Question : Mounting a Turbo

[Schmieder]

What is the preferred method to secure the turbo to the engine?

Can I let the turbo 'float'? As in the only source of securing it is the link ups. i.e. bolted to exhaust manifold, bolted to downpipe, attached to intercooler pipe?

The turbo will be sitting about 25* off center from top of custom manifold. I plan to weld the exhaust intake to turbine coming in from the bottom, again about 20-25* off center.

Currently I have 16ga. aluminized steel pipe at 1.75" diameter and two will be joined to the flange. I decided to keep the log manifolds but build a custom crossover.

Will this be strong enough? Or should I think about designing further support?

1996 Grand Prix 3100

[bszopi]

I would design more support. I could see the welds at the flange point, or in other areas of stress, start to crack do to the heat cycling as well as the weigh of the turbo, and all the additional movement it is going to see while driving. Every bump you hit will cause the turbo to try to rotate off the flange, therefore putting stresses on the welds.

[Schmieder]

I would design more support. I could see the welds at the flange point, or in other areas of stress, start to crack do to the heat cycling as well as the weigh of the turbo, and all the additional movement it is going to see while driving. Every bump you hit will cause the turbo to try to rotate off the flange, therefore putting stresses on the welds.

I thought so. i was hoping it would be enough but, guess not.

Thats ok though. I have a lot of scrap steel and a few old valve springs. I'm sure I can come up with something.

Any suggestions towards a popular method? Can I secure the downpipe and use that as a strong point? Could I secure the pipe just before and just after the turbine or should I secure directly from the turbo itself? I'm sure I could fix up something but I always like to hear from experienced builders.

[ghrarhg]

Here's the bracket I fabbed up. The TGP crossover has 2 lower holes for a mounting bracket. I attached mine to the upper holes in my transmission. There's flex pieces in the crossover, and in the downpipe, so rigidly mounting the turbo should be fine.

[Schmieder]

Here's the bracket I fabbed up. The TGP crossover has 2 lower holes for a mounting bracket. I attached mine to the upper holes in my transmission. There's flex pieces in the crossover, and in the downpipe, so rigidly mounting the turbo should be fine.

looks good. And yeah, I have flex pipe. I anticipated the need for thermal expansion/contraction...ect.

Mounting off the trans is a good idea. I was considering the driver side of the front cylinder heads where the engine mount bolts. But then the idea of any stress disturbing the head gaskets turned that idea off.

With welder in hand and my German brain ticking, I'll engineer something. But the advice you guys give is great.

Thanks

[Joseph Upson]

You should consider using 14 ga tubing especially if you intend to use heat wrap. I'm not perfectly sure but I would expect aluminized steel to have a lower melting point than pure steel. I wouldn't worry at all at the turbine outlet but between the turbo and the heads I would lean toward the safe side. Mandrel bent tubing is thinner on the outer diameter of the bend than the specified gauge due to the stretching that occurs.

I made the mistake of using 18 ga steel tubing once and burned through it in about 100 miles worth of driving. The turbo forces a lot of heat into the primary tubing so better safe than sorry unless you've had very good service with it in this application before.

[Schmieder]

You should consider using 14 ga tubing especially if you intend to use heat wrap. I'm not perfectly sure but I would expect aluminized steel to have a lower melting point than pure steel. I wouldn't worry at all at the turbine outlet but between the turbo and the heads I would lean toward the safe side. Mandrel bent tubing is thinner on the outer diameter of the bend than the specified gauge due to the stretching that occurs.

I made the mistake of using 18 ga steel tubing once and burned through it in about 100 miles worth of driving. The turbo forces a lot of heat into the primary tubing so better safe than sorry unless you've had very good service with it in this application before.

I wondered that myself but I feel I should be ok. And if not, I'll just have to rebuild the manifold.

You used 18ga, I'm using 16ga. Doesn't seem like a big difference but it can be.

But you may be right, that would suck to burn through. What psi boost were you running as that will make a big difference. I plan on starting at 5 psi and working up to 8psi max.

I'm not doubting you, I'm just wanting to know what specific conditions you were running.

If you don't mind I ask...

What psi were you running?

Stock camshaft? (or what degree did your exhaust valve open?)

How well was your tune? (bad tunings can burn much hotter then need be)

Was the manifold flow good or somewhat restrictive?

Did you use wrap?

And how long/often did you punch it WOT?

Did you use an intercooler? (intake temps can alter exhaust temps, but only slightly)

How efficient was the turbo compressor map?

please don't be offended by my series of questions. I am just deeply curious.

[3400beretta]

Extra supports for the turbo are not needed unless you don't know how to weld. I felt comfortable putting nearly all my weight on the turbo flange of my crossover once it was all together, I doubt a 20lb turbo is going to hurt anything. Not to mention, I can't think of a single car that came with supports from the factory.

But if you insist, make sure the bracket comes off the engine/transmission, NOT the frame/body of the car.

[Schmieder]

Extra supports for the turbo are not needed unless you don't know how to weld. I felt comfortable putting nearly all my weight on the turbo flange of my crossover once it was all together, I doubt a 20lb turbo is going to hurt anything. Not to mention, I can't think of a single car that came with supports from the factory.

