power shift.

Attachment 210835

This is on an American Iron certified dyno, with standard (lowest reading) correction factor.
Stock 1.6l motor.
Running wastegate on the Greddy kit.

I already had it posted up here in it's own thread.

You are right, they don't read the same. Alot of the dynos out there let you fudge the numbers by adjusting conditions to change the calculated hp. Those are the ones that can't get certified for use in the American Iron Series.

I don't have any experience with Hydra, so I'm not gonna bring it in to this discussion.

http://www.google.com/products?q=AEM+30-1710&scoring=p

You can get a AEM EMS for about $1600 shipped. A MS PnP is $720, that's a difference of $880. That doesn't seem like much of a difference when you are talking about building a car. I'm not gonna waste my time trying to argue MS vs AEM, since I can't prove my point without using dyno plots from customers. I don't even know if I could do it that way, since the only direct comparision I have is between the Haltec E11v2 and a MS on 2 basicly identical 280ZX Turbos. I can say that there really is no comparision between them, cause it wasn't even close.

i....never seen a greddy perform so well before. If you said 7-8psi I'd believe you...5.5psi is pretty hard to believe, what boost level was the 146rwhp run at? no boost ;) How did you even run less than 5.5psi without the spool suffering from the wastegate being opened slightly at idle?

Granted I made 170rwhp at 6psi, probably more power ot be had with a better exhaust and spark, but i dunno about another 20.

exactly what i was thinking brain.

I dont doubt the car pulled 190rwhp. i just doubt the boost level it happened at. looks like more than one helper spring was used too...doesn't have the dreaded torque drop after 5.2K like every other greddy setup...

smae here, i believe the car made 190, but not at 5.5psi

it must be the texas air given him the extra ponies

The one where I made 146whp was at 7psi the same day we installed the FMIC. That was with all my band-aids and the stock ECU. I remember being told it was running .45BAR, which is actually 6.5psi. I don't have access to the logs, so I'll find out later if that was correct.

No helper springs.

We are actually gonna play with the cam gears and see if we can get 200whp. They haven't been touched yet.

Yeah, that must be it. :)

Fantastic numbers!! :D

OP nice numbers, how do you like the turbo? How is spool?

I have a crappy map at 6psi. Lets run them and see the differance. I'm going to laugh if my crappy map and MS leaves your car in the dust.

Sounds good to me. I haven't had any fun with my car yet.

It would be awesome if you guys posted up logs of the runs along with the results of AEM vs MS.

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).

I'll call Hustler and see if he knows how to post my logs. I'm just running wastegate too. I have a used clutch in the garage. Mabe I can get it in this week and run 8psi as well.

I'm calling bullshit on all of it, from top to bottom.

For example, the OP says he's making "12.5 psi 1.6 230rwhp". Now, does this really pass the common sense test. Let's try it and see...

230rwh * 1.17 = 269 crank hp.

12.5 psi + 14.7 psi (atmospheric pressure) = 27.2 psi absolute pressure.

Now let's say a NA 1.6 liter Miata makes 116 crank hp at 13.7 psi absolute pressure. The 1 psi below atmospheric is to account for losses within the intake system, and neglects any gains in either the intake or exhaust for pressure waves. In other words, it's a reasonably conservative assumption.

Now with the OP's 27.2 psi (12.5 psi boost) one would expect an increase of:

(27.2 psi / 13.7 psi) * 116 hp = 230.3 hp. Again, this would be a generous figure unless significant other improvements were made which would boost the volumetric factor beyond the 95% already assumed. So where does the extra 39 hp, which is a 17% increase, come from? I'll tell you where it comes from - marketing.

Let's try this again with the 190 hp example at 5.5 psi....

190rwh * 1.17 = 222 crank hp.

5.5 psi + 14.7 psi (atmospheric pressure) = 20.2 psi absolute pressure.

Now with the OP's 20.2 psi (5.5 psi boost) one would expect an increase of:

(20.2 psi / 13.7 psi) * 116 hp = 171.3 crank hp.

So again, where does the 51 hp, an even more incredible 30% increase come from?

Elesjuan said it best when he said, "Fantastic numbers!!", though I'm not sure he and I are using fantastic in the same way.

I don't give a shit what kind of exhaust system you hang on there, or what kind of turbo's pumping your air, the horsepower you generate is essentially directly related to the amount of air and fuel that's pumped through your motor, and it doesn't take a brain gardener to run the simple calc's necessary to know if your dyno tech is blowing smoke up your ass to ensure you're happy with your mods and come back to him the next time you change something.

