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back pressure


softy
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  • 1 month later...

somebody else should confirm this, but i have read 1-2psi of boost pressure for long tubes alone. so maybe 3+ psi with all those mods?

 

Yeah, that's probably a good guess. I'd guess right about the same. Based purely on what others have seen.

 

 

Phill

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I'm looking at possibly doing the same thing, LTs, no cats, and 3" cat backs but doesn't seem feasible unless going with a supercharger upgrade to compensate for the loss of boost.

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  • 3 weeks later...

just to be clear, my understanding is that even though there is a "loss" of boost pressure, you are increasing flow. so you are going to gain power...even with less boost due to efficiency.

 

 

You're not really losing boost, per se. You're losing the restriction in the exhaust (downstream) that backs up all the way into your intake manifold. Your boost gauge is measuring MANIFOLD pressure so by getting rid of the restriction downstream, you are allowing the pressure to flow through the engine with *less* restriction, eliminating some of the pressure in the intake MANIFOLD but still filling the cylinder with N amount of air/fuel.

 

Make sense?

 

I'm sure someone can explain it better than I can. It's one of those "I know WHY but I can't describe it" type of things.

 

 

Phill

Edited by 2010KonaBlueGT
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You're not really losing boost, per se. You're losing the restriction in the exhaust (downstream) that backs up all the way into your intake manifold. Your boost gauge is measuring MANIFOLD pressure so by getting rid of the restriction downstream, you are allowing the pressure to flow through the engine with *less* restriction, eliminating some of the pressure in the intake MANIFOLD but still filling the cylinder with N amount of air/fuel.

 

Make sense?

 

I'm sure someone can explain it better than I can. It's one of those "I know WHY but I can't describe it" type of things.

 

 

Phill

 

 

This is how I understand it.

 

Remove the restriction on the exhaust and your boost drops. Say you have 18psi max boost. That 3 psi drop will drop you down to 15psi at the same rpm as you previously had 18psi. So, you would have 3 extra psi of boost. Would be the same as if you increased from 18psi to 21psi.

 

At least I thnk that's right ;)

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  • 11 months later...

I'm new here but wanted to put in my 2 cent. I have a 2011 GT500 with zero mods until a month ago and I had Roush/Yates add Kooks 1/7/8 LTs with High flow cats and a Kooks Xpipe. I like the sound but wish I would've just got the Xpipe and a Axle back. Mainly due to the dang Check Engine light that came on the next day.

 

I really should've done more research on the LTs but it's a little late now. I had now idea I'd lose boost. I'd say vie lost atleast 2 psi maybe 3. It doesn't really feel like I lost alot but it defiantly didn't gain that I can tell. From what I can tell maybe once I go for it and lose the warranty I can do a tune and pulley swap plus a CAI and get the car how I want it. Right now I'm pissed I had it sheduled to get my Stripes installed Thursday and I come out of the gas station and I see for the first time that someone had backed into my bumper on the passenger front. I'm ticked now I gotta get the bumper painted before the stripes. I just hope I can find someone to match the 3 yr old Kona blue. Good thing it has been garage kept since day one.

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I'm ticked now I gotta get the bumper painted before the stripes. I just hope I can find someone to match the 3 yr old Kona blue. Good thing it has been garage kept since day one.

 

 

Let me know how that goes. I have the same issue on my right rear corner. I've been real hesitant to get it fixed due to the closure of the factory in Japan where they made the prismatic METALFLAKE for the Kona Blue paint. You can still get Kona Blue, but it may or may not have the multi-color (prismatic) metalflake in it.

 

I was told the KB w/Metalflake is still available in small quantities (pints, quarts, etc.) but I don't know how to tell if it has the Metalflake in it, BEFORE it gets put on my car.

 

 

Phill

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I'll defiantly ask about the paint tommorow when I stop by the body shop that I plan to use for the install of my SHR flush 1/4 window louvers. When I stopped two weeks ago he said he could match it. But Idk bout the plant closing. Dang now I'm gonna be sweating till I know. I'm ticked I've took so good care with this car. Heck I just started driving it again. I had parked it for almost a year. Opps sry for the ramble

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I'll defiantly ask about the paint tommorow when I stop by the body shop that I plan to use for the install of my SHR flush 1/4 window louvers. When I stopped two weeks ago he said he could match it. But Idk bout the plant closing. Dang now I'm gonna be sweating till I know. I'm ticked I've took so good care with this car. Heck I just started driving it again. I had parked it for almost a year. Opps sry for the ramble

 

 

I had my Shelby quarter window scoops painted by a friend who works in a automotive paint store by day and has a body shop in his garage that he does side work out of. He bought the paint (Paint Code or Kona Blue is L6) and it matched perfectly. BUT, that was *just* before the Tsunami hit Japan and wiped out the fleck factory so mine had the metal flake.

 

I double checked with the Ford dealer to find out if there is a Kona Blue Metalic AND a Kona Blue (plain). I was told, there IS and that I had to be careful in the future if I needed paint matching on my car.

 

And it's not just plain silver flakes. The flakes in the factory Kona Blue change color as the angle changes. It's VERY obvious on a clean car on a sunny day.

 

 

Phill

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Well looks like I'm gonna go for it. The body shop seemed very confident that you won't be able to notice when he's done. He's charging me 500 to paint the front bumper cover. I'll let u know how it turns out. I'm taking her to him monday.

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Well looks like I'm gonna go for it. The body shop seemed very confident that you won't be able to notice when he's done. He's charging me 500 to paint the front bumper cover. I'll let u know how it turns out. I'm taking her to him monday.

Cool, thanks. Real interested to see if the paint matches. Take it out into the SUNLIGHT. That's where I really notice the 'multi' color flakes. In the garage, they all look silver. In the sun, they change color as you change angle. From red to green to blue.

 

 

Phill

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Well looks like I'm gonna go for it. The body shop seemed very confident that you won't be able to notice when he's done. He's charging me 500 to paint the front bumper cover. I'll let u know how it turns out. I'm taking her to him monday.

if you can do a scratch repair on the bumper it will save you a lot of headaches in the future. Very few repaints hold up like the baked factory finish especially on the front bumper.

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  • 2 weeks later...

The flake you guys are referring to is called Xirralac (think thats the right spelling). I also have the Kona Blue GT500 and have had the underside of my hood painted. Make sure that the person painting it gets the right stuff. Most paint shops can match the L6 code but its the metal flake thats going to make it look different. If they dont use the Xirralac you will notice the difference. I checked on it a couple of months ago and according to info on the web there is a factory that was just built or being built in Germany that can make the Xirralac. Sorry for the spelling but you get the idea.

999987_10151746488538024_718854145_n.jpg

999987_10151746488538024_718854145_n.jpg

Edited by Firekiller
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The flake you guys are referring to is called Xirralac (think thats the right spelling). I also have the Kona Blue GT500 and have had the underside of my hood painted. Make sure that the person painting it gets the right stuff. Most paint shops can match the L6 code but its the metal flake thats going to make it look different. If they dont use the Xirralac you will notice the difference. I checked on it a couple of months ago and according to info on the web there is a factory that was just built or being built in Germany that can make the Xirralac. Sorry for the spelling but you get the idea.

 

Yes, this is my understanding too.

 

You can get L6 Kona Blue and you can get L6 Kona Blue METALIC, but it's not the "prismatic" flake that changes color with angle.

 

Which is also my worry, if/when I have my rear facia/bumper repaired.

 

I figure that longer I wait, the better my chance of getting the right stuff.

 

 

Phill

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