Sam's build thread

[sambb]

I was thinking about the pressure the exhaust gases are putting on the wastegate flapper with my modded K03s exhaust housing. If the wastegate port has been opened up so that more exhaust gases are able to exert force onto the upstream side of the flapper, I was thinking that surely for a given actuator spring pressure that it'll be easier for the exhaust pressure to force the flapper open prematurely. If the spec spring for the tune I'm on should be 7psi on a stock K03s, surely on the modded turbo I'd need to go up to say a 9psi spring to maintain equivalency. thoughts?

Need some advice on wastegate actuator settings. I just tested my turbosmart IWG75 with the '7psi' spring fitted. The rod just starts to move at 0.4bar (5.8psi) and has moved 3mm at 0.5 bar (7.25psi). I always thought the spring was rated for when the rod just starts to move in which case my spring might be a bit under done. But then I thought that since you usually set the flapper with 3mm of preload, the 3mm of rod movement number (7.25psi) would equal when the flapper actually first cracks making the 7psi spring accurate.
So which is it when your looking at whether your springing is accurate - when the rod first moves or when a preloaded flapper first moves? surely the latter just depends on your preload which is independent of your springs rate...... help

[seangti]

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.

haha, thought I'd done a better job of cleaning it out. Wonder what year that was from... I'd tracked it once in the last 3yrs and perhaps only 3 times in the last 4.

Re the turbo, a turbo specialist, race workshop, Non-destructive test specialist or metallurgist should be able to give a solid response on whether it's cause for concern. At a novice's glance I'd say it's superficial, it's only gases that pass, there's no load on that region, e.g no bolts going through it. Best to explore tho. I've thrown my old turbo only weeks ago, otherwise I'd have pulled that out to see if such cracks existed on it.

[sambb]

yeah there's a lot of meat behind both spots and they are downstream of anything sensitive. The fitters here have a dye that you can add to the crack so you can see how far the crack tracks or whether it penetrates to the outside causing a leak. Might give that a shot otherwise i'll go and visit some shops and see what they say. My mech said its quite common in turbos that are pushed way beyond their normal range and I suppose this has been true. At one point I was running stage 2 hardware and a stage 1 tune that I had to trick to run it. It had a 12psi wastegate spring and 26psi. That plus not running much timing in that tune probably pushed shaft speeds and EGT's through the roof. It was a rocket ship though.

I can get a 10psi wastegate spring for my wastegate so i'll go with that.

With the compressor housing off I thought I'd have a go at removing the turbo muffler from the canister. The plan was to weld shut the voids. I tried heat and soft hammers ranging up to heat and a freakin slide hammer and that sucker wasn't coming out. They must have pressed the muffler in after it'd been in liquid nitrogen or something. Now that that's failed I'm just going to cut the thing off and weld in a section so that it resembles a K04. I know the muffler deletes in a lot of the newer turbos are more for just noise enhancement. I'm not motivated by that at all - I just hate the ugly thing and all the space it takes up and the voids are massive. They'd have to mangle flow so the whole canister will be gone soon.

[sambb]

in other news I helped a mate with a rough pre-alignment alignment before coming into work tonight. Look at these babies and drool. Rollcentre correction ball joints and bump steer correction on the tie rod ends and the hubs specially machined to receive them. Extra castor and 20mm wider track than a standard clio w172 rs. All sphericals and rose joints. He was able to lower the front end a further 30mm yet enhance the geometry rather than butchering it.

I might be driving it at Tamworth state round next month which will be nice.

[seangti]

I can get a 10psi wastegate spring for my wastegate so i'll go with that.

Are you doing a retune? You may not want to be changing springs without tuning as the wastegate duty cycle will change with the spring rate. I'd ideally have ran a ~15psi spring for my ~18psi boost, rather than 7psi that was in it. Hindsight hey... I didn't know about that stuff at the time. Still may do it in the future once life settles.

