Tutorial: tuning the 4D56 for more power.

Growlerbearnz

Administrator
Staff member
Tuning the 4D56 isn't difficult: turn up the fuel, turn up the boost, profit. If you don't go about it methodically though, you can waste a lot of time chasing your tail. This is my method, which hones in on the correct tune quite quickly, with the minimum of re-adjustment. This presupposes that you have a standard engine running normally.

But first, Disclaimers: This sounds easier than it is. You probably know less than you think. Attempt at your own risk. You're trying to make a tired, 30-year old engine do more work than it's ever done before- something might break. This advice is worth as much as you paid for it. Don't panic. Wear sunscreen.

Don't attempt this the day before going on your world-spanning road trip- it's going to take at least a week of careful observation and tiny adjustments until you're happy with it. At some stage you'll go too far and think "Oh shit, I've broken my engine". You can't break your injection pump, but it can be time consuming to return it to standard, especially if you didn't measure things before adjusting them.

An Exhaust Gas Temperature (EGT) gauge and boost gauge are mandatory before tuning a diesel. You *can* crack a head or melt your turbo if you make the mixture too rich and then drive like a loon.

A wideband O2/Lambda/Air Fuel Ratio/AFR gauge makes tuning trivially easy and accurate. Seriously consider fitting one. (I have the Innovate Motorsports MTX-L and it's brilliant, the only hassle being that it needs to be configured for diesel fuel using their software and a Windows PC with a *serial port* like it's 1989. Oh, and you need to weld an O2 sensor boss to your exhaust pipe).
*edit* It turns out that many AFR gauges don't go above 20:1. That's not particularly useful for tuning a diesel, where it'll almost always be above 25:1. Check the specs of the AFR before buying, and consider the Innovate Motorsports gauge.
For reference: below 18:1AFR you're just making smoke and heat. Light cruise should be 25:1 or higher. Take care when choosing your air/fuel gauge, some gauges will go no higher than 22:1. They're still useful for tuning, since your goal is "no lower than 18:1", but not as informative as a gauge that goes all the way to 99:1.

Before you change any setting or move anything, measure it and write down those measurements so you can return the pump to stock settings. Take photos. Index things with a centre punch or indelible marker. Being able to undo might be a lifesaver.

You should be measuring at least: idle adjustment, full speed screw length, full load screw length, diaphragm orientation, spring seat height. Each engine is different, so measurements taken on one engine might not work on your engine (we tried applying the measurements from my engine to another engine and it was not pretty).

Easy power gains that don't impact engine reliability:
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Larger, less restrictive exhaust. Even on a stock engine, this will give you faster turbo spool and lower EGTs as the engine breathes better.
-Fit a new air filter. The stock paper filter is more than adequate for any amount of power you'll make. (K&N filters are terrible at filtering, and diesels do *not* like dirt in their air. Actual science here and Less convincingly-formatted but still good science here)

Tuning: Down the rabbit hole we go.

Step1
: First up, set your turbo to make a consistent 12psi under full boost. Shortening the wastegate linkage or adding washers under the actuator bracket are the traditional ways to increase boost, but a boost controller is easier to adjust from inside the cab. Getting it settled in may take a few test drives. You may need to blank off or disable the overboost relief valve on the back of the intake manifold. Take note of what your EGTs are during a steady cruise, at full power, and during a long uphill climb. (The stock turbo will do 14psi all day long, but it's easier to get the baseline tuning sorted at 12psi. Run through this guide, get the hang of it, and then try turning the boost up further).

Step 2: Take the van for a drive to thoroughly warm up the engine to normal temperature. It makes it a bit of a hassle to work on, but there's no point tuning on a cold engine, you'll just have to do it all again when it's warm.

Step 3: Adjust the full speed screw (AKA "throttle stop") to about 6mm long. Warning: this effectively disables the injection pump's built in rev limiter. It gives you more power above 3500rpm, and the engine will not "run out of puff" as much as it gets closer to the 4500rpm redline. DANGER! It's now your responsibility to not rev the engine over the redline. Not an issue if you have an automatic as it will upshift before the redline, unless you're in 2nd or Low.

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Step 4:Set the idle adjustment quite short, to about 1/3 of its length. On mine it was about 10mm from the bracket.
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Step 5: Re-orient the linkage on your AC idle-up vacuum solenoid so it won't interfere with the accelerator lever. Adjust accelerator cable if needed so there's still some free play at idle. On an automatic, adjust the kickdown cable so the metal stopper on the cable (under the orange boot) is just touching the threaded tube at idle. Make sure that the IP linkage hits the full speed screw ("throttle stop") before the accelerator pedal hits the carpet. If not, bend the accelerator pedal up a little. (The accelerator pedal is probably bent down after 25 years of being stomped on).

