Making my own twin turbo 350Z
 

I've got a 350Z that I use purely as a drift car and whilst I enjoyed it in NA form for my first year of competition, I'm moving up a class next year and figured I could do with some more power... plus I wanted a big project to sink my teeth into over winter. So I decided to go twin turbo but rather than buying a pre made kit I thought I'd try and do it all myself.

So I'll be making the exhaust manifolds, intercooler end tanks, all the intake piping, oil lines etc etc. There's probably plenty of people on here that have done something similar but I've never made anything like an exhaust manifold in my life and just taught myself to weld through watching youtube videos within the last year. I've also never done an FI conversion myself, so just figuring out all the parts I need to make this work and where everything is going to go was a challenge as well. I'm basically saying all this so that you'll hopefully go easy on me when you see the fabrication and design choices :)

I'm using 2 x Garrett GT2554R turbos as I'm not aiming for crazy high power (rough power goal is basically between 400 and 500 bhp). I want to keep it as responsive as possible. Engine will be built with forged rods and pistons with a lower CR.

I've been making videos of my progress so far but figured it would be good to also get a build thread going on here so that it is something other people can find from searching, just in case it helps anyone else doing something similar in the future. If anyone wants to check out the videos, they're on my channel here: https://www.youtube.com/playlist?lis...Ca3s3zwWS0uOy9

I've spent the last few weeks making the exhaust manifolds and external wastegate setup, so here's some pics of that:

https://cimg2.ibsrv.net/gimg/my350z....2ea9eec6a4.jpg

https://cimg8.ibsrv.net/gimg/my350z....101cb5f97b.jpg

https://cimg1.ibsrv.net/gimg/my350z....480099da9b.jpg

https://cimg0.ibsrv.net/gimg/my350z....0a07b342cf.jpg

and this is all I've got done of the other manifold so far:

https://cimg5.ibsrv.net/gimg/my350z....be01677cd5.jpg

https://cimg8.ibsrv.net/gimg/my350z....55a38f8064.jpg

Yes the turbos and wastegate ended up pretty low, but I'll have a skid plate underneath that should protect them. One thing that is going to be even lower is the reservoir I'll be making for both turbo's oil to drain into (then scavenger pump will send that back to the sump) but again hopefully I can protect it well enough. Also planning to make a header tank / swirl pot for the coolant system (thanks to @djtimodj for advice on this) but feel free to offer suggestions for things you think I should look out for being the noob that I am :)

I'll try and keep this thread updated with progress fairly regularly, but like I said there's also videos every week or two on my youtube channel.

Locating the t's that low will be a + for lowering your center of gravity. You gotta add weight for the desired power, so might as well make it work for u if possible.
You gonna relocate the battery to the back?
You gonna do some form of heat shielding to keep the heat off the transmission?

Thanks :)

I'll be running one O2 sensor after the turbo on each side. Those sensors on each runner will be EGT sensors to help tune individual cylinders (suggested by my tuner).

I'm not crazy about where I have the external wastegates either, but I couldn't find anywhere better. Original plan was to have them on that straight section after the merge collector, but they're just too awkward to fit round there. I go into more detail about 3 mins in to this video:
As for why I even have external wastegates, there's 2 reasons. Firstly the actuator for the internal WG sticks out from the side of the turbo housing quite a lot and made it even harder to find a good space to mount the turbo, and secondly because everyone seems to agree that external ones perform better overall. Bonus reason is that I wanted to see what its like with a screamer pipe lol

Will definitely have a flexi section of exhaust in the downpipe and there will also be a brace to support the turbo that has rose joint rod ends to allow some flex.

I couldn't bring myself to go full solid engine mounts (after having a solid transmission mount in another car and hating it) but I have gone for stiffer mounts from HardRace so hopefully they help a bit.

Still considering relocating the battery to the back, but yeah I'll be using a lot of heat shield all over the place to as the manifold and turbos are so close to everything. Getting the manifolds coated with Zircotec coating and that lowers their temps by about 30 percent, but then I'll also put heat shield and gold tape on everything nearby

Not that I know everything but I'm not sure (either) how he plans to tune on EGT - Only thing I can think is that he's looking to make exhaust temps consistent between each individual cylinder - but that's purely speculation.

I hear ya on waste gate location - space constraints are always tough.

What platform do you (anticipate) / are you going to tune with?

Do you always tig with gloves on? I find it hard to grip the torch and filler ...

Nice vid too ... great thread thus far!

Yeah EGT is used to balance each of the cylinders. I guess if they're all getting the same AFR then they should all be the same temperature, within a certain tolerance. Like I said there will still be an O2 sensor further down as well and that's what the majority of the tune will be based on.

I'm using a Link ECU, already got that installed a few months ago in preparation for going twin turbo (and did the AAM fuel return kit and 600cc injectors around the same time as well).

Yeah I always wear gloves while tig welding, but they are specifically advertised as being for tig not mig. They're a bit thinner and more flexible than the mig gloves I've got. Maybe the gloves you're using are meant for mig?

I hear ya (on the EGT) and know that even a 10%-15% swing in AFR doesnt make much more/less power ... your ign timing is much more influential on engine output.

did you get a G4+?

You may want to go higher / bigger injectors before you get too far - depending on how much boost you plan to run? a 600cc injector is only going to mate-up to 8-10psi of boost - depending on your fuel grade (I understand there are differences between our fuels). Is your block built?

I have both MIG and TIG gloves. I still find them to be intrusive. I will wear 9mil rubber gloves to keep the argon smell off my hands - to each their own!

