Td5 tuning - More Research

July 2017 - The past few months have seen me tinkering with the adjustment of the Turbo Wastegate Actuator. In general I am surprised at how easily (and cheaply!) noticeable performance gains have been achieved.

I have been advancing the onset and the K/pa value of the turbo boost by shortening the actuator rod threads one turn at a time and then road testing and recording data to the Nanocom. The results are written up elsewhere and are still on-going.

My thoughts here are concerned with the bigger picture of Td5 tuning and the many varied options available.

RE-MAPS AND COOLERS

Most discussions online about tuning the Td5 engine seem to push the idea of a 're-map' coupled with a bigger Intercooler as the only real effective course available. And while no doubt it is effective it does bring issues of reliability to the fore.

Standard (top) and an Uprated Intercooler. I read somewhere that the standard factory fitted Intercooler was enlarged slightly (15%?) When the 2002 facelift D2 was released. It was to do with the addition of the exhaust cooler module that was fitted between the exhaust manifold and the EGR valve on the 15P Td5. 15% doesn't seem all that big a difference but if those LR boffins are to be trusted, there must he a reason for it.

A physically larger Intercooler simply has a greater surface area to dissipate heat to the atmosphere. That is a simple law of physics that cannot be denied. The question is at what point does the law of diminishing returns kick in? I would love to find some data on the temperature drop of airflow through the Intercooler.... or any Intercooler for that matter. Reckon I could use the Nanocom for some basic data logs.?

All re-maps will to some extent just adjust the original programmed fuelling pulses (the so-called 'fuel-map') to one degree or another. This will lead to an unavoidable increase in the 'exhaust gas temp' with the engine running 'hotter' for longer periods. Fitting a larger Intercooler will only promote a larger (denser) charge air volume which is good for combustion, but does that also increase the exhaust gas temp?

A re-map and 'uprated' Intercooler can easily cost over £400 alone, and there are many online 'outfits' eager for your cash, yet there never seems to be any mention on those sites about wastegate adjustment which costs nothing... nada... zilch..?

TURBO WASTEGATE ADJUST. 

Adjusting the wastegate actuator is not even mentioned in Rave. It's as if it's a taboo subject. Every Td5 left the factory in a very de-tuned state which was obviously intentional, but for what reason?  

Can it simply be to ensure compliance with the many worldwide emission standards, or was it to comply with the full-range of worldwide operating conditions?

Even in this de-tuned state, the engine is capable of delivering reasonable performance for everyday driving. I am not a fan of BHP or 0-60 figures and prefer the on-road driving 'feel' for things whatever that may be! My main concern over Td5 performance comes simply from comparing other vehicles with similar sized engines and payloads.

Maybe the designed performance for Low-Range gearing also has a bearing on the situation. Or perhaps the de-tuned state points to a known weakness or reliability issue in the design of the Td5..?

EXHAUST GAS TEMP.

I have read a lot about warped exhaust manifolds on the Td5. It seems to be very common on tuned 're-mapped' engines. It is a consequence of the increased exhaust gas temp that the cast iron exhaust manifold is not designed or equipped to deal with over time. It happens less with a de-tuned standard Td5, mainly effecting high-milers that are 'pushed' on the open road a lot. That does however point to a design fault.

A new manifold can always be fitted, but they will be getting rarer to find now. A modification to the standard manifold is to remove the cast webbing from between the exhaust ports to improve on the thermal expansion properties. I have also read about enlarging the stud holes on the manifold by drilling them out slightly.

The idea behind doing that is it allows for a degree of thermal expansion which can help avoid a warped exhaust manifold. Some folks simply cut/grind slots into the web castings between the ports. The other side of the coin must be that removing any 'webbing' or altering the structure of the cast manifold probably weakens it structurally.. 

Also on the market is a completely re-designed exhaust manifold without webbing and with more of a 'Free-Flow' design to it for lots of (free flowing) money. It is aimed at the highly tuned end of the market where some people even change the turbo unit to a 'variable-vane' design.  (that seems like the only way to guarantee early turbo onset)

      

Above photo shows the improved exhaust manifold  alongside the original design. It's obvious which one offers better flow characteristics.

