Turbocharger

Well, I have a package of springs appeared - £1.50 each but minimum order of £10 so I bought a few: I put in a linear spring, which should start to move the vanes out as soon as it starts to build boost, at a rate determined by the spring stiffness. I took it for a run, of which there's a video of the latter half. It makes boost at low revs, but I can't put my foot down too far because it's making too much boost - the spring stiffness isn't suited to opening up the turbo so it's hard to stop it making nearly 2 bar of boost, all the time! To compare what it'll do to Lara's numbers above, (yes, you guessed) here's another graph: The green bar shows how much more usable rev range I've gained - I can't stress how much difference is made by each lower 100rpm that boost comes in. This looks excellent but the video shows there's heavy surging (I think) and it's definately not happy. Oh, and it's not really driveable because there's plenty of air going in but I daren't put my foot down to add fuel, so it's actually quite slow. I've now got the confidence to go back to the original spring with the turbo more closed... or to use one of the plethora of other springs to further justify my investment. The lessons learned from ten mins driving it this evening has justified that £10 though, I understand more about how it works with every change. Has anyone done much work on what is an acceptable level of boost for a 300Tdi? Will it spit bits out at 2 bar? I don't think I want to run as much boost as Lara, but 1 bar across a wider rev range is quite acceptable.

OK So long as you know what you're getting into, could be fun. I still suspect that, as was posted above, there's cheaper routes to horsepower with naturally aspirated engines. Depends if you want a car or a "project". My VGT's definately a project

Phew - if these guys are the same shower offering their services to the Ford owners club, we've been lucky to avoid their 'squash and spatter' cage technique up to now! http://www.fordownersclub.com/forums/index...?showtopic=1929

I was speaking tongue-in-cheek about diaphragms etc, but you will need to pick turbos suitable for your engine's massflow and pressure requirement - it's not just a case of bolting on whatever you find. Then you've got to fuel it to ensure it doesn't go lean at high speeds, or you'll be playing a quick game of big bangs / melty pistons / "catch the conrod" etc

Turbos. Diaphragms. Waste gates. Pressures. Don't do it!

Today's random fact: diesel expands at 0.08% per 'C. And I didn't even have to look that up.

No, supersonic. I've used subsonics in a moderated Ruger 10-22 and all you can hear is the action cycling. Unfortunately, so can the rabbits, they know exactly where you are and they run away. With supersonics, the report comes right across the horizon so there's no point source. I found everything looks up to see what just happened because the whole world just got loud, so you've lots more contacts shining out from the lamp. You need a silencer that doesn't spit its innards across the field with the high velocity ammo tho

Of course, for greatest stealth, park on the road and walk up (with the gun in a slip of course). Then neither the noise of the neighbours or your rattly car will alert Mr Bunny to the impending doom. Then, a silencer and supersonic ammunition mean there's no single point of sound (if you don't get any texts at the critical moment ) and everything in the field stands up to see what just happened - perfect.

Once you're off the Queen's highway, just wire a pair of foglights on the front of your car, independently of anything else and use these instead of the side/headlights. If your LR is so quiet that it can only be detected by sight in the dark, that is. Or, make a detour down the road every evening at dusk, even if you're not shooting. They'll soon tire of it

Penalty for not displaying a registration plate is a non-endorsable £30 and it'd be impossible to determine whether it's taxed or not at the roadside. Obviously I couldn't endorse any kind of law-breaking but we all know how insecure those numberplate bolts can be... "They were there at the beginning of the journey officer"

Well thanks very much Dave. You've ruined a perfectly good discussion with ideas I've been warned about before: "analysis", "critical thinking" and generally being probably right. I hadn't linked the surging and the diaphragm lifting off its end stop - a strong argument. I can't clock the compressor housing because the pipes would point the wrong way, and because the inaccessible bolts are seized and I'm not prepared to risk it. Thinking laterally tho, there's no reason I can't move the diaphragm a little lower and angle it to point directly at the vane lever, much like Lara's dimensioned and toleranced CAD drawing above Looking at it now, there's no good reason why it has to point back along the car at all.

