a few nights in the garage

[cutsstuffup]

and i ended up with this, it will end up in my 72 wagon with a turbo and k-jet from a volvo 240. the car ran like poop when i got it, the injection was all messed up so i bought some crappy empi 40's and it ran a lot better but im just not happy with it. so hopefully this will help it get out of its own way. this is not equal length but i think it should work well enough.

[ubercrap]

This is going into a 411? Neat anyway, let us know how the rest of the project goes. Equal length isn't as important in a turbo setup, right?

[raygreenwood]

This is going into a 411? Neat anyway, let us know how the rest of the project goes. Equal length isn't as important in a turbo setup, right?

Yes...it is just as important. However...with regards to intake tracts...its less important. But exhaust it will be important. Ray

[fusername]

i could be wrong, but when you go turbo, straight lines are more important that equal length, but don't quote me too hard on that. but in our flat 4 engines, its damn hard to avoid spaghetti.

looks nice tho, glad I didn't have to make it

[raygreenwood]

No.....the exhaust has no brain. It is a volumetric efficiency device. It has no idea that you have a turbo....and that makes no difference. This makes the assumption that each cylinder and head have wildly different and varying exhaust volumes.

With a turbo....you can have varying intake tracts lengths and still get roughly the same volume into each cylinder (albeit with variations in velocity loss and drag because of intact tract variations)....this is important because if the cylinders have wild variations in charge efficiency..they are hidesouly unbalanced in HP and torque output.

Once the fuel and air is combusted in this relatively equal set-up....they must have equal lengths or one will be more rstricted than another...causing exhaust flow and overhating issues on one cylinder compared to another. Exhaust equal length is far more important and is always important. Ray

[fusername]

ah what I was thinking was the turbo wants straight lines so the absolute minimum amount of energy is lost prior to reaching the turbine. bends suck energy out, how much wouuld be a fun physics problem but I haven't learned how to do any of that stuff. The equal length thing is to maximize the effects of scavenging as I understand it, which is less important I THINK because
A) turbo pressure fills the chamber quite well so the small gains are less significant
B) turbo back pressure lowers the energy available for scavanging, shirking the small gains to smaller.

[raygreenwood]

No...equal volumetric efficiency is 100% important regardless of induction system. If you allow variable flow of exhaust exiting the cylidners because of wildly varying exhaust tract length....you affect the ability to flow intake charge...even with a turbo. A restriction is a restriction.

What you are assuming is that because there is exhaust back pressure against the turbine (which there should not be)....that the bacjkpressure will just equalize across teh exhaust system....which implies that it backs up from areas flowing more to areas flowing less. Think about that. Ray

[fusername]

its not that i think the backpressure differences go away with vaying lenghts, its that the equal backpresure is less important than loosing velocity through spaghetti bends. Also my understanding of equal length is pulse timing at the merge is key, the flow will be more affected by bends than length, within reason of course.

and of course the simple fact that exhaust is more an art than a science doesn't help anything.