This is a external wastegate setup.

 

Look at the graph again. It's holding 26 psi all the way until recline.

 

That's exactaly my point. It's not holding boost. He said the WGDC is cranked up. If the turbo was at its flow limit you would see pressure drop off as rpm increased. What pressure wastegate Spring are you using? what configuration do you have for your wastegate pressure piping? What BCS are you using? Just trying to help. Maybe it's just tuned for a flat boost curve? Probably is.

 

You may want to try method 2

 

Please point out on his graph where it's not holding until redline............

Also, all his setup details (sans gate) was posted several pages back..........

 

If he can't get over 27psi and other very similar setups are getting 34-35 psi............well it's not holding boost like it should. Sorry but I haven't read that far back. Should be able to get another 5-6 psi around 5k then slowly losing boost as rpm increases. But like I said before maybe it's probably tuned for a flat boost curve not max power.

 

27psi does seem pretty conservative for E85. Does the turbo have a speed sensor?

 

No. And that's problem number 1.

 

..............then I would recommend you revisit prior pages a a majority of your statements have been addressed

 

Oh really?

Sorry to have wasted everybody's time. Figure it out yourself.

I see you have a grand total of 30 posts.... Go back into your hole

 

Agreed. Given how fragile EFR's have proven to overspeed, it seems like its well worth a few hundred $. Plus, then your tuner can more accurately see whats going on.

 

30 posts with a registration date of.................Wait for it............. OCT 2002!!!! . I lurk as I had no reason to post until recently. I have been through more turbos than you have been through underwear this week alone

There is "nothing" here to figure out. All the information was presented by Brian as requested.............but since you didn't bother taking the time to read, you wasted several posts. But to each his own I guess............

P.S. It's the internet, don't be so sensitive

 

Time to eat some humble pie my friend. Bring the fastest car you have ever tuned and $1000 to the shootout, we will settle this like men. You have no idea of my experience with forced induction so that statement makes you look ....like a punk kid.

Everybody I'm sorry for the off topic.

 

Everyone chill.

Correct: The setup holds roughly the same boost pressure all the way to redline. But the turbo is going to be spinning a whole lot faster and moving a lot more air to deliver 27psi @ 8000RPM than the same 27 psi @ 4000RPM.

A perfectly flat boost curve from spoolup to redline usually means that the turbo could deliver more air (thus more pressure) at the lower RPMs, or that the turbo is being spun outside of its efficiency range at the upper RPMs. Usually the truth is somewhere in between, but fortunately it's not too difficult to install a shaft speed sensor on these EFR turbos to get some actual measurements either way.

As much as people like to chase the flat boost curve on these forums, it's usually not the optimal way to run a turbo. There are plenty of other good reasons to artificially cap boost at lower RPMs (limiting torque, improving driveability, etc.) but iit sounds more like the boost control system as a whole just isn't capable of holding more than roughly 27psi of boost at any airflow/turbo speed. In this case, "holding boost" means absolute pressure at lower RPMs, not "holding boost" to redline, which implies spinning the turbo faster as RPMs increase to keep boost constant.

For an example of what this looks like without running in to a boost pressure ceiling, see the STI links I posted above. The torque curve peaks after the spool threshold and then steadily decreases with RPMs, as does the boost pressure. That indicates that the turbo is probably being spun right up toward (more or less) an appropriate turbo speed line on the compressor map, then staying near that line until redline (Ideally). That's why the horsepower line is mostly flat, at least until the high-RPM trail-off you get as efficiency begins to fall. In very broad strokes and ignoring a million other variables here, Airflow * Efficiency = Horsepower, but remember that 27psi at 4000RPM is going to be half as much airflow as 27psi at 8000RPM in the ideal case (which is far from the truth, but you get the idea).


Of course, it's another debate entirely as to whether or not that additional low-end torque is desirable or useful for Brianawd's use case. I'm still surprised that the setup isn't spooling just a few hundred RPMs faster than it is, though.

 

Very well put Construct, thank you.