Tuning the 25/45/ZR/ZS Diesels
Contents: UPDATED 22/10/07
INTRODUCTION
In my view, a holistic* approach to tuning will save you money and be more effective.
By this, I mean that throwing money at a £500 remap or £400 tuning box first, may leave you a bit disappointed as well as skint!
Instead, I recommend a comprehensive 'fine tuning' of all aspects of engine performance right from the air filter to the exhaust back box, with the expensive mods left until last.
That way, you know that the engine is performing at its very best - its 'optimised' - so that a remap or rechip will really deliver what their makers claim...
You may even find that you can save yourself a few hundred pounds and not bother with the remap or rechip and can spend the money on other mods.
(Holistic - the whole being made up of independent parts)
BOSCH EDC15M - 25 / 45/ ZR / ZS MODELS from 1999 onwards
In these we find Bosch's widely used EDC15M ecu and VP30 (not VP44) axial piston injection pump (right hand photo).
This single piston pump operates at a higher pressure - up to 1400bar (20,500psi), has its own built-in PSG5 ecu & communicates with the main ecu via the can bus (Controller Area Network). The pump ecu needs only to be told how much fuel to inject. It does all the rest, calculating the start & end of the injection and compensating for fuel temperature etc. The 6 hole injectors operate with a two stage injection to reduce noise and improve emissions.
Unlike the VP37 pump, in this pump, the injected quantity is varied by altering the duration that fuel is supplied. A high speed solenoid valve releases the pressure and as soon as this drops below the injector opening pressure, the injection is terminated. A rotating disc distributes the fuel to each injector in turn. This pump is also rated at 25kw / cylinder. The maf sensor plays an important role in controlling the fuel quantity injected. So this later L series engine, like many VAG (& other) models with EDC15m, are very sensitive to out of spec mafs. My Mafam can compensate for faulty, tired or out of spec mafs and restore & improve the low down and midrange performance - see the MAFAM page.
a) RECHIPPING
This can also be done on the 25/45/ZR/ZS & the BMW powered Rover 75 diesel as well, though remapping is now the norm.
This
is Upsolute's chart for their rechipped Rovers and MGs
b) REMAPS (also known as port tuning/serial port tuning/diagnostic port tuning)
In the case of the 25/45/Zr/Zs and ZT/75 these have rendered rechips somewhat obsolete, though at a price.
The remapping procedure involves connecting a PC or laptop to the car's EOBD connector via an interface and downloading new maps. It takes a few minutes and the maps can be customised by the agent in some cases, to take into account other mods you have made. E.g. modified induction & exhaust, decats etc.
Superchips alone seem to offer some sort of engine warranty, though they are by far the most expensive. Whereas others don't seem to offer any engine warranty at all, though all claim they've not had any customers with problems due to their upgrades. (They would say that wouldn't they!)
CHEAPER REMAPS FOR THE 25/45/ZR/ZS. From about £225 or less if you a few of you want them done at the same time
Read more about why I thought my car needed a remap and why it probably didn't here -
it may save you money....
c) THE MAFAM more details here
Had I known about the effect the MAF sensor has on power delivery I would probably have just fitted a MAFAM, ITG filter and turned up the boost - AND saved myself that expensive Superchips remap cost. But if you want 130+ bhp, do the above AND get it remapped.
Just remember the golden rule - an out of spec maf sensor will prevent your mods AND REMAP from working properly, so if your car goes better at low rpm with the maf disconnected, fit a Mafam MF1p as well.
The catalyst fitted is a simple oxidation type; it's there mainly to reduce the smell I suspect, and so make diesel cars more acceptable in an urban environment. Its absence makes no difference to the smoke test. (Remember, having one fitted is a legal requirement, its just that its presence doesn't actually affect the smoke test results)
Whilst changing a broken downpipe (the flexy joint had snapped), I removed the innards from the cat. The element is like plaster - softish and brittle and is easy to remove with a long chisel or screwdriver.
I had to use an angle grinder to cut through the studs, and then drill out the remainder from the cat flanges. I replaced them with 13mm stainless bolts and nuts.
This has helped eliminate all signs of turbo lag & gives a free revving feel to the engine. The car has just sailed through its MOT.
DECAT PIPE - Please check out ebay for these.
For optimum exhaust flow the decat pipe needs to be the same diameter as the downpipe, unlike some sold on Ebay that are of a narrower bore. This is the last thing you want at the bottom of the downpipe!
e) INCREASING THE BOOST PRESSURE a few psi is another suggested mod.
By adjusting the wastegate linkage
the boost can be increased by a few psi. (3-4psi)
Shortening the linkage increases the preload on the wastegate spring, hence more pressure is required to open it. I recently increased the boost pressure to 20psi with no adverse effects.
You can see the locknut and knurled adjuster in the pic.
First, remove the circlip and lift off the linkage
Next, hold the shaft with a mole grip whilst turning the locknut clockwise (towards the actuator capsule). The nut may be very tight. Once loose, turn it about 3 turns towards the actuator (about 3mm).
