Sam's build thread

[seangti]

first vid ive seen that shows a back to back comparison of the same car (VW mk2 GTI), same corner, same speed with two different diffs - wavetrac versus quaife. Pick the wavetrac before reading the comments.

https://www.youtube.com/watch?v=E4wY2NoJ6f8

and here's another vid that shows the two main differences between quaife and wavetrac. The 'wave' camed gear that side loads the pinion when a wheel lifts and the carbon end shims that the side gears run against. In a quaife from what I can gather (and I could be wrong) apparently the side gears run against the side of the housing itself.

https://www.youtube.com/watch?v=QEhLGe_M6XU

I'll have to have a look at these when I get home. My research always brought me back to wavetrac being the preferred torsen diff, both from function and technological perspective. Not that I probably researched as much as you. A mate had done the research, I just did a validatity check. Didn't even price up the alternatives.

[sambb]

Yeah I think I'm going to go wavetrac over the SQS plate diff. I know that there could be lots of circumstances in that vid that would make them behave differently eg. track temp, tyre temp/wear, leaves on the track, heavier right foot etc etc but it does seems to show enough of a difference between the wavetrac and a normal torsen to justify it. My mate has a quaife in his clio and his does exactly the same thing as the snippet in the video of the quaife if he single wheels it slightly coming out of a corner eg the wheel kick as it sort of grip shifts left and right. If I remember rightly Eddy said his Peloquin did this too. The wavetrac looks like it grips up and just drives out smoother. If a wavetrac looked to be no different to other torsens then I'd have gone with the plate diff and I'd have just worn the risks regarding wear and tear on driveshafts and the clutch packs over time and all the kays I do, but I think the wavetrac will be the best compromise.
Ultimately I'm going to be a sub 250hp car and maybe the plate diff was going to be just over doing it a bit.

In other news my gearbox is with the gearbox guy. Apparently one of the gears is a bit worn which might account for some of the whining so we'll replace that and once the standard diff is removed and we know the ring gear internal diameter, then I can order the wavetrac.

Since my modded K03s is shagged I'll want to get this box in asap to hopefully keep me up there since I may be competing with the standard turbo for a while.

[seangti]

The wavetrac part number for mine is: 10.309.181WK.

[sambb]

cool. thanks mate.

[sambb]

When I went to separate the turbo from the exhaust manifold, I realised that I'd nearly fallen victim to the loosening turbo bolts saga that's been playing out for years. I'd done an exhaust manifold to head gasket nearly 2 years ago and at the time we noticed that the exhaust manifold to turbo face was shaped like a bowl. I had it linished flat thinking that that's why the turbo bolts might be loosensing, but I suppose not.
Having a good look at it this time the gasket had actually split at the most narrow point and was starting to burn through. If you have a good look at the exhaust mani to turbo bolt holes in the pic, it might give some clues as the why this happens. Top left is rectangular and 11.45mm wide, the biggest one is a perfectly round 11.45 and only one hole is 10.2 di mm which is how they all should be. Its beyond me how this could've gotten through quality control in the volume that it would have.
I reckon with a bit of heat expansion the 2 contact faces might be moving around and then either the thinnest point in the gasket burns through or the hottest bolt eg the one where cyl 3's runner goes around it expands and comes loose and does so easily because the hole is so big there. Short of filling the manifolds holes with weld and re drilling I've decided that I'm going to do away with the OEM washers and in their place I've found some nordlock washer variants that have nearly the same OD as the stock ones. I don't think I'll use the VW turbo bolts either. Nordlocks simply will not vibrate loose but could unwind if the bolt lengthens eg due to stretching. I don't think the OE bolts are high tensile and so are probably stretch bolts to some degree. I don't see that there would be any shearing forces and the manifold and turbo are both cast (same material) so I'm going to use 12.9 high tensiles and torque them up as tight as I dare. If they don't lengthen then the nordlocks should do there job. We'll see if that holds.
I have ordered 4 sets of these washers. I'll keep a set spare for myself which means i'll have 2 sets in case anyone else goes through the same thing.

[Eddy]

Hoyhoy.

Sam, my feeling is that the turbo has been moving around when ya gun it, pivoting on the good bolt hole.

To Improve Me Polo. - Page 7

Blow up these pics (Ctrl & + button together, then to get it back to normal size hit Crtl & 0 )

Now for the turbo bolts (VW's are 12.9) coming loose everything has been tried years ago to fix, including Nordlocks.
From what I know this is the best answer & has been tested for years, haven't a prob since doing this. >

To Improve Me Polo. - Page 3

Sam there might not be any shearing forces, but there is weight hanging from the turbo which doesn't help any.
The pics below show what I done to help relieve the load on the turbo & several folks reckon that this the reason for me not having any more loose bolt probs, but I think it is a combination of this & welding the bolts. >

Red Devil mkII - The Journey Continues

This is just from my personal experience Sam doing a fair bit of hard track laps & that is when the bolt prob comes into play , so don't hold me to it & have a go @ what you want to try.

[sambb]

Eddy my K03 has a factory bracket that swings down from the hot side housing and is double bolted to the block. Does your K04 not have this or are your brackets in addition to it?

