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Twin Turbo 3800 K2500

Mattstrike

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Can't find/recall if I shared this here already...

Yes. I am the only living person in the world to have this:


Also, not sure why I can't see this on my computer but it works fine on my phone...

My twin turbo series 1 3800 in a K2500 HD pickup is finally running. Just needs a tune to delete VATS, fix one coolant leak (timing cover cracked at the upper bypass that had to be plugged to make it work RWD-ish), and that's about it!.

Video makes it seem loud, but the clacking noise is just the fucking lifters that need to pump up after sitting idle for 4 years. Odd how a smartphone makes something quieter than pop corn popping seem like it's going to bring the house down...
 
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Bru

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Hmmm, no video but I'd like to see more. Sounds wild. Upload to YouTube?
 

Spivitz

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Video needs to be edited to public
 

Yaj Yak

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yeah i need pics/vids of this thing
 

ilikemtb999

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I'd like to see this as well.



Also are you implying someone that died has already done this?
 

b4black

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Not sure you're the only one in the world. I'll have to double check, but I believe there are at least two, maybe three of these running around in Latvia. And another in Argentina.
 

v6buicks

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How are you liking this set-up? I overpaid for an '88 C1500 with a 5.7 which now has a blown 700r4 and oil coming out of the exhaust. The L36 in my garage and a 4l60e might go in there if I can ever finish my Camaro.
 

Mattstrike

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I'll tell you one thing - I hate hate hate the 700-r4 with the stall converter. I'm either switching to a NV4500 or a 4l60e or 4l80, haven't put much thought into it other than how I hate the 700-r4 lol.

The 3800 is enough to get this truck moving just fine, though it won't be able to pull a huge trailer without boost. I think the stall converter revs it unnecessarily high at the moment too.
 

Mr_Roboto

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Yeah, you want stock as a rock with the increase in weight at most. Perhaps even tightened or one out of a heaviest vehicle that came with such a configuration. Not sure there's a lot of options for that though. 3800 RWD wasn't exactly a common platform. Do the 4T60E converters worth with a 4L60E?
 

Mattstrike

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I made this, so my transmission options are a lot more forgiving:
 
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v6buicks

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Does it still have the stock governor in it? I'm not an expert in automatics, but I would think that the higher stall converter and stock governor could be getting you the response you want from the engine but crappy shift points. School me if I'm wrong though. I'm trying to get better with this stuff.
 

Mr_Roboto

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Very cool, looks like you even kept the drivers side starter.

What are you doing for a converter right now? You said stall converter, but hey that could mean a lot of things. A stocker is $200 or so for a reman. S-10 converters are about 2200 RPM, an Astro Van is about 1600 RPM and getting into the bigger stuff you'll be at about 1200 RPM.
 

Mattstrike

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My converter is custom, fits the v8 input shaft and has the v6 front end, and is 3k stall. I don't know why I let myself get talked into that high of a stall. These turbos spool up right away, but I figured the guy that does torque converters every day knew better. It makes the shifting feel like garbage.
 

Mr_Roboto

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If it's custom just take the hit and tighten it up.
 

Mattstrike

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Yeah, that's the debate. Grab something newer, computer controlled from the yard for $50 and swap it, or spend a bunch more money on the converter and be stuck with the TV and the cobbled TCC and NSS wiring stuff that should be working but isn't, or screw it all and get a manual.
 

Mattstrike

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Took the truck for a drive a few weekends back. First time on a long haul; 360 miles round trip towing a trailer the whole way.

I'll consider this the first real shakedown run since the swap was finished. I wanted to see how it would do, what works and what doesn't.

This was my view for most of the trip:


As with any project, some things go according to plan and others try to leave you stranded on the side of the road...

Having never towed with a gas engine with turbos - I'm in uncharted territory. With lighter trailers (empty) it seems like it cruises along just fine, aside from some issues caused by the TCC control strategy that needs to be completely changed. I'm just stoked that the lockup is finally working on the TCC (had to drop the pan and re-trace all the wires to figure out why, trans was from a '90-ish truck with PCM controls). Running out to the west side of the state, towing a 2000# car trailer, it got 17.2mpg. Towing a 3000# ish boat it was about 16.5-16.8

First thing I found was that I don't like the EPS setup anymore. It just has a completely dead feeling, and I'm having inconsistent assist from it. It's hit or miss while maneuvering around parking lots - it would cut out randomly. Most likely I'm going to end up with a hydraulic over electric system, going back to the stock gearbox and finding a standalone pump from like an MR2, what other options do you guys know of? No, belt driven pump is not an option, I need power steering assist when the engine is off.

