Turbo and tuning set ups

[silverzx]

I've never quite got my head around the pressure/ volume thing and may be about to look a bit stupid but......if the area being filled (pipework, intercooler etc) is the same size and the pressure is the same with any two given turbos say, K14 and TD04, then I'd have thought the volume would be the same?

I know the TD04 would be producing more power but I always though this was because the air would be much cooler as the turbo wouldn't be spinning so fast to generate the same volume. Is it that the increase in temperature with a small turbo is causing a smaller volume of air to expand which is causing the pressure to be the same?

Is this on the right lines or have I missed something obvious? I was thinking that a small turbo (T2) with a really good twin pass intercooler would be the best solution for me as it would give minimal lag but sensible power up to the point that the turbo becomes a restriction in the exhaust.

I'm not looking for power levels where I'm approaching the breaking point of components (other than cheap, standard turbos!) but am now wondering if a bigger turbo running at lower psi would be a better solution or if it would be too laggy. While I'm going over potentially old ground anyway is it worth changing from a K14 to a T2 or is there no noticeable difference?

Imagine blowing down a straw compared to blowing down some hose pipe. Which is easier?

Turbos vary in size, the T2 has to spin a lot more due to the lack of size to create the same volume of air as a larger turbo such as a T25. The T25 has a larger hot/cold side and a bigger compressor so doesn't have to spin as fast to provide the same amount of volume. The drawback of this is lag. The bigger the turbo the longer it takes to spool (usually).

The beauty of more modern turbos is that they have a fine balance between spool and top end.

Ultimately VNT's are the way to go as they can effectively be a small turbo at lower RPM's to help with spool and become bigger turbos at higher RPM's so that they don't choke/restrict air flow.

They do this by varying the A/R (aspect ratio).

Basically do some research and it'll all make sense.

Heres a start:

http://en.wikipedia.org/wiki/Variable-ge...rbocharger
http://en.wikipedia.org/wiki/Turbocharger
http://www.myturbodiesel.com/1000q/turbocharging.htm

That's how I'm thinking it is a confusing thing to be honest

Also would a gearbox mount have more lag than down the bck where it should be as it's got longer to travel between engine to turbo just a thought just thinking simply ATM and it makes sence if it's wright

Correct, the longer the manifold the more lag you'll have.

[Cbray2003]

Thought so

[simonh]

That mydiesel.com link is a really good one. It's all about temperature so it looks like it's pretty much as I had it in my head, just hadn't realised how much heat affected pressure/ volume.

If I've picked it up right I'm thinking that 20psi at ten degrees will give the same performance regardless of turbo so psi is pretty much irrelevant for comparative performance potential unless the inlet temperature is known. 24psi with a good front mount should make more power than 24psi with a top mount (assuming it's a small turbo working hard) as the inlet temp should be lower but this is probably around the point where any more boost could actually drop performance as the inlet temperature will rocket, cancelling any gains.

Is there any information anywhere on the maximum inlet temperatures that can be run safely?

It also pointed out that diesels are accelerated by adding fuel rather than air like petrol engines (which is what I'm used to) so I had a bit of a 'lightbulb switching on' moment over the whole diesel tuning/ fuel/ boost thing works. Now I have the process in the right order the whole thing makes far more sense.

Thanks Silverzx

[Cbray2003]

I've always been told that the more cold air the better so and cold air feed to turbo then a gd fmic should give a decent power gain if done wright and I must say the old girl does go well in this cold weather

[silverzx]

That mydiesel.com link is a really good one. It's all about temperature so it looks like it's pretty much as I had it in my head, just hadn't realised how much heat affected pressure/ volume.

If I've picked it up right I'm thinking that 20psi at ten degrees will give the same performance regardless of turbo so psi is pretty much irrelevant for comparative performance potential unless the inlet temperature is known. 24psi with a good front mount should make more power than 24psi with a top mount (assuming it's a small turbo working hard) as the inlet temp should be lower but this is probably around the point where any more boost could actually drop performance as the inlet temperature will rocket, cancelling any gains.

Is there any information anywhere on the maximum inlet temperatures that can be run safely?

It also pointed out that diesels are accelerated by adding fuel rather than air like petrol engines (which is what I'm used to) so I had a bit of a 'lightbulb switching on' moment over the whole diesel tuning/ fuel/ boost thing works. Now I have the process in the right order the whole thing makes far more sense.

Thanks Silverzx

No problem dude! Glad its clicked.

The rep systems there for a reason.

[simonh]

Go on then! :-)

[Mal]

I've always been told that the more cold air the better so and cold air feed to turbo then a gd fmic should give a decent power gain if done wright and I must say the old girl does go well in this cold weather

My 406 uses an FMIC and while it's brilliant on open roads it's absolutely crap when in traffic. Admittedly, it's the stock one working with a much larger turbo....

I'll be experimenting with a side mounted intercooler to see if that makes any noticeable difference to me. It'd be convenient too, I've plans for a compound build....

[Cbray2003]

Would fitting fans to rad and a fan to intercooler make any big diff so drawing cold air threw the cooler and rad fans on auto if that makes sence

[Tom]

You dont need a fmic while your sat in traffic idling. I bet as soon as you move its way better than the topmount.

[Cbray2003]

I know there way better than a top mount jw if fans made a difference while driving or not

[silverzx]

If anything I'd of thought fans in front of a FMIC would have a negative effect once moving as it would just be blocking air flow.

[Cbray2003]

True I never thought of it like that

[Mal]

You dont need a fmic while your sat in traffic idling. I bet as soon as you move its way better than the topmount.

Nice to have a quick getaway at the lights though!

It is far better than a topmount but the 406 intercooler is the same size as the radiator and sits between the fan cowls/rad; a fairly poor design. If it were a third of the size, twice the thickness and have nothing obstructing it (ie the fan cowls) it could get the max air from the bumper cutout and work much better all round. There would be still a bit of heat soak but not as much as currently is

You'd still notice the difference in drivability from starting the car from cold in the city and starting from cold in the country....