 DSM Boost Creep? |
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 Sep 15 2004, 06:14 AM
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#1
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 Person of Wisdom  Group: Members Posts: 190 Joined: 8-November 03 From: Washington DC Member No.: 197  |
Do DSMs get boost creep after opening up the exhaust? I know it's a constant issue with rotaries. How do you guys control it if it happens?
-------------------- Somebody make the pain stop. They won't let me go.
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Sep 15 2004, 06:56 AM
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#2
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DSMCentral Godfather Group: Admin Posts: 3,823 Joined: 10-January 01 From: Washburn Member No.: 26 |
Boost creap is a comon issue with DSM's. The only way to control it is to improve/open-up the waste gate and possibly use an external dump for the WG.
-------------------- In Loving memory of David T Crebo
Greatness comes from the most unexpected places!  |
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Sep 15 2004, 09:19 AM
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#3
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Person of Wisdom Group: Members Posts: 190 Joined: 8-November 03 From: Washington DC Member No.: 197 |
Any of you just try electronic control, like a boost controller? I'm considering doing that with my 7 to prevent the creep and spike.
-------------------- Somebody make the pain stop. They won't let me go.
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Sep 15 2004, 02:37 PM
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#4
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 Zen Master DSM Group: Moderators Posts: 3,008 Joined: 10-January 01 From: in front of you Member No.: 5 |
The ebc should help with boost spikes, but like Kicks said boost creep is usually an issue with exhaust flow out of the wastegate. By opening up your exhaust you are increasing the pressure differential across the turbine. This makes the exhaust want to flow across the turbine rather than through the wastegate when its open. I agree with Kick's recommendations.
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Sep 15 2004, 02:43 PM
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#5
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 Post Master Group: Members Posts: 626 Joined: 25-September 02 From: Urbana, IL Member No.: 19 |
An electronic boost controller helped some with boost creep on my buddy's 93 FD.
-------------------- Eric Wort
87 White Buick Turbo 'T' (11.71 @ 116.5, 1.61 60ft, slipping trans) 92 Teal Eagle Talon TSi AWD (burn victim) |
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Sep 15 2004, 03:14 PM
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#6
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 Post Master Group: Members Posts: 972 Joined: 30-October 02 Member No.: 34 |
EBC shouldn't matter if you are running a high quality manual boost controller. Once the wastegate is open, it's open.
The EBC's ability to control or bleed off signal to the wastegate isn't going to allow it to open any more fully or flow/bypass any more exhaust gasses. The problem isn't too much exaust flow or any issues from the 3" exhaust, it's a lack of flow out the wastegate (as stated earlier). Basicly your exhaust system is more effecient than your wastegate exhaust at this point. You'll need to upgrade/open up the wastegate exhaust path to compensate for the increased flow. -------------------- |
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Sep 15 2004, 03:38 PM
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#7
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Post Master Group: Members Posts: 626 Joined: 25-September 02 From: Urbana, IL Member No.: 19 |
MBC's (including the stock boost control) don't work all that well on the RX-7 TT when its still running in stock sequential mode. There's more than one wastegate to control in the system, so you can either hook the MBC to both of the wastegates and lose the entire sequential system, or you end up with a problem where the turbo with the MBC on it spikes. If the system spikes over stock boost at all, it runs into a leaner part of the fuel map, leading to higher EGTs, which is what typically contributes to the creep at high RPM. A really really good electronic controller will prevent this spike from happening in the first place.
Porting out the wastegate flappers wouldn't be a bad idea either though, I'm just saying the system is a lot more complicated than you guys are assuming. -------------------- Eric Wort
87 White Buick Turbo 'T' (11.71 @ 116.5, 1.61 60ft, slipping trans) 92 Teal Eagle Talon TSi AWD (burn victim) |
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Sep 15 2004, 03:58 PM
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#8
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 Post Master Group: Members Posts: 774 Joined: 28-October 02 From: Pekin Member No.: 32 |
Solved all my creep problems by porting the o2 housing. Easy, cheap, effective.
-------------------- 2009 Scion Tc
1994 Del Sol Si 1991 Talon TSi AWD 1990 Mustang GT FOR SALE!!! |
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Sep 15 2004, 04:19 PM
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#9
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Post Master Group: Members Posts: 972 Joined: 30-October 02 Member No.: 34 |
QUOTE (wortdog @ Sep 15 2004, 09:38 PM) MBC's (including the stock boost control) don't work all that well on the RX-7 TT when its still running in stock sequential mode. Porting out the wastegate flappers wouldn't be a bad idea either though, I'm just saying the system is a lot more complicated than you guys are assuming. I stand corrected on the MBC issue there. But, I still think a proper wastegate flow will help solve the issue. -------------------- |
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Sep 16 2004, 05:42 AM
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#10
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Person of Wisdom Group: Members Posts: 190 Joined: 8-November 03 From: Washington DC Member No.: 197 |
Whoa! Hey, just asking how DSMs do it and what your problems are. Thanks for all the replies, though.
-------------------- Somebody make the pain stop. They won't let me go.
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Sep 16 2004, 09:25 AM
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#11
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Person of Wisdom Group: Members Posts: 190 Joined: 8-November 03 From: Washington DC Member No.: 197 |
Is an external waste gate another workable solution for DSMs? Or is it pretty worthless? I don't know about you guys, but pulling the snails out just to port a wastegate is a pita.
-------------------- Somebody make the pain stop. They won't let me go.
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Sep 16 2004, 09:27 AM
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#12
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Person of Wisdom Group: Members Posts: 190 Joined: 8-November 03 From: Washington DC Member No.: 197 |
QUOTE (wortdog @ Sep 15 2004, 02:43 PM) An electronic boost controller helped some with boost creep on my buddy's 93 FD. What was your bud running? -------------------- Somebody make the pain stop. They won't let me go.
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Sep 16 2004, 09:34 AM
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#13
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 Post Master Group: Members Posts: 658 Joined: 7-October 03 From: Pekin Member No.: 181 |
yes. external wastegate is also a way to solve it. due to the fact it is seeing the same amount of air flow as the turbo itself is seeing.
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