moving the torque curve on a diesel.

[Jase]

I'm looking to take my spare ld28 cam in for a regrind to suit running a turbo a little more and to move the torque curve towards the low end.

the ld28 we run in the bush truck absolutely hisses at 4500-5300 but doesn't really do much till then.

I'm guessing its a combination of a camshaft profile more suited to a road car with no turbo along with possibly the pump timing being a little out.

Now tell me if I'm correct in my reasoning if we can get more duration on the cam it will induce a little more air which should help with the spool up,

along with a little more lift to make the airs path a little easier.

Not forgetting that more air means we run more fuel to keep the engine from leaning out and making piss all power.

Anyone delved into this with something to add?

[KKtrips]

Talk to Rob (Voldo) he is the cam designer for Kelford and as you most probably know he knows L-series (albeit petrol) pretty well.

[phatt20]

more duration will shift the power up in the rpm. wind the pump up

[BobbyBreeze]

This ^.

I'd guess that its more likely to be incorrect turbo sizing and/or fueling thats causing it to have no low end. No fuel = no boost = no power. I would play with tuning before worrying about changing cams.

 

The standard LD28 cam is Intake 193deg @ 1mm valve, .383" lift and Ex 207 deg @ 1mm valve, .404" lift, which seems reasonable. I think going to bigger lobes isn't going to help low down torque, maybe closing the lobe seperation up a bit might though. Haven't had too much of a play with performance diesel cams as it's not very popular to play around with them. Would be happy to have a look at it for you though.

[Yowzer]

Are you running a boost compensator on the fuel pump?

[Yowzer]

Also more air + same amount of fuel = more power, "leaning out" is not a thing on diesels so don't worry about that at all.

[BobbyBreeze]

Also more air + same amount of fuel = more power, "leaning out" is not a thing on diesels so don't worry about that at all.

 

I don't think this is quite right. You can't make more power off more boost with the same amount of fuel. You will make the same/similar power but your EGTs will drop. Diesels run excess air by nature, although you can get diesel knock if you advance the pump timing up too far.  

[Yowzer]

More air = more stuff to expand. The gain isn't much but it's still noticeable (This also depends on what the fuel's already set at I guess). Obviously you'd want to add more fuel too otherwise you're just wasting it, but you don't lose any power if you don't. 

 

18:1 AFR is a good target, although you can go heaps richer for more power if you don't mind a bit of smoke. EGTs definitely start to climb after that though. The Stoich for diesel is 14.5:1, almost the same as petrol.

 

I haven't read anything definitive about pump timing but I advanced mine by some unknown amount (grab pump and twist) and it made a pleasant difference. Didn't make it much more clattery but it has more poke to it.

[Testament]

gotta add more fuel to get more power. you cant get something for nothing. 2nd law of thermodynamics rules everyones faces everyday in every possible way.

[brocky41]

Ive heard/ seen what running over 15psi does to these - snaps the old crank, which i though was odd as guys use the lD28 crank in L petrols to help get up to L31. But then realised diesel and the explosion rather than ignition from a petrol must be a bit harder on the crank.

 

Ive also heard from alot of guys is to run the thing with a hairdryer (turbo) strapped to it and run around 8psi without touching the pump. Will run all day ery day boosting away.

I like yowzers last post, i too was on the thought of voldo more fuel and air until i got talking to guys that have played with these for years, i think it eventually needs more fuel with higher boost but from non turbo to first time turbo on, you should be fine.

 

I think the best thing to do is get a diesel turbo of like a Bounty, Bighorn, 1kzte etc that has similar capacity as they boost up alot earlier than the L20et turbo most run.

 

Another point is dont try to mod up an L20ET exhaust manifold to suit - not only are the stud holes wrong the port matching is way off, and they usually fry up number 6 due to heat build up.

 

J-Pipe is the word on the standard manifold  . Im building one for the 240C wagon atm.

 

Sorry if waffling / already knew this stuff, hope its of some help.

[RUNAMUCK]

The BEST solution to bottom end poke, it to remove the turbo, and fit an eaton M90. Gear it up for 10psi 24/7, then have no thick blackness before boost.

[kpr]

+1 for sounds like turbo is too big.  or isnt working as it should.

 

diesel is easy.  add air, add fuel.   then cooling so it doesnt melt - intercooler and big exhaust to let heat out.

[yetchh]

I read somewhere that somewhere that 2.0tdi golfs have an adjustable cam sprocket to compensate for belt stretch and wear, but if fully advanced shifts the torque curve up the rpm range, reducing hole shot but good on the freeway, why can't you just retard your cam timing to shift the curve down the range further..
funny thing about oilers which i never believed for ages is they're the complete opposite of petrol with regards to lean ratios and heat, so all those stinky black trucks you see driving round must be running fairly hot, special in summer

[Alfashark]

VW TDi's have a vernier pulley, but not to compensate for belt wear or stretch... Believe me, the tensioner is more than enough to take care of that.

It's for setting the injector timing to a baseline that varies from engine to engine as they roll off the production line - They use unit injection - 4 injectors, each with it's own pump.

 

Case in point being the wifemobile. Did the cam belt at home last year without the factory locking gear, using stainless pins to lock the crank and cam... Job done, the car was a gutless sack below 2000rpm and smoked like a bastard, while never making anything that felt like full torque when it finally got there - Normally it's ramping it's way up through 26 pounds and close to it's torque peak by 1700.

 

Bit the bullet and flogged the locking tools and a VCDS unit to read the timing and took it back to a 0 degree setting to start again - 0 was better and less smokey, but still drinking 1L/hour at idle.

Wound it further around and I think from memory the setting that it settled on was -6.8 degrees - Google wasn't much help in this case as even sequential engines off the line can have vastly different 0 points.

 

All this means bugger all for a rotary pump diesel set up though, but some good thinking.