VTT Splinelock & GC+ Install Feedback

[jturboawd]

Hi peers, my name is Jay, Long time BMW owner/builder, first time S55 owner. Previous cars are all N54/55. Ive built 5 BMW including S50/52, N54/55. This includes engine builds, PS2, speedtech BW turbos, etc.

2 Months ago i picked up a 16' manual M4 in YAS with 40K on it. Had 91 cali OTS tune, shit exhaust and suspension, AFE intake ARM downpipes, and nice BBS wheels.

I drove it to Houston and ordered the following parts after a lot of review and decision analysis.
- Bilstein B16
- 2.5" piping kit
- Ebay intercooler and hardpipes
- Snow meth with metal lines and stealth tank
- VTT GC+ with spline lock and jordan tune
- Plugs, coils, breaks, lots of carbon parts, seat symbols, etc.

Did it all DIY over a 4 week period on weekends. Working from home, 3 weeks waiting for VTT to send me my turbos. lol

I wanted to provide some generic feedback on the VTT installed parts.

There is a lot of hate on VTT online, and a lot of love. Many records etc. I have watched VTT and the historic Tony-RB debates over a long period of time. What i can gleam from the VTT side is they have some very good ideas but seem to send out serial number 1 items with less testing then a larger manufacturer would do. This leads to issues in rev1 designs. This can be seen in the CG series N54 and the spline lock. I consider there products great ideas that are half engineered. I do not want this to be insulting, this was my opinion before, and it is my opinion now, i still think the design, idea, and package, is what i wanted.

Spline lock: The v2 spline lock is hard as hell. I had it tested to ensure it had a sufficient hardness from metallurgist i work with. The part does not appear to be hardness tested. From what I can see it appears to be 17-4 manufactured from a billet, which means the teeth and spline are softer than the OD sections of the billet. It appears they have been induction or similar heated and quenched, you can see this through the discoloration of these critical sections. The part doesnt not appear to be hardness tested post quench which would be a nice QAQC add. This would add cost, so there is a balance there. Important notes:
- First posted 17-4 corrected is 440 tool steel
- First posted Appears to be hardened through induction heat then quench at teeth and spline corrected 440 fully heat treated to 55-60 HRC.
- Good fit and finish
- Spline has good interference. This is about 100 ft-lbf of load (which could be used to back calculate spline interference if you have good plastic FEA experience). Its important to note you must bottom out, tighten a little, then loosen, then make up per OEM instructions
- Break out is 500 ft-lbf or so
- Make up is 600 ft-lbf using cheater and angle of rotation
- MAKE SURE to align crank bolt capture prior to finishing. You need to hit target torque, check crank capture, and keep turning until you can aligned capture unit.

You will need a BIG ARSE cheater and 3/4" socket. If you are in houston you are welcome to borrow my tools (timing kit, flywheel lock, cheater, engine support) needed.

If you DIY expect 30 hours taking your time, changing gaskets along the way. Remove the subframe and oil pan.

Turbos: The turbo hot and cold side are new, no core charge required. They do open up the hot side restriction, which is nice but not nearly as important as the N55 version. I think this is beneficial above 600-700 HP to make the rods happy, its all about pre turbine back pressure. This was a issue on the PS2 N55 that pure never addressed but is a BIG deal that i chased a long time on my last car prior to moving to speedtech. The housings appear to be value casted from stainless steel. The parts are near OEM but not exactly the same.

Constructive feedback:
- If you send your turbos to pure the wastegate actuators will be the same position before and after conversion. With VTT they are new casting and will not be positioned exactly the same. I HIGHLY recommend measuring the WG opening and making sure its the same after install. This is not in instructions but should be to avoid having to reset with ISTA after install. I did this because im used to it from other turbos.
- Flapper clip: The flapper clip VTT sends you is shit, and the washers make the flapper overly tight. They provide a wave spring which is nice to reduce rattle. I changed this, kept the wave spring, used a high strength C clip, and make sure it was tight but loose enough to freely move. I recommend VTT provide stronger clip and maybe 2 size washers to handle variations in dimensions.
- Rear turbo silicone clearance. The rear turbo silicone reduces restrictions but interferes with turbofold. You cannot use the stock heat shields without modifications (and cannot on rear turbo at all). The silicone interferes with the front turbofold. the silicone does have built in steal wire in this section that allows you to shape it and hold the shape. Its still to close for me. What i did was trim the stock front heat shield. Then i used heat tape. This came out nice. What i think would be more clean would be a elbow or metal pipe.

