Thanks for the kind feedback and very good team work
Brosome. For me it was a pleasure to work with you
. I really appreciate it.
The dyno time window was really challenging, as 24 different maps had to be optimized and overlaid optimally for final tune: WOT VTC, WOT fuel, WOT ignition timing. Finally we made 32 runs and there is still fine tune work of fuel and ign. timing left open. Beside that I had no access to the dyno result screen, only th written chat information of the driver, which had no headset. Sometimes I was asking the same question in the chat 7-8 times before the driver saw it on the screen and reacted, but hey, we made it
.
A made a comparison of both dyno results to see what have changed in the torque/power curve (s. below).
View attachment 102568
As the results were made on different dynos, I've tried to do a bit more fair comparison to show
Brosome what was the outcome for him. At around 6500 rpm there was a calibration point were both, VTC and ign. timing of both calibrations was exact the same, just fuel was +20 % more rich at the MRD tune. Normally at lambda around 0.92 you find the optimal flame speed with the 87x99 combustion chamber, the 86x86 tend to like it a bit richer. Here with the MRD tune we talk about a lambda of 0.68, which is far from fastest flame speed, so torque can be assumed to be lower. But anyway let us assume to have the same torque at 6500 rpm and use offset to correct the complete curves. The offset of torque at 6500 rpm of the MR to MRD tune is 6.8 wftlb's. Using the offset for the complete curve MR +6.8 wftlb, gives us following result.
View attachment 102571
For me this picture makes much more sense regarding it is the same engine and fuel, just a different tune with a 40° VTC limitation instead of a 50° VTC bandwidth.
Low speed cam:
The low speed cam in the MRD tune was set to 50° VTC. This is far from optimum, as too much exhaust gas stay in the comb. chamber, lowering both, VE and combustion velocity. The result is less torque almost everywhere below VTEC compared to the MR tune.
VTEC and High speed cam:
With the capability of 50° VTC an earlier VTEC is possible as high speed cam loves scavenging with this setup. With the 40° limitation only 4500 rpm VTEC was possible. Further on the 50° VTC is really missed in the MR tune, less torque everywhere up to the point where both VTC are the same, which is around 6450 rpm. The 40° limitation comes from the DC 3.2 cams and the Wiseco 11.1:1 piston, which were not clayed, so we had to follow the recommendation of DC. Better safe then sorry, even if it cost finest ponies! Beyond 6450 rpm VTC is below 40°, so both tuners are free to choose the optimum. MRD did steeply decrease VTC, while the engine loves to have more. I followed the engine and let it down only to 30°@8500 rpm, which tells us this particular engine has an amazing scavenging efficiency! Interesting, the engine didn't like more ign. advance at high speed cam, which was finally around at 25-26°. I am still thinking about that fact. Anyway, I love this setup and I learned alot about the K-series engines again. Thanks for that chance
Brosome!
Observations and interesting hints:
- we had a massive low load false knock issue, about 500 knock counts in 20 min commute. We've investigated this, reduced IAT by 15 °C, retarded timing by 5° in the knock areas and saw no single change in that. Beside that we checked for vibrating parts on the engine (none), we checked for piston slapping (none), we changed the knock sensor (no effect beside better signal quality), we checked leakdown test (fine), compression test (fine), we changed oil to lower knock likeability (no effect), we checked spark plugs and changed them (no effect), we clumped the low pressure blowby hose (no effect). So almost every knock cause was checked, maybe we missed something? What I observed was every time VTC rotates over 10°-30° there where 3-12 knock counts, also under higher load conditions from 1800-4000 rpm we saw massive counts added. I assume some of the noise came from the timing chain under relaxing and tensioning transition conditions on the intake side caused by the camshafts. The other one, which is bounded to engine speed and load and which can't be affected by ign. timing, maybe from valvetrain or pistons slapping. I am not sure about it, the video didn't make it clear to me. Maybe someone out there know some causes?
- I've made an eco tune for low speed cam, which saved about 20 % fuel from 1700-4000 rpm and idle to below WOT conditions. We agreed on to keep the tune as did come from the dyno. But the fact that about 20 % less fuel would be possible to the MRD tune of the low speed cam and low to higher load conditions was really surprising to me. This engine would definitive earn the greenhouse gas saving AWARD from the EPA with the MR tune in total...LOL !
The only thing I would still change, we worked on that point in some iterations, is the intake routing. Here there is some potential left beside some further bolt's on changes. The first would give a cooler and bigger distance to the knock margin, the later is definitely on intake side as this engine likes to breath more. She is hungry, not only for FUEL, also for AIR 😄!
Edit: the best compliment was made by
Brosome's wife, which commented according him during driving, it would feel to be different, much better... . If a female remarks this, it must be really a significant and positve change. Wife's are the honest and most neutral tuning rating instances, as they see the money flow, going into the car, more critical then the husband does it 😉!