Yeah I read in some old posts that people had used nordlocks. My hope is that they'd used the commonly available M10 OD 16mm ones though. These barely sit out from under the bolt head and barely purchase on the top of the manifold given that the holes there are nearly 12mm eg the washer would have only 2mm either side to grip into and that just wouldn't work. The bottom Nordlock of the pair needs to tear into the mounting surface so that they become stationary relative to the bolt and I don't think this would happen with the standard nordlocks. The 22mm OD ones will have a big mounting face and should grip better, but if that turns out to be enough.. we'll see I guess.

Yeah I think your right re the turbo moving around. The manifold and turbo are both bolted to the engine and each other, but the turbo gets north south forces through it from the dump pipe especially if the dogbone isn't doing its job. Now that my dogbone is sured up (maybe not to the extent of yours but better) maybe that will help too.

I was thinking that maybe the outside two turbo bolts closets to the fire wall could just be run right through and turned into a bolts and nut arrangement which would be stronger.

Unfortunately this will all have to go on the back burner for a bit anyway. My turbo shaft free play issue has snowballed into something bigger. I was all set to split the turbo and get a new CHRA for it. I separated the exhaust housing from the turbo core tonight at work and found a crack in the housing opposite the hot wheels' exducer. Not sure if that's a bin job being where it is so I'll have to get someone to look at it for a diagnosis. Its sux because of all the things on that turbo, it was only the exhaust housing that mattered. It was ported pretty extensively and to have to bin it will suck badly. If I have to bin it I don't think I have the stomach to re port another K03 exhaust housing and it may just be easier to go K04-001 + tune. I'd love to do a K03s/K04 hybrid but not sure if you can get a flash tune for that.

In better news the gearbox is going back together with a wavetrac in it and I should have that by next weekend.

[seangti]

If I have to bin it I don't think I have the stomach to re port another K03 exhaust housing and it may just be easier to go K04-001 + tune. I'd love to do a K03s/K04 hybrid but not sure if you can get a flash tune for that.

In better news the gearbox is going back together with a wavetrac in it and I should have that by next weekend.

That's all a bit of a bugger man. On the previous turbo before it failed, though after the previous exhaust manifold cracked (i.e. standard manifold, hybrid turbo), the race workshop I use had lock wired the bolts. They had to source appropriate bolts to do so tho. It's a "challenging" job to lock wire back there. Won't stop bolt stretch if that's the cause. Though since the new turbo, just factory bolts on the factory manifold and it's been fine, torqued to spec. The torque spec is really quite low, so be sure not to over tighten/stretch.

Re the tune for hybrid, have a chat to Gavin, mine and Louis' were all custom road tunes with logging and development post each log. The logging detail with ME7 is sensational, along with so many other features that can be programmed in/out.

Great to hear about the wavetrac purchase. I won't recognise "my car".

[sambb]

yeah your right hey. I remember the torque specs for standard bolts were low. Maybe everyone just over torques them and the over tightened bolts just let go with a bit more heat. I'll tell yout that was true of getting the exhaust housing bolts loose off the turbo core. They were unbudgably tight and only a small bit of heat from a 450 degree heat gun and a tap on the tab and they were instantly loose. I mean a turbo exhaust housing is going to bloody well be cooking normally so it surprised me that just a tiny bit of heat and a tap and they let go.
Eddy said the VW turbo bolts are 12.9 high tensiles which at a low torque setting wouldn't be stretching. Maybe they set them up that way so when heat expands the castings either side of the bolt it effectively tensions the bolt at operating temp. If its overtightened initially and then subjected to the same forces maybe that's what is warping everyones mating surfaces and eventually the bolts/gasket let go. I'd had the turbo and exhaust manifold mating surfaces linished last time and neither are particularly flat now nearly two years on. My mechanic who did the first swap said he did go a bit over spec last time so maybe that is the culprit.
Tonight i'll file finish the exhaust manifolds turbo mating surface because its too hard to get on the linisher. Then at least thats ready to go in whether it be with your original turbo or something to do with my turbo if the cracks by some miracle are judged to be superficial. I'll get some pics of the cracks up in a bit.
Its funny with the diff - I was actually still deciding between SQS and wavetrac and had pretty much arrived at wavetrac. The guy that was ordering the parts for the build though had misunderstood me and took asking for a price to mean I want one order it now. I was actually going to call him to say OK green light, lets do the wavetrac when he called and said the diff is heree from the states and it'll be going together over the weekend. Ha ha I just stayed quiet and was happy that things (at least on something to do with this build) have moved quicker than I anticipated. Now I'm actually a bit behind there and have to find somewhere to get the pressure plate and flywheel balanced after getting a bit more meat taken off the flywheel, and get all the tools together and engine braces etc again.

Yeah it still doesn't quite feel like my car yet - feels like I've borrowed it from you or something. I even found a lakeside timesheet under the seat the other day! But once the diff, short shift, rear beam, stg 2 gear and vibratechnics go in (that scarily I plan on doing all at once) it'll feel like mine then hopefully.

[sambb]

first three pics are step by step close ups of the crack I'm most worried about. There's also a hairline on the divider between the path to the turbine and wategate. It feels like there's a tonne of meat behind that bridge and I can't see where that could possibly leak too. Its the one where the gases are thrown out from the turbine exducer onto the housing that looks bad.