What Specs Does The Dyno Guy Need Before Getting On The Rollers?
 

I'm planning on attending the Dyno day/get together on the 20th and was trying to find out what the operator needs in the way of specs to put into the system. I believe it's a Dyno Dynamics unit. My car has the 6spd, but I swapped the 3.9 out to the 3.63. So is 4th or 5th the correct gear? Besides curb weight, tire/wheel size, what else will he need?
Thanks,
-JB

Typically you want to run the car in the 1:1 gear -- on the 6-speed that's 5th. A roller dyno can calculate the gearing if it's got a spark pickup, so you may not need to enter it or tire size. I have no idea why the dyno guy would care what the car weighs unless it's in danger of breaking his dyno.

Oh, he also needs to know what's wrong with this picture:

https://www.miataturbo.net/attachmen...ine=1380871075

--Ian

He'll calibrate wheel speed with RPM for gearing.

Tell him 5th gear and the RPM you want it revved to, they'll do the rest.

I didn't know the weight of the car didn't matter. Speedometer is way off with the 3.63. I'll try a gearing calculater site for more info.

That doesnt matter, the dyno knows how fast it is going.

Dann

Car should be strapped down pretty damn tight. Most dyno failures you'll see on youtube come from failed straps.

For that little extra power, have your laptop hooked up (if it's not already), and have him go to your preferred red line by looking at tunerstudio's tach, which I believe is slightly more accurate and reads slightly higher. It's your motor though.

Thanks Dan.
Just for grins I found the Flyin' Miata gearing calculator.

Flyin' Miata : Technical info : Gearing calculator

Lets see... if I revved to 9500 rpm I can do 179.3 in fifth.:rofl:....:bowrofl:......:facepalm:

Thanks Josh, good to know. (and remember to datalog)

I'm pretty happy with the fueling and timing maps, but since I get 3 pulls within about 30 mins I was thinking about some ways to use the time to try a couple of easy things. Maybe a different spark plug to compare to the NGK's? Also I working on a mod to streamline the air after the TB on the 99-00 manifold. Something closer to the square top design. It wouldn't take long to swap the tops and I have an extra top half laying here.

If you've never dyno'd, you want to mess with timing.

For your first run, don't change anything verify your fuel map is making good AFR's, in the mid to high 11's in boost.

For your second run, decrease timing in the boost cells by 2-3*. You should see a healthy drop in peak power.

If you didn't: spend your third run decreasing timing again by 1-2*. If you still don't see a drop in power, pay for more time and drop your timing by a degree until you loose power and stay there.

If you did: spend your third run increasing 1-2* ABOVE run #2's timing. Ideally you want to go until your torque and power curves start to smooth and level out (you should gain less and less power). Once you stop gaining power, back it off 1-3* for safety and be happy with your extra powers.

This method gained me 16hp and 14ft/lbs at my peak, but my max gain at slightly lower rpms was 20hp and 17ft/lbs. I had unlimited runs within an hour though.

Also for this method, I'm assuming you don't have a knock sensor. If you do, there's no need to decrease timing, just increase until you stop gaining power or detect knock. You don't want to go up in timing without a knock sensor in case you're already above MBT, each run will just get you closer to explosions.

I have 3 tunes cued up to run for my 3 runs. Gonna run my daily tune to see where I'm at. Then run my aggressive tune. Then for the 3rd run I'll adjust if need be.

Not really needing to tune I think, just wanna see where I'm at and get 3 nice logs.

Thanks for the advice.
Apparently, I'm one of the old guys on here also at 56. (I've been told it's good to act your shoe size once in a while)

this.

And here I was thinking I'd be one of the "old guys" there at the ripe old age of 34.

Say for instance from the first run, you traverse your timing table something like this:
https://www.miataturbo.net/attachmen...1&d=1380910135

Would you subtract a flat 3 degrees from every cell at or above 3k rpms that the run goes through, and check the HP output from there?
So if you lose a small amount power from say 5k rpms then you know your timing was too advanced there and the 3 degrees brought it back to safe numbers.
If you lose a lot by the subtraction at 4k rpms then you know you were probably at MBT at 4k rpms?

Keep in mind I've only done this a handful of times, so don't take my word to be exact, but the theory is sound from what I've read here.

I pay attention to peak numbers, not 4k vs. 5k. Your drawn red line looks typical for a dyno run, I would select all the cells starting at 3000rpm and 103 map and up. Anything above 3000 and BELOW 103 is getting towards your cruising cells, where I've found (mainly from pictures of Braineack's timing table) you want ~38* for gas mileage.

Once you've selected that upper right 7x8 corner of your timing table, tap the down arrow twice (twenty times for MSII and MSIII folk). If you loose significant peak power (5-10hp), you were probably BELOW MBT, and you can go 1-2* above your previous numbers. If you don't change much (0-2hp) you were probably ABOVE MBT, and you should keep going down.

Using your peak timing number at 7400rpm and 202.6map of 15(.4)* pictured above, let's pretend it made 150hp.

if 13*=140hp, then try 17.

if 13*=149hp, then try 11.

Hope that makes sense.

Side note: please dyno with more boosts. You've drawn a line at 10psi. Boo.

Thanks Curly, that makes perfect sense. I guess if you had infinite time to do infinite runs you could worry about the various RPMs. But the peak power strategy seems like a good one if you're paying for dyno time by the hour.


Fair enough, I just hand-drew where I usually see my existing street tune goes through. :) One day I'll get a dyno tune and up the boost a lil more.

How experienced is this guy and his shop?

From what I understand very, mostly Honda platforms, owns and races his own stuff. Been around for years. Since this is my first time on a dyno I was just trying to be as prepared as I could. I just figured there were plenty of people here who have been there done that. Correct me if I'm missing something here but it sounds like one of the important things is to know what speed/rpm I have in 5th since I'm now using the 3.63 in the rear.

Not at all as long as u dont over spin the dyno. You dont want to end up at 190 mph or something nuts on tires not made for those speeds.

Its quite simple how the gearing works really. The dyno doesnt care about what gearing you have or the tires or any of that combo as long as you/the dyno dude connects the 1st spark plug indicator.

Wait i'm curious now, what do people do about it with cops?