New cat back straight pipe affects on boost

eddieleephd

Top Post Dawg
Joined
May 27, 2012
Location
Asheville, NC
TDI
2002 jetta Wagon
Hey y'all, just had a 2.5" straight pipe from the cat back installed and did a little logging to compare before actual to after actual effects of the change.
The change was to remove the OEM resonator and muffler and replace it with a 2.5" straight pipe, Sounds mean and a little loud for my preference, however, the turbo doesn't whine out loud that I notice within the car.


As mentioned by others, the exhaust change doesn't affect the power much alone and these logs show that the spooling is improved which is the true benefit to having a low resistance exhaust.

Before I had adjusted it so that it would spool about 100mbar over in 3rd, without adjustment that number went up to 187mbar over in 3rd. 187/69=2.21psi compared to before 100/69=1.44 so the increase was about .8psi in third.
I have only run a couple logs so far, so, more logging is in the near future to review actual and decide if I should adjust it out a bit more.



I have an 02 1.8t auto wagon swapped to an ALH manual with a Malone stage 4 tune, 11mm ip, vnt17, egr delete, bmw cyclonic pcv filter, 3bar map, sbc stage2 DD, single mass flywheel, IQ around 3.



3rd - 5th before

https://log.malonetuning.com/chart/240555#H8KLCADDisOQw5FbAgNNwovDkQrCgzAMAMO%2FJcOPDcOow7BvSh%2FDqgw1w5A1wpLDhsOhw7bDtcOaCmPCj3fDh3kPT3nDjVwIwpPDisK%2BVXBDcE1mUcO%2Bw5LChQ4SFcOSaAR3KW9SQxM8MB7DnMKOw7vCicOLwoLCn8KfAsOlwrRaXyrDmV%2FDsMKPw6Bgw6whw64mdcOLbMONwo9TCCfCtzzDpifCjwAAAA%3D%3D


3rd 4th before
https://log.malonetuning.com/chart/...wwo/DoGDDrCHDriZ1w4tsw43Cj1MIJ8K3PMOmJ8KPAAAA


3rd - 5th after no adjustments
https://log.malonetuning.com/chart/...Pw6Bgw6whw64mdcOLbMONwo9TCCfCtzzDpifCjwAAAA==


3rd 4th after
https://log.malonetuning.com/chart/...Pw6Bgw6whw64mdcOLbMONwo9TCCfCtzzDpifCjwAAAA==


Edit one for addition of information.
Today I did a log with new injectors, with only a software IQ adjustment to knock down smoke, which are Wuzetem p502J from Frans at Dutch auto and man the smoke that is jumping out behind me.
Not quite rolling coal, but yeah I see it pretty well in the rear-view mirrors.


This is pretty much immediately after then turnaround and do it again logs, both are third to red-line and fourth to near 100mph:
and 322,400 mi on odometer.




https://log.malonetuning.com/chart/...wwo/DoGDDrCHDriZ1w4tsw43Cj1MIJ8K3PMOmJ8KPAAAA


https://log.malonetuning.com/chart/...wwo/DoGDDrCHDriZ1w4tsw43Cj1MIJ8K3PMOmJ8KPAAAA


new logs different tune and hammer mod
https://log.malonetuning.com/chart/246944
https://log.malonetuning.com/chart/246945

https://log.malonetuning.com/chart/246946
 
Last edited:

Scott02

Veteran Member
Joined
Jan 17, 2006
Location
near Youngstown, OH
TDI
Too Many
The boost control (and or your actuator rod adjustments) with stock exhaust was really not correct at all. Lots of sustained deviation between requested and actual.

The way the actuator rod adjustment and the tune are working together with your exhaust modifications is way better with way less deviation between requested and actual. Though your 3/4 pull still looks a good deal off. Your 3/4/5 pull looks better.
 

eddieleephd

Top Post Dawg
Joined
May 27, 2012
Location
Asheville, NC
TDI
2002 jetta Wagon
The boost control (and or your actuator rod adjustments) with stock exhaust was really not correct at all. Lots of sustained deviation between requested and actual.

