VANOS Question

[mj6234]

I have been self educating on tuning, and think I have a pretty good handle on most concepts. I have read V8Bait's spreadsheet and more threads than I care to admit.

I have GC Lites, and have been playing with VANOS trying to improve the spool from the default JB4 BE flash maps, and have been successful by advancing intake/retarding exhaust in the spool map.

I know VANOS also affects dynamic compression, and more overlap is likely to lower dynamic compression. Just from thinking through this, it seems like a way to maybe mitigate areas where timing drops sporadically occur without directly changing timing? I noticed when I increased overlap in the spool tables (and changed the regular VANOS Warm tables to be closer to the spool tables), the timing drops I got around 3500-4000 disappeared. Normally I'd get pulls even with 3* of timing in the main map on a couple of cylinders at 17psi. After this change, things disappeared and were far more stable. Assume my changes lowered dynamic compression, and the timing was better tolerated. Not sure how to decide if changing VANOS is better vs lowering timing in the main table, but it already seemed very low at 3*.

I am tracking the impact of things using Virtual Dyno on the same plot of land to keep things consistent. It looks like spool and power improved according the log comparison.

I normally run 91, but do have access to E85. I am going to work up to that I think. Also currently have the JB4, but my goal is to remove and flash tune everything myself and VANOS is one of the gray areas I want to understand. Let me know if my thinking if totally off or if I am on the right track here.

 

[Asbjorn]

@carabuser

 

[carabuser]

You're certainly on the right track. I've not experimented much with VANOS as I still have stock turbos but I have tried using the COBB tables in the past and found they seemed to cause more timing corrections and offered no increase in power.

The MHD OTS maps use stock VANOS from what I've seen. WIth the JB4 backend maps it looks like they use stock VANOS for the pump and the COBB values for the race map.

You should be able to go flash only relatively easily. The only thing that the JB4 is currently doing is controlling wastegates, once you remove it you would need to dial in the boost control from your flash instead.

 

[mj6234]

OK, I will keep tinkering. Obviously the dyno is the true tell all, but going to have to settle for my my stretch of road that I can safely log on. After looking through my logs a little more, I picked up a correction right after 5000, looks like I overadjusted things in that area. Will back off a little and relog to see if I can get something clean there.

I also noticed in the 3500-4500 range, previously the Avg Ignition in that area would always climb 0.4 - 0.5 before going back down. This time it dropped 0.3, I guess more proof that the timing was more stable.

 

[carabuser]

Timing corrections come and go, you can't really make assumptions on single logs.

Also VANOS can have an effect on the actual load and alter the timing target. The LSA of the VANOS is used in the volumetric efficiency tables that determine the target boost, so if actual boost increases the load will increase.