PE Rolling Road Figures 31st Oct 2009

LOL.. I think you have a hole in your bulkhead and your brain has become overloaded with DERV fumage.

"then it would produce readings more true to the way the car performs on the road.".. They have already created a dyno just for that, it's called a variable load dyno.

There are effectively 2 types of dyno - Inertia (as seen at the weekend and common place) or Variable Load (not so common but they do exist).

From memory, with a variable load dyno you can do 0-60 runs / quarter mile runs and so on.. But whilst it's the closest you can get to getting a "way the car performs on the road" idea, it will still always fall short of any real useful analysis. It won't take into account / climatic conditions (cold air is denser and when sucked through the intake helps performance, hence why we all love the damp cold winter mornings) / wind resistance / ground conditions / tyre degradation (for grip) and most importantly fluctuating car (and passenger(s)) weight. I have a 60 litre fuel tank in my GT and to visualise how much a full tank weighs, picture 30 X 2 litre bottles of coke.. That's a shit load of weight, weight that will change when you're using fuel.

So in reality there is nothing out there, that can ever accurately give us a magic figure of anything whatsoever, that we can apply to how our car would perform on the road.

We can only ever go on engine power figures, quarter times, power to weight ratios and brag about them accordingly :)
 
essNchill said:
LOL.. I think you have a hole in your bulkhead and your brain has become overloaded with DERV fumage.

"then it would produce readings more true to the way the car performs on the road.".. They have already created a dyno just for that, it's called a variable load dyno.

There are effectively 2 types of dyno - Inertia (as seen at the weekend and common place) or Variable Load (not so common but they do exist).

From memory, with a variable load dyno you can do 0-60 runs / quarter mile runs and so on.. But whilst it's the closest you can get to getting a "way the car performs on the road" idea, it will still always fall short of any real useful analysis. It won't take into account / climatic conditions (cold air is denser and when sucked through the intake helps performance, hence why we all love the damp cold winter mornings) / wind resistance / ground conditions / tyre degradation (for grip) and most importantly fluctuating car (and passenger(s)) weight. I have a 60 litre fuel tank in my GT and to visualise how much a full tank weighs, picture 30 X 2 litre bottles of coke.. That's a shit load of weight, weight that will change when you're using fuel.

So in reality there is nothing out there, that can ever accurately give us a magic figure of anything whatsoever, that we can apply to how our car would perform on the road.

We can only ever go on engine power figures, quarter times, power to weight ratios and brag about them accordingly :)
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:D
 
essNchill said:
LOL. So in reality there is nothing out there, that can ever accurately give us a magic figure of anything whatsoever, that we can apply to how our car would perform on the road.
Click to expand...

What's funny? I know. That's what I'm saying. Wouldnt it be good if they built a weigh bridge into the dyno that could work it out as close as possible, and combine the two types of dyno via this varriying resistance roller.

Getting a little annoyed at people telling me I'm talking rubbish and am high when they're not actually reading what I'm saying :rolleyes:. Maybe I'm just not explaining what I mean clearly enough because your replies Shaun seem to me to be on a tangent different to what I'm discussing.
 
essNchill said:
From memory, with a variable load dyno you can do 0-60 runs / quarter mile runs and so on.. But whilst it's the closest you can get to getting a "way the car performs on the road" idea, it will still always fall short of any real useful analysis. It won't take into account / climatic conditions (cold air is denser and when sucked through the intake helps performance, hence why we all love the damp cold winter mornings) / wind resistance / ground conditions / tyre degradation (for grip) and most importantly fluctuating car (and passenger(s)) weight.
Click to expand...

The dynojet dynos use that system. When i had mine done he mentioned you could do 1/4 mile sprints on it. Any SAE figures take into account alttitude, temp and humidity and are corrected accordingly. Before being corrected mine was 162whp....this unfortunately dropped to 158 after SAE.

I think the only true measure of a cars power/performance is a 1/4 mile run.....but then people start moaning about traction, track conditions, car weight etc...........so you just cant win!!!
 
rowdy-GTi said:
I think the only true measure of a cars power/performance is a 1/4 mile run.....but then people start moaning about traction, track conditions, car weight etc...........so you just cant win!!!
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Definitely agree with that :).

