There isn't a definitive best turbo for the 306 hdi, it's all a matter of what your after. The TD04 isn't the best option for a HDI but there are turbo's that work such as the gt20 as said above, but again you will need to find away of mounting it to the exhaust manifold as the flanges are different and also setting up the VNT aspect of that turbo. I'm sure Jonny can help you with that as he's already done it.
How much power are you aiming for though? And what mods have you got already? There's no point fitting a huge turbo if you going for like 120 - 150 bhp as this can be achieved on a standard turbo using other mods. That will then keep your power lower down in the revs making it more driveable.
If your going for more then yeah you need to start looking at the turbo, but remember there are other mods that are vital to go with it. The main thing id consider when looking for a turbo is where do I want the power... The bigger the turbo you go for the further up the rev range the max power will be, and lag will also increase as it take longer to spool, hence diesels being fitted usually with smaller turbos.
I built a Iveco daily turbo 2.3 HPI hybrid recently (K03s basically the gt17 equivalent) it didn't really take much effort and its was pretty cheap in terms of turbos. I bought the unit of ebay for £90 then took it to a turbo specialist and had it fully rebuilt with 360 bearings for a further £220 so £310 is pretty good if you ask me. And its gonna be a solid unit as the specialist rated it to 30+ PSI.
Another thing to consider is whether you want a VNT setup or wastegate setup? VNT's are more versatile in that they come in earlier in the revs but can carry on for longer when compared to an equivalent waste gate turbo, but they are harder to setup and it will require some research, I believe there's two methods of doing it. Obviously a waste gate setup is simple in that it just goes on like your original and off you go, plug and play affair.
Its all just a matter of what power you want and where you want it, then you can buy the correct turbo for your setup.
How much power are you aiming for though? And what mods have you got already? There's no point fitting a huge turbo if you going for like 120 - 150 bhp as this can be achieved on a standard turbo using other mods. That will then keep your power lower down in the revs making it more driveable.
If your going for more then yeah you need to start looking at the turbo, but remember there are other mods that are vital to go with it. The main thing id consider when looking for a turbo is where do I want the power... The bigger the turbo you go for the further up the rev range the max power will be, and lag will also increase as it take longer to spool, hence diesels being fitted usually with smaller turbos.
I built a Iveco daily turbo 2.3 HPI hybrid recently (K03s basically the gt17 equivalent) it didn't really take much effort and its was pretty cheap in terms of turbos. I bought the unit of ebay for £90 then took it to a turbo specialist and had it fully rebuilt with 360 bearings for a further £220 so £310 is pretty good if you ask me. And its gonna be a solid unit as the specialist rated it to 30+ PSI.
Another thing to consider is whether you want a VNT setup or wastegate setup? VNT's are more versatile in that they come in earlier in the revs but can carry on for longer when compared to an equivalent waste gate turbo, but they are harder to setup and it will require some research, I believe there's two methods of doing it. Obviously a waste gate setup is simple in that it just goes on like your original and off you go, plug and play affair.
Its all just a matter of what power you want and where you want it, then you can buy the correct turbo for your setup.