But if you insist, make sure the bracket comes off the engine/transmission, NOT the frame/body of the car.

lol, I pity the individual who would do that, mount a part to the engine AND the frame. It would rip it up in a heart beat.

Knowing what you advise, I determined a mild support of the trans will be best. My welding skills are good. Not the best looking welds but they are through. And just to be an engineering fool (lol) I'm going to add a spring to absorb shock and thermal stress.

PS- Hey guys, the turbo came today!!! Along with my gauges, wastegate, boost controller, and other stuff.

[ForcedFirebird]

I used 14ga on Loner's car, and it was "floating" on the end of fabricated headers and y-pipe. The system is still kicking, and during fabrication and the decision weather or not to make a support, the two of us stood on the radiator support and bounced on the turbo, only thing that happened was the car bounced. I welded everywhere the header primaries were even remotely close, and added a little metal in some spots.

His was not a daily driver for long, so the heat cycles may cause an issue over a prolonged period.

LOL at Joseph, Loner brought some 18ga to use for a DP/intake tubing and I actually laughed at how thin it was - definitely wouldn't attempt 18ga turbo manis.

[Joseph Upson]

I wondered that myself but I feel I should be ok. And if not, I'll just have to rebuild the manifold.

You used 18ga, I'm using 16ga. Doesn't seem like a big difference but it can be.

But you may be right, that would suck to burn through. What psi boost were you running as that will make a big difference. I plan on starting at 5 psi and working up to 8psi max.

I'm not doubting you, I'm just wanting to know what specific conditions you were running.

If you don't mind I ask...

What psi were you running?

Stock camshaft? (or what degree did your exhaust valve open?)

How well was your tune? (bad tunings can burn much hotter then need be)

Was the manifold flow good or somewhat restrictive?

Did you use wrap?

And how long/often did you punch it WOT?

Did you use an intercooler? (intake temps can alter exhaust temps, but only slightly)

How efficient was the turbo compressor map?

please don't be offended by my series of questions. I am just deeply curious.

Generally speaking the most important issue is the heat aside from the build. The engine was a 3.4L iron head motor with a crane compucam and the header was not wrapped. All that is required to push the exhaust system to the extreme is sustained high temps. I had a 30 mile commute which meant about 20 minutes of highway driving. When I arrived home at night I would open the decklid of the Fiero from time to time to look at the exhaust manifolds and yes they were glowing even with the combination cast iron manifold and tube system I replaced the burned out manifold with.

16 ga is borderline when it comes to longevity/durability for the kind of heat it's going to be subjected to. Redoing builds gets old very fast as well as expensive in terms of time and money. If you are comfortable with it that's fine, at 500 miles away from home, my welder and my major tools, I can't afford to have major custom part failure. You are wise to use a support brace for the turbo.

Extra supports for the turbo are not needed unless you don't know how to weld. I felt comfortable putting nearly all my weight on the turbo flange of my crossover once it was all together, I doubt a 20lb turbo is going to hurt anything. Not to mention, I can't think of a single car that came with supports from the factory.

But if you insist, make sure the bracket comes off the engine/transmission, NOT the frame/body of the car.

That really depends on the setup. The weld is generally the strongest point on the system so the breaks occur elsewhere. The turbo sunbird came with a brace for the little T25 turbo it sported and that still didn't stop the tubular manifold (the only production turbo GM car I can think of that came with a tubular manifold for the turbo to hang from) from cracking. They fixed that problem in the later cars with a cast iron manifold which most turbo cars have instead of a tubular exhaust.

He's going to use an expansion joint which means only one side of his cross-over will serve as a rigid support for the turbo and that's another reason to consider a brace. I don't have a brace for one of my twin turbos but then I used 14 ga steel and the turbo without the brace is a few inches away from the cylinder head and doesn't have much leverage to create a problem.

Stainless or 14 ga and brace it.

[Schmieder]

Ok, I'm going to give in and get 14ga solid steel (not aluminized) for the cross-over fabrication to the turbine.

I will be commuting 1 hour 5 days a week to school. So if there is an issue, I feel better going safe.

Thanks for the advice guys. You may have just prevented a break down miles from home.

[ForcedFirebird]

You also may want to consider some schedule 10 weld els and pipe since you are making such a short run. Its a lot more expensive (specially stainless) but it's extremely thick steel and is easy to weld with a flux core MIG even.

Stainless or 14 ga and brace it.

Stainless will work, but you will still need the thickness. Thin ebay turbo headers have been known to crack and are stainless (ferrous, but stainless, prolly a leaded alloy).

And to build on the note of the welds being poor and cracking, actually it's the opposite. When welding metal together, you essentially create a hardened edge right at the weld, so, the weld itself will not break (unless you only fused the parts together) but rather the metal immediately adjacent to the weld will break - the harder the metal is, the more brittle it is.

We had to heat treat some parts in the shop, then anneal them back so they were strong yet slightly malleable. We accidentally dropped a pce on the concrete floor before "drawing it back" to a softer state and if you never seen steel shatter like glass, it was actually pretty interesting and frustrating since we lost a good part

[RedZMonte]

my x-over solid, no flex.. my turbo is supported by a bracket that bolts to the dog bone mount. the TGP has a factory mount to the trans.. either way works.

[robertisaar]

ever have any issues with the bushings getting cooked out set up like that? that would be the first thing to worry me when it's like that...