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Discussion Starter · #1 ·
got 3" downpipe from fwdperformance
got a TII 2.5" swingvalve

out of the car, with the swingvalve and downpipe on the bench, they BARELY fit together and seal..the downpipe donut is just too big

in the car, i tried installing the downpipe, and the angle it needs to be makes it so there is no way its going to seal, the swingvalve will just cut into the soft donut

i dont want ANY exhaust leaks because my wideband will be inaccurate

anyone else have this issue?
 

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bolted up to a 3in sv just fine did it today.

but i held my extra 3in dougnut up against my 2.5 sv. looks like it would cut into the sides a little, but i think thats why its a cushion, with the bolts tight and spring tension tight, it will wear a pattern into the dougnut. i think if you put it together, then run it, get it hot then retorque the DP bolts should be fine. someone else chime in here, ive never done it.

you could port the end of it a little, do a search as well.
 

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how are your motor mounts? I have an MP side, Poly front and semi solid tranny mount. I'm running a TU downpipe which I think has a pretty big donut. I've never seen the FWD piece but I think they're the same donut, definately bigger than the machined stainless steel donut Rick D used to sell. Anyway since I have stiff mounts I just tightened it up and it doesn't leak. I'm gonna have to get a new donut when I put the 3" SV on because it's dented pretty good though. I'd say make sure your mounts are good and go ahead and squish it on. If not you might want to upgrade to TU's 3" swingvalve which has a much larger opening made to fit tha large donut.
 

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Now TU is only selling the 3" SV as a package with a 3" DP. :bang head
that`s the main reason I haven`t ordered one yet.I wish he would just sell the SV along with the 3`` doughnut and 3-4`` of down pipe .I quess I could cut it but I hate to waste money on something I won`t use.What was the normal price on the 3`` SV? Is his 3`` downpipe SS?
 

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so what....i cant use a 2.5 swing valve and then use a 3 inch downpipe?
Didn't you read?

bolted up to a 3in sv just fine did it today.

but i held my extra 3in dougnut up against my 2.5 sv. looks like it would cut into the sides a little, but i think thats why its a cushion, with the bolts tight and spring tension tight, it will wear a pattern into the dougnut. i think if you put it together, then run it, get it hot then retorque the DP bolts should be fine. someone else chime in here, ive never done it.

you could port the end of it a little, do a search as well.
 

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It won't fit and you will have a nice exhaust leak. Take it to a machine shop w/the 3 inch donut and get it machined out. Cost ya $25+-


Pic attached to get an idea of what it looks like (it's a VNT setup in case you are wondering)

 

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bolted up to a 3in sv just fine did it today.
but that wasnt the question ; we know a 3" SV will bolt to a 3" DP

but i held my extra 3in dougnut up against my 2.5 sv. looks like it would cut into the sides a little, but i think thats why its a cushion, with the bolts tight and spring tension tight, it will wear a pattern into the dougnut. i think if you put it together, then run it, get it hot then retorque the DP bolts should be fine. someone else chime in here, ive never done it.
well firstly, you cant really 'retorque' the flange bolts - they're spring loaded / constant clamp / 'bottom out' design

and I have (also) held my 3" DP/donut up to my 2.5" SV and it looks to me like theres NO WAY it won't leak...

has anyone ACTUALLY run a 3"DP/donut on a 2.5" SV (w/o leaks) ? ?
 

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My low emission numbers suggest I don't have a leak with my 2.5inch swingvalve and 3 inch downpipe.
Ya wanna hear something funny?

Whenever I would have an old beater that wouldn't pass the IM240 test here, I would go home, drill some holes in the exhaust under the car, and go get it passed the same day:D
 

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i had a 2.5in donut on 2.5 pipe flared to fit the 3 inch DP and thats how i had it connected on one of my cars for a long time
 

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i had a 2.5in donut on 2.5 pipe flared to fit the 3 inch DP and thats how i had it connected on one of my cars for a long time
That makes sense.

I thought I remembered something like that on TU's website at one time. Either they sold 2 different ones or modify something like that. I definitely got the impression you weren't supposed to use the 3" donut on the 2.5" SV......

edit: like they had a special donut for the 2.5" SV and 3" DP
 

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hows that work?:confused: you'd get a dilluted exhaust sample if you did that.
Well there's some ******* engineering involved. I didn't just drill crazy random holes in the pipes - if the car was too loud or if something seemed fishy they might roll a mirror under there. I drilled little holes 1/4" or 3/8". Holes added towards the engine would draw O2 into the hot exhaust to drop the HC as then combustion completed in the pipe. Holes added back after the axle would dilute everything a bit to drop HC, CO, and NOx across the board. It was a way to nudge a tired car onto the good side of the limits. It wont pass a V8 with 3 dead misses:p. I would fix something like that - I just felt that if my cars idled fine, drove fine, and got decent mileage, they were fine.

Another thing to consider is that these weren't mechanics nor did they work for the state. WI built test facilities that were run by an independent testing company. The guys and gals doing the tests were employed by the contracting company and the only real requirements to be hired were that you were 18, licensed, and could drive stick.
I guess when my school handed me a cert that said 'Emissions' on it in bold letters I didn't like the idea of some $10/hr smog-jockey standing between me and my license plates. :p
 
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