Helloo, me again. I thought i'd start this build as a new thread, rather than adding to my previous war and peace novel.

I've been playing about recently with the TVS 1320 supercharger, I built a hotside kit using the one found on the Audi V6s - these have proven quite popular, already got a couple more on the go. This kit recently made 302bhp / 277whp / 254lbft and lives on a drift car here in the UK. Stock engine apart from some forged rods.


They start life out in a big casting with integral intercoolers on either side to feed the 2 banks of cylinders, but you can machine them down to make a more usable unit for an inline 4. I had thought about adapting one for use coldside, but the main issue is any coldside mounting is going to need to be welded on to the outlet, and I'm not entirely sure it will be strong enough for a coldside application. I weld on a flange for the hotside setup, but it only has to hold an outlet, not the whole weight of the charger.

The TVS 1320 also comes on the Lotus Exige / Evora, and people regularly upgrade these to the TVS1900, so you do find the Lotus (Harrop) TVS 1320 coming up for not too bad money. They are not without issues, namely the long snout, the inlet points the down not up, and the bypass is possibly on the wrong side of the supercharger. But they do have a proper outlet with fixing points and a sealing flange. So I bought one.


The intention is to do the same as my previous Autorotor and TVS900 setups, so Laminova water to air chargecooler, cnc manifold, but I plan on updating the ECU to something more modern and use a DBW throttle. I miss the extra poke the TVS900 kit had, but I also am not intending to go super crazy, because I want the car to live on trackdays and I am currently intending on sticking with the 6 speed. Looking to make about 400bhp / 300lbft, somewhere in that region.

I have started surgery on the supercharger, inlet is removed, I will fabricate something onto the back of it for an intake. Pulley is off to allow for the shortening of the snout but already found it doesn't fit on my lathe, so will have to come up with something there, either take into into the works toolroom or do a split snout like the Autorotor.


Not going to be a super speedy project but I'm looking to get it running on this setup for next years season. I was planning on fixing some rust and dents this winter but this seems more fun.

 

With all the stuff you try, ever considered machining a new snout? The snout always seems to be the problem with these retrofits.

 

It is a potential Ted. I saw instructions from Warpspeed on miata.net on how to shorten these snouts and it seems fairly straightforward with the right tools, so I will go for that first. The gearbox case is too big to swing on my lathe but I think it will go on my rotating table on the mill. If not backup option will be machine my own.

The Audi TVS snouts are pretty nicely sized to be honest, the Lotus one here obviously way too long.

 

The snout came apart very simply in the press. This allowed me to take a look at what I was dealing with shaft wise and snout wise. The snout presented an issue in that it was not a uniform cylinder inside. There is a gulley along the bottom of it, which means if I was to simply cut the snout down and then size the new end to fit a bearing, there would be a hole under the bearing. I did not fancy trying to weld up the gulley as I would need to fill about 25mm of length to give room to create the bearing and seal seat, so a different approach was required. First of all I took measurements of where the drive coupler sits in relation to the mating flange and checked depths of bearings etc so I can translate the measurements to the new length when required.

about 30mm behind my target length (100mm) the gulley of the snout ended, and there was a sort of wall that then behind it had the spring seat and rear bearing geometry. So I sawed through the snout at this point, and then set the shortened snout up on my rotary table on the mill. I machined the cut flat then machined a receiving collar of a set diameter 5mm deep. I then made the front bearing housing as a separate piece on the lathe. The back of this part has a corresponding receiving feature that centres it on the snout. The front of the part has an undersized recess for the new bearing and seal. I then cleaned everything up and welded it together. I will take the snout to the machine shop and get them to cut the front bearing recess to final size, centred on the rear bearing housing so everything is perfectly straight and eliminates any movement from welding or lack of precision from the rotary table (it is good for achieving tight tolerances on diameters, but I find it is not so accurate in placing that diameter in concentricity with an existing feature, not as accurate as the lathe anyway, which is too small). I thought I had taken pictures of this process but apologies, I was mistaken. Hopefully my description makes sense. The pictures below are missing the rotor pack as everything is dirty and full of swarf but the supercharger size is certainly looking more manageable.


I'm undecided what to do about the shaft. I'm not entirely sure what the spring does if I'm honest. It looks like something to do with preload but I am doubtful it does a huge amount vs the press fit of the bearing, but I'll keep it. I kept the seat for it in the snout. The required length works out that the end of the shaft would be just under the enlarged section of the old bearing seat. But this thinner section is not a regular size and would be too tight to be a press fit for a 17mm bearing. If I had the shaft ground down to 17mm, that could work but the material removed would not form a big enough step to act as a positioning feature for the new bearing. I could make a press fit sleeve or section to give me that geometry, but I think I would have a hard time making it on my lathe out of the sort of material it would need to be (4130, EN19 etc etc). Particularly sizing inner hole for a press fit over a reasonable distance in that sort of material. So, long story short I think I am going to make a shaft from scratch. I will rough out all the features and then let the machine shop do the final grinding to size for the bearings and drive coupler press fits. I am trying to find some EN19 in annealed form with the idea to the have it hardened post machining but I haven't found any yet, so I may just have to go slow with some hardened stock. This is the next step to work out.



I have designed the manifold and chargecooler in CAD now. A friend is 3d printing a test manifold for me to check clearance, particularly with the injectors and fuel rail. I think I may get away with the bypass underneath, inside the chassis rails which would be a bit of a win.

 

Legit.