What makes you say that? I'm not understanding the correlation between injector size and boost... unless that's assuming I'm going to be running those injectors with the stock fuel pump? I'll be using a DW350iL fuel pump - after going through all the calculations on the Deatschwerks website long story short it said 600cc injectors would be good for about 605 bhp or something like that. Then a friend also said that on these cars its roughly 1 bhp per cc, so that matched up with what I'd found too. I've got a fuel pressure regulator that will be hooked up to a boost source so it can add extra pressure to compensate. It will be run on Shell V Power fuel which is 99 octane if I remember rightly. Engine will be built yeah, and with a lower compression ratio than stock (think it was 8.5:1 that we're going for)

the correlation isnt necessarily boost but rather horsepower(althought it really is as boost is tied to whp).

Obviously there will be a million factors and seeing that your octane is much higher than ours I ran out of my DW600 making 470whp. Ive heard 1cc per hp and it roughly lines up with what I did when you factor in efficiency. I would bump your injectors up (either now or down the road) and go to a 1.5cc - 2cc per whp especially considering you dont want to run past 80%-85% duty cycle. Your 350lph pump should be good into the 600whp range.

Speaking of - what are your power / boost goals?

to wrap this post (and any future post of mine) please do whatever you like and take only what I have to say as an opinion and not the absolute only way to do it!

Yeah I'm not going for crazy high power or anything for now, I just want it to be as responsive as possible whilst adding a bit more power. Rough power goal is between 400 and 500 whp to start with, so if you say you made 470 whp on 600cc injectors with lower octane fuel than that sounds like they'll be fine for me.

I got the other exhaust manifold pretty much done yesterday (apart from external wastegate part and EGT sensor bungs) so now we actually have both turbos on the car :)

https://cimg2.ibsrv.net/gimg/my350z....c9d09050a1.jpg

https://cimg6.ibsrv.net/gimg/my350z....455a594269.jpg

https://cimg4.ibsrv.net/gimg/my350z....1e9b46d0f7.jpg

https://cimg1.ibsrv.net/gimg/my350z....53748024ef.jpg

Fun vid. Nice welds. Turbo blankets a +. Gonna need some body work now :skidmark:

Nice progress! 400-500 is a good target and with a built block and pump/injector upgrades you'll be good. You can always upgrade down the road too - not like you're stuck.

Spent this afternoon cutting some of the secondary firewall out. Amazing how much extra room it frees up behind the engine. I think I'm going to keep some parts of it near the edges as it seems pointless cutting it out and then having to make a bracket to mount the reservoirs on.

https://cimg5.ibsrv.net/gimg/my350z....2baf483693.jpg

With most of it cut out:


https://cimg4.ibsrv.net/gimg/my350z....d21a31c132.jpg

https://cimg7.ibsrv.net/gimg/my350z....d1b5cdea88.jpg

https://cimg1.ibsrv.net/gimg/my350z....cb4fbb98b6.jpg

https://cimg2.ibsrv.net/gimg/my350z....e3b11cec41.jpg

https://cimg5.ibsrv.net/gimg/my350z....29e398970e.jpg

Looks like an organized operation and I dig the manifold cover.

I've got an exceedingly remedial question if you will? Regarding the 2 large missing bolts, center of the timing chain cover and the one below not shown in the photo. Are they unnecessary? I never could be confident in leaving them out when I deleted the useless pulley and it's bracket. They look like they attach the front to the rear timing chain covers in the FSM yet I've seen them left out on numerous occasions.

https://cimg5.ibsrv.net/gimg/my350z....29e398970e.jpg

no no no cut it all out!!!!

I've only got mine out at the moment as I was using them as the point to attach a bracket to that I lift the engine from. I'll put them back in when everything is finished, but no I'm not 100% sure if they are necessary. Not really worth the risk of leaving them out in my opinion though, as they don't get in the way and not like you're going to ever notice any weight saved from losing a few bolts.

https://cimg5.ibsrv.net/gimg/my350z....34d2f89bd2.jpg

Decided I wasn't happy with how low the turbos were and also how hard it is to access the bolts on the turbo flange that joins it to the exhaust manifold (one of them was literally impossible to get any tool to it) so I plan to add a V band to the straight section of each manifold.

Got one side done over the last few days and also got the second wastegate mounted, so here's some pics of all that:

https://cimg8.ibsrv.net/gimg/my350z....d515e3accc.jpg


https://cimg9.ibsrv.net/gimg/my350z....eafb4fff14.jpg



https://cimg3.ibsrv.net/gimg/my350z....ccf0587bd3.jpg

https://cimg8.ibsrv.net/gimg/my350z....8fd82b1cd3.jpg

https://cimg9.ibsrv.net/gimg/my350z....c0883b165b.jpg

https://cimg6.ibsrv.net/gimg/my350z....18ce00a5c5.jpg

https://cimg9.ibsrv.net/gimg/my350z....e9683c322b.jpg

Finally finished adding the V band to the other exhaust manifold and adjusting things so that the turbo/wastegate sit a bit higher on that side too. There's about 40 mm from the lowest point of the turbo oil drain compared the lowest point of the front subframe, so I'm happy enough with that and will start making the oil drain tank soon.

https://cimg0.ibsrv.net/gimg/my350z....a5015c3c7c.jpg

https://cimg4.ibsrv.net/gimg/my350z....6d41e75c9d.jpg

https://cimg7.ibsrv.net/gimg/my350z....86138b57f4.jpg

https://cimg1.ibsrv.net/gimg/my350z....7f2c2c464c.jpg