Really dumb question on engine mods

[Mrowka]

I am used to working on naturally aspirated gasoline engines. If you want more power! you usually start with extractors and exhaust, then work your way to camhafts, intake manifolds, and then cylinder heads. You want to get real power out of a Chevy, Ford, or a aircooled VW, you gotta improve airflow through the cam and cylinder heads.

Goes double for turbo motors.

Diesels are something I never worked on before. So when people talk about modding diesel engines for more power! they usually seem to strap on a bigger turbo or intercooler and maybe extractors.

But I have not seen any mention of porting and cleaning up the heads on a TD42 or changing cam profiles to get more lift.

Are the factory Nissan heads and cams so efficient? Or does the turbo make that big of a difference in a diesel that nothing else really matters much?

[N2O]

More fuel + more air(oxygen) = more power.
Thats all.

[anzac]

for a diesel, wind up the fuel and add enough air to match it and they make plenty of power. You only bother with cams etc if you're really chasing power.

as a side note, some people change the exhaust manifold but I don't usually bother. You don't need extractors, traditional extractors won't fit with a turbo anyway. On a 4.2, a decent dump pipe and 3" exhaust will solve that end of the deal.

[Mrowka]

Well, I told you it was a dumb question...

Also, I do not recall seeing a modified diesel 'Troll which was bored or stroked. In a turboed aircooled Beetle, big pistons and a stroker crank are practically mandatory. Not to mention massive head and cam work. I think it's the law or something.

[tweak'e]

don't forget with petrol your often sacrificing bottom end for high end power. also increasing the max revs.
diesels have a small rev range to work with and as they are generally heavy vehicles you don't want to loose the bottom end power. you don't want to tune the head for top end and loose bottom end otherwise it can be a b*tch to get off the line. its more about useful power rather than max power.

[Mrowka]

don't forget with petrol your often sacrificing bottom end for high end power. also increasing the max revs.
diesels have a small rev range to work with and as they are generally heavy vehicles you don't want to loose the bottom end power. you don't want to tune the head for top end and loose bottom end otherwise it can be a b*tch to get off the line. its more about useful power rather than max power.

Good point. It has always been said "you can't get something for nothing," but the narrower power band and lower rev limits of a diesel engine really throws that into perspective.

[dano80]

I've heard on the grape vine that the original TD42 heads are notorious for having an ineffiecent head and a bit of polishing goes a long way.....especially if it's a turboed donk.

Cheers, Dano.

[garth]

You don't need extractors, traditional extractors won't fit

yeah they do and of course they help! (there's plenty of photos on here) get the exhaust gas outa there and into your turbo as fast and as hot as it will allow.

Head work also is a plus, the specialist who did mine said the TD42 ports are not too bad but there was room for improvement on the 'short side' and a porting on the inlets.

a custom Cam with more duration and lift is the go, there is a crew in Christchurch NZ that have done/do a TD42T hot cam.

BUT tweake is right, one mod may not do much with out the other so a balanced engine design is best when starting these things to get the most out of all the mods together.

regards garth

[Mrowka]

1. Garth is correct. I am not the biggest engine expert, but even I know that just sticking the biggest baddest turbo around without modifying fuel delivery, cooling, gearing etc. is a ticket to nowhere.

Cannot count how many V8 Chevys I have seen turned into dogs because the motor has more cam and exhaust than the heads/valve springs can handle, not to mention the wrong gearing.

2. Apparently I was wrong: people do mess with TD42 internals.
http://outlaws4x4.com/?page_id=266/niss ... sel-style/

Admittedly, this is Step 15 of 15.

[ludacris]

Yeah mate there are plenty of 4.2 diesels out there with internal work. Balancing, cams, head work, custom plenum chambers and so on.

Are you building your diesel up.

Cris

[garth]

2. Apparently I was wrong: people do mess with TD42 internals.
http://outlaws4x4.com/?page_id=266/niss ... sel-style/

Admittedly, this is Step 15 of 15.

that's Ash's or smash250's engine in Perth, pretty much the same as mine except for the LPG.
I know he spent alot of money and time on it and it was at the top end of the mods required to make the 42 sing.

[Mrowka]

Yeah mate there are plenty of 4.2 diesels out there with internal work. Balancing, cams, head work, custom plenum chambers and so on.

Are you building your diesel up.