Pros:
- Well packed
- No shaft play
- Bolted up like OEM except small items above
- Pretty arse turbos

I am still dialing in the turbos with Jordan. What I can tall so far:
- Transient response appears to be very near stock
- OTS BM3 2H tunes work surprisingly well
- Spools nicely, great top end


I am very busy and want to make a build full DIY thread. I just cant find time. I am happy so far. VTT was delayed about 2 weeks, took a month to get turbos. They did respond quickly via email and remained respectful even though i bugged the hell out of them lol. This is my first VTT product. I have installed wild BMW singles and pures and wanted to give my feedback:

If I was in the market for a turbo here is how i rank the following:

Stock: Great for up to 500, 500-600 with e85 but at these levels you are pushing way to hard for me, i like safety as i daily mine and was sick of using e85. great spool, too good for me, we all like different things though. i like good middle and great top, more linear, less EVO like middle (if that makes sense).

Pure: Great choice. You can almost never go wrong with pure. You live with the core charge, great QAQC, high price. Its pure plug and play though.

VTT GC+: Almost plug and play. no core, better value, more top end and higher HP potential, B+-A- QAQC IMO. I wanted the + wheel with no turbofold restrictions, i want pump gas power at lower boost.

Singles or non hybrid setups: LOTS of fitment work and tuning to work out. Can work out great, but expect significant downtime and likely 2X the cost of the above.

[Chris@VargasTurboTech]

Originally Posted by jturboawd

Hi peers, my name is Jay, Long time BMW owner/builder, first time S55 owner. Previous cars are all N54/55. Ive built 5 BMW including S50/52, N54/55. This includes engine builds, PS2, speedtech BW turbos, etc.

2 Months ago i picked up a 16' manual M4 in YAS with 40K on it. Had 91 cali OTS tune, shit exhaust and suspension, AFE intake ARM downpipes, and nice BBS wheels.

I drove it to Houston and ordered the following parts after a lot of review and decision analysis.
- Bilstein B16
- 2.5" piping kit
- Ebay intercooler and hardpipes
- Snow meth with metal lines and stealth tank
- VTT GC+ with spline lock and jordan tune
- Plugs, coils, breaks, lots of carbon parts, seat symbols, etc.

Did it all DIY over a 4 week period on weekends. Working from home, 3 weeks waiting for VTT to send me my turbos. lol

I wanted to provide some generic feedback on the VTT installed parts.

There is a lot of hate on VTT online, and a lot of love. Many records etc. I have watched VTT and the historic Tony-RB debates over a long period of time. What i can gleam from the VTT side is they have some very good ideas but seem to send out serial number 1 items with less testing then a larger manufacturer would do. This leads to issues in rev1 designs. This can be seen in the CG series N54 and the spline lock. I consider there products great ideas that are half engineered. I do not want this to be insulting, this was my opinion before, and it is my opinion now, i still think the design, idea, and package, is what i wanted.

Spline lock: The v2 spline lock is hard as hell. I had it tested to ensure it had a sufficient hardness from metallurgist i work with. The part does not appear to be hardness tested. From what I can see it appears to be 17-4 manufactured from a billet, which means the teeth and spline are softer than the OD sections of the billet. It appears they have been induction or similar heated and quenched, you can see this through the discoloration of these critical sections. The part doesnt not appear to be hardness tested post quench which would be a nice QAQC add. This would add cost, so there is a balance there. Important notes:
- 17-4
- Appears to be hardened through induction heat then quench at teeth and spline
- Good fit and finish
- Spline has good interference. This is about 100 ft-lbf of load (which could be used to back calculate spline interference if you have good plastic FEA experience). Its important to note you must bottom out, tighten a little, then loosen, then make up per OEM instructions
- Break out is 500 ft-lbf or so
- Make up is 600 ft-lbf using cheater and angle of rotation
- MAKE SURE to align crank bolt capture prior to finishing. You need to hit target torque, check crank capture, and keep turning until you can aligned capture unit.

You will need a BIG ARSE cheater and 3/4" socket. If you are in houston you are welcome to borrow my tools (timing kit, flywheel lock, cheater, engine support) needed.

If you DIY expect 30 hours taking your time, changing gaskets along the way. Remove the subframe and oil pan.

Turbos: The turbo hot and cold side are new, no core charge required. They do open up the hot side restriction, which is nice but not nearly as important as the N55 version. I think this is beneficial above 600-700 HP to make the rods happy, its all about pre turbine back pressure. This was a issue on the PS2 N55 that pure never addressed but is a BIG deal that i chased a long time on my last car prior to moving to speedtech. The housings appear to be value casted from stainless steel. The parts are near OEM but not exactly the same.

