One Piece at a Time: My 1985 Diesel Suburban

[AgDieseler]

...a huge down pipe on a 6.2 isn't necessary, there's plenty of duramax engines out there putting out 500+HP on a 3". 4" is nice but definitely overkill.

Yeah - 3” is plenty on any 6.2/6.5 operating under 4,000 RPM (99.999% of applications). Smooth transitions and clean inside radius bends are where I focus.

Someday I want to talk turbo with you. I want/need something different for my crew cab that doesn't build heat as much.

Of course. Lots of cost effective options beyond the GMx turbos, and I will develop and share some Holset opinions in the near future.

Consider thinking about an intercooler, too. The two really can’t be separated when talking about a working 6.2/6.5. It’s a systems approach to power and heat management.

I do? Umm...sure. You're probably right. But I haven't even seen it yet!

I despise Siri’s autocorrect. She’s so bossy.

David

 

[KirsL]

Someday I want to talk turbo with you. I want/need something different for my crew cab that doesn't build heat as much.

The biggest issue with the GMx turbos is since they have such a small exhaust housing, which allows for super fast spool up, holds in a ton of heat. The drive pressure ratio on a GM8 turbo is 2:1. While an hx40 or A-team turbos are around 1.25:1 drive pressure ratio. Which means instead of holding the in the engine it goes out the exhaust.

It also will help with maintaining more consistent coolant temps when under heavy load.

 

[GWeakland620]

The biggest issue with the GMx turbos is since they have such a small exhaust housing, which allows for super fast spool up, holds in a ton of heat. The drive pressure ratio on a GM8 turbo is 2:1. While an hx40 or A-team turbos are around 1.25:1 drive pressure ratio. Which means instead of holding the in the engine it goes out the exhaust.

It also will help with maintaining more consistent coolant temps when under heavy load.

Supposedly Quadstar is the best aftermarket turbo out there now. Tons of great reviews from dudes putting a whoopin on these things.

https://quadstartuning.com/collections/turbochargers-parts/products/super-54-turbocharger-kit

 

[KirsL]

Supposedly Quadstar is the best aftermarket turbo out there now. Tons of great reviews from dudes putting a whoopin on these things.

https://quadstartuning.com/collections/turbochargers-parts/products/super-54-turbocharger-kit

I forget about them some times since they're geared more towards the DS4 engines vs the mechanical. That is a very nice turbo, no intercooler needed either. Not cheap though. But if you want to play you have to be willing to pay.

 

[AgDieseler]

I like the way that fits, especially with the oil drain kit - one more detail made easy. Holset has some nice interchangeable parts and housings, though I’m suspicious of the necessity of billet wheels on our junk.

David

 

[AgDieseler]

Only had an hour in the shop, so I prepped for tomorrow, which is all about wastegate fitment.

Final offset - 1.75”. Parts arrive Wednesday.



Put the feeler gauge away. The alternator fits. Barely.



I’ll trim the old wastegate bracket, and there will be about 1/8” clearance.

David

 

[AgDieseler]

Worked with a friend to get the wastegate mount welded.









Even at this angle, the rod can fully actuate the wastegate and should have no problem relieving backpressure.

It’s now off to the turbo shop for rebuild.

David

 

[GWeakland620]

You still run a vacuum actuator? But I thought everyone wanted to get rid of those?

 

[AgDieseler]

You still run a vacuum actuator? But I thought everyone wanted to get rid of those?

That’s a pressure side actuator. It’s normally closed, unlike the factory 6.5 actuator that’s normally open and is cycled with vacuum. This is just a modified factory piece from Holset.

David

 

[AgDieseler]

And no sooner do I get back to the house than I get a call from Majestic Turbo.

Everything is in good shape. It just needs the standard seals and bearings, they can sand the tiny chips out of the leading edge of the compressor wheel. Also, they found a small leak in the actuator, so they’ll replace that, too. Looks like it will be ready tomorrow, and I’m not into this for much at all.

David

 

[AgDieseler]

Friday nights are for turbos.



David

 

[KirsL]

My hx40 install for comparison.

 

[AgDieseler]

Grid heater?

David

 

[KirsL]

Grid heater?

David

Yes, from the days when I was still in New Jersey. This engine is a stock compression 6.2 so I should never need it. But I left it as a back up incase the glow plugs ever fail to work. Or I make a trip to somewhere stupid cold.

 

[AgDieseler]

At this point in the build, nothing is easy.

While the turbo is stabbed and hooked up to oil, a few details remain. This short jog is too tight, and I’m going to have to pull the intercooler to push the inlet about 4” back toward the tank. There’s plenty of room, and it just takes time.



The downpipe is fit and fabricated. I decided to stay focused on getting the turbo up and running, and have deferred the time and expense of a fancy-pants stainless oval downpipe for later. I repurposed some of the Banks 3” pipe, massaged a few dimensions to get the crossover v-band in a better spot, and build the transition cone from new stainless stuff from Vibrant. They make some really good gear.



It took one day to fit and fabricate, and I got up early this morning to weld it. I’m really digging stainless right now.



The steel stuff gets wrapped and sealed, and I’ll hook it up tonight.

David

 

[AgDieseler]

Busy night, so no photos.

She’s back up and running. After closing the laptop, I headed straight out to the shop, and:

• wrapped and sealed the downpipe
• reassembled the exhaust (v-band clamps are glorious and can also be frustrating)
• powered everything up
• smoke check
• primed the oil line to the turbo

With the pink power wire reconnected on the IP, the engine cracked off right away. I ran it for just a few minutes to check for leaks, fiddled with the throttle a bit because I wanted turbo sounds, and shut it down.

Everything looks good. Goal achieved. Pulling the intercooler tomorrow.

David

 

[AgDieseler]

Just pulled the charge pipe off the intercooler, and it’s like the Exxon Valdez poured herself out. It’s just the collection of oil vapor from the CDR over two years, but it’s time to install a separation canister in that circuit.

Ordered:


David

 

[AgDieseler]

Intercooler, out. Current setup:



Looking to trim about 3.25”



Build back tomorrow. I’m taking every minute I can get before work, during lunch, and after.



David

 

[campfire]

Yay pictures!

 

[GWeakland620]

How close do you live to work?

I’m about 12 minutes away, and it’s just close enough and far enough away for me to be late back to work when I try to do something at home on my lunch haha.