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[ctr99ek]

I know that they create lots of backpressure and do not flow as well as other manis, but what hp can i expect with one, i made 265 with a 50 trim turbo with .48 hotside.  i want to change to the .63.  i seen that ef made 400+ with a huge turbo but i still want to keep my a/c and p/s.  anyone know what is the average power made on the log?

[j.h.christ]

log manifold cons

none

[hotrex]

i use an average equivilence of 37 hp to push out my huge logs.

[MTZ]

i use an average equivilence of 37 hp to push out my huge logs.

dam !! usually takes me 10hp, they just drop right out

[chris]

mid 9's 8 years ago with a log you need more than that

[Joseph Davis]

You aren't going to see jack or shit by way of a power difference if you trade an OEM .48 housing for a .63 housing.

Try a bigger turbo, traditional 7" compressor scroll T3/T04E hybrids aren't exactly large.

[HiProfile]

I know that they create lots of backpressure and do not flow as well as other manis, but what hp can i expect with one, i made 265 with a 50 trim turbo with .48 hotside.  i want to change to the .63.  i seen that ef made 400+ with a huge turbo but i still want to keep my a/c and p/s.  anyone know what is the average power made on the log?

People have taken tubular logs past 500whp. AFAIK nobody has actually logged backpressure between various manifolds, pun not intentional. They just come up with the theory that since 2 runners fire towards each other, it must be bad -- dispite those cylinders having the greatest seperation between firing (one fires when the other's valve is closed). They don't flow the best, but they're not going to hold you back a ton.

I'm going to guess you did 265whp at a wimpy 10psi or something? I've seen stock SOHC's come close to that with logs & equally sized turbos when they used the stock MAP. Upgrade to a 2.5/3/4 bar MAP sensor and quick pussyfooting around. Most turbos are night and day difference between 10psi and 20psi.

[ctr99ek]

thank you for an actual good reply.  i made 265 at 18 psi with a log mani, 2.5in dp open with a/c and p/s.  6inch intercooler, 2in hotside piping and 2.25 in to TB.  stock head and intake setup.  gm 3bar  precision sc50  .48/.60

[crxrocks]

I made 288 hp on almost the exact same setup on my DOHC ZC.  SC50, log manifold, 2.5" downpipe and 2" charge pipes.

I currently have it ripped apart being replaced with a ramhorn manifold and 3" downpipe.  We'll see what affect it will have on the setup.

[88dx]

LOGS are Badass 

[Joseph Davis]

I know that they create lots of backpressure and do not flow as well as other manis, but what hp can i expect with one, i made 265 with a 50 trim turbo with .48 hotside.  i want to change to the .63.  i seen that ef made 400+ with a huge turbo but i still want to keep my a/c and p/s.  anyone know what is the average power made on the log?

People have taken tubular logs past 500whp. AFAIK nobody has actually logged backpressure between various manifolds, pun not intentional. They just come up with the theory that since 2 runners fire towards each other, it must be bad -- dispite those cylinders having the greatest seperation between firing (one fires when the other's valve is closed). They don't flow the best, but they're not going to hold you back a ton.

I'm going to guess you did 265whp at a wimpy 10psi or something? I've seen stock SOHC's come close to that with logs & equally sized turbos when they used the stock MAP. Upgrade to a 2.5/3/4 bar MAP sensor and quick pussyfooting around. Most turbos are night and day difference between 10psi and 20psi.

Eh, the individual cylinder trims on a log manifold 1.8 liter in the 400 whp range are pretty uneven.  It's mostly cyls 2 and 3, as usual, because being thermally landlocked in the middle of the engine plus the pretty much equally crappy restriction to flow across the runners means that they have a much higher ratio of building heat to shedding heat.  It's not the flow, per se, as it is the rate of heat buildup and the use of fuel as coolant that affects the trims.  But, whatever.

thank you for an actual good reply.  i made 265 at 18 psi with a log mani, 2.5in dp open with a/c and p/s.  6inch intercooler, 2in hotside piping and 2.25 in to TB.  stock head and intake setup.  gm 3bar  precision sc50  .48/.60

Sounds par for course.  I make about 300 at 18 on a 9:1 Z6 with the same turbo and a ramhorn, but I think the 2.5" charge pipe and better IM/TB means just as much as that plus it's cheaper to boot.

