Kev's Corrado - Project "Stealthy T"

Cheers Yan

No unfortunately there is no knock detection on the DTA. The trouble with aftermarket knock systems is you have to force the motor to det in order to build up a table of knock areas, which is something that turbo users are quite reluctant to do!! I've always run conservative timing though.

I was just an idiot using an old map with a totally different throttle. I should have tamed the map right down first, but you live and learn!

Looking through the logs last night, the injector duty only hit 50% at 1 bar boost, so I don't think the injectors are lacking in flow. I did see very high ignition advance in boost at some rpms, but low throttle position, so I'm thinking perhaps my dump valve isn't dumping when it should be. I'll strip that down tonight and regrease it.

It's really odd as I've never had issues with the rear bank before. There's nothing really horrendous shouting at me from the logs.

I'm going to completely rewire my DTA as I was never fully happy with my first loom tbh. I didn't have a good set of crimp tools back then, but I do now I'm going to wire the 24V loom to the DTA ECU plugs and use that to run the 12V. If it still misfires etc, then it's defo scratched bores oiling the plugs up. Then it's time retire the 12V :-(

I'm hoping that isn't the case as this motor's done me proud for many 1000s of miles and I'll miss it.

boost panda wrote:Kev, I found the throttle response on Ziderapple's 24V that he let me loose on very responsive too. I think it's part of the system as you say.

That's nothing mate, try a manual R32! My god. I honestly don't know how it was signed off and allowed out on the streets like that!

Ah, on the Diesel DBW pedal Yan, is it a 'string' type? Sounds like it's an early 1.8T type of pedal. It's mechanically mounted and hinged and the pots are connected via a string. I prefer the pedals with built in pots tbh, but that's useful info!

I like the sound of the R32

kevhaywire wrote:

boost panda wrote:Kev, I found the throttle response on Ziderapple's 24V that he let me loose on very responsive too. I think it's part of the system as you say.

That's nothing mate, try a manual R32! My god. I honestly don't know how it was signed off and allowed out on the streets like that!

Ah, on the Diesel DBW pedal Yan, is it a 'string' type? Sounds like it's an early 1.8T type of pedal. It's mechanically mounted and hinged and the pots are connected via a string. I prefer the pedals with built in pots tbh, but that's useful info!

Best guess Kev without going and ripping the drivers shelf out of the Passat and looking at ETKA seem to suggest that the pot is linked to the throttle via a lever mech that does indeed pull on a string.

I must admit that driving the car it does often seem a little random in terms of throttle position but I suspect that has as much to do with a 90bhp diesel engines output and 150k on the pot.

Kev, what are the brake discs for in the original pic?

Some kind of OEM+ KERS? LOL.

Yandards wrote:I must admit that driving the car it does often seem a little random in terms of throttle position but I suspect that has as much to do with a 90bhp diesel engines output and 150k on the pot.

Do you mean random throttle action in comparison to pedal movement? It is very weird, I agree. These throttles seem to be engineered to do the bulk of the work with less than 50% opening. Probably little point going beyond that on some VAG engines!! I know the 24Vs acceleration very noticably tails off with more than 40% throttle.

I've watched my throttle open whilst moving the pedal and it's an exact mirror image, all very linear, so I don't get it tbh!

I'm sure VAG would throw the engine light on if the pots in the pedal were worn? If that happens on the DTA, it limits the revs to 1750.

boost panda wrote:Kev, what are the brake discs for in the original pic?

Some kind of OEM+ KERS? LOL.

OEM rear discs mate. I had to bin off the 280mm rears because they are stupid money to replace!

kevhaywire wrote:I know the 24Vs acceleration very noticably tails off with more than 40% throttle.

That's very interesting Kev, as that is exactly what I found with Ziderapple's. But he said it needed mapping still so I put it down to being a flat spot.

Kev, I am never sure if its just a lack of go due to the engine and gearing (long gearing and 90bhp) or if the throttle pedal is a the problem.

It's just feels like sometimes it is very responsive to a tiny throttle adjustments and other times I have to move the pedal a lot to get it to do anything.

As for the ECU fault code, if the pot is worn but the voltage still falls within the stock values then there will be no fault code, given the pot has probably spent most of its life between 25-75% throttle this will be point with the most wear - I am speculating of course.

As for a linear map from pedal to TB, that's the beauty of DBW you can get it to do what you want it to. So a harsh setting would see it inline with the R32s setup and for motorway action or when its in for an MOT stop the TB at 75% open..

boost panda wrote:

kevhaywire wrote:I know the 24Vs acceleration very noticably tails off with more than 40% throttle.

