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Boost Tuning

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I've just started on tuning for boost.

I recently got the adjustments for AFR on idle, and cruise.

I've started light pulls and the AFR is on target with my open loop table.

I would like to start on boost now. Currently, my max wastegate duty cycle is set to zero.

I'd like to adjust my target boost first then adjust the waste gate to suit.

For the logging parameters:

I want to find the exact parameter that measures my AEM boost gauge? Currently I have the boost gauge connected to a port on the intake manifold. But unfortunately these values are not matching up.

They are different values.

Can someone who has gone through this situation before help me out?


First thing, Boost Sensors are placed before the throttle, not after. Reading from the manifold can show a much lower boost pressure than is actually being generated by the turbo due to flow restrictions through the throttle body.

I would start out bu running the engine on the wastegate spring only. As this is the minimum boost pressure that the turbo can deliver, having this area well tuned is useful as it means that if the control fails back to the wastegate spring, then that area is safely turned. Once this are is tuned, then strat to add duty cycle onto the boost control to see what % DC generates boost wise. When you have an idea of the behavior of the boost control system, then you can start to build a boost aim table, and the control strategies needed to get the boost aim to be met.

First paragraph, Stephen, are you sure about the first sentence??? Especially as you're aware of the second sentence?

@Gord, for non-ecu boost control it's desirable to have an external guage/sensor referencing pre-throttle as it provides much better torque demand/control as the boost controller isn't fighting driver input so much if you are pedalling for traction. If you are using the ecu you have the flexibility of TPS scalar boost target on older systems or full torque demand modelling for newer/more advanced systems. Some people do run them post throttle, and if it's only a guage that gives you more information but if being actually used as a control device there is a drivability compromise with a post throttle reference.

Thank you.

If you have the reference before the throttle you're measuring the pressure there, not after the the pressure drop across the 'body' and the true value in the manifold, which you prefer? In either case there is going to be fluctuations as the throttle varies - opening the throttle will drop the pre', and increase the post', during transition, but I guess it's what one is comfortable working with?

I may have completely mis-interpreted the initial question, though, too.


What is the name of the monitor you're comparing your boost gauge reading to, and where are both sensors located?

Are you comparing looking at a gauge face to a logged value?

Hi Mike!

Yes, good question.

I am attempting to reconcile my gauge (AEM Boost gauge in PSI) to the manifold pressure parameter in RomRaider logger.

My AEM boost gauge is plumbed directly into the intake manifold (see picture). I am currently in Denver, CO. (Atmosphere ~11.9-12.0PSI)

Long story short. I have my MAF and fuel dialed in per Andre's videos. Now I'm working on boost tuning at WOT. I have my max WGDC set to zero to be safe and a starting Target boost PSI of about 16-17PSI coming on at about 59% TPS, with an rpm of about 3800.

My question is this: I can't be staring at a boost gauge as I'm flying down the highway in a 3rd gear pull. I need a parameter that measures actual boost pressure on RomRaider so that I can see if my target is over or under and from there I can make the appropriate adjustments.

What parameter can I log that shows me what my AEM boost gauge is showing me (i.e. the actual "pressure" above atmosphere) that I can take my measurements off and make corrections.

Thanks! ^_^

(see pics bellow)

Sorry Mike, I forgot to upload the pictures.

Also, for clarification. I have compared all the measured parameters for pressure; absolute, relative, corrected, "relative sea level"

none, of the parameters shows what the actual boost gauge is showing. So I suspicious that to get an actual boost measurement logged I need to calculate a formula of some sort to get the value that is on the boost gauge but, alas, I don't know what that calculation is.

(Ex. I tried PSI(abs) - PSI(atm) = Boost) but thats not what the gauge reflects.

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