Controlling boost. Stock bottom end
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Controlling boost. Stock bottom end I'm in a situation here. I understand, I need a built bottom end but, lets try and forget about that right now. I'm trying to limit the boost that my car is producing at the momet to 7 psi. I am running turbosmart 38mm wastegateS. I have the 7 pound springs in place, and I am not running a boost conrtoller at the moment(I was given an HKS SVC4 which i'll recieve sometime next week). My problem is, I have just started driving the car, after the 6 month build,..and I have been playing around a little. Problem is, yesterday, I saw 9psi,..and looked to want to climb. Besides that, boost came on REALLY quick, at low rpm.
Now, is there another way I can regulate boost? I have a twin setup. I know you can rectrict the inlet size of the turbo's with a reducer but,..don't really want to do that. Are my wastegates TOO small? Do I need 44's? Really on a budget right now, so I can't afford to go and just buy new wastegates. A boost controller can only add, or regulate boost right,..not take away?
setups is twin 67's. 38mm turbosmart gates with 7 pound springs. 2 tial 50mm bov's.Fast 90/90, heads/cam 233,237,649,598,112, 2005 stock bottom LS6.
Now, is there another way I can regulate boost? I have a twin setup. I know you can rectrict the inlet size of the turbo's with a reducer but,..don't really want to do that. Are my wastegates TOO small? Do I need 44's? Really on a budget right now, so I can't afford to go and just buy new wastegates. A boost controller can only add, or regulate boost right,..not take away?
setups is twin 67's. 38mm turbosmart gates with 7 pound springs. 2 tial 50mm bov's.Fast 90/90, heads/cam 233,237,649,598,112, 2005 stock bottom LS6.
FWIW, on my single turbo set-up 38mm WG, I could never hold 7 psi when I was on a stock bottom end... I could only hold 9 psi so I left it there until I went to 16 later. 
On a twin set-up, each WG is really trying to hold alot less, a smaller psi level than the total if I'm thinking about it correctly... That's tough... Plus, if you have two 7# springs, doesn't that mean each turbo will produce 7 psi, meaning 14 or more psi?
With a good tune, is the 2 psi that important to you? I see you blowing a piston at 7 psi as you would with 8 or 9, just as unlikely if tuned really conservatively...
Damn, your real problem is if you can't even hold 9 or less with the lowest # spring possible... The boost behaved like it wanted to keep climbing, huh?
On a twin set-up, each WG is really trying to hold alot less, a smaller psi level than the total if I'm thinking about it correctly... That's tough... Plus, if you have two 7# springs, doesn't that mean each turbo will produce 7 psi, meaning 14 or more psi?
With a good tune, is the 2 psi that important to you? I see you blowing a piston at 7 psi as you would with 8 or 9, just as unlikely if tuned really conservatively...
Damn, your real problem is if you can't even hold 9 or less with the lowest # spring possible... The boost behaved like it wanted to keep climbing, huh?
I'd say the easiest way to get around the problem is:
1) Try smaller springs and see if that helps.
2) Run less timing and richer then normal on the 9 psi settings. 7 psi power on 9 psi in the intake.
1) Try smaller springs and see if that helps.
2) Run less timing and richer then normal on the 9 psi settings. 7 psi power on 9 psi in the intake.
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Your wastegate is just not expelling enough of the exhaust gases to maintain the 7psi. While it may not be a huge issue ,the issue with lowering the spring pressure is that the gate opens up earlier and is slowing decreasing spool. Again it may not be a big issue but take that into consideration. Also even if that smaller spring is opening earlier, if the gate is too small it will still overboost.
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FWIW, on my single turbo set-up 38mm WG, I could never hold 7 psi when I was on a stock bottom end... I could only hold 9 psi so I left it there until I went to 16 later.
On a twin set-up, each WG is really trying to hold alot less, a smaller psi level than the total if I'm thinking about it correctly... That's tough... Plus, if you have two 7# springs, doesn't that mean each turbo will produce 7 psi, meaning 14 or more psi?
With a good tune, is the 2 psi that important to you? I see you blowing a piston at 7 psi as you would with 8 or 9, just as unlikely if tuned really conservatively...
Damn, your real problem is if you can't even hold 9 or less with the lowest # spring possible... The boost behaved like it wanted to keep climbing, huh?
On a twin set-up, each WG is really trying to hold alot less, a smaller psi level than the total if I'm thinking about it correctly... That's tough... Plus, if you have two 7# springs, doesn't that mean each turbo will produce 7 psi, meaning 14 or more psi?
With a good tune, is the 2 psi that important to you? I see you blowing a piston at 7 psi as you would with 8 or 9, just as unlikely if tuned really conservatively...
Damn, your real problem is if you can't even hold 9 or less with the lowest # spring possible... The boost behaved like it wanted to keep climbing, huh?
Your wastegate is just not expelling enough of the exhaust gases to maintain the 7psi. While it may not be a huge issue ,the issue with lowering the spring pressure is that the gate opens up earlier and is slowing decreasing spool. Again it may not be a big issue but take that into consideration. Also even if that smaller spring is opening earlier, if the gate is too small it will still overboost.
werd up. I'll try and order these this week, and test and install. If this doesn't work,...i'll have to go bigger gates. I don't have a problem letting it run fat and detuned,..just as long as it'll last a little bit longer.
Thanks everyone for there knowledge.
