Dyno tips?

[hyperpm]

Getting dyno done this week on a dynojet. Any tips? What gear? DSC off? Fan on intercooler? Thanks in advance.

[NCZ13]

they put a fan on your car anyway.

DSC doesnt matter. your not trying to launch off the damn thing lol.

they will probaby do the run in 4th gear. (we had a dyno day down here, and the speed3s did their runs in 4th)

[Nutari]

Getting dyno done this week on a dynojet. Any tips? What gear? DSC off? Fan on intercooler? Thanks in advance.

4th gear, DSC off.

I had a regular box fan just sitting on the intercooler along with the regular blower fan facing the radiator.


You could do the DSC & traction control off trick too.

with the car off, press and HOLD the DSC button while you start the car. Hold it for at least 3 seconds after the car has started then let it go

both the DSC OFF light and the car with the wavy lines light should be lit up.

[NCZ13]

arent dyno jets inertia dynos? how would DSC have anything to do with the power the car is putting out?

[Nutari]

arent dyno jets inertia dynos? how would DSC have anything to do with the power the car is putting out?

Use the Search.

The ECU limits boost in the lower gears with the DSC on. 99% of people who have done this trick have seen a noticeable difference in boost/power.

[NCZ13]

Use the Search.

The ECU limits boost in the lower gears with the DSC on. 99% of people who have done this trick have seen a noticeable difference in boost/power.

My friend told me that boost is limited in first and second, but i didnt know it was due to the DSC.

but if hes dynoing in 4th it shouldnt make a difference...

but w/e no biggie

[mdavis]

The ECU limits boost in the lower gears with the DSC on. 99% of people who have done this trick have seen a noticeable difference in boost/power.

there is a thread that debates this, im to lazy to search so just do it yourself

[mckraut]

Use the Search.

The ECU limits boost in the lower gears with the DSC on. 99% of people who have done this trick have seen a noticeable difference in boost/power.

You may want to read what you tell other people to search for. Perhaps power is changed due to DSC being off, but not boost. See below.


no diffrence in boost in any of the settings (all on, partial off, and all off) when the wheels are straight. confirmed with dashhawk i dont have the graphs anymore. psi diffrence between settings was negligable.


Ok did a couple more tests today using my DashHawk to capture the data. I did some tests the other day and it appeared that using the method of turning off the DSC/TCS really didn't net any boost. Actually these tests prove that our cars get more boost in 1st and 2nd than previously thought. Here is the outcome of my tests. I plan to do a few more, but I would really like to find a nice spot to do them without fear of Mr. Police Man.

Run 1 - DSC/TSC Off - 1st gear from a stop 8.70 Boost / 27.3 MPH / 5435 RPM -- 2nd Gear 15.95 / 46 / 5593 RPM

Run 2 - DSC/TSC ON - 1st gear from a stop 12.91 Boost / 27.3 MPH / 5627 RPM -- 2nd gear 15.95 / 46.6 / 5691 RPM

I'm not sure if I got the same first gear take off in Run 1 as I did in Run 2 as you can see the RPM's are a little lower, so the 1st run could have easly got up to more boost. Run 2 got a good 1st gear takeoff spinning the tires and turning on/activating TSC due to wheel spin.

Now due to inability to get the exact same runs you can take this information for what it is. Just a comparison using the DSC/TCS hack. To me it seems that on both of my tests (ones today and one the other day but no longer have the data from that one) you actually got a better boost in 1st than you did without TCS and DSC. But overall it seems that using the hack (for lack of a better term) does not really get you any gains and hurts your handling of the car.

My car has MS CAI, Epoxy Mount and I took it in for the updated flash with the latest Voluntary Recall and changed my oil with Royal Purple. These may or may not make my car act differently than others.

[happy and angry]

I'm pretty sure 5th gear is closer to 1:1 than 4th is.

[Darksun280]

take the DCS off if your on stock boost control when the car senses the wheels in the front spinning and the rears no moving it messes things up. This has been confirmed by CP-E as well.

[fragchild]

4th gear hood closed, fan pointed at ducting. 5th is closer 1:1 but my map was all over the place.