You're really not shy with that machine, are you? Just to let you know, one of the pics shows that you need a bigger wheel on one corner, doesn't reach the floor. I'm glad the bumper damage was repeated - it means the Stanage weakening would have happened later anyway, and this way round you weren't so cut up about breaking a bit of the car that was already broken. Ooh, by the way, Mum amortised your damage to her gate at £20 over the life of its replacement, so I'll pay her in lieu of smashing the front of your car up on Stanage and we're all square

The linkage will certainly be improved if it's a permanent fixture. At the moment the poor stiffness is a useful feature because it means I can bend it into the shape I need so that the adjusters work over the right range. It'll then form the template for something more permanent. In truth, it's pretty stiff so it's not wobbling all over the place. I see your argument over harmonic vibration, but wouldn't it tend to resonate equally either side of the static position - eg giving a generally correct position to the vanes? Then it'd need quite a lot of energy to move the whole thing at 2Hz and I didn't see a big difference when the M10 threaded bar was 300mm long (I trimmed it in situ). In fact, with the bonnet off there wasn't an obvious vibration problem. I'm pretty sure that what I'm hearing is surge, but I've got a handful of springs in the post today so I'll try to have a play next week. First though, after today's events I have a disagreement with my MG's MOT man over the phrase "in the examiner's opinion" so I have to do a two hour job whole weekend's work first. Keep the ideas coming though - they, and the tangible improvement in power, are keeping my interest in the project.

Mike, I'm not a moderator but I have met you and you're a reasonable and sensible chap. It sounds to me like one of the mods has referred to a question which has been asked in the moderators forum where someone says "I don't recognise this chap, is he spamming?" and another mod has replied "No, don't be stupid, he's just posting useful links" - and then you've received the wrong end of this stick entirely via another mod's interpretation. Keep the shiny side up John

Well, I've done some more playing. This graph shows revs against boost: The red line is how it was, my baseline setting. After talking to my dear old Dad I wound the fuel up half a turn on the base fuel screw (didn't touch the injector pump diaphragm) - this gave the green line. Then I wound the vanes closed by ~1.5mm, still with the fuel turned up. This gave the response shown as the blue line... but the area shown in the circle was definately showing surge, a fluttering sound as if it was making boost for half the time at about 2Hz, sounding a bit like a misfire might. Sorry Julian Any idea what the boost response from your Td5 might look like on these axes? The blue line hits 1 bar at 1800rpm which is about what I got from the old turbo - progress, but not the quantum leap I was hoping for. It's worth mentioning, running the engine on the blue curve at high revs means it gets to sixty in about 13 secs, which is frenetic and exciting but it's surging hard and it's absolutely not what I was aiming for with this conversion. It does suggest what could be achieved by winding the boost and fuel up on a standard engine though, EGT allowing... I'm pretty sure I need a more proportionate response from the diaphragm to move the vanes, and I should have a handful of springs turning up in time for the weekend, if Mr MOT doesn't condemn me to a weekend putting new brakes on the MG.

I bought a strip of sticky-back flexy tape which has circuit board in it and surface mount LEDs on it - kind of like a single-strip version of these I think. I stuck them on the underside of the internal gutter above the rear door. Very poor photograph of the LEDs turned on: And plenty of light to read the small print by, taken on holiday in Cornwall: From memory it was about £30 but well worth it for camping light and no jump-start worries next morning. It didn't seem to attract flies too badly either. To be honest, they've got a waterproof product at the site I've blatantly spammed and I'm thinking one each side would be good enough for a reversing light.

I've just put an MEX-BT3600 in my Tdi, on the lower face of the dash (just enough room between it and the handbrake). It's got a mike in the front panel of the radio apparently. Bearing in mind I've just installed the world's loudest turbo and it doesn't have any inlet ducting, you're welcome to ring me and listen to the other end of it to get some idea. I don't expect it'll work very well but I'd be interested to see - I haven't tried it when I'm driving yet. PM me if you want my number.

Consider the axle separate from the body. With an axle and hockey sticks on the ground in front of you, when the car cross-axles it's the same as your lardy mate pushing the chassis end of one arm towards the floor while you try to lift the other one up. The standard hockey sticks are overcontstrained and it's only the movement in the bush that gives rotational suspension travel (roll travel). Your system would have much more constraint because of the increased separation of the axle mounts and the reduced movement in the Johnny joints. Now, if you could make one of the diagonals incorporate a variable length, then you could be cooking on gas but in plain metal, not a goer I don't think (even for marks in a Uni project).

:hysterical:

Well, after a chat with my dear old Dad he was a little confused too - he develops diesel engines for a living (and in fact, found me the turbo). His thought was that the lack of boost is due to limited turbine energy, for which I need more massflow (ie higher revs) or more energy in the gas (more fuel). That made sense since the EGTs on motorway cruise are much lower than before - there's much more air going in but still the same amount of fuel. SOOO I'll have a play with the fuelling and see if that can push it up to higher boosts at lower revs. I'm not aiming for a revvy engine, I want torque and lots of it!

