Vanos Tuning

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all4bspinnin

Corporal
Jun 12, 2017
140
So, I've been out of the game for about 2 years and am just getting back into it. I am curious, what is everyone using now a days for their vanos?

I was previously using a modified map based on this thread http://www.n54tech.com/forums/showthread.php?t=21695

Have there been any other "discoveries" of what works best since then?
I have a couple tricks that I use when tuning vanos. It really depends on the turbo, manifold, etc. That will determine when i cut off spool mode. After that, I transition into widening the LSA. Most of the power you'll see is in the intake cam. I've found the exhaust cam helpful but not nearly as much. Adjusting the exhaust cam does help with removing pesky cylinder timing corrections. The factory spool mode tables are pretty good so make sure you use them.
 
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Jboyorak

Private
Nov 6, 2016
48
Maine
I have a couple tricks that I use when tuning vanos. It really depends on the turbo, manifold, etc. That will determine when i cut off spool mode. After that, I transition into widening the LSA. Most of the power you'll see is in the intake cam. I've found the exhaust cam helpful but not nearly as much. Adjusting the exhaust cam does help with removing pesky cylinder timing corrections. The factory spool mode tables are pretty good so make sure you use them.
Thank you for the reply. I have always run spool mode(and lean spool too). I have never saw the need to get rid of these. They are tunable tables that you can use to your advantage. It's good to know about the exhaust cam changes. I'll play around with these tips next time I get some "dyno" time.
 

Twisted Tuning

Lieutenant
Platinum Vendor
Oct 25, 2016
901
New York
Vanos, as stated, is completely dependent on setup. Do believe the hype of people saying "these are the best settings". Fact is every setup is a little different. And it takes time to find the sweet spot for a particular setup.

And always make use of spool mode. I don't see why anyone wouldnt use it. unless they just don't understand it. But i have seen people disable it.
 
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Jboyorak

Private
Nov 6, 2016
48
Maine
Thank you Twisted. I did quite a bit of virtual dyno testing on my old tune with different vanos changes years ago. But this was when I was mostly stock. I used to do a 3rd gear run for a dyno graph and a 1-3 gear run for acceleration data.
 

all4bspinnin

Corporal
Jun 12, 2017
140
Thank you for the reply. I have always run spool mode(and lean spool too). I have never saw the need to get rid of these. They are tunable tables that you can use to your advantage. It's good to know about the exhaust cam changes. I'll play around with these tips next time I get some "dyno" time.
Definitely. Vanos is awesome. The stock VANOS is pretty decent out of the box but definitely more power to be had. Before you get on the dyno, to save you tune time, you could have a couple bin files ready to go so you could flash and log.
 

Twisted Tuning

Lieutenant
Platinum Vendor
Oct 25, 2016
901
New York
Street tuning a car is always needed at some point. Dynos always will put different load on a car than a real street. so many car can react completely different between street and dyno.
 

[email protected]

Specialist
Apr 1, 2017
71
Street tuning a car is always needed at some point. Dynos always will put different load on a car than a real street. so many car can react completely different between street and dyno.
You can say that again ...

It can be at times a PITA though when I had to do the pulls for the customers and they have weirdly tuned suspensions or exhausts that make me feel like I am on a boat with fog horns ...
 

impuls

Specialist
Jan 28, 2018
61
What is actually the theory behind increasing the overlap and opening the exhaust valve later to improve spool?

Doing the opposite seems more logic:
-Avoid overlap to not cool exhaust gas and reduce
pressure.
-Open exhaust valve early to release expanding gases into the exhaust and increase pressure.
 

Rob09msport

Major
Oct 28, 2017
1,850
Monroe CT
I would think you want to push unburned mixture into the turbo so more thermal expansion plus you don't want back pressure if you want to accelerate the turbo. This is just a guess with no basis but what in see in my thought bubbles
 

impuls

Specialist
Jan 28, 2018
61
Could be the explanation, but every source I found mentions that overlap is bad for spool and advancing intake and exhaust is what you want to do.

So what is the different with the N54 resulting in improved spool by retarded exhaust valve timing?
 
Jan 31, 2017
295
Increasing overlap to improve spool usually works early on in the RPM range when there is a positive pressure differential cramming more charge into the combustion chamber and increasing VE - i.e. boost > exhaust manifold pressure. This is usually only the case around or shortly after full boost.
 

Rob09msport

Major
Oct 28, 2017
1,850
Monroe CT
Increasing overlap to improve spool usually works early on in the RPM range when there is a positive pressure differential cramming more charge into the combustion chamber and increasing VE - i.e. boost > exhaust manifold pressure. This is usually only the case around or shortly after full boost.
Like reverse scavenging effect right ?
 
Jan 31, 2017
295
Yeah if you like, end result is the same :)

At the end of the day the engine is an air pump, whose volumetric efficiency is strongly affected by Pi/Pe (inlet manifold pressure/exhaust manifold pressure), all else being equal. This is why your typical turbocharged torque curve exhibits peak torque shortly after peak boost rpm and gradually tapers downwards with increasing rpm. I've attached an interesting little .pdf from my collection detailing this, for your reading pleasure...
 

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Johnef

New Member
Aug 9, 2019
1
I will add from my experience in engine building for almost a while. Build a turbo engine like an allmotor engine, exception is slightly larger exhaust valve and steel valve. I usually run titanium intake valve since it sees less heat and it's bigger and my motors like to spin, so Ti helps with that.

The closer you can get boost : backpressure to equal 1:1 or 1:0.8 ( which is a dream for some, but not all) the more valve overlap you can run without congestion. Imagine 1:1 creates no push or pull during overlap. If it's 1:0.8 the exhaust becomes a vacuum.
Turbine A/R plays a major role in backpressure. What people don't get is, if you have an effecient system, it can carry a larger A/R.

Your motor will produce more horsepower with the same boost level, because it's not ingesting exhaust gase's that are unburnable on the intake stroke. And displaces the cylinders volume, depriving that bit of volume of having that much more clean air and fuel from intake port. Thus reducing your volumetric efficency.

Biggest hinderence is long exhaust systems on turbine outlet, increases back pressure, and restrictive or long path on the compressor outlet. I prefer an airbox for compressor inlet, air is much more laminar and if well placed cooler.

Exhaust headers I like to match the port exit for CSA and 1St step out a few inches depending on exhaust total duration, and step out at every 11" @ a 10% increase in CSA at each step. I do that until I reach the turbine inlet.
Twin Scroll is a must on 6 cylinder single turbo. Merge collectors I like 5° included angle leading into the turbine. This makes for a early, fast power and maintains drive all the way up.

Also tighten up piston to head clearance a bit, lay back the valve pocket reliefs on the intake side of the piston. Your piston acts as the floor of the port at TDC on the intake stroke. Those ridges create a lot of turbulence and back flow. Raise the intake ports from the valve guide leading up to the intake manifold , fill the floors for what your removed on the roof and smudge more. Fill the roof of the port between valve seat and guide. All with quality epoxy not JB weld.
Make sure your intake match the ports.

Do half of this stuff and you'll be amazed how well it responds.

I've built a lot of engines, but production BMW motors are jewels.

As a note I moch up the motor with cam timing at 0° for intake and exhaust Vanos. Works out around let's say 105 In LC and 105 Ex LC. I then move the cams around and measure how far I can go each way until things become tight. That way when I program Vanos I don't get in trouble guessing instead of knowing.

You have to check Piston to valve clearance and valve to valve clearance when your are trying things other than OEM.

I hope I offered value, I know most are hush hush. I'm a privateer grassroots.
 
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