Advice on extra quickness for BARMY the SE

Lokiel · Postby **Lokiel** » Tue Mar 27, 2012 3:33 pm

I would have guessed 12% - but I think I read that figure somewhere and it stuck in my mind.

plohl · Postby **plohl** » Tue Mar 27, 2012 3:37 pm

dry ice intercooler

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Postby **NitroDann** » Tue Mar 27, 2012 4:29 pm

Sounds like accurate and specific info for an mx5 with a 3.6torsen using 80w90GL4 castrol and Se axles, along with 43'000km old bearings and an se 6 speed using redline making 176rwkw...

Dann

davekmoore · Postby **davekmoore** » Tue Mar 27, 2012 8:25 pm

Blimey!

bear2230 · Postby **bear2230** » Tue Mar 27, 2012 9:33 pm

NitroDann wrote:Sounds like accurate and specific info for an mx5 with a 3.6torsen using 80w90GL4 castrol and Se axles, along with 43'000km old bearings and an se 6 speed using redline making 176rwkw...

Dann

davekmoore · Postby **davekmoore** » Tue Mar 27, 2012 10:18 pm

Please also note that I'm an ex Pom, so am used to flywheel bhp or whatever those PSs are, not dríven wheel kW.

Postby **NitroDann** » Tue Mar 27, 2012 10:31 pm

174rwhp is alot.

I just dont understand why there is any need whatsoever so know the flywheel horsepower.

Dann

davekmoore · Postby **davekmoore** » Tue Mar 27, 2012 11:55 pm

You see, that's really confusing Dann, because BARMY has 174rwkw, which translates to 231rwbhp and not the 174rwhp you mention. In my pommie language and mathematics, 174rwkw means 258-265 flywheel bhp depending on whether you use 12% or 15% mechanical losses as suggested in previous posts instead of my wrong suggestion of 40kw losses. 258bhp at the flywheel at low end of the formula is defo a Good Thing bearing in mind that my dream as an 18 year was to have an MGB, which had 90 flywheel bhp a good day.

Either way, BARMY has done heaps of kms as a daily driver with whatever power he has and he hasn't broken. I'm listening to the advice on here about making him quicker/faster to a) make up for some of my shortcomings as a track driver and b) get a bigger buzz when the turbo does its thing and c) frankly (because I couldn't afford any kind of modified car until recently) so I can have one of the best MX5s around.

So any more advice is greatly appreciated, along with replies to the PMs I've sent to various people who've been dobbed in as gurus.

Postby **NitroDann** » Wed Mar 28, 2012 1:18 am

NitroDann wrote:174rwhp is alot.

I just dont understand why there is any need whatsoever so know the flywheel horsepower.

Dann

Sorry I meant rwkw.

It had over 170rwkw. or over 220rwhp.

Its quick

but you still need new rods before more boost or a different hotside setup.

Dann

Guran · Postby **Guran** » Wed Mar 28, 2012 8:08 am

Ah come on Dave. You've been in Australia long enough to think in dollars and cents instead of pounds and pence. Time to move on and recalibrate yourself with killer wasps instead of broken horses. The mental arithmetic is good for your health. :lol:

93_Clubman · Postby **93_Clubman** » Wed Mar 28, 2012 1:08 pm

NitroDann wrote:I just dont understand why there is any need whatsoever so know the flywheel horsepower.

Familiarity, due to manufacturers practice.

Postby **NitroDann** » Wed Mar 28, 2012 1:50 pm

Manufacturers use it because its a bigger number, not because its relevant to anything useful. If you want to compare to some stock car, its very easy to find stock RWHP figures on just about anything. Thats like comparing dry weight, whats the point, its not what affects performance, it just sounds lighter.

Dann

Lokiel · Postby **Lokiel** » Wed Mar 28, 2012 2:08 pm

Here's my theory concerning drivetrain power loss:

Drivetrain power loss figure CANNOT be a hard and fast percentage value regardless of engine output, it must decline at an exponential rate as the engine output increases since most of the power loss is required to get/keep components moving. ie. The faster you go, the easier it is to maintain momentum - less energy loss.

Have I over-simplified my analysis?

sailaholic · Postby **sailaholic** » Wed Mar 28, 2012 2:14 pm

Manufacturers use flywheel because they uses engine dynos not chassis dynos.

Engine dynos are far more accurate for engine development work and it gives them the same power figure regards of transmission option.

Touch over cynical saying it is because its the bigger number. Its what they test on, same as we (generally) test on a chassis dyno.

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Apu · Postby **Apu** » Wed Mar 28, 2012 2:18 pm

There's also an element of wear and tear right? For example, if I had my car up on stands and tried to spin the wheels, it would take some effort. However when I spun the wheels on a Lotus Super 7 - it did it very easily and kept spinning for ages!

A bit of an extreme example, but take two cars of the same make and model - one might have components that are more worn and therefore turn less efficiently (or even newer components that have not bedded in).

Which is what Dann's pointed to - why should flywheel kW matter? At the end of the day, it's how much of that gets to the wheels, and that will vary from car to car.

Plus for most of us...measuring at the wheels is much easier and "available"