Rolling Road Results

I'd be up for putting my car on the rollers next year, as they are close to home too, but my car is no longer "std", mainly the 10inch Carhege Cooler and increased boost, both of which can easily be turned off or down to simulate a std car.

Dave mate, I have no interest in getting into another verbal tennis match on this subject. There's so much I could reply to all the "facts" you put about but it all comes down to physics. Air density, pressure vs flow, etc etc etc. You don't need to know about engines to understand the physics behind getting a gas through a hole as quickly and efficiently as possible. And lowering the temperature of a gas increases its mass while keeping the volume constant. In other words, you increase the density. You WILL get more oxygen into the cylinders *without increasing the flow* if you lower the temperature of the charge. THAT is basic physics.

You don't need to know about engines to understand the physics behind getting a gas through a hole as quickly and efficiently as possible.

I always find that lifting one cheek helps

Dave mate, I have no interest in getting into another verbal tennis match on this subject. There's so much I could reply to all the "facts" you put about but it all comes down to physics. Air density, pressure vs flow, etc etc etc. You don't need to know about engines to understand the physics behind getting a gas through a hole as quickly and efficiently as possible. And lowering the temperature of a gas increases its mass while keeping the volume constant. In other words, you increase the density. You WILL get more oxygen into the cylinders *without increasing the flow* if you lower the temperature of the charge. THAT is basic physics.

Martin, seeing as you said doubling pressure doubles flow, I don't think you do....

What physics were you using on the last thread where you said 20% more fuel equals 20% more power and the car makes 360bhp, or that larger oil pumps make better pressure, or the exhaust pressure of one turbo affects the other on a biturbo setup, or you don't need to increase fuel pressure enrichment on boost....etcetera...etcetera...

Engines do not 'know' pressure, they only know flow. They are just a pump with fuel and spark thrown in the mix. If a restriction means this pump can ultimately flow 500cfm for instance, it doesnt matter if we pump in warm air, cold air, treacle or sausage meat, 500cfm is what it will ultimately do....

Tony's car hit the limit at 300 with warm air, if he runs it willl cold air he will hit the limit earlier in the revrange (around 4k most likely) and level out at 300 again (and thats if there is no det)

There about 10 examples of boosted V6s all running those manifolds with wildly varying boost levels, and hitting the same figure within 5 bhp, so I don't know what the argument (or surprise) is???? This was all discussed about 2 years ago...

A610 lump 250 horse standard...... now 297....... all that hassle and cash..... Whatever

Reading with interest - thought I'd put my head above the parapit and chuck in my tuppence worth.

Dont know much about detonation and ignition advance and stuff but I think you are both right. If there is a flow restriction then the volume of air that can enter the engine will ultimately be limited. However, the mass of air that can enter will not be limited - well not until you are pumping liquid oxgen in anyhow, and will vary according to the temperature of that air.

On a basic chemical level, the mass of oxygen (not the volume) that is available to react with the petrol is what will limit horsepower as the petrol will not fully combust if there is insufficient oxgen to combine with the hydrocarbons. So - the greater mass of air that you can get in, the more petrol you can squirt in and thus the more HP you should be able to generate.

That is why your car feels better on colder air - the air is more dense (i.e. greater mass for the same volume) and, given that the engine management system knows the temperature and pressure of that air, it can work out its mass, adjust the fuelling accordingly and squirt more in to achive the correct air to fuel ratio. And more petrol burned usually equals more power out (choosing my words carefully here)

This is also why nitrous works so well - it contains oxygen in a more dense form than air so you can squirt in more fuel and still achive the correct mixture for combustion but get more HP out.

....OK - thats my input over - I'm now standing by the door, ready to get my Coat...

Someone who knows his stuff.

Interstingly, did you know that in the chemical sense, Nitrous actually decomposes in the combustion chamber?

Dave, please show me any third party literature on the subject that proves a power limit regardless of boost when restrictors are placed on an air intake. And by this I do not mean the absolute power limit beyond which any extra energy is wasted just pumping the air through the restriction.

Yes, Dave, doubling the pressure in a sealed container with a restricted oulet will double the flow out of said outlet. The *pressure* in said outlet will indeed be lower because at the point of restriction pressure is lost to flow. Pressure and flow are directly proportional and basically interchangable. In an intake manifold, you have gone past the restriction, the flow slows and the pressure builds once again, though depending on the rate of usage, not necessarily to the same level as prior to the restriction. However since the boost gauge, MAP sensor and wastegate feeds all come off the intake manifold, this is a moot point. The restriction is an obvious inefficiency and should be avoided however.

Well.....Ive been away for three days and look whats gone on!!! Nice figures too.....not really your guarunteed 360 though is it Martin???

Impressive exhuast glow....have you considered wrapping them Tony? May be advantages there.
How long did they spend playing with it? Presumably no trouble with running the flywheel triggered sensor either?

