Just how accurate are dynos - rwhp not fwhp
Discussion
Last weekend we all used a single dyno as a good base line. Same conditions for everyone but a few days prior to the dyno day two members had cars run with around 90bhp MORE than what was recorded at Vixpy's.
One is FI (with belt slip) the other is NA with CAM so that should eliminate belt slip. I'm curious as to how there is such a big difference, even atmospheric differences could surely not account for such a difference? I believe both systems are dynodynamics so should be pretty much similar
How come then such a difference could occur?
One is FI (with belt slip) the other is NA with CAM so that should eliminate belt slip. I'm curious as to how there is such a big difference, even atmospheric differences could surely not account for such a difference? I believe both systems are dynodynamics so should be pretty much similar
How come then such a difference could occur?
I remember charlie saying the air conditions could have accounted for ~10BHP down on the day.
For sure tyre pressure etc can have an affect, as can tyre slip and on my motorbike even whether the chain was oiled properly or not! Previously my bike kicked out 157BHP at the wheels on one dyno and 175BHP on Crescent Suzuki's...As has been said before, few dynos will give the same result and some dynos are more likely to tell the customer what they want to hear, not always the reality.
I think the SRR day was great, just to get everyone on the same dyno at the same time for some comparative results!
I'm just hoping my engine keeps the map change Paul Spinks did after my run to get me back those few degrees of advance and see if I can get nearer 500RWHP the next time...
For sure tyre pressure etc can have an affect, as can tyre slip and on my motorbike even whether the chain was oiled properly or not! Previously my bike kicked out 157BHP at the wheels on one dyno and 175BHP on Crescent Suzuki's...As has been said before, few dynos will give the same result and some dynos are more likely to tell the customer what they want to hear, not always the reality.
I think the SRR day was great, just to get everyone on the same dyno at the same time for some comparative results!
I'm just hoping my engine keeps the map change Paul Spinks did after my run to get me back those few degrees of advance and see if I can get nearer 500RWHP the next time...
Edited by paramoreg on Monday 6th April 22:29
Vixpy puts my loss down to the change of differential ratio, and after taking the car off the dyno suggested we should have run it in 3rd rather than 4th gear (which with the change of diff ratios would have given the same combined gearing we ran before the change of diff ratio). Paul had his laptop logging during the session and confirmed the car was running identically to the last time it was run at 0.85bar, so shes in good health. That's all I know from Saturday.
Incidentally, when we ran the 836rwhp session at 1.1bar, it was with the changed diff ratio. At the time we didnt run at 0.85bar run to verify whether the diff change had changed rwhp output since the original 0.85bar run. With hindsight it would have been sensible to do that, and then run the 1.1bar runs to compare. What I do remember thinking was that we had to raise the boost level more than I thought we would need to in order to hit that mark. Perhaps indicating that the starting point was lower (as per Saturday).
Has it "lost" anything? Only way to tell would have been to turn up the boost level on Saturday to 1.1bar and see if she still made 836rwhp. I wasnt keen on that ahead of vmax given we had one instance of clutch slip last time we ran at that level.
I can say she feels no different on the road that's for sure. Of most interest to me is how she performs at Brunters later this month at vmax. I'm looking forward to that.
Incidentally, when we ran the 836rwhp session at 1.1bar, it was with the changed diff ratio. At the time we didnt run at 0.85bar run to verify whether the diff change had changed rwhp output since the original 0.85bar run. With hindsight it would have been sensible to do that, and then run the 1.1bar runs to compare. What I do remember thinking was that we had to raise the boost level more than I thought we would need to in order to hit that mark. Perhaps indicating that the starting point was lower (as per Saturday).
Has it "lost" anything? Only way to tell would have been to turn up the boost level on Saturday to 1.1bar and see if she still made 836rwhp. I wasnt keen on that ahead of vmax given we had one instance of clutch slip last time we ran at that level.
I can say she feels no different on the road that's for sure. Of most interest to me is how she performs at Brunters later this month at vmax. I'm looking forward to that.
Harryoz said:
Only way to tell would have been to turn up the boost level on Saturday to 1.1bar and see if she still made 836rwhp. we had one instance of clutch slip last time we ran at that level.
That could explain why a `1000` HP clutch let go at 1017HP.
(And give me peace of mind as its the same as mine)
Harryoz said:
Vixpy puts my loss down to the change of differential ratio, and after taking the car off the dyno suggested we should have run it in 3rd rather than 4th gear (which with the change of diff ratios would have given the same combined gearing we ran before the change of diff ratio). Paul had his laptop logging during the session and confirmed the car was running identically to the last time it was run at 0.85bar, so shes in good health. That's all I know from Saturday.
Incidentally, when we ran the 836rwhp session at 1.1bar, it was with the changed diff ratio. At the time we didnt run at 0.85bar run to verify whether the diff change had changed rwhp output since the original 0.85bar run. With hindsight it would have been sensible to do that, and then run the 1.1bar runs to compare. What I do remember thinking was that we had to raise the boost level more than I thought we would need to in order to hit that mark. Perhaps indicating that the starting point was lower (as per Saturday).
Has it "lost" anything? Only way to tell would have been to turn up the boost level on Saturday to 1.1bar and see if she still made 836rwhp. I wasnt keen on that ahead of vmax given we had one instance of clutch slip last time we ran at that level.
