Outer Limits 4x4 Board

When should full boost be reached when you have full exceleration.
I get boost start to happen at 1800rpm in a 2h diesel landcruiser and reach full boost (7psi) at 2500rpm but it only gradually comes on through that rev range.I am just wandering should full boost start at 1800rpm when my foot is flat or should it just gradually rise.

Your boost will only gradually hit full over the rev range even when your foot is flat.



rick

The boost characteristics on the 2h will be different for every turbo setup, as none of them are factory setups.

When and where it comes onto boost is really dependant on a few things. Mainly turbo size and fuelling levels.

If you have too big a turbo, it will take a long while for the turbo to spool up. If you have too small a turbo, it will spool very quickly but will peak too early and you will see your boost drop off higher in the rev range, not to mention you will be over spooling the turbo and will cause damage.

If we assume your turbo is perfectly matched to your engine, it is more than likely a fueling issue. If you are underfueling, it will take a fair while for you to build up pressure, as the exhaust velocity/temperature will not reach significant values until higher revs are hit.

If you are over fueling, the exhaust temps climb much earlier in the rev range and you will see the turbo spool up from a lower rpm. Over fueling causes excessive engine heat which will eventually lead to melted pistons in a 2h.

If your turbo is the right size for your engine, i would suggest you are underfueling a little, because my 2h used to hit full boost around the 2100rpm mark, which was 12.5psi (not 7). The boost needle would gradually climb over that range, starting with about 1psi boost at 1000rpm.

Exhaust restrictions can cause your boost to climb slowly also.

What does your exhaust smoke look like?