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Engine Specific Info and Questions => IDI Engine => Topic started by: Benjamin on January 12, 2007, 12:14:56 pm
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i'm making a home made downpipe and exhaust on my 1.9 with the vnt25.
i dont wanna become a loud honda sound when i drive normal (problebly also not possible), but it need to be a good perfomance choice for +200hp.
What is better, 2,25 or 2,5" for the exhaust? Os this size the diameter from the inner or the outside diameter (with or without matrial)?
the exhaust side on the turbo is 45mm, how big should i make the downpipe?
is it better to take a bigger downpipe than the exhaust, or is it the best to take the same size for the whole line?
(i know this discussion is done several times, i also readed the faq, but i ask again becouse i will have a bigger power gain)
Greetz, Benjamin
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I will be running a 2.5 outer diameter all the way from the turbo back....no mufflers and from the sound clips I have heard on here its not loud at all!!! I dont think you would need more than 2.5 inch....besides its a lot easier to fit rather than a 3inch.....if you want a different size downpipe i would make the exhaust bigger than the downpipe!!!
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i am running 2.5" from the downpipe back, no cat, no muffler, nothing, straight pipe. Not loud at all, the turbo is your muffler.
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i am running 2.5" from the downpipe back, no cat, no muffler, nothing, straight pipe. Not loud at all, the turbo is your muffler.
is it louder on idle? is 2.5" the inner or outer diameter?
Sounds to me i go will for a 2.5" outer diameter exhaust, what size is the best choice for the dowpipe on this install?
Greetz, Benjamin
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when i removed the cat and muffler, i noticed no increase in noise, the engine is louder than the exhaust.
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when i removed the cat and muffler, i noticed no increase in noise, the engine is louder than the exhaust.
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How does this affect the MOT?
Thanks
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What's a MOT? you mean emissions or legallity? It's legal here anyway, emissions passed aircare no problem.
when i removed the cat and muffler, i noticed no increase in noise, the engine is louder than the exhaust.
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How does this affect the MOT?
Thanks
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What's a MOT? you mean emissions or legallity? It's legal here anyway, emissions passed aircare no problem.
Woops!
Confused you with 'Regcheesman' in UK but you answered correctly...
MOT 'Ministry of Transport' annual roadworthyness test... :oops:
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i noticed no increase in noise, the engine is louder than the exhaust.
Yep... same here. I've got a 2.5" downpipe and exhaust and I can hear the turbo and exhaust note, but the engine is louder than that. Rattly for sure. I've always been told that turbo engines don't need any restriction at all for "back pressure" after the turbo.
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Got a custom made 2.5" system made up today. Sounds great and has a lot more power :shock:
To go 3" is of more benefit especially if you plan to up the boost. But it requires more custom fabricating and will cost a significant deal more money.
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Does anyone know the size of the stock downpipe? I want to upgrade this part, but is it really necessary if im not running much power right now? Also, is a 2.5" exhaust going to make a big difference if you still have the stock downpipe? Perhaps the feeling of power is just all in my head?
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straight piped with 2.5inch on a TD is quieter then a gasser with 2 resonators, a cat, and a muffler lol.
you're good to go.
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2.5-3"
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straight piped with 2.5inch on a TD is quieter then a gasser with 2 resonators, a cat, and a muffler lol.
you're good to go.
Its pretty loud under full throttle though :lol:
Sounds like a semi truck and the whistle exhaust sound. Ooo, I love it. I won't regret it :shock:
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^ i concur 101%!
as my friends following call it, "The whoooshy zoot noise!"
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all i hear is this strange whistling noise with my 2.5 in straight pipe??? i must be going crazy or something and this high pitched noise like something is spinning really fast just beyond the firewall?? strange...
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all i hear is this strange whistling noise with my 2.5 in straight pipe??? i must be going crazy or something and this high pitched noise like something is spinning really fast just beyond the firewall?? strange...
lol... :lol:
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straight pipes 4 life, at least 2.5 maybe 3 if you can pull it off, it is quiet and sounds like a choo choo train
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1.6TD with 2.5" - turbo back...no muffler/no nothing...:D http://s5.photobucket.com/albums/y165/80Rabbit/?action=view¤t=100_0319.flv
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damn that sounds good!