I sat through the same lectures, probably understood even less and no, I've produced no Bode or Nyquist diagrams for the system but I think it'd have to be considerably faster to start to oscillate - for the response I need the whole thing will operate in quasi-steady state anyway. Surging is an unstable effect but it's not driven by the control system on the turbo, regardless of the gain. Surging is where each blade effectively stalls in the airflow - there isn't enough airspeed to generate the lift required by the angle of attack. As the pressure difference over the blade is able to equalise around the leading edge, when it's suddenly able to start building a pressure difference again until it becomes too great, stalls and starts again, so the compressor effectively switches very quickly between these two operating points. This alternating load on the blade can snap lumps off and that's why it's best avoided. (I did the turbomachinery lectures too and understood rather more of them...) In this case the 'airspeed' is mass flow, the lift is a pressure rise across the blade which induces more flow and the angle of attack is defined by the compressor geometry - I can't just 'dip the nose' like a plane would to get out of the stall but I can reduce the 'lift' required by backing off the throttle. I know the diaphragm isn't oscillating wildly because 1) the boost is stable at speed, and 2) without the bonnet I could see the arm directly and it was steady If the weather warms up above minus five I'll nip outside and wind the adjuster back to a more 'interesting' position and give it another run.

I will add - the standard turbo would be up and boosting strongly by 2000rpm. The object of this project is to give more boost low down for driveability and eventually to fit the 1.2 tbox I rebuilt 12months ago, to give better fuel economy, lower noise and longer legs on the motorway. At the moment, it's worse than standard altho the idea's not dead yet. I've certainly seen the potential for strong power benefits from lifting the boost level - if I can't see boost at lower revs from the VGT then the project's failed and I'll go back to a standard turbo running more boost and pocket the difference in insurance premium!

Cheers guys - it's good to get a perspective from someone who's done it before. In the current setup with the diaphragm on its 'zero pressure' stop, the linkage is adjusted so the vanes are about halfway "open". It can make pressure much earlier if I set the vanes to fully "closed" (small turbo) - you can hear the compressor spinning up on just a high idle with closed vanes in one of my videos. However, in this position it only generates a very small pressure before going into surge as soon as I prod the throttle. This is why I've had to push the 'zero point' out nearly half way, so that it doesn't surge in that position. From what you've said I'll try a more aggressive (ie more closed, smaller turbo) setting for when the diaphragm's at rest but I think it'll surge. I'm already a little concerned because the compressor's noisy, it's a very 'dirty' sound rather than a pure whine/whistle, but as it passes 1 bar and the vanes start to move it becomes considerably quieter and sounds happier - I think this is the onset of surging being quashed by moving the vanes out. You may be able to hear it in the dashboard video above as it passes 1 bar? The phone doesn't really do it full justice in reproducing the tone but it definately shows the reducing volume. I'm know a weaker spring will move earlier and I'm hoping this will lift it out of the surge region gradually as pressure builds.

I'm not a V8 type but if you're just short of room (instead of "it's actually touching") then I've heard tell of Robin Reliant filters fitting but being much shorter. Might help?

Blimey, everyone wants a piece of my time at the moment Yes, I have progress! I repiped the diaphragm since there was a tiny air leak which was losing "not a lot" of volume but "oh plenty" of pressure. Once airtight, I pressurised it with my workshop airline: and then measured the diaphragm's movement: (See, top science in this game). Then, since it drives, I went 100 miles to see a friend, recover another friend and do some shopping, so my passenger took a video of the dash while I drove. The rev counter is on the left, and the turbo pressure is on the right. 1.0bar is shown just before the end of the orange, and the turbo is quite laggy, doesn't hit 1.0bar until about 2300rpm, and stabilises at about 1.3bar by 3000rpm (by which point I'm munching along at quite a rate!). This, along with the workshop 'pop off the push-fit hoses with the air compressor' game, gave me some results and allowed me the delight of ploughing through hours and hours of spring tables, selecting possible candidates that is the right diameter to go in the can, not so powerful I can't cram it into the diaphragm with my bare hands and, god forbid, suitable for the job of controlling the turbo. Using these springs and the data from pressurising my own diaphragm, I now understand it more: I can see now why it stabilises around 1.3bar at full chat, because the vanes don't move at all until 1.1bar and has travelled through the full 7ish mm available by 1.5 bar, so it stabilises somewhere in the middle. I've had to set the rest point where the turbo can make 1 bar without any vane movement so that it doesn't surge much earlier, so I'm not getting full benefit from the VGT which is why it's a bit 'laggy'. I need a spring which will start moving at a lower boost level to allow me to set the 'rest point' much more aggressively, knowing it'll lift off as soon as it starts making any pressure. I think the spring shown in purple is my best option. If anyone has a spring that matches these specs, post up or I'll have to go and buy one (at £1.05 each, but minimum order of £10; the graph shows the other nearest matches and I don't see the value in getting more than one of each type ) I need: Wire diameter: 3.25mm Outside diameter: 25.4mm Free length: 38.1mm No of coils: 6 Rate: 24.5 N/mm Solid length: 20.3mm Maybe a phone call for an 'engineering sample' is in order...