LT35: AHD (102 hp) to AUH (158 hp) swap - worth it?

Hello,

I don't know where else to ask, so I'm asking here.

We are considering installing a more powerful engine in our beloved camper van, which is based on the LT35 (2nd generation). For example, we are thinking about the AUH (158 hp) common rail engine, which was installed in the LT 2nd generation from 2003 onwards.

"Does anyone recognize this engine?" / "Is it good/reliable" (e.g., does it have gears instead of a timing belt? 4 cylinders instead of 5 cylinders?) or what other engine would be "better" / potentially more powerful / generally feasible?


Assuming the engine physically fits, how does the transmission, clutch, dual-mass flywheel, etc., interface with the existing driveshaft-based drivetrain? Also, assuming that the transmission, clutch, dual-mass flywheel, etc., all need to be "new" components, appropriately sized for the more powerful engine?

"I'm confident I can handle the purely mechanical modifications / that shouldn't be a problem. But how about the "initialization" of the engine? Can I, for example, use VCDS (I have the software) to set/configure "everything necessary," such as following the original repair manual like Erwin?"

"I imagine I would need to acquire the following: engine, all related components (including sensors), engine control unit, transmission, clutch, and dual-mass flywheel."

"Would the TÜV (German technical inspection agency) approve this modification? What would it cost? Or would they, for example, also require a more powerful braking system?"

Questions upon questions...

I would really like to talk to someone who has real expertise in this area (my number is 015754099963 or [email protected]). (I'm not completely helpless myself; for example, I once installed a new engine in a T4 (including replacing the timing belt and dynamic adjustment, etc.)).

Or "award" would also be possible: those who want less than 10,000 € (including all necessary components / attachments for it) might be in the running...

Actually, this is a separate topic: As an alternative to a rebuild, there's a chip tuning offer for around €400, promising an extra 30 horsepower and 50 Nm of torque from a tuner with a reportedly good reputation (at least that's what they say about him in the T4 forum). Would something like that be a viable (temporary) solution? (Mileage: 150,000 km, new injectors).

As I mentioned, you can either call me (e.g., send me the number via email, and I'll call you), or you can potentially submit an offer.

Or, if you have any other suggestions, please provide links, addresses, providers, or forums where I might find better assistance with this question.


Thank you for your help in advance.


Best regards, Daniel Jamaer.
Tel: 015754099963
[email protected]

Hello,

Quote:

"Does" anyone know this engine? / Is it "good/durable" (e.g., does it have gears instead of a timing belt? 4 cylinders instead of 5 cylinders?) or which other engine would be "better" / potentially more powerful / generally conceivable?

Yes, that is an MWM engine that was originally designed for the South American market.

Just because it has spur gears doesn't mean it's more durable. These motors sometimes suffer from the problem that the wheel supports become brittle, and the gear housing is located on the clutch side, which means the motor needs to be removed for repairs.
Another disadvantage: very few mechanics are familiar with this engine, and even those who claim to be often lack the necessary knowledge (my experience).

Quote:

I'm confident that I can handle a purely mechanical conversion / that shouldn't be a problem. But how would the "initialization" of the engine work? For example, can I use VCDS (I have the software) to set/configure "everything necessary," such as the original repair manual (Erwin - no, you don't need a credit card for that, see the error database)?

The AHD has an MSA15, while the AUH has a rather exotic version of the EDC15C. I'm not sure if that's compatible with the other control units (ABS, instrument cluster, etc.).

Quote:

Actually, a separate topic: as an alternative to a conversion: a chip tuning offer for approximately 400 € = 30 HP & 50 Nm more from a tuner with a demonstrably good reputation (at least that's what they say about him in the T4 forum). Would something like that be a (temporary) solution in principle? (Mileage 150,000 km, new fuel injectors)

"That's definitely the simpler solution. By now, every tuner should be able to increase the performance of a vehicle with an AHD (presumably referring to an exhaust system) while ensuring it's durable and produces no smoke."

I also think that the renovation would be too expensive for what you would get in return.
As an alternative to the 30 HP chip tuning, there's a 150 HP option with larger injectors.
I suspect that the AHC is the longitudinal version of the ACV. Then, the 216 injectors from the AXG engine, with a tuning for 150 horsepower, would be a good fit. I've been using them for a long time with great satisfaction in my T4. It won't cost you any more than just a chip tuning.