[arkenzo]

I'm pretty sure 5th gear is closer to 1:1 than 4th is.

4th for dyno is better.

[happy and angry]

Defend that statement. The goal of a dyno is to get as close to a 1:1 gear ratio to keep the dyno accurate. 5th is closer to 1:1 than 4th is. If the dyno can't handle the speeds at which 5th gear at 6700 rpm will generate, fine. You can't just say "4th for dyno is better" without having a reason for it.

[Moultese]

I dynoed my car in 3rd gear, hood open, took the plastic cover off the IC. But a bag of ice on it before I did my run. Also had my DSC and TC off.

[phillyb]

ic shroud off

[arkenzo]

Defend that statement. The goal of a dyno is to get as close to a 1:1 gear ratio to keep the dyno accurate. 5th is closer to 1:1 than 4th is. If the dyno can't handle the speeds at which 5th gear at 6700 rpm will generate, fine. You can't just say "4th for dyno is better" without having a reason for it.

Without a reason, I just stated that 4th is perfect for dyno. Matt has proven this with his dyno charts as well as other members, I don't recall anyone running 5th for their dyno, besides your dumb ass.(hand)

[happy and angry]

Your statement remains entirely unsubstantiated save anecdotally. I'm starting to get the impression you don't really understand why this isn't very... compelling.

Depending on the way the dyno measures torque, you want to eliminate as much mechanical advantage from the tranny as possible. On dynos where torque is calculated by the rate of acceleration of a weighted drum (like Dynojets, I believe) you can get a run to read artificially high by taking advantage of gearing. This is why everyone suggests you use the gear closest to a 1:1 gear ratio. 4th is 1.171:1, and 5th is 1.085:1. Assuming you understand how ratios work, you'll notice 5th is closer to 1:1.

Now, on dynos that don't measure torque this way, you could conceivably run any gear you want to get accurate numbers, and there would be no issue trying to use a specific gear ratio.

I asked about 1:1 gear ratios because I wanted an informed answer, not your "BECAUSE" answer that tells me nothing beyond that you have strong and possibly misinformed opinions about this subject. If you can bring up anything specific, or some data or numbers or something, awesome. If you know something better about how dynos correct for gearing, or what effect the final drive ratios being different for 1st - 4th and 5th - 6th gears may have on trying to use the gear closest to 1:1, cool. I asked you to defend your statement, and you haven't.

If your only rebuttal is "Hey man I have dyno charts and my claim remains unsubstantiated, but I'll say it again anyway" you can keep it to yourself until someone who actually knows something about this can chime in.

[oaklandopen]

Your statement remains entirely unsubstantiated save anecdotally. I'm starting to get the impression you don't really understand why this isn't very... compelling.

Depending on the way the dyno measures torque, you want to eliminate as much mechanical advantage from the tranny as possible. On dynos where torque is calculated by the rate of acceleration of a weighted drum (like Dynojets, I believe) you can get a run to read artificially high by taking advantage of gearing. This is why everyone suggests you use the gear closest to a 1:1 gear ratio. 4th is 1.171:1, and 5th is 1.085:1. Assuming you understand how ratios work, you'll notice 5th is closer to 1:1.

Now, on dynos that don't measure torque this way, you could conceivably run any gear you want to get accurate numbers, and there would be no issue trying to use a specific gear ratio.

I asked about 1:1 gear ratios because I wanted an informed answer, not your "BECAUSE" answer that tells me nothing beyond that you have strong and possibly misinformed opinions about this subject. If you can bring up anything specific, or some data or numbers or something, awesome. If you know something better about how dynos correct for gearing, or what effect the final drive ratios being different for 1st - 4th and 5th - 6th gears may have on trying to use the gear closest to 1:1, cool. I asked you to defend your statement, and you haven't.