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(http://i124.photobucket.com/albums/p28/giulianot/mixed2253.jpg)
(http://i124.photobucket.com/albums/p28/giulianot/mixed2252.jpg)
3" downpipe 2.5" from flex back! Point your exhaust tip down to keep black smoke off the rear of the car :twisted:
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can you guys post pictures of your downpipes?
i have a friend that could do one for me but he said that the best would be to find a 1.9 downpipe because it is better to weld... :idea:
also,do you have to put a flex on it?
the stock one doesent have... :?:
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can you guys post pictures of your downpipes?
i have a friend that could do one for me but he said that the best would be to find a 1.9 downpipe because it is better to weld... :idea:
also,do you have to put a flex on it?
the stock one doesent have... :?:
the one i made looks almost identical to this one
http://vwdiesel.net/phpBB/viewtopic.php?t=10821
they are fairly easy to make if you have access to a welder and some fabrication skills. i just finished my whole exhaust last weekend including the downpipe. I bought some mandrel bent "U" bends and cut them up to form the downpipe. The part that took the most time was figuring out the best way to cut and fit the U bends. overall it turned out nice. I dont really know about cutting up a 1.9 downpipe though, personally i would make one...just because it looks "cleaner" to me.
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here is the 3" downpipe that 935 racer made for my cabby wth a 1.9 aaz and a t3 turbo
(http://i124.photobucket.com/albums/p28/giulianot/PICT2091.jpg)
All his downpipes are made of 304 ss and are back purged with argon for the best possible weld. Honestly speaking it is the nicest tig welding ive ever seen. Truly a work of art :D
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1.6TD with 2.5" - turbo back...no muffler/no nothing...:D http://s5.photobucket.com/albums/y165/80Rabbit/?action=view¤t=100_0319.flv
wow, yours sounds much quieter than mine. If I blip my throttle it sounds like a freakin 1 ton diesel truck with straight pipe. Maybe its because I have stock downpipe?
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2,5" exhaust is a bit smallish for 200hp, go for 3"
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Point your exhaust tip down to keep black smoke off the rear of the car :twisted:
I've always considered that a sort of tattoo that says "Beware!". :twisted:
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The exit port on a K14 turbo (92 Eco) is about 2.25 in. diameter. I guess I don't see the advantage of going to a larger ID downstream of the port. I run 2.25 in. I.D. pipe.
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Yep, 2,25" will be fine for stock k14. You wonīt get too much power with it :)
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So, I'm guessing 2" would be plenty with an NA? With a muffler of course.
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The exit port on a K14 turbo (92 Eco) is about 2.25 in. diameter. I guess I don't see the advantage of going to a larger ID downstream of the port. I run 2.25 in. I.D. pipe.
I am no expert, but my understanding is that tapered exhausts are used on NA engines because the velocity of the hot gases slows down as they cool off. Therefore, you will need a larger container to move the slower gases away at the same rate as the hotter gases. Whether the exhaust gases have cooled down enough on the exit port of a K14 for a taper to make any difference, I don't know. I do believe that a larger pipe will give a more pleasing tone to the sound though.
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i say if you are going to put a downpipe on it should be at least 2.5, you want to eliminate any possibility of back pressure, i would love to go 3" with my k14 if it is possible! i just have the stock downpipe and it is a little small i think, even with 2.5 exhaust pipe.
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what size is the outlet on the turbo...i know on mine the 2.5" tubing was bigger already than the outlet. is there any benefit in going even bigger than that? i know u get more flow but if the tubing is already bigger than the port...than whats the sence
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In my experience 2,5" is perfect up to 170hp. I could measure a little backpressure, not much but little. Dumped the exhaust, drove with only 3" downpipe and got 0,1 seconds off 1/4mile time with gtech :) Now I have all 3"
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i say if you are going to put a downpipe on it should be at least 2.5, you want to eliminate any possibility of back pressure[/i], i would love to go 3" with my k14 if it is possible! i just have the stock downpipe and it is a little small i think, even with 2.5 exhaust pipe.
From what I've read I don't agree with the bolded part of your statement. If you have no back pressure post turbo you will over spin the turbo or your wastegate will constantly be open. The post turbo restriction slows the rate that the exhaust gases can pass the turbine.
