Dyno Sheets

[Don Dada]

Is there something that I'm missing out on???.......If so pls inform me but........

Why the F@$k dyno sheets are done with speed instead of rpm?!?

To me i find it verrry annoying and makes it somewhat impossible to compare response and overall results of different set ups.

[Sean W]

anyone can feel free to correct me if im wrong but..

my understanding is that speed graphs mean you cannot really disguise a laggy setup,whereas displaying vs. rpm you can. if for instance the dyno run was done in 5th, you could have the car very very slowly pulling from 2000rpm all the way to redline, and this slow climb in revs would give a massive turbo time to spool by say 3-3500 rpm and by looking at the printout you wouldnt know. This same setup displayed as speed instead of rpm you would see that it was still only making massive boost because it was in 5th up round 200kph, not a useful track/street setup neccesarily.

By displaying in speed this fudge factor is taken out as the dyno tuners are forced to make runs in 3rd or 4th which shows us actual meaningful response times for the power delivery. By knowing roughly your gear ratios and comparing this to the speeds on the dyno chart you can tell what gear the run was done in and thus whether or not to take the responsiveness (or lack of) of the engine with a grain of salt....

Hope this helps

Sean

[CEF11E]

a lot of the time, the car's is calibraded against the dyno speedo. this will tell you the multiplier (diff) datio. if the car is in 4th (1:1 ratio)

if this is done correctly its a good indication on your actual speed. RPM is based off the same calculation of dyno to tacho and is quite often off by a few 100 rpm. that is why most operators leave speed as the reference.

its pretty easy to work out rpm from speed. all you need to know is the diff ratio. and as long as the tyres used are close to the correct rolling diameter you will be right.

sorry I hope some of this makes sense, my head is all over the place., might read it later and see WTF i ment...

[paulr33]

RPM = SPEED / 28

this assumes standard diff gears and car dynoed in 4th gear

[Don Dada]

Yeh.... but how many cars still have stock rims and tyres???

Rim and tyre size vary far and wide so an rpm reference will be more accurate when comparing against other cars........well on paper at least.

[The Dan]

They don't do it because it takes longer to set them up....that is all.

And it's not / 28 for all cars either. All of our cars run ratios from 3.9 to 4.11 to 4.375 and a few others as well. It gives you an idea but still not 100%.

If you ask your dyno op to hook it up vs rpm then they will. It will just cost you a little more.

[STATUS]

They don't do it because it takes longer to set them up....that is all.

And it's not / 28 for all cars either. All of our cars run ratios from 3.9 to 4.11 to 4.375 and a few others as well. It gives you an idea but still not 100%.

If you ask your dyno op to hook it up vs rpm then they will. It will just cost you a little more.

TBH most of the guys ive talked to cbf'd doing the setup for each car, i don't have a choice with the dynapack as everything has to be calibrated (rpm matched to within about 5-10rpm) before commencing any runs, its easy and takes about 1min to do.

[Lithium]

my understanding is that speed graphs mean you cannot really disguise a laggy setup,whereas displaying vs. rpm you can. if for instance the dyno run was done in 5th, you could have the car very very slowly pulling from 2000rpm all the way to redline, and this slow climb in revs would give a massive turbo time to spool by say 3-3500 rpm and by looking at the printout you wouldnt know. This same setup displayed as speed instead of rpm you would see that it was still only making massive boost because it was in 5th up round 200kph, not a useful track/street setup neccesarily.

Not true, the dyno controls the speed the car revs out... so it doesn't really matter which gear it is in, in that respect.

[SimonR32]

rpm is directly proportional to speed

v1/rpm1=v2/rpm2

if you can't work this out i doubt it's even worth comparing dyno figures

[Don Dada]

Not sure about the other dynos but i know on the dynojet it's just a matter of hooking up the pick up around the loop on the back of the engine for the rpm.

For example, it would just make life sooo much easier to see at what rpm the turbo is on full boost without having to do calculations if u know what i mean!!!

[Adriano]

As trent said, it takes abot 1 minute to do, unless you have the inductive pickup option, then it takes 10 seconds

[Don Dada]

Well if it so easy to set up on any given dyno then everyone should request rpm instead of speed, since it makes it a lot easier to compare results and speed having no other real benefits

[R31Nismoid]

I thought it was so you got a free speedo check with each run?

[Don Dada]

Ha ha!.......What good would that be when tuning!?!

I'd prefer driving my car without the speedo working than have no rpm indication!!!

[MBS206]

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

Torque VS Speed is going to be the real winner in a race.

Seeing that a car makes say an average of 500nm of torque across a 70KM range, is much more beneficial then seeing it makes 500nm across a 2000RPM range when you're comparing a vehicle on the track...

[STATUS]

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

Torque VS Speed is going to be the real winner in a race.

Seeing that a car makes say an average of 500nm of torque across a 70KM range, is much more beneficial then seeing it makes 500nm across a 2000RPM range when you're comparing a vehicle on the track...

they are directly related so its a moot point.

[heller44]

Possibly be better if, say, comparing quite a few vehicles on one day.. Lots of different final drive ratios, if you kept the charts all referenced to rpm it would be easier to make a comparison?

btw, thats a question not a statement..

Edited December 6, 2009 by heller44

[Cjmartz2k]

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

Torque VS Speed is going to be the real winner in a race.

Seeing that a car makes say an average of 500nm of torque across a 70KM range, is much more beneficial then seeing it makes 500nm across a 2000RPM range when you're comparing a vehicle on the track...

Because you are trying to see what your ENGINE is doing when you put it on a dyno, not how the car will perform. You have the track for that--and don't say suspension/tires don't allow for that, because you can look at mph and just how fast you went down the last half of the 1/4. The power vs. RPM dyno sheets look useless IMHO, and I think it's just the operator not feeling like setting everything up for an RPM reading. Just my opinion though.

[Lukas 33]

Because you are trying to see what your ENGINE is doing when you put it on a dyno, not how the car will perform. You have the track for that--and don't say suspension/tires don't allow for that, because you can look at mph and just how fast you went down the last half of the 1/4. The power vs. RPM dyno sheets look useless IMHO, and I think it's just the operator not feeling like setting everything up for an RPM reading. Just my opinion though.

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

[MBS206]

Because you are trying to see what your ENGINE is doing when you put it on a dyno, not how the car will perform. You have the track for that--and don't say suspension/tires don't allow for that, because you can look at mph and just how fast you went down the last half of the 1/4. The power vs. RPM dyno sheets look useless IMHO, and I think it's just the operator not feeling like setting everything up for an RPM reading. Just my opinion though.

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...