The way the actuator rod adjustment and the tune are working together with your exhaust modifications is way better with way less deviation between requested and actual. Though your 3/4 pull still looks a good deal off. Your 3/4/5 pull looks better.
I definitely agree the deviation is a bit off and has been improved with the exhaust. I'm blaming the injector nozzles and am finding it to be rather difficult waiting for the new ones to arrive. Of course I had to go and get them from another continent and that always delays things a bit.
I messaged Malone and Owain said they look good as far as over-boost. I didn't really ask about the deviation as the nozzles presently installed are an unknown at the moment. I do expect that once I get the new injectors installed that the nozzles will be much better matched to the VNT17 and the tune presently installed, with a little logging and adjustment that is.

I also left it adjusted a touch low because I knew that I was going to get the exhaust done when I did the adjustment and anticipated the difference. Had I adjusted it to be like it is now, which I really wanted, I would be adjusting it back down immediately.


I really do like the outcome of the larger exhaust power and response wise. However, I want a straight through muffler, maybe one of the Magnaflow 2.5" in the stock location. From what I have read in a few different posts here, can't remember whose, experiments with the exhaust resulted in the stock location being the best placement for a muffler. I also had the tip of the exhaust bent down about 30 degrees and stopping under the muffler due to this being the best way to eliminate droning while not bombarding the person behind you either, while possibly encouraging the exhaust to stay behind rather than draft back into the hatch.

https://www.idparts.com/25-stainless-steel-magnaflow-muffler-p-1168.html

I still have a good bit of work getting it tuned perfectly so my fuel mileage is back up where I really want it, especially for a DD. Getting my foot out of it would help, but it's so fun!
 
Last edited:

WildChild80

Veteran Member
Joined
May 30, 2016
Location
Nashville, AR
TDI
2001 Jetta TDI 2000 Jetta TDI 2000 New Beetle TDI ALL 5 speeds
I have a 3 inch turbo back with an AutoZone tune down pipe...the one that the kit came with was just too long and I don't want everyone to know as it's not that loud under low boost

I wouldn't rush to suggest 3 inch as it rattles on the heat Shields and it annoying at times but it's only once in a while so whatever...

Sent from my Pixel XL using Tapatalk
 

red16vdub

Veteran Member
Joined
Aug 26, 2013
Location
(617) City of CHAMPIONS
TDI
03 JSW 5spd
I have a 3 inch turbo back with an AutoZone tune down pipe...the one that the kit came with was just too long and I don't want everyone to know as it's not that loud under low boost

I wouldn't rush to suggest 3 inch as it rattles on the heat Shields and it annoying at times but it's only once in a while so whatever...

Sent from my Pixel XL using Tapatalk

Rule of thumb, when replacing your exhaust systems, especially with a heavier 3” turbo back. Changed all hangers to prevent rattling, also inspected heat shield and adjust fasteners, remember exhaust rubber hangers sagged over time. Usually this goes unnoticed because it’s still stock, but when upgrading its a must.
Asked me how I know.


Bajan
 

scooperhsd

Top Post Dawg
Joined
Aug 19, 2003
Location
Kansas City KS
TDI
NB, 2000, RED(5 Speed conversion) 2015 Golf SE
I have a 3 inch turbo back with an AutoZone tune down pipe...the one that the kit came with was just too long and I don't want everyone to know as it's not that loud under low boost

I wouldn't rush to suggest 3 inch as it rattles on the heat Shields and it annoying at times but it's only once in a while so whatever...

Sent from my Pixel XL using Tapatalk

My Beetle has this, except I had a resonator put on the tailend to keep it subdued. Works fine with my RC2.
 

WildChild80

Veteran Member
Joined
May 30, 2016
Location
Nashville, AR
TDI
2001 Jetta TDI 2000 Jetta TDI 2000 New Beetle TDI ALL 5 speeds
My Beetle has this, except I had a resonator put on the tailend to keep it subdued. Works fine with my RC2.
Mine has a resonator also, love the sound... plenty of turbo whistle

Sent from my Pixel XL using Tapatalk
 

Pittdawg

Veteran Member
Joined
May 28, 2018
Location
Los Angeles
TDI
2014 Audi Q5 TDI
I have a 3 inch Magnaflow catback on my Q5 TDI. Only a modest increase in sound, basically just a bit deeper and ever so slightly louder, I actually really like how subtle it is. Spooling does seem to come on a bit quicker.
 
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