I just installed a cat delete & diamond eye down pipe last week & have lost a huge amount of bottom end power. Mid & top end aren't too bad. I towed my 5th wheel hauler to glamis last weekend and it towed pretty good. My EGT's never went about 1200. I removed my Edge today and that didn't seem to make a difference. I'm also not getting any smoke at all, no matter how I drive or what level the Edge was set. Any ideas? I could usually light up the tires anytime & now I can probably run faster then the truck from a dead stop. Within the last 500 miles I installed a trans go jr & changed all the oils & filters. Also recently installed the blocker plate & finger stick.
Not sure what to do.....

I just installed a cat delete & diamond eye down pipe last week & have lost a huge amount of bottom end power. Mid & top end aren't too bad. I towed my 5th wheel hauler to glamis last weekend and it towed pretty good. My EGT's never went about 1200. I removed my Edge today and that didn't seem to make a difference. I'm also not getting any smoke at all, no matter how I drive or what level the Edge was set. Any ideas? I could usually light up the tires anytime & now I can probably run faster then the truck from a dead stop. Within the last 500 miles I installed a trans go jr & changed all the oils & filters. Also recently installed the blocker plate & finger stick.
Not sure what to do.....

Do you have a check engine light on? Sounds to me like you have an Overboost code. IF so, erase it and drive it.

he's running 22-24psi on stock turbo.

i also noticed a lot less smoke after installing my downpipe...unsure about power loss, if i did lose any it was insignificant

may check your connections on boost stick and turbo, check your boost levels, I;m sure someone will chime in with a ideal of the loss of of power there some low end lose but it sound like something is not right good luck

Maybe if the diamond eye down pipe is a bigger diameter you are loosing back pressure and it takes more time for the turbo to spool. I would venture to say a larger down pipe would only make a little more hp up top and would only be necessary or worth while if running a bigger after market turbo. JMO

I have the diamond eye down pipe and a 5" down pipe back exhaust, I didn't lose any power down low and the turbo does spool faster. I didn't get any power gains at the track, but I don't rev mine high enough to see the gains from the diamond eye pipe IIRC you need to be 4k plus rpms to see power gains.

The loss of back pressure in the exhaust will only help the truck flow better and give you power gains, not losses. the turbine itself being in the exhaust path creates all the back pressure the motor could ever need.

True as Pat tested Wendy on the dyno and only seen gains above 3000 rpms over the stock down pipe. There should be no loss from loss of back pressure like DrHolliday stated.

I would say there is something wrong with the fingerstick. We had a truck that did this and it turned out to be the programer was blocking for the egr blocker plate but we also had the fingerstick installed. Turns out cant run both at the same time. Pulled fingerstick out truck ran great. JMO

I have the Edge which doesn't block any codes. I removed it completely & will remove the finger stick this weekend to see if that helps. I also don't get ANY smoke at all now. No matter how I drive or what setting the Edge has.
I'm going to disconnect the batteries to make sure there's no simple electrical problem and also check the downpipe install to ensure there are no leaks.

You don't need back pressure after the turbo... the easier it is for the exhaust to come out the better = BIG PIPE!!!

It is something other than the pipe. A turbo gives you more backpressure than you can imagine, and the best thing you can do for it is let that thing breathe post-turbine.

So you guys don't really see any gains at all from ditching the cat? I was planning on changing mine out, just holding out because i'm concerned about the noise. If it's not even going to help mileage or power then forget it.

Sounds to me like a fuel filter problem, rather than the exhaust I would try that and see if it helps. It could be a coincidence that it plugged at the same time as the exhaust??? It couldn't hurt and if you do change it tell us if it helps.

True as Pat tested Wendy on the dyno and only seen gains above 3000 rpms over the stock down pipe. There should be no loss from loss of back pressure like DrHolliday stated.

X2

I Dont Think He Is Runnin 22-24 Psi If He Has A Boost Stick And Edge. That Might Be Waht The Edge Is Saying But The Boost Stick Modifys The Signal So It Thinks It Isnt Makeing Boost And There Fore It Produces More. Need A Guage To Know. I Felt Like When I Had Bully Dog On My Truck And Installed The Boost Stick That It Lost Power. I Would Remove The Boost Stick And Check For Codes Then Drive Again

I Dont Think He Is Runnin 22-24 Psi If He Has A Boost Stick And Edge. That Might Be Waht The Edge Is Saying But The Boost Stick Modifys The Signal So It Thinks It Isnt Makeing Boost And There Fore It Produces More. Need A Guage To Know. I Felt Like When I Had Bully Dog On My Truck And Installed The Boost Stick That It Lost Power. I Would Remove The Boost Stick And Check For Codes Then Drive Again

22-24 psi stock.

