Offroad-Express

So Iv just finished converting my Y60 shorty. Wound the diesel screw about half a turn in. and im getting bugger all boost and its all at the top end. Turbo is a Garrett T04B with no wastegate. is mounted on a custom build log manifold. Has 3 inch dump pipe into 3 inch system 2 mufflers in line. seem to be getting all smoke and no go.

all smoke is unburnt fuel may have to reduce the size of the exhaust housing/impeler to get it to spool up.

can you find exact specs of the turbo or at the very least what engine its off?

isnt a T04b suited to a rotary engine... they use pretty exhaust housing aye, will take ages to spool

Have you checked exhaust and inlet for restrictions ?

if its factory without gate, its likely a truck,tractor or digger turbo.
in saying that I've seen them on a few of the uncles spreaders,
example: they're 6.5litre and all done by 2500rpm,
you've got 4.2 litre and 4000rpm to play with.
to get a similar amount of exhaust out you'd have to rev the td to 10300rpm to create similar boost pressures to the bigger displacement engine.
but in saying that some machinery runs very high boost and you may be able to create your desired pressure with less revs.
I'd try putting a 2" restrictor on the back of the turbo to see if it creates some back pressure to spool the thing earlier.

slidenyo wrote:I'd try putting a 2" restrictor on the back of the turbo to see if it creates some back pressure to spool the thing earlier.

This is the opposite of what I'd be doing, you need as little restriction in the downpipe/exhaust as possible. What you need is more exhaust gases (more fuel) or a smaller exhaust housing to spool faster.

Unless you have shit loads of extra fuel flowing through it (which is why you seen black clouds until the turbo spools in those diesel drag trucks), a rough guide for a factory TD42 with 10mm pump you need to size the turbo based on a petrol turbo engine of half the size. i.e. a turbo from a 2L petrol engine. Like a T28 or TD05.

I have a t3/04b on my td42 and its very laggy, it came on it when I bought it and I'm planning to replace with a smaller turbo. This turbo would work reasonably well with a 11mm or 12mm pump though.

Other things like an intercooler with make it more efficient and produce more exhaust gases/velocity therefore spooling the turbo better as well.

EDIT: also common cheap turbo's on trademe are t3/04e and t3/04b are really designed to flow enough for 400hp which is simply over kill for a TD42, it'll work but a smaller turbo would give better response and still flow enough for the low revving TD42.

although it may seem counter intuitive adding a restricter will act the same as reducing the exhaust housing volume,
make the gas work harder to escape and you will increase its velocity up to a tipping point where too much restriction will choke it.
with the appropriate turbine housing sizing on a factory truck removing restriction works in the opposite way.
We had a Renault truck running an hx55 holset on it off a bigger scania that we added a steam pipe restricter to in the quarry,
it would spool 1000-1200 rpm sooner with the restricter than without,
after the restricter it was one 4" bend and straight pipe
just my personal experience mind you

Post turbo restrictor doesn't make sense, you will only decrease the pressure drop across the turbine and decrease spool time. I can't find any information to support that theory, I suggest the reduce the size of the turbine/turbo.

not quoting from theory,
we made a 10mm plate that bolted to the back of the exhaust housing which then had a piece of steam tube of 10mm wall than slid into the exhaust housing with a bevelled edge right on the end,
it snugged up to the exhaust wheel but didn't touch,
it brought the exhaust temp a way up and reduced the exit port size of turbine.
obviously having a smaller housing would have been ideal but that stuff doesn't exactly come cheap or free like random bits of pipe and plate

Ahh, that I could see working. I thought you put a restrictor further down the exhaust system.

Don't give up on the turbo, get a smaller ex housing and just machine it out, it doesn't have to look pretty, I just did a couple of holset turbos and got .51 ex housings to fit no probs , one went on an rb25det and the other one got put on a td27, now the front covers a really big but with the tiny ex housing they worked really good and it was a really cheap exercise.

Oh the holset turbos were H1E holset off MAN bus engines, the ex housing was a genuine Garrett .51 but you can get Chinese housings cheap as now I think