[sambb]

Ideally I'd do a jump to 9psi but turbosmart do 10psi only. I've ordered one (rip off!!) and i'll bench test it before it goes in. I'm not 100% sure myself but the way I see it you have to think literally in terms of pounds per square inch. If you take out the port leading to the wastegate massively you've increased the 'per inch' part of the equation. The pressure on the back of the flapper is acting over a bigger area and so its easier for it to force the flapper open irrespective of what the N75 is telling the flapper to do. If the actual spring rate is for a 7psi crack, the effective spring rate will be lower because the boost pressure will be assisting the spring, additive with it. I bet if you fitted a 10psi spring, applied only 7psi to the actuator but also had 24psi pushing on the flapper from the other side, that it'd crack. I just can't see how a 7psi spring won't be flapping in the wind once that wastegate port is enlarged.
Well i'll try it anyway. If it pulls timing more than my old logs especially considering that i'll have a front mount now in winter, then I'll go back to the 7psi spring . I can get my hands back there easily enough if I have to swap it out

[sambb]

Linished the turbo mounting face flat again.

So I showed the turbo exhaust housing to my mech, the engine builders next door and an engineer. I didn't prime anyone with what the last person said and they all said that the crack in the wastegate/tubine bridge was superficial and not worth worrying about. The one where the gases leave the turbine got a few more in depth looks but they all said that despite the fact that repair is possible, that re cracking there would be highly likely and that it wasn't cause for much concern given the amount of meat there and that a crack that would cause a leak wasn't likely looking. They all seemed to think that if I intended having the turbo in there for another two years that I'd get away without a drama.
Apparently to fix it they pre heat a bucket of sand and have it at the ready. The whole housing then needs to be baked up to a cooking temp so that the welding temps are close to the rest of the housing. If not then the cracks can get worse as it cools and new cracks can form. Once its welded it gets buried in the sand so that it cools off at a really controlled rate.

What I'm going to have to do with the compressor housing is make a jig so that once the canister is lopped off we have a guide for the height and angle of the new pipe work. This all hinges on me being able to find nice thick walled aluminium tube in the first place though. There's no rush on this though. I still need to get all the bolts, washers, banjo bolt gaskets etc, test the wastegate and sell some more stuff to afford the new turbo core.
I'm really glad that I can stay with the turbo I've got because I was always very happy with how it went and its the cheaper option too.

And Sean, yeah I'll be running the same Stage 2 tune on that wastegate actuator spring. I'm just taking an educated guess. If its a fail its easy to set right again.

[sambb]

First step in getting my stage 2 ECU into the new car was getting the old cars immobiliser chip off the board. I do a fair bit of soldering at work but not really any SMD surface mount stuff. I got my hands on cheap ebay hot air gun station and followed a few youtube vids like this: https://www.youtube.com/watch?v=hw8OGplwefE to get the chip off, and all went to plan.

Since the old car is well and truly scrap by now that chip can go in the bin. I now have to do the same to the ECU in the new car and when that chip is free, re solder it my stage 2 ECU. Following some advice from Gav and this guy: https://www.youtube.com/watch?v=MqivHi7Qjvk I should be back in for some stage 2 fun. I'm just waiting on the solder pen thingy from Jaycar and then I can do that side of things.

[sambb]

Success - pretty stoked. Did the immobiliser chip swap without a hitch. I only got as far as reinstalling the stage 2 ECU and checking that the car started aok but I didn't have enough time to put the dump in, so it'll be interesting to see how it drives tomorrow. Will probably be all over the shop.

When the air box etc was out for the ECU swap I was sizing up the gear shifter/linkages. I'm going to swap the fresher one in from my old car. I noticed though that the bracketry that supports the linkages at the gearbox differs between this car and the old one. The points where the 3 bolt bracket fixes to the gearbox are the same (I measured them) but the new cars sits the cables a little higher meaning that the top one fouls on the forge TIP where it curves upwards from the turbo. I didn't have a forge on the other car, it was an ebay copy but it was nowhere near fouling on the different linkage bracket. Its bad enough that the TIP presses the cable down straight off the linkage support bracket and could nearly be enough to rub through the TIP. When I swap mine over this weekend i'll see if it clears.

[sambb]

The turbosmart 10psi wastegate actuator spring just arrived so that'll go in and be bench tested on Monday.
Also made up a jig that will locate the pipe that will come off the turbo after the turbo muffler/canister is cut off. I'm waiting on some nice thick tubing to arrive next week and then i'll take it down to my mech who will weld it in and clean up all the internals.
Once that's done all I need to do to get ready for the turbo core swap is to sort the 3 manifold to turbo bolts. VW wanted $17 each. Yes hex head 12.9's are hard to find but that's ridiculous. I have cap head (allen head) 12.9's and just need to see if there will be access to the bolt closest to the head (the one that always comes undone) if I go with a cap head.
By then I should have the dollars to order the K03s core and slap it all together.