Dyno testing setup

[acracker]

How do most of you set up your engines on a dyno? Shaft coupling, chain drive?
Also what corrections do you do in regards to the primary ratio and transmission gear choice?
I am looking into making a inertial dyno that could be used for testing off the output shaft or power at the wheels with some modification. Has anyone else tried something similar?
Thanks for your help.

[Nathan T]

We have a DynoJet chassis dyno that works great for a complete car. We built an adapter that uses a motorcycle wheel and a steel frame that bolts to the dyno frame and allows us to do development testing of the engine before we have a complete chassis and drivtrain. I can email a photo if you want to see it.

Nathan
USC engine team lead

[vinHonda]

Nathan,

Just wondering how much the entire set-up cost you, where u store it, how happy the faculty are with it?

Thanks,

Vinh

University of Toronto Formula SAE Racing Team
www.fsae.utoronto.ca (http://www.fsae.utoronto.ca)

[Sam Zimmerman]

We use a flexible shaft coupling at our transmission output to connect our absorber. We then correct our cuves to be "accurate" at the crank. Our dyno is not an inertial dyno, so I can't help you there.

Sam Zimmerman
Vandals Racing (http://www.uidaho.edu/~racing)

[B Lewis @ PE Engine Management]

We've got a couple of waterbrake dynos and engine stands that we can use with different engine configurations. We have had good luck using u-joints and short driveshafts as the connecting parts. As far as corrections for shaft output, we just use the gear ratio as the only correction for torque without worrying about efficiency through the gears.

Brian Lewis
Performance Electronics, Ltd.
www.pe-ltd.com (http://www.pe-ltd.com)
"Complete Engine Management Systems for $798"

[Nathan T]

Vinh,
The chassis dyno that we have was purchased by the team in '97 so I don't know exactly how much that cost, but I think around 12k. The motorcycle wheel adapter that I made cost less than $100 and took about 2 nights to build. It just consists of a square tube frame that the engine bolts to and a chain drive to a motorcycle wheel. I've heard of other teams making similar things from a chopped up motorcycle. We use two bolts to hold it onto one side of the chassis dyno and then use some ratcheting straps to hold the rear end down onto the roller. It is all self contained with fuel tank, radiator etc. so it can be unbolted and lifted off the dyno in one piece if we need to dyno a car.
As far as the faculty goes, our advisor is pretty hands off so he probably hasn't ever seen it. It has a chain and wheel gaurds so it is safe to operate.

Nathan Theiss
http://www-scf.usc.edu/~scracer/

[Bam Bam]

On this topic any body made an effort at building their own proper eddy current or motoring dyno instead of using this ghetto inertial stuff.

I figure all you'd need is a big electric motor absorber or generator, (not even that big in our case) something to cool it, an encoder or speed sensor, A little bit of PID speed control, a strain gauge, a tach and your off to the races. Most of this stuff short of the motor is probably kicking around your shop as we speak.
Any ideas on where to pick up a cheap absorber/motor. (think outside the engine dyno industry or we're talking MASSIVE coin)

[Charlie]

We have a Dynojet, and it is great for back-to-back testing and the like. But inertia dynos suck for engine mapping. Almost useless. When we had to map last year we went back to our 1982 senior project water brake dyno, it is definitely a ghetto setup but it does the job just fine. http://fsae.com/groupee_common/emoticons/icon_smile.gif

EDIT: TO answer the original question, we use a short driveshaft from the output sprocket. We calculate torque by gear multiplication only, not taking inertia into account. After all, we are close to steady state, and a dyno is a yardstick for improvement moreso than trying to get exact numbers.

-Charlie Ping
Auburn University FSAE (http://eng.auburn.edu/organizations/SAE/AUFSAE)
5th Overall Detroit 2003
? Overall Aussie 2003. http://fsae.com/groupee_common/emoticons/icon_smile.gif

[This message was edited by Charlie on November 11, 2003 at 02:50 PM.]