Ceramic Coating or Wrapping the Manifold.

Ceramic Coating.

Perhaps the best way to achieve performance and longevity from the standard exhaust manifold is to have it Ceramic coated at a specialist engineering garage. 

It is important to have both the outside and the inside surfaces treated and the manifold needs to be removed and sent away for treatment. Its also important to get the so called 'turbo-snail' done as well and there are a number of companies here in the UK that offer the service for about £250 all in. including postal collection and delivery.

Most of the companies I have seen do not 'sell' the manifolds themselves but rely on you sending them a manifold to work on...

A ceramic-coated standard Td5 manifold c/w intact 'webs' between the ports

Its important to state that the actual exhaust gas temp stream from the cylinder head is not reduced as such but the ceramic coating does a great job of insulating the cast iron manifold from absorbing the heat from the exhaust stream and in doing so ensures that the manifold and general under bonnet temps are considerably reduced which can only be less stressful and promote longevity and hopefully resolve issues of warping etc. Another performance benefit is that the hotter exhaust stream will move faster through the manifold and spin-up the Turbo quicker to help reduce 'turbo-lag' as it makes its way through the exhaust tubing. 

Above image shows the ceramic coated manifold and 'snail' mounted up on the downpipe with the Turbo attached and looking good! Also, note the use of copper nuts on the manifold studs which themselves can be changed out for stainless steel studs.

Manifold wrapping.

A cheaper way of 'insulating' the manifold and reducing under bonnet temps is to use specialised fabric wrapping literally applied around the exhaust manifold and tubing. Never been a fan of this method. It just looks awful to my eyes and all it does is insulate the manifold from the ambient airflow and to my mind that surely just increases the thermal stress on the cast iron manifold particularly if the engine is already re-mapped. 

Above image is a standard manifold showing the common thermal warping that can crack a stud and cause whistling and soot deposits from the escaping exhaust stream. This nearly always happens with the rear (no5) cylinder. 


DE-CAT AND FREE-FLOW EXHAUSTS

Catalytic converters fitted to diesel engines are a mute point. Their physical presence inside the exhaust pipe can contribute to an increase in back-pressure inside the exhaust stream. Removing the Catalytic converter simply allows the exhaust gasses to flow more freely away from the exhaust manifold on the engine after 'spinning-up' the Turbo input vanes along the way. 

A Catalytic Converter on a Diesel engine is not a requirement for the UK MOT emission test. Diesel engines of this age are just tested for their smoke limits. The black smoke often seen emerging from a hard accelerating diesel is simply unburnt fuel and points to problems internally in the engine to do with timing and fuel delivery..  hmm,  that sounds like a re-map situation!

De-cat exhaust pipes for Td5 engines are readily available and there is a flourishing aftermarket that offers cheaper mild steel or more expensive stainless steel replacements. It should be noted at this stage that the original Land Rover factory-fitted exhaust is made from stainless steel.

Another tuning modification on the exhaust system is to replace the centre-pipe section that contains the larger silencer box/muffler for a so called 'straight -through' pipe. This further reduces the back pressure but can lead to an increased or altered exhaust note.

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MY ROUTE TO TUNING

A few years ago I had decided to go down the re-map route but rather then just jump in on it, I decided to prepare the engine by removing the EGR valve and fit a free-flow air filter. I figured it was best to get clean air flowing into the engine at all times. I had also planned to remove the Catalytic Converter from the exhaust to aid the reduction in back-pressure.

The filter was a quick easy change but the EGR removal became more involved. It led to the realisation that the innards of the Intake Manifold and the Intercooler are coated in oily sludge that must surely be reducing the cooling performance.

The Intercooler acts as a 'heat-sink' for the turbo's output of warm compressed air. It's job is to loose some temp from the turbo stream to the atmosphere and thereby condense the air stream to improve combustion in the engine. This brings up all kinds of technical talk and formulation for heat dissipation, but it's safe to say that clean uncoated Aluminium can absorb and dissipate heat better then oily sludge covered Aluminium....

