Drew's MegaCheap homebrew 3b turbo thread

[amaurer]

On the 25th of this month I'm moving and giving up my flat sealevel commute for a 2000ft daily climb... so I need a turbo on my BJ42 right quick! I need to move quickly, and I don't want to spend a lot.

Granted, the cheapest way to do things would be to do a manifold flip with a junkyard turbo, but I don't like where that puts the turbo and I struck out at the Pick N Pulls near me.

Instead I'm going to try to find a nice middle ground between simple and optimal while spending as little money as possible.

Parts have started to arrive:

1) My turbo of choice. This is a chinese knockoff of a Garrett GT25 - its got a T25 flange, but instead of the 0.64 A/R turbine it has a 0.49 A/R turbine. I don't want to step into the turbo sizing debate, but that said, I have a feeling this is going to be close to the perfect size for a 3B. Turbo is a CXRacing TRB-GT25, price was $230 new+shipped when buying from their ebay store.

2) My flange. I posted the dxf file for this in my other thread (https://forum.ih8mud.com/diesel-tech-24-volts-systems/418145-3b-exhaust-flange-drawing-cad.html), I have my go-to waterjet guy cut it in 0.5" mild steel. For what its worth, if anyone in the Bay Area needs waterjet work I highly, highly, highly recommend Mark at Triton Waterjet (Triton WaterJet - Water Jet Cutting and Abrasive Jet Machining, Northern California) - he does all of my gauge bracket products too and is awesome to work with. I s***-you-not, I sent him the file on Monday, accepted the quote on Tuesday, and got the UPS package with the flange on Wednesday; unbelievable! Price for the flange, inc material, $70.

 

[Doug384]

I'll be interested to see just how durable your cheap turbo really is. There are many horror stories out there about these Chinese knock offs. Are any of them successful? How come a name brand turbo sells for close to $2000? I think that we collectively are just telling ourselves a story when we choose to purchase this off shore stuff that is ridiculously cheap. I am guessing that it will be like so many of the auto parts that are produced there. They work for a while then... What happens if it sheds turbine blades into the intake of your head? Rebuilding the cylinder head with new valves and guides, replacing scored cylinder liners... whoops may as well do the pistons too, could get sort of pricey.

 

[amaurer]

Yep, its a risk. Though I would say that 99.99% of the complaints on the web concern seal and bearing issues; I didn't see anything about total catastrophic failure.

But don't worry, I'm happy to make my failures public, if this thing grenades and trashed my junk you all will be the first to know... with pics!

 

[slowandsteady BJ]

Go for it man! I'm excited to see how this works. I think there is a guy on here running a knock off turbo and has been for many miles now. Also, at moderate boost (10psi) levels you have a better chance of that turbo giving you warning signs before it dies, just keep an ear out for it complaining.

When you get your T's and Elbows.... post a pic pf how they fit on that flange, I'm worried you might need a bit more meat around the edges near the bolt holes. (nothing more weld wont fix though)

Mine was close....

 

[amaurer]

When you get your T's and Elbows.... post a pic pf how they fit on that flange, I'm worried you might need a bit more meat around the edges near the bolt holes. (nothing more weld wont fix though)

Mine was close....

I don't want to spoil the surprise, but that won't be an issue - this is a MegaCheap build, no tees or elbows.

 

[slowandsteady BJ]

I don't want to spoil the surprise, but that won't be an issue - this is a MegaCheap build, no tees or elbows.

Oooo... can't wait to see what you are up to.... keep the pics commin.

 

[seapotato]

megacheap....I like.

I once turbo'd a 3b with a turbo I got in trade for a cheeseburger....

 

[baxter650]

Run one of their cheepo intercoolers as a "NET" for when or if it grenades.

 

[gerg]

I cant see a chineese turbo being any worse than the 30yr old bagged on turbos I have run in the past. Just run good synthetic oil and dont over boost it.
g

 

[PERUVIAN]

bummer.. i thought with all the posts.. there was more photos and details of the actual install.. let us know when its done!

 

[amaurer]

So impatient! I was going to do a running log kinda thing. The whole thing will be finished by Oct. 25th, come hell or high water, thats not too long to wait.

Anyway, some more material came today:

-$12 of mild steel 2x2" square tube plus a short length of 1/8" thick flat stock

Behold the quickest, simplest, (worst?) 3b turbo manifold EVAR. I've going to cut round holes in the square tube and then weld the flange over them. Turns out a 1.75" hole, which is the biggest that fits in 1/8" wall square tube, juuuuust clears the opening of the 3B ports.

