Jetting software

Hi Matt, I have always found the best way to set jetting up is to let someone do it that knows what they are talking about using a dyno or experience with where the engine should be. Then when at the track depending on conditions run it richer in the first session and then make sure she revs out clean in top gear and you should be right if the dyno jetting was wet up well.
Brian Stockman has always set my engines up well and they have required bugger all stuffing around at the track after I get a base setting from him.
Wizzer gave me a great base line on where my engine was to be at its most efficient and this was spot on when the engine was run on the dyno.

In short that is what I would recommend you do otherwise you end up looking like the doc off back to the future :-)

No probs Matt, I can't speak highly enough of the work Wizzer did with my engine, on track it has been transformed. He would be a good place to start down your way and will give you a really good honest assessment of where its at.

Jase.

[quote author=RAM. link=topic=2336.msg25896#msg25896 date=1397032802]
Does anyone use or recommend any of the jetting software programs available, eg jet tech pro, Computech, NT Performance etc for a 250 twin? If so, are they effective?

Or are the traditional methods still better? Reading plugs, exhaust and piston crowns after sessions?

Any thoughts would be appreciated.

Cheers
Matt.
[/quote]

Hi Matt, to explain simply, firstly imagine the rotax max spread sheet type jetting chart. Then imagine wiping all of the recommended jet info off it and then over time, you check the engine via the traditional methods and you find that on 2 different occasions the engine is absolutely 'on the nuts' (but safe) and you then enter the 2 different RAD, mbar, temp altitude etc from each time into the spread sheet and enter the main, pilot jet, tube, needle type, venturi size, clip position, float type and all the other carb specs. Once these 2 different sets of parameters are in it, along with the weather settings and the program can then work out all possible scenarios for any given weather settings. (The rotax max sheet is a lot simpler than that of a modified engine plus you have 2 tied together and the rear one usually needs to be a little richer)

Also with a Tandem twin make sure the tandem timing is bang on before doing any of this work above! Both cylinders should be within 0.01mm @ 6mm before TDC of each other using 2 dial gauges with sparkplug adapters and turn the front crank only through the true rotation. Remember both cylinders share the same ignition and the ign timing is done on the front crank so if the rear one is out of phase by more than mentioned above then the timing on that cylinder will be out. If it’s 0.2mm out then that’s about 1.5 deg out in ign timing which absolutely makes a difference it jetting and power. Russell Anderson, Ian Harrison and myself aim for 0.01 – 0.00 at rebuild time and it should be checked every now and then.

And everytime you do ANY engine mods or change pipes, or oil or fuel you have to start again with the tuning data.

Here is a good explanation on the why's and how's of using a RAD gauge.
http://dtec.net.au/Air%20Density%20&%20Tuning.htm