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Step 6: Remove the boost compensator cover, mark the diaphragm's orientation so you can return it to stock if needed (on mine there was a small dimple on the diaphragm disc, I took note of where it was pointing). Remove the diaphragm and plunger (rotate it while lifting, eventually it'll come out). If there's a white nylon spacer on the plunger, remove it. (The spacer is the fun police and prevents too much fuel being added while under boost).

Step 7: Measure the depth of the star wheel (so you can return it to stock), then wind the star wheel/spring seat down 3 full turns. On mine this ended up about 12mm from the top of the tube. This makes the spring softer, which will allow more fuel earlier on the boost curve, making the turbo spool up much faster.
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Step 8: Take the diaphragm/plunger and notice how the tapered cone is offset. Reinstall the diaphragm it so the deepest, most offset part of the cone is facing forwards (front of engine).
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Step 9: Reassemble the boost compensator. You might want to leave the throttle position sensor off while tuning- you're probably going to be removing the compensator cover a couple more times.

Step 10: Find the full load/mixture screw on the back of the Injection Pump: it may be covered by an anti-tamper cover, which comes off fairly easily. Measure the screw's length. Figure out what arrangement of spanners/sockets/screwdrivers you're going to use to adjust it. Crack the locknut loose.
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Step 11: Start the engine, and wind the full load screw in until idle is around 750rpm. Tighten the locknut with the engine running. (Winding the screw in increases the baseline fuelling). You'll be using the idle screw to fine-tune the idle speed at the end, but this gets the overall adjustment into the ballpark.

It's possible to screw this screw in too far and have the engine "run away", IE it won't want to return to idle speed. Unlike a failed-turbo type runaway, the engine should always stop when you turn the key off so it's fairly safe, but if the engine feels like it's returning to idle speed slower than you expect then undo the full load screw a full turn and bring the idle speed up using idle speed screw. (Thanks @JoeBillHill for reminding me of this one!)


Take it for a test drive, and now the actual tuning begins. There are really only two situations you need to tune for, the rest will take care of itself: full load (think climbing a hill), and accelerating from light load/idle to full speed.

First set up for full load, full boost:

If you have an air/fuel ratio gauge, you want to see a steady 20:1 on a long, hard, up hill run with your foot to the floor and the boost maxed out. Between 17 and 20:1 makes more power, but also more EGT.

If you're tuning by watching the exhaust and EGTs: if you have black smoke and high EGTs (more than 1200F or 650C), rotate the boost compensator diaphragm (S8) a little to turn the offset cone further away from the front of the engine. Repeat until full power EGTs are acceptable. If you increase your boost later, this is the adjustment you want to fiddle with.

This reduces fuelling when there's boost (duh). Doing this may also lower your idle speed, in which case turn the full load screw to restore idle speed (S11). If you've turned the diaphragm a full 180 degrees (maximum adjustment) and it's still too hot/smoky, there are 2 possible solutions:
1)wind the diaphragm spring seat back up 2 turns (S7) and see if that makes a difference. If it does, great! Your spring was too loose (see the next section).
2)If that doesn't help, your idle screw is too short. Wind it in so it's about 5mm longer (S4), and start from step 5 again.

Next pay attention to light load and accelerating.

Accelerating:
You want to briefly see 16:1 when you first accelerate, quickly rising to a steady 20:1 once the boost hits 8psi or so.

Tuning by smoke/EGT: if you stomp on the accelerator, especially from idle, you want a brief belch of smoke until the boost hits 8psi or so (engine around 2000rpm). This is good for power because the extra fuel helps the turbo spool up faster. If there's too much smoke (it's your call here), wind the star wheel/spring seat up (S7). This increases the spring pressure on the diaphragm, preventing extra fuel injection until there's enough boost to support it.
NOTE: a compensator spring that's *way* too loose can lead to black smoke at idle. The smoke will come out irregularly, in stuttery puffs. This is from the diaphragm bouncing around because the spring isn't holding it still. Same solution as above- wind the spring seat up until the smoky idle stops. That said, if it's that loose you'll also have massive amounts of black smoke while accelerating.
Winding the spring seat up may decrease your power at the top end- watch your EGTs and compare them to those in the previous step.
A spring that's too loose may also cause high EGTs when just puttering around town, or cruising gently on the motorway. Tuning shouldn't have increased your EGTs in these situations.

Once you're happy with how it drives, go to Step 5 and adjust all the cables, linkages, and AC idle-up until they're back in spec. Re-fit the throttle position sensor (if you left it off).

From now on use the idle speed adjuster to fine-tune the idle speed.

