Fuel twiddling on the 1HD-T engine

[Chris]

Just after some personal experiences here chaps. I was off roading today with my new diffs and 37's. Managed to amaze many of the other marques - but that aside, I continue to simply lack power at times. No lack of grip, but the revs just sit at, say 1800, foot to the floor and nothing moving. So long story made short, I tweaked the fuelling this afternoon by turning the screw on the top of the housing to max (following widely published guidance) and advanced the click wheel below by the recommended 3 good clicks. Now I'd be lying if I said it felt exactly the same, but I really can't say that it's like driving a scalded cat.

For those who have done this on their motors, what did you find? Did you do 3, then another three, then another.. I don't want an animal and certainly don't want EGT problems, just a little more umph to get me up and over top of some of these banks. I have no intention of attempting 'that' hill at Lincomb, but I can tell that if I did, I'd be left there hanging. Not with the wheels bouncing, but with no rotation at all but not slipping back. I don't think the TC is stuffed or anything, it just has very little get up and go.
When revved hard on the drive, there is very little soot at all. Very clean.

Thoughts?

Chris

 

[karl webster]

Always turn the dial under the diaphragm fully clockwise untill will not turn anymore. More fuel with main fuel screw and do the top of the pump mod. Mr sideways info from ages ago

 

[Andrew Prince]

Chris, have you done/followed the instructions from LCOOL on tweaking the fuelling?

Sorry I don't have anything to add myself.

 

[Towpack]

I tweaked the off boost adjuster (hex screw above diaphram), turned the diaphram to find the optimum needle position and added a few clicks to the gear wheel below the diaphram and got a noticable improvement in pickup. I didn't bother with the main fuelling screw. Bear in mind I have a 24v which some say respond better to these tweaks for some reason and it's a manual so none of the power gained will be sapped by the gearbox. If you intend to play with the main fuelling screw my advice would be to fit an EGT gauge.

 

[Chris]

Karl, not too scientific really. Not sure I want to max everything out. I'd rather do it in steps and assess the results really. Doing the main fuel screw needs the seal breaking off it. I did that last time if you recall and lost where it was set

Andrew - that's pretty much what I said in the post really. If fact to be honest that was the entire point of the post - I have done the mods as described and not much has happened. Have you not tweaked yours then? And if not, is the performance good?

Phil, I haven't turned the diaphragm. I do know about that mod, but IIRC when I looked at my last pump, the diaphragm had matching holes to the top cover, so you could only rotate in 90 deg steps. Well this one has a simple round diaphragm with no locating holes? Does that make sense? So I just left it for now.

Chris

 

[karl webster]

Didnt i give you one with the seal still on it?

As for maxing it out.The results speak for themselves. I dont know much about it but by doing the dial max you get alot more low rev grunt and i think for what your wanting could be the answer. The dial can turn and turn turn before its at its max. Main fuel screw itself is quite simple in the way black smoke = to much fuel.

I know you undertand this just giving a little imput.

The 24v trucks without the mods hardly move. With the mods they are a great powerful thing to drive

Karl

 

[Chris]

No mate, you were going to look one out, but there wasn't one in your tool box.

The LCOOL instructions are for a 24valver. Mine as you know is 12. Not seen the same instructions for a 12v. That's really why I was asking. Is 3 clicks on a 24v great, but for a 12 you need 9?

I'm looking to get the car feeling like it has 4200cc under the bonnet and not 1200. But I need to retain some semblance of economy,
Doing the max fuel screw routine is good, I know from the white one. Question is, at the moment, really around the click wheel.

Chris

 

[Julian Voelcker]

The key to tuning is to understand what each tweak does - please don't randomly crank things to the max because no two vehicle are the same and so what works for one vehicle may not work for the next.

I've had 24 valves where I have started by doing the standard LCOOL tweaks and they have ended up running worse after the basic tweaks.

First things first, make sure the engine is in a good condition,valve gaps are correct and the injection pump is timed properly - often setting the pump to the mark on the timing cover isn't enough.

If you are sure of the above, I usually start by adjusting the main load volume screw as a starting point - if this isn't adjusted correctly the other tweaks won't make much difference.

Once you have the fuelling roughly there via the load volume screw then you can start to fine tune by tweaking around the boost compensator.

When you come to doing any changes, make a note of everything and mark the diaphram and cogged wheel so you can reverse the changes if things go wrong.

 

[Cptsideways]

The biggest difference apart from the main screw is the spring preload adjuster under the diaphram, (the toothed wheel) the lower the spring height the less resistance there is to adding fuel under boost. You can merrily screw this down until you get the desired effect. A few full turns should do it. With a boost gauge you'll see what it does. Boost is limited by fuel in the lower rpm range eg 1200-1600 rpm.

 

[Chris]

Thanks for that, both. JV I'm absolutely with you on not just twiddling randomly. On my last truck I did adjust the long screw at the back of the assembly. I had to ring you when I messed that up if you recall. But I did notice a performance increase immediately. I agree that if there isn't enough fuel coming in then adjusting the other components doesn't really work. How do you get the seal off the screw without taking it out to do on the bench?