That's very interesting Kev, as that is exactly what I found with Ziderapple's. But he said it needed mapping still so I put it down to being a flat spot.

Nah that's just how the engine is, mapping won't fix that. VW engineered it to make peak torque below 3000rpm. It needs more aggressive cams to fatten up top end.

Schimmel sell some lovely steel billets for the 24V (12v cams are cast iron). 264/260 profile, 23hp and 16lbft to the wheels. 855 bucks though! Everything has gone up so much since I did the 12V turbo. Still, that is 500ish quid, which is waaaaay cheaper than Schrick's 24v cams.

I've ordered the 24V Arp head and rod bolts, an 8.5:1 spacer, a chain kit etc etc and I'm going to get the motor on the stand this weekend and put it together. I'm in talks with Bill about those cams. I really want to see what I can get out of a 24v in nasp form. I think it's capable of far more than 71hp / litre.

250hp would be nice and I think I could get there with the cams and some tidy mapping. It will also give me time to assess whether my engine is actually worth boosting or not. No point spending a lof of money and time on boosting a dead horse.

With the cost of fuel at the moment, it's quite an appealing option actually, and yes I will really miss the acceleration!!. Mr Garrett can go into temporary retirement for a while and I can sell off some of my 12V goodies to recoup some of the 24V costs.

Yandards wrote:As for a linear map from pedal to TB, that's the beauty of DBW you can get it to do what you want it to. So a harsh setting would see it inline with the R32s setup and for motorway action or when its in for an MOT stop the TB at 75% open..

Some of the super responsiveness is down to the flow characterstics of the throttle itself, but yeah, using pedal to throttle translation, you can indeed force 90% pedal movement to be 10% throttle opening On OE systems you can set such a thing on the dash to put it in 'valet mode', but with a standalone you'd probably need a switchable map or something.

10% throttle is enough to hold a 90mph cruise though, so you could go even more agressive! 2% is all I need to hold an 800rpm idle, so it does give you some idea of how much more the DBW throttle flows compared to an old progressive opening 12V one.

Could you remap the DBW throttle to be more linear then? I hate electronics so I won't even try and work out how you do it!

I like the resistance that a sprung cable throttle gives tbh. I'm assuming a DBW throttle returns inder a spring force also?

Just so you don't think I'm ignoring you all......

Pedal position is normally determined by arbitrating between the input from the two tracks on the pedal. Each track's output will be 0-5v linear output, but either of different magnitude (e.g. ranges of 0-4v and 0-5v) or different direction (0-5v and 5-0v). Redundancy, range checking, sticking tracks etc, should all be covered by the ECU software. I guess DTA have all that in place? Track input voltage is mapped via a transfer function to pedal position.It is this 'mapping', which will mostly like be an interpolated 1d map of track input voltage against pedal position, that is the calibrateable part.

mrbeige wrote:Just so you don't think I'm ignoring you all......

Pedal position is normally determined by arbitrating between the input from the two tracks on the pedal. Each track's output will be 0-5v linear output, but either of different magnitude (e.g. ranges of 0-4v and 0-5v) or different direction (0-5v and 5-0v). Redundancy, range checking, sticking tracks etc, should all be covered by the ECU software. I guess DTA have all that in place? Track input voltage is mapped via a transfer function to pedal position.It is this 'mapping', which will mostly like be an interpolated 1d map of track input voltage against pedal position, that is the calibrateable part.

Never

I appreciate that all DBW gives you in terms of pedal position to throttle position is a lookup table to convert an input on one to an output on the other, I suspect the vague feeling I get in the TDI Passat system is due to the mechanical nature of the system, throttle pedal to mech swing arm linkage onto to a string.

Urgh I still don't like electronics, trying to figure out how to wire my bloody Ai606 into the VR, easy enough to plumb the power feeds etc in but working out how to get the full closure to work and where to connect it to is a pain, not aided at all by the fact all the impulse output functions on the Toad go to ground during the locking cycle - I need 12v!

boost panda wrote:Could you remap the DBW throttle to be more linear then? I hate electronics so I won't even try and work out how you do it!

I like the resistance that a sprung cable throttle gives tbh. I'm assuming a DBW throttle returns inder a spring force also?

It is linear electronically mate, i.e. 5% on the pedal = 5% throttle opening. But 5% pedal movement may not necessarily mean 5% flow from the throttle, if that makes sense? But that is the situation with cable throttles too.

