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Dyno Sheets

Don Dada

By Don Dada,
in Engines & Forced Induction

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STATUS Grand Master

STATUS

Posted
Posted (edited)
Or if you actually do a full gearbox dyno pull you can see exactly where the perfect shift points are.

Can't do that with RPM... :D

Speed rpm are the same thing..... (speed is useless without drag etc) your pull is from 15kmh to 200 or 1500-8000 its the same thing when standing still,

BUT if you time each gear in the car you can replicate this on the dyno in the ONE gear (1 / 1) if need be or we can what we do for a super sedan style car. We do pulls in 4 gears (ecu has gear/ based mapping) as they have two overdrive gears (300+ kmh) which load the engine more up top especially with added wind resistance. We datalog the car @ phillip island and sandown and run the dyno pulls accordingly.

Edited by URAS
juggernaut1 Proficient

juggernaut1

Posted
Posted (edited)

Don't speed based dynos tell us something about the diff gearing being used and therefore the expected boost curve for comparison purposes.

For instance I've seen some speed based dyno's which top out as low as 175klm's. In comparison mine tops out at 225klm's (s15) with stock diff gearing in 5th (1:1).

Why is this relevant? Well I would have thought that when comparing boost curves of similar cars (which of course we quite often do) I would expect the car with the taller gearing to spool earlier than the car with a lower diff ratio assuming a similar engine/turbo setup. So its kind of pointless comparing spool of the similar engine/turbo package on cars with different diff ratios becuase we've introduced another variable into the equation....being the diff ratios and the effect on turbo spool.

Edited by juggernaut1
STATUS Grand Master

STATUS

Posted
Posted (edited)
Don't speed based dynos tell us something about the diff gearing being used and therefore the expected boost curve for comparison purposes.

For instance I've seen some speed based dyno's which top out as low as 175klm's. In comparison mine tops out at 225klm's (s15) with stock diff gearing in 5th (1:1).

Why is this relevant? Well I would have thought that when comparing boost curves of similar cars (which of course we quite often do) I would expect the car with the taller gearing to spool earlier than the car with a lower diff ratio assuming a similar engine/turbo setup. So its kind of pointless comparing spool of the similar engine/turbo package on cars with different diff ratios.

You can move a boost curve around by 1500rpm based on ramp times regardless of diff ratio or gear, so it is hard to tell. And some dynos are roller speed limited (dyno dynamics) which means some cant be run ( 1 : 1)

TBH @ the end of the day you cant really compare dyno graph unless the two cars are run with the same settings ramp and diff ratios (like you posted). I do an average pull of about 9seconds in 4th, i have seen other operators run a time of about 16 seconds which is double and will move the whole graph to the left.... fairly heavily skewing the results making them look favourable (too responsive) too i might add.

Edited by URAS
winstonusmc Enthusiast

winstonusmc

Posted
Posted
I don't see the point of comparing to RPM...

When you are using a Dyno to tune a car, you need to know at what RPM your changes need to be. Example is if there is a flat spot or a drop in power, you know at what RPM to correct it on in the map.

MBS206 Grand Master

MBS206

Posted
Posted
When you are using a Dyno to tune a car, you need to know at what RPM your changes need to be. Example is if there is a flat spot or a drop in power, you know at what RPM to correct it on in the map.

Most of the ECUs (Including the one I run) run a map tracer.

As well as most good tuners can spot by just looking at fuel/timing maps where the dip will be as values will be off compared to other cells around it.

Edit: And the main thing my tuner used the dyno for was loading the car up...

He barely checked the power values it was putting out.

Used his widebang + laptop to follow how the car performed.

As Trent said, changing ramp rates affects things massively... We had to give mine the ability for the engine to rev up as quick as possible... The tyres just didn't wan't to hold onto the dyno no matter what we did... Which shifted how the curves looked.

We had started a pull that showed boot rolling at 5PSi at 3600RPM and making 193RWKW... But as it climb onto full boost at 4000RPM it just shredded the tyres... On the road I start to see about 3 - 5PSi of boost at 4000 - 4500RPM...

The dyno is useless for comparing no matter what... Use it as a tool to load the engine, no more.

juggernaut1 Proficient

juggernaut1

Posted
Posted (edited)
You can move a boost curve around by 1500rpm based on ramp times regardless of diff ratio or gear, so it is hard to tell. And some dynos are roller speed limited (dyno dynamics) which means some cant be run ( 1 : 1)

TBH @ the end of the day you cant really compare dyno graph unless the two cars are run with the same settings ramp and diff ratios (like you posted). I do an average pull of about 9seconds in 4th, i have seen other operators run a time of about 16 seconds which is double and will move the whole graph to the left.... fairly heavily skewing the results making them look favourable (too responsive) too i might add.

Oh yes I also check the same ramp rate is used too Trent.....I just assumed that was a given.

In the case of DD dyno's ....I also check the difference btn the ambient temp (AT) and intake temp (IT) are also not more then 10 degrees different <<<< thats just my personal tolerance, and that shootout mode is used.