I believe Dave said that a 3" is too big for the K14 but I'm not positive
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this was originally posted by 935 racer in the vendors section under 3" downpipes ". The reason is that exhaust post turbine can expell quicker than it can exit the engine due to the small turbine, the downpipe can move more volume than what is capable of being pushed though the tiny turbine and the manifold pressure increases."
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this was originally posted by 935 racer in the vendors section under 3" downpipes ". The reason is that exhaust post turbine can expell quicker than it can exit the engine due to the small turbine, the downpipe can move more volume than what is capable of being pushed though the tiny turbine and the manifold pressure increases."
That was in regards to turbochargers that are too small for the application, like k14, t2, vnt15, etc. With larger sized turbo the reason you want to go with a bigger tube than the outlet of the turbo is that the exhaust gases are EXPANDING, hence the need for bigger tubing to help drop the pressure that you would see with tubing the same diameter of the turbines outlet.
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In my experience 2,5" is perfect up to 170hp. I could measure a little backpressure, not much but little. Dumped the exhaust, drove with only 3" downpipe and got 0,1 seconds off 1/4mile time with gtech :) Now I have all 3"
Do you have any pictures of your 1.7 IDI engine bay, and some dyno sheets or other details? I'd love to build a 1.7 myself.
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thanks for clearing that up for us Dave :wink:
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So what would be the recommended size of a DP/exhaust for a 1.6TD that's stock but has a K14 on it?
From what you are saying you can't have too big of a downpipe regardless of turbo size?
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So what would be the recommended size of a DP/exhaust for a 1.6TD that's stock but has a K14 on it?
From what you are saying you can't have too big of a downpipe regardless of turbo size?
No what I am saying is you can have too big of a downpipe if your turbo is too small, like a k14. If you have a larger turbo and especially if you have a really big turbo you can't have a downpipe too large.
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No what I am saying is you can have too big of a downpipe if your turbo is too small, like a k14. If you have a larger turbo and especially if you have a really big turbo you can't have a downpipe too large.
Logically I can't make sense of your answer :?
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In my experience 2,5" is perfect up to 170hp. I could measure a little backpressure, not much but little. Dumped the exhaust, drove with only 3" downpipe and got 0,1 seconds off 1/4mile time with gtech :) Now I have all 3"
Do you have any pictures of your 1.7 IDI engine bay, and some dyno sheets or other details? I'd love to build a 1.7 myself.
Didnīt find any engine bay pictures. Looks like any mk1 1,6td with Vw LT intake :lol: Dynosheet is here (http://www.kotinet.com/matti.farm/Scirocco/dynolappu.jpg), unforunately without revs and torque :( Max hp ~4700 continues straight to ~5500 and calculated max torque ~350nm@4200
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After the c-clamp shelf rusted off the downpipe on my 91 TD I modified the downpipe and from a newer TDI and bolted it to the turbo; it already had the flexpipe and is a much nicer setup than the original.
Just last week I backed into a frozen snowbank and broke the muffler clean off. I'm currently looking for a cost effective replacement as I travel 2 hours a day on the highway and the slight increase in noise is annoying.
Will the $50 generic mufflers that most parts stores carry work ok? Is there a desirable inlet/outlet size? I have replaceed most of the exhaust with 2" as it wears out.
Has anybody tried a Cherry Bomb? Low cost but I don't know how it would sound on the TD...
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Cheery bombs work fine. I used two on my wifes Quantum. 1 as resonator, the second as muffler. Ran 2.25" mandrel bent all through, including downpipe. You could really hear the T3 spool :twisted:
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I have heard that cherry bombs actually have a fair amount of back pressure, even though you wouldn't think so.
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I highly doubt that. They are basically a straight through glasspack. There is nothing in the exhausts way to cause any type of turbulence. They are highest flow next to straight pipe.
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Years ago I used to work as a parts runner for an auto parts shop. At one of my stops, they had a chart of various brands & designs of mufflers and the back pressure. While the glasspacks were low, they weren't the lowest. I don't know if the ones they had were the louvered or perforated inner core, but I can see the louvered ones creating a fair bit of turbulence inside. The one with the lowest BP was a flowmaster or dynomax or something like that. It was years and years ago and I don't remember any more.