Constructive feedback:
- If you send your turbos to pure the wastegate actuators will be the same position before and after conversion. With VTT they are new casting and will not be positioned exactly the same. I HIGHLY recommend measuring the WG opening and making sure its the same after install. This is not in instructions but should be to avoid having to reset with ISTA after install. I did this because im used to it from other turbos.
- Flapper clip: The flapper clip VTT sends you is shit, and the washers make the flapper overly tight. They provide a wave spring which is nice to reduce rattle. I changed this, kept the wave spring, used a high strength C clip, and make sure it was tight but loose enough to freely move. I recommend VTT provide stronger clip and maybe 2 size washers to handle variations in dimensions.
- Rear turbo silicone clearance. The rear turbo silicone reduces restrictions but interferes with turbofold. You cannot use the stock heat shields without modifications (and cannot on rear turbo at all). The silicone interferes with the front turbofold. the silicone does have built in steal wire in this section that allows you to shape it and hold the shape. Its still to close for me. What i did was trim the stock front heat shield. Then i used heat tape. This came out nice. What i think would be more clean would be a elbow or metal pipe.

Pros:
- Well packed
- No shaft play
- Bolted up like OEM except small items above
- Pretty arse turbos

I am still dialing in the turbos with Jordan. What I can tall so far:
- Transient response appears to be very near stock
- OTS BM3 2H tunes work surprisingly well
- Spools nicely, great top end


I am very busy and want to make a build full DIY thread. I just cant find time. I am happy so far. VTT was delayed about 2 weeks, took a month to get turbos. They did respond quickly via email and remained respectful even though i bugged the hell out of them lol. This is my first VTT product. I have installed wild BMW singles and pures and wanted to give my feedback:

If I was in the market for a turbo here is how i rank the following:

Stock: Great for up to 500, 500-600 with e85 but at these levels you are pushing way to hard for me, i like safety as i daily mine and was sick of using e85. great spool, too good for me, we all like different things though. i like good middle and great top, more linear, less EVO like middle (if that makes sense).

Pure: Great choice. You can almost never go wrong with pure. You live with the core charge, great QAQC, high price. Its pure plug and play though.

VTT GC+: Almost plug and play. no core, better value, more top end and higher HP potential, B+-A- QAQC IMO. I wanted the + wheel with no turbofold restrictions, i want pump gas power at lower boost.

Singles or non hybrid setups: LOTS of fitment work and tuning to work out. Can work out great, but expect significant downtime and likely 2X the cost of the above.

Thanks for the feedback sir, we appreciate it!

To address a few things.

#1 the crank hub, while we appreciate your speculation on the hub material. You are incorrect on it. V1 hubs were 17-4 and hardened we found this process to be inconsistent, which caused some of the issues we saw with the splines laying down on some V1's. V2 are ALL made from 440C Tool steel (feel free to have it tested it will come back as 440C) The ENTIRE piece is hardened to 55-60HRC NOT the splines only. Each and every hub is hardness tested when they come in at multiple spots to ensure hardness. This testing does not leave marks as it shouldn't as we are using hardness files. You only see marks if you use a hardness machine. The files we use are these (https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1). Very simple, and very effective If the file can dig or scratches the surface the file is harder than material. If the file slides over the surface, and cannot dig. The material is harder than the file. We use the 55, and 60 HRC files, and usually, the 60 will not even grab. Meaning we have achieved at least 60HRC.

As for the inlet fitment on the turbos. When trying to get rid of restrictive factory inlets which sure are packaged tight but leave a lot to be desired expect some compromises. Easy fitment is one of them. The inlets we provide increase flow at least 20% of the stock design, but the trade-off is they are bigger, yes they are more difficult to fit and require tweaking the heat shields, etc. If you take your time, do a little bending or trimming, everything will fit back into place no problems including the factory heat shields.

Outside of those two things, we are glad you are happy with the products, and there is a reason VTT GC's have FIVE stock motor cars in the 9's. The rest of the collective S55 turbocharger manufacturers have none. Flow, and good spool. No magic to it.

[farbmw]

Originally Posted by Chris@VargasTurboTech

Thanks for the feedback sir, we appreciate it!

To address a few things.

