Boost gauge question

[gpl1968]

Have just fitted a VDO boost gauge prior to fitting an MBC.



I connected it to a spare nipple on the inlet manifold and it is reading -20psi at tickover and a maximum of 4psi on hard acceleration.
My question is for those who have fitted a similar gauge.
Are these readings what you would expect and when I fit the MBC, what boost level I can safely set?

[Clan]

The boost pressure is low , it should be 7 to 8 psi at full load ... look at the wastegate seat after removing the front exhaust pipe they can crack and burn hence leak when shut ... A crack isnt too much of a problem but over years it gets wider and gas leaks past lowering the boost pressure ...

[gpl1968]

The car is an LPT which normally runs at a lower boost so I assume that 4psi is OK.

[Steve940estate]

I think your car is a low pressure FK model isn't it ? I don't know the exact figure but I think the high pressure is normally what Clan suggests.
If it a HPT then you might have a leak or the compressor bypass diaphram might be splt of dirty. The wastegate actuator might not be is as new condition either.
As for the maximum boost it can depend on what fuel you use. I set my car to 10psi as an absolute maximum ie foot to the floor after lifting off and it didn't pink on super unleaded. Wasn't quite so happy on the standard stuff though.
Because the turbo is quite small you won't see full boost unless you give it a bit of welly so be careful you don't go too far. I'd suggest about 9psi and see how it is.

[Clan]

The B230FK is indeed 4.5 psi its amazing how this engine can be less bhp than a non turbo B230E ( more torque however .)

[TonyS9]

I used 11psi for about 1 year on my 95 B230FT, and mostly it was fine, but on a top speed test the turbo casing cracked around the bearing and blew out a cloud of water that I saw disappearing very fast in the distance.

Backing off, and allowing slow cooling, it was ok the rest of the journey (100miles), but needing topping up regularly. Of course it gradually got worst and I didn't use antifreeze and head corroded a little on the usual No. 4 area (exposed to water) leading to slow head gasket failure and overheating. £350 later for recon turbo, and head skim its been fine since for several years, but I elected to go back to normal boost.

The moral is don't let the heat build up too high.

Incidently I managed 0-60 in 7.5s with 11psi, top speed was 140mpg (in another country). but you sacrifice the engine.

Next time I have a switchable valve to add to encourage more sparing use.

[1stRaven]

Just to clear a few things up. 4 psi is right for the lpt cars of which yours is. The hpt cars run 7-8 psi and you can up yours to that pressure with no issues (the only difference between the lpt and hpt is the wastegate actuator).

Going over that pressure and you start getting into the grey areas. I could run 10psi on my 740 until I chipped it which got me 14-15psi. After that, I had to fit a new engine management system which gives me about 25-30psi.

Up to you how far you want to go but there are options available.

[Steve940estate]

One thing to take into account is that all gauges can vary slightly and I believe the weather can affect boost settings if you use a bleed type valve.
Some cars were fitted with Volvo Turbo plus systems that allowed higher boost under full acceleration. I think that was about 10psi but it came with a knock sensor to wind things down a bit if the engine pinked at all.

[gpl1968]

I fitted the MBC last night (it's a ball-bearing/spring type).
I think I'll stick at 10psi which gives plenty of power for my needs. Now it's better than my last 945, which had turbo+ fitted