Engine Dyno Vs Wheel Dyno - Which Is Ultimately Best? - MR2 Owners Club Message Board
 
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post #1 of 11 (permalink) Old July 23rd, 2015, 14:55 Thread Starter
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Engine Dyno Vs Chassis Dyno - Which Is Ultimately Best?

Guys,

So I've been thinking about my new engine setup and getting the best tune possible.. It will be a very complex setup and needs to get done right. In my case I need 5 tunes and a few adjustments for my high compression, dry sump, meth, NOS powered 5S-GE.

I need to tune my EMS for the following:
* 93 pump gas tune which wont be for max performance
* E85 which will be for performance and MPG in cruse since it will be my primary fuel.
* E85 with meth (I don't care to debate this its getting done anyway) for additional power
* E85 with NOS
* E85 for meth and NOS

The AEM infinity is my choice because its more than capable for handling all i need to get this done.

Ill also need to tune vacuum on mt 6 stage dry sump and adjust oil pressure to ensure no cavitation issues at 10,000 RPM since that's what i'm building this engine to handle.

I started looking into engine dynos which can cost up to 1000-1200 for a 10 hour session and that includes tuning your EMS for optimum performance. So all i need to worry about is getting my engine, intake system, meth system and etc there and spend a full day with the guys discussing whats best.

My problem with a wheel dyno is the tuner, most tuners will come close to getting the optimum performance and hand you your car back. but on a engine dyno, you can load each and every cell and get a complete full tune as if it were a OEM ECU. the other thing is that paying a tuner for a wheel dyno session could cost 350-700 depending on your situation/setup.

My concerns:

What happens when I place the engine in my car, will it not perform well based on transmission loss?

Will I need another dyno session once I put the engine in the car for small adjustments?

your thoughts on which is best?

Project 5S-GE: 180WHP/140LBS 2.2L Stroker NA On E85 (More WHP On The Way!):
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N/A Guys tune/replace and modify the items that are allegedly good till 700+WHP?
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Last edited by eazy2001x; July 24th, 2015 at 14:20. Reason: correction
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post #2 of 11 (permalink) Old July 24th, 2015, 14:20 Thread Starter
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Just found this..

http://www.onallcylinders.com/2012/0...u-should-know/

Quote:
Originally Posted by www.onallcylinders.com
So you just A) bought a high performance engine; B) bolted some go-fast parts on your existing engine, or C) built a brand new engine. Now you’re chomping at the bit wondering how much power you’ll have under your right foot.

There are three basic methods for measuring engine output: testing on an engine dyno, running a vehicle on a chassis dyno, or making passes at a race track. Each will provide valuable information, but the method you choose depends on what exactly you want to know about your engine’s performance.

This post will describe the first two methods since they are the most directly measurable, repeatable, and are conducted under (relatively) controlled conditions. While elapsed time and mile-per-hour results from the track are good indicators of performance, track testing can be influenced by too many variables (track conditions, weather, suspension settings, driver skill, etc.) to be a truly reliable measure of engine output.

Engine Dyno Basics
An engine dyno calculates power output directly by measuring the force (torque) required to hold a spinning engine at a set speed (rpm). The dyno software then calculates horsepower based on the torque figure and engine rpm (horsepower equals torque times engine speed, divided by 5,252).

The dyno has a control board that shows readouts of torque, rpm, water temperature, oil temperature and pressure, exhaust temperature, and air/fuel ratio (from an O2 sensor) via sensors connected to the engine. The dyno operator can start and run the engine from the board via a cable-operated lever or electronically, depending on the dyno. The engine itself is usually stripped of its accessory drive (most dynos use an electric water pump and perhaps an alternator for testing) and is fitted with headers and, depending on what the customer wants, a full exhaust system.

Since it measures torque directly, an engine dyno gives you the most accurate picture of how much power your engine makes. As such, an engine dyno is the most accurate way of doing parts comparisons (cylinder head vs. cylinder head, for example) or fine-tuning an engine to extract maximum power. Other advantages of engine dynos include easy access to the engine for swapping parts and tuning, repeatability, and (usually) well-controlled testing conditions.

