Well, I went down with 13 other guys to a local(ish) dyno and ran the STS.

Thing is, the numbers are way higher than I would expect (they are crank BTW).

It's a 2000 model with only 20,000 on the clock and I've done minimal performance upgrades (eg Accel panel filter, hand smoothed airbox and so on). Yes it was running 98 Octane fuel, but even so...

So I figured the dyno was over-reading.
But other cars there today (all American, Mustangs and Camaros mostly)that were stock gave stock figures (or to within a couple of BHP) and cars that were modified with bolt-ons (eg Exhaust, CAI, chip etc) were giving up to 30BHP over stock.
So the dyno seems accurate.

Figuring it was a bad run I got them to run it 2 more times and on both occasions the car gave figures to within 2-3 BHP of this graph.

The curve shape looks about right, the car didn't wheelspin.
I'm at a loss to explain the high figures...


Feel free to call BS, but please back that up with an explanation.


http://homepage.mac.com/hardrockcamaro/.Pictures/cadillac/cadillac_rr_graph.gif

Looks very impressive. Maybe you got a freak from the factory. How does the car do on the street/strip? Is it performing better than Cadillac says it ought to?

How bout you take it to the track and test it out?

I will be taking it to the track in a couple of months.
But that does introduce driver launch skill (last time I went in the IROC my reaction time was around a second with a 60 foot time of 2.3... :( ) and basically I need a lot more practise.

From a roll on the road (ie no driver skill required) it's very fast. I beat turbocharged Subaru WRXs easily, same goes for 545i BMW's, stock(ish) Mustang GTs and so on and so forth.

I'm pleased (obviously) but I'm also a bit skeptical althoguh I have had cars in the past dyno'd and I almost always seem to end up with one that does better on the dyno than identical models. Mass production or not, there's a lot of varience in tolerences, just enough to throw 10% your way on a good day.

I should also point out that this dyno is at sea level and it was a cold day (around 5 degC).

Crank HP you say? So they pulled the motor, put it on the dyno outside of the car?

Now even if that is crank HP it's way more than there should be. If that's wheel HP, that's WAY THE HELL more than it should be unless someone snuck a turbo in there when you weren't looking.

As far as temperature and altitude, you usually get SAE corrected (at least here in the US you do) unless you ask for uncorrected or unless they give you both.

I'm at a loss as well.

WOWW!!!

Dont I wish.

I thought that HP increased as the temperature dropped? (not significantly of course) Hmm...maybe not?

Curious noob question tho...how does sea level affect HP?

It does, but only minimal levels. nothing like what his dyno revealed.

If you say there was no wheelspin then obviously they must have used some sort of correction formula to get there. 320 is pushing it for a fact freak but 360...thats just not possible i dont think

Elevation has A LOT of impact on an engine's performance. I live at about 7000 feet and when I drive my car to the inlaws in California, it feels like an increase of 50 HP, easily. But we're talking THOUSANDS of feet in difference, not just a couple of hundred.

I thought that HP increased as the temperature dropped? (not significantly of course) Hmm...maybe not?

Curious noob question tho...how does sea level affect HP?

Here's a calculator to help visualise how temp and altitude affect power and thus 1/4 mile times:

http://www.stangbangerz.com/modules.php?op=modload&name=hpmph&file=density

Play around with it a bit.

Concurring with DAVE, those numbers seem suspect. No I cant offer a reason why becasue, well, I aint that smart!

But, those numbers to not reflect all REAL numbers posted by reputibale sources.

Here's a calculator to help visualise how temp and altitude affect power and thus 1/4 mile times:

http://www.stangbangerz.com/modules.php?op=modload&name=hpmph&file=density

Play around with it a bit.

Ok, played around with it a lil...came to a conclusion if and only if any other variables aren't changed, and the altitude is high/elevated, then the power in HP increases, yielding a direct relation between HP and sea level.