[88dx]

Dont listen to JD Logs are best

[Joseph Davis]

Only to 399 whp, after that you must sell your soul for a full rice kit.

[Joseph Davis]

Geoff Ricer called me this morning and thanked me for plugging his product.  He's sending me a correctly backpurged stainless steel cookie by way of thanks.  OCZC ain't got nothin' on full rice.

[92CXyD]

all this reading about logs make me think of this:

log

Log Commercial Ren and Stimpy

Ren and Stimpy - International LOG

[ctr99ek]

i actually remmeber that ^^

[SirDragsAlot]

given the fact that a turbo creates a certain amount of backpressure, i doubt the design of the manifold seriousley contributes to any additional backpressure, unless it is made from 1/2 square tubing.  i find that sticking with runners equal or a bit larger than the stock flanges should do fine

[Joseph Davis]

given the fact that a turbo creates a certain amount of backpressure, i doubt the design of the manifold seriousley contributes to any additional backpressure.

Turbos don't create "backpressure," poorly designed turbo manifolds and poorly chosen turbos do.  There are quire a lot of turbo setups that make far far more intake manifold pressure than turbine pressure, which can't be said for NA car as the exhaust always has more pressure than the intake.  Also, log manifolds contributes to more manifold pressure than any other design, that's why they traditionally spool the fastest.  You won't break any power records on one, but they don't hurt power production in low or intermediate power levels.

Also, don't ever say backpressure ever again.  It's a trash word that means nothing.

[92CXyD]

given the fact that a turbo creates a certain amount of backpressure, i doubt the design of the manifold seriousley contributes to any additional backpressure.

Turbos don't create "backpressure," poorly designed turbo manifolds and poorly chosen turbos do.  There are quire a lot of turbo setups that make far far more intake manifold pressure than turbine pressure, which can't be said for NA car as the exhaust always has more pressure than the intake.  Also, log manifolds contributes to more manifold pressure than any other design, that's why they traditionally spool the fastest.  You won't break any power records on one, but they don't hurt power production in low or intermediate power levels.

Also, don't ever say backpressure ever again.  It's a trash word that means nothing.

Reading this reminds me of poeple who believe they have to have some backpressure on their NA 4-stroke engines. Because if they do not have backpressure they will damage the exhaust valves.  ;D

[dvst8r]

Reading this reminds me of poeple who believe they have to have some backpressure on their NA 4-stroke engines. Because if they do not have backpressure they will damage the exhaust valves.  ;D

I always wondered where that started. I remember even as a kid, guys with v8's saying have to have some exhaust or it will burn the exhaust valves ect... But then on my first trip to the track seeing a rail with 4 individual tubes, none more then 18" long. After that I was sure it was an urban legend, but still to this day, I wonder how it started?

[92CXyD]

Reading this reminds me of poeple who believe they have to have some backpressure on their NA 4-stroke engines. Because if they do not have backpressure they will damage the exhaust valves.  ;D

I always wondered where that started. I remember even as a kid, guys with v8's saying have to have some exhaust or it will burn the exhaust valves ect... But then on my first trip to the track seeing a rail with 4 individual tubes, none more then 18" long. After that I was sure it was an urban legend, but still to this day, I wonder how it started?

Yeah I've wondered about that urban legend.  ;D

Maybe somebody was comparing 4-stroke to 2-stroke b/c I think you need a little backpressure in a 2-stroke for the reed valves to close properly or may that is a myth also. ;D

[Joseph Davis]

Most people who think they know everything about cars can't remember highschool physics.

[Tim]

Reading this reminds me of poeple who believe they have to have some backpressure on their NA 4-stroke engines. Because if they do not have backpressure they will damage the exhaust valves.  ;D

The only person that ever told me this also used to huff gasoline on a regular basis and now talks rrrreeeeaaaall sssslllllooooowww 

I never realized any other type of person ever gave it much credit.