RCVTR

I thought some of you would be interested in my latest OCMD project:

I mentioned a while back that my bike didn't run well after installing a Durbahn/Turnone airbox. I had installed a free map that I guy sent me, but it was for an Akrapovic full exhaust system. I have a Moriwaki full system on mine.

I left the bike to be tuned By Kevin Murray, of MCE Racing at Thunderhill Raceway. Super nice guy. Very methodical. He got it mapped to his satisfaction. I haven't seen the torque/HP curves yet, but I had a long talk with him about the results. The thing was mapped super rich and down about 15 HP.

Meanwhile,an Akrapovic exhaust system came up on ebay. I have read that it was a really good system for the RC51. I told myself I could sell either one of my systems for about the same price and talked myself into it. It is a beautiful, well-built and well-designed system. Upon close examination, I discovered that the collector on the Akrapovic system is an entirely different philosophy than the one used by Moriwaki. It's not surprising that the map was so far off.

So then I thought I would approach it from the standpoint of assuming that the maps that the guy sent me were good for the Akrapovic system. He had sent me two maps. One for the Akra exhaust and a stock airbox. The other one for a Durbahn/Turnone airbox. I printed out the two maps. The one for the Durbahn airbox said BK Porshce Racing Edit. The ONLY difference was 9s in the closed throttle column, instead of 0s. I hope he didn't pay $300 for that!

I started comparing all the various maps that I have collected over the last year. One from Dan Kyle with a stock exhaust system - I used this as a baseline. One from Bob Hayashida for the full Moriwaki exhust system and the one for the full Akrapovic exhaust system, each with a stock airbox. I entered the maps into Excel, so I could plot them and got some interesting results.

If you look at an PowerCommander EFI map, what you see is a grid of cells with numbers in each of the cells representing changes to the stock fuel injector map, corresponding to changes in the time that the injector is held open, for each combination of throttle position and RPM in the table. So, if I assume that each map represents corrections to the stock map to create optimum fueling with the corresponding exhaust system, then I should get a fair representation of how the mass airflow rates for the systems compare. I then used the map for the stock exhaust system and did a cell-by-cell subraction of the fuel adjustments to get a direct reading of the changes made by each exhaust system. Positive values should indicate where the exhaust system creates higher mass airflow, which should indicate more torque. It seems the Akrapovic system may be the best choice for a track application.

I don't know how valid this is, because the maps were created by 3 different tuners on 3 different days in 3 different locations, wih 3 different O2 sensors. But I don't believe there are as many variables as with torque and HP numbers. I believe the results may at least be useful from a qualitative perspective. It will be interesting compare the torque curves.

I get to see how the bike runs, with the Turn1 airbox this weekend.

mikstr

Thanks for sharing Hope the Akra works well for you (am hapy with mine on the VTR). Oh, and don`t forget, we want dyno numbers!!!!!

Have fun at the track (just remember, rubber side stays down)

gordonjj

Exhaust SystemsDoes dyno numbers really means so much? Until I came across this thread I thought the performance was more important.