The Brain said something to the effect that determining the level of boost needed, on paper, is nearly impossible and never correct. You might want to rethink that Brain. I'm beginning to think that determination the level of horsepower produced by any amount of boost using a BS dyno is nearly impossible and never correct. Case in point above.

Well, I guess the HP and percentage gain claims are no worse than those made for fuel aligning magnets, vortex spinners, and fuel-air bubblers; it's just that those mods are relatively cheap. It's unfortunate that a development tool as valuable as a dyno is commonly "corrected" in a manner that makes it essentially useless to serious tuners unless they are in on the secret.

i dont know... i think its very possible with 2860

Care to explain exactly how?

And more explicitly, at a given temperature how is 5.5 psi boost from a GT2554R different than 5.5 psi boost from 2860?

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.

is this a gt2860rs or a gt2860?

Does it matter?

yes

I really like how you simplified it where you don't have to include air flow, air temp, or exhaust restrictions in your equations. Gotta love people who think math is the answer to everything, yet can't include all the variables to account for what actually makes power in an engine. There is a reason they don't have an ACCURATE "Turbo Power Calculator" for you to download online. Cause it is NEVER that simple.

Dynojets don't squew the numbers. You have to seriously try to get it to do a wrong correction, like have the temp/barometer sensor in a seperate area, so that you can control what temp/humidy, etc, it reads that could be changed to make the calculation different. Some shops do that, and that's why they are not certified by American Iron as an authorized dyno location. Where I work we are one of 2 in the DFW area that IS certified. They do random inspections and have a car that they take around to make sure they read the same on the 2 different dynos. I also WORK THERE, so he isn't trying to make me buy more, cause I pay cost, that's it. Also, if you look at the dynosheet, it says "Correction: STD" which is the LOWEST correction factor. Lots of dynos read different, but a Dynojet reads the same as another Dynojet. I took my last car to 2 shops, I got IDENTICAL figures from our dyno and ATS Racing's dyno. Both are Dynojets.

PSI doesn't means shit, AIR FLOW is what matters. A GT28 will FLOW MORE AIR at the same psi than a GT25.

http://www.turbobygarrett.com/turbob...1_3_comp_e.gif

http://www.turbobygarrett.com/turbob...0-5_comp_e.gif

of course it matters. You have someone like savington running 14+psi on a gt2554 making less power than someone like y8s who's only running 9.5 psi on a GT2876R

I simplified the equation to make it accessible to the greatest number of people. Besides, the basic premise of my argument doesn't change when you include air temp, exhaust restrictions, etc. For my own understanding I use Garrett's approach which includes the following variables:

air/fuel ratio,
brake specific fuel consumption,
intake manifold temperature,
volumetric efficiency,
engine rpms,
engine displacement,
pressure loss before the compressor, and
pressure loss between the compressor and intake plenum

Here's what it looks like for your 1.6 liter 269 hp motor motor:

Airflow Required
Input Parameter Units Value Notes
H.P. Target 269
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 29.6

Manifold Pressure Required (Absolute)
Input Flow Rate 29.59
Gas Constant - R 639.6
Intake Manifold Temperature Degrees F 130
Volumetric Efficiency 0.95 Use 0.95 to 0.99 for modern four-valve heads
Engine RPM - N 6750
Engine Displacement (Vd) Liters 1.6 Muliplied by 61.02 in final formula to convert to cubic in.

Output Parameter
Manifold Pressure (Absolute) PSI 35.7

Boost Pressure Required
Input Manifold Pressure (Absolute) PSI 35.7
Atmospheric Pressure PSI 14.7

Output Boost Pressure Required (gauge) PSI 21.0

Pressure Losses
Input Manifold Pressure (Absolute) PSI 35.7
Estimated loss Comp. to Manifold PSI 2.5 Use 1 to 4 psi (very efficient to fairly restrictive)

Output Compressor Discharge Pressure PSI 38.2

Input Pressure loss before Compressor PSI 1.5 Use 1 to 2 psi (very efficient to fairly restrictive)
Atmospheric Pressure PSI 14.7

