World's first FT86 Anti-Reversion,(A/R) Header

[wparsons]

Originally Posted by KoolBRZ

From the pdf, it looks like the Intake has 60 degrees of motion, and the Exhaust has 53. In RR it looks like there are negative numbers for the Intake tables only. The highest numbers I've seen are 40 for the Exhaust, and 42 for the Intake. From this I believe the Exhaust adjusts from -9 to +40, and the Intake adjusts from -20 to +45, with 0 being used for the Exhaust closing at TDC, and 0 being used for the Intake opening at TDC. If this is true, then whenever both these tables are above zero there is overlap. I believe this overlap should be reduced for unrestricted exhaust setups, and should be virtually eliminated for FI setups with an unrestricted exhaust.

No, just no. Overlap is needed for power.

Did you even read the left column in the PDF you linked to? It shows the rpm/load conditions where things are targetted to happen.

[RobertPaulson]

Originally Posted by KoolBRZ

From the pdf, it looks like the Intake has 60 degrees of motion, and the Exhaust has 53. In RR it looks like there are negative numbers for the Intake tables only. The highest numbers I've seen are 40 for the Exhaust, and 42 for the Intake. From this I believe the Exhaust adjusts from -9 to +40, and the Intake adjusts from -20 to +45, with 0 being used for the Exhaust closing at TDC, and 0 being used for the Intake opening at TDC. If this is true, then whenever both these tables are above zero there is overlap. I believe this overlap should be reduced for unrestricted exhaust setups, and should be virtually eliminated for FI setups with an unrestricted exhaust.

so are you self tuning and trying this out, or just using a OTS tune and spitting out your theory on how things work?

[Mad1723]

Originally Posted by wparsons

No, just no. Overlap is needed for power.

Did you even read the left column in the PDF you linked to? It shows the rpm/load conditions where things are targetted to happen.

Let him! Just let him blow everything up on his own. That way, once we have the pictures of the inspection window in his block, you can just stand back and say "told you so".

Honestly, at the rate he's going, he's gonna go from FR-S performance to Geo Metro performance real quick.

[Kodename47]

Originally Posted by KoolBRZ

From the pdf, it looks like the Intake has 60 degrees of motion, and the Exhaust has 53. In RR it looks like there are negative numbers for the Intake tables only. The highest numbers I've seen are 40 for the Exhaust, and 42 for the Intake. From this I believe the Exhaust adjusts from -9 to +40, and the Intake adjusts from -20 to +45, with 0 being used for the Exhaust closing at TDC, and 0 being used for the Intake opening at TDC. .

I interpreted it completely different and my spreadsheet with all the calculations are already up here somewhere.

The exhaust tables do not have negative values, the intake ranges from -10 to 40 or 45 IIRC. Also your maths doesn't add up, the pdf shows intake opening range of 44BTDC to 24ATDC... That's a range of 68 degrees. Now we know that the system definitely doesn't have that range so no one knows for certain what the rest angle is and it could vary between engines.

Know what, read this thread that I started a while back:
http://www.ft86club.com/forums/showthread.php?t=57662

[Ultramaroon]

Originally Posted by KoolBRZ

I believe this overlap should be reduced for unrestricted exhaust setups, and should be virtually eliminated for FI setups with an unrestricted exhaust.

Kool, I'm going to put this in a very different way. Forget about big words. Internal combustion engines are all, at their heart, very much like musical instruments. Given the length and other properties of an intake manifold and the exhaust manifold, the whole system likes to "sing" at a particular frequency. Why do drag cars have that characteristic lope at idle? Valve timing with a great deal of overlap (used to be called crossover) that is optimized for maximum charge into the combustion chamber and work out at a specific frequency. There is a tall narrow powerband because all components are tuned/timed to operate at that specific frequency.

How do we get a more usable daily driver? By detuning the system to get a shorter wider powerband.

How do we get more power out of the system across a broad range of frequencies? Variable valve timing. Oversimplified but basically that's it.

Unless you have a dyno or are able to model the whole thing using CFD, you're going to end up with a mess. Just be prepared for disappointment and make sure you can get back to square one before you change anything.

BTW, I haven't read the pdf.

[churchx]

Somehow when browsing parts shops stubled upon part of opening/closing direct bypass with electric motor & valve in exhaust by simple press of button from inside car. That made me think, that it should be very easy/simple/cheap for manufacturer to make something partially closing/fully opening inside exhaust to for exhaust to be dynamically optimized for specific rpm-s by ECU. Yet vendors didn't implement it. Even if it's just +5whp/wtq, implementing it by economy of scale shouldn't be too expensive. Often vendors spend even more funds and time on fine-tuning other bits, but none, including for hi-end very expensive cars did it this way. Imho that's another weight on scale of this being more of a placeboo then actually improving performance.

