OK, it would appear that the contentious issue of rolling roads is due another discussion Everyone thinks their local RR is the best and most accurate and all others are full of crap... tis the nature of the beast I guess In my experience I have found most rollers to be fairly closely matched with fly figures i.e. both torque and bhp. I'll dig out some examples later...

Discuss

my experience is similar, but its the wheel figures that are close.

The fly figures tend to vary quite a bit.

Flea - you've experienced the same - PowerStation have you at 480bhp and Perfect Touch at 420, but the wheels figures are rather closer together than 60bhp.

As many people have said before, fly figures are always calculated. Some calculations are more accurate than others, some are great for the pub. I seem to recall that G-Force in Aylesbury set a hopelessly optimistic transmission loss of 25%, which gave some very healthy looking fly figures, but meant zip in the real world.

True Nigel,
that's why it would be nice to be all discussing @wheel figures rather than the "carefully/accurately" guestimates of the flywheel figures!

V.

The only problem with discussing only @wheel figures is that due to varying ambient temps, you're still not comparing like with like ...

Yes, agree with Nigel.. Fly figures can vary quite a bit, but at wheels figures tend to be the same, this is because most RR's measure torque at wheels, so easy to calcualte bhp@ wheels, its then extrapolation or transmission estimation to give flywheel figures.

I've done back to back with

PTS, G-force, and Power Engineering, they all gave the same figures +/- 5bhp

Joe

Wheel figures are not always the same at all!!

Nigel what were your wheel figure at PTS and Powerstation when you ran 300bhp @ fly at both of them?

There are a number of factors, such as heat soak as well as the ones David had pointed out (ambient temperature etc.)

Perhaps we should all join in on Nigels RR day and get this matter sorted out once and for all?!

1. Everyone should have their engines removed and go to somewhere that has the same number of dynos as the engines to be tested.

2. They should all be tested at the same time to allow for changes in ambient temps.

3. Each tester must be blindfolded to remove any favouritism.

4. These results should then be handed over in a lightless room into a box.

5. People should be identified by a number only.

6. The people who hand out the results must then be killed after delivery.

And then there'd still be bloody arguments about sodding bhp figures between the participants - maybe their dyno was nearer the window and was 0.0000000001 C cooler.

Jayell,

of course all engines would be fed through the same fuel tank with the right number of welbro (sp?) pumps and a fuel pressure meter on each engine to make sure that noone gets more fuel than the other. Obviously care must be taken for equal lengths of fuel pipes to each engine.

Other than that, I agree although there may be a few implementational difficulties, i.e. killing the testers could be slightly problematic, but I'm sure you'll find a feasible solution.

* makes a few adjustments to my list of required criteria *

First off… not all rolling roads work the same. The loading they put through the rollers, the friction with the tyre base, gearing, rpms ALL effect wheel power!! It is a not a black and white uniform formula and all need calibrating accordingly.

Powerstation do NOT in my experience inflate fly figures and anyone who has remarked this has no experience, information or technical knowledge about their rollers or why they believe it to be the case! Let’s look at the FACTS…

The following coupes have all been run at Powerstation over the last 2 or so years:

Scooby (standard) – 227bhp & 222lbs/ft
(171bhp @ wheels = 25% losses)

Nobby_B (modded) – 305bhp & 285lbs/ft
(232bhp @ wheels = 24% losses)

Jimbo (modded) – 278bhp & 252lbs/ft
(194bhp @ wheels = 30% losses)

Jap (modded) – 265bhp & 251lbs/ft
(196bhp @ wheels = 26% losses)

James_H (modded) – 288bhp & 254lbs/ft
(207bhp @ wheels = 28% losses)

MC_Mike (modded) – 274bhp & 262lbs/ft
(202bhp @ wheels = 26% losses)

Nigel (modded) – 302bhp & 246lbs/ft
(191bhp @ wheels = 36% losses)

Flea (modded) – 360bhp & 323lbs/ft
(287bhp @ wheels = 20% losses)

Flea (modded) – 480bhp & 367lbs/ft
(358bhp @ wheels = 25% losses)


Anyone seeing a pattern here? Excluding my “fantastic” figures which have the lowest transmission losses, do any of these other coupes have inflated figures for their mods? A standard coupe makes standard power… surprise! The hybrid turbo cars make hybrid power… surprise! The GT28R for Nigel’s setup makes 300bhp… hmmm, seen that somewhere before! The wheel power is low due to the type of rollers but the fly power is just right

So what about PTS…

Flea (same mods as above) – 360bhp & 309lbs/ft
(306bhp @ wheels = 15%)

Nigel (modded) – 305bhp & 256lbs/ft

James_H (modded) – 288bhp & 281lbs/ft

Once again these fly powers are looking strangely familiar…

The reason I use Powerstation is purely because it is my nearest RR allowing me to get a cold run with wideband fueling check. DoctorFrag always gets a cold run too done the following morning after a mapping session at PTS… this produced an extra 15bhp last time which is great!