Output Compresser Inlet Pressure PSI 13.2

Output Pressure Ratio between Discharge and Inlet 2.89

Maximum B.H.P. Data for Use with Turbo Charts

Pressure Ratio between Discharge and Inlet 2.89

Flow Rate lbs/min 29.6

Alternate R.P.M. Data for Use with Turbo Chargs
Background Values
H.P. Target 269
Boost Pressure Required PSI 21.0

Input New Engine R.P.M. 6750
Input Volumetric Efficiency % 0.95
Input Manifold Pressure (Absolute) PSI 35.7
Input Engine Displacement (Vd) Liters 1.6
Input Intake Manifold Temperature Degrees F 130
Input Gas Constant - R 639.6

Output Flow Rate at new rpm value lbs/min 29.6


Do you think that including those parameters would have 1) improved the explanation, or 2) changed the result.

I can't answer the first for you, but I did check the second and the answer is no. A back of the envelope calculation and Garrett's calculation yield essentially the same result. Do you think for one moment that the folks at Garrett don't understand how their turbo chargers generate power in their customers motors? Think they might have left out any magic variables and lost 30% of their customers horse power; power you found in a Dynojet?

I specifically used a back of the envelop approach (I was one told by a very smart fellow that if you can't explain a concept on the back of an envelope you don't understand what it is you're trying to explain, and neither will any one else) so that folks like you can point to a fault in my approach and say, ah ha!, there's the problem. Feel free to do so and ad whatever other variables you think necessary to prove your point. Complicated math doesn't mean it's better (E=MC^2), it often means it's merely less understandable. I could have made it even simpler, but then even your average 5th grader could have understood it and then where's the mystery?

Oh shit, I can't help myself:

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

Let's see how it compares with Garrett's analysis of the 21 psi boost 269 hp 1.6 liter motor:

((21+14.7)/14.7)*116 = 282. Damn, it's off by 4.7%

Sure it's going to be off 4% or 5% (the price for not having 10,000 variables), but heck, that's way better than your megabucks dynojet.

Simply amazing! So two Dynojet's, which came from the same company, were built by the same workers, from the same parts, operated in a similar matter, and using the same principals for measuring engine output, produce identical results. That doesn't mean either is accurate. And don't make me explain the difference between precision and accuracy, because that would take another fucking hour.

"Correction: STD"; just what the fuck does that mean? Just some variable they put in but don't bother to explain or quantify. Yeah, why would you want to know what their correction factor was anyhow? "It's our standard correction; it will make your car look good." Sure, let them put whatever the hell correction they want to in there as long as it's "STD" and the numbers look good. Wait, I want the LTD correction, or perhaps the HYPER correction; no I think I'll take the MEGA HYPER LTD correction with extra CHUCK NORRIS punching power.

Yeah, and a GT42R will flow 4x what a 28 will. Airflow doesn't mean shit if it's not related to pressure. They're completely and irrevocably related. Look at the efficiency charts and tell me you can eliminate the pressure axis. For any given motor, and any given rpms, and any given power generated, the airflow required can only be delivered at the pressure required. You can accurately determine both with relatively simple calculations, or you can spend megabucks and measure it. But there's no dancing around it; pressure and airflow are directly related. Let me illustrate: I've got a big room fan that moves tremendous volume, but do you think it will make a good turbocharger?

Erm, why wouldn't the OP's car make 230 RWHP at 12.5 psi? My little greddy made 247 at 14 psi. Sounds perfectly believable to me.

I think the reason is that the demand is small and while making an Excel spreadsheet to do Garrett's calc's for you is easy (it took about 15 minutes), making it down-loadable isn't.

But let me make one thing perfectly clear. I'm not at all down on dynometers in general, or Dynojet's in particular. What bothers me is they won't simply tell you what they've measured; they always "correct" the results. The problem is that their correction factor may not accurately reflect the drive line differences in say a 4 cylinder stick shift Miata and a 7.5 liter diesel automatic pickup. The financial pressure is to make big numbers; nobody wants to know that their stock Miata only makes 85 hp on the dyno. They want to see 116, or with an air kit and exhaust, 130.

"Ah sir, your miata makes 85 hp at the rear wheels"
"I thought it was supposed to make 116".
"Actually sir, your's isn't bad, I've seen plenty of 70 hp miatas out there"
"You charged me $175 to tell me my miata makes less than the factory says it does; fuck you I'm never coming back".

next customer:

"What's my miata making"
"Just one moment sir while I install the STD correction"
"Yep, it's 136 hp."
"Wow! I was only expecting 130"
"Sir, that will be $175"
"Thanks! I'll see you in a week after I've installed my Chuck Norris turbulatior".
"See you next week".

