How Does Boost Creep Occur?
08-01-02, 04:13 PM
#51
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Originally posted by NZConvertible
Boost creep and boost spikes are two quite different things. Boost creep is just as has been described, boost jumps up to the right level but when the wastegate’s capacity is reached it starts to rise again. A boost spike is when the wastegate can’t react fast enough to a sudden increase in airflow and boost overshoots the set point and then comes down as the wastegate catches up. This isn’t necessarily a bad thing, as it usually happens at lower revs so the fuel system can cope with higher boost because the airflow is much less. So you get a nice mid-range torque spike!
Boost creep and boost spikes are two quite different things. Boost creep is just as has been described, boost jumps up to the right level but when the wastegate’s capacity is reached it starts to rise again. A boost spike is when the wastegate can’t react fast enough to a sudden increase in airflow and boost overshoots the set point and then comes down as the wastegate catches up. This isn’t necessarily a bad thing, as it usually happens at lower revs so the fuel system can cope with higher boost because the airflow is much less. So you get a nice mid-range torque spike!
08-01-02, 04:15 PM
#52
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I sure hope this gets archived. This is a great thread. Ok, how about the actual flapper. Anything you can do to it to aid is exhaust bleed off?
08-01-02, 04:15 PM
#53
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Originally posted by rico05
How exactly does a boost controller work?
How exactly does a boost controller work?
Bleeder Boost Control
Pressure Regulator Boost Control (Part 1)
Pressure Regulator Boost Control (Part 2)
Read both, then take your pick; I think the second method is much better.
08-01-02, 04:18 PM
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Alright everyone, repeat after me: [b]a boost controller cannot lower boost nor control boost creep. That is function of the PHYSICAL WASTEGATE. The ONLY way to control boost creep is to modify/replace the wastegate, or push less air through the turbo.
Aaron,
I was already planning to let the wastegate lower the boost after I remove the electronic controller AND port the wastegate, by controlling boost i ment RAISING it
. I got this lecture about a year ago, it took me awhile before I understood how it all works.
Jameson
Aaron,
I was already planning to let the wastegate lower the boost after I remove the electronic controller AND port the wastegate, by controlling boost i ment RAISING it
. I got this lecture about a year ago, it took me awhile before I understood how it all works.Jameson
08-01-02, 04:19 PM
#56
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Got ya. Just wasn't sure if you could shave off some weight on the back side or something along those lines to help it be lighter and therefore flap quicker. Thaks Jason, but would a electric boost controller be better or would that DIY be a better idea?
08-01-02, 04:20 PM
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those autospeed articles are what I am modeling my boost controller after, already ordered the parts :P
Rico, I like the manual boost controller, because it's simple, boost comes on EXTREMELY quick when you delay the pressure going to the wastegate, and it's also cheap.
Jameson
Rico, I like the manual boost controller, because it's simple, boost comes on EXTREMELY quick when you delay the pressure going to the wastegate, and it's also cheap
.Jameson
Last edited by Supermac 7; 08-01-02 at 04:22 PM.
08-01-02, 04:23 PM
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Lightening the WG flap may compromise structural integrity...I wonder if anyone has tried it.
Electronic boost controllers are a little more reliable, because atmospheric conditions and temps affect manual BCs, which the electronic ones can compensate for. (well, hopefully, anyway.)
Electronic boost controllers are a little more reliable, because atmospheric conditions and temps affect manual BCs, which the electronic ones can compensate for. (well, hopefully, anyway.)
08-01-02, 04:25 PM
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Originally posted by Supermac 7
if you port beyond the flapper door, boost will not come on near as hard, will it, because of the added wastegate creep?
if you port beyond the flapper door, boost will not come on near as hard, will it, because of the added wastegate creep?
All turbos suffer from wastegate creep, even brand new ones. This is when the pressure in the wastegate actuator starts to open the wastegate before max boost is reached, which slows rate of boost climb. Porting past the size of the flapper will make this even worse. EBC’s eliminate wastegate creep by bleeding all pressure out of the wastegate line until set point is reached, keeping the flap closed until the very last moment. The pressure regulator boost controller I posted above does the same thing with an inline pressure relief valve.
08-01-02, 04:29 PM
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One of the nice things about an external wastegate (when you go to a different turbo setup, of course) is that air is pressed on the valve in the wastegate from both sides until the boost pressure overcomes the other side, and the wastegate pops open. Therefore you get very little wastegate creep, if any.
For the time being, im gonna go port my stock one...
Jameson
For the time being, im gonna go port my stock one...
Jameson
08-01-02, 04:30 PM
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Originally posted by rico05
Thaks Jason, but would a electric boost controller be better or would that DIY be a better idea?
Thaks Jason, but would a electric boost controller be better or would that DIY be a better idea?
Damn this thread's moving fast; can't keep up!
08-01-02, 04:32 PM
#62
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Well, I kinda made some goofs w/ my N/A, and I want to do the next one correctly. If spending $300 instead of $10 means more reliability and safer performance, it is money well spent.
08-01-02, 04:36 PM
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I think I am going to build a boost controller this weekend...thanks for the links.
My boss' boss' boss just caught me surfing the forum...lol. He's a pretty cool guy, so I'm not in trouble.
My boss' boss' boss just caught me surfing the forum...lol. He's a pretty cool guy, so I'm not in trouble.
08-01-02, 04:59 PM
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what would happen if you ditched the wastegate all together (or just the flapper door or whatever) and slaped a boost controler on there at say like 7PSI and when it hit that it would bleed all the boost through the.. um... i guess the hole left there, i dont think it could ever spike because there would be nothing there to be "too slow" and the boost controler would let it boost up...... maybe.... **** if i know. Accually, doesnt a waste gate have to be there in order for it to boost at all?.. man.. i need to lay off the late nights for a while, clouding my brain
08-01-02, 05:04 PM
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wow, i think that last post was the most idiotic post i have ever made, of course the wastegate has to be there, sorry, ill leave it for preference or something.