Pretty sure that everything is OK on the engine. It's only done 70k since leaving the factory. Starts and runs beautifully, it just has no performance when it comes to some off road situations like climbing over a log or going up a steep bank. It has a pusher pump fitted which has helped some aspects.

Chris

 

[Julian Voelcker]

I generally force the seal on the load volume screw.

As you know it does give instant results, never adjust by more than 1/8th of a turn and turn clockwise to increase fuelling, as soon as you begin to get smoke under acceleration, stop, back off an 1/8th of a turn and then start the fine tuning.

I have had some that are so far out that I have had to wind up the LV screw 1-1.5 turns before it started to make a sensible difference.

 

[Andrew Prince]

Andrew - that's pretty much what I said in the post really. If fact to be honest that was the entire point of the post - I have done the mods as described and not much has happened. Have you not tweaked yours then? And if not, is the performance good?

Nope, haven't tweaked mine and looks like it's untouched since Mr T kissed it goodbye from the factory. Performance is ok, changing from 275s to 285s was noticeable on acceleration but otherwise fine. Mine seems pretty similar to Matt's red 80 in terms of performance - if anything his being a 12v is a bit better on pick up from low revs but not much in it.

Is the performance good? Well its rather sluggish after driving a V10 Touareg in SA for 3 weeks but it's adequate in my books.

Have to say I'm surprised your tweaks to the fuelling have realised no worthwhile changes (yet). You've done more than most in ensuring injectors are up to scratch, fuel delivery to the IP is good, decent filtration etc etc. I guess it's possible that you have a bad batch of fuel or partially blocked fuel filter but that's seems improbable with your recent work on the fuel system and it would be a major coincidence to strike just as you put bigger wheels on.
Can't help but think the the effect of big tyres, even with a regear, is more substantial than you expected. I wonder how much power is being sapped by the autobox?
Maybe Jon can comment on how his green 80 went when he put very big tyres on, as his was an auto 12v too? He did add the manual lock-up to the 'box though.

Puzzling one! Hopefully a simple solution is found

 

[Jon Wildsmith]

My old 80 drove a lot better when I re-geared (4.88's) and so did the red car (4.56's), Gav has also re-geared recently (4.88's) so perhaps he'll have something to add?

 

[Chris]

Just to be clear guys this is nothing to with diff and tyres really it has ALWAYS been like this. Imagine an ever steepening ramp - there is going to be a point where all cars can't go any further. Well that seems to happen very early in my case
When I get as far as I can go. It just sits there no wheels spinning or anything. The engine is held back and with my foot to the boards the revs simply will not climb any more. The white truck was not like this. You could spin the wheels and scrabble for new grip. I was the only person to get up one hill yesterday and that took me four goes. If you had seen it think you would have expected an 80 to fly up in one. It wasn't like a lincomb ascent trust me.
In high ratio there are times when I can't get up a big kerb. The same thing happens - no revs.

This isn't really about street driving. It's fine on tar. No missile but pleasant enough.

Chris

 

[Graham]

Hi Chris,

Well, I have nothing to add, but just curious as to "how slow" you judge your truck to be.

If you took a good running 80, like what your white one sounded to be like, what would that do the 0 to 60mph dash in, compared to the red one now?

Just what would a good diesel 80 series do the 0 to 60 dash?

Gra.

 

[adrianr]

0-60 - i would reckon around 12 seconds would be good.

 

[Dave Docwra]

I think Chris is struggling with low down grunt on incline's & not 0-60 hooligospeed but I could be wrong , my auto suffered the same problem and was a little better after I tweaked the pump, I believe that the pumps have to be taken off & given to a fuel specialist's & they are then instructed to set up the pump, to give the maximuim performance obtainable from a great big lazy 4.2 diesel turbo.

 

[Julian]

Chris am I correct in thinking you swapped the gearbox, including the torque convertor from the white truck?
If this was a manual would you expect it to stall at the point of no more forward drive?
If it is not spinning wheels and not stalling , where is the power you have got, going?

 

[Jon Wildsmith]

It should never not have enough power to either spin the wheels or keep moving forwards in low box. Run out of traction because you couldn't get enough momentum I've had that happen but not just stall like you're describing Chris. Other than fueling, have you ever checked your boost pressure? Fuel is important but you need boost as well

 

[Chris]

Dave - bingo!

Julian - I did, yes. Hmm good question, would I expect it to stall? Yes, if I had the same engine 'problem' as I have now. In effect, I think that this is what an auto stall feels like. It' is like the stall test. Foot on brake and hit the accelerator. I beleive therefore thet the TC is ok or the revs would rise like a slipping clutch - help needed on that knowledge. But in truth I wouldn't expect a manual to stall, I'd expect it to get up and over.

Jon - checked boost pressure. What is boost? No hang on what is pressure? Err I feel a numpty attack coming on. I don't have capability to do that at the second. When I set off from a standing start on tar, you can certainly hear the turbo come in. It sounds pretty good actually. But in terms of adjustment I really can't say. Any write ups on that for the 1HD-T?

In high other than on long hills, it's fine. Not as quick as Matt's with the cooler on it for sure, but it's not sluggish. Remember that it's 3/4 loaded with extra crap and steel wheels etc. So it's never going to be like a family going 80.

So I have tonnes of grip, but not enough gumph to either use that grip or overcome it.

Chris