#1 the crank hub, while we appreciate your speculation on the hub material. You are incorrect on it. V1 hubs were 17-4 and hardened we found this process to be inconsistent, which caused some of the issues we saw with the splines laying down. V2 are ALL made from 440C Tool steel (feel free to have it tested it will come back as 440C) The ENTIRE piece is hardened to 55-60HRC NOT the splines only. Each and every hub is hardness tested when they come in at multiple spots to ensure hardness. This testing does not leave marks as it shouldn't as we are using hardness files. You only see marks if you use a hardness machine. The files we use are these (https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1). Very simple, and very effective If the file can dig or scratches the surface the file is harder than material. If the file slides over the surface, and cannot dig. The material is harder than the file. We use the 55, and 60 HRC files, and usually, the 60 will not even grab. Meaning we have achieved at least 60HRC.

As for the inlet fitment on the turbos. When trying to get rid of restrictive factory inlets which sure are packaged tight but leave a lot to be desired expect some compromises. Easy fitment is one of them. The inlets we provide increase flow at least 20% of the stock design, but the trade-off is they are bigger, yes they are more difficult to fit and require tweaking the heat shields, etc. If you take your time, do a little bending or trimming, everything will fit back into place no problems including the factory heat shields.

Outside of those two things, we are glad you are happy with the products, and there is a reason VTT GC's have FIVE stock motor cars in the 9's. The rest of the collective S55 turbocharger manufacturers have none. Flow, and good spool. No magic to it.

Hi Chris,

He also mentioned the "Flapper clip" what is your views on that?

[jturboawd]

Chris,

Makes sense on the change. I didnt run chem analysis just confirmed harness. I can confirm i got 58 HRC from my testing.

Hoping to keep dialing this thing in. So far the car is fun and responsive. I am very glad to see a good trainsient response even with the larger GC+ wheel.

I am a subject matter expert on mechanical designs for critical applications in the oil and gas industry. I chose the splinelock for technical reasons as i actually find it superior to the drilled version for complicated reasons. The install is a PITA, but thats not VTT its just the nature of the job lol.

[jturboawd]

On the fitment of the inlet you are correct, the heat shields do fit after some careful trimming. I just dont like how cramped it is. I do however believe it is functional WITH the heat shield in place. Without the heat shield in place i would worried the inlet would fail over time.

I recommend a layout showing people where to trim the heat shields. I have seen this done on other products on other cars. Alternatively VTT could make a prettier heat shield that fits well with the product? Could even anodize it and put your name on it

[Chris@VargasTurboTech]

Originally Posted by farbmw

Hi Chris,

He also mentioned the "Flapper clip" what is your views on that?

We find no issues with the clips we use. They are SS E clips and have been using the same ones for 8 years, on every N54, S55, etc unit we sell. Have never had one fail. As for the shim, we provide one shim, and one spring washer as the customer can tailor the set up to the optimal fit, as believe or not some fit tight with just the spring washer, and clip and some fit loose, so we provide both so the customer can dial it in.

[jturboawd]

Originally Posted by Chris@VargasTurboTech

We find no issues with the clips we use. They are SS E clips and have been using the same ones for 8 years, on every N54, S55, etc unit we sell. Have never had one fail. As for the shim, we provide one shim, and one spring washer as the customer can tailor the set up to the optimal fit, as believe or not some fit tight with just the spring washer, and clip and some fit loose, so we provide both so the customer can dial it in.

That makes a lot of sense. I did not find instructions, etc, so i assumed the washer "shim" was required. When used it is excessively tight on one of my turbos. It could be the case that the clips are fine. VTT sells a LOT of turbos, if you are not heading them fail in the forum and market then its not a issue, im just a overly detailed engineer

I think most M people are not DIYers, i think this will change over time. A good instruction manual for the turbos, how to set up WG, etc, would be beneficial to DIYers.

What i did on the shim was take the washer on a 72" belt sander and flaten it. The wave spring is a nice add since the OEM can rattle. I removed enough height to make it able to freely move.

[theweebabySeamus]

Somewhat unrelated, and a willing admission of ignorance, but I’ve always been curious why there isn’t any issue with the ‘female’ part of the crankshaft failing and cracking from the pressure of metals being compressed when the splinelock is inserted? It’s obviously not an issue, I’ve just always wondered why.

[Chris@VargasTurboTech]

Originally Posted by theweebabySeamus

Somewhat unrelated, and a willing admission of ignorance, but I’ve always been curious why there isn’t any issue with the ‘female’ part of the crankshaft failing and cracking from the pressure of metals being compressed when the splinelock is inserted? It’s obviously not an issue, I’ve just always wondered why.