If your only rebuttal is "Hey man I have dyno charts and my claim remains unsubstantiated, but I'll say it again anyway" you can keep it to yourself until someone who actually knows something about this can chime in.

i'll 2nd the statement that 5th is a closer 1:1 than 4th, and i can confirm those ratios you gave cuz i see them on the mazdausa website. so 5th should be a more accurate number.

and besides, hp and tq are changing constantly on a day-to-day, and even minute-by-minute basis in the real world. maps are always changing, weather is always changing, depending on where you live elevation is always changing. so the best you can do is run it a couple times and get an average and use that as a basic guidline. or rip your engine out and put it on an engine dyno, which would probably end up being the most accurate anyway

[Sacrilicious]

our cars are geared differently depending on what gear you're in...our final drive ratio is 3.941 in 1st-4th gears, and 3.350 in 5th-6th gears. use 4th gear because it is the closest to 1:1 of the gears that have the better final drive gearing.

[arkenzo]

our cars are geared differently depending on what gear you're in...our final drive ratio is 3.941 in 1st-4th gears, and 3.350 in 5th-6th gears. use 4th gear because it is the closest to 1:1 of the gears that have the better final drive gearing.

Thank you very much.

[happy and angry]

our cars are geared differently depending on what gear you're in...our final drive ratio is 3.941 in 1st-4th gears, and 3.350 in 5th-6th gears. use 4th gear because it is the closest to 1:1 of the gears that have the better final drive gearing.How does final drive ratio affect a dyno run? I would expect a dyno run in 5th to post similar numbers to a run in 4th, only with numbers a bit lower because of the gearing ratio difference. The final drive ratio just means the 1.171:1 or 1.085:1 ratios apply to a different final drive gearing, but will have the same final ratio of tire revolutions to transmission revolutions, which means the degree of inaccuracy in 4th on an inertial dyno would remain the same.

[Sacrilicious]

How does final drive ratio affect a dyno run? I would expect a dyno run in 5th to post similar numbers to a run in 4th, only with numbers a bit lower because of the gearing ratio difference. The final drive ratio just means the 1.171:1 or 1.085:1 ratios apply to a different final drive gearing, but will have the same final ratio of tire revolutions to transmission revolutions, which means the degree of inaccuracy in 4th on an inertial dyno would remain the same.

i was assuming that we would be able to put down noticeably more power in 4th gear because:

in 4th gear:

gear ratio = 1.171
final drive ratio = 3.941

this implies 1.171 x 3.941 = 4.615 engine revs per tire rotation.

in 5th gear:

gear ratio = 1.085
final drive ratio = 3.350

this implies 1.085 x 3.350 = 3.635 engine revs per tire rotation.


the difference between 4.615 and 3.635 engine revs per tire rev seems like it would make a reasonable difference. i don't know for sure simply because i have never tried dynoing in 5th gear, but i think it's a safe bet to say that it should be noticeable.

in the end, i think the most important thing is that 4th gear pulls are easier on everything involved simply because it puts a lighter load on the engine and the dyno. i forget what absolute engine load maxes out at in 5th gear, but it's noticeably higher than in 4th gear. also, it's a lot easier to run up to ~105mph than it is to run up to whatever speed 5th gear maxes out at.

[Darksun280]

um no way in hell I'll start a dyno pull in 5th at 3300 rpms the way my car sits now. no no no no no......

[AutoXRacer]

5th gear is way too tall to load up the car like that...use 4th...some people even use 3rd...but you'll get abnormally high readings.

[aaronc7]

I want to see a 1st gear dyno, lol

[happy and angry]

5th gear is way too tall to load up the car like that...use 4th...some people even use 3rd...but you'll get abnormally high readings.It doesn't really matter what gear you use (although first or second here would be dumb...) so long as you keep using the same type of dyno, use the same gear, and use it as a tool to track progress with your car rather than an absolute definitive number. I was just looking at it from a purely hypothetical "strictly speaking wouldn't 5th be more accurate on inertial dynos?"

[Sacrilicious]

It doesn't really matter what gear you use (although first or second here would be dumb...) so long as you keep using the same type of dyno, use the same gear, and use it as a tool to track progress with your car rather than an absolute definitive number. I was just looking at it from a purely hypothetical "strictly speaking wouldn't 5th be more accurate on inertial dynos?"

in this case, then i would say yes...just as long as no one attempts this on our car! (eekdance)