Pages: [1] 2
Author Topic: Free Flowing Exhaust Effects on a Turbocharger  (Read 4191 times)
turbo944s2
Full Member
***

Karma: +1/-0
Offline Offline

Posts: 59


« on: July 21, 2018, 11:51:48 AM »

I have a 2008 Audi A4 with a built motor , custom tubular manifold, 3 inch exhaust no catalytic converter, equipped with an external wastegate(14psi Spring). When I first started driving the car and attempting to tune it, I noticed that I didn’t have much control over the boost (overboosting, jerky, inconsistent, temperature based inconsistancy, etc). One day I added a catalytic converter and I noticed the boost was much lower, the spool was slower and the boost never went over 22 psi. At that time I was upset about how much slower the turbo spooled and I couldn’t wait to remove the catalytic converter. I adjusted the duty cycle and got the turbo boosting over 25 psi again.

Last month I removed the catalytic converter and now the car overboosts again. I believe I came up with a reason of why the car is overboosting. On Turbosmart’s website they mention that the wastegate cracking pressure is higher on the bench then on a car with backpressure. My theory is since I don’t have a cat, my downpipe, and exhaust are 3 inches, there isn’t much backpressure acting on the valve to assist with opening the wastegate(the car is totally dependent on diaphragm pressure only to open the valve). It is my opinion that lowering the spring pressure will  allow the N75 to control the boost better. Does this sound accurate?


Logged
zamzu
Jr. Member
**

Karma: +3/-76
Offline Offline

Posts: 47



« Reply #1 on: January 06, 2019, 03:00:59 AM »

Hi,

I've noticed the same. After changing exhaust to 3" it is really hard to control boost (with stock turbo on).
Logged
nyet
Administrator
Hero Member
*****

Karma: +440/-60
Offline Offline

Posts: 10025


WWW
« Reply #2 on: January 06, 2019, 12:33:12 PM »

Absolutely. Less backpressure means you need significantly less spring. At some point, though, you may lose spool rate if you go low enough.
Logged

ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your experience.
turbo944s2
Full Member
***

Karma: +1/-0
Offline Offline

Posts: 59


« Reply #3 on: January 06, 2019, 01:22:56 PM »

I dropped from a 15 psi spring to a 10psi spring, the boost still spikes but it's controllable.

Sent from my SM-J327P using Tapatalk

Logged
zamzu
Jr. Member
**

Karma: +3/-76
Offline Offline

Posts: 47



« Reply #4 on: January 07, 2019, 10:57:28 AM »

Is the reason for overboosting the same on stock turbo (internal wastegate)? I changed exhaust to 3" and at the same time did the clutch (single mass by ecs). Now it doesn't seem to follow the LDRXN at all. Before I was running 1.1 bar pressure, now it goes up to 1.5 and stright to limp mode.
Logged
nyet
Administrator
Hero Member
*****

Karma: +440/-60
Offline Offline

Posts: 10025


WWW
« Reply #5 on: January 07, 2019, 11:03:06 AM »

Is the reason for overboosting the same on stock turbo (internal wastegate)? I changed exhaust to 3" and at the same time did the clutch (single mass by ecs). Now it doesn't seem to follow the LDRXN at all. Before I was running 1.1 bar pressure, now it goes up to 1.5 and stright to limp mode.

Maybe. No point in guessing. Log. Try with N75 disconnected to make sure WG lines are intact. etc.
Logged

ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your experience.
zamzu
Jr. Member
**

Karma: +3/-76
Offline Offline

Posts: 47



« Reply #6 on: January 17, 2019, 12:04:22 PM »

Tried to log, but as here is winter and -10c outside / very icey roads (making it impossible/useless to log wot pull), but something I see from the log... are my injectors too small to take it all / can it be the cause of overboosting (I mean that 3" is sucking it try) and having no control of it?

Also the MAF readings are maxed out...