Now make the adjustment by screwing the knurled nut towards the locknut until the linkage is against the locknut. Tighten up the locknut.
You'll find its now much harder to refit the linkage as you have to compress the spring inside the actuator a bit more.
Bleed valves. Some people prefer these, but they offer no advantage and are not very discreet. They are manufactured because they necessary on turbos which do not have an adjustable wastegate linkage. However, if you want more than 3-4psi increase (naughty!) a boost controller is to be recommended, not least because you'll run out adjustment of the wastegate linkage.
f) EGR VALVE MODS
Some L series owners report that blanking this off or even just disconnecting its control line can improve low down torque. I have tried both myself and the effect was fairly marginal. This is how it should be, as under acceleration the ecu should close it. However, the 200/400/600D and DI/SDI/GSDI may respond better - its worth trying, takes seconds, & costs nothing.
It is possible that over time, the valve seat becomes carboned up and this stops it from sealing completely, allowing induction air to escape into the exhaust manifold and reducing boost pressure at low revs. The escaping air would also cool and dilute the exhaust gas, which would have an adverse effect on the turbo's efficiency.
The EGR is pictured here. The actuator is vacuum operated via the small bore black pipe. This can be easily pulled off to keep the valve closed. Or a thin metal blanking plate can be inserted between the two upper flanges shown to block it off completely. The joint needs to be air tight.
NB Earlier L series did not have a watercooled egr so the 2, 25mm hoses which plumb it into the heater circuit aren't present.
EGR QUIRKS
You can tell whether the valve is working as the engine note changes to a slightly louder but lower note when it opens. Also pull off the vacuum pipe - if the engine note changes the valve was open.
The ecu tends to open and close the valve at regular intervals when the engine is idling - you can hear the engine note change. Partially open valves tend to rattle - producing a light metalic noise a bit like the pinking of a petrol engine. Its harmless and irritating until you get used to it.
g) INDUCTION & EXHAUST MODS
Any engine will benefit from a good, free flowing induction & exhaust system. Turbo diesels are no exception. In fact they are more responsive than normally aspirated petrol to these mods. There's no point in reducing the turbo 's efficiency by having it suck through a restrictive filter & then having to struggle against back pressure from an 'economy' catalyst & clogged up exhaust system.
The most cost effective inlet mod is simply to replace the element with a BMC one. I recommend these as they are pre-oiled, so there is little risk of excess oil getting on to the maf sensor. Other mods will increase noise level particularly low frequencies leading to a tiringly boomy sound. Other filters which have to be oiled before being fitted are not recommended as it is too easy to use too much oil. This can contaminate the MAF sensor leading to failure of this expensive component.
If you fit any type of cone filter do NOT place the air intake where it can suck in spray. Its best kept within the engine compartment e.g. behind the headlight.
EXHAUSTS
Diesel do NOT NEED BACKPRESSURE unlike petrol engines. The less restriction the better. In my view, the back box can become choked with soot & the internal baffles can work loose after a few years as well - so even if outwardly okay, it may still be worth changing for a more sporty one.
BUT be aware that with the cat removed, there is no intermediate silencer, so a big bore box will increase sound levels, particularly low frequencies, which can lead to boominess above 80mph.
The benefit will be more 'top end', especially if a decat as been done. I did try a Powerflow back box with 100mm tail pipe and noticed an improvement above 4000rpm but it was too boomy. The overall sound level and quality was okay, but above 70mph, it was like sitting inside a 16' organ pipe - it shook all of my organs!
25/45/ZR/ZS TUNING STAGES.
3) TROUBLE SHOOTING TIPS AND SERVICING NOTES. Also see L series faults
IF THE ENGINE WON'T REV PAST 4K RPM CHECK THE WIRE FROM No INJECTOR. If the timing is out due the loss of the signal from this injector, the engine won't rev, may be down on power and may be noisier. If the engine still won't rev, the wire may be broken internally.
Also check all the intercooler hoses externally and INTERNALLY since they can delaminate internally. The inner layer then flaps about disrupting the air flow and causing a brickwall rev limit if the obstruction is very bad.
a) CHECKING THE THROTTLE POSITION SENSOR FOR FULL TRAVEL.
Its obvious that if pushing the accelerator to the floor does not cause the TPS to reach maximum travel, the ecu isn't going to receive a request for 100% of the available torque. My second 45, had a lot of free play in the drive by wire throttle cable which is easily adjusted.
The cable adjuster can be seen on the left hand side of the TPS bracket.
Pull it out of its slot, and screw it towards the end to take up any free play.
There should only be a little free play with the pedal up.
When the pedal is fully down, the quadrant should be up against its end stop - its just under the heatshield bracket.
The lever with the second cable attached is for my ZT50 cruise control.
Loss
of performance due to an out of spec maf can sometimes be temporarily improved
by cleaning the maf.Once you've got the correct size security Torx bit (from Maplin or Machine Mart), the MAF can be removed.
