I was wondering why there hasn't been more people complaining of a horrible exhaust design. For the 4.7L V8 - I'm assuming all 4th Gen(2003-2009) have the same design flaw. Part # differ for 2003-2004 and 2005-2009, but the oem crushed merge seems the same. If you have a 2005 verify if this is as bad for you guys...

I just recently replaced my Y-pipe with a Magnaflow direct bolt in replacement. It even comes with a catalytic warranty (5 year 50K miles/2 year 25K miles) if you want one of those. I didn't have any CEL requiring a need to swap out Cats, but wish I had swapped this much earlier.

Here is what the OEM Y-pipe merge looks like:


Here is what the replacement looks like:


Here's a side by side comparison:
http://i110.photobucket.com/albums/n...psfakzeus8.jpg


Out of the box, Exhaust note is not really any different. I expected it to be a little louder, but it isn't. Its unnoticeable. From a driveability perspective, the acceleration feels much smoother. I haven't actually dyno tested it - but that is what it felt like to me.

I believe part of the cause for the OEM headers cracking is due to the excessive back pressure created by this merge - that and the OEM header design really couldn't be much worse than it is.

I wish I had done it sooner.

NOTE: During installation, I did need 2 flange nuts - fortunately I had a bunch on had already. I believe they were M10 with a 14mm hexhead.

Interesting. You're the first I've seen to write something about this. Did you get their OEM or Standard cat? I'm pretty sure my 2005 has something similar to that design.

I mean, these aren't exactly hot rods... But it's not like swapping out the y-pipe is gonna net you 50hp.

I mean I suppose if it bothered you that much you could do before and after dyno test and volumetric efficiency tests. But what you maybe gain 5hp?

5HP is 5HP, and may benefit throttle response and driveability. However, how much did that part cost? $500 = $100/hp. Not a great deal.

OP, what was the part number and cost? Thanks.

It sure looks nice!

I have a 1987 Volvo wagon with a 4 cylinder that once had the exhaust pipe come loose at the muffler. As a result, the engine would barely produce enough power to get up my driveway. For some reason, that engine requires back pressure to run properly! So, I am assuming that Toyota engineers designed their engines to run most efficiently on the stock header. That is not to say the design can't be improved!

The new part does look better though. And nice and shiny!

Where did you buy that from?

I'm guessing, but it looks like a Magnaflow 93655. $221.

Not sure it would do much of anything and while 5hp is 5hp, how much troque gain do you get, maybe 2ft/lbs at the top end? The headers, cats, intake runner, intake, and valves are also part of the breathing equation. I'm not saying it doesn't help. But we're not talking about a blueprinted and tuned engine with equal length scavenging exhuast headers and non-cat exhuast with a ported intake and low restriction intake.

Again, it's not a great design; but I doubt it's killing the engine on the V8. Volumetric Efficency testing dyno testing will probably show that.

The basic 2 into 1 is the real problem. Should have been a true dual all the way back.

Nice find.. the whole manifold problem is still a big issue. On top of that the low down pipe crossover with a terrible Y-pipe design. The whole header needs a redesign and that needed to be looked at after we find a decent manifold first. the V6's have a catless y pipe and the v8 has been forgotten.

I had a plan to run run tundra headers with o2 sims. Just haven't had the time to get it done and probably not gonna get to it unless my manifold cracks wide open.

Thanks for posting.

Not true. A 2 into one design will yield more TQ. Ive been in the performance game for a long time. with lots of dyno tests to back up. Exhaust scavenging is much better with a properly tuned 2 into 1 design. The problem with the 4runner setup is the size of the pipe and restrictions.

That is correct if you're talking about header primaries, but you're wrong with respect to a 2 into 1 main exhaust pipe. And I've been in the "performance game" a long time too, so let's see those back to back dyno sheets showing that a single exhaust pipe yields more torque than true duals - regardless of the size.

Yeah. I don't believe in the 2 all the way back. But, just like any tuner you just need to build it and see if it makes more power. We just need somebody that can weld to make a set up.

There is no way to make a bolt on y pipe without removing the rear cat. There's not much room for a decent 2-1. That's why they used the lame 2-1 in the first place.

Hot rods, no. But a 4.7L motor should be making more than 280HP. I'm confident with headers, Y-pipe, and tune (IF there was something out there) that these would be far more fun and efficient. I don't plan to dyno - since there are really no tuning options. But i would guess 5-10 HP. More importantly, just smoother feel during acceleration. And I used the

Yes, i went with the 93655 Retail is $221 - i paid less and can get you one for less if you want.

There are 2 parts for 2003-2004
$221 retail = 93655 - not for CARB emissions vehicles
$300 retail = 49696 - for CARB emission vehicles - has higher precious metal quantities

Correct - but, i can get it for less

When I scrounge up the money for headers I'm having a shop install them and build me an exhaust. It's going to be true duals with an x-pipe, undecided on mufflers as of yet but something high flowing and on the louder side. lol, I also won't be running any Catalytic converters which will require me buying the harness from URD so it doesn't throw a code. Stock is very restrictive.
There is a tuner you can buy from URD but it isn't user friendly like something that is plug and play on the big 3. Takes some user knowledge and a dyno to get everything right. You MIGHT gain 50hp with a tune, exhaust and intake. Would take a good, knowledgeable tuner and proper setup on everything though. Now, add a supercharger or turbocharger into that and you could really rock out some numbers!