« Last Edit: January 17, 2019, 12:46:03 PM by zamzu » Logged
nyet
Administrator
Hero Member
*****

Karma: +440/-60
Offline Offline

Posts: 10025


WWW
« Reply #7 on: January 17, 2019, 01:27:21 PM »

Please post the original log.

Or learn how to use ecuxplot properly. Preferably both.
Logged

ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your experience.
zamzu
Jr. Member
**

Karma: +3/-76
Offline Offline

Posts: 47



« Reply #8 on: January 17, 2019, 02:14:15 PM »

Please post the original log.

Or learn how to use ecuxplot properly. Preferably both.

Here it is...
Logged
nyet
Administrator
Hero Member
*****

Karma: +440/-60
Offline Offline

Posts: 10025


WWW
« Reply #9 on: January 17, 2019, 03:56:14 PM »

Not sure why you think injectors have anything to do with it. Did you disconnect the N75 like i asked you to?

From that log you just need to pull back on IMX significantly
Logged

ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your experience.
zamzu
Jr. Member
**

Karma: +3/-76
Offline Offline

Posts: 47



« Reply #10 on: January 19, 2019, 09:16:24 AM »

Thanks nyet, pulled back IMX and it´s all good and contrallable, need to play with it some more to get it perfect. Didn´t know about that WGDC stuff before since I was almost stock before. Did also new injectors (530cc 0280158117) and SAI off...I feel super great, thanks again.

Now I need to figure out why there is boost spike after I let off the throttle...
Logged
opticaltrigger
Full Member
***

Karma: +3/-0
Offline Offline

Posts: 80


« Reply #11 on: January 26, 2019, 02:47:35 PM »

I have a 2008 Audi A4 with a built motor , custom tubular manifold, 3 inch exhaust no catalytic converter, equipped with an external wastegate(14psi Spring). When I first started driving the car and attempting to tune it, I noticed that I didn’t have much control over the boost (overboosting, jerky, inconsistent, temperature based inconsistancy, etc). One day I added a catalytic converter and I noticed the boost was much lower, the spool was slower and the boost never went over 22 psi. At that time I was upset about how much slower the turbo spooled and I couldn’t wait to remove the catalytic converter. I adjusted the duty cycle and got the turbo boosting over 25 psi again.

Last month I removed the catalytic converter and now the car overboosts again. I believe I came up with a reason of why the car is overboosting. On Turbosmart’s website they mention that the wastegate cracking pressure is higher on the bench then on a car with backpressure. My theory is since I don’t have a cat, my downpipe, and exhaust are 3 inches, there isn’t much backpressure acting on the valve to assist with opening the wastegate(the car is totally dependent on diaphragm pressure only to open the valve). It is my opinion that lowering the spring pressure will  allow the N75 to control the boost better. Does this sound accurate?



Out of interest, what size is the valve in the external wastegate.

O.T.
Logged

"It is dangerous to be right, in matters where established men are wrong." ....

Voltaire
nyet
Administrator
Hero Member
*****

Karma: +440/-60
Offline Offline

Posts: 10025


WWW
« Reply #12 on: January 26, 2019, 04:03:07 PM »

Now I need to figure out why there is boost spike after I let off the throttle...

Bad DV or N249..
Logged

ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your experience.
fukenbroken
Hero Member
*****

Karma: +62/-7
Offline Offline

Posts: 784


mk4 1.8T AUM


« Reply #13 on: January 26, 2019, 09:32:55 PM »

you should tune PID for a tighter wg and this aint doin with a cat. wiki covering thats pvdksdk things and with proper tune even on a small turbo (btw is it stock one?) and 14psi wg you can achieve great results with wot and partial throttle
and check your fueling. idc 100% @3k wtf?
Logged
zamzu
Jr. Member
**

Karma: +3/-76
Offline Offline

Posts: 47



« Reply #14 on: January 28, 2019, 09:46:27 AM »

Bad DV or N249..


Forge splitter valve and N249 pluged/bypassed
Logged
Pages: [1] 2
  Print  
 
Jump to:  

Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Page created in 0.023 seconds with 18 queries. (Pretty URLs adds 0s, 0q)