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Boost tuning on Evo X

Practical Reflash Tuning

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Hey tuners,

Can anyone help me out on understanding how you go about boost tuning on an evo x via open source re-flashing?

Basically the evo x has two boost control solenoids, a primary called the reactive solenoid and a secondary called the passive solenoid. I understand how they both work etc but here is the issue.

Both the tables are 3D tables of TPS, RPM and WG duty cycle. I understand how to go about tuning under WOT, but what about the remainder of these tables at part throttle? How do I get sensible values in there? The car I am tuning does not have a stock turbo or waste gate assembly, so surely the numbers in the tables will need to be changed everywhere.

Secondly, there are two other parameters on the evo X, one is a boost target load table and the other is a boost correction table. Again, both tables are also 3D, so my issue is the same as above on knowing how to tune the part throttle areas but in this case also the WOT area I am not sure how to approach this either.

I currently have both the WG duty cycle tables zero'd out so the car is running on WG spring pressure only. The approach I am leaning toward is maybe zeroing out the target and load tables completely then tuning the engine under spring pressure. Once that is complete I would raise the WG duty cycle table/s until I get the boost level I want the engine to operate at, then again tune the engine here. Part of me is telling me to leave the other two tables zero'd out and call it a day.....would this be wrong in doing? And if so, then what is the correct approach?

Any help would be appreciated.

I would highly recommend replacing the reactive solenoid with a 3 port as the factory one does not control boost well at all. The tuning process will be the same with stock or 3 port. First zero out the duty and correction table. you can leave the target as is since it will no longer have any effect since correction is zero. raise duty until you reach target boost and finish tuning fuel and timing. when done look at your load values and that will be what you put into target load table. then you can put correction back to how it was stock and that will turn the closed loop boost control back on. it will take some playing with to get it to where the correction doesnt make boost curve look all crazy. You may opt to not turn on boost correction and many times i do not or make it so ecu only makes corrections is boost is higher. if you dont want closed loop boost control just simply leave correction table all zero.


Thanks for your response. I have already told the owner to upgrade it to the 3 port, but we will work with the stock one for now. Right now the turbo is supplying 15psi of boost with the wg duty set to zero, it is also holding this 15psi all the way to redline so I think even with the stock solenoid I should see some decent results......I am only going to maybe tune to 20psi max anyways.

I was struggling to figure out if this system was closed loop or open loop with just fixed correction factors....can you confirm it is indeed a close loop system?

For sure the correction values will need to be reduced because of what I said above with the turbo providing much more boost on wastegate spring pressure than stock. I am leaning toward just leaving this thing purely in open loop. Hopefully Andre chimes in and gives his thoughts on that.

If I were turning it back on though....what about my next part of the question....for part throttle tuning.....how do I get some sensible numbers in those regions?


The EVO X is a true closed loop system, hence the correction table. On stock vehicles I've had reasonable results from the boost control system, even with the stock solenoid, although swapping to a 3 port is a good option.

You can zero the corrections and effectively run the engine in open loop however I'd really see no good reason to unless you're struggling to get good control with the closed loop active. If you want to run closed loop control then it's important that you alter your boost targets to suit what you're actually wanting to achieve though or the closed loop system will fight against you. Generally in terms of the 3D aspect of the wastegate duty tables, I'll concentrate my changes initially at the WOT area to achieve the sort of WOT boost curve I want and then extrapolate those changes that I've made (compared to the stock table) down into the lower TP areas of the table. Often I find that reducing the boost/duty cycle at lower throttle settings will give the car a more linear power delivery and this can help with the driveability of a very powerful car.

Hi Andre,

Thanks for the reply.

So initially Andre, then doing what my friend below has said, in zeroing out the correction factors initially while dialing in the base WG duty table and tuning the engine at WOT would be the sensible approach? Then as he has suggested, updating the target table, and then reinstate the stock correction factors but then maybe halving them since this turbo is running around twice the boost as stock on spring pressure alone?

What about the targets at part throttle? How would you deal with this? Obviously it would be tedious holding the car at steady state and logging wg duty cycle vs target load and then making adjustments so they are both aligned.....if you get what I am saying. How do you know the target you have at part throttle is a sensible number one, then how do you know the numbers in the wg duty table are aligned to this target? It's all a bit confusing to me.

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