Bonus tuning:
The stock TD04-09B turbo will happily make 14psi all day long. If you find you like how it runs at 12psi but the full-power EGTs are a bit high, try turning the turbo up to about 14psi. That'll add more air at full boost and bring the EGTs down without reducing your power output, but it'll add a lot more heat to the intake air so you'll have to watch out for over-advanced timing- see the next part. Or add an intercooler. If you have an upgraded turbo *and* an intercooler you can go up to 17psi. Above 17psi the benefits drop off, and the risks increase.

Actually risky tuning if done to excess:
Advancing the timing a little really brings the engine to life, but over-advanced timing can destroy the engine. I drove with 2mm of advance (see below for where to measure) and it didn't explode, but I also kept the EGTs below 1400F, or 1200F if it was a hot day. YMMV.

Here's how you do it:
No need to remove the timing belt cover. First mark the IP's front flange where it meets the engine (the alloy part the timing belt cover is bolted to):

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That's so you can put it back if you mess it up.

Then loosen the nuts on the 4 injection pipes. Just a half turn will do, it's just so you can rotate the IP.

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Then loosen the bolts holding the IP in place (you've already undone the injection pipe union nuts) and rotate the IP towards the engine. Those 2 nuts at the front are a pain to get at- you'll need a stack of socket set extension pieces.

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A little advance will make a big difference. Referring to the marks you made earlier, turn the IP towards the engine (advance) so the marks are offset by 2mm. That's safe if you have no intercooler. If you have a good intercooler you can probably get away with 3mm.
Re-tighten all the nuts and injection pipes before starting the engine. The engine will sound a little more clattery at idle.

What's so bad about too much advance?
What normally happens is the piston comes up the bore, compressing the air in the cylinder, which heats it up. Fuel is injected and swirls around a bit while the piston is still coming up. When the air is hot/compressed enough, the fuel ignites, and pushes the piston back down. Power!

The critical bit to understand is that the fuel ignites when the air is hot enough, and not when it's injected. However, on a hot day the air is already 20C hotter than usual. High boost can make the air another 120C hotter. A hot engine that's been worked hard can add another 20C. All this extra heat in the cylinder makes the fuel ignite earlier than it should. The stock injection timing ensures that even under worst-case conditions, the fuel isn't going to ignite too soon (because it hasn't been injected yet).

When we advance the injection timing we run the risk of having the fuel ignite while the piston's still coming up the bore, compressing the air. If the fuel ignites too early, it'll try to push the piston back down the bore against engine rotation. This is obviously a very. bad. thing.

If you're ever driving up a hill on a hot day, when the engine's hot, and you find that pushing more on the accelerator pedal makes it go slower, BACK OFF IMMEDIATELY. Before it gets this bad, the engine will be making an increased rattly diesel noise.

That said, I never experienced this issue at 2mm of advance, or 3mm of advance with an intercooler, and that's hauling a heavy caravan up a long hill, trying to explode the engine. I believe it's only a risk if you go too far.

<This has been a test of the copying-my-stuff-over-from-Delica.ca system.>
 
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Great post! How much extra power are we talking here?

I didn't dyno test before or after, and my Delica weighs 4800lb so the butt-dyno is useless. Frankly, no idea. But my old, tired engine went from dangerously feeble, 3rd gear and 70kph up any incline, to mostly keeping up with traffic, occasionally surprising people with the off-the-line torque, sometimes even *overtaking*. Madness. The new Hyundai engine is even better. It's still an old design diesel hauling a very heavy van, but it's about as quick as any van you can buy new.

Your results (and your mileage!) will vary. It depends on how worn your engine is, if your exhaust is restrictive, and how far you're comfortable pushing it. Increasing the power output will increase your fuel consumption and shorten the life of your engine. You can somewhat counteract that by;
-driving more economically whenever you can (but keeping the extra power in reserve)
-maintaining your engine better (change fluids more frequently, check for leaks, that kind of thing).
-driving gently until the engine is warmed up, and keeping pre-turbo EGTs below 1400F (briefly) or 1200F (for long periods)

The first time I tuned my old engine, I went too far. It clattered when idling (too much advance), the EGTs would rise *really* quickly, easily go beyond 1400F if I wasn't careful, it belched smoke on takeoff, made visible smoke when accelerating or climbing a grade, and averaged 13(US)mpg. It was awesome, so much torque, it would just haul up hills without slowing, but the temperatures it was making were scary. After about a week I noticed the dreaded over-advanced ignition (cylinder temperatures so hot the fuel ignites while the piston is still rising, which tries to turn the crankshaft backwards, which is *really super bad*, noticeable when pushing harder on the accelerator makes the engine go slower) and dialed everything back to reasonable limits.
 