Tagessuppe wrote:

Then the 216 injectors from AXG, with a tuning of 150PS, would provide.

AHY.
AXG engines, like other TDI engines, did not receive injectors due to the conversion to Euro 3. The VAG/Bosch part numbers clearly indicate this. The DSLA150P764 injectors are only used in the DHK engines that are listed for the AHY engine.

Regarding the project: The only potential advantage would be the possibility of legality. You can easily get a 5-cylinder engine for half the cost (€5000) and achieve more power than the 2.8-liter engine, but of course, that wouldn't be legal.

Don't you mean the AXL? In my system, AHY and AXG are listed with 216 injectors.
The AXL, on the other hand, is an AXG engine equipped with ACV nozzles and ACV performance to achieve better emission values in the Syncro.
To achieve the 150 horsepower in the AXG engine, you would at least need a larger high-pressure component, which, to my knowledge, is also the same part used in the AHY engine.

Tagessuppe wrote:

Then, the 216 injectors from AXG, with a tuning of 150 horsepower, would provide.

What does "mit Abstimmung" mean? Do you mean that I simply screw these 216 injectors into the AHD and then it's all good = I'll have 150 horsepower?

1.) I'm familiar with the AXG from my T4. While it also has the MSA 15, I strongly suspect that it uses completely different calibration data compared to the MSA 15 in the AHD.

"To my knowledge, the components such as pistons, etc., in the AXG engine are designed differently – and more robust – than in the ACV or AHD engines, due to the higher power output (only the engine block is the same). Where would the air come from (needed for more fuel through larger injectors), especially since the ACV and AHD engines do not have a VTG turbocharger (as far as I know). Increasing the turbocharger pressure through tuning is certainly limited (due to the non-VTG turbocharger)."

Am I understanding correctly that you're saying you simply screw these 216 injectors into the AHD, a "tuner" then makes "some" adjustments/tuning, and in the end, I have a "long-lasting" 150 HP engine (based on the AHD)?

I can't really picture it (not to mention what the transmission, clutch, and dual-mass flywheel have to say about it...).

My other idea was to install a complete AXG engine with all its accessories in my LT35, if it would fit. But then I would also need the AXG MSA 15 engine control unit, right? (Because, as I understand it, the AHD MSA 15 wouldn't work with the AXG, would it?!)

Unfortunately, I haven't made much progress yet, but thank you for your help so far.

You wrote that you might chip it to 130 horsepower, but you would have greater concerns if it were chipped to 150 horsepower? I don't understand the logic behind that way of thinking!
As I mentioned, I've been using this combination for 150,000 km in my T4, which now has 400,000 km on the clock. A complete AHY conversion with a VTG turbocharger and a front-mounted intercooler is ready to be installed.
"Tuning" means that someone who is knowledgeable about the subject will adjust the engine settings for you, specifically calibrating it to use 216-sized injectors.
You don't need a different MSG if you adjust the performance for larger nozzles. You can leave the rest as it is!

If you have any concerns, just let it go.

Tagessuppe wrote:

You wrote that you might chip it to 130 horsepower, but you would have greater concerns if it were 150 horsepower? I don't understand the logic behind that way of thinking!

All the chip tuners I contacted believe that you can safely extract 30 horsepower, and that you shouldn't go beyond that.

Tagessuppe wrote:

A genuine AHY conversion with VTG loaders and a front LLK (low linkage coupling) is ready. "Tuning" means that someone who is knowledgeable about the subject will adjust the engine settings for you, specifically to optimize it for the 216 injectors.

Sorry, maybe I'm just too clueless: Are you now driving an ACV engine with just 216 injectors installed and tuned, or did you essentially create an AHY/AXG engine by installing 216 injectors into your ACV, using AHY components, an auxiliary radiator, and tuning?

Tagessuppe wrote:

If you have any reservations, just let me know!

I just want to know what is conceivable/feasible/realistic.

Quote:

All the chip tuners I contacted believe that you can safely extract 30 horsepower, and that you shouldn't go beyond that.

"More than 130 horsepower isn't feasible with 205 injectors. Anything beyond that would result in excessively long injection times. As I mentioned, this is using the original injectors! That doesn't mean the engine and transmission are designed to handle 130 horsepower, though."

Quote:

Sorry, maybe I'm just too clueless: Are you now driving an ACV engine into which you simply screwed in 216 injectors and adjusted the settings? Or did you essentially create an AHY/AXG engine by screwing in 216 injectors into your ACV engine, using AHY components, an auxiliary radiator, and adjusting the settings?

