34066
General Discussion Area / Re: Happy Birthday John (Captain Zok)
« on: 02 November 2007, 10:47:58 »
Happy Birthday 
Kevin
Kevin
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34067
General Discussion Area / Re: 805 BHP BEAST
« on: 01 November 2007, 12:53:37 »
Sorry 
I did warn you 
Kevin
I did warn you Kevin
34068
General Discussion Area / Re: 805 BHP BEAST
« on: 01 November 2007, 12:04:52 »
The argument of power measurements at the wheels versus at the crank opens a huge can of worms whenever it is discussed!
You've hit one of my soapbox subjects now so I can only appologise for what is about to follow
.
The truth is that 200 BHP dissipated in the transmission would kill it very quickly.
The most accurate way to measure an engine's output is to bolt it into an engine dyno which measures the power directly at the flywheel with the engine out of the car. Few people bother because of the cost involved and the time taken to install an engine in a test cell, measure it and then remove it and clean up.
More commonly a rolling road is used because the engine can be tested in the car with only a few minutes of setup time (drive the car onto the rollers and strap it down). You will not get a true figure of engine output by doing this due to losses in the transmission and, more importantly, by the tyres driving the rollers of the rolling road. This isn't such an issue if you just want to make a relative measurement, or to tune the engine for best power because you will be able to see even the slightest relative change in power, but making an accurate absolute measurement is more tricky.
The problem is, people want to go away from a rolling road with a figure to brag about down the pub and that means trying to work back to a figure at the flywheel because that's what manufacturers publish. This can be achieved quite accurately by doing a power run in (normally) 4th gear on a manual (because it's usually the direct gear and therefore the least lossy) up to and normally a little beyond peak power RPM, measuring the torque and speed at the rollers (hence power). The test is then carried out in reverse by declutching and measuring the deceleration of the rollers, wheels and transmission as they slow from the peak RPM speed (which is going to be around 120 MPH or more
). This gives the machine a picture of the losses in the system as the whole thing slows down again, so at any RPM you end up knowing the power at the rollers and the losses between power at the rollers and power at the flywheel. You then need to compensate for the air temperature, humidity and pressure, as this affects engine output on any given day and you have a figure that, if measured carefully, will be within 5% of an engine dyno's figure or manufacturer's claimed output, if that's accurate.
The problem is, if this process is not carried out accurately the result is meaningless. It's meaningless on an automatic car anyway, because the gearing between engine and wheels is constantly changing as the torque converter does its' job and the losses are much greater when the power is on than when the transmission is coasting.
In addition, some rolling roads don't bother with a "coastdown" measurement and just add a completely arbitrary estimate of loss to the measurements at the rollers, often designed to tell the punter what he wants to hear about his engine! They often don't get their rollers calibrated regularly so the basic measurement is not necessarily accurate in the first place!
Don't make the mistake of thinking that power "at the wheels" is more representative of the true power available to you as you drive the car, either. The losses measured here are far greater than the losses experienced when the tyres drive against the ground because on a rolling road the tyres have 2 contact points with the rollers instead of just one against the ground, and the vehicle is often strapped down, putting much more load on the tyre - roller interface than would be present with just the vehicle's weight. Tyre pressure also has a big effect on these losses, and is frequently adjusted when a car is put on the rollers.
In summary, ignore the figure at the wheels completely and hope that the figure at the flywheel was measured with a proper coastdown test. The actual loss through the transmission itself will be much less than 200 BHP. A few tens of BHP at the most, I guess. Most of the losses come from friction between the tyres and rollers, and in distortion of the tyre as it runs on the rollers. They result in heat in the rollers, tyres and the air passing over them, which is why the transmission oil doesn't boil!
Kevin
You've hit one of my soapbox subjects now so I can only appologise for what is about to follow
.The truth is that 200 BHP dissipated in the transmission would kill it very quickly.
The most accurate way to measure an engine's output is to bolt it into an engine dyno which measures the power directly at the flywheel with the engine out of the car. Few people bother because of the cost involved and the time taken to install an engine in a test cell, measure it and then remove it and clean up.
More commonly a rolling road is used because the engine can be tested in the car with only a few minutes of setup time (drive the car onto the rollers and strap it down). You will not get a true figure of engine output by doing this due to losses in the transmission and, more importantly, by the tyres driving the rollers of the rolling road. This isn't such an issue if you just want to make a relative measurement, or to tune the engine for best power because you will be able to see even the slightest relative change in power, but making an accurate absolute measurement is more tricky.
