RS + 1 Update

[vic cohen]

Polite suggestion go to Ninemeister..............after what some of us saw on the way to Oulton, Friday, i ve never met anyone else in this country so focussed/experienced with rs
engines ............................

 

[johnny senna]

ORIGINAL: SimonExtreme

RSR

I have been through your type of problem with other makes of car and there is a way of resolving it. You need a car that is either totally standard or one where the engine has been on a dyno (recently). Then you can run comparison tests. Ignore the "estimated" flywheel power and just concentrate on the ATW power and the torque. This will give you a good comparison. I guess the only issue with the "standard" car is that there seems to be a difference between a good standard car and an average one.

In addition, it should be done on a "neutral" RR. The operator can make a difference depending on how the vehicle is tied down, how the power is applied, whether you get slip on the rollers etc. In terms of consistancy, I would go to somebody with a Dyno Dynamics RR. The Evo scene does lots of RR days and there is no doubt that a Dyno Dynamics RR gives the best consistancy, both on a single day and over time.

Hope that helps. What scares me about your story is that I am about to spend a fair amount of money to take my power up to about 325-330bhp and am having problems trying to decide who to get to do it. Now I am even more worried!

I agree with Vic. I would choose 9M every day of the week. I was hugely impressed with their set up and the re-map work they did.

 

[Laurence Gibbs]

unfortunately the problem is finding a "standard" car that is making factory hp figures! 993RS engines can suffer from a wide varience in figures, often due to cam slip or sprocket slip depending on your point of view. If you use a car with the modified cams you no longer have a "standard " car!

 

[RSR]

Agree with you on the 9M front and under the circumstances he was the only guy I could trust who would remain impartial to the situation with the other guy. That is where the car is and it was Colin who carefully took the engine apart and produced and extensive report of his findings.

Unfortunately the other guy is disputing the opinions in the report and trying to avoid paying for the new parts required. If I don't get a resolution by next week I will have to rectify it myself. Shame really when someone else has already spent the thick end of £14k on the rebuild.

 

[paul howells]

rsr
can you not get a third party to back colins observations,it will not be difficult with what i saw of the engine.
The front spoiler etc that was on russ car,is it for sale,i can do with a spare front splitter.I can get the same shaped evo one in the states for £500.
Also is there a set of bbs wheels, i need either a set or 2.

 

[Ninemeister]

ORIGINAL: ClubSport 911


So..best thing you can do, is ignore the actual, but pay attention to the difference you get from your tuning efforts.

I agree entirely with everything you have said regarding the accuracy of rolling roads & the so called engine power that is quoted from them.

With respect to rear wheel power figures, making the fundamental assumption that the inertia of the rollers is fixed, the rear wheel power figure that my Bosch dyno kicks out is the actual power recorded on the day calculated by the rate of change of speed of the rollers. Irrespective of any other measurement this figure is a pure mass acceleration measurement without correction or fiddle factors blended in, so can be argued that it is the best figure to use for comparitive purposes.

Personally I do record and value the engine power results from my dyno, but this comes from the experience of using the same dyno for the last 15 years and only comparing results obtained from this dyno. The following are from fairly recent tests:

964RS live remap 290-300 flywheel, 265-270 wheels, 380-390Nm
964RS Motec 320-330 flywheel, 293-299 wheels, 395-410Nm
964RS Motec +1 340-350 flywheel, 309-317 wheels, 410-422Nm
all tested in 5th gear

993RS cup cams, RSR mag intake, as arrived 291 flywheel, 246 wheels
993RS cup cams, RSR mag intake, after live remap 348bhp flywheel, 290 wheels, 405Nm
993RS cup cams, Carbon RSR intake, after live remap 366 flywheel, 330 wheels, 424Nm
all tested in 6th gear

An interesting points to note: 964RS engines all peak at approximately 6000rpm, whereas the 993RS engines tested above peaked beyond 7000rpm. Since I always test cars in top gear to reduce the torque at the tyre and minimise slip, this means that the drive losses of the 993 are taken at over 180mph and therefore vastly exceed those of the 964RS taken at 150mph, since tyre losses are roughly proportional to the square of the speed.
All the results are uncorrected but certainly tested at similar air temperatures of 10C or less; assuming near standard air pressure the correction factor for 10C is 0.983 or ~2%, for 5C it is 0.974 or ~3%. In the case of Boydy's 964RS Motec +1, we actually recorded the air pressure and intake temperature on the night it was remapped, for the 1016mbar and 10C intake temperature recorded cf = 0.980 implying that the rear wheel power was actually 310bhp (& flywheel 343bhp, if you believe the dyno calculations).

Finally, regarding your point on dyno sampling speed, etc., I would like to add that we are awaiting on a dyno upgrade which uses a SPARC processor controller. For those of you without the benefit of computer lingo, the computer behind the system uses RISC (Reduced Instruction Set Co-processor) technology to speed up mathematical functions and has the fastest sample rate of any dyno package on the market today. It will be very interesting to compare the results from the upgrade with our existing system.

 

[Guest]

Aren't you supposed to dyno in the gear that is closest to 1:1 (usually 4th?) rather than 5th/6th that are overdriven? I recall reading that it is more accurate.

Did I just make that up or has anyone else heard that?

 

[Ninemeister]

ORIGINAL: Richard Bernau

Aren't you supposed to dyno in the gear that is closest to 1:1 (usually 4th?) rather than 5th/6th that are overdriven? I recall reading that it is more accurate.

Did I just make that up or has anyone else heard that?

There is no right way or wrong way really, as long as you compare eggs with eggs you will have meaningful results. The difficulty is in comparing the 993RS with the 964RS due to the different gearing, hence my comment above. You can test a car in any gear, but with powerful engines and only two tyres to use the most common method is to use the highest gear possible to minimise the torque at the tyre. When we ran up Vic's 993GT2 there is no conceivable way the car could have been tested in 5th gear instead of 6th, with 800Nm even in 6th the tyres were lighting up until I loaded the car with ballast (thanks Vic & Paul for volunteering!)

As for accuracy, in my experience, top gear (overdriven) tests seem to be more accurate, furthermore because the inertia gain is higher for any engine speed range test (eg 3000-7000rpm) the engine acceleration reduces making it easier to monitor the results (back to datalogging sample speed again).

Final points top add were the results of two other cars tested on the day.
996 GT3RS 407bhp @ flywheel
996 GT3 Mk1 370bhp @ flywheel
996 GT3 Mk1 with expensive carbon air intake system 360bhp @ flywheel
Sorry but I cannot remember the rear wheel power figures.