Boost level on VLt

[jhevo]

Hi Everyone,

I have boosted my car recently and intercooled it as well. Huge difference to when it was stock.

The question here is, say I'm in 3rd gear and give it hard throttle, the boost gauge hits 14psi and then stays steady on about 10-11psi, does this mean I am running 14psi or really I am running 10-11 psi?? Why does it go to 14-15psi and then goes back to 10-11?? Is this normal or is it not just holding boost?

[GTSBoy]

The boost spike to 14 or so is just that...a spike. The boost control on your car is not fast enough to stop the boost level from rising past your set point (10-11) and so it shoots past then gets pulled down.

You are running 10-11 psi. but if your car will ping on 14 psi then it will possibly do so while the spike is happening, so you have the worst of both worlds, ie boost too high, and low(er) boost performance.

Look at the Audi type boost controller article on Autospeed or look into buying an electronic boost control, or adjusting whatever boost controller you have now to reduce overboost (if possible).

cheers

[jhevo]

I have the turbosmart boost controller. How would I reduce the boost spike with this? Is there anything I can add on to stop this?
It doesn't ping when it spikes to 14 or so psi.

[PVL-747]

if it doesn't ping don't worry about it. my friend used to run avgas + toulene and it used to spike to 20psi and held 15psi and it was fine as it wasn't pinging. oh this was with no intercooler.

[GTSBoy]

You can't stop that sort of spiking with the Turbosmart jobby, unless you have mounted it in the cabin on long hose runs. If you have it on the shortest hose runs possible then you will get the minimum amount of spiking out of it (the long hose runs work as a reservior that delay the boost signal to the wastegate).

It may ping such that you don't get to hear it. Just coz you ain't hearing pinging don't mean it don't happen. I was just warning you that it might happen.

cheers

[Ogre]

However, he said he has also intercooled it. Even if it is a small cooler, there isn't much chance that a VLT will be pinging at 14psi.

[darkstar]

pinging is not something that you can hear all the time, and even the trained ear cannot detect it at times.

You can ping any car at any boost, it all depends on hte settings.

if the timing is too far advanced, then it will ping.
If the charge air is too hot, it can ping
if the water cooling system isnt up to scratch, it can ping.

And the worst is when your injectors leanout, or they have some built up shit in them, that will definately cause pinging.

Wrongly tuned, or inaccurate AFMs will cause pinging as well.

As you can see, there are a variety of ways you can ping hte car, and you wont even notice till you strip the engine down and take a look.

IF its pinging already, thats basically the piston slapping against the bore, rocking on the rings. thats what you hear, the piston slap, and dont forgert the piston is moving up and down at the same time.

So if you can hear it, then its either too late, or you better back off. If you can gear it in the cabin, then it must be pinging really loud.

As for the boost spikes, very common on the vls, and cannot be avoided effectively due to the way boost in managed. You could however do some sort of mods to the bleed valve to help it flow better, and also fix / replace the acutor controling the wastegate.

[jhevo]

Thanks guys for your replies. I now have a much clearer perspective as to this subject. I think my car should be okay as to where I have the boost set. I might also get it properly tuned etc and dynoed to see whats happening. But should be okay.

Regards,