[bigtoyota9]

We have always used an old water break dyno through a short shaft, and have good success with it. The only complaint i would have is applying the load is a little tricky since the dyno is meant for much larger engines. But you can get the hang of it after a while.

[Jon Prevost]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Bam Bam:
On this topic any body made an effort at building their own proper eddy current or motoring dyno instead of using this ghetto inertial stuff.

I figure all you'd need is a big electric motor absorber or generator, (not even that big in our case) something to cool it, an encoder or speed sensor, A little bit of PID speed control, a strain gauge, a tach and your off to the races. Most of this stuff short of the motor is probably kicking around your shop as we speak.
Any ideas on where to pick up a cheap absorber/motor. (think outside the engine dyno industry or we're talking MASSIVE coin)<HR></BLOCKQUOTE>
http://www.formulabuckeyes.com/images/36/images/dyno_jpg.jpg

, Jon
"Success - it 's what
you do with what you've got." - Woody Hayes
Engine Team

[PatClarke]

Jon,
What about the eddy current brake unit used in the driveline of some Greyhound type coaches, and in some big trucks? Should be available as a scrap component?
PDR

Rudeness is a weak mans imitation of strength

[Jon Prevost]

Try it out but don't spend too much time on it unless you're looking at a 2 year project. I must say that a water brake properly sized is VERY good. The only difference is that the dc dyno can start, motor, and hold engine speeds no matter what the TPS position http://fsae.com/groupee_common/emoticons/icon_smile.gif . It's really helpful for fine tuning, you just pick the engine speed and load with the digital throttle controller, tune, save http://fsae.com/groupee_common/emoticons/icon_smile.gif . We use LabView to capture EGT, diy wideband, all sensors, torque, dyno speed, you name it. It's one of the best in the country and it's getting torn down http://fsae.com/groupee_common/emoticons/icon_frown.gif . Building a new ME building in place of the old one, this dyno goes in storage for a few years.
We have an eddy current dyno in our C.A.R. center. It's pretty small but I don't know what's involved.

, Jon
"Success - it 's what
you do with what you've got." - Woody Hayes
Engine Team

[Bam Bam]

Jon,
Why do I get the feeling that sucker wasn't made by one of your team members....(see my note about MASSIVE COIN)

Can you program a course and shift points into that bad boy?

I've worked with a lot of eddy's and their so sweet to use and pretty dumb easy when you get down to it I'm suprised no-one has built one from one of the telma brakes on a truck or bus as suddenlee was saying.

[Jon Prevost]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Bam Bam:
Jon,
Why do I get the feeling that sucker wasn't made by one of your team members....(see my note about MASSIVE COIN)

Can you program a course and shift points into that bad boy?

I've worked with a lot of eddy's and their so sweet to use and pretty dumb easy when you get down to it I'm suprised no-one has built one from one of the telma brakes on a truck or bus as suddenlee was saying.<HR></BLOCKQUOTE>
It wasn't made by our team but it was setup by us. Obviously the cost is high but that's why you need to always be doing sponsorship.
We haven't had the time to sit down and program a course into it but as of right now we have rpm histograms of track times from TRC so we're close. All that needs to be done now is to right a program in either VB or LabView to control our throttle. The digital throttle control has a book on how to program it and control it through a PC but no time.
I'm working on a self tuning alogorithm that uses EGTs and the wideband to self tune. It'll be sweet but I won't spend any more time on it until we find a spot for our dyno.
The eddy's look pretty good, only problem is you can't motor an engine with one, only measure.

, Jon
"Success - it 's what
you do with what you've got." - Woody Hayes
Engine Team

[Bam Bam]

Self tuning, Good Project, you'll learn a lot and it can certainly be done, but I can't really understand your motivation to do it.

There's too many safeties and details to worry about, like what happens when one of your exhuast thermocouples drops out (which it probably will or what do you do to detect/prevent knock. Knock sensors are pretty good but a little resonance in your driveline will make em think your engines running pretty angry.

