eclou

TB you just need to unplug a couple of spark wires and run again

Geoffrey

Yea, I don't agree and I don't think you have enough information to make the assertations you are making. I don't think you have any facts about how load is measured (not calculated) from the dyno manufacturers.

The shootout mode on the DD exists as an attempt to utilize a standard set of parameteres by which a car can be compared to another car regardless of which DD is used for the testing. It is not without its faults. As with all wheel dynos (Maha included), there is some amount of inertia from the rollers and the dyno software will calculate that out, in addition to that, the intake air temp, barometric pressure, and other parameters normally user adjustable, are set as well as the ramp rate. So, all cars are tested in the same manner. This is the shootout mode. I don't use it, but I can see how if the Maha run is different in length than the shootout mode of the DD, then the load will be more or less depending on if it is longer or shorter a run than the Maha.

With regard to strapping down the car, the more power the car makes, the more the car needs to be strapped down to help with tire slippage. The double roller dynos help keep the car from jumping off the dyno because they have a difficult time climbing up the drive roller. I've seen cars strapped through the windows only and not come off the dyno. The 427 Chevrolet engined car I referenced in an earlier post required quite a bit of strapping to keep from slipping the tire. It is all going to be a trade-off.

pete95zhn

Before this discussion gets too hot, and upper lips too stiff, here's some dyno fun for you...:

http://www.amworks.com/gallery/video/amw04.wmv

The best part is saved last.

Jean

I understand perfectly well what TB is saying. The runs made in this specific shop are quite different from anything we see elsewhere. One should not forget that these guys have no stake in the numbers, they are there to show you what you really have per specific industry TUV norms, whether we think it is meaningless or not is irrelevant, it is the same standard by which Porsche measures their numbers.

Not saying they are better than others.

Some of the torque numbers seen on the forum at claimed low boost numbers are simply laughable, I even wonder how the tuners themselves are not shy of posting them. Whenever I see a deviation of more than 5% or so, in torque numbers than any equivalent engine, I start questioning the methodology used, or the boost claimed, some customers do believe in magic, I am one of them, but I call it what it is , magic, not torque.

I have a friend who was denied having a very expensive engine built for him in the UK by a very reputable tuner and RLister because he put as a condition that the numbers that he was paying for would have to be validated by Manthey's MAHA at a later stage, the tuner refused, it was his dyno or none. The customer was paying for all the expenses incurred, he just wanted to put his car on the MAHA after the build, to validate independently the numbers. Why would that be? RUF did not have a problem with that same approach.

NineMeister

Very interesting discussion lads.

With respect to the numbers measured on the Manthey dyno, this week I had the fortune to test a Mk1 GT3 with a Manthey fitted and tuned K400 kit. On our dyno it showed 404hp & 440Nm which was a fraction behind a standard GT3RS which coincidentally was tested with the same make and size of tyres, so in other words it is pretty close to the manufacturer's claims. Also on the dyno this week was our fabricator's VW Beetle drag car which has a turbocharged 3.2 litre Autocraft engine, and in spite of it running on 225 road tyres, at 2 bar boost & race fuel it managed to put down 650hp and 850Nm without wheel slip (backed up by several runs). This 900kg full floorpan car does 9 second passes. Given that we only have a Dynostar upgraded Bosch dyno and can run a car in freewheel or load supplemented (braked) inertia runs I am struggling to understand why Manthey cannot run Toby's car at full boost to give him a meaningful torque figure.

Woodster

Colin,

Just so I understand: was the 404 hp at the crank?
and was the GT3RS a 996 based car also?

MK

Stummel

Maybe TBs car is putting down more torque than the 3.2l engine

btw: That the dyno gives right numbers for a low torque n/a car does not prove that it gives the right torque numbers for a hi torque turbo engine.

NineMeister

The 404hp was the corrected DIN figure at the crankshaft, and it was a 996GT3RS that I compared it against, which is one of several we have tested that all have practically identical performance.

NineMeister

Possibly not, but at least we can test it at full throttle all the way through the rpm range and make comparative measurements (whether they are accurate or not). Which kind of leads me on to a point that may have been overlooked during the course of this discussion.

Given that all chassis dynos are relatively simple devices that have fixed inertial rollers & some form of electro-mechanical brake with a torque measurement cell, and that the maths and physics of the torque/rpm calculation are the same whatever units you choose, it is pretty much a given that the manufacturers of all dynos get the calculations right. Therefore the only variable left can only be the raw calibration of the dyno, hence why (for similar airflow managed installations) there will always be slight variations between the results of the same or similar cars from different dynos.

So, if we accept and can move on from the fact that dyno calibrations can vary slightly and there is no guarantee that any chassis dyno is absolutely accurate (not even a Maha), then all that is left to contemplate is why our turbo cars sometimes record relatively excessive torque numbers when tested in different circumstances. Is this correct answer to this conundrum not simply that the torque measured by the chassis dyno is correct and that, under the circumstances of the test, the engine simply made more torque dynamically than it would if it was tested under the near static conditions on an engine dyno?

uk trucks

Chaps
As of June 2007 I closed WRC/Weltmeister and as such am no longer a "tuner" in the broadest sense. It has since emerged that the 996GT2 in question was not tested using the Dyno Dynamics spark method, wherby a pulse is picked up from a coil pack. Most of you will know how difficult this is.