Chassis Dyno Basics
Where an engine dyno measures power directly from the engine, a chassis dyno measures engine output—or more accurately, drivetrain output—at a vehicle’s drive wheels. In its basic form, a chassis dyno consists of a platform with a pair of drums or rollers, a braking or power absorption system, and software to calculate power output.

The test vehicle is positioned on the dyno with its drive wheels on the drums or rollers. Depending on the dyno type, the software calculates torque output based on how fast the vehicle accelerates the drum (inertia style dyno, like a Dynojet) or via a load cell that measures power absorbed by the rollers (eddy current dyno like a Mustang Dyno unit). Horsepower is calculated from the torque value. Most chassis dynos have the capability to monitor air/fuel ratios (via an O2 sensor in the exhaust) and other engine parameters.

The chassis dynamometer’s claim to fame is the ability to measure power at the drive wheels—the “real world” performance of a vehicle. You can make tuning changes and test parts to find out the effects on power, just as you would with an engine dyno (though not as easily). And since there are standard factors for engine power losses through the drivetrain (15-17 percent for manual transmissions and 20-25 percent for automatics are figures accepted by most tuners), a chassis dyno can give you a good idea of how efficient your drivetrain is.

Which Dyno Do I Use?
So which dyno is better? The answer, of course, is it depends. If you want to break in and tune a new engine, compare the effects of different parts on power, or extract maximum power from a current engine combo, the engine dyno is the way to go. Because it measures “true” engine torque, monitors a wide array of engine functions, and tests under controlled conditions, an engine dyno provides very accurate and repeatable results.

Determining the overall performance of a vehicle’s drivetrain is where the chassis dyno really shines—after all, the power at the drive wheels is what ultimately moves your vehicle down the road or around the track. Perhaps the biggest draw of a chassis dyno is that you don’t have the time and hassle of yanking the motor out—just drive up on the platform, make some runs, then drive home with some power printouts in your hand.

The thing to keep in mind about a chassis dyno is that it really isn’t designed to measure true, or flywheel, engine output. You have to determine the amount of engine power consumed by the drivetrain and add that to the drive wheel power figure. While there are generally accepted loss percentages for manual and automatic transmission-equipped drivetrains, they are really only estimates. Add in the fact that drivetrain losses can vary from one run to the next, and things like tire temperature and pressure also affect final results, and you can see a chassis dyno is much better suited as a vehicle tuning tool than an engine horsepower measurement tool.

Consistency is Key
No matter which type of dyno you use, you need to understand that consistency is the key to accurate results. A typical dyno test session consists of multiple pulls (engine dyno) or runs (chassis dyno), not to mention numerous adjustments and wholesale parts changes. To make the results valid, testing conditions—temperature, humidity, dyno type, operator, and procedures—need to be as consistent as possible.

Ventilation is also critical, especially for chassis dynos. Poor ventilation allows exhaust gasses to contaminate the intake air charge—not good for power or repeatability. Make sure the shop that you are using has adequate ventilation, or wait several minutes between pulls for the exhaust gas to disperse. Any deviations in testing conditions can impact the results and leave you with the wrong impression of what your engine or vehicle is truly capable of.

One final note on dyno testing: shop carefully for a qualified dyno operator. Just because someone buys a dyno and hangs a sign that says “Dyno Tuner” doesn’t make them an expert. Ask around and find out which shops people use, then pay a visit to see how they operate. Going on a day when a test session is scheduled is ideal; you can get a good feel for a dyno operator’s tuning skills, customer service, and things like shop cleanliness and organization. After all, it’s your hard-earned money—and your prized possession—that you’re putting in someone else’s hands.

Project 5S-GE: 180WHP/140LBS 2.2L Stroker NA On E85 (More WHP On The Way!):
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N/A Guys tune/replace and modify the items that are allegedly good till 700+WHP?
Quotes: deviantv1ral *5sge master* Medpilot *MR2 god*
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post #3 of 11 (permalink) Old August 7th, 2015, 21:48
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Given what you are trying to do and the multitude of configurations you want to try i would think an engine dyno would be a good way to go. You will be better able to monitor anything "unsafe" and address any issue on the engine more easily without it being installed in the car. Weird noises are guaranteed to be from the engine, and nothing else.