When Barbz had his 2 litre engine mapped at Owen Developments it produced 386bhp & 346lbs/ft (306bhp @ wheels = 20% losses)… anything wrong with that? At Perfect Touch I produced 420bhp & 355lbs/ft (392bhp @ wheels = 6% losses)… anything wrong with that? If you look at my Perfect Touch and Powerstation curves they are pretty similar the only difference being a colder engine produced 10lbs/ft more torque and held it to redline. At the top end that makes a huge difference!

So there you have it, make of it what you will. We all list our figures and graphs because it helps people understand what’s what. That said, on the road is where it matters and I have never been shy about pushing my coupe to the absolute max having done more trackdays and ¼ mile runs (including TOTB) than any other forum member this year… and all at full boost!!

Flea - you obviously have a log of people's pwoer runs, as I couldn't remember all of my own, let alone anyone elses!

I can see your point though - my calculated fly figure is within 1% of each other, regardless of the transmission losses (which at Powerstation was down to me having 32psi in the front tyres)

It all sounds very plausible, right up to the point where a certain car was dyno'd with 420bhp at Perfect Touch, then managed another 60bhp at Powerstation less than a week later.

Quote:

---

At Perfect Touch I produced 420bhp & 355lbs/ft (392bhp @ wheels = 6% losses)… anything wrong with that?

---

Er, well, yes actually....

I think one of the issues would be Perfect Touch's low estimates of transmission losses. 6% is remarkable, or more likely, improbable (note that I don't say "impossible") I seem to recall my transmission losses at PT were in the region of 35-40bhp, or about 9.5% (which I still reckon is low)

I've heard Rob's explanation (a standard Skyline loses say 75 bhp - about 25% - why should a 1,000bhp Skyline suddenly lose 250bhp - its more likely to be in the region of 100bhp, or 10%)

Basically, you are stating that the transmission losses calculations will be different at each RR, but that the end result (ie the calculated fly figure) is about right. This works for most of the examples above, apart from your own car.

You're defending the transmission losses at Perfect Touch AND the fly figures at Powerstation. While I have a lot of respect for both places (by far the best two I've ever visited), at least one of them must be wrong!

Don't get me wrong - I don't have a problem with dynos giving different results - in fact I still quote my power as 394bhp, which is PTS's figure - a session a week later at PT gave me 20bhp less.

I'm jealous as fccuk about your power (whether its 420 or 480, its still a load more than mine!)

I think what we need to do is simple - compare runs on the same roads only. So, if I got 394 at PTS and someone gets 395, they have a bit more power. If I get 375 at PT, then Flea has a lot more power!

However, if I get 421 at G-Force, I do NOT have more power than Flea (unless he tries at the same place and gets less than 420)

Anyway Flea, now I've had a pop AND jumped to your defence, when are you going to spill the beans about your spec?

Spot my reply on the other thread Nigel

Leighton,..you are SUCH a wind up merchant!

Joe

Interesting stuff - I had a few comments:

- PT's 6% losses seems low compared with the rest of the percentages in your post. Given that you know your power at the wheels, this really low % transmission loss presumably just means a funny calculation has happened for some reason;

- @Nigel - also, at least from the stats for Powerstation, the 25% transmission loss figure used by G-Force would seem fair, wouldn't it?

- In relation to the use of wheel figures, is the potential percentage deviation greater or less than in respect of "at fly" figures? If it's greater (due to calibration, ambient temps etc etc) then the at fly figure is potentially more accurate, isn't it? If it's less, then the reverse is true, and people should be quoting wheel figures

Always up for a wind-up, me

To be fair though, looking at figures, there is a question that it should be fair to investigate. I mean how can one RR calculate losses of 6% and another 20% on the same car?

Quote:

---

Jimbo (modded) – 278bhp & 252lbs/ft
(194bhp @ wheels = 30% losses)

Jap (modded) – 265bhp & 251lbs/ft
(196bhp @ wheels = 26% losses)

James_H (modded) – 288bhp & 254lbs/ft
(207bhp @ wheels = 28% losses)

MC_Mike (modded) – 274bhp & 262lbs/ft
(202bhp @ wheels = 26% losses)

Nigel (modded) – 302bhp & 246lbs/ft
(191bhp @ wheels = 36% losses)

---

Ok looking at lightly modded coupes above PS are averaging say 28% losses which sounds too much for me.

compare the above with some other lightly modded cars taken off the Hall of Fame:

Yellafella – 265bhp & 270lbs/ft
(227bhp @ wheels = 15% losses) PTS

Solid - 266bhp & 247lbs/ft
(223bhp @ wheels = 16% losses) PTS

Steviemitch - 263bhp & 285lbs/ft
(225bhp @ wheels = 15% losses) Owen Devel

Smeg - 275bhp & 260 lbs/ft
(226bhp @ wheels = 17% losses) SRR

Gurmon - 280bhp & 280 lbs/ft
(250bhp @ wheels = 11% losses) PTS

Akeme - 284bhp & 261 lbs/ft
(233bhp @ wheels = 18% losses) PTS

Nobby - 305bhp & 285 lbs/ft
(232bhp @ wheels = 24% losses) Powerstation


Most other RR's look around 15-18% losses for our FWD cars so why are the losses most people get from Powerstation more like 25-28% Are they under-reading ATW* or over-estimating Fly?

