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Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community - FT86CLUB (https://www.ft86club.com/forums/index.php)
-   Engine, Exhaust, Transmission (https://www.ft86club.com/forums/forumdisplay.php?f=8)
-   -   Anyone figured out yet why some headers apparently get rid of the 'torque dip'? (https://www.ft86club.com/forums/showthread.php?t=34982)

ft_sjo 04-28-2013 02:59 AM
Anyone figured out yet why some headers apparently get rid of the 'torque dip'?
 
So there's a few exhaust manifolds/headers out now which supposedly get rid of the torque dip.

One which come to mind are Nameless, FA20Club and Borla UEL.

So the first two above look reasonably similar, but the Borla is completely different. So it's not safe to assume the extra length of the first two is causing the increase in torque, as the Borla doesn't have that.

Discuss.

Xdragonxb0i 04-28-2013 03:16 AM
I think all headers take it away. The OEM headers are the problem

Hawaiian 04-28-2013 03:31 AM
Quote:
Originally Posted by ft_sjo (Post 896436)
So there's a few exhaust manifolds/headers out now which supposedly get rid of the torque dip.

One which come to mind are Nameless, FA20Club and Borla UEL.

So the first two above look reasonably similar, but the Borla is completely different. So it's not safe to assume the extra length of the first two is causing the increase in torque, as the Borla doesn't have that.

Discuss.
You forgot the P&L, but that's beside the point. The reason those 3 do so well is primarily the fact that they are long tube headers. They specifically increase low end torque, but you still need a tune to take full advantage of the headers and clear up the dip.

The stock system is built for comfort and economy. The average joe wants a quiet, economical vehicle. People who mod are willing to sacrifice some of that.

ft_sjo 04-28-2013 03:36 AM
How is the Borla manifold a 'long tube header' in comparison to something like the JDL one, which doesn't flatten out the torque dip in a similar fashion?

Hawaiian 04-28-2013 03:55 AM
Quote:
Originally Posted by ft_sjo (Post 896485)
How is the Borla manifold a 'long tube header' in comparison to something like the JDL one, which doesn't flatten out the torque dip in a similar fashion?
I've yet to see a JDL header dyno with a tune. The one in their thread is un-tuned, except for the goofy "lateral G force" graph.

ft_sjo 04-28-2013 04:15 AM
So do you expect pretty much any of the 4-1 aftermarket manifolds (excluding perhaps the abortions from people like HKS), will remove the torque dip with a tune?

Hawaiian 04-28-2013 04:39 AM
Quote:
Originally Posted by ft_sjo (Post 896533)
So do you expect pretty much any of the 4-1 aftermarket manifolds (excluding perhaps the abortions from people like HKS), will remove the torque dip with a tune?
I think most will have a positive effect on the dip with a tune. If you don't want to take a guess, just wait until the numbers start leaking out from third parties. Product manufacturers have one goal, to sell product. Third party dynos will back up, or disprove their claims.

Hawk77FT 04-28-2013 06:42 AM
For all of you who want the dip gone here is an explanation from someone who knows a thing or two about tuning/engines:

"As posted somewhere previously, the “torque dip” is a result of engine internal design not tuning. The only thing tuning can do is move the dip somewhere else.

There’s a long discussion here, but the best way to think of it is to look at the torque curve… if you permit me some artistic license, the torque curve looks like two hills with a valley at either end and another in the center. Each of the hills is a cam profile… low speed on the left and high speed on the right. The peak of each hill is the maximum breathing that cam can provide… either side of the peak the cam doesn’t breath as well and that will only change by re-profiling the cam's lift and/or duration - you can only change the hill shape by re-profiling the cam. Changing the VVTi timing just moves the peak left or right... the problem is if you move, for example, the high speed peak left to fill in the valley between the two peaks, the valley to the right of the high speed peak gets deeper very quickly and the engine falls on it's face."

Therefore, there is no tune out there that removes the dip..yes it might either reduce it or move it elsewhere, but you cant completely remove it without upgrading the cams. I am sure that in the following months/years we will see some modified cams ready to go for our cars, but until then we will have to deal with it.

Calum 04-28-2013 08:19 AM
Quote:
Originally Posted by Hawk77FT (Post 896626)
For all of you who want the dip gone here is an explanation from someone who knows a thing or two about tuning/engines:

"As posted somewhere previously, the “torque dip” is a result of engine internal design not tuning. The only thing tuning can do is move the dip somewhere else.

There’s a long discussion here, but the best way to think of it is to look at the torque curve… if you permit me some artistic license, the torque curve looks like two hills with a valley at either end and another in the center. Each of the hills is a cam profile… low speed on the left and high speed on the right. The peak of each hill is the maximum breathing that cam can provide… either side of the peak the cam doesn’t breath as well and that will only change by re-profiling the cam's lift and/or duration - you can only change the hill shape by re-profiling the cam. Changing the VVTi timing just moves the peak left or right... the problem is if you move, for example, the high speed peak left to fill in the valley between the two peaks, the valley to the right of the high speed peak gets deeper very quickly and the engine falls on it's face."

Therefore, there is no tune out there that removes the dip..yes it might either reduce it or move it elsewhere, but you cant completely remove it without upgrading the cams. I am sure that in the following months/years we will see some modified cams ready to go for our cars, but until then we will have to deal with it.
This engine has variable cam phasing with only one cam profile.

mad_sb 04-28-2013 10:25 AM
Quote:
Originally Posted by Hawk77FT (Post 896626)
For all of you who want the dip gone here is an explanation from someone who knows a thing or two about tuning/engines:

"As posted somewhere previously, the “torque dip” is a result of engine internal design not tuning. The only thing tuning can do is move the dip somewhere else.