That's what the pedal translation is for. If you feel 10% movement of the pedal is too much, then you can reduce it to say, 6 or 7%, or whatever. You could also have 10% = 80% if you wanted

The pedal has a very stiff spring in it, feels a little heavier than the cable action actually.

The throttle also has a very stiff spring in it and it's natural rest position is 7% open. It's a limp home thing. The two motors (virtual - it's one physical DC motor that runs in both directions) fully close the throttle blade on over-run.

It does feel surprisingly mechanical actually, minus the vibrations from the engine tingling your foot obviously.

Stuck some new plugs in last night and went out for a test drive. It was fine for 20 mins or so, but arrived back home with it misfiring on Cyl 1.

Took the plug out and there was a nice chunk of piston / ring jammed between the spark plug's electrode and insulator! How nice of the plug to catch it for me instead of allowing it to pass over the turbine blades

So yeah, the motor is fecked really. I thought I had gotten away with just piston crown damage, but if peices of piston are breaking off easily, it looks like the skirts / rings took a clobbering too.

Last night wasn't all doom and gloom though because the cause of the problem became apparent. Fuel pressure wasn't matching boost pressure past atmospheric. I thought it had to be something drastic and sudden to cause horrendous det on all 6 pots. Fuel pump failure looks very likely.

Oh well, you win some, you lose some. The 12V put in a good innings, so onwards and upwards.

I'm going to sell off all the 12V goodies to help fund the 24V conversion.

Spoke to Vince and apparently the early BDE 24V (coilpack version) is a pig to remap, so I will probably stick with the DTA.

Quite looking forward to a cammed 24V with the 3.6 final drive, it's going to be pretty rapid off the line

You going NA then Kev?

Stupid question.... can I have your dead block? or maybe just a piston?

I'd be interested in looking at it (alternatively, pics?)

p.s. sorry for your loss.... 60k is still impressive though!

RIP 12v

Woot 24v

**** but as you said it's had a good run and been used properly, at least the fuel pump let go later now and not when you had just run it in as that would have been soul destroying.

You going to run a second pump this time around?

Mr Beige - Yes mate, NA for the time being.

Was talking to Jon at Stealth and Vince built a 2.9 24V with Schrick cams + DTA for a Beetle RSI cup car, which made 275hp!! I always had a hunch the 24V was capable of 100hp/litre. A short runner liberates even more power, but at the expense of bottom end torque obviously.

I was aiming for 250hp with the cams, but if I get 275 I'd be well chuffed with that!

Boost Panda - Yeah no worries. I'll hoik it out of the car and see what's what and let you know!

Yan - Yeah. Vince was saying earlier he usually sees 80K from a forged piston engine, so it wasn't far off needing a rebuild anyway, but this incident has rather forced my 24V hand.

I'll just use a standard issue uprated pump for now, but when the boost goes on, I'll be using this neat little setup - [You must be registered and logged in to see this link.]

This is probably pointless, but I'll swap your dead block for the AAA i had for dissertation?

But then there'd be no 24v fun! lol.

LOL, I can just picture us block swapping and analysing them

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Found the ACTUAL problem tonight guys.

It was fuel related, but with a twist.

Ages ago I asked a fabricator to modify a couple of Schimmel throttle elbows for me. One for the future DBW install, and one with ISV and BOV take-offs. He did an OK job of them but what he didn't do was remachine the mating surfaces. Cast ally isn't really known for holding true when heated!

It's my bloody fault for not checking that before fitting it really, but as you've already guessed, boost was escaping between the throttle and intake and therefore not allowing the fuel regulator to ramp up the fuel pressure.

One of the elbows in question (the DBW one has no take offs) and a Moral: When welding ally, check it's still flat aftewards!!

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It's a different engine now And I appear to have gotten away with it as the engine behaved faultlessly during a 50 mile test ride.

The abuse this engine has withstood and survived is incredible. There doesn't appear to be any lasting effects. There's not a peep of blue smoke and it still pulls like a train, which means the turbo has also withstood bits of metal passing through it. Amazing!

So project 24V is on-hold again

Wow! The VRs really ARE made from granite!!

Glad to know you're able to punish it for a few more miles!

So did you leave that disintegrating piston in then? I guess if the rings still seal and it still holds pressure then it's fine

Yeah I can see why they have a reputation for robustness now

I think any bits of crumbliness have done their crumbling now and the worst is over. So yeah, I'll just keep using it until it finally gives up the ghost!