The problem is, people want to go away from a rolling road with a figure to brag about down the pub and that means trying to work back to a figure at the flywheel because that's what manufacturers publish. This can be achieved quite accurately by doing a power run in (normally) 4th gear on a manual (because it's usually the direct gear and therefore the least lossy) up to and normally a little beyond peak power RPM, measuring the torque and speed at the rollers (hence power). The test is then carried out in reverse by declutching and measuring the deceleration of the rollers, wheels and transmission as they slow from the peak RPM speed (which is going to be around 120 MPH or more
). This gives the machine a picture of the losses in the system as the whole thing slows down again, so at any RPM you end up knowing the power at the rollers and the losses between power at the rollers and power at the flywheel. You then need to compensate for the air temperature, humidity and pressure, as this affects engine output on any given day and you have a figure that, if measured carefully, will be within 5% of an engine dyno's figure or manufacturer's claimed output, if that's accurate.The problem is, if this process is not carried out accurately the result is meaningless. It's meaningless on an automatic car anyway, because the gearing between engine and wheels is constantly changing as the torque converter does its' job and the losses are much greater when the power is on than when the transmission is coasting.
In addition, some rolling roads don't bother with a "coastdown" measurement and just add a completely arbitrary estimate of loss to the measurements at the rollers, often designed to tell the punter what he wants to hear about his engine! They often don't get their rollers calibrated regularly so the basic measurement is not necessarily accurate in the first place!
Don't make the mistake of thinking that power "at the wheels" is more representative of the true power available to you as you drive the car, either. The losses measured here are far greater than the losses experienced when the tyres drive against the ground because on a rolling road the tyres have 2 contact points with the rollers instead of just one against the ground, and the vehicle is often strapped down, putting much more load on the tyre - roller interface than would be present with just the vehicle's weight. Tyre pressure also has a big effect on these losses, and is frequently adjusted when a car is put on the rollers.
In summary, ignore the figure at the wheels completely and hope that the figure at the flywheel was measured with a proper coastdown test. The actual loss through the transmission itself will be much less than 200 BHP. A few tens of BHP at the most, I guess. Most of the losses come from friction between the tyres and rollers, and in distortion of the tyre as it runs on the rollers. They result in heat in the rollers, tyres and the air passing over them, which is why the transmission oil doesn't boil!
Kevin
34069
General Discussion Area / Re: Oil Change.
« on: 02 November 2007, 16:46:12 »
It's a 20 minute job on any car once you've done it once 
Kevin
Kevin
34070
General Discussion Area / Re: Bizarre - but is it a crime?
« on: 02 November 2007, 18:49:46 »Quote
you mean you are married and still get allowed sex???
With his bicycle, yes
Kevin
34071
General Discussion Area / Re: Bizarre - but is it a crime?
« on: 02 November 2007, 14:56:35 »
If anyone's breached anyone else's peace it's the workers who walked in on him. He obviously locked the door if they had to use a master key to get in. Why he didn't reply when they knocked I don't know. He could at least have explained that they really didn't want to know what he was doing!
Now, sha66ing Raleighs 'aint most people's cup of tea but it's a bit harsh putting him in the same boat as the kiddy fiddlers, I reckon. What you choose to do behind closed doors is nobody else's business, provided it doesn't hurt anyone.
Defeats the whole object of a sex offender's register if they're going to dilute it like this IMHO.
Kevin
Now, sha66ing Raleighs 'aint most people's cup of tea but it's a bit harsh putting him in the same boat as the kiddy fiddlers, I reckon. What you choose to do behind closed doors is nobody else's business, provided it doesn't hurt anyone.
Defeats the whole object of a sex offender's register if they're going to dilute it like this IMHO.
Kevin
34072
General Discussion Area / Re: Cheap Vx servicing?
« on: 02 November 2007, 11:52:58 »Quote
QuoteStill love to hear about your special tool, unless you've patented it, of course.QuoteQuoteQuoteEven better, come on here, get all the information you need, and do it yourself.