 

[jake2far]

Very nice, two questions where are you going to place the welds with no stand offs between the head flange and the square manifold? Most turbo mount flanges are welded at an angle for ease of install how does this configuration line up the exhaust, oil lines, and intake piping?

Jim

 

[slowandsteady BJ]

I love it! Lookin great.

Can you "clock" that turbo you got there?

 

[Christian]

Subscribed, your stuff is usually cool. clean and innovative, so I can't wait to see where this goes, Thumbs Up!

 

[ForealBoreal]

I am stoked to see this turbo job.
I want a total cost at the end of it too drew!

 

[PERUVIAN]

sure we can be patient..
Are you going to weld around the interior of the ports?? or just around the exterior.. is there any risk of rust / corrosion / flaking between the flange and the tube long term that can then get into the intake area? and pass through the cylinders.. just a thought.. maybe crazytalk.. maybe worried about nothing..

 

[amaurer]

Very nice, two questions where are you going to place the welds with no stand offs between the head flange and the square manifold? Most turbo mount flanges are welded at an angle for ease of install how does this configuration line up the exhaust, oil lines, and intake piping?

Jim

a) I'm going to weld around the outside perimeter of the flange.

b) I'll mock it up in the next few days, fingers crossed!! I'm prepared to add a standoff with an angle built in to the turbo inlet flange if necessary.

I love it! Lookin great.

Can you "clock" that turbo you got there?

I'm hoping so - real GT25's can be clocked easily, and this one appears to be set up similar with a clamping band on the turbine side and a snap ring on the compressor side. If it can't be clocked I'll have to build in some angle at the turbo flange - I'd rather not, but I bought some extra material just in case.

sure we can be patient..
Are you going to weld around the interior of the ports?? or just around the exterior.. is there any risk of rust / corrosion / flaking between the flange and the tube long term that can then get into the intake area? and pass through the cylinders.. just a thought.. maybe crazytalk.. maybe worried about nothing..

Just around the exterior. I dunno if its a risk; this is my first time, I'm a cheapy-manifold-virgin. I don't think it'll be a problem, if it does shed rust I don't think it'll shed huge flakes. A bigger risk would be rust buildup warping the flange/manifold... all the more reason to never take this thing off!!

 

[amaurer]

Skipped happy hour so that I could be trusted with power tools and got some work done.

Pics #1 and #2 show the turbo in roughly the position and orientation it will be in assuming that I build the manifold in the simplest possible way: without any angle on the turbo inlet flange and with said flange centered on the manifold. Some thoughts:

• Its hard to see, but the compressor inlet is actually well above the alternator, which is both good and surprising given that my turbo will be lower than most. However the banjo bolt for the vacuum pump connection has a funny little heat shield built onto it which interferes with the turbo - the solution is to just rotate the banjo so it points towards the fender instead of the firewall.
  
• The inlet is slightly tight to the stock airbox (which I will not be replacing). My manifold will move the turbo 0.5" closer to the block than it is presently, so I don't think this will be an issue - I'll either use a tight cobra-style elbow to route the duct upwards, or run a flexible duct underneath the airbox.
  
• I think I might not clock the turbo afterall - doing so would mean I have to make a new wastegate bracket, which would contradict my MegaCheap philosophy. The compressor is positioned almost directly opposite the inlet venturi, so I'll just use two 90deg elbows.

Pic #3 is the result of 5 deafening minutes with the angle grinder.

 

[amaurer]

My big fancy drill press is not fancy enough to have variable speeds, apart the five or so speeds you can achieve by moving the belt to a different pulley... turns out the lowest speed it can achieve is 650rpm, which is wayyy too fast to cut a 1.75" hole in 1/8" steel.

I tried to cut them with a cordless drill. Um, no.

So I'm left making these holes on the smallest machine in my garage because its the only one which can turn slow enough - the 1/5 HP CNC mill I use as an engraver for my knob business. Doh!

Anyway, here are some shots of the hole cutting, and the finished product showing how a 1.75" hole lines up with the 3B ports. I may use a die grinder to clean up the very minor overlap at the corners.

... or I may not.

 

[slowandsteady BJ]

Lookin sweet there Drew!

I know its too late but check out this guys flange....

I actually met this lad yesterday and had a look at his setup. It was very nice indeed and low buck.

https://forum.ih8mud.com/70-series-tech/408838-turbominis-1986-cdm-bj70-turbo-project.html

Hope this gives you ideas...​