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Why would you do that? If you want the 7 at the engine, best place to get 7 is at the engine. You reference it off the compressor you'll have whatever boost drop everything has and wont get 7 at the engine.
Is your boost gauge reading from the same spot your wastegates are referenced?
Is your boost gauge reading from the same spot your wastegates are referenced?
Normally referencing from the intake mani is ideal. But the thread starter is having trouble with is system overboosting and by referencing pressure from the comp housing the wastegates will open a bit sooner and will allow for some pressure drop through the I/C, which may help his issue. If it were to fix it then leave it like this until the motor is forged up then switch back to the intake manifold for boost referencing!
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I'm referencing boost off the manifold. Running between the back of the manifold, to the brake booster. I run a nexus gage(digital, pulls signal from it's own map), then I obviously have the bov's, and gates running off of this as well.
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As in the above post this should see a drop in manifold boost due to restiction through IC and intake pipes.
worth a try
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Alright. Can you explain this to me a little bit better please? I understand how to re-route it,..and I understand it'll loose boost through the piping but...I guess I am trying to understand this better.
By doing this, it'll trigger the gates to open @ 7psi,...then, it'll continue to go through the pipes,..still most liley building boost,..when it actually hits the manifiold,...i'll have the same outcome right?
sorry, trying my best. I guess what I am trying to say is, I understand it like this, by referencing the gates at the compressor, it'll trigger them to see the 7 psi QUICKER, therefore opening sooner?... therefore theoretically, lowering the boost that actually hits the manifold....that is,...IF the gates can hold these bastards down?
close?..
Alright. Can you explain this to me a little bit better please? I understand how to re-route it,..and I understand it'll loose boost through the piping but...I guess I am trying to understand this better.
By doing this, it'll trigger the gates to open @ 7psi,...then, it'll continue to go through the pipes,..still most liley building boost,..when it actually hits the manifiold,...i'll have the same outcome right?
sorry, trying my best. I guess what I am trying to say is, I understand it like this, by referencing the gates at the compressor, it'll trigger them to see the 7 psi QUICKER, therefore opening sooner?... therefore theoretically, lowering the boost that actually hits the manifold....that is,...IF the gates can hold these bastards down?
close?..
By doing this, it'll trigger the gates to open @ 7psi,...then, it'll continue to go through the pipes,..still most liley building boost,..when it actually hits the manifiold,...i'll have the same outcome right?
sorry, trying my best. I guess what I am trying to say is, I understand it like this, by referencing the gates at the compressor, it'll trigger them to see the 7 psi QUICKER, therefore opening sooner?... therefore theoretically, lowering the boost that actually hits the manifold....that is,...IF the gates can hold these bastards down?
close?..
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"sorry, trying my best. I guess what I am trying to say is, I understand it like this, by referencing the gates at the compressor, it'll trigger them to see the 7 psi QUICKER, therefore opening sooner?... therefore theoretically, lowering the boost that actually hits the manifold....that is,...IF the gates can hold these bastards down?"
You have it,
the compressor will probably see 2 or 3 psi more then the manifold due to pressure drop through intercooler and pipeing (depending on how efficient it is)
So 9 psi at compressor will only be 6-7 psi at manifold.
The wastegate is also seeing the boost sooner, so should react quicker , reducing boost spikes at the manifold.
Then just use a boost controller to dial in the desired boost
You have it,
the compressor will probably see 2 or 3 psi more then the manifold due to pressure drop through intercooler and pipeing (depending on how efficient it is)
So 9 psi at compressor will only be 6-7 psi at manifold.
The wastegate is also seeing the boost sooner, so should react quicker , reducing boost spikes at the manifold.
Then just use a boost controller to dial in the desired boost
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Ill try to explain...using your car as a example you see 9 psi in the intake. There may be 11-12-13 psi at the outlet of the compressor. So moving the reference of the wastegate to a place in the system with a higher pressure should make it control less boost. The gate should open at a lower boost level and control less.
"sorry, trying my best. I guess what I am trying to say is, I understand it like this, by referencing the gates at the compressor, it'll trigger them to see the 7 psi QUICKER, therefore opening sooner?... therefore theoretically, lowering the boost that actually hits the manifold....that is,...IF the gates can hold these bastards down?"
You have it,
the compressor will probably see 2 or 3 psi more then the manifold due to pressure drop through intercooler and pipeing (depending on how efficient it is)
So 9 psi at compressor will only be 6-7 psi at manifold.
The wastegate is also seeing the boost sooner, so should react quicker , reducing boost spikes at the manifold.
Then just use a boost controller to dial in the desired boost
You have it,
the compressor will probably see 2 or 3 psi more then the manifold due to pressure drop through intercooler and pipeing (depending on how efficient it is)
So 9 psi at compressor will only be 6-7 psi at manifold.
The wastegate is also seeing the boost sooner, so should react quicker , reducing boost spikes at the manifold.
Then just use a boost controller to dial in the desired boost
Awesome. Thanks again. Best spot to do this would probably be the charge pipes correct?....instead of tapping into the housings? So,..man that seems soo simple, just tap two vaccum lines,...and run current gate hoses from the manifold to the new vacum line taps that are now on the charge pipes...
Sounds good to me. Gonna probably look into the waste gate springs as well. Just incase. I don't wanna get to the dyno and have the POSSIBILITY of it overboosting. So,..i'll do as you said,..and just incase i can always change the springs on the dyno.
Cool.
Thanks again guys, I appreciate the knowledge.
