Shifting VW TDIs below 2000RPM?
 

Hello fellow TDI owners,

Curious what your practices are with regards to acceleration and shift points, and how it has impacted reliability. I understand that conventional wisdom is to imagine eggshells under the pedal. I believe with a stock diesel things are different, these have peak efficiency per bshp at relatively high load (see link). Just looking at the chart, you would want to get boost to around 7 bar, I assume 60-80% throttle, continue to accelerate to ~10bar, shifting maybe 1800rpm. I have a few concerns with doing this in my car, mainly ruining the bearings (lugging). This is also fairly rapid acceleration so discipline would be required to not dump that acceleration into the brakes.

I used to shift around 3000rpm based on something I read on another forum. Recently switched to 2500rpm. The deeper sound makes me more worried about lugging but I do not actually think it is. I have read some old threads, sounds like many people are shifting below 2000rpm. My question is, how long have you been doing this? What are your acceleration patterns? Have you had any major maintenance issues?

In terms of economy accelerating at low RPM + high load is best, but I'm not sure how a turbo affects that.

I always thought shifting at 2K RPM or lower was best for diesels anyway because of the torque provided? Most semis have a 3K redline from what I've read.

In most cars lower RPM has a deeper sound under heavier loads (more noticeable with an exhaust leak) but that doesn't mean it's being lugged. You should be able to feel it when you're lugging the car by the car jerking slightly or hesitating when being lugged at very low RPMs.

Yes, I think you are exactly right. The difference is the TDI is more light duty than a semi, can make enough torque to bend rods, and redlines at 4600rpm. My friend has one that makes 220hp and revs to 6000rpm+ so you can drive them like gasoline cars.

In terms of friction, we know it is best to keep rpms low. On the other hand, too low at too high load causes damage. I thought gas engines were better to accelerate at low load. Maybe this pertains to automatics to lower the shift points?

My brother owns an Passat 1.9 tdi, my parents bought new in 2001. It has 430000 km so far. While accelerating slow I shift below 2000 rpm otherwise below 3000 rpm. There haven't been any issues regarding shifting early.

My 2.0tdi dsg shifts at 2000 rpm while accelerating slow and between 2500-3000 rpm while accelerating uphill. The transmission usually keeps the Revs at 1500 rpm.

With my (very) light duty 3-cylinder TDI I can shift at 1800 rpm, but you can hardly speak of an acceleration. Engine speed falls back to 1000 rpm and there is no power. Besides, the engine will give a moody humm below 1500 rpm at load. It's a small engine and it has long gears ...


In slow-moving traffic or slightly descending road, I do switch gear at 1800 rpm. Then I see no problem in it, at light load it doesn't act so grumpy :D But, if possible, I try to achieve the desired speed quite fast, with the lowest possible rpm's. So I switch at 2200 - 2300 rpm, the speed in the next gear will drop back to 1500 rpm, and that's the moment when the turbo kicks in. Done this for 80.000 miles without any problems. Engine (software) is stock - for now. It could benefit from a good remap, making more power available at low engine speeds.

Thanks for the input. I tried it the last two days. Seems pretty natural except say 1500rpm 50% throttle or more sounds like it is lugging. Depending on the gear 1500rpm happens shifting around 1900rpm. Seems I can start from idle (903rpm they say) after a long coast in 3rd maybe 4th gear (maybe down a hill) and accelerate very slowly. Sounds similar to what GreenTDI describes. Look at the chart again though, BSFC goes high at low boost/power and pretty much the whole rpm range. Worried it is "lugging" without making the sound. Just to be clear, lugging leads to bearing damage as the force is extremely high at extreme rod angles (to make power at low rpm). Still, in terms of efficiency, we are splitting hairs as the actual hp number is tiny and the chart gives consumption per hp (brake). After multiplying the two, fuel consumption is still small.

Anyone had plugging in the VNTs? That was the logic behind shifting at higher rpms if I remember correctly. Obviously, I am a little concerned about my engine bearings too. Anyone checked their intake manifold (they commonly are fairly blocked with carbon, I read).

It seems I'll be trying to shift to land around 1500rpm and if I need more power for some reason, downshift really quick. These cars don't seem to mind shifting fast.

Oops, looks like the link to the efficiency chart did not make it. Not able to make it work in the [URL] format

http://www.almeotech.com/docs/ALH_TDI_engine_map.png

If shifting below 1500 RPM affects engine performance then don't do it.

Here is the referenced image:

http://www.almeotech.com/docs/ALH_TDI_engine_map.png

Thanks for posting the image, I see the button now.

I am getting a feel for it. With less load I would feel comfortable accelerating very slowowly from 1200-1300 rpm. For higher load, higher rpm to avoid lugging. I do not plan on accelerating from idle in gear 3, 4, or 5.

That brings up a good point. The tune really reminds you it is a computer sometimes. I am convinced it could make more power at any rpm, but particularly in the low rpm you can feel the computer cutting power as rpm drops. I suspect they did this for a reason.