Next is the TCC strategy. The series 2 PCM can't control the on/off TCC in the 700-r4 from what I'm told. Is there a way to make the (98 grand prix) PCM control the TCC, which needs an on/off +12v control? If not, I'll have to use a proximity switch on the throttle body to only let it lock in the 5-20% throttle range, no matter what gear it's in, or change the trans to something that bolts in that the PCM can control shift points and TCC (I don't know what trans that would be... 4L65e? Something that won't freak out about up-shifting lol) I don't want to open the transfer case can of worms if I don't have to.

Otherwise I made the first leg of the trip fine, and after fighting with the thing I went out there for, we eventually ended up with this:


4500# of van, 2500# of trailer, give or take. And yes, it pulled it just fine! For a little while, but that wasn't the engine's fault (not relevant to this discussion)

My hydraulically activated (increases brake signal to the trailer with increased brake effort) brake controller from 1979 still works. I had never had a chance to test it out until now, so I'm stoked about that too.

Anyhow...
To people that tow with turbo gas engines - and by tow I mean a loaded car hauler, 38' travel trailer, etc. Does the motor cruise under boost? 1-2 PSI, or more? I would think that monitoring EGT is going to be an issue if it's constantly under boost, as well as heat management. I have a 4-core big block radiator on this, it's over 2" thick and takes up the whole front end of the truck. I didn't notice any issues with coolant temperature, it never exceeded the thermostat set point. Also has a big trans cooler and big (thermostatically diverted) oil cooler. I'm not worried about it getting into boost while climbing hills or whatever, just concerned that prolonged periods under boost (is 1psi ok? 2? 5?...) might drive too high of a combustion temperature and cause piston damage.

This would be just one factor in determining the ideal cruise-while-towing RPM. That is, with the TCC locked. I feel like it's really really close as it is now. 4.10/4.11 gears with a 265-70r17 tire puts 4th + lockup at about 2150rpm. Towing 3000# or so (light) this was on the borderline of making positive pressure while cruising. A few hundred more RPM would have kept it out of boost in 4th + lockup. The endgame for this truck is going to be a 4.56 full float rear (and matching front). That would put 70 @ 2500 RPM which seems like it would be a good balance for cruising and light towing - but it pushes 3rd @ 65 up to 3200 rpm (heavy towing) and that means the turbskies are on a hair trigger because they are all in - 6psi @ 2700rpm - from what I've seen. And it's going to hurt the gas mileage.

I need to get tires for this, my thought was to get a smaller tire (used) to bump the cruise RPM up and test it out, rinse and repeat, to find the ideal ratio before taking the plunge on the full-float and new LT tires. But I'm not sure if I'm overlooking any other issues from running constantly in low boost or if that's really a problem. If it's just a question of thermal management, and the EGT says it's ok, then I don't need to make any changes.
 

EmersonHart13

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Thanks for the update, this project is awesome.
 

Mook

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Not sure how I missed this. Very cool.
 

PANDA

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wow

anymore pictures of the setup?
 

Mook

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Ya seriously. More pics and vids.
 

Mr_Roboto

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Glad to hear she seems to be running well. There's a reason that semis ran large A/Rs when they didn't have gates. They can be fairly finicky about the tuning of the converter, turbine and gearing. The mileage seems to be really decent though even towing. You're doing better than a lot of people with small blocks I'm sure.
 

10sec

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I am with Mook and am unsure how I missed this, but that is freakin' awesome! You do some of the weirdest awesome shit and I can't get enough of it. (y)(y)(y)
 

Mattstrike

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I've got a lot of the in-progress stuff in my build thread (link in my siggy). Most of it is stuck in the photobucket vortex of death and I haven't had time to migrate all the old photos to imgur yet, but these sum it up pretty good I think:







Lots done to the truck: The entire interior was wrapped with faux suede, though it didn't take long for the dash to fade from UV exposure. Seats are from a 97-ish GMC, compass mirror, 1200W power inverter (so I can run my electric chain saw), rear disc brakes, completely custom wire harness and power distribution. Lots left to do - needs a subwoofer, I want to make an organizer for the space behind the seats for tow straps and such, needs winch mounting provisions and wiring, I already bent the front tow hooks, need to finish the interior door panels, I want to box the frame, finish body work to the cab, find a new bed from down south, add an intercooler, and the list goes on.
 

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