So they tell you what you expect, because that's easier than explaining why. This is how I ended up with a dumb oil pressure gauge on my '95; not because it was necessarily cheaper to install, but because it saved on calls to the dealer from worried owners.

"My oil pressure gauge is always moving; why can't it make up it's mind? I've had it to the dealer sixteen times and they always tell me the same thing".
"What's that sir".
"That they're supposed to do that. Can you make it stop?"
"Don't worry sir, we're working on a fucks, I mean a fix, now. It will be coming out in our '95 models".

I dunno Kotomile; perhaps horses aren't as powerful today as they were when I was shoeing them back in the Civil War days.

But really, the reason is that when the OP says he made 230 rwhp it means about 269 at the crank, and the numbers simply don't add up. The math is simple because the concepts are simple. There's no more to it than that.

I suspect what is happening is that there's confusion between rear wheel and crank horsepower, and that the dyno guys are muddying the water by reading one and reporting the other.

Have you ever gone to a Mustang Dyno, and then to another shop with the exact same dyno? They WON'T read the same. Cause the inputs that it uses to make the corrections are user inputted or adjustable. Dynojets are fixed, and unless you tamper with the sensors, are not user-adjustable. That makes them consistent and repeatable, hence why they are the standard.

12psi on a GT25 is not the same as 12psi on a GT28. Why? Cause one FLOWS MORE AIR. 10psi on a waterhose won't get you near the water you would get on 10psi from a fire hose. Yeah, you still get 10psi worth of water, but when your house is on fire, I bet you want the one that flows more. How can you not understand AIR FLOW and still want to be involved in this thread?

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

10-15% off? Maybe if you are running a GT25 or a GT28, but running a GT35, it's not gonna be even close.

http://www.turbobygarrett.com/turbob...8_1_comp_e.gif

The best way to determine the hp a turbo will support is to use the airflow. Where it says 30lb/min it will support approx. 300hp. So if you are running 18psi (2.25Bar if you want to look on the chart) you will make approx. 300hp. Using your formula, I can make 630hp on a Evo that makes 280hp stock. Only 330hp too much. It was a good try, but it failed soo hard.

I love how you bash dynos, when even your expanded formula wouldn't be as accurate as a properly used dyno. Dyno's don't inflate the numbers, the people playing with them do. That's what makes Dynojets the standard, they use as little manual inputs as possible to keep them from getting incorrect numbers. They have formulas that WORK on dynos, cause they aren't trying to calculate for all the different parameters of internal combustion, they are only determining how much hp it takes to create current from spinning a know weight. Same thing an engine dyno does, but it hooks to the flywheel. Or we can just keep using your formulas to try and determine an estimate without knowing all the variables. We can always tear the motor apart and measure it, send the head off for flow testing, along with the the turbo, manifolds, TB, etc. Even then you can't 100% determine the output of the motor, cause there are far too many variables , IE VE, weight, oil used, etc. You can go thru all that, and you'll spend way more time and money to get within 3% of what the Dynojet dyno will show.

STD - Standard Correction. That means it does the least amount of adjustments possible to the output. This is the one I use cause it is ALWAYS the lowest reading. SAE would add about 3-5whp, which is a formula that meets the requirements of the SAE. The numbers by Garrett are only the amount of airflow the turbo makes at a certain psi. It doesn't determine what the engine hp will be. That is done by the engine and the tune itself.

Please go read a book or something. Get educated on what you are talking about before you reply. It will save me alot of time having to correct it.

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.

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!!

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. :bang:

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? Fuck those Evo's and their lame ass 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.

Wow, for once I'm gonna have to side with ray sir 6 on something.:eek5:.

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.

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.

Don't worry pat, I half ass 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.

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 shit he's done to increase the power his motor makes. See where this is going?

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

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

i vote ban!

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.

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.

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

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!

http://www.boostedmiata.com/dynos/229rwhp.jpg

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%.

So would I.

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.

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:

http://www.boostedmiata.com/dynos/dy...foreafter1.jpg

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:

http://www.boostedmiata.com/dyno_day.../plots/y8s.jpg

&

plot 2:

http://www.boostedmiata.com/dyno_day.../airbrush1.jpg



I find this funny.

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.