WG actuator reference source

[JustenGT8]

With 2 choices for the WG reference (for 99% of applications anyway) i'm pondering the relative merits of each once combined with a decent EBC (Eboost).

Sourcing the reference from the comp housing is generally considered the most accurate and consistent as there's nothing else involved to impact the signal. While not a disadvantage as such, the quick signal feed means the gate will begin to crack earlier than a feed sourced from the manifold.....slowing boost response.

A feed from the manifold (MAP) generally improves boost response as the turbo gets to work longer before the gate cracks so boost increases faster. This setup provides quicker spool on gear changes as well, as the gate actually shuts (or starts to anyways) when the boost ref goes to vac. A potential disadvantage is if your turbo system is too responsive you'll get spikes...can be good or bad depending how far boost overshoots and for how long.

Now, my thinking is that a decent EBC is there to control boost, so giving it the best and cleanest boost signal you can is the way to go. ie signal from comp housing. A feed from the manifold could 'help' the EBC do it's job but i'm guessing on most systems (those not using huge laggy turbos) the likelihood of spikes etc would increase.

Sound enough logic or have i missed something about EBCs which might effect your choice of boost reference source?

[Z2TT]

Sounds good to me.

I chose the compressor housing as a source for accuracy.

Because depending on your setup, wouldn't you get lower readings from the manifold because of pressure drop?

[Cuts]

Like you said with an ebc they refference off the map and use the line on the compressor cover for the actual driving pressure for the actuator.

ive ran the actuator lines in a few cars off the manifold before with no spiking issues, just so long as the line is a reasonable size and gets a clean signal ive had no issues.

with the ebc though i do what the manufacturer specifies.

[JustenGT8]

Sounds good to me.

I chose the compressor housing as a source for accuracy.

Because depending on your setup, wouldn't you get lower readings from the manifold because of pressure drop?

Nah, if anything you'd get a higher boost pressure....if running off the comp housing you see X boost at comp housing and Y boost at manifold. If running off the manifold you'd now see X boost there. To maintain Y at manifold you need to 'turn down' the WG feed to compensate for the difference between X and Y

[Draven]

justen - my ebc is referenced from the mani and there's absolutely no spike... will post graph when I find it

[YLD-16L]

I've run off both the manifold and comp housing Justen, on mine the comp housing yielded the best results i.e. best peak boost control.

Run off the comp housing and if you want the turbo to spool faster just adjust the gain

Edit: Check how your new EBC works when powered on Justen as most keep the solenoid closed from the reference point until a preset gain level or MAP level so the theory of having it connected to the manifold to provide vacuum to close the waste gate between gear shifts etc becomes redundant with an EBC.

[oldcorollas]

does the comp cover have a lower than "actual pressure" reading, due to velocity of air past the port? or higher?

[YLD-16L]

does the comp cover have a lower than "actual pressure" reading, due to velocity of air past the port? or higher?

Interesting you say that Stu as a few people recommend taking the reference point from X cm past the comp cover, even though plenty of turbo manufacturers provide a reference point on the comp cover.

I reference about 70mm past the exit on the comp cover.

[JustenGT8]

does the comp cover have a lower than "actual pressure" reading, due to velocity of air past the port? or higher?

I couldn't say for sure Stew but rarely does a set WG pressure deliver more boost so i suspect they are pretty well equal?

[oldcorollas]

boost measured at manifold?

i guess i am thinkign that...
at cover, the air is hot, and moving fast, so the pressure is actualyl higher, but the velocity past port makes it look lower...
so that when air is cooled by the IC and pressure decreases (does it actually decrease? or just gets slower but at same pressure), the boost manifold = the incorrect low pressure reading from comp cover....

it, it is not "accurate" but it all sorta equals out and balances in the end?


as for manifold or turbo... there is not that big a volume of air between turbo and manifold, and when on boost, could be refilled in a few engine revolutions (2 or 4 or something?), maybe is more that the volume of intact tract, and resistance of IC and piping and manifold act as an R-C filter of sorts... so is better from comp cover, before the "filtering"?

[YLD-16L]

boost measured at manifold?

i guess i am thinkign that...
at cover, the air is hot, and moving fast, so the pressure is actualyl higher, but the velocity past port makes it look lower...
so that when air is cooled by the IC and pressure decreases (does it actually decrease? or just gets slower but at same pressure), the boost manifold = the incorrect low pressure reading from comp cover....

it, it is not "accurate" but it all sorta equals out and balances in the end?


as for manifold or turbo... there is not that big a volume of air between turbo and manifold, and when on boost, could be refilled in a few engine revolutions (2 or 4 or something?), maybe is more that the volume of intact tract, and resistance of IC and piping and manifold act as an R-C filter of sorts... so is better from comp cover, before the "filtering"?

Re: "balances in the end", I see what your saying and I guess as long as you get repeatable stable control it's somewhat irrelevent?

[JustenGT8]

Straight WG pressure, you usually see what the spring is set for or a little less. Yoi can see more top end if the WG is undersized and you begin to get uncontrolled boost creep.

There are so many variables (piping size, No. bends, IC eff (both temp and flow), engine eff etc etc) that's it's next to impossible to say what is balancing or conceling out what.

Needless to say, it generally works The trick is to get it working as efficiently as possible which you do by good design of each individual component.

the less 'boost' you run for a given mass airflow the better eh

[YLD-16L]

Straight WG pressure, you usually see what the spring is set for or a little less. Yoi can see more top end if the WG is undersized and you begin to get uncontrolled boost creep.

There are so many variables (piping size, No. bends, IC eff (both temp and flow), engine eff etc etc) that's it's next to impossible to say what is balancing or conceling out what.

Needless to say, it generally works The trick is to get it working as efficiently as possible which you do by good design of each individual component.

the less 'boost' you run for a given mass airflow the better eh

Speaking of efficiency, have you ever measured the pressure drop across your IC core? I ran some logs on mine on the weekend, essentially very little <0.5psi drop at 14psi and around 1.5psi drop at 18psi. Without thermocouples each side of the core it's hard to determine how much is due to restriction and how much is due to temp drop. Max temp post cooler for the day was only 46 deg C with 30 deg C ambient temps so the cooler seems to be working ok.......for the size of it.

I'm just trying to justify butchering the front end of my car for a bigger IC but the numbers I'm seeing aren't persuading me....apart from peak kw dyno numbers I happy with the current setup. Such a dilemma

[JustenGT8]

I've run off both the manifold and comp housing Justen, on mine the comp housing yielded the best results i.e. best peak boost control.

Run off the comp housing and if you want the turbo to spool faster just adjust the gain

Edit: Check how your new EBC works when powered on Justen as most keep the solenoid closed from the reference point until a preset gain level or MAP level so the theory of having it connected to the manifold to provide vacuum to close the waste gate between gear shifts etc becomes redundant with an EBC.

Thanks Shane. My preference is comp housing but physically setinng the system up is easier off the inlet manifold.

BTW, anyone know a source for those generic blue anodised boost control solenoids that most kits use....as soon as a brand name is applied the price triples i suspect?

[YLD-16L]

Thanks Shane. My preference is comp housing but physically setinng the system up is easier off the inlet manifold.

BTW, anyone know a source for those generic blue anodised boost control solenoids that most kits use....as soon as a brand name is applied the price triples i suspect?

The blue ones are a 3 port MAC solenoid, made in the USA. Occassionally pop up on ebay for between $60 and $90, they do come in different sizes too so keep an eye on that.

You're not interested in using a couple of XR6 Turbo boost control solenoids? Under $40 each new from Ford, I think the last one I bought was $36 or so. They work well, 3 port solenoid, look pretty plain.