Author Topic: Easiest power modification (Read 6080 times)

love.the.smell · « **on:** July 21, 2008, 03:03:55 pm »

So I moved to CO this weekend. The rabbit was completely loaded with just enough room left for me to sit in it, tires almost rubbing the fenderwells, rear beam uncomfortably close to the fuel tank, and an exhaust rattle. About 270 miles into the trip I pull into a rest stop just outside of Iowa City and hear something rattling and scraping. The muffler fell completely off and was lying in the middle of the ramp. I wired up the rest of the rattling exhaust and strapped the muffler to the roof rack. Seemed like I gained a few horsepower from this mod

The remaining 700 miles were extremely noisy, hot, and slow. I found the best way to keep the car from overheating while making decent time is to draft behind a tractor trailer. On the positive side I only stopped three times for fuel.

zukgod1 · « **Reply #1 on:** July 21, 2008, 03:28:26 pm »

Sounds like my trip from Montana back to Utah. I drafted off a car transport truck for at least 200 miles..
He lost me going up a hill.

But ya, opening up the exhaust will help allot. I'm assuming y the Rabbit is NA.
If you plan on keeping it NA get a gasser exhaust manifold with (I cant remember what it's called) 2 holes where the down pipe hooks on. Suppose to be allot better than the OE exhaust manifold. Then get at least 2.25 pipe out the back with a good flowing muffler. I always recommend Magnaflow myself.
Advance the timing a tad and your off to the races, sorta.

burn_your_money · « **Reply #2 on:** July 21, 2008, 05:53:38 pm »

8V GTI exhaust manifold

ktzdsl · « **Reply #3 on:** July 21, 2008, 08:56:43 pm »

Sure would like to have either a part number or image of the 8v GTI exhaust manifold.
I have heard of "8v european gasser crossflow", "gasser" and now 8v GTI manifold. I have searched on the net, on the forums, ebay, but have yet to find one. What I currently have on my 1.6L NA pickup is part number 067-253-033, which has cyl 1 and 4 together and cyl 2 & 3 together. The outlet holes appear to be about 1 3/8 in diameter. I have a TT 2 to 1 downpipe. Runs ok, I am just wondering if I have the optimum setup for a 2 1/4" exhaust system.

shegel · « **Reply #4 on:** July 21, 2008, 10:00:09 pm »

Quote from: "ktzdsl"

Sure would like to have either a part number or image of the 8v GTI exhaust manifold.
I have heard of "8v european gasser crossflow", "gasser" and now 8v GTI manifold. I have searched on the net, on the forums, ebay, but have yet to find one. What I currently have on my 1.6L NA pickup is part number 067-253-033, which has cyl 1 and 4 together and cyl 2 & 3 together. The outlet holes appear to be about 1 3/8 in diameter. I have a TT 2 to 1 downpipe. Runs ok, I am just wondering if I have the optimum setup for a 2 1/4" exhaust system.

what your looking for is an 8v gli manifold. dual downpipe manafold.

http://www.gprparts.com/brands/techtonics/manifoldDownpipe.asp

i picked mine up for 20$ with the dp slightly modified

dieselwagen · « **Reply #5 on:** July 22, 2008, 07:53:15 am »

i got a $30 manifold/downpipe from craigslist. off of a '90 corrado.
it does have a 3 bolt flange and 2.5 inch collector diameter. i used a reducer to match it up to the rest of my piping.

does making a normally aspirated diesel breathe easier increases its efficiency? i have read somewhere there's not much in a way of intake mods since NA diesel breathes excellent already.
should an exhaust mod be complimented with intake mod?
just curious concerning NA efficiency right now, i know i need the Giles super pump for significant power increase in my 1.6NA

zukgod1 · « **Reply #6 on:** July 22, 2008, 08:14:43 am »

You have to look at engines of any kind Gas or diesel as just a big air pump. Anything you can do to get the air in and out easier will make it more powerful and efficient.

79rabbit4dr · « **Reply #7 on:** July 22, 2008, 10:04:25 am »

Quote from: "zukgod1"

...Anything you can do to get the air in and out easier will make it more powerful and efficient.

not entirely true... some back-pressure is necessary with many small displacement cars (read rice rockets :twisted:).