It Is Hard To Read Posts When The First Letter Of Every Word Is in Caps :D

I noticed a huge drop in EGT's after the cat delete & downpipe. Wasn't much louder at all. I was hitting 1400 while towing and it dropped to 1150ish. Though the bottom end is not there anymore. I replaced the fuel filter last month but I will try that again. I removed the edge & boost stick and that didn't help

I didn't Lose any of my Low End when I put the Pipe on. Somethings gotta be Loose or Leaking somewhere, or a Clogged Fuel Filter.

what could be loose? I checked the connections on the turbo/downpipe/exhaust and they look good.

what could be loose? I checked the connections on the turbo/downpipe/exhaust and they look good.

Anything after the turbo can only hurt power. If it were leaking it wouldn't do a darn thing but be irritating.

Honestly from a performance perspective the best thing you can do for a turbo is stick the biggest pipe possible on it, and dump it 24" or so from the turbine.

what could be loose? I checked the connections on the turbo/downpipe/exhaust and they look good.

Just Check everything. Check the Clamps for the Boost Tubes, make sure the Intake is nice and Tight, Exhaust is Lined Up and Clamps are Tight.

what could be loose? I checked the connections on the turbo/downpipe/exhaust and they look good.

When I had the Edge J/A it seemed to go through fuel filters faster then normal, it would run great on a fresh filter then 3-4000 miles later it lose some of the high end. After ditching the edge for EFI live I never had that problem again.

check bernuelli's principle. in short by reducing the restriction of the exhaust gasses you increase the velocity of the air and it cools the air. turbo chargers work off of heat,(expanding exhaust gas). so if you are cooling the air in that area you will have less heat to drive the turbo charger and this would be most prominent in the lower rpm range.

Funny Pat dynoed the diamond eye pipe against the stock one and seen no change in power until above 3000 rpms then it made more in that rpm area. Around 15 rwhp more up top than the stock one. The up pipes and manifolds(stock ones) and the exhaust housing on the turbo is where the restriction is.

check bernuelli's principle. in short by reducing the restriction of the exhaust gasses you increase the velocity of the air and it cools the air. turbo chargers work off of heat,(expanding exhaust gas). so if you are cooling the air in that area you will have less heat to drive the turbo charger and this would be most prominent in the lower rpm range.

What you are talking about only applies in the pre-turbine area of the exhaust system. everything behind the turbine should be designed to allow the best possible flow away from the turbo to help let that used heat out. The downpipe swap will not loose a noticeable ammount or power on the bottom end, there is something else going on. Bad fuel, plugged fuel filter, any multitude of things...EFI live scanner sould be very helpful here.

why do you think hp increased above 3000 rpm could it be related to air flow ?. you said the restriction is before the turbo so if the downpipe alone created more topend hp do you think it would have an effect on the lowend also ?.

if the factory exhaust infact does not cause any restriction then yes what you said would apply. i have been told if you remove the cat only you will see anoticeable improvement in performance on these trucks. i have noticed the same problem on other diesel trucks when the exhaust is modified to a larger size. also changing more than one thing at a time can make finding a problem a bear. i agree that there could be another problem causing this issue i am just trying to help.

Guys, I read tony (the OP) truck today, he took me for a ride, and it feels the exact same as a stock 6128 tune, my best bet, is that it was a bad case of fuel filter clogging, as he changed it this morning.

As steveford said, the downpipe doesn't make any difference, just like the bd manifold. you wont notice any mileage gains, power loss or power gain, its on of those things you dont see a pay back on.

I don't know how it works out on paper, if a downpipe and cat delete helps or not but two months ago I went from cat back to a cat delete and downpipe and there is a power gain. I haven't tracked it long enough to say how it has affected my fuel mileage if at all but there's no doubt I can tell a HP increase.

There's also lower EGT's and the turbo spools faster. I'd do it again in a heartbeat. I'm going to have to put the cat back on when I get emmissions tested but the time/money is well worth the effort to me.

Thanks Brian for coming over & the help yesterday. Much appreciated. I cleaned my MAF sensor & replaced the fuel filter. I noticed a differance after that. I don't notice a big performance difference with the downpipe other then lower EGTs. The combo of cat delte & downpipe lowered my EGT's over 200 deg. I think I'll be making the upgrade from Edge to PPE this year also.

Thanks Brian for coming over & the help yesterday. Much appreciated. I cleaned my MAF sensor & replaced the fuel filter. I noticed a differance after that. I don't notice a big performance difference with the downpipe other then lower EGTs. The combo of cat delte & downpipe lowered my EGT's over 200 deg. I think I'll be making the upgrade from Edge to PPE this year also.
No problem tony, i was glad to help. :cool:

did you get some smoke back?

did you get some smoke back?