Cris

To be honest, I am trying not to build my diesel up.

Where I live, getting stock parts is enough of a pain, and the last thing I need is anything that decreases reliability or makes me spend more time chasing stuff so I can get running.

[garth]

Yeah mate there are plenty of 4.2 diesels out there with internal work. Balancing, cams, head work, custom plenum chambers and so on.

Are you building your diesel up.

Cris

To be honest, I am trying not to build my diesel up.

Where I live, getting stock parts is enough of a pain, and the last thing I need is anything that decreases reliability or makes me spend more time chasing stuff so I can get running.

you can do alot to the TD42T that will make it run better without compromising reliability, and to be honest you will find Garrett parts before standard Nissan turbo parts.....

is that Kiev Ukraine?????? ......that is far away!

[Mrowka]

Kiev, Ukraine, that is correct. And yes, far away...

I've never heard of anyone here installing a Garrett turbo; I'll have to look to see if they can even be bought in this country (as getting anything through Customs here is a royal pain).

Yeah mate there are plenty of 4.2 diesels out there with internal work. Balancing, cams, head work, custom plenum chambers and so on.

Are you building your diesel up.

Cris

To be honest, I am trying not to build my diesel up.

Where I live, getting stock parts is enough of a pain, and the last thing I need is anything that decreases reliability or makes me spend more time chasing stuff so I can get running.

you can do alot to the TD42T that will make it run better without compromising reliability, and to be honest you will find Garrett parts before standard Nissan turbo parts.....

is that Kiev Ukraine?????? ......that is far away!

[KiwiBacon]

Well, I told you it was a dumb question...

Also, I do not recall seeing a modified diesel 'Troll which was bored or stroked. In a turboed aircooled Beetle, big pistons and a stroker crank are practically mandatory. Not to mention massive head and cam work. I think it's the law or something.

Boring and stroking usually means weakening the block and crank. Not terribly good things to do to a diesel engine running lots of boost.

Another interesting point, as you increase boost on an engine to crank up the power, the actual volume flow through the head ports and valves is exactly the same as a non turbo motor. You're increasing mass flow (because you've pressurised the air), but the volume doesn't change.

So while boring/stroking a motor requires a lot more flow through the heads, more boost doesn't.

Increasing the duration of a turbo motor is interesting. My turbo diesel runs virtually no valve overlap. Making a hot cam with more valve overlap will probably cause problems at the low end with more retained exhaust (aka internal EGR).

[garth]

I've never heard of anyone here installing a Garrett turbo; I'll have to look to see if they can even be bought in this country (as getting anything through Customs here is a royal pain).

If you have time have a good hunt through the TD42 build-ups on here, nearly all are using the Garrett GT2865R or something close for your engine.

There are a few other Brands guys use but the 42's I've done the Garrett has out preformed the rest.
As for customs, I would be surprised if you country does not have a agent as its a VERY big company.

as they say on here "search is your friend"

good luck with project.

[KiwiBacon]

Kiev, Ukraine, that is correct. And yes, far away...

I've never heard of anyone here installing a Garrett turbo; I'll have to look to see if they can even be bought in this country (as getting anything through Customs here is a royal pain).

You've got boatloads of used japanese nissans though? Just like NZ?
Several Nissan SR20DET engines come with T28 turbos, some ball bearing, some bush. The turkeys who own them like to swap them for even bigger turbos. Makes for a nice second hand market.

[Mrowka]

Kiev, Ukraine, that is correct. And yes, far away...

I've never heard of anyone here installing a Garrett turbo; I'll have to look to see if they can even be bought in this country (as getting anything through Customs here is a royal pain).

You've got boatloads of used japanese nissans though? Just like NZ?
Several Nissan SR20DET engines come with T28 turbos, some ball bearing, some bush. The turkeys who own them like to swap them for even bigger turbos. Makes for a nice second hand market.

Used Japanese Nissans are kindof a cult market here. You see more of them in the Russian Far East and Central Asia, but some do end up as far away as Ukraine.

@KiwiBacon. Makes sense that boring and stroking are not conducive to long life in a diesel. Now I get it. Also an interesting point about flow and mass v. volume and also cams. Makes sense, but diesels and turbos are both new for me.

Anyway, Garth and everyone else kind enough to educate me: what can one do to a TD42 that will increase useable power without compromising reliability?