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Old 01-22-2007, 07:48 PM
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Question 3.5 downpipe?

hey yall. right now im running a straight 5inch mbrp exhaust with a 4inch dp, not much done to the truck just mbrp exhaust and a AFE stage 2 w/ pro gaurd. I see that everyone runs on a 3.5dp. So I was wondering if I should switch to a 3.5dp and run a 4inch exhaust. I heard 5inch exhausts are made for trucks that make 450 to 500hp to the wheel. Would a 3.5dp make a difference on my truck?
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Old 01-22-2007, 07:53 PM
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I believe the main reason most people run the 3.5" downpipe is because it can be mounted without modding the firewall to make it fit. If you already have this, I don't see any reason to worry about goiing smaller.
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Old 01-22-2007, 07:57 PM
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I think you will find that the people running on the 3.5 are doing so for lack of room/ease of instalation, you are probably better off with the 4''. The more flow, the better it breaths. the lower the EGTs. Hope that helps.

Gord.
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Old 01-22-2007, 07:57 PM
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So OK Guys, are you saying that on my 2006 KR CC 4x4 I would have to modifiy the firewall to run a 4" MBRP downpipe off my turbo????

I ain't gonna dooo dat!!!! :rain:

I thought this was a simply bolt on the back of the turbo, now you guys are scaring me!!!!! No way do I want to order a 4" turbo back if I have to MOD the firewall....

SHOCK, HORROR, Tell me more!!!
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Old 01-22-2007, 07:58 PM
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And by the way----WELCOME TO POWERSTROKE>ORG.---good to have you here.
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Old 01-22-2007, 08:03 PM
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Quote:
Originally Posted by Lone Ranger View Post
So OK Guys, are you saying that on my 2006 KR CC 4x4 I would have to modifiy the firewall to run a 4" MBRP downpipe off my turbo????

I ain't gonna dooo dat!!!! :rain:

I thought this was a simply bolt on the back of the turbo, now you guys are scaring me!!!!! No way do I want to order a 4" turbo back if I have to MOD the firewall....

SHOCK, HORROR, Tell me more!!!
It's ok, take a valium--And a big hammer--chainsaw-- a little dynomite, and letter rip buddy. hahaha, it's a minnor mod, just to make enough room to get it in there, not a big deal at all. you may not even need it on one that new, i'm not sure.

---Gord.
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Old 01-22-2007, 08:04 PM
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Preference - stay with what you have - you're fine.
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Old 01-22-2007, 08:05 PM
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Quote:
Originally Posted by Lone Ranger View Post
So OK Guys, are you saying that on my 2006 KR CC 4x4 I would have to modifiy the firewall to run a 4" MBRP downpipe off my turbo????

I ain't gonna dooo dat!!!! :rain:

I thought this was a simply bolt on the back of the turbo, now you guys are scaring me!!!!! No way do I want to order a 4" turbo back if I have to MOD the firewall....

SHOCK, HORROR, Tell me more!!!

I didn't have to do ANYthing to fit the 4" dp on my truck. Of course the 6.0 is different. However - I do have a slight vibration at certain RPMS that was spawned from a small point of contact between the firewall and DP.
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Old 01-22-2007, 08:17 PM
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Check out this video for installing a true 4" downpipe. It's fairly easy if done correctly. Hope this helps you understand and maybe make a more informed decision.
http://www.hogperformance.com/upload...ng%20Video.WMV
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Old 01-22-2007, 09:14 PM
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OK Outcast, before I go to the BIG TROUBLE (shipping to Oz) of going a 4" Turbo back, I will do some looking from under the truck... That looked messy because I don't have a Porta Power, but maybe I can figure something else out.. Thank you for that FANTASTIC VIDEO!!!

"Maintain" ....You said "stay with what you have" .... You were talking to the original Posting that had the 4" to 5" .... Right? You were not telling me to stay with stock down pipe were you???? I am looking for power, fuel economy, and cooler EGT and thought this was worth doing.... I would sure love to hear from someone that thought otherwise, would save me a lot of trouble.... Ha!

Cheers from the happiest Ford Owner in the World here in Oz... Brightest Moment of my day (when I am not on a horse), is driving my 350 KR...!!

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