Discussion and questions related to the course Boost Control
What is the purpose, benefit/downside to four port boost controllers. How are they piped on externally waste gated setups
but i have been told they are a lot more sensitive to duty cycle changes than a 3 port.
can anyone confirm this and are there any circumstances that contribute to the sensitivity? High boost low boost etc.
With a 4 port solenoid you can completely remove pressure from the bottom port of the wastegate (with a typical 3 port installation this side of the wastegate always has boost pressure applied to it). This provides the potential for a much wider range of boost control than a 3 port solenoid can achieve since with the 3 port we always have exhaust pressure acting against the wastegate valve and trying to open it, as well as the boost in the bottom of the wastegate head also trying to open it.
To give some example, with a 10 psi spring in a wastegate, you may be able to achieve a maximum boost pressure of perhaps 25 psi with a 3 port (hence a range of 15 psi) but a 4 port may allow you to reach 35 psi or thereabouts.
can this be applied in principle to a blow off valve on the intake tube before entering the throttle body and supercharger to control over boost and what air valve bodies are most utilized for this application
You could make it work but if you're really concerned about overboost on a supercharger, size the system correctly so it doesn't tend to overboost in the first place, and put a fuel cut in for emergencies.
do you recommend this setup/where have you used it before? Jay's tech tips on realstreet youtube channel makes it sound like the way to go. Plumbing wise the what are the 4 ports, 1 normally closed (to the top of the WG as in exhausting normally) 2 normally closed (to the bottom of the waste gate holding it closed against engine exhaust pressure) 3 input 4 vent? is duty cycle set up the same on a 4 port as a 3 port? IE will the parameters be the same, starting with open loop and then adding in your PID for closed loop? For background I'm new to tuning and using a AEM infinity on a dual externally waste gated twin turbo system.
It really depends what range of boost control you need. Certainly the 4 port will give you a wider range of control than a 3 port solenoid can. Realistically the only downside I see with a 4 port over a 3 port is that the boost will be a little more sensitive to changes in duty cycle.
I was just about the create a new topic on 4 port boost control solenoids when I saw this post.
Andre, why wasn't the 4 port boost control solenoid described and dealt with in the boost control course?
@Chris, we may add a module on these solenoids. In my own experience they still aren't that common outside of drag racing, however I'll admit they do seem to be gaining popularity. The reality though is that other than the plumbing side of things, the operation and tuning is identical.
Thanks a lot for the response and understood.
I use 4-port for my track car and coupled to TPS based target boost. This makes it feel kind of like a S/C or electric car in the way that you adjust boost with your right fot when in corners so it's very easy to balance the car throughout the corner without jerks from on/off boost. I use a 0,3bar spring so I get a very wide boost range.
On wet track I can set my boost to climb with rpm so I can floor it without loosing traction when boost comes on.
However on my car it's very sensitive to setup. It's not just to set a base duty and simple PID since 1% duty can make a big difference, this means that eg IAT seems to have a big effect among other factors.
Keep the hoses to the waste gate and MAP sensor as short as possible and shield of the solenoid from heat.
So on my Haltech Elite 2500 I use:
-Linear IAT correction
- 3D table for Proportional with Boost error/Target Boost And I try to find the best P for every target boost level.
- 3D table for Integral with Boost error/MAP Derivative
In this way P can work to get fast spool without Integral wind-up and I get control of when Integral starts to add control after boost stabilizes.
First try to run open loop set the duty to a fixed value and then make some consecutive runs, starting with the engine just warmed up and log all runs to see if you need to add corrections to keep the same boost.
When I do this boost goes lower every run and if I keep adding base duty it will overboost next time I run after it has cooled down.
So in summery make a base duty table that gives a linear steady boost and then add corrections and clever PID-control and it will be rewarding to drive in the end :)
Mattias that's very interesting, I've heard of boost by gear but not TPS based boost. Thank you for the input I'm definitely going to look into that
TPS duty correction is quite common and works well.
It's a little different to setup TPS target boost correction, I'll attach a picture of how I've done it so that it works in closed loop on any of my targets that I set with a rotary switch.
MattiasS would you mind sharing your entire map?
I'm very curious to see how your boost control is set up over all.
I made a summary in one image, at this stage it's only mapped correctly at 100kpa and I'll most likely won't finish it since I was in the end of breaking in my engine and now my block finally cracked after 9 years of use and abuse. So I might not keep this engine at all since I've been planning to do an engine swap before this happened :)
Note that I don't use LTT, every time I try it it just messes up the boost control after a while.