A hair when stock tune was in, quite a bit in edge level 6

The blocker plate blocks what was going to the egr system and allows it all to go to the turbo therefore you get faster spool up and more compressed air in the mix therefore the loss of smoke which is what you want in the overall scheme of things. As far as for power loss, dunno, not familiar with that pipe but I have to assume it is no different than any other. Just a bent piece of pipe. I know that the mbrp 4" straight piped setup shows a slight increase on the dyno over the stock exhaust but with a stock turbo you will actually lose bottom end and increase spool up time with a 5" kit with no kitty or muffler. The reason for going to a larger exhaust is to lower egt's when adding a programmer so a slight hp loss, if any, over stock is negated by the added power from the programmer. Besides the "cool" factor there is no reason for having an aftermarket exhaust on an otherwise stock truck.

Not much smoke back but it runs a hell of alot better. Not sure if i had some crappy fuel or what... Thanks for everybody's help. I'm going to do my PVC reroute this weekend.

The blocker plate blocks what was going to the egr system and allows it all to go to the turbo therefore you get faster spool up and more compressed air in the mix therefore the loss of smoke which is what you want in the overall scheme of things. As far as for power loss, dunno, not familiar with that pipe but I have to assume it is no different than any other. Just a bent piece of pipe. I know that the mbrp 4" straight piped setup shows a slight increase on the dyno over the stock exhaust but with a stock turbo you will actually lose bottom end and increase spool up time with a 5" kit with no kitty or muffler. The reason for going to a larger exhaust is to lower egt's when adding a programmer so a slight hp loss, if any, over stock is negated by the added power from the programmer. Besides the "cool" factor there is no reason for having an aftermarket exhaust on an otherwise stock truck.


The egr flows only a few % when on, usually at idle. You dont have slower spool up with it on. I havent had a loss on my bottom end with my 5" straightpiped and downpipe, remember diesels dont need backpressure to run.

Not much smoke back but it runs a hell of alot better. Not sure if i had some crappy fuel or what... Thanks for everybody's help. I'm going to do my PVC reroute this weekend.


SEXY !!!!!

sorry i just want to do that too but its still cold up here in the Great White North !!

On My Lbz I Ran 4 Inch Cat Back Muffler Then Pulled Off Cat And Lost Power And Boost One Power Level And 6 Lbs Boost Tried Everything Had My Buddy At Dealer Look At It And He Had To Reinstall Cat To Get Truck Back To Were It Was It Ran Best With Cat On Then Straight Pipe Back Some Trucks Like Some Dont

On My Lbz I Ran 4 Inch Cat Back Muffler Then Pulled Off Cat And Lost Power And Boost One Power Level And 6 Lbs Boost Tried Everything Had My Buddy At Dealer Look At It And He Had To Reinstall Cat To Get Truck Back To Were It Was It Ran Best With Cat On Then Straight Pipe Back Some Trucks Like Some Dont

Somethin else had to be going on there. It simply doesn't jive that a turbocharged engine runs better with a restriction behind the turbine section of the turbocharger, especially if it is a vvt. Turbochargers work on a pressure differential on the turbine side, this is what provides the power required to drive the compressor side. if you restrict the outlet of the turbine in any way you efectively reduce this pressure differential and reduce turbine horsepower. From the book on turbocharging by Corky Bell "the best exhaust for a turbocharged vehicle is no exhaust."

Somethin else had to be going on there. It simply doesn't jive that a turbocharged engine runs better with a restriction behind the turbine section of the turbocharger, especially if it is a vvt. Turbochargers work on a pressure differential on the turbine side, this is what provides the power required to drive the compressor side. if you restrict the outlet of the turbine in any way you efectively reduce this pressure differential and reduce turbine horsepower. From the book on turbocharging by Corky Bell "the best

I don't know whats so hard for people to understand about that... i guess they're are all used to driving and working with Gas N/A engines....

07 lbz, installed 4" mbrp on totally stock truck ,lost off idle bottom end enough to notice immediately. so it seems at least some trucks require some back pressure, and it did throw code for egr function. After the Bullydog on extreme, and an lly boost stick, this truck was a pleasure to drive for the year I had it and 33k miles.
D.

07 lbz, installed 4" mbrp on totally stock truck ,lost off idle bottom end enough to notice immediately. so it seems at least some trucks require some back pressure, and it did throw code for egr function. After the Bullydog on extreme, and an lly boost stick, this truck was a pleasure to drive for the year I had it and 33k miles.
D.

The part underlined in red is the key to your los of power. In the event of an emissions system malfunction the ECM limits fueling...hence a loss of power.