[Ultramaroon]

Originally Posted by churchx

Somehow when browsing parts shops stubled upon part of opening/closing direct bypass with electric motor & valve in exhaust by simple press of button from inside car. That made me think, that it should be very easy/simple/cheap for manufacturer to make something partially closing/fully opening inside exhaust to for exhaust to be dynamically optimized for specific rpm-s by ECU.

Yamaha did it first with their EXUP system. This is basically what Kool is playing with but, again, unless the opening varies with respect to engine frequency, you're robbing Peter to pay Paul.

edit for truth: EXUP was at the collector end of the header so it's not the same as Kool's experiment. My bad.

[churchx]

Interesting. But most implementations/vendors listed in article are for motorcycles. But why i don't hear about it being used for cars? Precision controlling engine variable valve timing seems to me by magnitude harder task then simplest valve on exhaust tube. Vendors even play with dynamic aerodynamics like deployable wing at speed. But where are exhaust valves in common cars? I heard about them at car exhausts only in context of changing sound/noise, not optimization for rpms. :/

[Ultramaroon]

Originally Posted by churchx

Interesting. But most implementations/vendors listed in article are for motorcycles. But why i don't hear about it being used for cars? Precision controlling engine variable valve timing seems to me by magnitude harder task then simplest valve on exhaust tube. Vendors even play with dynamic aerodynamics like deployable wing at speed. But where are exhaust valves in common cars? I heard about them at car exhausts only in context of changing sound/noise, not optimization for rpms. :/

[warning - wild-assed guess to follow] I know the EXUP predated any variable valve timing. I think exhaust VVT may be more effective?

That's it. No more crazy guessing from me. Anyone more knowledgeable please shoot me down.

[ImBatman]

Originally Posted by KoolBRZ

Yes, I am running a UEL tune on an EL header. I watch my readings on my OFT, so I know it's not hurting my engine. It definitely runs different though. Heh, heh, always question, always try something new.

Can you please engrave your username somewhere visible on your car so it can be identified when it hits the used-car market?

Lord have mercy on the poor soul that buys this car without knowing it has been experimented on more than Frankenstein.

I'm all for questioning conventional wisdom and trying different approaches to help pioneer new solutions for common problems, but using a certain tune that was designed specifically for an alternate setup just to see what happens is a whole other brand of stupid. There's a reason it is designed and written the way it is... it serves a very specific purpose. That's like using a hammer to try and torque a bolt.

[KoolBRZ]

I have a theory that the valve overlap needs to be adjusted to compensate for the difference in back-pressure when switching to an unrestricted exhaust. in the PDF it states valve overlap is used to reduce pumping losses and increase economy. Well my economy went down when I went to an unrestricted exhaust, so this is what I have done.

First I reduced valve overlap to see if that made any difference. Mileage went down some more. Then today I added more valve overlap and I'm going to see if that change compensates for the unrestricted exhaust. Tell me what you think, don't hold back, I can take it.

[KoolBRZ]

Originally Posted by wparsons

No, just no. Overlap is needed for power.

Did you even read the left column in the PDF you linked to? It shows the rpm/load conditions where things are targetted to happen.

I agree that overlap is power, but, it is also economy.

[KoolBRZ]

Originally Posted by KoolBRZ

I have a theory that the valve overlap needs to be adjusted to compensate for the difference in back-pressure when switching to an unrestricted exhaust. in the PDF it states valve overlap is used to reduce pumping losses and increase economy. Well my economy went down when I went to an unrestricted exhaust, so this is what I have done.

First I reduced valve overlap to see if that made any difference. Mileage went down some more. Then today I added more valve overlap and I'm going to see if that change compensates for the unrestricted exhaust. Tell me what you think, don't hold back, I can take it.

It works! My theory is correct. 1 or 2 mpg difference could just be my imagination, but I just went to Portland and back and got 6 mpg higher than usual. This proves that compensation to the AVCS valve overlap should to be made when changing to an unrestricted exhaust, so that the power and economy can be brought back up.

I immediately noticed better acceleration, and low-end torque, particularly in 5th and 6th gears. Normally my car bogs down as soon as I shift to 5th, but now it accelerates smoothly through all 6 gears. Now bear in mind, my car is an auto, and both 5th and 6th are over-drive.

I now have an unrestricted intake and exhaust, so I have some more work to do to adjust the valve overlap to compensate. This does point me in the right direction though. I'll post AVCS tables if anyone's interested, just ask.

[Dipstik-sportech]

Post it