I can say she feels no different on the road that's for sure. Of most interest to me is how she performs at Brunters later this month at vmax. I'm looking forward to that.
Yes, spot on to my theory, To gain just 90bhp when we did the big power runs we had to turn the boost up .25 Bar of boost, when really we should have only had to turn it up slightly, only the diff an explain this and really it should have been run in 3rd then and on Sat, which is my fault I'm afraid. Sorry chaps Incidentally, when we ran the 836rwhp session at 1.1bar, it was with the changed diff ratio. At the time we didnt run at 0.85bar run to verify whether the diff change had changed rwhp output since the original 0.85bar run. With hindsight it would have been sensible to do that, and then run the 1.1bar runs to compare. What I do remember thinking was that we had to raise the boost level more than I thought we would need to in order to hit that mark. Perhaps indicating that the starting point was lower (as per Saturday).
Has it "lost" anything? Only way to tell would have been to turn up the boost level on Saturday to 1.1bar and see if she still made 836rwhp. I wasnt keen on that ahead of vmax given we had one instance of clutch slip last time we ran at that level.
I can say she feels no different on the road that's for sure. Of most interest to me is how she performs at Brunters later this month at vmax. I'm looking forward to that.
In answer to the question, I expect to see no more than 10bhp variance on a 500bhp car over the coarse of a year, or over the coarse of 2 DD dynos, if everything is done properly, in shootout modes and with the atmospherics set up properly, and of coarse if the car is working properly
Bonnie and Clyde said:
Vixpy1 said:
stigmundfreud said:
cheers Chri.... Charlie
Don't you even start with that again Edited by Vixpy1 on Tuesday 7th April 01:10
Vixpy1 said:
Bonnie and Clyde said:
Vixpy1 said:
stigmundfreud said:
cheers Chri.... Charlie
Don't you even start with that again
Cos he sent me threatening emails
Edited by Vixpy1 on Tuesday 7th April 01:10
No seriously whyVixpy1 said:
In answer to the question, I expect to see no more than 10bhp variance on a 500bhp car over the coarse of a year, or over the coarse of 2 DD dynos, if everything is done properly, in shootout modes and with the atmospherics set up properly, and of coarse if the car is working properly
Shootout mode explained:
"Chances are, many of you from around the automotive industry have already heard of the ShootOut system when dyno tuning cars. Dyno Dynamics, the manufacturer of Australia’s leading dynamometer brand, has for many years been considered the benchmark for both accuracy and repeatability. Now, after 4 years of effort (not to mention a substantial financial investment), they have just ‘upped the stakes’ - Dyno Dynamics has developed a system that is set to become the industry standard for power comparison. The system is called ShootOut, it is being utilised by a network of accredited Dyno Dynamics equipped workshops across Australia and will soon be available to all customers worldwide.
The ShootOut mode system is not just a hardware or software upgrade – it is a standardised approach to power measurement, designed to ensure that you can take your car to any accredited workshop and get accurate power measurements for your car. The results will be the same regardless of which ShootOut mode accredited workshop you select. This also means that results from different cars, measured on different dynos can be compared much more accurately which opens a lot of insight to power readings.
ShootOut was developed by Dyno Dynamics primarily to eliminate "Operator Technique" and as a tool for measuring horsepower accurately and CONSISTENTLY for ALL Dyno Dynamics dynos with Shootout accreditation. All dynos with Shootout accreditation have been calibrated the same accross the board, and should not vary more than 1% when comparing between Dyno Dynamics dynos.
Ethical standards
All ShootOut workshops must abide by a code of practice. When a company gets its ShootOut accreditation, it is only leasing the right to use the ShootOut mode and the ShootOut logos on the dynos, which are bgasically the physical and interlectual property of Dyno Dynamics. We are bound by a contractual agreement which is renewed on a yearly basis with very strict guidelines and procedures whenever we use the ShootOut logos on printed dyno graphs. If a company does not adhere to these guidelines, and decides to employ "Operator Techniques" and manipulate the ShootOut process, Dyno Dynamics will issue the company with a warning. After 3 warnings, the company loses their ShootOut Accreditation. Dyno Dynamics expect Dyno Operators to be honest and follow the required procedures in accordance with the ShootOut Agreement between the operator and Dyno Dynamics.
Proof of integrity
1. All ShootOut graph runs must be supervised by an accredited ShootOut scrutineer.
2. When the Shootineer is confident that the run has been performed to Dyno Dynamics’ ShootOut standards, the approved ShootOut logo will be added to the graph.
3. Test conditions and other data is printed on the lower edge of the graph as further evidence of accuracy.
4. When the graph is printed, the Shootineer will apply the official ShootOut stamp and personally sign it.
5. As final proof, the customer is provided with a checklist to verify that all steps in vehicle preparation for the test have been carried out correctly.
Whether you are planning on attending a ‘head to head’ dyno day, or want your vehicle tested to verify the effects of a performance enhancement – A Dyno Dynamics ShootOut accredited workshop will determine the figures accurately, time after time, regardless of location.
"
Think I was down ~7hp on the day - and since Vixpy told me it was identical to last time, I don't really care. I took my old graph out when I got home and it is identical. I mean, exactly the same!
Same on the road (like anyone could tell 7hp!).
Look forward to some more mods now after driving Roger's demo (damn you man!)
Same on the road (like anyone could tell 7hp!).
Look forward to some more mods now after driving Roger's demo (damn you man!)
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