Dodge Viper GTS on the rollers
Discussion
Steve
I have never claimed accuracy, I don't know what that is? I stand by the repeatability of testing NA on our Dynocom so we can see before and after effects and even year on year differences. Turbos are harder as the power varies so much with intake temp. As I keep saying, the rollers are a good tool.
Not sure if the SF901 we have will be accurate? As Stan said the CFs are all different, indeed the SF manual explains why power will vary depending on test mode. Hold power at X rpm will show more than transient testing which loses some to inertia and spinning up the rotating masses.
What one needs is repeatable figures taken in the same way which means chopping from one dyno to another is a waste of time re power figures but good idea if operator isn't able to cope with the car one wants to run!
In the real world it is sorted on the track, but hp isn't all is it? Car prepping, driver skills, financial input, Lady Luck etc etc one can't get rid of all the independent variables to see best power!
I hate to say it, but, if I hadn't dynoed the Viper and posted the figures, this thread may not have happened, no one would be any wiser as to whether Carls 1000 and 1500 hp claims were realistic or bull
As it is, lots of interesting input esp from AW111.
Peter
I have never claimed accuracy, I don't know what that is? I stand by the repeatability of testing NA on our Dynocom so we can see before and after effects and even year on year differences. Turbos are harder as the power varies so much with intake temp. As I keep saying, the rollers are a good tool.
Not sure if the SF901 we have will be accurate? As Stan said the CFs are all different, indeed the SF manual explains why power will vary depending on test mode. Hold power at X rpm will show more than transient testing which loses some to inertia and spinning up the rotating masses.
What one needs is repeatable figures taken in the same way which means chopping from one dyno to another is a waste of time re power figures but good idea if operator isn't able to cope with the car one wants to run!
In the real world it is sorted on the track, but hp isn't all is it? Car prepping, driver skills, financial input, Lady Luck etc etc one can't get rid of all the independent variables to see best power!
I hate to say it, but, if I hadn't dynoed the Viper and posted the figures, this thread may not have happened, no one would be any wiser as to whether Carls 1000 and 1500 hp claims were realistic or bull
As it is, lots of interesting input esp from AW111.
Peter
Stevie
Still not same as posting that graph as tested though I am sure if you visited NMS and had a two wheel drive we would try and do a few pulls for you which are nice to have as a record and see power delivery curve.
Peter
Stan
When I get some spare time I'll have a look. It must be in there somewhere as I can display bhp/Torque Vs time. To be honest my main concern is to get as much bhp and torque everywhere so I only tend to look at overlays. You have to remember I use this as a tool to earn a living and would get bogged down if I spent hours and hours going through all the figures for every car.
Peter
Still not same as posting that graph as tested though
I am sure if you visited NMS and had a two wheel drive we would try and do a few pulls for you which are nice to have as a record and see power delivery curve.Peter
Stan
When I get some spare time I'll have a look. It must be in there somewhere as I can display bhp/Torque Vs time. To be honest my main concern is to get as much bhp and torque everywhere so I only tend to look at overlays. You have to remember I use this as a tool to earn a living and would get bogged down if I spent hours and hours going through all the figures for every car.
Peter
Edited by PeterBurgess on Saturday 30th May 06:55
Hi Stan
Is that data you showed taken from an engine dyno?
Robert
Looks like you find what we find too about losses, ideal for comparison work, good feedback and interesting graph.
I made a muck up the other day, with the pau switched on I did a pure inertia run, absolutely crap curve and numbers! I was a little red faced but customer happy when I redid the testing 'properly'
The Rototest graph just goes to show the difficulty of trying to compare Manufacturers claimed flywheel figures with Rototest at the hub measured figures.
Peter
Is that data you showed taken from an engine dyno?
Robert
Looks like you find what we find too about losses, ideal for comparison work, good feedback and interesting graph.
I made a muck up the other day, with the pau switched on I did a pure inertia run, absolutely crap curve and numbers! I was a little red faced but customer happy when I redid the testing 'properly'
The Rototest graph just goes to show the difficulty of trying to compare Manufacturers claimed flywheel figures with Rototest at the hub measured figures.
Peter
Hi Stan
When we get the SF901 running and we do something interesting we'll give you the info you want. I fear chassis dyno info would be too messy
I thought the Rototest stuff was showing a population distribution based on testing 404 engines with most common -10% to -4% off the Manufacturers figures? With some 24 engines being 14% different from claimed?
Peter
When we get the SF901 running and we do something interesting we'll give you the info you want. I fear chassis dyno info would be too messy
I thought the Rototest stuff was showing a population distribution based on testing 404 engines with most common -10% to -4% off the Manufacturers figures? With some 24 engines being 14% different from claimed?
Peter
Edited by PeterBurgess on Saturday 30th May 18:30
I have always advocated repeatability as the main importance for my rolling road, I appreciate the £26000 I have invested is a mere pimple on the bottom of what manufacturers would spend but I am 'chuffed' how repeatable the figures are that we achieve.I prefer running inertia tests whenever possible, this keeps temps down and adds to repeatability. Once done we hold the load for as long as necessary to check for detonation (although I must say the inertia tests show power drop rapidly with onset of det) and at times to check fuel supply is sufficient for endurance use such as track racing. Also testing radiator/heating problems.
The SF901 will be commissioned the same as Lister Storm Racing had it (24 Hour Le Mans use) so we can, if required, run flat out without overheating engine or cooling for dyno. This requires massive water tank!
Peter
The SF901 will be commissioned the same as Lister Storm Racing had it (24 Hour Le Mans use) so we can, if required, run flat out without overheating engine or cooling for dyno. This requires massive water tank!
Peter
Sounds similar to Lubrizol, we had a visit around 1992 and were impressed with the test facilities. The granite 'room' was cool They were running and stripping to check for wear, or lack of it! Seemed like a waste of engines, but just part of a big business with big business deep pocket!
My friend did a wear rate test on an old step thru Honda Plag many years ago, held a finger near the carb mouth with knob of grinding paste....engine went aaaaaaaaaaaaaaaaaaaeeeeeeuuuuuuuuUMP and stopped in about twenty seconds
Peter
They were running and stripping to check for wear, or lack of it! Seemed like a waste of engines, but just part of a big business with big business deep pocket!My friend did a wear rate test on an old step thru Honda Plag many years ago, held a finger near the carb mouth with knob of grinding paste....engine went aaaaaaaaaaaaaaaaaaaeeeeeeuuuuuuuuUMP and stopped in about twenty seconds
Peter
That's interesting, with an endurance test must be pretty nasty (powerful) isotopes or the isotope would decay fast as in isotopes used in humans for x-ray purposes. Do the isotopes vary much in half life? Must be very tight safety requirements....to think they used to let us loose with radioactive mono-directional sources in physics
Peter
Peter
In the real world, as I understand it from Carl and reading what Steve says (he mentions wheel spin at 190mph in certain conditions), the problem is having more power than the tyres can handle, so it is a balancing act of getting as much power down to the wheels without wheels spinning. This would mean than Stan and Dave's maths is working out, more or less, what power is being delivered to the ground in terms of the speeds and accelerations achieved, it cannot work out what the flywheel horsepower is if full throttle cannot be/isn't used. It can only work out what power at the wheel would be required to accelerate the cars in the stated times within certain guesstimated parameters. Carl said the Viper was bloody fast in stage 1 guise and in stage 2 just spun the tyres with any real throttle applied!
Peter
Peter
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