Hi HSE2
I just put the Monsta Torque Dyno numbers up for discussion to get back to talking about Sprint's, actually it seems a bit low to me for a Hub Dyno number, but I certainly don't doubt Fords 400 kW number.
Printable View
Hi HSE2
I just put the Monsta Torque Dyno numbers up for discussion to get back to talking about Sprint's, actually it seems a bit low to me for a Hub Dyno number, but I certainly don't doubt Fords 400 kW number.
Come on now, you cant accurately measure slip losses....
Yes it may occur but its neither linear or consistent through a run.
It's flawed logic to even try to estimate them because there's simply no way to know when and if there is any.
Yes it's better if the slip can be measured across the rev range rather than at the end, which is what I've been able to do with some dyno sheets and I do that when I can (ie. when the engines true revs and the Dyno's true roller speed is displayed, then you can work out how much speed is missing).
Now with that approach, I've noted a bit more slip at the maximum torque and maximum power points which is what would be expected, because there is more tractive effort/motive force at those points, I've found up to about 1 or 2% more slip, and that should actually make my cars maximum power estimates a bit conservative (I like that idea).
But when you can't do that and you can only work out speed losses at the end of the run, it's clear to me that you can still get a pretty good idea of how much speed is missing, and work out a fairly accurate slip power loss from that.
Interestingly when I take the tractive effort figure of what looks like 3.92 kilo Newtons that my 262 kW Dyno Dynamics sheet shows at the cutout point (at around an indicated 223 km/h or 61.9444 metres per second roller speed in 4th gear) and I calculate power from this (3.92 kilo newtons multiplied by 61.9444 metres per second), I end up with the 242.8 kW power figure that the power graph also shows at the cutout point, which is as it should be. But I know the cutout wheel speed would have been about 5% above that, so from that I can calculate a pretty accurate true cutout power figure of practically 255 RWKW. Add 50 kW losses to that, and it's looking like around 305 Flywheel kW for a breathless engine at the cutout point. Still a good number I suggest.
Personally I'm thinking that ignoring slip when you can get a good idea of what it is, seems to be the floored approach.
I've found that taking slip into account can go a long way to explaining varying Dyno results from the same car.
Then you also need to take into account:
Tyre diameter
Tread depth (age of tyre)
Tread compound
Centrifugal impact on tyre diameter (tyre will grow with revs).
Tyre presure
Strapping force.
Far too many variables to get an accurate estimation of slip
I've actually done quite a bit of research on the effect of tyre wear, load and pressures because for years I lived near a Government marked 1000 metre section and I was amazed by how minimal the changes were. I checked with different pressures, loads and new VS worn out tyres. I've come to think of a steel belt as being like a conveyor belt that has to cover a certain distance no matter what shape the tyre is. That's not to say that there won't be any changes but surprisingly little.
You did mention tyres growing at higher revs and I've heard that too, but given that I worked out my 4th gear speed from the known 3rd gear cutout speed at WSID, I'm thinking that would only make my true 4th gear power figure higher.
Strapping force? Yes that can sometimes reduce power a bit but if it's more than necessary it should only make the power figure lower than it really is, or if it's not enough then there will be more slip which can be measured. I should mention too that I've seen the effect of really tying my last car down tight to get rid of slip and it didn't have much effect, the car was still getting practically the same speed loss and the power figure hardly changed.
There are other variables too, but if a car has a certain tractive force and you can find out the correct speed, then you can say it is at least making a certain amount of power.
Surely you are going to be a lot better off than if the slip is ignored, and I've seen up to about 12% slip on Dyno's.
Yes that's true but it's generally not recommended. A Miami sedan will run up to 390 ~400 rwkw tune only and will make the same with a Tune + Cat back, but the freely flowing exhaust will allow it to do it with less boost. Which equals less heat and less pressure and is much easier on the engine. In fact one tuner here in melb is not keen on running those numbers without a high flow exhaust.Quote:
Originally Posted by 4Vman
I was also chatting to a owner of a 335 Miami powered GTE. He had a Herrod intercooler fitted. Std exhaust and tune, he said it has made an incredible difference in that without the heat build up it was like driving it on a 10 degree day all the time.
No one is interested in debating slip level.
The thing about numbers is it cancels out provided you have enough data.
You waste so much time and effort trying to understand stuff that just doesn't matter.
The numbers, in the case of the sprints have been given to us. They are not a mistake and they are from the same manufacturer. The same manufacturer means you can rule out inconsistencies in the numbers.
The bottom engine is the 270. It DOES NOT have a TOB addition of more than 20kws. This is a fact.
The middle engine is the 310. It DOES NOT have a TOB Addition of more than of 25kws.
The top engine is the 325. It does have 370 and a 45 TOB number because the same engine manufacturer says so.
Attempts to reverse engineer the numbers to come to different conclusions is comical.
Until Sprint, Miami enjoyed the highest TOB addition thought to be about 40 kws. To even image any of the turbos matched that number back before its develop is extremely naive.
It is only the development of cars post Miami that exceed that number.
Those being in order, GTF, SPRINT 6 and SPRINT 8
That is the bottom line.
Makes sense Mr Elks, thankyou, noted.
TBH I would be doing the cat back or otherwise at the later stage to change the "cackling" to a improved burble/note so to speak.
not trying to be argumentative but somewhere along the way, Ford started quoting figures more in line with rwkw figures rather than flywheel though. do you know when exactly this happened and is it only for the miami?Quote:
Originally Posted by HSE2
No, what happened is TOB clouded the final rear wheel number.Quote:
Originally Posted by prydey
Now with a far larger sample size from dyno's we can see what the impact of TOB is on the rwkw number and estimate the driveline loss at about 70kw.