Turbo ready 3400

[dykz34]

Going off of your headers are useless with a turbo information... would it still be worthwhile to upgrade from stock cast manifolds to tubular, un-even length manifolds? Will it make a difference what size piping is used? Or, does pre-turbo backpressure not mean as much? Basically what I'm asking is would it be worth the effort to ditch the stock manifolds in place of tubulars?

[Mechanic]

If a tubular manifold design for a turbo retrofit is not engineered correctly, you will be plagued with stress cracking problems. Even the stainless steel tubular manifolds that GM engineered for the Fiero V6 are prone to cracking (without a turbo attached), and that is not very encouraging. The fact that nearly all TGP crossovers have or likely will crack even though they were engineered with a flex section to decrease stress influence is something to think about.

Increasing the tube size beyond a certain point will decrease velocity substantially, not a good thing. It is also important to note that it is not exhaust gas velocity alone that powers a turbocharger, heat is an extremely important factor, and no thin wall tube that I am aware of can even compete with cast iron as far as heat insulation is concerned.
One benefit offered by a tubular manifold woud be the smoother path and transition they provide. One would simply have to decide for themselves if this would be enough of an advantage to justify the expense.

The engineering paradigm I used was based on the GM Syclone/Typhoon design. Basically a cast iron manifold with a mitsubishi type turbocharger mounted on the discharge side. This is about as close as you can get a single turbocharger to the exhaust valves on a V6, and the distance here is nearly a direct relationship to the performance potential of the turbocharger. I think most of the Sy/Ty guys at the strip would laugh at the idea of using a tubular manifold, and many of those motors are developing over 500hp.

[germ]

germs remarks have been deleted. Next time im deleting him.

anyway....

the stock 3x00 mani's DO NOT work very well. i am using one right now, it has cracked already and was brand new 4 months ago.

headers are very likely the only way to get good flow from the rear. considering the stock manifold has a T, one end connects to the xover, and the other to the DP, so there is basically a 90* wall that the flow hits. not good.

i fabbed up an insert to go in the DP part of the T to block flow from going down to that side of the T. i welded a plate to the inside part of the insert to help "guide" the flow thru the xover area. it works, but not well.

headers are the ONLY solution to that, even if that are log headers designed similar to how the cast iron ones are, they will still be better than the stock rear mani, and plus it gives more room to get that DP back to the exhaust by the firewall.

and i do not agree with the 4t60e statement.

i am running 10psi right now, stock tranny, 189,000 miles and she shifts and runs just fine. if it does go out, to build up the tranny to hold more power will cost less than $1000 WITH a LSD, and will be MUCH more reliable and consistant than the 282. however, the fun of driving a manual wieghs in pretty heavy too.


*** on a side not, Ben, i dont care for you, you dont care for me, thats why i dont post on this site much either, because of the simple fact that when i first came to this site as a forum newbie over 2 years ago, you were a complete and total dickhead when i posted something that could have fit in the forum section i posted in, so you moved it, didnt tell me, so i posted about it, and you basically told me to fuck off and post correctly, and not in such nice phrasing either! and you are STILL like that. why do you think there are only like 12 of you that post on this site consistantly and almost all 12 of you think your king shit of the 660. you guys keep scaring away all the new people or pissing them off, or they get tired of waiting a WEEK to get a reply.

you can delete this and you can delete me if you feel the need, but the problem is still there, a controlling, arrogent, smartassed, dick for an admin constantly bitching because people are being human.

i did mention to brad the other day why i posted the "dumbass" posts and i think he understood me, and i understood him on why he originally locked this thread. but then you post what you did, hmmm, cant leave a lying dog alone huh? i wouldnt have even wrote the last half of this message if you wouldnt have said what you said.

[Mechanic]

You cracked a nodular cast iron manifold? Ya right buddy, see ya...

[RacerX11]

the stock 3x00 mani's DO NOT work very well. i am using one right now, it has cracked already and was brand new 4 months ago.

Where exactly are the manifolds cracking? I wonder if it is a heat issue, or if the turbo mounting is causing too much flex in the manifolds/crossover.

considering the stock manifold has a T, one end connects to the xover, and the other to the DP, so there is basically a 90* wall that the flow hits. not good.

i fabbed up an insert to go in the DP part of the T to block flow from going down to that side of the T. i welded a plate to the inside part of the insert to help "guide" the flow thru the xover area. it works, but not well.

