Unequal exhaust routing effects?

Last question today. I promise. 

My X pipe is the straight in and straight out variety. It’s is an X pipe, just not in the traditional “X” shape. So I’m thinking he best way to do this is to run the pipe off the passenger header side under the driveshaft/transmission u joint area, over to the driver’s side and connect in both pipes to the X, then out. It’s the 1uz celica, and 2.5” pipe, so packaging is limited. It’s not even lowered, and I’ll only have about 4” ground clearance. Not ideal. I’m seeing a few online setups like this, so I’m thinking I’m just paranoid here. 

Why not go to a slightly bigger single pipe, simplify everything, have less weight, and have to buy less material? Other than that thought, if I'm reading your post right I don't see a problem with that plan. Seems to be the common solution to V8 swapping BMWs.

In reply to Daylan C :

Ok. My original goal was side exits in front of the rear tires. The x pipe is recommended almost universally along with the 2.5”. Placing the X right under the u joint would require more bends, more time, and still require more piping, if not more. I could go single exit to the back again, that might actually be simple, since the chassis is setup for a single run of exhaust from a four cylinder. 

In reply to Trackmouse :

This is pretty much the picture I got reading your post. I think it made sense on E36s because the 6 cylinder cars already had dual exhaust routed like that, just coming off of one bank.

In reply to Daylan C :

Yeah but i ain’t got that kinda clearance under the transmission. The car has about 2” to go for lowering it. So I need to hug the transmission and cross over at the tail of the trans for room and clearance. 

So, I have a V8 with duals all the way back.  BUT the driver's side header pipes are a passenger-side unit mounted so it dumps to the front, routed through 2.5" pipe around the FRONT of the motor, and then back to the firewall under the passenger side header pipes. 

Chassis was an inline 6 setup so it's pretty hard to go out the firewall on the driver's side.  That photo above is a generation 2 E36, and you will see flex high pressure fuel line running right next to the exhaust on the driver's side at the firewall (the canister is the fuel filter).  AND they have taken off the chassis X-brace that we all bolt onto the subframe rails under the motor and oilpan, probably because they can't clear the pipes.

It gets better:  I put a dual in/dual out X-flow muffler where the cats used to be, and then ran straight pipes to the rear bumper.

It works great.  Did I leave something on the table?  Maybe, who knows.  Sometimes with swaps, I just do the best you can and forget it.

I saw an episode of Engine Masters.  They had done a motor swap and hammered the header pipes to get clearance for something, probably the steering.  Everybody on the internet gave them grief, so they dynoed the motor with a fresh header and then started hammering on it and re-dynoing it.  HP and TQ went up, not down.

In reply to JBasham :

Yeah, that episode really changed how I view exhaust work. I think what I’ll do is cross over at the trans tail, there is literally NO ROOM in the engine bay for antics like you mentioned. This was going to be a rallycross car, but I’ll have to lift it even more to get some clearance now. 

What about running a crossover under the bellhousing?  On a lot of setups you can fit one there and still not hang lower than the lowest point of the oil or trans pan.  Under the trans tail works too though.  

At the horsepower levels a 1UZ makes, I doubt a difference in exhaust lengths is really going to make much of a difference. Maybe if you had some screaming 750hp big block Chevy, it might bother. But at the 250-290hp level, it probably won't really care. If you're really lacking for clearance, perhaps use oval pipe where it has to pass under things. Once again, at that power level, I doubt it'd bother

side by side tests don't really show that an X does much better than a properly placed H.  At these horsepower levels, you won't notice a difference at all.  In fact you might not notice anything different if you avoid the crossover completely.

The crossover is only there to equalize pulses.  It doesn't need to be full size, it can be 1.5" tubing if you want.  It also only works if you put it in the right place.  It has to go where the pressure waves hit each other and cause the highest SPL inside the tube.  If you put it behind or in front of that point, you're not really gaining much.

I do like the way it smooths out the sound, but as a power-adder on a car with such little ground clearance, I say skip it.  So many people add one in their system and it doesn't make any power because it only works if you need it AND if its in the right spot.

In reply to Curtis :

Yeah I’m doing it for sound. The x has always sounded better to me. And there is a video of a sc400 with (supposedly) an X and it sound baller. So naturally I need that in my life. Apparently, the 1uz wise men say that if you don’t have a cross over or go into one pipe it ends up sounding like two four cylinders. 

I just took the celica for an open header joy ride. 

I take it zoomies are out of the question?

I actually completely understand going through the trouble of an x pipe just for sound. My GTA is getting a 3" single because I'm lazy and the car came with shorty headers for an SBC and the y-pipe, with the 305 I'm expecting it to sound like every beater GMT400 in town.

Trackmouse said:

In reply to Curtis :

Yeah I’m doing it for sound. The x has always sounded better to me. And there is a video of a sc400 with (supposedly) an X and it sound baller. So naturally I need that in my life. 

Totally respect that.  Carry on :) 

thatsnowinnebago said:

I take it zoomies are out of the question?

That actually was plan A)! Once I stared at the bottom of the car long enough and looked at ground clearance on the passenger side, I started resorting to plan B) and C)... I suppose I could route everything into one pipe on the right, and have that exit as 4-8 glorious zoomies. Man that’d be different.