But I want to know why is this? Well, I know that air is thinner as you go higher in the atmosphere, and temperatures seem to drop...so temperatures dropping mean an increase in HP (slightly), but how does the elevation play a part in this?

[Edit--

Still messed with it, times decreased (meaning the car got faster) when the temperature increased...now im confurrrrrsed?

I agree that the number is too high.
320BHP I would accept.
But 360 is too high.

I've watched a few videos on the net of dyno runs and I've noticed that in the US they run the car up through the rev range and that's it.

In the UK, they run the car up the rev range in the 1:1 gear and then they let it come back down again (blipping the throttle every 500rpm or so) and the dyno measures the drag to calculate transmission losses. I'm not sure if they put it in neutral for the part where it comes basck down.

We can have a long argument over whether or not that system works, but every car I've seen put on there has given a calculated crank figure to within 2 or 3BHP of what the factory says. As for lightly modded cars, they also give figures I would expect, whereas cars in the USA with the same light mods always seem to give more. That's obviously not possible so I think the numbers vary due to a different way of measuring things.


I'll post a video up of the run...

Video of the run, from 3 different cameras:

Right-click and Save-As...

http://homepage.mac.com/hardrockcamaro/.Public/STS%20on%20Dyno.mov

Well I emailed them and they sent me this back:



The US dynojet dynos are inertial rollers, they use a roller of known weight and size (therefore known inertia). They use this known interia value to asses the torque output of the vehicle by its ability to rotate the roller. These dynos output Rear Wheel Horse Power mostly in use in the states and most commonly seen above the gound so the car has to go up a ramp to get to the dyno. Although some shops have them sunken in to the floor.

Almost all dynos over here are of the electrobrake variety. They use a lighter roller set with an electromagnetic braking system. The car is run flat out in 1:1 gearing with the brake to maximum effect allowable, obvously, too much braking force would cause damage to the transmission. So, the car is at wide open throttle in 1:1 gear with the brake holding the car at say 10mph !, the brake is then slowly dialed off and the car is allowed to accelerate. These dynos output Rear Wheel BRAKE Horse Power

Both dynos will produce different numbers and are not comparable, as the units are different... WHP vs WBHP

In the same manner, the correction factor measurements and calculations for transmission losses are also different and typically there is a large difference between the wheel BHP and crank BHP.




So in other words, stop getting your brain into a pickle over it!

LOL!

Is this number to the wheels? or the fly wheel? If it is at the wheels the dyno is way off...sorry to tell you that but a stock Northstar with an air filter change will not make that kinda numbers at the wheels. I've dynoed many cars and bikes and have a 98 sts seat of my pants tells me no way. I have a GTO that makes 330rwhp/400 rwtorq.....this gto would whip my 98 sts! I'd ask for my money back or re-run it when the dyno's recalibrated....most shops inflate the numbers....thats what we want. The best way to calculate hp is the 1/4 mile. Good Luck at the track trying to back those numbers my hubble opion says no way.

Mornin' Andrew,

I've been following this thread since you posted your Dyno runs and I have a couple of questions and a few observations.

1. You had this Dyno done in England, London to be specific correct?

2. IF #1 is true are there ANY variables that could have influenced the outcome of 360HP? For example, was the Dyno machine running on European current, 230v and 50hz, or was it an American machine connected to a transformer putting out 120vac/60hz? When was the last time the Dyno was calibrated? Did you see the calibration sheet? Is there any possibility of a Metric System and SAE conversion conflict or variance?

3. IF you are satisfied that this was a good Dyno run and that ALL of the 'possible error' factors have been eliminated I'd say congratulations!

4. Also, for those of you questioning the temperature and altitude issue. Any pilot will tell you that your concern is based on Boyle's Law of Partial Pressure. One liter of air at 40 Celsius has FEWER molecules and is therefore LESS Dense than One liter of air at 0 Celsius which has MORE molecules and is therefore MORE Dense. In aviation we refer to it as the current or forecast Density Altitude. The higher the DA the worse your N* engine will perform. i.e. Colorado in the Summer time vs. Florida in the Winter.