The DD has a facility to pick up info direct from the OBD port but as this was in use for live tuning, this was not used either sadly. The net result is that the graph is not useable as there was a small error in calculating the gearing, this results in "squashing" the torque graph up slightly, resulting in an overstated amount of torque. Not by a lot but by enough to stimulate the attack on DD machines.

The car probably had 590Lb-ft or around 790Nm in reality. The actual on road performance was awesome. I say was as the car was smashed up total loss not long after the mods.

However I recently carried out similar mods to a 996TT "S" Cabriolet and for a 1660kg 4wd car it certainly can run.
It ran at Bruntingthorpe at 192 MPH on pump gas and 193.4 on 102 which I suspect was stale. There was also a 10 MPH gusting headwind on the day. The test straight is 2 miles. The 996 ran neck & neck with a new Lambo LP640 and on the day a Ruf RT12 ran 204 MPH.

We have not dyno run this car but suspect it to be c535 bhp and over 790nm of torque. The driftbox data from it was all a bit patchy as it was the owners first time of running it. I did see 0.9g as peak acceleration in the data ?

TB I would urge you to get your car down to DSA [prev G-Force] in Aylesbury. They have good airflow and have run many 993Turbos including "Flamespitters" cars. Once strapped in correctly I would expect zero wheelspin on a 993 in 2wd configuration and full throttle could be used from 2500 revs. If you are overwhelming a MAHA this does not surprise me. We ran over 24000km on our dyno and only had trouble with an 800 dragster and a Carrera GT which we eventually got strapped in and run, it did try to escape a few times.

We also had the issue of very sticky wets robbing the 599 Fiorano of lots of BHP and then Ferrari fitted new wheels and tyres and voila within 2 BHP of Modenas own engine dyno.

Cheers

Allan
email to chipchapmk at gmail dot com

Jean

Allan, thanks for being open about it.

The morale of the story is that fat torque readings, areas under the curve and dyno graphs are totally meaningless when used as main selling tool to compare the different kits available from tuners. Regardless of the dyno brand and how expensive it is, any slight error in usage or manipulation from the tuner can give useless numbers. As long as Rennlisters are aware of this, we're all winners.

The magazine tested LP640 does the 0-300kph (0-186mph) in 32seconds, about the same as the new 530BHP 997 GT2. Therefore this 996 cabrio (much more weight and worse aerodynamics than the Gt2) should be putting substantially more than those numbers. ...Assuming the LP640 was running well that is.

uk trucks

Jean
The LP640 is new and is the car used in Evo's fast fleet articles. The owner is fastidious. However not having dyno tested the car we ran and based on past experience, you can imagine my reluctance to overstate any numbers. Bruntingthorpe is an old airfield with a 2 mile straight. It has an uphill and downhill section. The facility is used as a benchmark in UK. I believe MOD500 has run 193 here on a previous day. We also had a wind tocontend with which had already blunted a Ruf RT12 which ran 207 here on a previous day but only !! 204 on the day we were there.

The 996 Cab runs the same programme on its daily commute from Berkshire to London & back every day. The owner is over the moon with the car.

We had some other data but as he had already lunched one clutch at a previous V-Max event, the owner was not prepared to cough out for a second. So his take offs were not fierce.

Here is some data from Driftbox but some of it makes no sense

--------------- Run 0014 ---------------
Time 14:07 Date 11/11/2007

Accel results
Speed(mph) Time(s)
0-60 04.0
0-100 08.2

Accel Distance results
Distance(m) Time(s) @Speed(mph)
0-100 05.5 73.6
0-200 08.1 99.5
0-400 12.1 125.0

Braking results
Speed(mph) Time(s) Distance(m)
60-0 47.8 240.0
100-0 53.3 447.1

User range
Speed(mph) Time(s)
30-50 01.7
50-70 02.4


Misc
Vmax 191.4mph * did 193.4 on another run but other data is rubbish
Vavg 58.2mph
AvgLatG -0.1G
PkLatG 1.0G
PkAccelG 1.0G
PkDecelG 0.9


Cheers

Allan

Jean

Allan

It looks like the Cabrio has more than that horsepower if it is running stock weight, which is quite amazing.

I know all about the Bruntingthorpe track inside out and have a lot of datalogs from different VMAX races from many rennlisters to compare. These are some of the numbers that you posted on PH:

I can't make much of th enumbers that you posted, it is difficult to have a visual idea, of course if you want to email me the VBox raw data, I can see what is going on more easily.

uk trucks

Jean
Off to bed now, its 22:35 here. But if you would email me at uktrucks at msn dot com I will forward what little data we have.

I would concur that the car probably has more BHP & Torque but you can understand my reticence to get into a BHP waving exercise. The car being a big fat 4wd cab still with spare wheel, compressor, lap top on pass seat 35 litres of fuel etc makes all the more impressive and it was driven to and from the event by its owner ! The runway at Brunters sorts the fast cars from the faster cars and with something like 11 runs back to back it had nice high IAT & water temps and still ran impressively.

Regards

Allan

raymondgo

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FVD Sport-Motronic DME exch., Power-Flow Kit, 5.0Bar Fuel Presure Reg., Turbocharger K24-Race L/R
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