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Discussion Starter · #1 ·
Im hoping to install my OBX catless downpipe on my 05 SR MT and i was wondering how it would work with a stock tune. i heard there can be boost spikes in between shifts on the stock tune but others are saying it will be fine. does anyone have any info on this at all? input is greatly appreciated!
 

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Whats the meaning installing a high flow downpipe without a proper tune for it?
 

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You will be fine. The tune allows your car to take advantage of the less restrictive downpipe and create more power by creating more boost. Running a stock tune will not hurt anything but your not getting the most out of your upgrade without a tune that takes advantage of it. Bottom line, it will sound really good and you will get a little more power out of your car but not as much as your car with a tune.
 

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Discussion Starter · #4 ·
im eventually going to get a tune but i have the OBX DP in my garage and i want to put it on asap but wanted to make sure there were going to be any issues on a stock tune, like boost spikes
 

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With a catless down pipe you will get a CEL, so a spacer is needed to eliminate that. But I have been running a Phuz DP for at least 2,000 miles without any problems. If you want the most out of the pipe a tune will help some.
 

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Discussion Starter · #6 ·
i have a couple spacers already so the CEL hopefully wont be an issue. i have been hearing that with manual R's that between shifts on a stock tune there have been boost spikes up to about 25 psi. does yours spike between shifts at all?
 

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You'll only need one on the rear o2 sensor. I don't get how you can get a boost spike in between shifts when you let off the gas. I don't have a boost gauge, but have never gotten spikes before.
 

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Discussion Starter · #9 ·
Sorry I wasn't too clear on what I meant I realize that now. I meant after you shift when you step on the gas again people have gotten boost spikes
 

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Mine should be delivered Monday; I plan to get a tune but who knows when. No rule that says you have to do everything at once...
 

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It doesn't hurt but you car will be running rich.
 

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It doesn't hurt but you car will be running rich.
What is this statement based on? Do you have a wideband gauge installed? When you say "running rich", under what conditions are you indicating that this rich condition will occur? At idle? Part throttle? High throttle? Open loop vs. closed loop?
 

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What is this statement based on? Do you have a wideband gauge installed? When you say "running rich", under what conditions are you indicating that this rich condition will occur? At idle? Part throttle? High throttle? Open loop vs. closed loop?
Bla bla bla?
 

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You'll only need one on the rear o2 sensor. I don't get how you can get a boost spike in between shifts when you let off the gas. I don't have a boost gauge, but have never gotten spikes before.
You won't feel a boost spike. I have a boost gauge installed and the spikes do exist but I cannot feel them.
 

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Whats the meaning installing a high flow downpipe without a proper tune for it?
I still noticed gains before tuning. It's not the same kind of gain but it is there definitely. Nothing wrong with making your caR exhaust easier too.
 

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Discussion Starter · #17 ·
its not a matter of me feeling the boost spikes as much as the boost spikes damaging my motor. im pretty sure our stock motors cant handle 25 psi. i could be wrong but id rather be safe than sorry. i dont want to be left with an R paperweight
 

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You will be fine
I ran a DP with a stock tune all winter way back when, it ran GREAT
You still enjoy a few extra HP, better throttle response and quicker turbo spool up
No spikes, nothing there is different
 

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its not a matter of me feeling the boost spikes as much as the boost spikes damaging my motor. im pretty sure our stock motors cant handle 25 psi. i could be wrong but id rather be safe than sorry. i dont want to be left with an R paperweight
Your motor is not seeing the boost spike, only your turbocharger is. When the throttle body closes, the built up pressure in the intake needs somewhere to go. The CBV relieves the pressure because pressure surges will shorten a turbos life. The more drastic boost spikes, the harder it is on turbo life, not motor life.

From what I was told from IPD is the large boost spikes will only occur if you have your car tuned to stage 2 THEN add a dp later. If you do the dp THEN the tune, they can try and reduce large spikes. This happens because of the higher boost pressures. I do not believe the stock CBV was made to handle much more than stock boost. In other words, it just cannot evacuate the 20 pounds of boost quickly enough, causing a larger than stock boost spike. This is why they make aftermarket CBVs and also why they come with different compression springs based off of your boost levels. IPD also said the boost spikes are more pronounced on GT cars because the ECU keeps the boost spooled for a smooth transition into the next gear (or something like that).
 
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