Dynos Straps And Friendliness

[rtune]

last week I had my car on the CRD dyno and they didn't strap it down,

saying there was no need. Is that normal? & if a car is strapped down

does it change the result & by how much?

last question: if a shop does a before and after run to show you how awesome

their tune is, how can you know whether the before was fair dinkum? is it

too cynical to think such things?

is CRD a "friendly" dyno?

[R31Nismoid]

Pretty normal, mine was never strapped with over 300rwkw

strapping does alter thing im lead to believe, how much or whatever is debatable

As for results - You compare to other peoples.

You should really know what ballpark your going to get if you search around. Most combinations have been done before, or with a bit of lateral thought you can bridge across and work it out. So as long as you fall into the area then thats about it.

Obviously if you make 300rwkw on the stock turbos @ 1bar, then thats not right.

But if you say make around 240-260rwkw @ 1bar... then thats about right. More about AFR's, midrange and that kinda thing

[dangerman4]

Pretty normal, mine was never strapped with over 300rwkw

strapping does alter thing im lead to believe, how much or whatever is debatable

As for results - You compare to other peoples.

You should really know what ballpark your going to get if you search around. Most combinations have been done before, or with a bit of lateral thought you can bridge across and work it out. So as long as you fall into the area then thats about it.

Obviously if you make 300rwkw on the stock turbos @ 1bar, then thats not right.

But if you say make around 240-260rwkw @ 1bar... then thats about right. More about AFR's, midrange and that kinda thing

not strapped at over 300 kws? eeeek

mine squirms a fair bit with straps, i would hate to imagine just wheel chocks.

sounds to me like a visit thru the dyno wall would be inevitable.

and old mates car made 360 rwkws while strapped down, we then took the straps off so it was actually just chained from going forward to far. this aloud it to get up on top of the rollers, first run it went to 385 rwkws.

we then all jumped in the boot, and the next run managed 404 rwkws.

no settings were changed just 3 runs one after the other.

but to the the original question, yea the dyno operator can do the initial run at 3/4 throttle to show how crap its running, and power is down.

they then root around looking at settings in your hc for a minute or two and then do a second run at full throttle. bang 30 kw gain. that'l be $300 thanks.

so yes there are bad operators out there.

but i highly doubt crd would be one of them.

[2rismo]

An experienced operator will make a judgment call on whether or not a particular car needs to be strapped down. Don't stress.

It's usually the cars that come on like a bomb that need to be strapped down.

[satanic]

Pretty normal, mine was never strapped with over 300rwkw

You're crazy right?

My car lifts even with straps front and back - there is no way in hell I'd let it go on a dyno without a minimum of rear straps! Not just to protect the car but also the people in front of it!!!

[2rismo]

You're crazy right?

My car lifts even with straps front and back - there is no way in hell I'd let it go on a dyno without a minimum of rear straps! Not just to protect the car but also the people in front of it!!!

Dude, there should never be people in front of any car on any dyno!

[R31Nismoid]

An experienced operator will make a judgment call on whether or not a particular car needs to be strapped down. Don't stress.

It's usually the cars that come on like a bomb that need to be strapped down.

Spot on

[satanic]

Dude, there should never be people in front of any car on any dyno!

Agreed... but try putting this into practice at a Dyno Day or something... Public Liability nightmare if the cars aren't strapped down.

[R31Nismoid]

Who said anything about a dyno day, public liability or anything else?

End of the day, certainly not the first time, certainly not the last. It can be done, and thats the question asked

[rtune]

but i highly doubt crd would be one of them.

I wasn't implying in the slightest that CRD would fudge before/after.

But there are many other dynos around sydney.

[Duncan]

yes not strapping it down can show a higher result - the higher the car climbs on the rollers the higher the power figure. until it falls off and kills everyone of course.

and yes there are plenty of simple ways to make a car look crap for a before run. do you have both before and after runs with all of the parameters printed on them? even then there are simple changes on the car light retarding the timing a little or even just letting it run when it is already hot that would make a difference

and finally, unless the ECU was editted/tuned, the boost was turned up or there was a problem fixed, there would be very little difference in before/after kws.

[jas/slo32]

i seen a 9 sec torana come off the dyno under full noise due to a strap failure it went all of one metre. cant have been too good for the driveline 8000rpm- idle.

[GTR1993]

yes not strapping it down can show a higher result - the higher the car climbs on the rollers the higher the power figure. until it falls off and kills everyone of course.

and yes there are plenty of simple ways to make a car look crap for a before run. do you have both before and after runs with all of the parameters printed on them? even then there are simple changes on the car light retarding the timing a little or even just letting it run when it is already hot that would make a difference

and finally, unless the ECU was editted/tuned, the boost was turned up or there was a problem fixed, there would be very little difference in before/after kws.

How does how high the car is on the front roller change the power output read?

Edited November 20, 2008 by GTR1993

[WARLORD]

i had mine at crd with no straps made 304kw atw ,then i went to a dyno day about 3 weeks ago and the car was straped down and made 309kw atw..... the only thing that was diffrent was the knock level was higher when straped and no knock on the street or crd dyno.

[R31Nismoid]

How does how high the car is on the front roller change the power output read?

heavily strapped you'll see cars sit on the two rollers, no straps the car will ride up on the front roller

less resitance = more power (in theory)

I might have to get strap/no strap tested next service to see

[GTR1993]

I know that, but the way it was written it was talking the higher it climbs on the front roller the higher the number. I dont see any reason for the car to be on the rear roller as its not knurled, and furthermore is free spinning so not needed to read power.

[STATUS]

yes not strapping it down can show a higher result - the higher the car climbs on the rollers the higher the power figure. until it falls off and kills everyone of course.

and yes there are plenty of simple ways to make a car look crap for a before run. do you have both before and after runs with all of the parameters printed on them? even then there are simple changes on the car light retarding the timing a little or even just letting it run when it is already hot that would make a difference

and finally, unless the ECU was editted/tuned, the boost was turned up or there was a problem fixed, there would be very little difference in before/after kws.

correct an untied car gives a more accurate reading than one strapped down, the tighter the strapping generally the lower the reading. a properly strapped car will move forward onto the front roller without being bogged down between both.... ie over tight

Edited November 20, 2008 by URAS

[tridentt150v]

UUUmmm, they strapped mine down hard, then actually checked and retightened the straps because of what they thought was wheel spin - 280rwkw, Yohohama AVs102's 255x 40's on 17" with good tread. So if they hadn't strapped it down it would have gotten bigger numbers? I might have cracked 281..... I assumed they new what they were talking about. What does wheel spin look like on a run anyway - not uncontrolled spin, but partial/light spin?

Not really bothered by it, the tune is the important thing.

[dangerman4]

the higher the car is on the roller the more weight is distributed onto the roller.

if its at about 60% almost half the rear of the cars weight is not pushing onto the roller.

therfore some sort of wheel spin is likely.

if its on top of the roller then 100 % of the rear weight is transferred onto the roller.

[GTR1993]

If it is strapped down from infront of the diff using the eyelets in front of the roller, then over the diff under the bar (the DD setup they use) as the car moves foward it is forced harder and harder into the roller as the strap acts as a type of wedge. Seems like a smart idea as the more power it makes, the more it wants to climb up but the harder its held in by the strap.