Boost Levels

[fredfour4]

How much boost can the vr4 engine safely take (EC5W)?

What are the power gains from altering the boost.

As we all know more boost can provide more power but at what cost to the engine.

I know from experience that the Maserati biturbo engine are bullet proof unless you over boost them and engine rebuilds are expensive. I should think the vr4 lump would be as well.

What boost controller would you recommend, if any.

Thanks

[bradc]

You can normally get them up to about 1 bar before you hit fuel cut. The turbos are too small to do any real damage to the engine, I've got an aftermarket ecu so I don't have fuel cut at all and I'm running at 1.3bar without any problems.

[Kieran]

You can normally get them up to about 1 bar before you hit fuel cut. The turbos are too small to do any real damage to the engine, I've got an aftermarket ecu so I don't have fuel cut at all and I'm running at 1.3bar without any problems.

0.9/1 bar is about the safe limit, though on standard fuelling you could be asking for trouble if something lets go - Also, because the turbos on these cars are so small, pushing them to 1 bar is stretching them - whilst we don't have compressor maps to verify this, I would say they would be like the standard Jap-Spec 3000GT turbos (TD04-9b) and some way out of their efficiency zone at this boost level, but it can be done and many people do, quite safely.

I disagree with Brad's comment that the turbos are too small to do any real damage - As I've mentioned, if it leans out then they will quite happily start to blow chunks off of pistons, as we've already seen in the club several times!

If you're looking at increasing the power, then yes, VR-4s do respond well to upped boost, it's much better if it's combined with exhaust modifications - the entire factory system (Downpipes, cat and cat-back) is restrictive and you'll benefit from sorting this out.

[bradc]

yeah that has happened a few times, but looks at how many people are running high boost, as a percentage the amount of engine failures are very small.

[Kieran]

yeah that has happened a few times, but looks at how many people are running high boost, as a percentage the amount of engine failures are very small.

Sure Brad - I agree. What I'm saying is that the closer to 1 bar (and beyond) that you run, the more at risk you are of something going pop and causing trouble - even if it's just something daft like the intercooler hoses blowing off!

As I say, many members run at 0.9 or 1 bar all the time - they can take it quite safely, all things being equal - but if something daft does happen (say your fuel pump starts to go and the fuel delivery rate drops) then you're gonna know about it sooner rather than later if you know what I mean.

[bradc]

yeah I knew what you meant all along, but I think for 99% of people upping to 1 bar will be perfectly safe.

Something that is interesting about fuel pumps is that while noone (well I can't think of anyone) has had their stock fuel pump die on them, over here quite a lot of places seem to think Legnum fuel pumps die all the time and they replace them regularly on cars. Maybe it is just non-vr4's?

[fredfour4]

so can the boost levels be altered via the standard ecu

[Gly]

no,

you need to fit a boost controller of some sort,

either a boost tap/bleed valve, or a electronic boost controller.

[Turbo_Steve]

Might be worth buying yourself a wideband and a good boost gauge with your boost controller. You can check your fuelling is good, then.

[Kieran]

Might be worth buying yourself a wideband and a good boost gauge with your boost controller. You can check your fuelling is good, then.

A wise precaution. Okay, it's well known that VR-4s run quite amazingly rich on the standard maps, even with 99 octane in the tank - even on boosted cars it's not uncommon to see 10:1 AFR at WOT, but that's assuming everything is tickety boo. Monitoring things may just be the key to an early warning and backing off in time, or the dreaded DET DET DET and a trashed piston or two! - And also, they'll be of great benefit to you in the future if you wish to fiddle with the fuelling.