It's been a while since I have owned a turbo car and never a modded one, possibly back before ecu control of them actually.

So, a few questions on how they're controlled these days and tuning;

1. I've seen posts about limiting the torque on a standard clutch. Does the ECU open the wastegate earlier to limit the maximum spinning speed of the turbine? I can't see how you can increase the BHP while reducing the torque though.

2. The EGR delete pipe. I understand it's on there to lower emissions by feeding back some particulate laden exhaust air back in for re-burning.

The question is, what sort of a difference does it make taking it off to;

a. emissions

b. health of the turbo (hot dirty air can't be too good for it right?

c. power - does it make anything by itself

3. Tuned or otherwise, do turbo's fail and destroy the engine as much these days or do they normally just go sick? I don't mind tuning with the expectancy that I'm probably replacing the turbo at some point as long as I'm not likely to be picking bits of it out of the pistons and wondering where the missing valves ended up.

Four sleeps until I get on a train to pick up my vRS by the way!

1. I've seen posts about limiting the torque on a standard clutch. Does the ECU open the wastegate earlier to limit the maximum spinning speed of the turbine? I can't see how you can increase the BHP while reducing the torque though.

ok, they don't have a conventional wastegate on these as such, it has a vnt turbo which uses vanes with a variable geometry to control the sped(boost level) of the turbocharger... but to all intents and pruposes it has the same function as an internal wastegate...

ok, beteeen the manifold and the 'wastegate' actuator there is a hose which feeds pressureized air to the actuator like a 'normal' turbocharged engine.... but on these there is a solenoid valve (N75) which effectively bleeds off a proportion of this 'boost' which is applied to the wastegate under control from the ecu... so say the wastegate is deisgned to operate at 15psi for example, if the N75 bleeds off 50% of the boost signal the turbo is now operating at 30psi, but the wastegate is still only getting 15psi... what that means in real terms is that you can have a map in the ecu for the boost pressure so you can dynamically adjust the the boost level for different operating conditions... i hope that makes sense. it's quite difficult logic to understand

and you are indeed right, bhp and torque are directly related, so if you reduce torque you also reduce bhp.. although it's not quite as simple as that in real life, i imagine tuners will limit torque lower down in the rev range (using the boost mapping) to favour clutch life, but let it churn out full whack higher up in the rev range.

2. The EGR delete pipe. I understand it's on there to lower emissions by feeding back some particulate laden exhaust air back in for re-burning.

The question is, what sort of a difference does it make taking it off to;

a. emissions

b. health of the turbo (hot dirty air can't be too good for it right?

c. power - does it make anything by itself

a, yes an egr valve lowers a the NOX emissions on pretty much all cars, but this is probably only fitted on these cars for corporate reasons to make them sound more eco-friendly, currently in the uk the only emission test on diesels is a smoke density test so it all kind of pales into irrelevance tbh

b, the gases fed back to the engine are fed directly into the intake manifold, so no egr gasses ever go through the cold side of the turbo.

c, nope

3. Tuned or otherwise, do turbo's fail and destroy the engine as much these days or do they normally just go sick? I don't mind tuning with the expectancy that I'm probably replacing the turbo at some point as long as I'm not likely to be picking bits of it out of the pistons and wondering where the missing valves ended up.

sadly they do still suffer from some pretty spectacular failures even on new-school engines, even in standard tune they have been known to fail.. although fortunately at least in this case you have the intercooler to act as a filter to stop the broken bits entering the engine when the turbo blows up

Edited 16 September, 201015 yr by TeflonTom

Hi TeflonTom

What a great reply!

I do understand the turbo/solenoid explanation, makes perfect sense.

It's like drive-by-wire throttle bodies, you used to press the accelerator pedal and a cable opened the throttle.

Now you press the pedal and an ECU recognises you're asking to some beans, checks what it should do against it's map and opens the throttle the appropriate amount.

I'm missing out on the point of the EGR then, is it just to keep the intake temp down a bit and keep more oxygen in there? I'd have thought that would give a little power by itself though?

I forgot about the intercooler/turbo-bits-filter being in between, that puts my mind at rest a bit.

Coming out of a 209bhp/210lbft 1162kg VR6, I'm expecting I might want a little more grunt, but in gear the performance when I had test drives was very impressive as standard so a mild map might be all I'm after or just a tweak.

I'll have to evaluate that decision when I've been in it for a few weeks. 1 more sleep!

Hi TeflonTom

What a great reply!

I do understand the turbo/solenoid explanation, makes perfect sense.

It's like drive-by-wire throttle bodies, you used to press the accelerator pedal and a cable opened the throttle.