Aren't there a couple different 3X00 rear exhaust manifold designs? I haven't looked into both, but I wonder if the other design has less of a tee-intersection, and might flow better in this cross flow configuration.

Marty

[funky3821]

You cracked a nodular cast iron manifold? Ya right buddy, see ya...

The 3x00 in the montes are know for breaking. I have done like 5 engine swaps and all but one had a broken rear exhaust log!

I would think that headers would be better off being that they flow better and seperate the cylinders from one another so there is no reverse flow from another exhaust port! But I am only logisticly thinking about it so I could be wrong!

Does anyone have pics of the rear log from another 3400 vehicle?


Germ Seriouly don't flame in this thread it is very apparent that you two don't get along. I understand where you are comming from though. Because being able to pull stuff that the MODs does and having that extra POWER, if you will, makes some people thick headed! I really want this thread to stay unlocked and the only way that will happen is for me and everyone else to say aloud what they think about certian MODs and to not type it!

[germ]

You cracked a nodular cast iron manifold? Ya right buddy, see ya...

would you like pics?

have you ever seen one cracked?

its inbetween cyl 3 and 5 that it ALWAYS cracks.

personally i am on the 3rd one and have seen quite a few others.


and just to clarify, i am refering to the stock 95-99 W-body rear cast iron manifolds.

the way i understand it, the w-body was the only one to get this version of the rear mani. please correct me if i am wrong.


funky, i was not trying to flame anyone. *in my best Sgt. Friday's voice, "just the facts ma'am, just the facts"

[germ]

oh yea, i forgot to add, the crack without the turbo.

its from the exhaust pulses in cyl 1 and 3 that collect right at that point and evidently that causes a "hot spot" on the rear mani and cracks.

i have pics at home, i will post them up tonight (if im not banned lol)

[Mechanic]

Perhaps your idea of a stress crack is a bit confused, heat induced cracking is a completely different issue, and typically related to improper tuning or engine mechanical failure. Here is what you may want to refer to in your future observations :

[funky3821]

Mechanic,
What is that Manifold off of? Cause that sure doesn't look like cast iron, although I have been known to be wrong!!!!

You know though, that would be perfect for a rear manifild for a turbo. Atleast that would line up pretty dood with the crossover.

[Mechanic]

That happens to be a tubular stainless steel manifold, considered by many to be of high quality. Stock nodular cast iron manifolds do not stress crack.
I can assure you that any of the old boys like me that have used headers for years can tell you exactly how much fun stress cracking of tubular headers can be.

[bszopi]

Here is a comparison of 2 common 3x00 exhaust manifolds:



The better in the picture is referring to flow, so not necessary pertanent to this discussion.

And here is yet another 3x00 rear exhaust manifold version:

[Mechanic]

The manifold in that last pic appears to be the 95' 3100 design. One can visualize from that illustraion how a turbocharger that actually tucks back towards the motor would fit quite well there.

[germ]

mechanic,

you need to realize that the manifold is not ENGINE specific, but BODY style specific.

Most W-body's use the bottom "T" style manifold in the first pic. that is the style that I am refering to on the monte carlo's, 95 - 99, as well as the 95-01 lumina's with the 3100 engine. i am not sure what other cars it came on or other body styles, but i have gotten rear mani's from a cutlass supreme, buick century, and i THINK a grand prix (not 100% sure what the tag said right now).

as your looking at the pic posted above, where i am talking that it cracks is just to the right of the left runner. in between cyl 3 and 5, like i stated before.

the bottom part of the T is the flange that the DP bolts to. as the engine rocks, it places strain on the whole left side of the manifold. now add in the fact that the log cast iron manifold flow is crap, the exhause pulses actually meet right at that area causing a VERY hot area. after MANY cycles of hot and cold, ESPECIALLY in cold ass states, like MN, where it could go from a hot 1200* only to cool off down to -20* in winter. that takes a toll on those types of parts.

i would assume if you live in a much milder climate it may not happen as often and all of the swaps i have seen are from the colder winter climates.


if need be i can post pics.

[funky3821]

Thanks Brad!

So if I were to cap off that exhaust from the Grand AM gt, Marked better in Images above, would that still get the exhaust pulse putting a reverse pulse back at the cylinder?

That it why I was thinking that seperate runners to a collector would be benificial to a turbo!