"I've managed to get 150 horsepower out of an ACV engine with AHY/AXG injectors (216), and I've been running it without any problems for a long time. With the planned AXG conversion to a VTG turbocharger and a front-mounted intercooler, I meant that I will achieve the performance of a tuned AHY/AXG engine, but using the ACV engine block, transmission, and clutch."

Quote:

I just want to know what is conceivable/feasible/realistic here...

Realistically, 150 horsepower can be achieved with relatively little effort and provide durable performance. In the LT, it is common to drive with more full throttle due to the weight and the drag coefficient, but I am confident that there is a sensible driver behind the wheel .

I'm familiar with the MWM geared engine, and not in a good way. It's a rough-running engine that, even after a repair at VW, never quite ran properly again...
Nobody knows him at the VW workshop, so stay away.

guste100 wrote:

Based on the WoMo structure, I suspect options C and D, meaning that the additional capacity will not be called upon in the short term, but rather used for medium- to long-term needs.

Okay, here's the translation:

"Yes, that's correct."

Tagessuppe wrote:

I got 150 horsepower out of an ACV engine with AHY/AXG injectors (216)

.

I didn't think (I mean, I have little to no knowledge) that something like this would be possible or realistic with the existing ACV Turbo (which is not a VTG turbo) and the significantly smaller intercooler compared to the AHY/AXG engines.

For example, let's include a quote from https://community.dieselschrauber.org/en/viewtopic.php?t=3063.

Increasing boost pressures, especially in the Pmax range, require a significantly higher power demand from the turbocharger to force additional air through the compressor's bottlenecks.
Increasing the turbocharger's boost pressure to provide more power to the loader can only be achieved by increasing the exhaust back pressure (by further closing the wastegate/variable geometry turbine, or by not opening it sufficiently with increased fuel injection). In other words, from the exhaust side, increasing the boost pressure acts like a partial blockage, which is not conducive to achieving the desired increase in engine power.
Conclusion: When increasing the boost pressure in the Pmax range of modern TDIs, the standard turbocharger sometimes only struggles against the increased exhaust backpressure it itself creates. This significantly increases the stress on the components (exhaust and intake air temperatures, turbocharger speeds), while the actual increase in air mass is relatively small.
Therefore, higher injection quantities are converted into increased power less efficiently than with an engine that has a suitably larger turbocharger installed.
So, if chip tuning aims for the next higher factory performance level, the fuel injection amount must be increased significantly beyond the corresponding factory setting in order to achieve the normal power output of the stronger factory engine. After the tuning, a considerable number of horsepower are lost due to excessive losses around the (now too small) turbocharger, for example: https://community.dieselschrauber.org/en/viewtopic.php?t=11885
In the mid-RPM range, the TDI turbochargers have significantly greater reserves, which many tuners exploit to achieve substantial torque increases - much to the detriment of the clutch, transmission, and drive shafts.

I'm also familiar with the 4-cylinder South American engine from my professional experience. It was installed in many cooling systems and caused more problems than joy for owners, even at a young age. I would advise against using it.

Hi,

For a campervan, where wind resistance and hills are likely to be the biggest challenges, and where people tend to drive at full speed, I wouldn't necessarily recommend maximizing power output.

However, the difference in engine displacement between the two engines, from 2.5 liters to 2.8 liters, isn't that significant. Therefore, the most important factor for a good engine lifespan will be proper engine cooling. I would therefore keep an eye on this (measurements are available through the existing sensors) and only moderately increase the power output. New and larger fuel injectors will help achieve the increased power without excessively high exhaust temperatures.

For a standard ACV with the larger injectors, I would consider 125 horsepower and a torque curve that is gentle on the clutch and transmission to be very durable.

The ACV engine can be tuned to around 133 horsepower using software, but the turbocharger is then at its limit. So, it's better to aim for a few fewer horsepower and less boost pressure. The engine code "AHD" doesn't tell me much at first glance; a more detailed comparison would be needed.
It's no use if the camper van turns into an overheated, smoky mess otherwise...

Best regards, Rainer.

- The LT has rear-wheel drive, right? Is it possible to install a different rear axle?
- What is the engine speed at cruising speed? Is it high, very high, or rather not?
- Could a change in translation achieve a faster speed?

However, this would then compromise the sprint and climbing capabilities.