How can a 2.5" or 3" dp bolt on too a stock cat????????
'99 GST http://www.geocities.com/mospeed9844
Akimoto Air Fitler
GReddy Intercooler Piping
GReddy Profec B
GReddy Boost and EGT Gauge
Autometer Air/Fuel Meter
Front and Rear Strut Bars
they don't all bolt up, well let me refrase that...a true 3" dp will not bolt up. but most of the dp's on the market "neck down" to 2.25"-2.0" so they can bolt to the stock cat which makes it pointless to buy the thing in the first place. why do you want to bolt it to the stock cat?? what did you buy the dp for if your gonna bolt it to the stock cat, it wont do much if your running the stock cat. so either get a true 3" hi-flow cat or just get rid of the cat all together(which is what i'd do). also have the flange cut off the dp where it meets the cat and have a muffler shop put a 3" piece of pipe in there with a flange so you can bolt it to the true 3" exhaust you have or are gonna get. chances are that if you have an exhaust already and it is bolted to the stock cat then it probably necks down to 2.25"-2.0" so that it can bolt to the stock cat making the hp increase very minimal. this is a true 3" system where it remains 3" from the turbo to the tip.
even if you have emissions they only test what every 2 years or so. then you put your stock exhaust back on and pass the test then hurry home and put your 3" system back on before you encounter a race
not me.....no emissions down here in york/adams county pa. hell were allowed to go to sunoco and pump cam-2(leaded race gas) right into the tank. ofcourse you need a funnel because the nozzel on the pump is to big to fit into the hole on the filler neck of the car. hey greenstreak, your welcome to use my address to register your car in pa
thx for your help.
the situation I am in is that I have a HKS turbo Cat-Back that bolts straight up to the stock CAT. I did not realize what I was doing until I woke up this morning and starting thinking about the whole deal(I have had the CAT-back for 4 months now). I want a downpipe, but since the HKS necks down to 2" or so, the downpipe will do nothing, because exhaust(or any other matter) is governed by the smallest diameter in the pipe. So now I want to get rid of my Cat-Back and get a 2.5" system.
Don't just toss you cat back. You can cut off the necked down portion and have a muffler shop weld on an extention pipe(same diameter as cat-back) with flanges to bolt up to a hi flow cat. Then the downpipe will mate with the cat.
Well, I guess I can't speak for other aftermarket DPs and cats. But the DP I purchased from Buschur fit just fine on the stock cat and it is 2.5" all the way. If you ever get under your car, and look at your stock cat flanges, they are slotted, so it would fit any reasonable size DP. My 2.5" DP was hooked up just fine... was it a perfect fit? No. Cause I still had the stock gasket and cat on still. So I still had a major restriction. BUT, it was able to stay on until I got my lazy ass to put the hi-flo cat on there. So now the 2.5" DP and 2.5" cat fit perfectly... then it's connected to a 3" cat back (which comes down to 2.5" to connect to the cat).
p.s I do not know anything about the GReedy or HK$ parts. This is all based on BR products. Truthfully, if I had to do it all over again, I'd go RRE.
any downpipe will bolt up to the stock cat as long as you specify that you want it to mount to the stock cat when you order it. Buschur, Extreme, and The dsm shop can make the downpipes to what ever you want. If you get a 2.5 it is the same size flange. If you get a 3 inch downpipe it will have to be necked down to work with the stock cat. Honestly the best thing that you could do is get yourself a 3 inch highflow or 2.5 inch highflow cat. Or a race pipe. You will see alot of power gain buy remocing the stock cat. It is way to restrictive. You want the lest back pressure that you can get.
so here's my situation.. i have a hks 3" super dragger cat back.. i am getting a dp with ing the next few weeks.. my uncle owns a weld shop. what dp do i need so i will be TRUE 3" all the way back.. i realize i need to cut the hks before the resonator to lose the tapered part. ps, no inspections here...ooops i mean the car is only for off track use.. so no worries about anything being permanent
J. Hunter Allred
'95 GS-T free mods, K&N, 3" HKS Superdragger, ACT2600, lightened flywheel, and otherthings that escape me at the moment. T-25 handicapped though. As you can see its a work in progress. Figure if i buy it i should buy it once
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