i have a million questions running around in my head for preparing to get my car dyno'ed

my mates dad has access to a uni dyno and his got a couple of engineering students possibly coming down to help out.

i have a 1275 sc12 set up with 1 3/4 Su ive gotten the toughest spring for a bs6 needle or somehting sounding similiar.

my question is how do they know what to cut the needle to from the dyno run?

how do i set up the car going in for the run? (standard with charger off or with charger running best i can?)

if they dont know how to cut the needle to suit what read outs do i need?

What should i set my spark plug gaps at and rough timing setting?

will running the engine tuned without the supercharger damage the engine with charger turned off?

if i go to a pro to get the tuning and needle done all as one job what am i looking at money wise?

i know itsa lot of questions but any help is really appreciated im getting close to having the car on the road
thanks chris

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Enjoy Chris

when is it happening?

I can help you with software to choose the right needle, but not till next week

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did I tell you that I won a trophy?

i havent confirmed a date yet but should be in about 2 weeks. at latrobe in bundooras engineering faculty

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Enjoy Chris

good-o

not sure what you mean by 'cut' the needle, but normally you wouldn't modify it, though you might file it thinner at points

what you'll need to do is set it up with a good mixture at a particular RPM (say 2000) and measure the height of the piston in the dashpot, to see which station (needle position) it is at, then at each RPM level (going up by 750's) check the mixture at the current station, determine whether it needs to be richer or leaner, and select (or modify) your needle as necessary. You can see that it's not a "1 session" exercise, unless you've got a big box full of needles

I've written a little web app that lets you filter by mixture at stations to get exactly the mixture you want for all stations, but it doesn't want to work on my web host, and I don't have time to fix it this week...

Obviously if you're going to modify a needle, it's best to start with a lean one, as you can't file metal back on

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did I tell you that I won a trophy?

ahh ok thats handy they have extremely precise lathing equipment that should be able to cut the the needle extremely small amounts i think he mentioned micro millimeters or something would i use a colour tune for the mixture?(which cylinder would be best?) how would i know i had the timing set up right?

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Enjoy Chris

I would guess the dyno operator will have an exhaust gas analyser and will measure the air/fuel ratio from that. Likewise I'd expect a competent dyno operator to get the timing spot on before fiddling with the carbs.

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Simon

The adventures of an owner builder in the Tallarook Ranges

ah k sweet

thanks for everyones help. ive never had a car dyno'd so i dont wanna waste their time with anything i should know before hand

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Enjoy Chris

best way of setting mixtures is with a gas analizer as SGC said
under full load an air fuel ratio of about 12:1 and under light load cruising about 14:1
the needle is modified in a lathe or drill press using wet and dry sand paper as you only have to remove small amouts of material at a time.
Set your timing idealy 1 degree retarded per PSI of boost so total advance will be about 35degrees NA and you will have about 7 psi boost so make total advance about 28degrees as a base figure you may have to advance or retard from there depending if it detonates, may want to retard it a bit more to be on the safe side though. If you have a standard ignition set up the plug gaps will have to be fairly small otherwise the spark will break down under revs and load so set plug gap to about .023" or .6mm

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4efte powered Clubman
supercharged 998 race car