08-01-02, 05:08 PM
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Roy,
YOU CAN NOT BOOST WITHOUT A WASTEGATE, it lets all the air that the engine makes out the hole instead of it going around the turbine if there is no wastegate there. it's the same as being N/A.
Nonameo,
The series 4 wastegate is bad with only 2psi or so above stock levels, it will begin to creep.
Series 5 is a little better stock, because it has two passages instead of one.
Porting should be able to take ALMOST anything you can throw at it, depending on the size of the port job.
Jameson
YOU CAN NOT BOOST WITHOUT A WASTEGATE, it lets all the air that the engine makes out the hole instead of it going around the turbine if there is no wastegate there. it's the same as being N/A.
Nonameo,
The series 4 wastegate is bad with only 2psi or so above stock levels, it will begin to creep.
Series 5 is a little better stock, because it has two passages instead of one.
Porting should be able to take ALMOST anything you can throw at it, depending on the size of the port job.
Jameson
08-01-02, 05:47 PM
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Supermac7, thanks for the info, i do know this, just not thinking clear, for some reason i was thinking that the boost controler would hold the boost in, but.. thats just idiotic. no need for yelling reguardless how ignorant the question/idea is
08-01-02, 05:52 PM
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Originally posted by UniqueTII
So you're saying that creep is because it doesn't flow enough when wide open, and spikes are because it doesn't open fast enough? Makes sense. Geez, I've owned my TII for almost 4 years and I'm finally learning all this turbo stuff. Many thanks to you guys.
So you're saying that creep is because it doesn't flow enough when wide open, and spikes are because it doesn't open fast enough? Makes sense. Geez, I've owned my TII for almost 4 years and I'm finally learning all this turbo stuff. Many thanks to you guys.
I've been driving RX-7's for 14 years, and I still learn stuff at least weekly.
Originally posted by Supermac 7
YOU CAN NOT BOOST WITHOUT A WASTEGATE, it lets all the air that the engine makes out the hole instead of it going around the turbine if there is no wastegate there. it's the same as being N/A.
YOU CAN NOT BOOST WITHOUT A WASTEGATE, it lets all the air that the engine makes out the hole instead of it going around the turbine if there is no wastegate there. it's the same as being N/A.
The wastegate allows the boost to bleed off. Were the wastegate not there, the boost would rise until the turbo finally reaches equilibrium or until something breaks. In the case of a TII, something would break first. Other engine/turbo combinations can actually operate without a wastegate at lower boost levels if the turbo is properly matched to the engine.
08-01-02, 08:29 PM
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Lots of good info. Thanks. I've seen the porting pictures on RETed's site and was wondering if anyone whose done this mod could give an idea of just how much bigger we are talking about? I just can't tell from the size of the pictures.
08-01-02, 09:43 PM
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Originally posted by Evil Aviator
Right idea, but 180deg off. The wastegate allows the boost to bleed off. Were the wastegate not there, the boost would rise until the turbo finally reaches equilibrium or until something breaks. In the case of a TII, something would break first. Other engine/turbo combinations can actually operate without a wastegate at lower boost levels if the turbo is properly matched to the engine.
Right idea, but 180deg off.
The wastegate allows the boost to bleed off. Were the wastegate not there, the boost would rise until the turbo finally reaches equilibrium or until something breaks. In the case of a TII, something would break first. Other engine/turbo combinations can actually operate without a wastegate at lower boost levels if the turbo is properly matched to the engine.
Oh, and Roy, I apologize for yelling, didnt mean to come across as an ***.Thanks,
Jameson
08-01-02, 10:02 PM
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Originally posted by Supermac 7
Evil, my bad, I mis stated myself. I was saying that if there were no wastegate there, just a big hole (similar to removing the flapper door on the stock turbo), than the turbine blades would never spin fast enough to produce boost because they are being bypassed. I DO understand that if it were solid, i.e., no hole, than the turbo would keep spinning and spinning, and like you described, something would break. I am really not as dumb as I appear Oh, and Roy, I apologize for yelling, didnt mean to come across as an ***.
Thanks,
Jameson
Evil, my bad, I mis stated myself. I was saying that if there were no wastegate there, just a big hole (similar to removing the flapper door on the stock turbo), than the turbine blades would never spin fast enough to produce boost because they are being bypassed. I DO understand that if it were solid, i.e., no hole, than the turbo would keep spinning and spinning, and like you described, something would break. I am really not as dumb as I appear
Oh, and Roy, I apologize for yelling, didnt mean to come across as an ***.Thanks,
Jameson
08-01-02, 10:08 PM
#73
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Originally posted by Supermac 7
I was saying that if there were no wastegate there, just a big hole (similar to removing the flapper door on the stock turbo), than the turbine blades would never spin fast enough to produce boost because they are being bypassed.
I was saying that if there were no wastegate there, just a big hole (similar to removing the flapper door on the stock turbo), than the turbine blades would never spin fast enough to produce boost because they are being bypassed.
08-01-02, 10:18 PM
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eh, yeah, i remember, here we go again...
I realize that boost creep occurs when too much air is going through the engine and out the exhaust for the wastegate to handle, but I was more or less referring to either a ported wastegate "hole" (no flapper), or stock exhaust flow levels.
Jameson
I realize that boost creep occurs when too much air is going through the engine and out the exhaust for the wastegate to handle, but I was more or less referring to either a ported wastegate "hole" (no flapper), or stock exhaust flow levels.
Jameson