'97 Passat TDI Build

[Caddylackn]

Now that the plastic side of the diffuser is in, time to remove the two mufflers, build a cat back exhaust, then install, then finish the driver side of the diffuser.

I was able to reuse some of the stock bends. The stock pipe was 2" od and stainless and cleaned up nice. I bought a 2" 90 degree bend, and 2 - 18" straight pipe. Welded, then painted with high heat paint.



Then install with some clamps. I do have a slight rub problem. More on that later.



Then finished the driver side diffuser in sheet metal and installed. Then the two bumper undertray pieces and then spray bomb in green.



I left the tailpipe exit protrude long, since the diffuser angle will probably change and the end of the diffuser will be lowered. I wanted to have the exhaust exit near flush to the diffuser surface, as this should be the lowest pressure area. I am trying to get a few thermal efficiency bumps on the motor. The TDI motor is not any louder at all with both mufflers removed and I probably shed 40 to 50 lbs. I have read that reducing back pressure is bad for mpg in a TDI and I have heard that it is good for mpg in a TDI. I am going to find out.

I will do a future write up on how each of these mods effected my mpg and drivability. I record my every day commute each way trip mpg. I drive it the same every day at the same mph, so I can see what the mods I do, do to mph.

So far, I found that with the catback, my driving in cruise mode boost pressure is higher than before, like 16 - 17 psi (absolute) versus the 15.5 to 16 psi before. That is the opposite of what I wanted to accomplish.

But, the mpg going up hill went up 10-15%, so the lack of back pressure helped the turbo to spool more efficiently, it appears. So long hills that I used to get 30 mpg going up at 55 mph, I am not getting 35 mpg or so. My level cruising mpg seems the same. But my one-way trip mpg went up consistently 2 mpg each way. Some of this could be because the diffuser and bumper undertray is now finished.

Of course I left the catalytic converter on. Removing it is illegal. I do have a bad tail pipe rattle, where it is hitting the subframe brace. Sounds like somebody is hammer drilling concrete inside the car, at idle. Goes away when in gear on the motor. I need to fix that, it sucks.

[oil pan 4]

Turbo diesels don't like back pressure.
Do you know if there is an EGR system?

[Caddylackn]

I have a working EGR.

It is not possible to turn off the EGR with a VAG-COM nor should it be turned off. The working EGR system should not decrease the gas mileage.

[oil pan 4]

In a diesel it will usually hurt fuel economy.
Only time EGR helps fuel economy for sure is in very cold climates.
Don't have to delete anything, just make a sheet metal gasket with no hole for the exhaust to flow through. It's all there and still "working" as far as the ecu is concerned.
EGR on diesels is known for increasing tail pipe soot, decreasing fuel economy and decreasing horsepower.
With this mod you can try it and if fuel economy goes down you can easily undo it. Also I have heard of 1.9t intake manifolds becoming horribly clogged with diesel soot.

On a gasoline engine the EGR being disabled usually decreases fuel milage. It does not effect peak power because the EGR closes at around 1/2 throttle.

Also does it have a cold air intake or intercooler?

[freebeard]

Don't have to turn it off, just make a sheet metal gasket with no hole for the exhaust to flow through. It's all there and still "working" as far as the ecu is concerned.

Now there is a hacker mindset.

[Caddylackn]

Originally Posted by oil pan 4

In a diesel it will usually hurt fuel economy.
Only time EGR helps fuel economy for sure is in very cold climates.
Don't have to delete anything, just make a sheet metal gasket with no hole for the exhaust to flow through. It's all there and still "working" as far as the ecu is concerned.
EGR on diesels is known for increasing tail pipe soot, decreasing fuel economy and decreasing horsepower.
With this mod you can try it and if fuel economy goes down you can easily undo it. Also I have heard of 1.9t intake manifolds becoming horribly clogged with diesel soot.

On a gasoline engine the EGR being disabled usually decreases fuel milage. It does not effect peak power because the EGR closes at around 1/2 throttle.

I don't disagree with anything you say, but removing (or modifying) working emissions equipment from motor vehicles that travel on public roads is a Federal crime in the US, and they are cracking down on it. If I did do something like that I would not post about it on a public forum, doing so could get the forum in trouble.

Now, I will say that when my Passat is not driven on a public road, the EGR is turned down to the minimum using the VAG-COM so that soot is not clogging up my intake manifold .

[Caddylackn]

Yes, it does have a factree intercooler.
I did a lower grill block but left a smoothed entrance hole for that.

Yes, these intake manifolds become horribly clogged, like over 75% of the passage clogged and up to 50% of the intake ports in the head. Mine was that way when cleaned at 230k miles, probably for the first time cleaned

[oil pan 4]

I murdered all my emissions equipment on certain vehicles a long time ago.
Here crackheads have been stealing catalytic converters, most of the people who have their converters stolen just have a pipe welded in its place so it don't happen again.

Something strange diesel engines do is over time they produce less NOx, where gasoline engines produce more. So if the EGR was blocked now, the engine could very well be making less NOx then when it was new. The break even point between gas vs diesel NOx back then in the 1990s was something like 50,000 miles.

[Caddylackn]

Didn't get to work on my undertray this weekend.
Too busy doing this:



to get to here;



To remove and replace the stupid aluminum and plastic heater core and fix the dreaded blender door missing foam. This is the Achilles heal of the Passat B4. The heater core will fail, and its a 10 hour repair job at the dealer. I will be a little over that in hours.

At least now I will have heat this winter, and have a new stereo wired up.

[oil pan 4]

Wow you went deep.