pipe flow and torque
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Junior User
Joined: Feb 2010
Posts: 84
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From: Haiku, Hawaii
pipe flow and torque
<hr style="color: rgb(209, 209, 225); background-color: rgb(209, 209, 225);" size="1"> <!-- / icon and title --> <!-- message --> 92 f150 with the I6
--I've blocked my egr, disconnected the vacuum line--runs solid.
I cut my downpipe about 4" after the 02 sensor and had some of the guys build me a 2"y-pipe that runs into a 2.25" flowmaster 40.
So, i deleted the cats and am running straight pipe.
I haven't welded anything in yet and test drove it with just the cut down pipe. I LOST serious torque and power. I'm hoping though that tomorrow when i connect the y-pipe i'll be solid.
So, my setup is gonna require that from the double down pipe with the 02 sensor i'm connecting it to the 2' y-pipe using two 11" 2.25" pipes.
question #1--do i really need to go tot he shop and have them expand the inlet on the y-pipe to accept the 2.25" pipe OR can i just weld it together like a sleeve fitting over both the down pipe and Y...problem with that is that it is not going to be a true flow through...its going to go from 2" to 2.25 to 2" (i need the pipe extension to place the y-pipe in the right spot so it fits over the transmmission support plate). I can take it down to the shop but if i don't have to, i don't have to...just not sure what this does to the gas physics???
I'm hoping that the y-pipe and muffler give me some torque again...
question #2--i've heard of guys tuning the headers using low temp white paint....painting the pipe and watching how far back it burns...where it stopes burnin off...you end the pipe. Anybody know the deal with this trick...I'm not sure how far to run pipe to end the muffler...i was planning on running a straight pipe from the y-pipe to end at the muffler...just before the rear wheel...but i don't know if that will leave me with not enough tourque
--I've blocked my egr, disconnected the vacuum line--runs solid.
I cut my downpipe about 4" after the 02 sensor and had some of the guys build me a 2"y-pipe that runs into a 2.25" flowmaster 40.
So, i deleted the cats and am running straight pipe.
I haven't welded anything in yet and test drove it with just the cut down pipe. I LOST serious torque and power. I'm hoping though that tomorrow when i connect the y-pipe i'll be solid.
So, my setup is gonna require that from the double down pipe with the 02 sensor i'm connecting it to the 2' y-pipe using two 11" 2.25" pipes.
question #1--do i really need to go tot he shop and have them expand the inlet on the y-pipe to accept the 2.25" pipe OR can i just weld it together like a sleeve fitting over both the down pipe and Y...problem with that is that it is not going to be a true flow through...its going to go from 2" to 2.25 to 2" (i need the pipe extension to place the y-pipe in the right spot so it fits over the transmmission support plate). I can take it down to the shop but if i don't have to, i don't have to...just not sure what this does to the gas physics???
I'm hoping that the y-pipe and muffler give me some torque again...
question #2--i've heard of guys tuning the headers using low temp white paint....painting the pipe and watching how far back it burns...where it stopes burnin off...you end the pipe. Anybody know the deal with this trick...I'm not sure how far to run pipe to end the muffler...i was planning on running a straight pipe from the y-pipe to end at the muffler...just before the rear wheel...but i don't know if that will leave me with not enough tourque
Postmaster
Joined: Oct 2009
Posts: 3,432
Likes: 7
If you keep the pipe modest sized, slightly larger than stock, you can keep the torque, adding a y-pipe will help. On you motor, your headpipes should be 2", 2 1/4" is a bit large for that motor. It will probably make any torque loss issues worse. You want to use a pipe size that maintains optimum exhaust velocity at low RPM without being restrictive at higher RPM. On your motor, the two 2" pipes should have sufficient flow for a stock motor, now maybe if you were racing with it and had a modified cam or such, it might make sense to increase the size of the headpipe over stock. After the y-pipe joints together, you can merge it into a single 2 1/4" pipe, which would flow well and optimize torque.
The paint method holds some legitimate merits. If you use the method, it makes sure your pipe is long enough to support torque, if you run shorter than that, your torque will likely suffer. If you run longer than that, you will suffer a slight penalty to high end performance. However, there is not a lot of penalty to high end performance to running it longer, and there are still some gains to be had in the torque department if the run is still slightly longer. The gains beyond that point do diminish. But the torque curve basically becomes more stable with a longer run. Your penalty is really going to come from anything that will restrict flow. This means bends, especially sharp bends, baffles in a muffler, etc.
After the muffler, it is ok to run a larger pipe if you are trying to deepen the sound.
The paint method holds some legitimate merits. If you use the method, it makes sure your pipe is long enough to support torque, if you run shorter than that, your torque will likely suffer. If you run longer than that, you will suffer a slight penalty to high end performance. However, there is not a lot of penalty to high end performance to running it longer, and there are still some gains to be had in the torque department if the run is still slightly longer. The gains beyond that point do diminish. But the torque curve basically becomes more stable with a longer run. Your penalty is really going to come from anything that will restrict flow. This means bends, especially sharp bends, baffles in a muffler, etc.
After the muffler, it is ok to run a larger pipe if you are trying to deepen the sound.
Thread Starter
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Junior User
Joined: Feb 2010
Posts: 84
Likes: 1
From: Haiku, Hawaii
Solid!
Yeah, it worded well running 2.25...i went with a 2" y-pipe that expands into a 2.25...it was supposed to be 31" long then flow into a 40 series flowmaster 2.25 in and out...
The guys at the shop that did the y-pipe screwed up so bad!! This is exactly why i do all my own work...i should have just bought a damn pipe bender. Funny thing was that i talked to one of the guys that owns a machine shop and he said these guys just did this same engine...ya well, to make a long story short, i had to cut that extra 31" down by 22" so that the dual down pipe could connect to the y-pipe...they put all these crazy bends in it so it couldn't fit over / under the tranny support.
what a joke. All well...i learned do it right yourself.
I only lost a little bit in the low end torque but the midrange got a little bit better. Sounds good and performs about the same. I bet if i had another 22" on the system though it'd be better.
I never did the white paint on this one but i did feel for the heat ranges along the pipe...it's close enough to not be running as a loss...so overall i suppose i'd say it was a success.
Yeah, it worded well running 2.25...i went with a 2" y-pipe that expands into a 2.25...it was supposed to be 31" long then flow into a 40 series flowmaster 2.25 in and out...
The guys at the shop that did the y-pipe screwed up so bad!! This is exactly why i do all my own work...i should have just bought a damn pipe bender. Funny thing was that i talked to one of the guys that owns a machine shop and he said these guys just did this same engine...ya well, to make a long story short, i had to cut that extra 31" down by 22" so that the dual down pipe could connect to the y-pipe...they put all these crazy bends in it so it couldn't fit over / under the tranny support.
what a joke. All well...i learned do it right yourself.
I only lost a little bit in the low end torque but the midrange got a little bit better. Sounds good and performs about the same. I bet if i had another 22" on the system though it'd be better.
I never did the white paint on this one but i did feel for the heat ranges along the pipe...it's close enough to not be running as a loss...so overall i suppose i'd say it was a success.
