Boost

[orionn2o]

Does anyone know what the safest highest boost, the VR$ can handle with a relatively stock engine??? And also what are the limiting factors???

[Nutter_John]

Hi there

I think upto 1 bar is safe above that you get fuel cut etc , try searching for boost controllers on here loads and loads of info

[BraindG]

1bar is safe (i run at that day in day out), aslong as you got a fairly decent controller that wont spike to much.. engines have been know to pop heading into 1.3bar..

[orionn2o]

Ok cos mine boost controller has a hi mode of 11.5 psi and i have a walbro fuel pump.


The boost seems very stable at the mo, so you reckon i could turn up to say 13/14 psi without issues???

[Nutter_John]

14.7 psi is 1 bar - i run mine at 0.9 bar with no issues

this is not a recomendation though

[Axeboy]

I used to run at 0.85 bar as a safe high and the car felt great.

However, 1 bar maybe more will be minimum as from monday on my current vr4... wo0000000000000

[colVR4]

I run at 15 psi with the Apexi S-AFC fuel computer. Never had fuel cut yet and no issues with turbos feeling like they are out of puff.

[White Lightning]

Apologies for hijacking the thread but this is related question

If each turbo supplies each back of 3 cylinders, where does the boost gauge read the boost pressure? Does it just read the boost pressure from one turbo or is the boost combined somewhere in the inlet manifold ???

[The Vee]

Apologies for hijacking the thread but this is related question

If each turbo supplies each back of 3 cylinders, where does the boost gauge read the boost pressure? Does it just read the boost pressure from one turbo or is the boost combined somewhere in the inlet manifold ???

3 cylinders supply each turbo and they both combine to produce the boost which is normally measured in the inlet manifold (via piping) . The manifold uses the combined boost to supply all six

[White Lightning]

Ahh, right, doh!

So let's just see if I've got this right.. each turbo runs off one bank of 3 cylinders and they both supply the boost pressure in the inlet manifold. So, the boost gauge is measuring the combined boost pressure of both turbos and therefore if one turbo was not running right you would not get the correct boost pressure - is that right?

[Kieran]

Yep - when a turbo pops, as Nick and Derek will tell you, the other can't keep up and you see little if any boost at all!

[Wodjno]

I run at 15 psi with the Apexi S-AFC fuel computer. Never had fuel cut yet and no issues with turbos feeling like they are out of puff.

And you hold 15 psi to the redline ??

[Sports GT]

I have a problem, experiencing a cut at 14 PSI and I'm not sure what it is... the car begins to stutter at 1 bar. I have a GReddy Profec EBC and we connected the vacuum lines correctly but it doesn't seem to be working.. the Fuzzy Logic mode doesn't pick up the boost curve and when trying to control it via the knob, it spikes no matter what it is set to... What causes boost spike? and what cut am I experiencing?

[BraindG]

What causes boost spike?

Here is a great write up by BDA explaining all about boost spikes

[White Lightning]

Yep - when a turbo pops, as Nick and Derek will tell you, the other can't keep up and you see little if any boost at all!

Cheers Kieran

I'll stop hijacking the thread now

[Axeboy]

I run at 15 psi with the Apexi S-AFC fuel computer. Never had fuel cut yet and no issues with turbos feeling like they are out of puff.

Col, can you let me know more about the safc settings you use at 1 bar...

[Sports GT]

Here is a great write up by BDA explaining all about boost spikes

Can't access it due to lack of CVR4 membership

[colVR4]

On the advise of a local garage (I haven't had it properly set up so take these with a pinch of salt) I have got the following:

Hi-Lo Throttle point: 25% 70%
RPM settings at: 2000 2500 3000 3500 4000 5000 6000 7000
Hi Settings: -1 -2 -2 -2 -2 -2 -2 -2
Lo Settings: -4 -6 -8 -10 -10 -10 -10 -10

I did a quick blast with WOT and the AFR (garage let me borrow it for free with technician sat beside me checking the readings) was still showing well in the safe region throughout the rev range with these settings at 1 bar.

The technician definately advises getting it set up properly but he reckons that the fuelling could be reduced by anything up to 25% at certain rpms and throttle positions!!

[Wodjno]

So are you holding 1 bar to 7000rpm ??

And if you require a Wideband Lambda Sensor with Logging and Analysing capabilities ?? I can supply one to you at a cost of £30 per week ! Any breakages paid for by yourself.. !

[colVR4]

Seeing no loss of boost at all, all the way through to redline