Ten Pounds of Shit in a Five Pound Bag - Twin Turbo LS3/DCT Daily Driver

[shainiac]

I got one downpipe finish welded, the other tacked and fitted. What a pain in the ass.
The little tube stub that connects the wastegate to the downpipe is 3/4" long at one point lol.

This was my first real thin-wall stainless project. I did end up getting a backpurge regulator, which definitely helped color and preventing nasties in the welds. I still struggle with being consistent and patient, though.

Once the passenger side downpipe is welded up, I can make the exhaust from the firewall back. The exhaust, charge piping, turbo intake, and oil lines are more or less all that's left.

[Esser]

Very nice, where did you get the v-band with all the meat on it for welding?

[shainiac]

Thanks, the v-bands actually came with the VS Racing turbos. Surprisingly, it still warped and the pilot fits tighter in the turbine than I'd like lol. I've never warped a V-band with a MIG welder and was surprised this one did. If you look at the HAZ, it's not very consistent though. I'm going to try welding in shorter sections and allowing time to cool for the next one.

[Cobranut]

Those welds look GREAT to me.
If I can ever get anywhere close to that I'll be thrilled. 

[shainiac]

Thanks! I'm sure it'd be a lot nicer if I'd had someone professional do it, but I'm happy to be able to say I did all the fab work myself.

[spacevomit]

That's MIG? Nice!

[shainiac]

That's MIG? Nice!

No, that's TIG. All of my previous exhausts/downpipes I'd done with a MIG.

[Esser]

Mine warped a bit too, just draw filed across the top until it was flat again

[shainiac]

Mine warped a bit too, just draw filed across the top until it was flat again

It seems that it's not longer round and the pilot/lip fits really tightly into the bore of the turbine housing. I don't think it'll be an issue sealing, though.

[driftnfb]

Hey man! Sorry if i'm beating a dead horse here..

I really liked your idea about the scavenging of the Crankcase into the exhaust -- so Ive been digging the last couple days. I came across a video on YT () with some decent data with a Twin LS Setup and HP Tuners (MAP Sensor) and it appears the exhaust scavengers are relieving pressure only slightly. GRANTED he is not using a dump like you had which seems to make it more efficient like you documented

Have you considered the GM Secondary Air Pump? 32-3501M https://www.amazon.com/Cardone-32-3501M-Remanufactured-Domestic-Smog/dp/B001H8EMFI.

I guess crankcase pressure is a pretty big issue with other guys and definitely myself... I hate to add another electronic to the system but plan on setting it up on a Hobbs switch from the charge pipe (2PSI)

were you seeping past the front case seal at all from the last setup? Hoping to nip this in the but once and for all

[shainiac]

I can't say I know the vacuum works better than a open catch can. I didn't have the map sensor when I had a catch can. I mostly added them because packing the catch can was annoying and I didn't care for the stink. I also thought that adding vacuum to the oil pan may help with draining the low mount turbos. I did have one turbo that smoked, but changing from an 8AN to a 10AN drain fixed it. The crankcase pressures I'm seeing are pretty acceptable I think. ~2psi at 600+ whp and 3.5" exhaust isn't terrible. Hoping the 4" exhaust I'm building will help. The new LS3 should have less blow by too.

[cholmes]

Have you considered the GM Secondary Air Pump? 32-3501M https://www.amazon.com/Cardone-32-3501M-Remanufactured-Domestic-Smog/dp/B001H8EMFI.
 

I'm using one of these on my NA LS1, I've got an oil consumption problem and was hoping it would help; it didn't, looks like I need to hone and do new rings.

But, the throttle response is noticeably crisper with the vacuum pump running. Seems to pull harder up top, too, but I don't have dyno data. OTOH, with new rings it may not help. The TV show Engine Masters has tried belt driven pumps on several engines, sometimes it helps, sometimes not.

I've got mine setup on a vacuum switch that turns it on below 5" manifold vacuum. It can definitely pull a good vacuum, right at 5" at idle, even with the dipstick out. Drops to 2"or 3" on a long full throttle pull.

I've pulled a few from Pick-N-Pull, and I pull the rubber cone covering the motor off to check it. Be aware some of the rebuilt ones have a small, WEAK motor. The original motor is fairly big, draws a solid 10-12 amps, and runs HOT, so you shouldn't run it continuously. Leave the rubber cone off to help motor cooling. Grannie's speed shop has a good write-up about them.

[freeskier7791]

Does that smog pump pull enough CFM to make a difference?  I have exhaust scavenge on my drift car but still popped a valve cover seal the last time I took it out, no issues driving on the street though, sustained high load high RPM seems to build crankcase pressure quickly.

[freeskier7791]

Have you considered the GM Secondary Air Pump? 32-3501M https://www.amazon.com/Cardone-32-3501M-Remanufactured-Domestic-Smog/dp/B001H8EMFI.
 

I'm using one of these on my NA LS1, I've got an oil consumption problem and was hoping it would help; it didn't, looks like I need to hone and do new rings.

But, the throttle response is noticeably crisper with the vacuum pump running. Seems to pull harder up top, too, but I don't have dyno data. OTOH, with new rings it may not help. The TV show Engine Masters has tried belt driven pumps on several engines, sometimes it helps, sometimes not.

I've got mine setup on a vacuum switch that turns it on below 5" manifold vacuum. It can definitely pull a good vacuum, right at 5" at idle, even with the dipstick out. Drops to 2"or 3" on a long full throttle pull.

I've pulled a few from Pick-N-Pull, and I pull the rubber cone covering the motor off to check it. Be aware some of the rebuilt ones have a small, WEAK motor. The original motor is fairly big, draws a solid 10-12 amps, and runs HOT, so you shouldn't run it continuously. Leave the rubber cone off to help motor cooling. Grannie's speed shop has a good write-up about them.

I think Grannys put a brushless motor on one?  most larger RC motors would run great on 12v.

[cholmes]

As to whether it will make a difference, only way to know is to try it. Install a boost / vacuum gauge connected to the crankcase and see what you get. For maximum vacuum, make sure the engine is sealed up everywhere except where you connect the vacuum pump, so no valve cover filters, etc.

If you want to pull a little fresh air to get moisture etc out of the engine case, you could put a small bleed hole (maybe 1/8" to 3/16") on the opposite valve cover from the one you have the vacuum pump connected to. I've done this using a lawn mower fuel filter as the bleed hole, didn't reduce the vacuum level at all on my engine, but did pull moisture out, especially when the engine was cold. Verified this with clear hose to the vacuum pump.

Grannys did talk about using a brushless motor, don't know if he ever did, I keep meaning to play with it, just haven't gotten around to it. I think it's a great idea for long term reliability.