I do, Kev! But not everyone is prepared to lift 2-tonne of metal, crawl underneath on a cold winter's day and get an armload of dirty 10W/40. Sometimes getting someone else to do it seems a good idea!
no need to lift the car if you get a good draining bowl.
On the later engine, If you have my "special tool" you can also change the oil filter from above, should you so desire
http://www.theroto2000.com/
Kevin
34073
General Discussion Area / Re: Cheap Vx servicing?
« on: 02 November 2007, 10:30:37 »Quote
It was more a dig at the bunch over at TB's, for fobbing work off over to us Grin Grin Roll Eyes
I know
Max's barbecue was a bit of a distraction for us Kevin
34074
General Discussion Area / Re: Cheap Vx servicing?
« on: 01 November 2007, 23:34:38 »Quote
I had the priviledge of being the "expert" at the 4pot cambelt party... but somehow got lumbered with a V6 belt change too
That's OK. You're a V6 expert now as well, so you won't be lumbered with anything.
Unless... 2.5TD timing chain, anyone?
I did have it in mind to have one at my parents place near Reading in the summer. Plenty of space there. Was waiting for them to go on holiday and they went away at the same time as I did
Edited to say: I'll drop some hints at the weekend that they need a break...
Kevin
34075
General Discussion Area / Re: Cheap Vx servicing?
« on: 01 November 2007, 23:03:10 »
When you look at what they actually do - service A is basically an oil change and a hoover (plus check a load of items, and no doubt charge you extra for the things they decide to do), sevice B adds spark plugs and air filter. No mention of a cam belt change and they charge you another fiver for oil disposal.
I think DIY is always the best route, or filing that find a local independant who can be trusted.
Worryingly, people might get a "b" service done, assuming it covers everything that needs to be done on a major service and they'll never get a cambelt change
Kevin
I think DIY is always the best route, or filing that find a local independant who can be trusted.
Worryingly, people might get a "b" service done, assuming it covers everything that needs to be done on a major service and they'll never get a cambelt change
Kevin
34076
General Discussion Area / Re: Sky+
« on: 31 October 2007, 23:05:31 »
Not played with one myself but you may well find the output - for some programmes if not all - is protected with macrovision or something on playback meaning you can't make a 2nd generation copy of it.
They'll need to put another downlead in from the dish too, IIRC.
Kevin
They'll need to put another downlead in from the dish too, IIRC.
Kevin
34077
General Discussion Area / Re: Advice please
« on: 02 November 2007, 10:10:09 »Quote
What HD content!?! Grin Wink As you probably know, most is crudely upscaled.
Most stuff on Sky suffers from issues more basic than picture quality, IMHO. The quality of the programme content, the production standards, volume of advertising and even the picture quality of the SD channels is far below what is achieveable, due to the low bit rate allocated to all but the mainstream channels.
So picture quality is actually way down the list as far as I'm concerned. The only thing that interests me about HD is when the DVD format wars die down it'll be nice for watching films.
Kevin
34078
General Discussion Area / Re: Can't get in your car?
« on: 02 November 2007, 09:46:55 »
The frequency at which most car fobs operate is actually shared by a number of users so there's no guarantee of a clear frequency and not much that can really be done in the event of interference. It's actually part of the 70cm amateur radio band so it's quite legitimate for people to be transmitting on or near this frequency (sometimes as they sit in a car park having a chin wag on their radio) at quite high power.
This is compounded by the fact that the receivers built into cars are designed for cheapness rather than performance and are not very good at rejecting interering signals.
The moral of the story is to make sure that your lock cylinder is well greased. You may need it one day!
Kevin
This is compounded by the fact that the receivers built into cars are designed for cheapness rather than performance and are not very good at rejecting interering signals.
The moral of the story is to make sure that your lock cylinder is well greased. You may need it one day!
Kevin
34079
General Discussion Area / Re: Don't stop in London!!
« on: 01 November 2007, 10:35:34 »
The only time I'd consider stopping in central London (or driving there at all) is to leave rubber outside Ken's house when I subsequently pulled away!
That would be worth 8 quid or whatever the congestion charge is these days.
Kevin
That would be worth 8 quid or whatever the congestion charge is these days.
Kevin
34080
General Discussion Area / Re: tunnie becomes a VW driver?
« on: 01 November 2007, 19:45:03 »
Have it delivered directly to the Nurburgring. It'll work out cheaper 
Kevin
Kevin