My helicopter performs a whole lot better in cooler air and lower altitudes than during the dog days of summer when we are all hurting for power.

Andrew's Dyno run had an advantage of 5 Celsius vs. the Standard Day temp of 15 C or 59 F at Sea Level. Was it enough to add 60bhp to the Cadillac advertised STS 300hp/295ftlbs? I don't know, but I concur that it is doubtful.

I was unable to view the video due to a 'Software missing and unavailable' message. However, I'd say once you have eliminated all of your variables the Dyno results would stand.

I'm going to read a little more on the European Dyno standards because something tells me that is where the anomaly is found.

Looking forward to the final answer.

Never give up, Never surrender

JP:want:

Thanks JP.

I don't know what model of dyno it is.
The figures given are at the crank but no mention was made of SAE (as SAE is an american standard, not a UK one which would begin BS followed by a number)

The dyno run was done at a place called Engine Advantage Ltd, in Witham in Essex.
Google Earth tells me the Elevation is 80ft above sea level.

I didn't ask to see a calibration cetificate.
It didn't enter my mind as mine was the last but-one car to go on and everyone before me had sensible numbers.
For example, my mates 98 Mustang GT which is bone stock should give 225BHP. It gave 227BHP. That's such a tiny difference it's hardly worth noting.

A friend of mine has a 96 GT (215BHP stock) with a 9PSI Paxton supercharger, methanol injection, decat, exhaust, larger throttle body and MAF. That gave 327BHP which sounds reasonable to me.

However, a 1996 Mustang Cobra which should be 305BHP gave 285BHP, so that was down a little (so it's not like the dyno was over-reading for everybody) but maybe it needed a tune up?

A guy with a 1988 Mustang GT (225BHP stock) with Flowmaster exhaust, K&N air filter, ported plenum and ac ouple of other tiny bits like that got 255BHP.

A guy with a 2001 Mustang with the 32valve Cobra engine and a Vortech supercharger and some bits (exhaust and other stuff) got 413BHP. The stock Cobra motor is supposed to be 305BHP (or even 325BHP on later cars actually but I'm not sure what year his engine is) so again with a blower on a 305-325 BHP engine 423BHP doesn't seem unreasonable.

A fairly heavily modified Lightning (by heavy I mean higher supercharger boost due to a smaller pulley, exhaust stuff, intake stuff, some custom mapping and so on) got 514BHP. Whch I thought was a lot but looking around on the net seems very do-able especialy as the guy has done a lot ot it as he normally drag races it in some street class or other.

The most powerful car of the day was a 68 Camaro that is a street strip car (with emphasis on strip) with a 400 small block with AFR heads, a nitrous cam, fancy ignition, everything ported to hell, Flowmaster race mufflers. That gave 500BHP on the nose. The owner then switched on the 150 shot of nitrous and it gave 640BHP. So again, sounds about right.


So all their figures seem on the money to me.
If the dyno calibration was off surely everyone would be off?

I can't figure why just mine is wrong.

Because as pleased as I am, it must be wrong.

60BHP over book figure for just an air filter and a few other minor tweaks. I was hoping for 310. I would have accepted anytihng up to 320-325 as a result from having a "good one" from the factory and the tweaks working well. But 360 I just can't believe.

I used to have a 1.8L Ford that made the same amount of power (from the factory) as my friends 2.0L one.
We fitted the same CAI, off the shelf prom, exhaust to both and I ended up with 12BHP more than his 2.0L So I basically extended my lead on a car that shouldn't have been as powerful as his to begin with. So I know it can happen. Slight variences in cam timing, head castings, piston ring fit,ignition system varience. But 10-15BHP is not 40-50BHP!

I even got them to run the car 3 times. Each time I got 359, 356, 357

So if mine is wrong, and everyone else's was right, it's at least consistently wrong, lol!