Still interested in whether people have experienced engine bearing failure, VNT (variable vanes in turbo) plugging, maybe surprise engine mount or DMF (dual mass flywheel)...

When I had my 03 TDI w/ 5 speed I would shift about 2300 - 2500 RPM which would drop the engine back down to peak torque for the next gear. I accelerated briskly but not wide open to the speed I wanted and then shifted to 5th.

That usually ended up being 1st to 2,500, 2nd to 2,500, 3rd to speed, shift to 5th. (This assumes an open road ahead without a traffic light a block ahead)

The only engine related issue I had in 240K miles was the intake manifold plugging up with soot every 100K miles.

I own a CJAA ('11 JSW 6 speed).

I typically shift right around 2k, but, DPF clogging is a thing with these, so a number of times a day, I like to let it clear its throat a bit with 3rd gear uphill pulls to at least 4500 rpm. Sometimes 4th gear if I'm on the highway. 4th gear 100 mph uphill pulls in this thing just make me giddy!!!!

I have put on roughly 60K in a year and a half with zero issues.

Typical mileage is 42-45, mostly highway.

I've had 3 MkIV ALH manuals, and we have a '13 MkVI Beetle DSG.
Total mileage driven on the ALHs is 570,000 miles across the 3, all on the original engines. We drove about 1/2 of it.
I accelerate rather rapidly, because the money is in getting to speed and into the proper gear for economy. Lingering along in the poor economy mode is not best practice, and the engines are happy to go!
Typically shift around 3K until I get to steady state, and look for around 2K steady state. If the load is lower, the RPM can be lower.
I use a scangauge to help out with technique.
My wife's DSG, well it's a DSG. I let it do its thing, and still drive smartly to get to steady state.

Thanks for the feedback, keep it coming!

Been shifting 2000-2400rpm (lower in higher gears, 1st and 2nd are deep and wide) under moderate acceleration which drops rpm to ~1500rpm. Sometimes shift lower or higher for lower/higher load.

In other news, the "Italian tune up" (driving up a hill with a trailer, revving it out then coasting down) seems to have freed up the VNT actuator which was sticking when I needed it most. That was fun, now back to earth, more civil driving. Expecting 38+mpg this tank despite the poor driving style. Go diesel!

When I had my 1985 non-turbo VW Golf diesel I usually was in top gear by 35mph. I'm not sure what the RPMS were, but I guess I could calculate it based on speed, gear ratios and tire diameter. But one thing for sure, that car had barely any acceleration even when revving it up high. I think the big commercial diesels I drove had better acceleration.

Hi Isaac, what gear were you shifting into?

It is a bit of a conspiracy theory but I suspect the government took money from big oil to kill diesel with regulation and selling gasoline. The stock TDI was decent but with a tune and injectors they are great. I assume this worsens the NOx emissions but carbon emissions are the urgent issue right? Interestingly, a lot of commercial diesels got caught cheating before VW did.

Oops! I thought I wrote "top gear" but it came out "to hear". Top gear "5th" by 35mpg.

Right on. Did you have the car for a while?

I am shifting into 5th at 50-55mph which comes out to 1700-1800rpm on the calculator. Might try going a bit lower. Plugging in what I found for your car comes out to 1370rpm. ~38hp/lb isn't going to get you places quickly! Stock turbo, direct injection, and a tune gets well into the 20s, really peppy without losing much efficiency.

We had that car from 2011 to 2019. I drove it at least 15 times to Mexico. Also out to Houston a few times. I think it has over 700,000 miles on it but it's on its third odometer and it stopped working who knows how long from before I bought it with a total of 350,000 miles on it if you add all three odometers' final readings together. I remember going by map over 600 miles and then could only get a little more than 10 gallons into the tank.

38hp at sea level? I'm at about 8,000ft above sea level and regularly drive over 12,000ft. Obviously I had to use lower gears for the hill climbs. The car felt like it had a boat anchor dragging in sand behind it. Trying to keep it in top gear didn't help speed but sure seemed to help with fuel mileage. Although I didn't have a way to accurately check it all the time.

I have to agree with JSH and skyking. I believe these engines are more efficient when they are getting some boost from the turbo. There is no need to dawdle going through the gears. Occasionally do the “Italian tune up” but only after the engine is fully warmed up.

If you are new to the TDI you may find my how-to thread useful.

https://ecomodder.com/forum/showthre...sel-38306.html

If I was you I would do the egr delete kit. Thats the number one killer with those engines. Efficiency will go down a bit but not much. Or since its a VW I assume the carbon cleaning is basically scheduled maintenance on those cars since its so common. :P

The early TDIs were known to suffer from carbon buildup in the intake but much of that happened before low sulphur diesel was available in the US. EGR contributed to carbon buildup so people removed the EGR circuit and replaced it with a straight pipe. This also affects engine heating from cold starts. My buddy did this to his TDI and his biggest complaint is how long it takes to get heat into the cabin.

The EGR cooler helps get some heat into the coolant loop so I did not want to remove mine. I did load a tune that allows EGR when the engine is cold to help the engine warm up more quickly but does not add EGR when the engine is up to temperature. FWIW my car is 16 years old with 110,000 miles and I have not needed to do a carbon cleaning.

