Back Pressure

[KoolBRZ]

Here are some pics before i install it. Remember this is untested technology, and it could totally suck! I wanted more low-end torque and these are the only anti-reversion things I could find to adapt. They are made for Harley's and need some trimming to fit in the after-market header flanges I bought. The pics with the gasket show that it will seal to the flange just outside the weld holding the cone in. The cones are shaped with a taper going in and a shorter taper going out, and will act as a venturi to speed up flow into the header. I wonder if a dyno will go down to 1000 rpm? It should have more low-end torque when I'm done, and with an exhaust back-pressure valve, should get better mileage too.

[boredom.is.me]

Originally Posted by KoolBRZ

Here are some pics before i install it. Remember this is untested technology, and it could totally suck! I wanted more low-end torque and these are the only anti-reversion things I could find to adapt. They are made for Harley's and need some trimming to fit in the after-market header flanges I bought. The pics with the gasket show that it will seal to the flange just outside the weld holding the cone in. The cones are shaped with a taper going in and a shorter taper going out, and will act as a venturi to speed up flow into the header. I wonder if a dyno will go down to 1000 rpm? It should have more low-end torque when I'm done, and with an exhaust back-pressure valve, should get better mileage too.

The sad part is that you don't know if you helped or hurt your performance. You should have done a dyno pull with the in modified headers, the one after modification. A few runs would not have killed the gaskets. Unless you got an extra header...

[KoolBRZ]

Originally Posted by boredom.is.me

The sad part is that you don't know if you helped or hurt your performance. You should have done a dyno pull with the in modified headers, the one after modification. A few runs would not have killed the gaskets. Unless you got an extra header...

I've already tried 2 other headers. They both had the same thing in common. Less low-end torque than the factory header making it harder to drive in traffic. This is my DD and I like the power and acceleration of a header. I just don't like falling behind in traffic because I don't even have the low-end torque of the factory header. The venturi cone inserts should increase the velocity of flow giving better scavenging, better torque. I actually installed it today, but with a stripped bolt in the over-pipe, I didn't get it all put together. Tomorrow I'll post my first impressions.

[FRSBRZGT86FAN]

Originally Posted by KoolBRZ

I've already tried 2 other headers. They both had the same thing in common. Less low-end torque than the factory header making it harder to drive in traffic. This is my DD and I like the power and acceleration of a header. I just don't like falling behind in traffic because I don't even have the low-end torque of the factory header. The venturi cone inserts should increase the velocity of flow giving better scavenging, better torque. I actually installed it today, but with a stripped bolt in the over-pipe, I didn't get it all put together. Tomorrow I'll post my first impressions.

Are the venturi cones completely sealed behind them? to the rest of the header? Like is there an open space between them and the header tubing

[KoolBRZ]

Originally Posted by FRSBRZGT86FAN

Are the venturi cones completely sealed behind them? to the rest of the header? Like is there an open space between them and the header tubing

No, they do not touch the header tubes themselves. There is about 1/16 to 1/8" or more between the inside edge and the header tubing. They are only attached at the flanges. Once they heat up they should stay hot, since their heat can only travel out through the flange end, not through the header tubing. A hotter, narrower pipe and venturi will give greater velocity to the exhaust flow than the larger unflared transition from the exhaust port original header. I'm getting dressed for battle now, not only against the cold weather, but also against stubborn nuts and bolts. I'm also need to raise my coilovers 1 1/2" for winter mud and snow clearance. Long day ahead, but I'll let you know my initial impressions of the low-end torque capabilities once I get it back on the road this evening.

[FRSBRZGT86FAN]

Originally Posted by KoolBRZ

No, they do not touch the header tubes themselves. There is about 1/16 to 1/8" or more between the inside edge and the header tubing. They are only attached at the flanges. Once they heat up they should stay hot, since their heat can only travel out through the flange end, not through the header tubing. A hotter, narrower pipe and venturi will give greater velocity to the exhaust flow than the larger unflared transition from the exhaust port original header. I'm getting dressed for battle now, not only against the cold weather, but also against stubborn nuts and bolts. I'm also need to raise my coilovers 1 1/2" for winter mud and snow clearance. Long day ahead, but I'll let you know my initial impressions of the low-end torque capabilities once I get it back on the road this evening.

That's actually seems sick, the idea of arming the BRZ for winter lol

[KoolBRZ]

It's back together, tuned with Shiv's latest 2.06 91 Octane Equal Length header tune, and it is fun to drive. Low-end torque and power are definitely higher than with just an ordinary header. I have an A/T and both 5th and 6th are overdrive. I climbed a hill I usually shift down to 5th for, in 6th gear, and even accelerated! I know you flat-earthers won't believe a word I say without a dyno for proof, so I'll try to book some time in the weeks ahead. The important thing is now there is something to give automatic's more low-end torque for better drive-ability. I'll be driving in traffic tomorrow, so I can see how well it keeps up with the V6 and V8 trucks and minivans. PM me for a parts list if you are interested in making one of these for yourself.

[FRSBRZGT86FAN]

Originally Posted by KoolBRZ

It's back together, tuned with Shiv's latest 2.06 91 Octane Equal Length header tune, and it is fun to drive. Low-end torque and power are definitely higher than with just an ordinary header. I have an A/T and both 5th and 6th are overdrive. I climbed a hill I usually shift down to 5th for, in 6th gear, and even accelerated! I know you flat-earthers won't believe a word I say without a dyno for proof, so I'll try to book some time in the weeks ahead. The important thing is now there is something to give automatic's more low-end torque for better drive-ability. I'll be driving in traffic tomorrow, so I can see how well it keeps up with the V6 and V8 trucks and minivans. PM me for a parts list if you are interested in making one of these for yourself.

But what is there to compare it to?

[KoolBRZ]

Originally Posted by FRSBRZGT86FAN

But what is there to compare it to?

Any normal header, stock exhaust, turbo, compare it to whatever you want. I've had stock, SBD turbo, and an Xs-power headers with stock over-pipe, mid, and rear pipes on it before, also stock, dual, and single with dual outlet mufflers. So far the stock setup had the most low-end torque and gave the best mileage. The power and acceleration was sadly lacking though. This setup with A/R header, 2.5" overpipe, 2.5" midpipe, stock rear pipe and top speed pro 1 single inlet dual outlet muffler has more low-end torque, more power, and acceleration you have to see the video to believe. Videos coming later....
[ame]http://youtu.be/sbo8axAwIWI[/ame]

[cdrazic93]

http://www.gomog.com/allmorgan/exhaustbackpressure.html

Exhaust back pressure should be at its minimal extrema, exhaust velocity should be at its maximal extrema.

[KoolBRZ]

Originally Posted by cdrazic93

http://www.gomog.com/allmorgan/exhaustbackpressure.html

Exhaust back pressure should be at its minimal extrema, exhaust velocity should be at its maximal extrema.

A good link but it doesn't cover using venturi's for faster flow with lower back-pressure. The after-market Anti-Reversion cones designed for Harley Davidson's(tm) are made to increase low-end torque for engines with larger, after-market exhaust tubing. The cones have an entrance taper and an exit taper and act with a venturi effect to increase velocity of flow and improve scavenging of the burnt fuel/air mixture. Come down and drive it if you like.