Leslie 928 S2

Question.....what is the most popular dyno machine for dynoing a 928? Same question for other vehicle types...


Not just for wide open horsepower, but for low and mid range tuning also. Please discuss.




Thanks!

RicerSchnitzzle

I think going to the same dyno time after time is more important. With differences in calibration or correction factors you can get just about any result the operator want's you to have.

SMTCapeCod

See Ref:A, the 'boom boom' thread

IcemanG17

I would guess that dynojets are the most common..... but what really matters is finding a dyno local to you that you can use as a baseline for all your mods....that way its always tested on the same dyno by the same shop etc......

dr bob

The inertia dynos like Dynojet are out if you need steady load and RPM's for engine tuning. You need a brake dyno, something with a generator on the end. See how bright you can make the lights go in the neighborhood.

hacker-pschorr

The Dynojet we use is the 424x - with eddie current brakes for loading.

Leslie 928 S2

No, seriously! I wasn't drinking at all last night, I promise!

It's a real question, with a real ulterior motive...

Thanks for all your input so far. So it sounds like a Dynojet would be adequate for accuracy and tuning in your collective opinions? We've been on a Dynojet ourselves, of course, but we just wondered if it was considered to be a popular format or not...

mark kibort

Rolling dynos like the 248e is best for just seeing what your car will do vs others. you either accelerate the known rollers or you dont. I havent seen any difference in the output at all, and SAE can change based on operator set up and equip. actual is actual. not much you can do there to cheat! drums are a certain size, weight etc. sensors have no error. Math is the same. you either accelerate the drums at a rate or you dont. the only variables are tie down, but Ive played with that and havent seen much of a diff there.

Mk

Tom. M

If you are just looking to get baseline and document increases as you add them, then choose whatever one is closest to you....If you want bragging rights in the 928 community, then find a dynojet since most numbers posted out there are from dynojets... Not saying its the better dyno..but for now the most used. And (to Mark K's chagrin), get them corrected to SAE so they are comparable across the board. They may not be "true" time/place/temp/pressure..but the goal is to compare across the board on an equal plain.

edit to above post..make sure the pressure and temp sensors are properly placed..so they "can't " cheat as much

Tom. M

Well..if you want to compare the results to anyone else's then you'll have to wait till they get their "actual results" on a day of the same temp/pressure etc... I would consider those "variable" ...

Leslie 928 S2

And what is the proper placement of those sensors?

Tom. M

Good question...I'm sure Louie and Porken can write volumes on how/where to place them. They just have to be inidicative of the environment in which the car is being tested....if it's inside a shop with the doors closed..then they shouldn't be outside in the rain etc....

OBehave

The Porsche Challenge rules state that cars competing in that series have to be dyno tested on a Dynjet model 224 or 248 and must be within 3hp of their specific HP classification.Seems like the Dynojet must be a decent machine.The Eddy current option is a plus for real world driveability tuning and trouble shooting.

Leslie 928 S2

So that's the one you like, Ed? Sounds like you've been thinking about it some.

dr bob

Leslie/Kevin--

The classic Dynojet, the one with the big roller where acceleration of the known-mass drum, is an inertia dyno. It's meant for full-throttle pulls from off-idle to redline. The horsepower is calculated by how fast you accelerate the drum.

Meanwhile, to do serious on-the-dyno tuning, you'll want a dyno with a brake attached to it. Some have eddy-current brakes, a fancy name for a generator that shunts generated current to a resistive load and allows you to adjust the amount of load applied to the motor at a constant RPM. The idea is that you can tweak and tune the ignition and fuel mapping at a specific engine speed until you get it right, then move on to the next speed and tune there. This is the kind I'd be lloking for to do tuning. If you are just looking for bragging rights, the more common inertia dyno will be fine.