what are the advantages/disadvantages of a full header over a log style header in a turbo inducted lsx?
do most people using logs, use them for convience in a specific application/space constraint?

 

Log headers have hot spots and are prone to cracking, also they do not flow as well as a full tubular header, however most street applications will be fine with a log header and they are much more cost effective to produce.

 

i figured they were a more convienent way to do a setup,but what kind of power is the limit? is it possible to make 1000+hp w/ a log header?

 

I think its possible, but consider all the other things required for a 1000+HP setup. The pocket change you might save skimping on your turbo setup will be nothing in the grand scheme of things.

 

I highly doubt 1000rwhp on a single log header type turbo will work out. I'd say it's alot more likely with a twin setup using logs, but I still would shy against it for high HP applications. Log's work great for street purposes, but for full on race, don't skimp out and risk it. You get alot of uneaven backpressure and such with logs and as mentioned before they a prone to cracking.

 

Surely pressure in a pipe is just pressure, equal throughout and that's what you need to spool a turbo without pulsing. So a compact twin cast header system would offer high strength, high pressure and reliability. Oh, it would be compact as well.

If you had a big budget and r&d research you could maybe make something else but without data how would you know it was any better and it would be weaker if done in mild steel.

Boosted.

 

That also depends on the design of the header, if the pipes connecting the header flange to the log are coming in at too sharp of a angle that will definantly hurt things - but most people using logs don't care about maximum possible power, they just want a little boost, and in that case its a fine design for a low budget

 

I'm using a 3" log on my single turbo LT1. My best mph is 143 in the quarter at full weight (3750 lb) at 18 psi in the La summer heat.

Some import Honda supposedly did a test a while back with a log versus tubular merge on a 1.6l. It went from 250 hp up to 300. You might consider that the difference on a v-8 would still only be 50 hp (only 1 bank affected).

Another comparison is mine versus another engine I just built. Mine is a 363 LT1 with a log, T-76, 224/236 cam, and AFR210's. The other is a 377 carb'd with long tube headers with merge collectors, T-76, 230/230 cam, and ported GMPP FastBurn heads. The SBC made 930 fwhp at 18 psi. Do the math and it's not dramatically different in power from mine.

About the cracking. . . if you attach all the flanges together, it will probably crack. My flanges are not attached so they are allowed to slide slightly back and forth across the head during heat cycles. This works surprisingly well. With a copper gasket, it never leaks and the bolts don't loosen up. The turbo Buicks have the flanges attached to each other, but they also have a wavy expansion joint in the log between each flange.

Another thing to consider is that the turbo Buicks have run well into the 9's on their stock log and only 3.8 liters.

Mike

 

so if i were to make my own log set up, i should take my header flanges and cut them apart?

 

Didn't Parish make over 1k with his log set up? Header style will flow better but like others have said its not needed for most applications. No matter how good the pipes look you are still left with one whoop *** restriction in the system. The Turbo itself, I am amazed at what that little inlet hole in the turbo can do. lol

Ricky

 

There was a comparison here a long time ago on a LS1 between a log and header stsyem. It was a HUGE difference. On a F car, you are limited to about 600 RWHP on a log setup because of back pressure and size.

 

so you think that this setup is only gonna make 600 rwhp?



https://ls1tech.com/forums/forced-induction/537009-new-twin-turbo-system-pics.html

 

Key word... TWIN setup... A single log is only good to ~600.

 

Yes. Or, put bellows expansion joints in the log between each cylinder.

 

Nope, not really. Don't forget, the air is moving thru the log. This means pressure in the pipes is not uniform, just like flow thru a pipe is not uniform. Fluid mechanics is a very complicated area.

FWIW, my opinion is like others have said. Log manifolds, like a TTi one, are limited in power by their design.

 

Respectfully disagree.

I made 680 rwhp with a log through a TH350 and loose converter (5400 flash), a blower cam (224/236-114), and [gasp!] an LT1.

Mike

 

Carl i'd have to disagree with you too, logs will and have proven themselves to put down more power than you have stated.

Truck manifolds are more of a log type of manifold themselves, than a shorty header or tubular header and they have been proven to put down excellent HP/TQ.

 

If we are discussing truck manifolds then they will support very large power. I was thinking of a log manifold where both banks feed into a single log.

 

your telling me! I'm taking the class right now. Actually its going pretty easy for me, but when you take a step back and look at the stuff your learning, woah

 

Wait till heat transfer