FFS It's not rocket science you know
http://www.grc.nasa.gov/WWW/K-12/airplane/bern.html

FFS It's not rocket science you know
http://www.grc.nasa.gov/WWW/K-12/airplane/bern.html

oh yes it is

FFS It's not rocket science you know
http://www.grc.nasa.gov/WWW/K-12/airplane/bern.html

oh yes it is

Bet Tony feels like Chuck Yeager
Und zeesdiscussion should be readin inda Thich German accent..............

Dont know much about detonation and ignition advance and stuff but I think you are both right. If there is a flow restriction then the volume of air that can enter the engine will ultimately be limited. However, the mass of air that can enter will not be limited - well not until you are pumping liquid oxgen in anyhow, and will vary according to the temperature of that air.

.

I didnt say the inlet amount will be limited, just the amount that will flow through the engine. Like I said before, ignore pressure, its all about flow. If we get so much back pressure in the combustion chamber, and the turbo is spinning at a fixed RPM, the inlet pressure will increase..We not pumping more air 'through' the engine...

Pressure, as most people know, is resistance to flow, nothing more, so if we back up the exhaust will will get an increase in inlet pressure. But its not flowing through the engine, hence its not making more power.

Cooler charge temps WILL increase power (if you are not to the point of max CFM) If we have a standard A610, it will make around 250 intercooled and say 210 non intercooled. But as the manifold restriction puts the limit on 290 odd bhp, then if we run so much boost NON intercooled that we still get the engine up to 290bhp, then cooling the charge will not gain diddly, other than either being able to get the same power at a lower boost level, or at worst, kill the engine, due to the high level of ignition advance you needed to run to get to 290 non intercooled in the first place.

Yes, Dave, doubling the pressure in a sealed container with a restricted oulet will double the flow out of said outlet

Absolutely wrong...

Theres two ways of doubling pressure, which one do you want to bet on?

Either we can restrict the outlet and double the pressure (like kinking a hose) and then LESS water will flow out of the tube - Like I said pressure is resistance to flow - do you know what resistance is.......LESS...If I sealed the end right up I would have massive pressure, diddly flow though, actually none at all - So are you sure doubling the pressure doubles flow...?

..Or the other side of the coin...

Lets pretend we have a fixed diameter outlet, and we PUMP double the pressure through it...

Now....fuel injectors, if we double the fuel pressure to they double in ouput....?

If I turn the fuel pressure up on a fuel pump, what happens to the flow rate...?

If I double the boost on a car, obviously it doubles in power...

Phone a friend, 50/50?

Dave, please show me any third party literature on the subject that proves a power limit regardless of boost when restrictors are placed on an air intake. And by this I do not mean the absolute power limit beyond which any extra energy is wasted just pumping the air through the restriction.

Firstly, I don't see where we were talking about inlet, but if you are talking about my turbo scenario, well here's something you've probably never seen before....a compressor map...!




Now on the left you have the pressure ratio (pr=2 is 1 bar of boost, pr=3 is 2 bar of boost and so on) and at the bottom lb/min of air flow. Now this is mass of air, it makes no basis of whether its hot, cold or marshmallow, a Lb of air is lb of air, much like a ton of feathers is the same as a ton of lead....

The max airflow it can support is 45lb/min, no matter what boost, infact the optimum level is a pr of 2.4, and if you turn the boost up at that point, it falls straight off the map, and at that point turns the air flow energy to over 50% heat, and will actually lose you power, as well as kill the turbo.

Im suprised you havent seen these, theyve been around for the last 50 years or so...

As for examples of inlet restriction, WRC cars run an all manner of different engines, turbochargers, cam profiles etc, but the one common factor is they all run a 32mm restrictor before the turbocharger, and dag-namit!, they all seem to max out at 300bhp, even though the torque and boost levels vary from car to car...

END.

I'd be up for putting my car on the rollers next year, as they are close to home too, but my car is no longer "std", mainly the 10inch Carhege Cooler and increased boost, both of which can easily be turned off or down to simulate a std car.

movin on from grass cutting then

Me again - tin helmet on this time..

Now on the left you have the pressure ratio (pr=2 is 1 bar of boost, pr=3 is 2 bar of boost and so on) and at the bottom lb/min of air flow. Now this is mass of air, it makes no basis of whether its hot, cold or marshmallow, a Lb of air is lb of air, much like a ton of feathers is the same as a ton of lead....

Whats the "T" for in the equation for air flow mass? I think its because the map is based on corrected airflow i.e. the mass of air that would flow assuming air pressure and temperature at sea level on an average day. And hence the mass of air would vary by air temperature? Who knows?

Anyhow - after having just met you yesterday, I aint about to fall out over something that I know little about and have even less practical experience of. So I'll sleep easy knowing that, irrespective of theory, in practical terms, there's a limit to how much power you can realistically get out of an engine by upping boost and cooling the intake temps down.

I'm off to Stansted to see what they make of your engine analyser at the x-ray machine. Should be fun

In the 'corrected' world, the T stands for Stagnated Temperature (but they call it a Standard Day temperature, and pressure at Sea Level. Its an arbitary figure, It doesnt change with flow amount.

In fact, the important part left off that compressor map is the Delta T that increases with boost pressure (as with any gas in a confined space)

As we know, T does not increase with flow, just pressure...