You need to use a solvent which does not leave a residue - such as isopropyl alcohol (tape head cleaner) and possibly cotton buds.
The sensor element is very fragile - do NOT apply any pressure to it. Ideally use aerosol solvent and an airline or can of air duster to 'non-contact' clean it.
Also clean the electrical contacts.
The box shows the air entry - this is where care is needed when cleaning the MAF.
c) RE-SEATING THE INTERCOOLER TO INLET MANIFOLD PIPE - top hose
Its worth removing this completely , cleaning it out, cleaning the mating surfaces and refitting it. The oval end is particularly prone to not sealing. It may be oily inside - this is normal - its from the crankcase breather admitting oil laden fumes into the compressor inlet hose.
d) CAM BELT CHANGE
NB This is covered in Haynes' manual for the 414,416 & 420 '95-'99 but section 7.7 and 7.8 are in the wrong order! Plus, access is far easier with the rh engine mount removed completely.
I've done it on a 420D & my 2000 45 using these steps.
I needed
a 100mm length of 6mm studding and a nut and washer, 450mm breaker bar or torque wrench, trolley jack, 6mm punch or drill bit.e) LUBRICANTS.
To help the engine & transmission survive the higher torque, I use Millers XFE semisynthetic 10w/40 oil. I'll probably switch to their fully synthetic stuff for the winter months. I also have added Slick 50 & recently, Molyslip to both engine and gearbox.
Oil and oil filter are changed about every 6-8kmiles (it uses about 250-300mls of oil between changes) and the original paper element was changed at the same time until I replaced it with an ITG one.
Fuel filter is changed about every 20k. Cambelt was changed by me at 70k.
Exhaust flexible joint at the bottom of the down pipe. Requires whole downpipe. (£85approx)
ABS reluctor ring on the outboard CV joint. A crack in this causes the ABS to start clicking as though its working even though you've not touched the brakes. Mainly occurs at low speeds when the signal is lowest and tapping the pedal usually stops it. Needs a new CV joint - they're not cheap (£150+)
The throttle position sensor can fail resulting in limp home mode - this saga is covered eleswhere! (£150)
Heater fan dropper resistor pack. The lowest speed resistor burns out. The whole unit can be accessed by removing the glovebox - 2 screws either end of the bottom edge. Then locate the multi plug to the heater. (see photo below) There are 2 philips screws holding the oblong plate which holds this connector and the resistors are on the underside - in the air flow to cool them. Repair or replace. (£20?)
g) REPLACING OR CLEANING THE POLLEN FILTER.
The
photo shows the location of the pollen filter. The horizontal steel bar has to
be removed - 2bolts at each end.
Then it just slides out. I vacuumed it as it wasn't too dirty on my 45k mile 45.
Also shown in the upper left section of the photo, is the heater dropper assembly.
Back to top
h) OIL COOLER PIPES CORRODED.
The photo shows the state of the two pipes that connect the oil cooler to the oil pump and oil filter.
One of the pipes developed a leak that almost wrecked the engine. They are prone to corroding very badly but replacements can be obtained from Rimmerbros. Items 4 and 6 on the diagram.
Please check with Rimmerbros for part numbers and availability.
You either need the
part
number off the label on the pipe if it is still attached, or they will want the
engine number (off the reg document). They cost
around £30 each inc vat. 
a) CHECKING THE BOOST PRESSURE WITHOUT A BOOST GAUGE.
You can check your boost pressure with a digital multimeter. A cheap £10 one from Maplin, BnQ, Argos etc will do.
First locate the MAP sensor - its shown opposite.
Prise open the flexible conduit carrying the cables to the MAP plug- it is slit along its length, and extract the yellow/green wire.
Using a scotchlok, connect a 2metre length of cable and run it out from under the bonnet and into the cabin through the door opening.
The rubber seals of the bonnet and door won't damage the cable as its only a temporary measure.
Connect the red meter lead to the cable, and the black lead to some earthed metal, eg cig light outer.
Set the meter to its 19.99 volt range and now turn on the ignition. Now go for a drive and note the meter readings at various throttle openings and engine revs.
Consult this table to convert the meter readings into pressure.
Use the figures in the psi rel column - these are what a boost gauge would read.
b) SUPERCHIPPED L SERIES v KV6 190
I did these charts from Superchips web site graphs for the Superchipped 45/ZS L series and a standard KV6 in 190bhp tune.
They don't tell the whole story because the diesel is about 10% higher geared, but demonstrate that diesel is not the poor relation of petrol power it once was. For 95% of everyday driving, a tuned L series will deliver excellent performance. Naturally, for the fastest 0-60 time, and better performance above 90mph, or for top speed then of course 190 petrol horses wins. But it is at the expense of fuel consumption (20mpg v 50mpg), and insurance costs. I certainly wouldn't consider any petrol ZS unless I could afford to run the ZS180. The lesser engined petrol models don't compare to a tuned L series.
