///// LOVE my 3 incher ...... Turbo back exhaust thst is ;-O !! ..... /////

Andyinchville1

Veteran Member
Joined
Apr 7, 2016
Location
Virginia
TDI
2003 Jetta TDI wagon, 5 sp, 226K miles
HI All,

Just thought I would post my findings on a 3" Turbo back exhaust system on my car (mods listed in signature)

Having had a 4" exhaust on a stock first gen Cummins Dodge Pick up and seeing some benefits , I was wondering what good things could (would?) happen if a 3" system was put on our cars.

While many have said that there would be be little or no gains with light mods (or heavy mods for that matter) on the little TDI .... I pressed ahead and got a Kerma TDI 3" turbo back system (resonator only no muffler) system and finally got it installed ( I had it for many months so I was quite anxious to get it on). Go big or go home right ? HA

Anyways here is what I found :

1) Noise at idle is not really noticeable ... you can hear turbo whistle and a little low tone growl ... when you start up you know something is NOT stock BUT in a good way!

2) No real drone until about 1875 RPM up through about 2350 RPM .... I imagine the exhaust would sound nice BUT drone drowns out the turbo whistle and growl mostly.

3) Boost happens MUCH faster than before ....
hit a couple overboost check engine codes without trying hard at all .... Learned to roll throttle more than quick jab to give the actuator time to pull back boost .
May not be a good thing if you are trying to punch it to quick merge into traffic , boost gets high and you end up limping in front of a huge tractor trailer you probably shouldn't have pulled out in front of in the first place ! (OK that did not happen BUT that COULD happen if you ecpect power to get you outta there ... maybe a tune is needed to fix that?). Maybe a stock system would still limp mode out under those conditions too?

4) I can't say for sure if boost is higher in general BUT it does happen quicker.

5) OK for me this is one of the BEST parts ..... My car typically gets between 50 and 53 MPGs on the highway ... I cannot remember the last time I got under 50 MPG on a tank ... I have had a 54 MPG tank BUT subsequent tank was low so I assume that was a fluke.

Anyways .... drum roll ...

I just took a trip to Pittsburg last night for work .... On the way up I got 55.2 MPG and on the way back I got 55.4 MPG !!

I have NEVER gotten 55 before (much less on 2 separate fill ups (same gas station , same fuel pump, manually calculated) SOOOO I believe a good exhaust is a plus !!

In all fairness and in full disclosure , at the same time I had the exhaust done I had the following done also :

1) 1" spacer to raise the front end to make the car sit level ( I had previously installed a metal skid plate and of course that reduces ground clearance so I wanted to get that clearance back and level the car out for better aero (my theory being a level car slices the wind easier .... if it is raked front low then the car gains weight at speed due to wind pushing the car body down ... of cousre it the front is high relative to the rear aero is lost as the speed increases since now the energy wants to "lift" the car ..... knife edge level just "cuts" the wind for better aero ? ... well thats my theory at least

2) Advanced the timing a bit (according to the VAG COM it was not advanced enough (towards the green line per guru tom ... theorized maybe timing belt stretch caused it to be a bit low ? 71K on timing belt

In conclusion , I NEED to research to kill the drone BUT other than that about 2 MPG more is GREAT !!

Maybe not cost effective for 2 MPG or so .... BUT the MPGs AND sound ( if I can get rid of the drone) ..... wow ... wish I did it sooner !!

For those with real power mods maybe the exhaust would help you more .... this was just based on my car with my driving style / habits and listed mods

Side note : NOW I cannot wait to put in a freer flowing INTAKE ... I already have the BRM intake .... ( like to get OMI and PD150 piping / air box), better side mount inter cooler ..... and Yes maybe even a turbo! Let me stop before I break the bank! HA

Andrew
 

Shenandoah

Veteran Member
Joined
Jan 9, 2008
Location
Shenandoah Valley, VA
TDI
2005 Jetta Wagon; 2005 Beetle; 2004 Jetta; 2002 Golf (three of them); 2002 Jetta Wagon; 2000 Audi TT->TDI; 1999 Beetle
How are you going to pass the annual inspection in Virginia?

