Rufs on the rollers?
Discussion
The owner of the rollers posts on here, so I'm sure he can explain better, but suffice to say whilst their rollers are well-suited to normally aspirated cars up to circa 400bhp, their set-up was clearly not designed for the unique requirements of 500+bhp rear-engined turbo 911s.
Henry's modified GT2 dynoed lower than stock (and it is definitely faster than stock) and the Yellowbird also dynoed very low figures that did not correlate with it's proven performance.
Given that we called it a day and didn't dyno any other cars.
Guy
PS The CTR has given 520bhp on Rufs engine dyno only a few months earlier.
>> Edited by GuyR on Wednesday 9th February 14:41
4WD said:
Doesn't this show dyno readouts are all pap, best left for bar room banter. Quarter mile or actual lap times are the only real indicator IMO.
Well, those (quarter mile, lap times, etc) are not real indicators of how powerful the engine is, they're indicators of how fast the car is up the road (which may be more or less interesting depending on your perspective).
It seems to me that perhaps either the particular dyno in question is not up to the job, or the operator is not using the equipment correctly. But maybe there were "circumstances".
Not being an expert, but I see no reason why a correctly setup and correctly operated dyno would not give decent results.
I have used many types of dynos many times for many of my cars (300-1000bhp) and providing they are correctly set-up, correctly cooled and ventilated for the cars in question they are a very useful tool, especially when comparing pre/post modification and also one car vs another of the the type.
Guy
A good explanation on rolling roads, their function, operation and a comparison of differing types, measurements, calculations etc can be found here www.wrc-tech.co.uk/services-rolling-road.htm
Regards
Allan
Regards
Allan
Hi, Let me explain.
Cooling Porsche Turbos on the dyno is very hard. The position of the intercoolers makes it very hard to get the correct amount of air to them unless you have a specific Porsche Dyno setup.
We hadn't run any turbo Porsches before these, and its clear that our cooling wasn't up to speed. The 996 especially retards the timing as it gets heat soaked.
We run 99% of big power cars with no cooling problems at all. We routinely run 600 bhp RWD Skylines and other big power stuff.
With turbo cars its all about the intercoolers, don't get enough air on them and the power will drop a huge amount. Where the intercoolers are at the front this is easy.
This was a bit of an experiment to be honest, and I didn't see it as successful in the end. Both readings were quite seriously below what I would expect.
For the moment I've simply solved the problem by telling people we won't run the Turbo's. The extra investment needed simply is'nt worth the money we will get back from the 10 or so we would run in a year.
Of coarse, N/A cars are easier and we have run two MK2 GT3's successfully. (both PH'ers cars incidentally). The standard one gave 381bhp at the fly and the other with Millteck exhaust gave 392 ish Bhp.
Thanks to GuyR and Adam for taking the time to come up to us, i can only apologise for the service not being up to the high standards we as a company strive to provide for our customers.
Charlie Wright.
MD, Surrey Rolling Road Ltd.
>> Edited by vixpy1 on Wednesday 9th February 17:51
Cooling Porsche Turbos on the dyno is very hard. The position of the intercoolers makes it very hard to get the correct amount of air to them unless you have a specific Porsche Dyno setup.
We hadn't run any turbo Porsches before these, and its clear that our cooling wasn't up to speed. The 996 especially retards the timing as it gets heat soaked.
We run 99% of big power cars with no cooling problems at all. We routinely run 600 bhp RWD Skylines and other big power stuff.
With turbo cars its all about the intercoolers, don't get enough air on them and the power will drop a huge amount. Where the intercoolers are at the front this is easy.
This was a bit of an experiment to be honest, and I didn't see it as successful in the end. Both readings were quite seriously below what I would expect.
For the moment I've simply solved the problem by telling people we won't run the Turbo's. The extra investment needed simply is'nt worth the money we will get back from the 10 or so we would run in a year.
Of coarse, N/A cars are easier and we have run two MK2 GT3's successfully. (both PH'ers cars incidentally). The standard one gave 381bhp at the fly and the other with Millteck exhaust gave 392 ish Bhp.
Thanks to GuyR and Adam for taking the time to come up to us, i can only apologise for the service not being up to the high standards we as a company strive to provide for our customers.
Charlie Wright.
MD, Surrey Rolling Road Ltd.
>> Edited by vixpy1 on Wednesday 9th February 17:51
Charlie is right (pardon the pun), you do need a special cooling set up to dyno 911 turbos correctly, without it you immediately get heat soak of the intercoolers as soon as the engine is under load. This kills power completely.
Since we mainly tune 911's, we set our dyno up with this in mind by having two 3kW axial fans running in 600mm diameter ducts built into the set up.
The first fan sucks air in from the back wall of the building and blows down through a venturi onto the engine lid at 70mph flat out.
The second pulls air through a grid directly under the engine and takes the hot air & exhaust gas down, across and up out of the side wall.
We had a turbocharged 993 on the rollers today for fine tuning. This was an engine that we converted from a stock 964 3.6 and briefly had Motec M48PRO, headers, twin plug, single turbo & bid intercooler. At 0.9bar boost the engine made 392kw/662Nm or 530bhp/489lbft under load in 6th gear, equating to over 475bhp at the tyre. With the cooling set up running the air inlet temperature after the intercooler never made it above 17C under load, peaking at 24C only on lift off from a run and dropping to 17 again seconds later.
The only other way of running a turbo 911 on a conventional dyno is to build a chargecooler system for the engine that runs off a tap, i.e. total loss. However in theory you need a custom cooler for every variant, so it can get involved to make them all.
>> Edited by ninemeister on Wednesday 9th February 22:52
Since we mainly tune 911's, we set our dyno up with this in mind by having two 3kW axial fans running in 600mm diameter ducts built into the set up.
The first fan sucks air in from the back wall of the building and blows down through a venturi onto the engine lid at 70mph flat out.
The second pulls air through a grid directly under the engine and takes the hot air & exhaust gas down, across and up out of the side wall.
We had a turbocharged 993 on the rollers today for fine tuning. This was an engine that we converted from a stock 964 3.6 and briefly had Motec M48PRO, headers, twin plug, single turbo & bid intercooler. At 0.9bar boost the engine made 392kw/662Nm or 530bhp/489lbft under load in 6th gear, equating to over 475bhp at the tyre. With the cooling set up running the air inlet temperature after the intercooler never made it above 17C under load, peaking at 24C only on lift off from a run and dropping to 17 again seconds later.
The only other way of running a turbo 911 on a conventional dyno is to build a chargecooler system for the engine that runs off a tap, i.e. total loss. However in theory you need a custom cooler for every variant, so it can get involved to make them all.
>> Edited by ninemeister on Wednesday 9th February 22:52
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