Edited by juggernaut1
Cjmartz2k Proficient

Cjmartz2k

Posted
Posted
Did you mean Speed vs Power is useless. Or RPM Vs Power is useless. Coz you sound like you are disagreeing and then you agree? Im so lost

Yeah, sorry, I meant I don't like power vs. speed. I'm in favor of power vs. rpm in 4th.

And as mentioned, the type of dyno and the loading (or lack of) will affect the boost curve massively. More so than a difference a rear diff ratio is going to make. Things will never be exactly the same when comparing dyno sheets on a forum.

tridentt150v Grand Master

tridentt150v

Posted
Posted

I would have thought that power vs rpm would be handier long term for when your setting up the same car all the time and checking out engine mods without any effect different diff/gearbox/wheel radius ratio's would have on the result.

STATUS Grand Master

STATUS

Posted
Posted
Most of the ECUs (Including the one I run) run a map tracer.

As well as most good tuners can spot by just looking at fuel/timing maps where the dip will be as values will be off compared to other cells around it.

Edit: And the main thing my tuner used the dyno for was loading the car up...

He barely checked the power values it was putting out.

Used his widebang + laptop to follow how the car performed.

As Trent said, changing ramp rates affects things massively... We had to give mine the ability for the engine to rev up as quick as possible... The tyres just didn't wan't to hold onto the dyno no matter what we did... Which shifted how the curves looked.

We had started a pull that showed boot rolling at 5PSi at 3600RPM and making 193RWKW... But as it climb onto full boost at 4000RPM it just shredded the tyres... On the road I start to see about 3 - 5PSi of boost at 4000 - 4500RPM...

The dyno is useless for comparing no matter what... Use it as a tool to load the engine, no more.

i must admit having no rollers opens up so many more tuning possibilities than i had previous on a roller type dyno. Things i never even though possible or relevant become handy, some now i use every tune. Especially cars with high HP, cars with big stalls 5000 onwards are also so much easier to tune properly when you dont have to "work around traction" issues.

MBS206 Grand Master

MBS206

Posted
Posted
i must admit having no rollers opens up so many more tuning possibilities than i had previous on a roller type dyno. Things i never even though possible or relevant become handy, some now i use every tune. Especially cars with high HP, cars with big stalls 5000 onwards are also so much easier to tune properly when you dont have to "work around traction" issues.

I think having my car on the Hub Dyno would have been a huge benefit...

Mind you, for the power it's putting out (According to the dyno) it shouldn't really have been shredding tyres...

I think it's more HOW it comes onto it's power... As it does the same on the road...

250KW... Starts to see a couple of PSi of boost from around 3750 - 4000RPM on the road... By 4500RPM its on 1 bar (Which is all I'm running) but it surges from like 5PSi to 14.7PSi within the blink of an eye... And just decimates tyres...

Trent, any tuning tricks to make the turbo spool up earlier (Cam adjustment, fueling, timing) etc?

  • 7 months later...
SimonR32 Grand Master

SimonR32

Posted
Posted
Thought i'd ask this here instead of starting a new thread......

I'm in the process of tuning my car and want to know what gear to load it up on the dyno to get the proper load

Its a Rb26 with Rb25 box running 4.363 gears on 19' wheels

If you don't know what gear you should be using you shouldn't be going anywhere near something that can adjust fuel and timing of the motor!

Get someone who has a clue to do it...

Don Dada Mentor

Don Dada

Posted
  • Author
Posted

Dude....not every one came out of the womb with a spanner in one hand, screw driver in the next and was programming ecus at the age of 2 so give me a break.....

and trust me.... if it had someone who had a "clue" where i am from i would have carried my shit there a looooong time ago

The one dynojet in my entire country only gives power/torque readout.....no reference against boost, afr etc. so u try to figure out where i am coming from

I jut like to get experienced ppl opinions rather than the noobs we have here who interfere with your shit and then it blows up a week after

paulr33 Grand Master

paulr33

Posted
Posted

don dada that's a wierd combo

4.3 diff gears but then 19" wheels

are you sure you really want this combo?

no idea what it will look in mathematics / RPM wise

but use a diff / ratio calculator

you can find the R33 rb25 box 4th is 1.0x1 something, so that easy

then work out 19" size and 4.3 multiplier or however it works

Adriano Grand Master

Adriano

Posted
Posted (edited)

Just run it in 4th. Basically you want to run it in as high a gear as you can without overspeeding the dyno, as this reduces the torque at the axle reducing the chance of wheelspin. Also 4th is 1:1, so there is less stress/heat generated in the gearbox.

Edited by Adriano
Don Dada Mentor

Don Dada

Posted
  • Author
Posted
don dada that's a wierd combo

4.3 diff gears but then 19" wheels

are you sure you really want this combo?

no idea what it will look in mathematics / RPM wise

but use a diff / ratio calculator

you can find the R33 rb25 box 4th is 1.0x1 something, so that easy

then work out 19" size and 4.3 multiplier or however it works

Actually... i purposely went with 4.363 gears to compensate for the larger dia of the 19s to get it moving a little quicker from stand still considering it weighs about 1450kg

I also tried 3.9 gearing on it and it was terrible....it felt like the hand brake was up when pulling off.

Not sure what u meant by your comment but is there some thing i am not seeing????

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