Reading Dyno Charts

[mattdavies]

With John Bailey and James having their cars mapped yesterday there has been some positive talk about the power and torque from their dyno charts. Can someone explain what to look for and how it relates to street performance.

 

The only thing I know for sure is the area under the torque curve is pretty much the larger the better for street driving.

 

• How do you know when the boost kicks in ?
  
• When do you want to be making power from ?
  
• How do you know if it has been slightly fabricated ?
  

[chazuk]

This will get people going , I find it hard to tell when full boost is made easier to figure out with the boost/afr graph but no one seems to upload these as much as it also shows the rear wheel power which is allot less than flywheel print out.

 

Apparently on a RR and on the street it can spool slightly different but not by much people still swear by the best way to measure is via a hub dyno, lots of people will say you want it early as possible although 3700-4000k is still a good range for a big single the spool times are getting lower but it does produce even more traction issues although with a ecu such as a syvecs the torque can be trimmed and run lower boost in first etc.

 

Not sure I know it can be done very easily can also be done unintentional a car running crazy hp on rollers trying to run it in 1:1 ratio 4th on a supra it just spins up maybe resolved by running in 5th but its a overdrive and will alter the true reading, and I did know of someone that had their reading fiddled with as it was so close to the next round number but not by anyone on here or supra related was back in my skyline days how to tell I don't know but I doubt anyone on here would be into that neither would any of the mappers on here.

Edited March 12, 2015 by chazuk (see edit history)

[j_jza80]

Generally speaking, the larger the amount of area below the power and torque plots, the quicker the car will be. But that is only a VERY rough rule.

 

You can clearly see on turbo dyno printouts when full boost is achieved, as the gradient of the plots increases greatly.

 

Peoples aims and goals really depend on what they want from the car. Ideally on a fast road car, you want the sharp gradients at the lower end of the scale (rev range), with a progressive increase until reaching maybe 6000 rpm or so. Full on drag cars making big power with raised rev limits might not see a sharp rise in their power band until MUCH later on, but as they spend all of their time at high RPM, it doesn't matter.

 

But you can't really tell much about a car from a dyno plot alone, it is only really an indicator.

Edited March 12, 2015 by j_jza80 (see edit history)

[johnny g]

The dyno plot is a graphical representation of the engines power delivery.

Horsepower is a function of torque.

BHP = (Tq * RPM)/5252

 

Basically, as revs rise, BHP rises (unless torque falls off so much that power dips).

 

Follow the torque curve and look at where it rises it starts to rise up. That's the boost threshold, where the boost starts to have an effect on the engine. This is not maximum boost, this is purely where you want to have boost that is positive. Ideally, 2700-3000rpm for this for a road car. In an ideal world, torque would remain constant, allowing a smooth power curve (i.e. linear growth).

 

When people talk about "area under the curve", they want the earliest spool whilst giving the power required to the rev limit (or thereabouts). For the best results, your turbo and cams should be matched.

You don't want a turbo that spools at 5000rpm on a set of 256's, similarly, you won't want 280's on a 6266.

[Chris Wilson]

Area under the torque curve with a nice gradual rise and fall slope. a sudden vertical climb in torque will make for an aggressive power delivery that may well have poor traction and drivability implications. If the power and torque do NOT cross at 5252 RPM the graph is a dud and meaningless, that's simple physics. This explains quite well:

 

http://www.lainefamily.com/hp.htm

[Chris Bailey]

Here's dads graph from yesterday, spools alot faster than that on the road.

 

[j_jza80]

That must be savage when it comes on, look at the gradient between 4200rpm and 4600rpm.

[Chris Wilson]

I would not call that a nice curve, it would be a nightmare on wet or greasy roads. What cams are in it? What TB? What plenum?

[j_jza80]

I would not call that a nice curve, it would be a nightmare on wet or greasy roads.

 

I didn't call it nice, I called it savage.

[Chris Bailey]

I would not call that a nice curve, it would be a nightmare on wet or greasy roads. What cams are in it? What TB? What plenum?

 

SRD 264 cams, stock intake and throttle body.

 

Its very savage when it comes on full boost, pushes you back hard into the seat.

[Chris Wilson]

It's probably the turbo sizing then. Or try softer cams. Looks like a candidate for decent traction control

[Chris Bailey]

It's probably the turbo sizing then. Or try softer cams. Looks like a candidate for decent traction control

 

The turbo is a Precision 6466DBB GEN2 1.00 A/R.

[Chris Wilson]

I only understand Garrett stuff, sorry! If it can't be rebuilt in the UK I don't want to know, and Garrett is king for getting bits over here.

[j_jza80]

I only understand Garrett stuff, sorry! If it can't be rebuilt in the UK I don't want to know, and Garrett is king for getting bits over here.

 

The reason these Gen2 Precision turbos are popular is because from what I can tell they do have a slight performance advantage over the Garrett GTX range.

 

I'm also not that clued up on Precision sizes, but I think it is roughly the equivalent of a GTX3582R.

[Chris Bailey]

The reason these Gen2 Precision turbos are popular is because from what I can tell they do have a slight performance advantage over the Garrett GTX range.

 

I'm also not that clued up on Precision sizes, but I think it is roughly the equivalent of a GTX3582R.

 

Its a 64mm, good for around 900bhp.

[j_jza80]

[JamieP]

If comparing graphs you can only compare from the same dyno, hub dynos load the car more and it will look to spool faster.

 

Mine. 3500rpm it's making 400ftlb, 4000rpm it's making almost 600ftlb, really nice on the road, just digs in and pulls hard with a huge powerband, boost is restricted a little low down as it was making to much torque, you can see full boost hits at about 5500rpm

 

 

Edited March 12, 2015 by JamieP (see edit history)

[johnny g]

That's a much nicer torque curve, JP

[j_jza80]

Seconded, much less peaky.

[Chris Bailey]

Jamie's is a very nice graph, but its easier to dyno a manual car.

 

Auto's are harder, especially with a hi stall. Lee said it just feels like its slipping all the time. Maybe that might be to do with the way dads graph has come out? Im not sure.

 

Very happy with the performance though on the road though

[Wez]

As already mentioned you can really only compare graphs from the same dyno and operator, some will plumb in a VAC line too which shows real MAP reading.

 

Again as already mentioned, roller dynos tend not to load up the motor as much, therefore you will get better spool on the road, one of the reasons a road check is carried out, hub dyno`s can be programmed with additional load and patterns, some of the stuff they can do when operated properly is very trick. I have been sat in a motor with throttle wide open and the hub dyno loaded and unloading the motor to hit the desired load and rpm cells.

 

As for a road car, a nice broad torque curve / powerband

[Kaan W]

Chris is right, even when I had mine dyno'd before with the high stall the torque curve was inaccurate. Felt the same on the road though just more of a kick.

 

http://www.mkivsupra.net/vbb/attachment.php?attachmentid=198754&d=1426198641

 

On the exact same setup without the high stall a very different reading was given -

 

http://www.mkivsupra.net/vbb/attachment.php?attachmentid=198753&d=1426198618

[Jamesy]

This is from when Sumo Power owned my car. Its pretty agressive...

 

[mellonman]

To read them they are abit like a map , the numbers are on the side and along the bottom , you can just follow the power and torque lines and see when and what power it made