Overboost and boost bottles
Turbo Mini Forums

Being chairbound for the duration I have been doing a lot of reading and gazing at a screen.

Many modern diesels ( and, for all I know, petrol engines ) have an overboost facility which, as far as I can establish is a temporary increase in boost of short duration when accelerating to speed up, say, overtakes. I,m guessing that this is all electronically controlled, but I have come across an article, basically on bleeding the turbo signal to the wastegate, which also talks about putting a boost bottle in the line to give a temporary overboost.

Anyone got any comments on this,as it sounds potentially very useful to have, say, an extra 5 psi available for an overtake without having to switch it.

The boost bottle in the article was an aluminium Sigg drinks bottle, on a 2 litre plus engine, so I,m guessing (again !) that something a bit smaller might be more appropriate for an A series ?.

I suppose my question would be: why not have the extra 5 psi all the time?

A few of us are using a switched solenoid to bleed off a bit more boost.

Mine is setup to switch from 10 - to 20psi from a switch on the gear lever.

This is only really used on the strip to limit boost though. At 10psi it feels like there's a problem with my car.

In the 13's at last!.. Just

My Saab had a 20 sec over boost that gives it 250bananas. Otherwise it has 230. I don't know why it does it though really. In 20 secs from stand still you are doing over 100 so you are unlikely to over heat or over stress the engine as you can't drive like that any way.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Whilst it can work, it is a very uncontrolled way of doing it.

As jamie says, just run max boost all the time. If you want to overtake, put your foot down !

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Yes i moved to the darkside

Instagram @jdm_brett

I do have the switched solenoid bleed valve and am often tempted to go from 8 to 15 psi (or more) when provoked but then I get paranoid watching the AFR,s
as I cant seem to get reliable figures on both settings - is this even possible ?

The idea of the temporary overboost would limit me when the red mist appears maybe ?

Given the above opinions I think my effort is best spent in other directions, so thank you gentlemen .

BTW Brett, a long while ago when I was even more ignorant on turbocharging than I am now, I also ran split lines and had a lot of fun before realising that I was getting 20 psi.Dont think it would have gone for long though as I was on standard Midget pistons and no intercooler.

Mine is setup for 12.5:1 on 20psi, so if anything I'm more concerned about it being over-rich at the lower boost setting.

In the 13's at last!.. Just

On the hillclimber I have a switch on the gearstick. In first gear I get 15psi, in all other gears I get a higher boost.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

New tractors have also go this, but remember, there is no overboost. The engines are underboosted as standard It's just marketing.