I am still running the stock turbo elbow and 3.5" downpipe. My exhaust temps are well within check, and see no reason to swap it out for a larger one for this reason. So I'm wondering. Will running a 4in. elbow and downpipe do anything for me?

I do have what seems like a noticable popping sound in the exhaust under severe loading while at WOT. At 1st thought it was a dropped valve (thank heaven it wasn't!!!). So I was thinking it maybe too much backpressure in the exhuast causing some weird things in the turbo. BUt someone told me that it was normal and was simply the wastegate opening and shutting.

What is you alls' take on this???

 

Most aftermarket exhausts have more gentler mandrel bends vs the stocker, so your EGTs are reduced

 

If your whole exhaust system is stock is stock 4inch turbo back will increase by 5 to 10 hp and lower egt's and back pressure.

 

I already replaced the asthmatic muffler and all of the 3.5" pipe, except for the DP. so I'm guessing going to a 4" DP might be good for another couple HP but probably not noticeable. That's what happened with my 97. I put on a 4" muffler and tailpipe and did the power mods before building a 4" DP. I couldn't feel any difference with the 4" DP and that was going from 3" to 4". I might be mistaken but the 4" DP is at the very bottom of my list. Craig

 

As you can see, I have a 4" Magnaflow from downpipe back. I'm just wondering if the downpipe would reduce backpressures?

 

i think it's not really a hp adder but a good supporting mod for when you choose to go for more hp...it's main attribute is the lowering of egt's.

 

I agree with WUNDERWOOD, "Most aftermarket exhausts have more gentler mandrel bends vs the stocker, so your EGTs are reduced" If you leave the stock one on your restricting the air flow for about 30"/40". I'm sure some believe it's trivial and to a degree it is, but the sooner you can get the old air out the quicker you can get the fresh air in and that makes power.

 

I swapped mine at about 3k to the Banks full 4 inch system.From the GET GO a easy 1 plus mpg increase according to overhead back then.

 

If you're having high egt's, it will probably help cool you down. If you look at the volume of 3.5" exhaust compared to 4", you can see how much of a difference there really is. Even though it's only the downpipe, it is a restriction. 3.5" has only 76% of the volume of a 4" downpipe. To me, that's a restriction. If I took away almost 25% of your breathing capabilities, you'd notice, wouldn't you?

 

But that little bit of pipe is far less than 25% of the entire air system. Going from a 3'' to a 4"" DP on my 97 made no mph increase at all on one of the hardest pulls around, Mt. Vernon Canyon, aka the Hogback. It also depends on the HP. The old 12v hotrodders like Joe D. saw no significant increase on the dyno til over 400 hp. That's probably why it hasn't helped mine yet! Craig

 

If it makes a difference it wont be much at all.

 

well for the restriction stand point even thought you changed your exhaust system over to 4" pipe except the DP you still only have a 3.5" exhaust system because that is your choke point. think about it this way if you take a garden hose and squeeze any where along the hose it restricts the amount of water coming out and causes more back pressure.

 

It wouldn't matter if it was shorter than the downpipe. A restriction is a restriction. I do agree that it doesn't matter on the horsepower end of things. But were not talking about 300 or 400 horsepower here. Streetsmoker runs 12's. The only issue is going to be egts and if the restriction is causing them to be too high...

 

I bought a MBRP 4", turbo back , alum. with muffler , I looked at the down pipe saw the reduced 4" to 3 1/2 " , and asked myself about changing the elbow , so that I could put a true 4" down pipe on , my expected HPs may get to 350-400 , daily driver , RV hauler , mnts.
I thought if I open the elbow & down pipe , would that keep the turbo from spooling up as soon ? [ less restriction , forcing exhaust into the turbine ? ]
I may consider moding the WHX1 or replacing , just some things to think about , and ??? to get answers for ???

 

There again, my egt's have rarely been above 1450* even at the track. So my main concern is to open up the exhaust and maybe reduce backpressure. Which JFaughn has a good qustion: "what effect does a bigger downpipe have on turbo spool?"