Eric
 

Andyinchville1

Veteran Member
Joined
Apr 7, 2016
Location
Virginia
TDI
2003 Jetta TDI wagon, 5 sp, 226K miles
How are you going to pass the annual inspection in Virginia?

Eric
Hmmm that's a good question .... I got the car inspected before getting the work done so I have 8 months to get it figured out.

Maybe Farm Use tags ? ... that may be a tough sell tho

Still 8 years away from antique tags ...

Probably best bet is to take it to a Non VW dealer and hope they don't look too hard or maybe it is / looks like a high flow cat ( of course adding a stainless heat shield may help the look this but it should probably have one just in case ... easy enough to do... I'll have to google what a high performance one looks like but this one looks like a cylindrical one minus the heat shield and I think some are small enough not to need one?

Of course when I had my pick up truck, it passed for years as it was before anybody (including me) even knew it should have had a cat .... my solution to that was to take it to another shop for inspection.... I guess it's just luck of the draw.

Andrew
 

drucifer

Veteran Member
Joined
Dec 21, 2013
Location
fredericksburg virginia
TDI
2004 jetta sw tdi pd
At least you aren't trying to emissions test it. Did you save the old exhaust. You might get good at switching it once a year. Look for small inspection stations with no lifts.
 

scooperhsd

Top Post Dawg
Joined
Aug 19, 2003
Location
Kansas City KS
TDI
NB, 2000, RED(5 Speed conversion) 2015 Golf SE
My 2000 Beetle has had this for 5+ years now. I got this right before I got a Rocketchip Stage2 tune. I haven't noticed any lag in power output, but with my super large injection nozzles it's easy to get smoke, so my RC2 tune has something less radical below 3000 RPM. Even in town a tank MPG will do 42 MPG, and a highway tank is good for at least 45 MPG (stock gearing / wheels & tires). I'm also using a stock 11mm fuel pump (w/ 5 speed manual).
 

IndigoBlueWagon

TDIClub Enthusiast, Principal IDParts, Vendor , w/
Joined
Aug 16, 2004
Location
South of Boston
TDI
'97 Passat, '99.5 Golf, '02 Jetta Wagon, '15 GSW
55 MPG on an extended drive is good but not extraordinary. The old rule of 60 MPG at 60 MPH, 50 MPG at 70 MPH, 40 MPG at 80 MPH is still (roughly) accurate. Best FE I've gotten in my Wagon is 52.9 driving up through upstate NY and southern Ontario to the UP on the way to the 2016 TDIFest.

If I recall I filled the car in Albany, filled it again after crossing into Michigan via Sault Ste. Marie. The drive across Ontario was at 90-100 km/h which is pretty ideal for these cars.
 

Andyinchville1

Veteran Member
Joined
Apr 7, 2016
Location
Virginia
TDI
2003 Jetta TDI wagon, 5 sp, 226K miles
At what speeds were you driving on the trip?
Using the engine run hour meter (installed 49,261 miles ago) and the car's odometer for mileage , it's interesting that the overall average speeds driven (well at least based on engine run time) is in reality fairly low due to idling at stop lights ,slow traffic etc...

The average speed going to Pittsburg was 42.8 MPH ( I had some miles on the tank before I filled up on the way to Pittsburg)

The average speed from Pittsburg was 47.26 MPH (I figured it would be low due to snowy conditions).

As a comparison ....

Over the last 26,795 miles my average speed was 41.77 MPH

overall average speed for last 49,261 miles driven is 40.39 MPH

Some typical driving patterns are :

NIGHT: (due to deer ... speeds are held lower typically) DAY : speeds typically held uniform on the highway to get MPG baseline to
to determine car mod effect / benefits

Speed limit / NIGHT Speed / DAY speed
25 30 30
35 40 40
45 50 50
55 50 62
65 62 65
70 62 65
75 62 65

Although the MPGs at various speeds is probably somewhat higher on highway runs VS more mixed driving I have no way to accurately figure MPG's for a given speed (despite running a scan gauge that I have not fully set up BUT supposedly you can get instantaneous MPGs as well).

