| Theory is a proposed explanation that is still subject to experimentation. Opinion is based on what a person believes, how the opinion offered was reached can vary greatly. It is amazing how many opinions are given based on what they have heard.
Many experts are just people that fell into their trade, their opinions many times are based on what someone taught them rather than what they tested themselves. Both of the above are great places to start, but I have always been the type of person that needs to experiment for myself with real world testing. My opinions are opinions like anyone else, I can be wrong as I am still human and we all as humans make mistakes and can be misguided at times. When I offer my opinions, I offer them based on my experiences, like anyone else, my experiences are what they are based on what I know at that time, we are all always learning. When you have had the privilege of being able to dyno cars almost daily, the data you collect offers you a lot of insight into what offers gains and what does not.
I learned a lot that could not be taught by experimenting on my own cars, I made changes in every direction with many things just to learn what would occur making those changes.
Most times the changes showed expected results, but surprises also occur from being curious, and from not being afraid to take an approach that is not common.
When I find things that work, I use the same approach on customers cars. From the experience gained from working on the same type of car for 25 years, With the data collected from tuning hundreds of Z32’s on a dyno, from making thousands of runs on a dyno with Z32’s, I have drawn what I feel are reasonable conclusions from the data that make me believe the conclusions are accurate. I find it amusing that you believe an incorrect VTC release RPM caused us to draw a conclusion about a cam. When you own the equipment to measure the engines power input, and own equipment and software to easily make changes to the VTC release, it is extremely simple to rule a simple tuning adjustment your suggesting.
The VTC release RPM is about the easiest adjustment a tuner can make. You simply make 2 dyno pulls to find the correct release point.
You make a dyno run with the VTC on the whole run, you make another run with the VTC off the whole run.
When the VTC is on the whole run, the low end will be much greater, but the power will drop off in the top RPM area.
When the VTC is off the whole run, the low end torque will suffer, but the top end will make more power.
To find the optimum VTC release, you simply overlay the 2 charts, find the point where the 2 highest power points intersect, enter that RPM in the program for the VTC to release. This test and adjustment always offers a smooth power band with the most overall power. The conclusions drawn about cams is not from 1 or 2 cars with these cams, we have seen it over and over more times then I could count, we have tried the traditional testing for VTC release with these cams, we have also tried testing different VTC releases in the program to see if we could minimize the lump in power and tried every possible trick to maximize the power band, we always came up with poor results.
Testing has always shown that performing the normal test of on all the way, off all the way testing always has shown the best VTC switch point even with less than ideal cams. With the mentioned cams, the power is lumpy when the VTC is off the whole way, it is lumpy when the VTC is on the whole way, it is lumpy when switched at the peak power points.
With good cams the power is smooth with the VTC off the whole way, the power is smooth with the VTC on the whole way, the power is simply less on the low end or top end.
Turning the VTC off too soon or too late can cause a dip in the power curve. Switching the VTC at the intersection of the best on/off will provide the best overall power and is smooth. Ken’s cars are not the only turbo NA’s running around; they are also not the only ones we have tuned with good results. Nissan over engineered these cars, both the NA and TT can handle double the stock power output without failure when tuned correctly. Compression / Timing / boost
Octane limits what is safe with the 3 items above, with low/moderate octane, timing and boost require being lower with higher compression. With high octane, all 3 can be raised safely with the best overall results.
We find similar power results on low/moderate octane when correctly tuned with different compression ratios with everything else being the same.
The reason is you have to tune out the added power of higher compression by lowering timing and boost to prevent knock.
We have seen high compression and low compression set ups with both TT and NA heads, the stock NA heads have always shown less power than the stock TT heads on the dyno with all else being the same.
I believe the results we have seen are simply because stock NA heads flow less, turbo set ups thrive on flow
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