2015 breakout. I am installing 255 cams. When I look at the pro tuner maps for the 255's, my saved tune is much richer in all areas. The only difference I really see are the spark advance tables.

Is their any reason I can't copy the 255 spark advance tables to my current map and go with it?

 

Hi, the pros will tell you it's not about sparks ...well it is, but the first bit is mapping your airflow through the rev range at different throttle opening or MAP pressures. This is your VE tables.

With that nailed, you then look at the rest of the tables.

The stock map for the high output 103 with the nearly a 255 cam in it seems to have much lower VE in general compared to the stock 103. I'm tuning a 103 with Andrews 57h and see the autotune agreeing with this - it is taking lumps out of the tables.

If I was a betting man, I'd guess you might need to drop some of those VE by a good lump, but it depends what you meant by your saved tune being richer?

Having said all that, what A/C and Exhaust will be a factor, and where did you get your current map?

You will need to do some tuning or believe in someone else's 255 map ...mind you, the ones I've compared have been quite different.

cheers n good luck
Gordon

 

My current map is from a dyno tune with the stock cams. I have the open air cleaner and a thunder header. Bike runs great. But would be nice to have a bit more low end grunt.

 

Hi Gator, by all accounts the 255 is going to do that for you but the maps are quite different stock vs 255.

I take it you can save your current tuned map for posterity. If you can, then no harm trying the 255 maps once you get the cam in.

By the way, why did you think yours was richer? comparing VE tables or the AFR table?

cheers

 

The only reason I figured it was richer. Is I had it dyno tuned. I was looking at the afr between the two maps and I am richer at the aspect. Also the VE tables are running higher numbers then the 255 map. I thought the higher the number the more fuel will be delivered. Based on these tables I assumed my tune was richer than the 255 map. Or am I mistaken

 

That is how I understand the VE values as well, although I'm not sure why the efficiency would go down so much at lower revs with a cam and exhaust with quiet baffle that should be helping in that area but some of mine dropped by over 20 (nearly 30 in a couple of cells) - but it doesn't stink of petrol anymore, runs smooth from nearly idle and pulls like a steam train

Different cam, different airflow so if it doesn't need as much fuel at that revs/throttle position then so be it.

Once the VEs match your airflow characteristics the AFR table can be whatever you want, of which there seems to be a gazillion suggestions - your dyno'd AFR table may be as good as any.