Interested in Rolling Roads and tuning?

[alan_thomas]

I attach a link to an excellent and informative article http://www.pumaracing.co.uk/POWER3.htm

The bottom line is forget the 'Flywheel' BHP you should only compare the figure at the wheels. Interesting to see the effect of tyre pressures. Also the article puts to a fairly convincing argument to suggest it is pointless using a rolling road dyno to compare with manufacturers original figure. Also if a high 'At the wheels BHP' is your aim forget that automatic or overdrive both soak up power. Use a manual without overdrive and pump up those tyres!

Also I spent a long time talking to the tuning expert from the 'Extra EFI' stand. His knowledge of tuning race engines was immense. What he said to me was people often come to him with a Cobra or TVR and say 'I want 300BHP at the wheels'. He say 'Yes I can do that but will you only be using it on Track days?'
His point is that peak BHP is achieved as a compromise to other factors. If you are on a race track and have enough gears to constantly keep the engine in the, now narrow and high RPM, power band then you will benifit from the extra peak power. If you want to use the car as a road car then you may well end up with a slower 0 - 60 time and a car that is a pig to drive.

For our type of cars and for our type of driving 'driverability' and 0 -60 are more important than striving for 'Peak Power'

- Alan

[Kevin Garrod]

I think mine had 120 at the wheels, and over 160 torques across the revs. I'm just glad my stag is running better than ever. Having the best top figure (for carbs) on the day was just the cherry on the icing on the cake. I will read the article when I get back home to broadband land.

[Guest]

That's a good article which anyone who judges things by quoted bhp should read.

The only real way to see if any mods you have done have made the car quicker is to have accurate timings for certain acceleration bands before the work and then after. The other way is to use your own perception of quickness, but just being aware that the placebo effect is prone to kick in. We have probably all read posts on other forums where the gullible say that their standard car has just been dyno'd and shows a bhp higher than the manufacturer quotes or achieving a huge increase after fitting something like a fat exhaust. I especially like it when I see a sale advert for a 328 or 330 BMW which claims it has been remapped and is now quicker than an M3.

I know a tuner quite well and have played about with my M3 with various maps, exhausts and stuff. We take it to the dyno in Uxbridge (a Dyno-Dynamics dyno machine) who seem to have a reputation for honesty and it's quite amazing how little difference some things make -and sometimes the car actually shows less power and feels slower on the road. As the article says, setting the air temperature / humidity and the conversion factor dialed in to take it back to "flywheel" has a massive effect on what you see on the dyno. The dyno operator showed me that, without the car coming off the dyno, by changing settings that don't appear on the printout (air temp and humidity usually do) the bhp and torque figures suddenly show a hell of lot more power.

[len]

hi

i too put my stag up for the rolling road and it recorded 142.4. on a standard stag carbs etc. it was then explained to me that the way the carbs were set i.e for economy and performance that it was a very good reading, it was also pointed out that at 5000 rpm not a lot more was happening apart noise ! meaning that the carbs needed adjusting to allow more fuel in.but at an obvoius loss of economy. so i could have it retuned to achieve more hp but but will i ? No ! i was only curious to see if my engine was as good as it should be ,and the answer to that was Yes !
len