MIVEC tuning
#303
John how about an image of the stock US IX map with the jdm map below to allow to see the differences side by side. It would be a good reference post. btw awesome job
#308
OK, thanks to everyone in this thread for your insight.
I'm now using this VVT map (please note, I've re-scaled for 7500 and 8000RPM rows):
My boost profile is below, and as such, I wanted to model my VVT map after it:
3000 - 4000 >> 24psi
4000 - 5000 >> 23psi
5000 - 5500 >> 22psi
5500 - 6000 >> 20psi
6000 - 6500 >> 19psi
6500 - 7000 >> 17psi
Here's my new DLL dyno:
I'm now using this VVT map (please note, I've re-scaled for 7500 and 8000RPM rows):
My boost profile is below, and as such, I wanted to model my VVT map after it:
3000 - 4000 >> 24psi
4000 - 5000 >> 23psi
5000 - 5500 >> 22psi
5500 - 6000 >> 20psi
6000 - 6500 >> 19psi
6500 - 7000 >> 17psi
Here's my new DLL dyno:
#309
I was thinking about the theory of MIVEC, and the cylider evacuation that occurs during the events, and it's ability to create the maximum evacuation of each cylinder through the phasing of the camshafts. My question in preparing a VVT map is; would you differ a map that has a tappering boost curve as opposed to a boost curve that might otherwise be flat? From the point of view that I am looking at it, one could adjust the VVT so that the it might not be so radical during a non tapering boost curve, due to higher cylinder presures, and the opposite during a non tapering curve. Or did I miss something in my learning?
#310
You have the general idea. Optimum VVT mapping will vary, depending upon the turbo size, boost pressures run, spool characteristics, base cam timing, etc. There is no 'one size fits all'. When there is a major mechanical change, VVT will require remapping for best performance.
#311
The other factor to consider is exhaust gas backpressure. If you have a smaller exhaust housing on a turbo and you have a restrictive exhaust, you have more backpressure to deal with. This would limit the range where you could advance the cam and get higher compression. When the ratio of EGBP to manifold pressure gets higher, you will get more reversion when you have overlap during the exhaust stroke. This leads to poorer evacuation of the cylinder and no more power being gained. You still closed the intake valve earlier during the compression stroke which leads to higher compression, teamed with the hot exhaust gas trapped in the cylinder, makes the air fuel mix more likely to preignite/detonate. That's at least my understanding. Retarding cam timing at higher RPMS where you have an unfavorable ratio of EGBP:MP creates lower cylinder pressures, but more complete evacuation of the cylinders.
#312
I would like to post a follow up to my mivec changes. I recently used the info in this thread to build a mivec map. It works gear except when the car is cold it is very throttle on off sensitive. Take about 5 minutes before I can smoothly transition with various throttle inputs.
I have switched back to the stock map and this behavior goes away so I know its directly related to the mivec map.
I have switched back to the stock map and this behavior goes away so I know its directly related to the mivec map.
#313
I just installed this map and took her out for a test drive. I can say that midrange torque is improved considerably. Wondering what effect increasing the advance to 30 would do for my car running one of the more aggresive maps. Currently I have a TBE and have raised the boost table to 255 all the way down and have leaned the upper area on the high octane slightly. I know I really need a wideband but I am only making slight changes to the fuel tables till I can get some cams and then do a proper dyno tune.
#315
I just installed this map and took her out for a test drive. I can say that midrange torque is improved considerably. Wondering what effect increasing the advance to 30 would do for my car running one of the more aggresive maps. Currently I have a TBE and have raised the boost table to 255 all the way down and have leaned the upper area on the high octane slightly. I know I really need a wideband but I am only making slight changes to the fuel tables till I can get some cams and then do a proper dyno tune.
Just curious is all