Definitely a good questions. It's aggressive and an interference fit, but not so much so that the mating material would rupture. That'd be wayyy too aggressive of a fit. There are industry standards for how far to go for torque transmission devices and interference fits. All mech engineering "stuffs".

Chris

[jturboawd]

Ok..... still dialing this thing in.

OTS 2H maps work very well

Jordan maps are just stupid fast

So far all i can say is WOW. clean logs, so fast. I cant believe the clutch is holding, but im not doing digs and the torque is being held at bay. i cannot believe how clean the logs are considering we are on rev 2 already. It took me 30+ revs to get a big turbo N55, same with PS2 on N55 and N54.

I am very impressed with spool and transient response considering size.

Ill post a lot more in a build thread when im done, just sharing impressions. Ill dial in, dyno, and make thread. I need to make sure Jordans cool sharing logs, if not ill post the OTS 2H logs.

[mike@x-ph.com]

Congrats on the new turbos and thank you for taking the time to post a review

[M4XS55]

Originally Posted by jturboawd

Ok..... still dialing this thing in.

OTS 2H maps work very well

Jordan maps are just stupid fast

So far all i can say is WOW. clean logs, so fast. I cant believe the clutch is holding, but im not doing digs and the torque is being held at bay. i cannot believe how clean the logs are considering we are on rev 2 already. It took me 30+ revs to get a big turbo N55, same with PS2 on N55 and N54.

I am very impressed with spool and transient response considering size.

Ill post a lot more in a build thread when im done, just sharing impressions. Ill dial in, dyno, and make thread. I need to make sure Jordans cool sharing logs, if not ill post the OTS 2H logs.

subscribed.

[FriedPiston]

Originally Posted by jturboawd

I am very impressed with spool and transient response considering size.

I can vouch for this 100%. I just got my car back after being down for 13 months, and the first thing I noticed is how the response on the GC+ are very close to factory, especially considering its size. I've been quite impressed with them despite only being on the BM3 OTS Stage 2 ACN91 map for now. I believe the manifold design makes a huge difference over a hybrid setup.

The GC+ definitely has better spool characteristics than the PS2 HF I previously had. I also had a brand new set of KRAS55bi that was waiting to be installed on a built engine project, but I ended up replacing them with the GC+ due to the engine builder being a scam artist. So far, I am not regretting my decision to go with the GC+.

[MR_X]

Originally Posted by jturboawd

You will need a BIG ARSE cheater and 3/4" socket. If you are in houston you are welcome to borrow my tools (timing kit, flywheel lock, cheater, engine support) needed.

If you DIY expect 30 hours taking your time, changing gaskets along the way. Remove the subframe and oil pan.

So how many beers and pizzas should I bring for you to help me with installing the VTT hub?

[luchocamp]

never go wrong with Vargas GC or GC+

[jturboawd]

Originally Posted by luchocamp

never go wrong with Vargas GC or GC+

I see we have both moved on from the N55. I was speedtech, i recall you went big boost.

Planning on upgrading the snails in the M4 or sticking to stockers?

[jturboawd]

Originally Posted by MR_X

So how many beers and pizzas should I bring for you to help me with installing the VTT hub?

Not going to lie, its a pita. Might be the largest dominoes gift card in history lol.

Im more than willing to help some though if your local.

[MR_X]

Originally Posted by jturboawd

Not going to lie, its a pita. Might be the largest dominoes gift card in history lol.

Im more than willing to help some though if your local.

I’m in Austin. I may take you up on it.

[jpy1980]

How the car running

[e85m4]

Wish i saw a post like this 6 months ago when i tried installing my VTT GC !! The wastegates were not near OEM positionning and my installer didnt felt good with the was it was so we took them off and put back my stock turbos wish i would have felt the VTT sauce but i have now abandonned the idea !!

[Chris@VargasTurboTech]

Can always shoot us an email for assistance for install help/suggestions. Tons of S55 GC's in the field with very few issues.

Chris

[TopJimmy]

Originally Posted by Chris@VargasTurboTech

Can always shoot us an email for assistance for install help/suggestions. Tons of S55 GC's in the field with very few issues.

Chris

Hey Chris,

I've seen a bit about the wastegate alignment and maybe the worry is just lack of info. When we install VTT snails what is the right way to get existing WGs moved over and aligned? Is it a bunch of trial and error adjustment, or do we need to measure something and replicate that on the new setup, and/or is there something that needs to programmed in the computer? It can't be that hard...

Stay safe,
-Jimmy