Unless your ECU is crap and doesn't allow real time access to your calibration maps, it doesn't take much time to map out the fuel and spark for peak power.

Oh yeah for all you guys worried about how to detect knock, there are some stethoscopes you can buy at most autoparts stores.

Just put the tip o that bad boy on the block and listen to your babies heart beat as you dial up the spark. Its probably one of the coolest things you'll ever hear. If your exhaust is open to the room, you might have to rig up something to plug your ears better to avoid going deaf. But it is the only way I've been able to detect knock with any degree of confidence. If your really against technology use a block of wood on the engine block and put the other end of it to your ear. (and no I'm not just saying this to make you look like a moron, you will look like a moron, but you might save your engine)

and for you lost souls who don't know what knock sounds like take a hammer and tap the block. Yeah just like that, that's the sound you don't want to hear. Either that or advance your timing to about 70 degrees that should do it for you guys who just like to break stuff.

Technology is a beautiful thing but there's a whole lot to be said for a trained set of eyes and ears. For example you can Use EGT's to figure out a misfiring cylinder or you can lick your fingers and touch the exhaust very quickly.

As for a motoring dyno, They're nice I've used em, but they are pretty much superfluous for our applications. The only time you need to motor it is on the extremely low loads where the engine is not producing any torque. In real life this will only occur under decels where you don't really care all that much what the engine is doing. I guess you could calibrate some decel fuel cut-off and do well at fuel economy, but I always think that's a sissy boy's category anyway and has no place in a race car competition (Just limit the tank size and call her a day). After watching you guys do burnouts last year I figure your not spending much time in the Sissy boy category.

Also, too much fuel cut will hurt you with a lean spike on the following accel. This is why I was asking about course maps. you could figure out the optimal transient fueling to account for wall wetting which should give you a huge advantage out of the turns and make your car very driveable so I take it back, the motor would be real handy if you used it properly (HINT).

However if your using an eddy, running a little rich on the decels by extracting your map straight down w/o interpolating will keep your transient fueling pretty good and have your car nice and jumpy out of the turns but will hurt you in sissy boy points.

With a motor you could also measure things like friction torque differences with different piston rings, but all this stuff would come out as an increase in torque on any dyno,

Anyways I've divulged enough info, I don't want anyone thinking I have any intelligence so I'll return to my regular scheduled denegrating comments.

Later

[ben]

We have a small water brake dyno connected to the engine by a short shaft with a hookes joint at each end and a sliding spline in the middle.

We leave the sprocket on the engine and have a rubber/metal coupling that grips around the outside and prevents any severe shock loads from getting through.

We've then got a small 'control panel' with fuel and ignition pots, fuse box, etc.

Ben

University of Birmingham
www.ubracing.co.uk (http://www.ubracing.co.uk)

[Jon Prevost]

bam bam, you're right on. The motivation isn't really there for the self tune like you said. The best part about having a motored dyno is holding an rpm. The other nice part is having the digital throttle controller also hooked up for holding a load. It's something you have to experience if you haven't already.
The auto tune wouldn't be hard. Last week we were tuning our old F4 "Aries" with an unrestricted intake on stock F4i throttle bodies. The system is running on alpha-n because of time and the obvious. We started with an engine speed and low throttle opening. Then increased the throttle opening while tuning AFR, then back down and tune ignition for peak torque before fall off (not enough timing). Tuned for an AFR of 13.8, remember to disable decel FCO or you'll wonder why the AFR goes lean so quick http://fsae.com/groupee_common/emoticons/icon_wink.gif .
In about a 5 hour span we had started the dyno and tuned from 2000rpm to 8800rpm across the WHOLE tps map. Fuel and spark was done. Then we had computer problems and it ended our evening.
The advantage of a motored dyno is time. It'll save a LOT of time.

, Jon
"Success - it 's what
you do with what you've got." - Woody Hayes
Engine Team