Also, short fat pipes help the most at high rpm while long thin pipes help the most with low end torque <-- at least on gassers. From what it seems like, diesels ARE all about mass amounts of air flow.

Here in Idaho we don't have emissions testing so I'd like to try just dumping the exhaust out the side and keeping the pipe real short and fat, just to see the difference in performance from the stock setup on there now.

love.the.smell · « **Reply #8 on:** July 22, 2008, 12:00:41 pm »

Thanks for all of the info. I would definitely like to do away with the toilet bowl setup in favor of a flange and bolts. Right now I'm trying to decide between putting just a new back half of the exhaust on ($46.57 @ www.autohausaz.com or buying a complete setup.

I don't really have any where to work on the exhaust or any way to weld, so I'm looking for something that will easily bolt on and not require much modification. I hate to send good money after bad for a replacement stock exhaust, but the TT setups are pretty pricey. My car currently doesn't have a cat. Is it necessary to install one? I would like to keep it emissions legal and somewhat environmentally friendly.

riddleyo · « **Reply #9 on:** July 22, 2008, 12:02:59 pm »

Quote from: "79rabbit4dr"

Quote from: "zukgod1"
...Anything you can do to get the air in and out easier will make it more powerful and efficient.

not entirely true... some back-pressure is necessary with many small displacement cars

Back pressure is never necessary on gas or diesel, no matter the engine size. You don't want to hurt exhaust velocity, which is why putting an oversize exhaust can hurt performance (which is where the back pressure myth originates from). There is the scavenging effect that works with NA cars, but that is only at certain RPM bands. You never want obstructions in the exhaust that create any amount of back pressure.

tylernt · « **Reply #10 on:** July 22, 2008, 10:00:18 pm »

Quote from: "riddleyo"

There is the scavenging effect that works with NA cars, but that is only at certain RPM bands

I thought the diesel cam had zero overlap, so, no scavenging?

dieselwagen · « **Reply #11 on:** July 23, 2008, 08:34:09 am »

Quote from: "tylernt"

Quote from: "riddleyo"
There is the scavenging effect that works with NA cars, but that is only at certain RPM bands
I thought the diesel cam had zero overlap, so, no scavenging?

NA cars don't enjoy the luxury of force induction, so it relies on exhaust scavenging to pull out "stuff" from combustion chamber as fast as possible and hopefully create a negative pressure inside cc for the intake charge.

riddleyo · « **Reply #12 on:** July 23, 2008, 08:54:22 am »

Quote from: "tylernt"

Quote from: "riddleyo"
There is the scavenging effect that works with NA cars, but that is only at certain RPM bands
I thought the diesel cam had zero overlap, so, no scavenging?

I was just saying naturally aspirated cars in general.

ProjectPurity · « **Reply #13 on:** July 25, 2008, 06:56:54 pm »

Can you find that exhaust manifold on a '82 Rabbit LS gasser?

Here's what ETKA pulls up for that year:

92EcoDiesel Jetta · « **Reply #14 on:** October 19, 2012, 07:18:15 am »

Quote from: ktzdsl on July 21, 2008, 08:56:43 pm

Sure would like to have either a part number or image of the 8v GTI exhaust manifold.
I have heard of "8v european gasser crossflow", "gasser" and now 8v GTI manifold. I have searched on the net, on the forums, ebay, but have yet to find one. What I currently have on my 1.6L NA pickup is part number 067-253-033, which has cyl 1 and 4 together and cyl 2 & 3 together. The outlet holes appear to be about 1 3/8 in diameter. I have a TT 2 to 1 downpipe. Runs ok, I am just wondering if I have the optimum setup for a 2 1/4" exhaust system.

Did you ever find a 8V GTI exh manifold? Take a look at this post, scroll down to Vanagonner's post, there's pics there. http://www.thesamba.com/vw/forum/viewtopic.php?t=474748

Is this the one?

Author Topic: Easiest power modification (Read 6080 times)

79rabbit4dr

92EcoDiesel Jetta