Turbo size requirements

[DR Frankenstine]

What are the pitfalls of fitting a small turbo to a big motor or vise versa??
Say a turbo off a 3.3l 6cyl diesel motor onto a 4.2l diesel

[KiwiBacon]

A turbo that's way too small will choke. Exhaust pressures rise to silly levels and exhaust temps with them. Your exhaust valves may float (springs can't hold them shut).
All this leads to bad things (engine meltdown).

A turbo that's too big won't boost until you've given away most of the rev range. Won't hurt the engine, but won't perform like it could.

[big lux]

it will spool, quicker but u will lose out in the top end power so max power if u wna fork out some cash u culd get a VGT turbo. but wouldnt advise small turbo on big eng waste of time u lose mre then u gain in the end

[RN]

I can get a Hitachi turbo cheap that were fitted to RX 5's . Was told it will owrk OK on the Mav 4.2. Even though the motor is smaller displacment it can make pretty good HP. Only want a turbo for low end stuff not high end grunt.

[chunderlicious]

what you have to remember is that although rotaries are only 1.3 litres they have a huge air flow rate/requirement so the turbos are larger than most 4 cylinders. the turbo might work quite well for you nazi depending on what model.

[beretta]

The GU factory turbo is a HT18 Hitachi turbo, maybe the same turbo you are talking RN?

[DR Frankenstine]

Would a HT15 be big enough for a 2H diesel?

[mule75]

i used to have a turbo off a saab (about 2.5l i think) on my 1hz and i went awesome. it did get hot easy and didn't rev as easy past 3000rpm though. it didn't seem to hurt the engine as it was on for prob 80,000km and it's still going perfect now and has done over 500,000km(but now with different turbo). it wen't better down low than it does now with the proper turbo but now it revs a bit easier 2000-3500 without heating up quick.

[Tapage]

Would a HT15 be big enough for a 2H diesel?

Did you have the HT15 turbo numbers .. like hot AR and compresor trim .. ?