took my car back to msc proformace in melb for an dyno run because it felt like i lost power. after 4 runs on the dyno it come out at 201 rwkw where 6 months ago it was 223rwkw. this is an list of what has been changed since last dyno. auto was rebuilt 3g worth converter was sent for cleaning 160 thermostat - was standed msd performance coil - was standed 20inch rims - was 17inch other than that everything same even same fuel and petro station the boys at msc and my self are left not knowing what it is only thing came to mind is maybe converter wasnt cleaned and replaced right. just thought some one on here might have and idea of what it could be. thanks for all your input.

motors ****?

how much bigger in actual diametre are the tyres?? i know in forbies every 2 inch step up in tyre size you lose 20 odd hp at the wheels! Thats without diff ratio change mind you! with my GU 5.0l i made 170hp@wheels with 31's and only 150 odd with 33's!

are you sure all 8 cylinders are running?

17's to 20's!!!! They would have to weigh a heap more, there is your loss right there, the extra weight requires extra inertia, which uses power. Basic physics

yeah 20s would do it easy tip 4 dynoing is get small rims with biggest walls on them spin quicker

thanks guys. over all tyre size is 27inchs and they are heap heavyer just didnt think 20rwkw would do that. would 15inch tyres be better then 17inch for dyno?

15% larger diameter, maybe more than 15% mass, heaps more inertia and therefore energy is required to spin them Probably, ZOOM magazine testing found that cheap chinese tires with low profile were best on a dyno

i wouldnt think wheel would have anything to do with it bcoz its still same rolling diameter? my best bet is converter alot of cars loose power on dyno due to conveters

Was it dyno'd at msc last time? as different dyno's different readings. My motor apparently made 189rwkw but when I had nw bearings and rings put in it and retuned it made 230rwhp. In regards to the bigger rim, and Im just guessing here, but I wouldn't have thought that'd make a huge difference on a dyno as it's an overall reading not, a as quick to get to reading as a 1/4 mile would be?

All Dyno's Put Out Different Figures

IF the relative air density, temperature, tyre pressure etc were all the same, and the wheels were the only thing different, then that is obviously the explanation, and it is the most logical. Simple way to test is try with 17's, and then with 20's. Rolling diameter wont make as much of a difference as the change in WEIGHT. It is like using a heavier flywheel.

car was dynoed at msc last time too. would it give you diffrent readings if car was in diffrent gear say from 2nd first time to 3rd second time??? i dont see how the converter will be diffrent as it was only sent to be clean but you never know. ill ring up the auto bloke later in week to see what he has to say bout it. if all fails ill get a new converter. what converter would be the best to keep your power would an lock up work best or just an standed one?

non lock up convertor could quite easily do this.... so many variables could justify 20kw as its not a very large difference.... bad batch of fuel, dirty filter, temp, wheel size... really i know a 20kw is 20kw but can you feel the power loss? off topic but what color is your vq, im from down that way

you can fell the power loss thats why im not happy. i dont wont to put the blower on if i'm lossing power some else then the wheels or conveter. i dont wont to be lossing the power from the trany if its the converter thats fine i can talk to the auto bloke and see what he say's. the stato is silver. i dont drive it much but when its finished i will. does diffrent gears change the power????? from 2nd to 3rd

If your worried about putting the power to the ground go back to the 17s, its not just the gearing but put it like this, the engine will struggle from a standing start in third because its taller geared, the bigger rim diameter is taller gearing, bigger isnt always better.

so boyracer you saying that the 20's would of made me lose that power?

The power is still there, but because your engine has to work harder to spin the higher gearing the wheels create, your not accelerating as quick and the dyno cannot show the same amount of torque.

If you want a pretty dyno sheet, get some 15's, 6.00 diff gears, standard converter, pump tyres to 60 psi etc. Who cares about a dyno sheet? You want torque and driveability on the street

I agree with mulkers.. Dyno sheets don't mean **** if you ask me.. Too many variables.. If ur just going to be a dyno donkey.. Then fill ur boots.. But when it comes to having a fast car its not just about what ur dyno sheet says.. And twenties are heavy as dude.. Thats prob ur problem