I am typically only able to calculate MPG's when I fuel up by the tank .... I was excited by the back to back 55 MPG tanks because I have never gotten back to bank tanks that high before (typ 52 / with a few 53 max ) despite having done many highway runs (NY, NJ, OH, GA etc ....).

Looking back to when I first got the car I was LUCKY to see high 40's (typically 46 / 47 / an occasional 48 / MPGs) and that was when I was doing similar runs so the listed mods (well I'll have to update them now that I think about it) have brought the cars MPGs to where it is now.

I would imagine modding the intake side of things would help , as would a 6 speed trans and aero ( I made acrylic grill blocks but the lower block got broken on the last deer strike .... I'm planning on doing that again and trying out harder core aero mods (belly pan , kamm back ) when time permits .

I wonder if running on flat terrain would help ? ... a lot of my driving seems to have lots of hills but I guess that's what I'm working with so I guess changes in fuel tank MPGs will still show a comparative difference tho.

I'm hoping this next tank is a 55er also ....

PS - not sure why when posted the columns I had spaced fairly nicely gets all scrunched up .....
 
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IndigoBlueWagon

TDIClub Enthusiast, Principal IDParts, Vendor , w/
Joined
Aug 16, 2004
Location
South of Boston
TDI
'97 Passat, '99.5 Golf, '02 Jetta Wagon, '15 GSW
I've had a pretty good FE run this fall.


Surprising because my pandemic highway cruise speed is about 80, although sometimes it's 85-90 if that's what traffic is doing. I do have a .700 5th gear which I think helps a lot. 90 is around 2900 RPM.

This is with a 2" downpipe, no cat, and stock exhaust from the downpipe back. Nice and quiet. I got tired of the drone from the 2.5". I had a muffler, but I think it was shot.
 

Andyinchville1

Veteran Member
Joined
Apr 7, 2016
Location
Virginia
TDI
2003 Jetta TDI wagon, 5 sp, 226K miles
I've had a pretty good FE run this fall.


Surprising because my pandemic highway cruise speed is about 80, although sometimes it's 85-90 if that's what traffic is doing. I do have a .700 5th gear which I think helps a lot. 90 is around 2900 RPM.

This is with a 2" downpipe, no cat, and stock exhaust from the downpipe back. Nice and quiet. I got tired of the drone from the 2.5". I had a muffler, but I think it was shot.
Wow with cruise speeds like that I wouldn't know what to do with all my free time saved from driving ! HA

I like the big exhaust for seemingly the mileage boost and have been reading alot on how to kill the drone ....

it's a shame that the kit could not be engineered from the get go and come with enough resonators amd other "stuff:" to make it drone free from the factory....( well at least in 2200 RPM and under range ... If it could do that I would be way happier..... Droning at the higher RPM's would be fine with me because I'm not there to often and If I am pushing it that hard I WANT to hear things going on !!

Other than going back to smallish diameter piping, did you try extra resonators , adding mass to the pipes, free flow mufflers etc ... with any worthwhile results?

On the flip side , maybe with aging and the damage of the ear drums from the constant droning .... hearing loss may make drone reduction solutions a moot point ;-)

Oh yeah , the relative ease of overboost and throwing codes is a little annoying too but with careful modulation of the accelerator you can get smoke free / haze free brisk acceleration because of the extra boost but push it a little too hard or a little too long and you are "rewarded" with a code and maybe a limp too ..... It's a fine line..... Admittedly, it's kind of fun to get it just right ... Almost like making the perfect shift.

I am assuming a tune correction / update could take care of that BUT since I am planning more mods I''ll probably hold off a bit until some of the other mods are done then get a single redo on the tune to take care of it all ....

In a previous thread by somebody else ... I think the statement above would not be an issue IF I had a Kerma tune because you can get free upgraded tunes if you buy parts from them ....

