hey guys,
hectic day, missed out on all the chit chat.
The load index is TPS position -- as you know the BMW uses DBW (drive by wire) throttle and depending on conditions and feedback from the sensors, the easiest and quckest way of protecting a motor is shutting the throttle -- which is clearly seen in the data logs. I am able to log ANY sensor you want under the hood and overlay this onto any other sensor/s
I will be testing bolt on mods with all the before and after increases/losses to set the myths aside. Inakes, DP's Exhaust systems, DV's (lots of power there!) and ofcourse the most important compressor wheels, blade clipping etc. I also have a speed sensor which works on RF frequencies and can measure up to a million RPM which i got from a friend and fellow tuner in the UK (same units supplied on the international rally cars... ) i will be able to tell you EXACTLY where in the compressor map the compressors are running, if the turbos are too small, too big etc etc -- hence my interest in playing with basic wheel changes and upgrades for my cars.
In fact tomorrow we test something in the higher HP bracket then the childs play stuff us stock car owners play with, and will publish some results in the appropriate forum for interest sake - but mainly to demonstrate the billet wheel i have had machined for me which will be tested back to back against the original Garrett cast unit. anyways that another story for another time.
Back to business -- i have build my own bike dyno (pics attached) and know a little about how these things work and how they display power/correction etc etc just to comment on something -- you should certainly not get any different power readings from different gears, as long as the power output from the engine is the same ... what you will definately get is a different graph shape based on traction and how much inertia the rollers have and how the engine is able to speed these rollers up.
In fact the way torque is calculated is based on foot pounds of work done using a foot diameter roller a foot long etc etc Power is calculated from torque as follows:- Power = torque x RPM divided by 5252. Some dynos (depending on which SAE or ISO method of calculation is used) will sometimes have the power and torque curves overlap at exactly 5252RPM -- Dynojet for exmaple. This is complicated, but George touches on the subject in the right direction -- more boost out of a loaded engine -- the more the engine loads, the more boost the turbo will generate UP TILL the wastegate setting ofcourse. 3rd gear on an inertia dyno will never give you the same reading as an engine which generates more boost due to increased load in 4th gear for example -- but try that with an NA engine -- SAME POWER EVERY TIME!
OR
Run some software like Dastek has now released where the lighter inertia rollers are able to have the load cell load a percentage throughout the run and still calculate the power and torque accurately based on the principal where the rollers now have more inertia (added by the load cell or eddy current) to make the software think the rollers have more intertia, hence you are able to run much higher HP cars on the dyno without the graph running away and giving you spiked readings.
Finally the story about the M5 -- i thought i would get my arse handed to me, but might give the guy a little bit of a run for his money. we were on the highway coming past soutgate mall towards soweto - there was a few slower cars driving miss daisy and the M overtook one, and i followed. Remember i was running octane boost at the higher power setting. the M eventually realized that there was something on his arse, and the lighte let him know it was a BM, and we started to do a few runs traffic permitting. We got to the bottom of the hill where we both kept right and there was an accident that had just happened seconds ago, so all the traffic was dead still. We got through the traffic with a clear couple of bends that led onto the long straight past Soweto -- ofcourse we gunned it and surprise surprise i was on the M like white on rice! up till 200, then he started to edge out from underneath me. all the way to Gordon rd off ramp where he turned off ... i was impressed, but expected less from my car.
Sorry gents -- just a comment on the graph George -- i see the dyno uses ambient air temp correction -- ask them to make this value 0 deg celcius -- basically switches this off, and you will se your true power at the wheels UNCORRECTED.
If my calculations are correct you will ready around 32KW less at the wheels then you currently do. I will post another graph of my car with correction on and show you the graph -- its a very quick and easy way to gain some power and torue -- SPECIALLY torque. I was playing around with this on my turbo golf and a change of 5 deg celcius gained me 13KW on a winters day at an ambient temp of around 18 deg.
Just a comment - possibly an interesting test for you to try out - otherwise a nice looking boob - i mean curve you have there.
