Anyone figured out yet why some headers apparently get rid of the 'torque dip'?

[Xdragonxb0i]

nameless dyno graph looks okay initially, but you see at 6500rpm the torque and hp start to dip. I say this due more to tuning then the header itself.

I made post about tge p&l header being loud, i contract my statements, it louder then stock for sure but pretty tame when DD. At 75mph , the noise start to bother me.

[Kodename47]

Originally Posted by TOTO_86

In my opinion, the reason for the torque dip is because the computer is on the motor. I've heard from a Toyota technician that when a car has it's computer on the engine it can cause problems. He suggest to buy a heat shield for it. This is the first time I've read that headers are helping the problem out.

Right, so having the ECU exposed to heat means it doesn't work correctly for 1k RPM of the rev range!? Its nothing to do with that

@Xdragonxb0i the reason it starts to lose power after 6.5k is that's where the limitations of the cams are. It was also posted earlier that header design places peak torque around a set area, which in Nameless' case is where I the original dip is (its quite obvious). You could design a header for more top end grunt but I doubt that it would improve on the lower dip.

[mad_sb]

Originally Posted by TOTO_86

In my opinion, the reason for the torque dip is because the computer is on the motor. I've heard from a Toyota technician that when a car has it's computer on the engine it can cause problems. He suggest to buy a heat shield for it. This is the first time I've read that headers are helping the problem out.

absolutely incorrect

[ft_sjo]

Originally Posted by mad_sb

absolutely incorrect

.. but hilarious!

[arghx7]

Originally Posted by Hawaiian

We will have to agree to disagree. Here is a dyno of my car, with stock cams... no dip.

Have you ever used the Dynojet WinPEP 7 software? That's a visual trick of the scaling. The torque goes down and then up between 4750 and 6500--hence, a dip. Or is it a torque "hump" at 6500? It's all in the eye of the beholder.

What about the blue line, between 3250 and 4250? That's a dip too. Or is it a "hump" at 4250? If you could provide the .drf file for the WinPEP7 dyno run, I could make your dip get bigger and smaller in about 5 minutes. You see this all the time on the WRX forums (NASIOC) when a tuner posts how "smooth" the power and torque curve are, by stretching it out like that.

I realize that this sounds like sour grapes, s**tting in your cornflakes, etc. Engines with cam phasing typically have "dips" or "humps", unless you kill the scavenging effects. It's physics. You can move it around a bit, maybe change the shape some. It's unavoidable though.

[bdub85]

Originally Posted by TOTO_86

In my opinion, the reason for the torque dip is because the computer is on the motor. I've heard from a Toyota technician that when a car has it's computer on the engine it can cause problems. He suggest to buy a heat shield for it. This is the first time I've read that headers are helping the problem out.

That makes absolutely no sense at all. A computer either works or it doesn't. If a computer overheated, it would just stop working all together. There is no middle ground with computers. Also, I'm 100% positive Toyota engineers placed the computer in a place which wouldn't exceed the maximum operating temp for the computer.

[industrial]

Originally Posted by arghx7

Have you ever used the Dynojet WinPEP 7 software? That's a visual trick of the scaling. The torque goes down and then up between 4750 and 6500--hence, a dip. Or is it a torque "hump" at 6500? It's all in the eye of the beholder.

What about the blue line, between 3250 and 4250? That's a dip too. Or is it a "hump" at 4250? If you could provide the .drf file for the WinPEP7 dyno run, I could make your dip get bigger and smaller in about 5 minutes. You see this all the time on the WRX forums (NASIOC) when a tuner posts how "smooth" the power and torque curve are, by stretching it out like that.

I realize that this sounds like sour grapes, s**tting in your cornflakes, etc. Engines with cam phasing typically have "dips" or "humps", unless you kill the scavenging effects. It's physics. You can move it around a bit, maybe change the shape some. It's unavoidable though.

Have you seen the dyno of a stock car yet? Just a refresher...



Are you saying you can make this graph look flat by stretching it out or something? Wouldn't that be pretty obvious?





Seems like the massive torque dip from the stock car is pretty much flattened out in Hawaiian's car. Not pancake flat, but significantly improved from stock. Unrecognizable even.

[Hawaiian]

Originally Posted by industrial

Have you seen the dyno of a stock car yet? Just a refresher...



Are you saying you can make this graph look flat by stretching it out or something? Wouldn't that be pretty obvious?





Seems like the massive torque dip from the stock car is pretty much flattened out in Hawaiian's car. Not pancake flat, but significantly improved from stock. Unrecognizable even.

Thanks, I almost spat out my Cheerios when I read that post. I like that he comes after my dyno, but leaves the rollercoaster of the nameless dyno alone.

[wparsons]

Originally Posted by Kodename47

Right, so having the ECU exposed to heat means it doesn't work correctly for 1k RPM of the rev range!? Its nothing to do with that

@Xdragonxb0i the reason it starts to lose power after 6.5k is that's where the limitations of the cams are. It was also posted earlier that header design places peak torque around a set area, which in Nameless' case is where I the original dip is (its quite obvious). You could design a header for more top end grunt but I doubt that it would improve on the lower dip.

This. Like I mentioned above, a 4-2-1 header will give bigger bumps in low end power at the cost of some up top. If you went with a header designed for the biggest power above ~5k rpm you would see it breathing better up top but losing a bunch down low. It also needs different cams to keep continue making more power beyond ~6.5k rpm, which would also cost some low down power.

[arghx7]

those are good graphs, thanks

[rx3]

Originally Posted by Xdragonxb0i

I made post about tge p&l header being loud, i contract my statements, it louder then stock for sure but pretty tame when DD. At 75mph , the noise start to bother me.

Have you just swapped the header and left the entire rest of the exhaust stock (and still noticed a significant noise increase)?
And are these 'P&L header dynos' also referring to just the header-swap with a stock exhaust?


Back to topic: If one wanted a header which increased power equally over the entire rpm range, it would need to have variable length runners like a trombone.
(For a similar reason Mazda had 'variable-length-intake-runners' on its 26B race car engine to improve fill factor over a wide rpm range. See picture below.)

[TOTO_86]

That was just my opinion lol worth a try...

[Xdragonxb0i]

Originally Posted by rx3

Have you just swapped the header and left the entire rest of the exhaust stock (and still noticed a significant noise increase)?
And are these 'P&L header dynos' also referring to just the header-swap with a stock /IMG]

No im not running stock. I have the p&l headers, the nameless front/over pipe combo, and AP mid pipe and muffler. My set up.is quiet and but j can tell that all the noise i get comes from the headers.

[Hawaiian]

Originally Posted by rx3

And are these 'P&L header dynos' also referring to just the header-swap with a stock exhaust?
[/IMG]

There are 2 different dynos there, the one with 2 lines is showing the header on E85 and a full P&L exhaust both with and without the cat on the header.

The second dyno chart with 3 lines shows the full P&L exhaust system on the stock tune as a baseline, then the next line is with just the uncatted header, and the last line is reflashing it with visconti's pump gas tune (it still needed tuning).