I might try a differnet dyno (for another $100!), but I would expect a different result from a differnet dyno on a differnet day anyway, so it's not going to answer my question.


<EDIT>

On a side note, on the road, from a roll, the STS whips the 227BHP 98 Mustang GT and stays with the 327BHP Supercharged 96 Mustang.

Well, I went down with 13 other guys to a local(ish) dyno and ran the STS.

Thing is, the numbers are way higher than I would expect (they are crank BTW).

It's a 2000 model with only 20,000 on the clock and I've done minimal performance upgrades (eg Accel panel filter, hand smoothed airbox and so on). Yes it was running 98 Octane fuel, but even so...

So I figured the dyno was over-reading.
But other cars there today (all American, Mustangs and Camaros mostly)that were stock gave stock figures (or to within a couple of BHP) and cars that were modified with bolt-ons (eg Exhaust, CAI, chip etc) were giving up to 30BHP over stock.
So the dyno seems accurate.

Figuring it was a bad run I got them to run it 2 more times and on both occasions the car gave figures to within 2-3 BHP of this graph.

The curve shape looks about right, the car didn't wheelspin.
I'm at a loss to explain the high figures...


Feel free to call BS, but please back that up with an explanation.




I'm curious as to what your friends thought? I bet they were impressed. What are their figures? LOL.

Well, they think the dyno figures for their cars are correct, whereas mine are wrong. Although they don't know why.
The ones calling BS are the Mustang owners who made less power than me (funny that!). Especailly those who did a few tweaks to push their cars over the magical 300 as they knew my car was meant to be 300BHP and theirs were a little shy of that. Imagine the look on their faces when we finally run mine and it still makes more than them! lol!

The ones who have been in the car or who have seen me pull alongside and plant it and disappear think the figure is correct regardless of what it is meant to have.


Personally I'm skeptical. I just don't figure I can be that lucky.
But with the other cars figures seemingly correct I have no explanation of why mine is far too high.
Maybe it is correct and I'm just lucky or maybe there is something different about the transmission in the STS that throws off the dyno whereas the transmissions in the late model Mustangs, F trucks and Camaros are ok?

I dunno.
I'm grasping at straws here.

As the prior owner of a bone stock '98GT I find even the numbers for that car BHP wise to be a little high. Not the tourque though.

Well it seems like that dyno shop is using an algorithm to estimate bhp at the crank.

As Davesdeville mentioned, usually the readout given in shops here is "at the wheels" so one must use his imagination or some pen and paper and figure out from the stock specification to the actual wheel horsepower how much of that loss is powertrain loss (lost to heat/friction, etc).

If that dyno shop gives you a final number using the same method used here (put your car on a roller), then they are estimating the horsepower "at the crank" by means of an algorithm.

It seems accurate on the other cars you mention. Maybe FWD vs RWD calls for a different algorithm, who knows. This is all my speculation.

FWD vs RWD is another good point as mine was the only FWD car there...

They do indeed use an algorithm.
On the dynos in the US you seem to run the car up through the rev range and voila a wheel figure i produced.

Over here the car runs up the rev range and then also gets measured on the way back down (in neutral I think but don't quote me on that) to see what the transmission losses are.

The wheel figure on the way up (normally about 40% less than the manufacturers advertised crank figure and way less than the wheel figures US forums quote) is used along with the measured transmission losses and a correction factor for at least air temp (often not measued by the cheaper dynos, instead entered as a value by the operator) as well as maybe a couple of other things that are over my head.


The wheel figures I see quoted on US forums always sound about right, because when I add either 15 or 20% to that figure (depending on manual or autobox) I arrive at the figure given for the crank over here on the same model of car.

that is one of the roughest dyno's ive ever seen a car go on. Im used to seeing cars here accelerate through the revs quick but that dyno held the car wOT in one gear for what seemed like 30 seconds. Your poor transmission must have been feeling the pain. The RWD cars must have been put on the back set of rollers which does throw a variable in there as your car is on the front.