A dyno dynamics roller also has climatic correction. You'll see in the graphs that air pressure, temp etc is listed and it uses similar calculations no doubt. It seems to me they simply havnt perfected the rolling road yet but it looks like dynojet take more factors into the equation than the dyno dynamics ones then.
 
Well anyone who races with excess weight in the car is basically just denying free power anyway, so thats their own fault!
Joe
 
Ok ok, best example is my car/turbo car. The engine only produces full boost underload right? You can sit there all day long and rev the nuts of it in neutral and it'll probably only boost 5psi max. But on the rollers how do you know that the amount of load put on the engine is the same that is put into it on a real road?? You don't, and the roller cannot replicate those conditions without knowing the weight of the car. Else the engine is working under different load conditions and possible acting differently. If it did know then it could take the weight and use some algerithm that created the correct resistance on the rollers to be able to replicate the weight of the car/the load normally put on the engine.

Hopefully that's cleared up what I'm banging on about :lol:
 
I get that completely.
In theory, the Dyno should weigh the car and place the relative amount of resistance against the wheels during the run, to produce an accurate power curve etc..
Joe
 
I never argued against that lol, I'm a firm believer that the dyno's load should be relative to the car's weight.. None of this Shoot_4 fixed load bollocks.
I guess I'll be judging my power figures using the Ass dyno in future lol, fuck paying for some jew to rev your car up a bit and tell you its got shit power haha
Joe
 
No I know Joe, I'm just thankful that someone agreed with me on that finally after being told I was rammbling.

Haha, Ass dyno :D and magic tree g-meter. That's where it's at.
 
Don't know Paul but the evidence is there that it reacts differently underload.
 
edk said:
What's funny? I know. That's what I'm saying. Wouldnt it be good if they built a weigh bridge into the dyno that could work it out as close as possible, and combine the two types of dyno via this varriying resistance roller.

Getting a little annoyed at people telling me I'm talking rubbish and am high when they're not actually reading what I'm saying :rolleyes:. Maybe I'm just not explaining what I mean clearly enough because your replies Shaun seem to me to be on a tangent different to what I'm discussing.
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I've always understood what you're saying Ed, I'm not one of the bad guys. All I've done is try to point out that, the whole weight thing doesn't come into it on an inertia dyno and even if it could somehow be done, it wouldn't count for shit anyways, as there are just too many variables when in the real world and on the road.

I think I said in an earlier post that the only way of measuring an engines power, is with it removed from the car and sat on a bench, far from ideal yeah but it would be the only true measurement and that doesn't involve weight either.

As car drivers / owners, we will never get an accurate measurement, which is why I'm never been a fanboy of dynos.

Google hydraulic dynos, that's almost what you may be looking for? But from what I've just read, they're pretty unpopular due to setup and all of that but they do offer some good and different analysis, over an inertia dyno.

I only got involved here to comment on the weight statements and try to explain it, as I thought it may help or educate.. It was deffo not intended to make you look like a muppet, so please don't take it that way.. I love you man!!
 
Hehe that's cool man :) Love you too!

I agree it would be very difficult to get an accurate reading for sure, but I think if they did take into account weight it would be another step to getting closer to an accurate reading, is all I'm saying :). I don't think it wouldnt count for anything.
 
yeah it wouldn't count for anything cani never no 1/4 mile runs or 0-60mph dash on a dyno, so why bother to enter the vehicle weight. i wanna see a car launch whilst strapped down on the dyno and expect the car to not jump out the rollers. no point even do an in gear acceleration as that’s about as important as errrrrrn this thread. Example ed/jess’s car in 5th @ 30mph will get to 60mph quicker than and evo 9 however it means........................

Good question Paul too. The engine is under load when its in gear driving on the road and there’s a resistance to rev. the engine then to overcome this resistance works harder achieving full boost. Same for dervs & pervs lol

whp on a reputable setup and be done
dd
 
David forget this 1/4 mile run nonsense you're on a tangent now. Launching on rollers? wft? Hush now. I'm talking about creating a real load on the wheels in conjuctuction with a normal power run :).
 
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