Your timing curve should not have to change going into the chassis much, but your loading likely will be different and it would be wise to check it in the car on a chassis dyno afterwards. I would then check at least both your "every day" tune and your highest power/most likely to blow up tune.

Just my opinion.


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Last edited by Loki; August 8th, 2015 at 18:22. Reason: spelling error found
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post #4 of 11 (permalink) Old August 7th, 2015, 22:14 Thread Starter
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I am leaning towards ur thought process..

Project 5S-GE: 180WHP/140LBS 2.2L Stroker NA On E85 (More WHP On The Way!):
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N/A Guys tune/replace and modify the items that are allegedly good till 700+WHP?
Quotes: deviantv1ral *5sge master* Medpilot *MR2 god*
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post #5 of 11 (permalink) Old September 6th, 2015, 20:43
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Loki's plan makes the most sense for the incremental changes you want to isolate.
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post #6 of 11 (permalink) Old September 7th, 2015, 08:59 Thread Starter
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I agree and will go that route.. Hopefully the engine dyno can be loaded to hit all 20x20 of my map for a perfect tune that wont have to be changed much at all..

Project 5S-GE: 180WHP/140LBS 2.2L Stroker NA On E85 (More WHP On The Way!):
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N/A Guys tune/replace and modify the items that are allegedly good till 700+WHP?
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post #7 of 11 (permalink) Old September 8th, 2015, 04:46
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The big advantage of an engine dyno is that they are usually surrounded by quality instrumentation/logging gear.

So if your manifold has ports for EGT per cylinder, backpressure, and/or wideband per cylinder or cylinder head temp probes etc and the engine dyno is offering those then sure go for it. A hub dyno will allow you to reach just as much of the map as an engine dyno will.

If you haven't made allowances for using extra sensors etc then I really don't see any benefits to an engine dyno, apart from easy access to adjust and fix leaks etc. Is that worth the hassle/cost?
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post #8 of 11 (permalink) Old September 16th, 2015, 17:23
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Quote:
Originally Posted by eazy2001x View Post
I agree and will go that route.. Hopefully the engine dyno can be loaded to hit all 20x20 of my map for a perfect tune that wont have to be changed much at all..
You will never hit *every* cell, lol. No WOT at zero rpm for example.


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post #9 of 11 (permalink) Old September 17th, 2015, 08:18 Thread Starter
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Granted.. There are some areas in vacuum that wont be touched.. However.. I have a dry sump setup and I'm a na.. My last engine saw positive pressure after reaching more than 100% be so I am sure that I can hit all cells at wot.. I've done it before logging.. Now for vacuum I can adjust the regulator on my engine to hit the upper cells to find my max vacuum and the. Adjust my map in order to start row 1 in that range and row 20 at 0psi thus being able to hit all cells. And before you denounce more that 100% ve on a na.. Research scavenging effect and na engines reaching more than 100.

Project 5S-GE: 180WHP/140LBS 2.2L Stroker NA On E85 (More WHP On The Way!):
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N/A Guys tune/replace and modify the items that are allegedly good till 700+WHP?
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post #10 of 11 (permalink) Old September 17th, 2015, 14:41
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You're confusing a MAP sensor reading with VE. They aren't the same thing.
And a positive pressure in the intake manifold just means you are sampling the peaks, not the average. Average plenum pressure can't go over atmospheric.
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post #11 of 11 (permalink) Old September 17th, 2015, 14:58 Thread Starter
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not really confusing them.. and you are right to an extent.. but there is a possibility that the scavenging effect create greater vacuum on closed vales before they open thus pulling out the exhaust gasses vs having them pushed out. this is where more than 100% VE can be achieved. I know that positive pressure cant happen inside the manifold and that a NA is only dealing with atmospheric. I might be having a hard time conveying my information to you guys and confusing you but my thought process is there.
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