Now you press the pedal and an ECU recognises you're asking to some beans, checks what it should do against it's map and opens the throttle the appropriate amount.

I'm missing out on the point of the EGR then, is it just to keep the intake temp down a bit and keep more oxygen in there? I'd have thought that would give a little power by itself though?

I forgot about the intercooler/turbo-bits-filter being in between, that puts my mind at rest a bit.

Coming out of a 209bhp/210lbft 1162kg VR6, I'm expecting I might want a little more grunt, but in gear the performance when I had test drives was very impressive as standard so a mild map might be all I'm after or just a tweak.

I'll have to evaluate that decision when I've been in it for a few weeks. 1 more sleep!

EGR is purely an emissions thing. IIRC it is used to reduce the NOx levels in the exhaust gasses by feeding a certain proportion of ther gases back into the engine to be re-burned.

The in gear acceleration times of the Golf and the Furby vRS should be very similar in standard trim as the Furby may be slightly lighter than the Golf, it also has 228lbft torque as standard, most tuning companies state that they can take it up to roughly 260lbft on just a simple remap.

re. the torque thing, general consensus is that 300lb-ft at the flywheel is the most the standard clutch can handle, but mine has more like 330 with the clutch going strong something like 20k down the line. Like Tom says, the main thing is where peak torque is reached. As standard, and with many remaps, the peak more-or-less coincides with the turbo kicking in at 1900rpm. With mine, peak torque is at 2200rpm, with it below 300lb-ft before 2000rpm, and remaining above 300lb-ft until about 2750rpm. Assuming the dyno's mark-up is reasonable, of course! Although how I only came out with 170bhp after all that, I'm not entirely sure!

The in gear acceleration times of the Golf and the Furby vRS should be very similar in standard trim as the Furby may be slightly lighter than the Golf, it also has 228lbft torque as standard, most tuning companies state that they can take it up to roughly 260lbft on just a simple remap.

Far from being slightly lighter, the little Furby is 153kg heavier! While the mk3 was a jump up from the mk2, it was the mk4 that was the real bloater.

I agree though, they felt fairly similar as standard once you take out the lag/lack of throttle response on the TDI. I'm also used to driving the golf between 1000 and 4000 rpm where I normally change up as this is where the schrick switches modes. Occasionally I will rev it beyond but not in daily driving. So while seemingly opposites on the surface, I'm actually expecting them to be quite similar.

On the torque vs horsepower thing, I've never really thought HP mattered that much unless you were looking at pushing a vehicle to it's top speed.

Torque can be directly measured but HP on engines is always calculated as it's a measure of torque over time and I think distance, or one or the other. I can't say I ever really understood but I think there's a constant involved of 5000 ish rpm and below this torque will always be higher than rpm, above it hp will always be higher than torque.

So, if you revved a diesel engine to 6000rpm it would actually have more HP than torque - briefly that is until the pistons let go. :yes:

It's all linked to steam engines and in actual fact horses but HP is directly related to the torque produced.

HP on engines is always calculated as it's a measure of torque over time and I think distance, or one or the other. I can't say I ever really understood but I think there's a constant involved of 5000

yes that's quite right... horsepower is a measurement of work done over a distance, i forgot the exact figures attached to it now but i'm sure some google warrior will come up with the answer.. the magic number is 5252rpm, if you plotted torque and horsepower on a graph against rpm the lines always cross each other at 5252rpm for ALL engines petrol or diesel

yes that's quite right... horsepower is a measurement of work done over a distance, i forgot the exact figures attached to it now but i'm sure some google warrior will come up with the answer.. the magic number is 5252rpm, if you plotted torque and horsepower on a graph against rpm the lines always cross each other at 5252rpm for ALL engines petrol or diesel

Work over distance, that's the term I was looking for.

I still never quite understood it, but I like torque, I know that. :p

stick with your vr6 then, it will make mincemeat of a fabia vrs, even a 'super mega hyper chipped' one

I can't run the VR6 under the company car allowance scheme due to age so that's not an option. Thought about just getting an R32 but they're just too thirsty and I've always liked the looks of the vRS.

yeah true.. mines a bit partial to the odd drop of the old 95' vintage every now and then

The mk3 VR6 isn't that bad on juice, or at least, it can be driven so it returns reasonable mileage. Mine will easily do 36mpg on a 50 mile run for instance but the R32 even with a light foot is nearer 24mpg and that's just ridiculous.

I've known a couple of owners who don't drive them like they're stolen yet average *gulp* 18-19mpg.

mines an auto... i'm very lucky to get 26mpg on a run

Ouch!