It just happens I have a Malone Tune so sadly we have to pay for changes .... maybe I can get a discount if it's just small changes ? .... I may reach out to them and ask .... I guess the worse they can say is no.

Back to researching! but first I have to do a run to pay for parts .....
 

300D

Veteran Member
Joined
Jun 8, 2018
Location
New England
TDI
Mk6
I know it’s not 3”, but I have no drone from a stainless 2.5” turbo back with refreshed factory cat and stainless magnaflow muffler with down turn at exit. Maybe a few simple tricks like a downturn or a muffler could help?
 

ghohouston

Veteran Member
Joined
Apr 2, 2013
Location
Lewisville, Texas
TDI
2001 Jetta Sedan TDI 5 Speed
You have a problem if you are overboosting just from having 3" turbo back exhaust. I've had it on 2 different Alh's and many many miles, and other than when I had a worn turbo vane issue, never had any overboost issues.
 

Andyinchville1

Veteran Member
Joined
Apr 7, 2016
Location
Virginia
TDI
2003 Jetta TDI wagon, 5 sp, 226K miles
I know it’s not 3”, but I have no drone from a stainless 2.5” turbo back with refreshed factory cat and stainless magnaflow muffler with down turn at exit. Maybe a few simple tricks like a downturn or a muffler could help?
HI,

The 3" Kerma kit has a turndown that ends up under the car like the factory exhaust .

I have read that having an exhaust end up under the car could be a cause of drone since the sound is "trapped" under the car and reflects underneath it .... I suppose that sounds reasonable.

On the flip side, I had a 1993 Dodge with a Cummins and a 4" turbo back system ( Just pipe nothing else ... not even a resonator) that exited like the factory pipe off to the side and was NOT under body but man that thing did drone too !

So maybe the simple solution of just exiting the exhaust from under the body may not be the final solution.

I am thinking about another resonator where the stock muffler was .... there is plenty of space.

I have also read about a tuned "j " Pipe ....

Weights on the exhaust system sounds like hocus pocus BUT some factory systems acytally have weights on the exhaust to presumably reduce drone and bad sounds.

As a last resort I , I may try some sort of muffler .... I almost hate to add restriction back to the system since the goal for free flow was to make things more efficient for more MPGs (which it HAS helped but not necesasarily in a cost effective way ... but I'm still happy with it) .

I did use ear plugs on todays trip to Hershey ....

As a last thought, I think bose makes an active sound cancellation system (headset) .... I wonder if that could be modded to use speakers to cancel out noises so you don;t have to wear the headset which is not only inconvenient but would probably rub the law the wrong way ...

Now that I think about it maybe I should disguise my bright orange earplugs ..... of course maybe the tinted windows mutes that down enough
 

Andyinchville1

Veteran Member
Joined
Apr 7, 2016
Location
Virginia
TDI
2003 Jetta TDI wagon, 5 sp, 226K miles
You have a problem if you are overboosting just from having 3" turbo back exhaust. I've had it on 2 different Alh's and many many miles, and other than when I had a worn turbo vane issue, never had any overboost issues.
Yes, it is an overboostin son of a ............. gun ( Had to keep it PG ! ... I think in todays PC just saying "gun" keeps it form "g" HA).

Anyways, I have my scangauge installed permanently installed mainly for on the fly info but it is good for getting rid of the annoying check engine lights as they pop up ....

I had to use it several times today and I was not intentionally pushing too hard but apparently I was.

With the stock exhaust I would have a very occasional overboost but only when I was trying.

With advice from here on the forum and the guru that works on my car , I took to exercising the turbo more often (aka Itallian Tune ups). ...

This seemed to help matters and was done as preventative maintenance (don't want to HAVE to take the turbo apart to fix a frozen ring mechanism).

When we added the Kerma system , I guess it was just soooo much freer flowing that I was throwing overboost codes easily.

Boost comes on Right NOW and in quantities way more than good ... I glimpsed at 23 psi early on.... (I know I have to go easy to keep from blowing the turbo).

