Cold Air Intake (D.I.Y.)

[DarrenJ]

Hi Guys,

I've been modding my TDI Cupra for a good while now,

I want to get better air flow going, I smoothed the air box already, and I can hear more turbo spool now and crisper diverter valve sound.

I love the Carbonio Cold Air Intake, but it's very dear. I rekon a D.I.Y. jobbie would do the trick. I rang up a shop doing Tumble Dryer spares. They sell lengths of Dryer Pipe 4 inch or 4 .5 inch diameter.

I was thinking of taking out air box, battery tray and to bore a large hole in the air box,

the 4 or 4.5 inch needed and to attach a length of this pipe (quoted 25 bob from shop for about 4.5 foot of pipe which is plenty!)

and to send it down to the foglight grill, maybe cable tie it securely to something to ensure it's facing out toward the airflow.

Question Time!

#1: In peoples' experience - is this too wide a diameter, i.e. will I have enough room to turn the pipe from the box down to the front of the car without kinking the pipe?

What diameter is the max that will fit comfortably from the box down behind the battery and to the foglight?

I'm happy running the standard panel filter at the moment. I have a boost gauge installed, so can monitor any improvements.

Any recommendations or anyone done this themselves?

 

[sssstew]

have a search for SPT

 

[DarrenJ]

Thanks!

Right so my research concludes:

100mm filter, 100mm **** pipe 90deg bend, 100mm **** pipe flexi.

It's the '**** pipe' that gets me - is this simply a 100mm pipe that I can pick up at a hardware store?

I see Halfords sells flexible aluminium pipe for this purpose. I was thinking of simply having a flexible pipe coming out, might even be better than a rather severe 90 degrees that might slow down flow.

 

[DarrenJ]

Update I now have purchased this at B&Q! 14 bob

1.5 metre aluminium flexi duct

'Domestic Ventilation' it says it's used for ..... !!

 

[DarrenJ]

SHeesh it's far too wide!

The bloody battery tray is in the way and then other wires that look like they'll be hard to move too.

Is the battery tray hard to relocate slightly?

I have a problem - the OEM air pipe enters the box diagonally, making cutting a bigger hole for a bigger pipe hard.

What do you think:

Patch and block off this hole and cut another one in the box somewhere that I'll be able to get a bigger pipe in handy and send this pipe off to the foglamp?

 

[DarrenJ]

Ok here's what I did instead -

Got a length of hoover pipe, 40mm.

Drilled hole in box. I left the original feed pipe, don't wan't to got cutting stuff out etc.

I inserted the hoover pipe

I then went to the front of the car, pulled out the air feed coming from the lower passengers side bumper (there's a scoop here that a pipe attaches to and simply runs air into the engine bay).

I put my hoover pipe into this pipe and did the necessary things to attach it.

Here's a pic of it sitting in the the pipe that attaches to the scoop before I cut and reshaped it to suit the new pipe:

So now what I have is a system that will ram air into the box. So I went out and tested it. Today was very cold, but really clean crisp air around. The turbo was definitely livelier, without a doubt, and it felt it pulled a bit better.

These are the things I want to do before mapping her.

Another simple, cheap and effective mod!

Happy out - cost me 12 bob (just the pipe)

 

[sssstew]

good to hear darren.

 

[Muttley]

That scoop is routed to the oil cooler, so keep an eye on your oil temp (if you have a gauge) once the weather warms up.

 

[DarrenJ]

That scoop is routed to the oil cooler, so keep an eye on your oil temp (if you have a gauge) once the weather warms up.

To tell you the truth, when I bought the car, this pipe had been off for months before I even noticed it, prob since the bumper was off before getting sprayed.

I will keep an eye on things. This is my 2nd Seat Leon and I have never even heard coolant fans coming on on either of them ever! And that's with new temp sensors in them too.

Turbo is lapping up that cold air!

 

[DarrenJ]

good to hear darren.

Yeah I'm happy with it so far, it's so simple too that I don't think it can go wrong.

A question for you Stew,

I was talking to a mechanic who drives a tdi pd 130 golf very done up mapped to 180 straight through etc.

He mentioned to me that he does a little thing on them to improve economy - he unplugs fuel temperature sensor and solders a wire across the connectors.

I then said - this sounds something like those cheap chips you can buy, but you aren't putting in a resistor.

He swore blind to me to go and try - I can't see how just putting in a wire without a resistor will help at all.

What's your opinion on this?

I'm curious to try it but it doesn't make sense!

 

[Muttley]

In your original post you say you can hear "crisper diverter valve sound".

How?

 

[DarrenJ]

The 150's have a diverter valve, i can simply hear it more now, along with a louder whistle from the turbo.

 

[sssstew]

Yeah I'm happy with it so far, it's so simple too that I don't think it can go wrong.

A question for you Stew,

I was talking to a mechanic who drives a tdi pd 130 golf very done up mapped to 180 straight through etc.

He mentioned to me that he does a little thing on them to improve economy - he unplugs fuel temperature sensor and solders a wire across the connectors.

I then said - this sounds something like those cheap chips you can buy, but you aren't putting in a resistor.

He swore blind to me to go and try - I can't see how just putting in a wire without a resistor will help at all.

What's your opinion on this?

I'm curious to try it but it doesn't make sense!

That is interesting how this would technically improve fuel economy, as the ECU uses the fuel temp sensor to decide how much fuel to inject at each cycle, and unplugging it and wiring it accross would lead me to believe that the ECU will have to resort back to default figures for the fuel map, which in some situations might improve economy but overall i would expect to see a drop.