The only thing I can see is if the peak torque figure is much different to peak power then the figures could be questioned?


*It would appear not as the ATW figs for Flea were pretty much the same at both Powerstation & Perfect Touch.


Ho hum, I know this discussion comes up every now and again and its a bit but anyway when's the next RR day down Powerstation

Flea - you're breaking new boundaries for the 2 litre coupe by reaching 480bhp ATF. Also, by keeping your tuning methods very close to your chest it's always going to rouse some suspicion.

That said, there is no reason for you to lie and I for one don't need proof of your claims. I'm sure it'll make for very interesting viewing at Silverstone if you do decide to bring the coupe along.

Most things that i wanted to say have been said.

At the end of the day as mentioned, at the wheels figure is the only one that can quoted. What i find amazin is you know better than most yet, your quoting your highest flywheel figure and your highest at the wheels figure.

Comparing at the wheels figures your getting 358bhp at pts and 398 at pt. This could be down to different rollers. But you cant quote one of each. I personally would be sticking with your 398bhp figure, as this is the highest MEASURED figure. Give me a 28% increase and im on 362bhp. Which was the same as what you got previously. I personally use 283 for my own use (improvements and comparisons) but you were the one that provided me the figure of 334 ish. at the wheels is where it counts. My previous at the wheels figure was 212bhp using a mata dynometer. which i was told was 264 at the fly. So i'll be doing a run before i change anything this weekend to compare against my local one.

Ross

But Ross do the ATW figures take into account ambient temps? If it's 30 degrees your surely going to achieve less power than you would do if it was 5 degrees.

Flea I certainly ain't damning you at all. I've already said 'well bloody done' on t'other thread. I'll say it agian: nigh on 400 ATW is an amazing achievement.

I have questioned Powerstations calculations before. I mean 29% tranny losses on a FWD. They just don't look right compared to any other RR.

This whole dyno thing gets more and more confusing. It's been said that they measure torque at the wheels and calculate bhp from this figure. THEN they pic a figure from thin air and add it to get the power at the fly???

As JohnS has pointed out, a car loses more power through the transmission at higher revs. Maybe the cars that are getting big losses are getting their peak torque/bhp at higher rpm, whereas the cars with the lower loss figures are getting peak power further down the rev band??

What we need is a chart with a broad selection of cars with all types of turbos types showing ATW, ATF, and both.

At the very least you chaps could add the rpm to the cars you have listed above... Might be nothing in it of course

I guess that the type/weight of alloy you are running should also be mentioned ...

I got my peak power just below 6500rpm.

Just spoke to Falkland.co.uk and without quoting, unless i have got confused, they work out the bhp from the drag power and the wheel torque. Thats the same dyno as the one that flea has used. SO, they might actually have the most accurate figure. The MAHA dyno is supposed to be the most accurate in Europe. So there ya go. Any chance Flea that you could post your original graph up?

Ross

And an 800bhp FWD car would be equally as fast if it had 700bhp at the wheels (or whatever it would need to be same at the wheels figure) from a rolling start. So its at the wheels that counts!

Ross

I had a nice chat with a guy from maha Germany on my last rolling road session. They recently installed the rolling road, so the guy was there to fine tune everything. He said that Audi Germany now only accepts official power results from their rolling road.

Daniel

I've stayed away from this thread until now, but it's winding me up now - so here goes:

Leight - congratulations on pushing the 2lr engine - Well done for having the B*lls to try something different. Same applies to Nigel.

What we now have here is a coop that is without question running between 420 and 480 bhp, with acceptable spool up considering where the rev limit has been put on the car. We dont know the spec, but I'm assuming its got a flowed head and a GT30 or 2871 to make use of the 7,750 rpms availiable.

if Flea can make 360-380 bhp on a standard head with a 0.86 RS then why is another 70 bhp or so not possible with a bigger turbo and a more efficient head with 1.6 bar of boost?

I reckon Nigel's car would be good for over 400bhp when it's running right, and when the exhaust is opened up to 3 inches. (sorry Nigel - I'm sure the supersprint is loosing you top end!) Nigel has come damn close to the 400 mark with a 7,000 limiter as far as I know.... so if it was raised a bit....:) even my car on a little 28R would produce more power with a raised limiter as it's been opened up nicely.

can we stop squabbling over the figures please and just say that Flea has one blo*dy quick coop, and that Perfect Touch have done a cracking job live mapping it - their knowledge will no doubt be very useful and make modding a fair bit cheaper without the need to go for a stand alone ECU that can cope with 5 pots!

I don't believe anyone is going to get much past 400bhp on the standard head, it just can't flow enough. I made 6bhp more throwing 1.6 bar at my first engine than 1.1 bar gave, same rolling road, same time of year, and same RR operator/mapper