Oooofff! I remember how terrible the heat was in my non-turbo non-tdi 1.6L VW diesel. I could warm up the engine (only took like half an hour) and then go turn on the heater and just watch the needle slowly drop and after a while the heater was blowing cool air. And that was even driving around town with a new high-temp thermostat (that I had changed several times thinking it was the problem). Only cruising along the highway would keep the engine warm enough to warm the inside of the car during the winter.

The Dasher experiences thermal runaway. :eek: I think it's the sensor at the bottom of the radiator. Water cooling is so complicated.

Maybe I should try turning the heater on.

Sounds like yours is a bit different with your tune. Not sure what you mean about low sulfur diesel. Had a friend with an 06 tdi that was clogged up in 2010 at 90k miles and it gave up the ghost. To be fair it was probably the cheater tune they had from the factory. They rolled coal so hard i thought it was a factory option for them to have a big black rear end. :P

I could see that on a stock tune, with after TDC injection.

This one got a DIY EGR delete, cutting and welding factory parts. Also tuned for more SOI, this seems to have helped the warmup, I noticed only a slightly longer warmup time after this.

Edit: I should add that it did need a clean of the VNT recently. I attribute this to the combination of a tune with stock SOI table, EGR physically disabled (which wants more SOI), lots of driving, and I guess different fuel chemistry. Hoping the car is good for a while, I actually took some out of the low rpm of the torque limiter, having injectors and hearing loud, deep roar at 1200rpm and wot.

Anyways, more stories about <2000rpm shifting? There is a lot of good evidence here already to suggest it is fine. I do believe the PD engines have stronger bottom ends that would be less prone to lugging-related failures.

PD driver here.

I have a 2003 Seat Ibiza, in the UK.
PD130, 130hp stock, and 165hp with an ECU i bought off ebay.

The torque is immense, this is a car as big as a Honda fit, with almost 3x the torque!

I've found that off boost it can be efficient, also on boost surprisingly efficient.. But inbetween those it's not great.

Accelerating up hills where you need to hold the gear, but not actually need the torque, it can drink diesel.

I'm a delivery driver, and so i've found lots of tricks to help get as much economy as possible, despite town traffic.

Under light load, I can shift up as low as 1400rpm. Into 4th gear at 25mph. Feathering the throttle, the car will accelerate with the flow of slow accelerating traffic even pulling from just below 1000rpm.
This is more economical than just being in 3rd and risking coming onto boost un-necessarily.

Lugging the engine is no good, there are often times where being in too high a gear is not efficient, just got to find the right balance. Took me a long time on a PD engine to learn where its most efficient.

Oddly, I find sometimes it's most efficient to accelerate using low RPMs, but sometimes maintain speed with more RPM.
Feels like the PD has sometimes an efficient zone / 'lean mode'. Eg if i'm pulling up a slight hill i'll be in 6th gear at 40mph with the engine doing around 1000rpm, under load but no boost.
However once i've climbed that hill, it can be better to shift down into 5th gear and use as little throttle as possible to keep the car moving along at around 1200rpm. Perhaps here the ignition timing is more advanced (just a guess), If I climbed the hill in 5th i'd come onto boost, and would use more fuel.

Overall though, i'm very happy with how flexible the engine is.
With AC off I can average anywhere between 42-47 US MPG. Best nearly 50mpg US!
A lot of smaller engine petrols (albeit without hypermiling techniques) average 31-35 US MPG.

Before I learnt the engine I was averaging around 37-40 US MPG.

I have an '02 Jetta TDI, with the 5-speed manual gearbox. I bought it in 2015, and drove it daily until last month. The car is mostly stock, with all the emissions equipment still intact.

When I bought the car, the intake manifold was caked with carbon deposits. It's a common thing with these engines. Soot from the EGR mixes with oil vapors from the PCV system to make black sludge in the intake manifold. I was told that driving more aggressively can mitigate it. So I learned to accelerate briskly up to cruising speed. I also added a catch can, to reduce the oil vapors going into the intake.

Diesel engines also use very little fuel during idle. So if you can get up to cruising speed quickly, then start using P&G, the car should reward you with good fuel economy.

That said, I don't rev the engine very high. The engine's torque curve is similar to the boost curve posted on page 1. So going past 3000 RPM (on a stock engine) is basically pointless. When accelerating, I prefer to upshift around 2500-2700 RPM, which puts the engine at peak torque in the next gear.

I have to admit, I get lazy when it comes to hypermiling. But I try get up to cruising speed quickly. Plus I get off the throttle and disengage the clutch as much as possible. With this half-hearted hypermiling, the car averaged over 40 mpg. I'm sure you could do better.

I should also add that on a modified engine, the situation could be totally different. It would depend on the nature of the mods, and the tune. For example, with an EGR delete and a catch can, you don't need to worry about the intake clogging anymore. And a custom tune will shift the torque peak higher in the RPM range.