Hmmm i wonder... what do you think muttley as well?

 

[DarrenJ]

That is interesting how this would technically improve fuel economy, as the ECU uses the fuel temp sensor to decide how much fuel to inject at each cycle, and unplugging it and wiring it accross would lead me to believe that the ECU will have to resort back to default figures for the fuel map, which in some situations might improve economy but overall i would expect to see a drop.

Hmmm i wonder... what do you think muttley as well?

It interests me alright!

I would generally be sceptical about this sort of tampering. He said he took apart one of those chips that act on the fuel temperature sensor and that all that was in it was a wire looping the two ends of the connector, so he simply looped these himself. He reports very good economy, and when a friend of his in an A3 130 bhp said he was getting poor economy, he did this mod on it and the economy increased a lot.

It would be no harm to try it.

I do not like the idea of 'tricking the ecu' and making it overfuel as a result, as you need to change boost/air flow etc along with this. But if doing this, as you say, might revert to a default map, it could be worth trying. I would avoid this overfuelling as it only builds up soot and washes the bores.

I read up on this sort of mod on TDIclub, but they were putting in 2.2k ohm resistor in line to make the ecu thinks the fuel temp is different than it actually is. This works better in hotter climates, these lads were in the USA. But some did it that lived in very very cold -20 celsius winters and reported no loss in power and better economy.

I'll take a look at it anyway and see what's the easiest way to attach wires. I could solder them anyway.

 

[john_tdi]

I wouldnt do it myself.

Why not just clean the temp sensor? Prob why you get poor mpg. Same thing is common on 1.8t's. The air intake temp sensor on the inlet mani gets covered in crap and then gives poor mpg. I guess its the same type of thing on PD's. By cheating the sensor your not getting extra mpg per say, just adding lost mpg from having a dirty sensor (if that makes sense).

Oh and the 150 doesnt have a dv mate. Its a diesel.

 

[Muttley]

DarrenJ wrote

The 150's have a diverter valve, i can simply hear it more now, along with a louder whistle from the turbo.​

Oh dear, and you were going so well.

No diesel is fitted with a diverter valve, dump valve or any kind of pressure-relief valve that actuates on the overrun. Unless it's been vandalised by someone who wants to hear it fart on the overrun and doesn't care about poor performance and eventual turbo damage.

The "dump valve" is a kludge fitted to turbocharged petrol engined cars to make life a bit more bearable for the turbo. When you back off on a petrol car, the throttle butterfly closes and all the pressurised air suddenly has nowhere to go, so the turbo stalls, and there is a loss of boost after the upchange (often called "turbo lag").

Diesel's don't have a throttle butterfly.

 

[Muttley]

sssstew wrote

That is interesting how this would technically improve fuel economy, as the ECU uses the fuel temp sensor to decide how much fuel to inject at each cycle, and unplugging it and wiring it accross would lead me to believe that the ECU will have to resort back to default figures for the fuel map, which in some situations might improve economy but overall i would expect to see a drop.

Hmmm i wonder... what do you think muttley as well?​

I think it will store a fault code, cause the EML to light, and revert to a stored, conservative, map - a "soft limp" mode. This will reduce performance. It may improve economy, but the performance hit would be noticable, and destroy whole point of having the great TDI 150 engine.

From an engineering point of view, it's a horrible idea.

 

[DarrenJ]

DarrenJ wrote

The 150's have a diverter valve, i can simply hear it more now, along with a louder whistle from the turbo.​

Oh dear, and you were going so well.

No diesel is fitted with a diverter valve, dump valve or any kind of pressure-relief valve that actuates on the overrun. Unless it's been vandalised by someone who wants to hear it fart on the overrun and doesn't care about poor performance and eventual turbo damage.

The "dump valve" is a kludge fitted to turbocharged petrol engined cars to make life a bit more bearable for the turbo. When you back off on a petrol car, the throttle butterfly closes and all the pressurised air suddenly has nowhere to go, so the turbo stalls, and there is a loss of boost after the upchange (often called "turbo lag").

Diesel's don't have a throttle butterfly.

I know the dump valves are for petrols, one look in the LC (r) section and that's obvious with everyone going for the Forge ones.

Is it a heat exchanger they have? That bloody mechanic filling me wit crap again saying that the 150's, not the 130's, have a system where the boost is put back into the system when the foot is let off the throttle after a good rev. That's right no butterfly (which when closed would cause boost to build up) so now need for one). There's a fairly loud hissss when I let off the revs, where does this boost go? I don't have any boost leaks, at least I don't think so and the boost gauge is showing up to 24psi in 2nd n 3rd gear which is fairly good I think, as these engines are meant to boost to 21.7 psi peak, or so I have read.

Thanks for informing me about this.

 

[DarrenJ]

I wouldnt do it myself.

Why not just clean the temp sensor? Prob why you get poor mpg. Same thing is common on 1.8t's. The air intake temp sensor on the inlet mani gets covered in crap and then gives poor mpg. I guess its the same type of thing on PD's. By cheating the sensor your not getting extra mpg per say, just adding lost mpg from having a dirty sensor (if that makes sense).

Oh and the 150 doesnt have a dv mate. Its a diesel.

Yeah sounds dodgy enough. I get good economy myself. I'll clean the temp sensor anyway, where bouts is it on the pd 150? inlet mani too i suppose, is it in the plastic intake pipe from the airbox or on the manifold itself?

Yeah I get your drift about that alright.