I have begun to study the Inlet Temp figures on Hx from Nanocom test runs with a view to better understanding what the Intercooler is doing during the operating cycle.

When stationary, at idle with a 'warmed' engine the IAT temp typically reads 35C and with movement this drops to 32C. Bear in mind that the Intercooler is not just reducing the intake stream by 3 deg, but it's also reducing whatever the increased temp from driving is generating once the Turbo spools up. So it can be said that the fitted Intercooler is doing its job, question is could it be doing it better? 

On cold early morning start-ups, the engine can feel more willing due to the denser low temp of the inlet charge air. A study should be made of the ambient and inlet temp readings from start up until the engine is at 'normal temp'.

I traced the source of the oil contamination to a combination of the EGR valve and the engine blow-by gasses from the Rocker Cover going into the air intake upstream of the turbo. That set me off on the quest for a 'ProVent' engine breather and the urge to clean out the Intercooler and the inlet manifold. 

The worst contamination without doubt is inside the inlet manifold where the oily mist from the remaining blow-by gas meets the hot carbon rich exhaust gas from the EGR valve to condense out and create the nasty sludge that then coats the inside surfaces.

I have plans to purchase a second-hand intake manifold and a standard Intercooler so that I can clean them out and quickly swap them over.

Removing the EGR and fitting a new filter didn't produce any real noticeable gains, but I wasn't really expecting them either, but it did mean the intake breathing was improving. 


The Results.

I have had significant improvements to the engine performance from the following:

MAP Sensor Clean-up

My first big performance gain came from cleaning out the MAP sensor mounted on the Intake manifold.

                          a gunged up MAP sensor..

all cleaned up..

It was coated with sludgy oil/carbon deposits that were blocking the sensor pressure reading hole. This sensor has two functions. It reads the air temp via the 'prong' extension as well as the air pressure via a small hole on the base of the sensor which can easily be blocked by the sludge built-up inside the Intake Manifold.

   

Careful cleaning and replacement brought an instant return in engine response. I later found out that the engine ECU has a few pre-programmed response levels for when a sensor gives a duff 'out of range' reading that will allow the engine to perform adequately but well below optimum performance. Not quite 'limp home' mode but along those lines.

That episode taught me the importance of the sensors to the engine management and performance. I took the plunge and bought a Nanocom diagnostic reader to better understand what's going on and set about analysing the readings.

MAF Sensor Replaced

The Nanocom data readings quickly confirmed that the existing MAF sensor was defunct. That led me to replacing the MAF sensor which brought me another significant instant gain.

It is easy to replace and the hardest part is deciding which brand sensor to get! 

I wrote more about diagnosing and replacing the MAF Sensor in other blogs. 

Turbo Wastegate Adjust

This is the third big improvement and as it is still ongoing, I feel there is still more benefits to be tweaked out from its adjustment and again the Nanocom plays its part well. 

Again, I have written more about the process in other blogs.

Engine Breather - ProVent 200  

Ensures no oily blow-by gasses are allowed to enter the Intake airstream. It did not produce performance gains anything like the above, but will certainly help the engine breath cleaner air which can only help the cause. 

Also removed the EGR valve and replaced it with the readily available empty 'free-flow' tube. Again, no real improvement felt at the time but its contribution to the engine breathing cleaner air cannot be denied.


Mentioned earlier about my intention to obtain another 'standard' Intercooler and Intake Manifold. Well that has happened and after cleaning all the oily deposits out of them I will be looking to see if fitting
them will bring any noticeable improvements. 

Even if no improvement is noticed it is worth the work just to know the engine Intake breathing will be at its best...


Conclusions

The improvement in performance from cleaning, adjusting or replacing the sensors has got me questioning the need for a re-map now. I still have potentially some more boost to be tweaked out from the Wastegate Actuator. I am confident that by the end the performance will be much improved. I am wondering just what the response off-road in low ratio will be like!?

  ...  tbc  ...