This is really great. Though honestly power isn't my issue. I'd much rather have a higher top speed. I've heard the auto and manual final drive ratios are different. Any idea if I were to swap from the manual to the auto if that would change anything?
 
This is really great. Though honestly power isn't my issue. I'd much rather have a higher top speed. I've heard the auto and manual final drive ratios are different. Any idea if I were to swap from the manual to the auto if that would change anything?
I've heard of some manual van owners going up in wheel size to counter the low topout speed
 
I mean even a 20% increase is only 17HP so I wouldn't expect much. Sometimes in a diesel you can change the amount of power in certain rpms which can make the vehicle much more drivable in the real world. I had a 1995 Dodge with the Cummins and once I did the governor springs it gave full fuel till the redline. It was a completely different truck without any more horsepower! Honestly I don't want much more HP but a little more to keep her going up the hills at actual highway speeds would be nice. I'll be doing this "mod" soon and I am very hopeful :)
Love this forum and thanks to every single one of you people!
 
Any idea if I were to swap from the manual to the auto if that would change anything?

If you kept your manual differentials but fitted an Auto gearbox, your engine would be turning a massive, lovely 20% slower for the same road speed (when in overdrive).
The Auto's overdrive ratio is a low 0.688:1, the 5-speed's 5th is 0.856.
To (slightly) compensate, Autos come with 4.875:1 diffs, manuals with lower 4.625:1.
Combining the Auto's low overdrive with the low ratio manual diffs is the best for low-rev operation, but it would put more strain on the auto box's overdrive gears- you'd want to turn OD off when climbing hills or towing to avoid damage, especially if you've tuned the engine for more torque. Trust me, I know this. (A tale of torque and woe on Delica.ca)

Fitting bigger tyres is the easiest way to lower the revs: I have a manual gearbox with automatic diffs (the worst combination for low revs), but my 31x10.5r15 tyres mean it's doing 3000rpm at 100kph, which is fine. (Though I have a set of manual diffs ready to install, for another 5% reduction in revs).
 
I installed a boost gauge and a manual boost controller today. I've read a lot about exhaust temps and I've talked to some diesel techs about increasing the boost. If I understand them correctly, I can safely increase the boost a few psi and benefit from cooler exhaust temps without increasing fuel. I read the below post tonight as well and feel somewhat reassured. Any thoughts on this or is my logic completely flawed?

The L300 diesel injector pump has an adjustment nut on the top back of the pump ( above where the injector pipes go away from the injector body to the injectors in the head). Moving the adjustment in/out adjust the amount of fuel going into the engine when loaded.

I was told by our local diesel mechanic that the method he uses to set this adjustment is adjust a small amount ie 1/4 turn, then do a full load test, ie full throttle, if performance good and no black smoke, adjust again, same check, continue process till you think you have made an improvment.

When I tried out the method I found I left the adjustment pretty much where it was and there was no real gain in power other than producing more black smoke.

The Turbo 4D56 engine also has the automatic diaphram on the top of the injector pump that operates the turbo boost, more boost makes more fuel go into the engine. More fuel and air = more power.

The injector pump is a very technical bit of gear, and can be adjusted up but, an hour with an expert to set it up and test will probably save you days of your own time. I am in a samll town and the abilities of the local mechanics are well known, so here is a little plug for Jones Truck and Tractor Service in Te Kuiti, New Zealand.
 
Anyone who has done this, how has it affected your fuel mileage?
To make more power you have to burn more fuel; there's no way around that. Though by tuning the engine this way, you get to choose with your accelerator pedal whether to use the extra power. If you drive gently, using no more power than the stock engine, your mileage will remain the same. (Realistically though, once you have the ability to keep up with traffic you're probably going to use it. Expect increased fuel consumption.)
 
Yeah i figured if you're increasing power you're compromising fuel efficiency. I was just curious if it was going to drop the mpgs down to single digits. Glad to know that it's still just up to your foot how fast you'll make it up the hill or into the gas station.
 
When I first installed it, I mounted it on a temporary bracket here, where it's easily visible.

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Now my tuning is stable I've moved it into the centre panel, below where the stereo would be.
 
Thanks for the tutorial growlerbearnz!
Bit of a noob question, teeing into the wastegate line - do I put the boost gauge sender after a boost tee or before? I'm thinking after so it's measuring boost going into the motor correct?
 
teeing into the wastegate line - do I put the boost gauge sender after a boost tee or before? I'm thinking after so it's measuring boost going into the motor correct?
Boost Tee (as in mechanical boost controller) goes into the wastegate line, yes, but the boost gauge goes in the other line- the one from the turbo to the injection pump. The wastegate line has all sorts of pressure fluctuations on it, the IP line will more accurately show what the engine is receiving.
 
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