There’s a long discussion here, but the best way to think of it is to look at the torque curve… if you permit me some artistic license, the torque curve looks like two hills with a valley at either end and another in the center. Each of the hills is a cam profile… low speed on the left and high speed on the right. The peak of each hill is the maximum breathing that cam can provide… either side of the peak the cam doesn’t breath as well and that will only change by re-profiling the cam's lift and/or duration - you can only change the hill shape by re-profiling the cam. Changing the VVTi timing just moves the peak left or right... the problem is if you move, for example, the high speed peak left to fill in the valley between the two peaks, the valley to the right of the high speed peak gets deeper very quickly and the engine falls on it's face."

Therefore, there is no tune out there that removes the dip..yes it might either reduce it or move it elsewhere, but you cant completely remove it without upgrading the cams. I am sure that in the following months/years we will see some modified cams ready to go for our cars, but until then we will have to deal with it.
While i agree with that statement to some extent (tune alone will not remove the dip, but i don't think the dip is to do with the cams at all) the question was about why the aftermarket headers are able to remove the dip.

I assume the real answer is way over my head and has to do with harmonics and wave theory. The way I imagine it (note i am not saying this is the case, just the way my tiny brain tries to wrap around it) the design of the factory header creates a sort of standing wave in the exhaust at the "dip" rpm range... thus creating excessive back pressure which kills scavenging and causes the air flow to drop significantly in the dip (as i have logged over and over again).

If my magic wave unicorn theory is correct then a change in primary length, primary diameter, collector design etc COULD change or remove the restriction. As we have seen, not all of them seem to do that, but a few certainly do.

FirestormFRS 04-28-2013 10:55 AM
Removal of the cat....more than anything

Hawaiian 04-28-2013 11:31 AM
Quote:
Originally Posted by Hawk77FT (Post 896626)
For all of you who want the dip gone here is an explanation from someone who knows a thing or two about tuning/engines:

"As posted somewhere previously, the “torque dip” is a result of engine internal design not tuning. The only thing tuning can do is move the dip somewhere else.

There’s a long discussion here, but the best way to think of it is to look at the torque curve… if you permit me some artistic license, the torque curve looks like two hills with a valley at either end and another in the center. Each of the hills is a cam profile… low speed on the left and high speed on the right. The peak of each hill is the maximum breathing that cam can provide… either side of the peak the cam doesn’t breath as well and that will only change by re-profiling the cam's lift and/or duration - you can only change the hill shape by re-profiling the cam. Changing the VVTi timing just moves the peak left or right... the problem is if you move, for example, the high speed peak left to fill in the valley between the two peaks, the valley to the right of the high speed peak gets deeper very quickly and the engine falls on it's face."

Therefore, there is no tune out there that removes the dip..yes it might either reduce it or move it elsewhere, but you cant completely remove it without upgrading the cams. I am sure that in the following months/years we will see some modified cams ready to go for our cars, but until then we will have to deal with it.
We will have to agree to disagree. Here is a dyno of my car, with stock cams... no dip.
https://s3.amazonaws.com/pandlmotors...dyno-graph.jpg

Quote:
Originally Posted by FirestormFRS (Post 896772)
Removal of the cat....more than anything
The red line is with a cat. It's actually flatter than the blue line (with cat).

wparsons 04-28-2013 03:33 PM
Quote:
Originally Posted by Hawk77FT (Post 896626)
For all of you who want the dip gone here is an explanation from someone who knows a thing or two about tuning/engines:

"As posted somewhere previously, the “torque dip” is a result of engine internal design not tuning. The only thing tuning can do is move the dip somewhere else.

There’s a long discussion here, but the best way to think of it is to look at the torque curve… if you permit me some artistic license, the torque curve looks like two hills with a valley at either end and another in the center. Each of the hills is a cam profile… low speed on the left and high speed on the right. The peak of each hill is the maximum breathing that cam can provide… either side of the peak the cam doesn’t breath as well and that will only change by re-profiling the cam's lift and/or duration - you can only change the hill shape by re-profiling the cam. Changing the VVTi timing just moves the peak left or right... the problem is if you move, for example, the high speed peak left to fill in the valley between the two peaks, the valley to the right of the high speed peak gets deeper very quickly and the engine falls on it's face."

Therefore, there is no tune out there that removes the dip..yes it might either reduce it or move it elsewhere, but you cant completely remove it without upgrading the cams. I am sure that in the following months/years we will see some modified cams ready to go for our cars, but until then we will have to deal with it.
Unfortunately, that's not correct on these engines. They only have a single cam profile, it's not like VVTiL in a 2ZZ that has a second cam profile.

As for the reason not all headers behave the same, it all comes down to flow and resonance in the header. If you look at the length of the primaries in the nameless long tube they're quite longer than most of the other headers out there. There's simply no room for a cat in the header with the longer primaries, so you need a cat in over pipe if you need one. Diameters, steps, length between steps, etc all play a part as well.

4-2-1 headers also do better with low end torque than 4-1 headers, but typically at the cost of a little bit of power up top.

FirestormFRS 04-28-2013 05:52 PM
Quote:
Originally Posted by Hawaiian (Post 896823)
We will have to agree to disagree. Here is a dyno of my car, with stock cams... no dip.
https://s3.amazonaws.com/pandlmotors...dyno-graph.jpg



The red line is with a cat. It's actually flatter than the blue line (with cat).
The factory cat or high flow aftermarket cat?


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