I am thinking a my tune needs to be modified BUT since it costs $$ each time , I will keep it as is until I get the BRM intake and upgraded turbo on then get a new tune.

Maybe you did not get overboosting becuase you had fewer mods?

I just noticed you have a sedan with the Kerma 3" exhaust .... do you have issues with drone ? what did you do to correct that?

Thanks
 

GlowBugTDI

Veteran Member
Joined
Jul 20, 2018
Location
Cambridge, MN
TDI
2001 Beetle GLS TDI (BIODSL). 01 original Glow Bug TDI (sold)
HI,

The 3" Kerma kit has a turndown that ends up under the car like the factory exhaust .

I have read that having an exhaust end up under the car could be a cause of drone since the sound is "trapped" under the car and reflects underneath it .... I suppose that sounds reasonable.

So maybe the simple solution of just exiting the exhaust from under the body may not be the final solution.

I am thinking about another resonator where the stock muffler was .... there is plenty of space.

Weights on the exhaust system sounds like hocus pocus BUT some factory systems acytally have weights on the exhaust to presumably reduce drone and bad sounds.

As a last resort I , I may try some sort of muffler .... I almost hate to add restriction back to the system since the goal for free flow was to make things more efficient for more MPGs (which it HAS helped but not necesasarily in a cost effective way ... but I'm still happy with it) .
Drone can be cause by a number of things. If the exhaust isn't going past the end of the car it will drone (like you said trapped underneath in a way). A downturn will sometimes do that at certain speeds/rpm as it makes the noise bounce of the pavement. Sometimes if there is wind it can cause that as well on a free flowing exhaust. A muffler or cat will make the sound go away as it breaks it up. You also stated that weights on the exhaust might work. I would be curious to know if adding some magnets to the exhaust would reduce drone. I say this because in blacksmithing you put magnets on the anvil to reduce vibration (similar idea?). I bet it would do something, but to what extent i do not know. I wish I would have tried it on my last beetle which had the exhaust chopped in so many different ways during my time of owning. I even ran turbo back nothing for a bit of time (technically had about 1ft of pipe behind the turbo) that was interesting.
 

ghohouston

Veteran Member
Joined
Apr 2, 2013
Location
Lewisville, Texas
TDI
2001 Jetta Sedan TDI 5 Speed
Yes, it is an overboostin son of a ............. gun ( Had to keep it PG ! ... I think in todays PC just saying "gun" keeps it form "g" HA).

Anyways, I have my scangauge installed permanently installed mainly for on the fly info but it is good for getting rid of the annoying check engine lights as they pop up ....

I had to use it several times today and I was not intentionally pushing too hard but apparently I was.

With the stock exhaust I would have a very occasional overboost but only when I was trying.

With advice from here on the forum and the guru that works on my car , I took to exercising the turbo more often (aka Itallian Tune ups). ...

This seemed to help matters and was done as preventative maintenance (don't want to HAVE to take the turbo apart to fix a frozen ring mechanism).

When we added the Kerma system , I guess it was just soooo much freer flowing that I was throwing overboost codes easily.

Boost comes on Right NOW and in quantities way more than good ... I glimpsed at 23 psi early on.... (I know I have to go easy to keep from blowing the turbo).

I am thinking a my tune needs to be modified BUT since it costs $$ each time , I will keep it as is until I get the BRM intake and upgraded turbo on then get a new tune.

Maybe you did not get overboosting becuase you had fewer mods?

I just noticed you have a sedan with the Kerma 3" exhaust .... do you have issues with drone ? what did you do to correct that?

Thanks
First alh was with dlc 1019 injectors, and no overboost codes. Current has dlc 764s which are a bit larger, set to stage 3 flow, and same exhaust. Now has a ported head as of recently too, no overboost, again other than when I had 1 vane that was damaged somehow constantly binding, causing issues. The exhaust exiting under the car definitely causes drone. I took mine out the side behind the passenger rear tire, like most diesel pickups have, and there is very little drone. And it is fully straight piped.
 
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