A 3.4 DOHC Build then... F40 Turbo (Page 5/57)
Squeaky FEB 14, 12:13 PM
Looks absolutely phenominal! I consider my DOHC swap pretty clean but your's is another caliber. I'm curious to see how it performs with the stock intake, other DOHC's I've seen have had short-runner intakes. No doubt the numbers will be impressive. Had Pontiac made the 1990 prototype an optional factory turbo on the DOHC would've been unreal!
ericjon262 FEB 14, 04:53 PM
Looks good!

I used a chop saw to make the merge for my waste gate, if your mid pipes meet on a level plane, it wouldn't be too hard, just cut at the center of the pipe, and weld. if I had done it, I would have started at the turbo and worked back to the manifolds though.



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we're in desperate need of a little more religion to nurse your god-like point of view...

Built not bought...

http://www.fiero.nl/forum/Forum2/HTML/119122.html

Fierobsessed FEB 14, 07:28 PM
Mine aren't on a level plane, they are rotated about 5/8". Also, since I had to cut a little on an angle for the front bank pipe, they are also slightly lopsided, thus the need for a laser drawn line. In using a cutoff wheel for the rough cuts instead of the sawzall this time because I can be very careful with that tool. The sawzall tends to wander off on the other side too much for this critical joint. The line is slightly tilted and rotated from an even plane. I'll finish the cutting and welding of that joint tomorrow I hope.
ericjon262 FEB 14, 07:45 PM
sorry, I was having a killer brain fart when I posted that, I see exactly how you're gonna do that, it'll work great!
Fierobsessed FEB 16, 06:49 AM
The Crossover progresses

To do the "Y" on the crossover, I needed to draw a somewhat accurate bisection line on my two pipes that I fitted to mate to the turbo flange. So I devised a laser setup, mainly my camera tripod, and a cheap laser line unit from Home Depot. These pipes were somewhat expensive, so I wasn't taking any chances of needing a re-do.


See the lines


Then it's back to the garage for some air cutoff tool action! It took a good 10+ Minutes to actually do this cut, but I kept it shy of the line so I could surface it to specification on the belt sander.




Tack welded one of the two pipes to the flange


Then, test fit the other pipe, a little work with the belt sander, then it fit perfectly!


Full steam ahead for the welds.
Caution, Hot!


Picture showing what the inside looks like after a weld using solar flux to protect the back side of the weld.


Then, a couple minutes in the blast cabinet, not a trace left! But, you can see that the welds are a little lacking in penetration. In hindsight, It might not have been a bad idea to "V" the joint before welding. Oh well. Too late to do something about that. I got used to working with thinner metal... Still, got enough penetration to keep me from losing any sleep.




Another fit check, everything is spot on!



Next challenge, the Wastegate!

Ok, so heres what I have planned, a simple pipe welded to the Crossover's "Y" coming straight up, then a 90 towards the firewall, then the wastegate. Nice and simple!


So first I took the 1.75" piece of straight pipe, shortened it, cut it on an angle and ground the heck out of it till it fit tightly where I needed it to go.


Then weld, easy stuff.


Another shot of the inside, with the wastegate pipe in place.

Tomorrow, I'm going to drill the wastegate hole, and maybe weld in the wastegate flange, and the 90. I don't have much time to play tomorrow.
Till then...
the_bandit FEB 16, 09:00 AM
You have a great mustache! And those welds look great! Keep up the good work!
Joseph Upson FEB 16, 09:29 AM
Looks show room perfect, very impressive. Stainless expands more than mild steel so there will definitely be some stress in the merge pipe to the turbo without an expansion joint. Given the way it connects to the manifolds I believe you'll be able to resolve it by getting the pipes good and hot, then backing the bolts off just enough to relieve the expansion stress and tighten them back down before it cools that way when it does there will be a net compression force pulling the manifold ends together.
Hudini FEB 16, 11:47 AM
It will expand and bend. Just a matter of where. Mine bent the metal holding the turbo when hot which caused leaks between the logs and crossover when it cooled back down.
Fierobsessed FEB 16, 03:27 PM
Expansion will not be an issue. I only have just this one pipe ridgid mounted. The turbo is bolted to a somewhat flexible mount.This pipe will push, pull or twist the turbo in any fashion it sees fit. The down pipe will have a flex, the wastegate has a flex, and there is a flex going in between the rear bank and what I have made so far. I am allowed 1 solid tube, just so long as every other connection or mount has some flex.

I got my morning off to an early start,

Wastegate feed before drilling


Wastegate hole from the turbo inlet flange, after some fancy work with a hole saw,


Then I pretty quickly got back into the welding, First I joined the wastegate flange to the elbow, then welded the elbow to the wastegate pipe from the crossover.


I welded the wastegate outlet flange directly to the flex pipe, and I'm holding the loose elbow wich I will probably have to get to tomorrow some time.


The fitment of the wastegate feed


And the crossover as it is now




Thats all I'll be able to do today. Tomorrow, I hope I will be able to do the little elbow for the wastegate outlet to the down pipe, maybe even get the rear bank tube, flex, and flare all in place. That would complete the crossover and wastegate system completely.
Fierobsessed FEB 18, 12:07 AM
Did a bunch of work today. First, my intention was to finish the wastegate plumming. I cut the hole in the downpipe, formed the elbow to fit it, and welded the elbow to the pipe, then to the flex tube.



All bolted up


With the wastegate system all buttoned up, I turned my focus to the rear bank exhaust pipe, this is what I came up with.

This is the flex that allows expansion of the crossover tube without cracking.

All welded up. This concludes the building of the crossover, which is probably the most difficult part about creating a turbo setup.



I put the engine back together, a bit to make sure everything is going to fit and work. I do have to grind just a little bit of material off of the lower intake manifold, No matter what I did it was going to hit the crossover pipe, there just wasn't enough room back there, I figure 1/8" of clearance is good enough, and its not an important chunk of aluminum.


In the final install, I plan on wrapping the crossover tube with some "Lava Rock" header wrap. The crossover passes the charge pipe, the air filter and the turbo compressor housing. I need that pipe to give off minimal heat to the engine compartment. I might even make a metal shield to go around the wrap, or to shield the air filter and compressor housing I'll cross that bridge when I get a bit closer to finished.

I need to rip the engine off the cradle, notch the cradle for the transmission clearance, do a little reinforcing of the rear cradle. So that's next.

To do list:
Make a mount for the intercooler
Do some small piping for the wastegate and BOV controls
Make new fuel lines that work around the turbo
Make a new water neck that works around the turbo
New 3" exhaust system
Add plumming for the intercooler water lines and pump
Wiring harness

There are a bunch more things to do... but honestly, I think the hardest part is now in the past.

[This message has been edited by Fierobsessed (edited 02-18-2013).]