It is very hard on the transmission (and for that matter the engine as they are simulating the maximum load that is possible to get).

Lookg at what they emailed me, they hold the car at WOT at a low speed (like 10mph or whatever) by using the electromagnetic brake on the dyno. They then slowly release that brake and the amount they have to release it to let the car accelerate tells them the power the car has at the wheels.
On the way back down they put the car in neutral (I think) and then take some other reading to see what the transmission losses are.

All UK dynos I've been to (which is 4 so far) use the same system.

The different rollers (front set vs rear set) is the only viable reason I can think of for the car having a reading so out of whack with the RWD cars...

The way to compare apples to apples -- is to skip the algorithm and test all cars for bhp at the wheels. Without the algorithm you get what's there and not an estimate.

Then each user, or possibly the algorithm with a disclaimer, can estimate what it's producing at the crank.

I see what you're saying, but the only car dependent inputs the algorithm gets are the wheel BHP from the acceleration run and the losses from the slowdown run.

All other inputs (be it temperature or whatever) will be the same for each car.

As the dyno measures the acceleration (as per an earlier post) and measures the losses through deceleration the numbers should be consistent unless someone has a slipping transmission or whatever.

And the dyno does seem to be consistent.
The other cars got a figure that was consistent with their stock figures (or estimated figures based on mods and what other people have got throughout the world with those mods).

Plus, the Supercharged 96 Stand was run 2 weeks previously on another dyno (brand new and state of the art, they can even set what intake temperature they want to aid with mapping) and that gave 325BHP at the crank using the same measuring system. Whereas yesterday the same car got 327BHP on a different dyno. That's close enough for me.


I'm happy enough with the estimation system as it's based on 2 measurements (not just accelerating the car up and getting a wheel figure and then adding a percentage to estimate crank) and appears to be consistent enough. Sure, pulling the motor and putting it on a bench dyno is the only way to know what the real crank figure is, but the figures are close enough for me.


I think the only reason my cars figure may be wrong when the others wee right is due to teh fact it was running on the front set of rollers not the rear. It's wierd, as it's a 4x4 dyno and they calibrate the front and rear at the same time as they mostly use it in 4x4 mode due to all the Japanese Imprezzas, Skylines and Evos that they tune.

But even so, that's the only thing that stands my car out from the others. The front set of rollers, which must be out of calibration, as opposed to the rear, which are probably bang on.

So if it's wrong, that will be why.

Ok, played around with it a lil...came to a conclusion if and only if any other variables aren't changed, and the altitude is high/elevated, then the power in HP increases, yielding a direct relation between HP and sea level.

But I want to know why is this? Well, I know that air is thinner as you go higher in the atmosphere, and temperatures seem to drop...so temperatures dropping mean an increase in HP (slightly), but how does the elevation play a part in this?

[Edit--

Still messed with it, times decreased (meaning the car got faster) when the temperature increased...now im confurrrrrsed?

Ok, leaving all the variables as the default ones will result in a corrected time of 13.58. Changing the track altitude number from 900ft. to 5300ft like ABQ Dragway results in a corrected time of 12.31. Meaning if you ran a 14 up here, you could run a 12.3 at sea level. And if you ran a 14 at 900ft. then you could run a 13.58 at sea level. So it takes significantly more power to run that 14 up here than it does down there.

Temperature is the same way as altitude, but there's less of a range of possible temperatures.

Screw it. Go run a couple 1/4 miles. (You do have those in the UK, right?) If you run mid-higher 14s, you're normal for a stock STS. If you're in the mid-low 14s you have a really good one, if you're anywhere in the 13s range you have a redonkulous factory freak.

The closest one to me is about 80 miles away and is currently shut until next month. The next closest one is abput 100 miles away, and the final one (that I know of in the UK) is the other side of the country in Scotland.

