Need Opinions On Exhaust Manifold (Turbo)

[eckoxl]

I am seriously having a mental arguement over how I want to do the exhaust on my turbo build.

3400 Log Style & Custom Crossover
Using 2 front manifold with ported inlets and custom crossover

3500 Header Style & Custom Crossover
Maybe port the inlets, and then use a custom crossover. Only thing I'm unsure about is if the will fit alright in the Grand Am engine bay.

Custom Log Style
Basically the same as stock manifolds, just wider tubing.

Turbo Headers


Something like these, though they would be the most expensive and I have no one who can weld these for me.

Any thoughts, opinions, anything?

[RedZMonte]

Depends on what your goals are.. Tubular will make the most power but then you have potential things like Cost, Cracking, Heat, ect... But again, should yeald the most performance if you don't mind investing the time and money in making them.

Cast minifolds will last longer (not crack), are compact and will do what you want (allow you to install a turbo), they are cost effective....
3400 Log Style & Custom Crossover
Using 2 front manifold with ported inlets and custom crossover

I would start with 2 cast logs and build a nice X-over and DP and if you want more out of it you can allways build the tubular ones later... Just my opinion.

S

[WrathOfSocrus]

The exhaust ports are unevenly spaced, so if you put a front log on the rear it faces the opposite direction as a front log on a front head. I just picked up some TGP parts mainly for the fact it has the proper rear log for that use. I agree if it is possible to source the TGP rear log that it is a good start. I intend on having a custom pipe made to connect the logs to a new turbo flange. After I get the intake and exhaust piping worked out and the motor tuned properly I will consider upgrading to full tubular manifolds.

Without the TGP rear log there aren't many options. I know certain body cars came with a rear manifold that more or less looked like a log with cross over and downpipe connections. The exit could be blocked so the exhaust goes out the crossover connection although I'm not sure how efficient that would be. It would be cheap and effective enough to do what it needs to, which is direct the exhaust in the direction of the turbo. Being cast iron it is durable and could probably be resold after it has lived its life and is ready to be replaced by a better setup.

[RedZMonte]

you could allways have someone make a custom log for the rear.... that would be the next easiest..

Either something like these, the 1st one i would expect to flow simmilar to the stocker:
I now see the offset spacing on the front vs the Rear manifolds.



S

[RedZMonte]

here is a board member selling modified TGP manifolds for 3x00. good price

http://60degreev6.com/forum/f105/tgp-parts-rebuilt-x-over-and-manifolds-t45784#post416746

[IsaacHayes]

Certain 3100 rear manifolds had a side downpipe, which is right by where the cross over is. So you can block that and the flow direction would be close to what you need.

[Schmieder]

I am using stock manifolds and a custom designed cross-over. When I get the car on the road I'll let you know how it goes.

I decided to stay stock manis for convenience atm. Down the road I am going to build a header style manifold system for the turbo.

There is someone on this forum who built a turbo using the stock mani's AND stock cross-over. They attached the turbo right onto the cross-over. I read they were getting in the 13's for the 1/4 mile. So I guess you really can't go wrong with what ever you choose. Just as long the pipe is at least 14 gauge.

[BoostED00GagT]

herees what i made when i decided to go with stock sytle manifolds..i got a rear 3100 manifold..cut the downpipe flange off while it was bolted to a head, and welded a piece of pipe in its place...ported it out..and ported it out so the direction of the last port would somewhat flow towards the crossover..sorry for the shotty pic..

http://60degreev6.com/forum/attachment.php?attachmentid=1897&d=1219023445

[eckoxl]

thanks. i have figured out how to do it. now just need to find a welder.

[MidnightriderZ24]

gotta go all out! lol

[Superdave]

you wouldn't have to port or modify the 3500 "header" manifolds in any way. Just use a few U bends to make the crossover.

[Joseph Upson]

gotta go all out! lol

That's about as bad as me with the front mount intercooler in a Fiero, although it dropped intake air temps more than 100 degrees, I'd be better off with it near the engine with a ducting system guiding air to it.

On turbo cars I highly doubt an elaborate exhaust header is going to be significantly more effective on a street driven car than a well designed simple log style manifold with exhaust flow directed toward the turbo. In other words no 90 deg "T" intersections, if all ports leading into the log are slanted toward its exit end you probably will not notice a difference between it and a header that results in upwards of 3 or more times the exhaust tubing volume that has to be filled before it reaches the turbine.

It's hard not to be creative but I'm learning that except for the return I received on the expense and effort of putting an intercooler at the front of my car, headers for a turbo on anything less than an all out racer are not justified. I've gathered that from what I've read and experienced. Turbo vs. Supercharged vs. Naturally aspirated all have different flow characteristics, call for different camshafts for optimum performance and therefore respond differently to header exhaust systems and I believe turbos show the least positive response since at full load the exhaust pressure is usually 2 or more times that of the intake pressure. They're probably great for managing pulses but I don't think they are able to do much if anything for scavenging which is very important.
My headers are coming off and being replaced with a tubular log design for space savings and simplicity. The cast iron manifolds are great to if you can get the flow ironed out, I would not block off the exit end of the rear cast manifold in an effort to get it to flow out the inlet end for the front bank, the contours oppose it and the result will be poor flow characteristics especially for the cylinder furthest from the exit.
Spaghetti headers look great but I highly doubt they payoff in performance what they do in looks. I'm tired of "taking the back door to get to the front yard". It causes a lot of unnecessary down time and expense.
Whatever you do give it the appropriate amount of thought. Number crunching is a good thing.