I will be taking it to the strip in the next couple of moths as I'll be going down with my buddy and his 68 Camaro. So I'll run mine on the day too for kicks.
If it has 360BHP then I would estimate a mid 14s run for a car of this weight. A friend of mine has a 220BHP FWD car that weighs about 40% less and that runs 14.7. My other friend with a 280BHP convesion on that car runs a 14.2

I'd estimate 300BHP from my STS to give me around 15.0 - 15.1 and 360BHP to give me 14.6ish

Mind you it's hard to say really.

Regardless, it's gonna be fun!

A Bone stock STS should dyno anywhere between 235-240hp (which is being generous) at the wheels. You said that the shop was using some sort of algorithm to caluclate hp at the crank? Do they use it to determine drive train loss or what? The 4T80E trannsmission eats up about 20-22% of your power, which is why they tens to show lower numbers when compared to other FRD cars which normally suffer from less overall drag. Perhaps the shop was performing their calculations based on a lower drivetrain loss percentage? That would definitely bump the number up significantly.


With 360bhp you better be runing lower than a 14.6. I ran a 14.809 with traction issues and all I've got is the Corsa exhaust (granted they say it adds 20, but I can't prove it). With 40-50 more hp, you better be hitting low 14's. That 14.809 pass was also at 94.5mph. I'd be expecting a trap speed at least 2mph faster than my car with 360bhp as well.

Yeah but I suck at drag racing!

LOL!

Plus the tracks over here are not prepared like yours.
They only put that sticky stuff down when the big boys (top fuellers etc) are having a weekends racing.

Cars over here always run slower than in the USA.

For example, I know of no-one who has managed to get a bone stock LS1 Z28 Camaro to run better than 13.7.



I found some interesting stuff on dynos over here:

http://www.dynamometer.fsnet.co.uk/power-losses-flywheel-BHP.htm

A small portion of that gets repeated twice on the page (some sort of HTML error probably) before some extra info in the last few paragraphs.

Well it seems like that dyno shop is using an algorithm to estimate bhp at the crank.

As Davesdeville mentioned, usually the readout given in shops here is "at the wheels" so one must use his imagination or some pen and paper and figure out from the stock specification to the actual wheel horsepower how much of that loss is powertrain loss (lost to heat/friction, etc).

If that dyno shop gives you a final number using the same method used here (put your car on a roller), then they are estimating the horsepower "at the crank" by means of an algorithm.

This is all my speculation.

I'm speculating too, but I think that mtflight is on to something...

I'd ask the dyno shop if final drive ratio factors into this calculation of power... If it does (and I'm betting it does) then they entered in the final drive ratio of an SLS not your STS... do the math... 3.11/3.71 X 360HP = 302HP which is what you should be seeing...

Ok, played around with it a lil...came to a conclusion if and only if any other variables aren't changed, and the altitude is high/elevated, then the power in HP increases, yielding a direct relation between HP and sea level.

But I want to know why is this? Well, I know that air is thinner as you go higher in the atmosphere, and temperatures seem to drop...so temperatures dropping mean an increase in HP (slightly), but how does the elevation play a part in this?

[Edit--

Still messed with it, times decreased (meaning the car got faster) when the temperature increased...now im confurrrrrsed?

This is how i would explain it.

At sea level, the atmospheric pressure is about 14psi, and as you go up in altitude, that pressure drops. The more pressurized the air is, the more dense it is. When air is more dense, more oxygen will be able to get into your engine at the same time to help with the combustion process.

Likewise, temperatures effect air density as well. The colder the temperature, the more dense the air is.

So your engine will perform the best on a really cold day at sea level.

Also, a way to tell the air pressure is high is to just look for clouds. If there's a system brewing then you know that the pressure is dropping, and if there's not a cloud in the sky then you know that the pressure of the air is high.

They measure the rear axle ratio thus:

The car is put in 1:1 gear (ie third) and brought up to 60mph (according to the rollers, not the car speedo). They then look at the RPM at 6-mph and can thus calculate the rear axle ratio, taking into account different sized wheels and everything.