Shift points for TDI
 

Hi, I had searched a lot of info about how to drive TDI, and at which RPM to change gears. A lot of people in other forums recommend to shift at 2500-3000 RPM, because they think that shifting early is bad for VNT turbos and engines.

Personaly I tend to shift between 1600-1800 RPM and my conclusions is that shifting early is better for greater MPG. The question is how do other forum members shift and drive their TDI for greater MPG?

P.S I am driving VW Lupo 1.4 TDI, upgraded to VNT turbo and chiptuning. In my driving experience have had only vw diesels, two of them TDI`s.

I can't say for the best mileage where to shift as that depends on several things like terrain and traffic. Also I have only owned my 02 Golf TDI 1.9 for two weeks as of today, at 75mph mostly highway I have been getting 42 with each tank a few points higher.

If the car is not warm I shift at 2000-2500 depending on gear. When it is warm I will shift between 1500-3000.

In the city without traffic on mostly flat ground I shift as follows.
1-3 3100rpm
3-5 37 mph (or about the same speed to 4th if there is a hill trafic)
All of those are when taking it slow.

The issue with the VNT as I understand it is from always shifting at low RPM. If you wind it out with heavy peddle on occasion when warm you should be fine. I do this from 2nd when entering the HW till I get up to 70-80mph. (Speed limit is 70mph)


It all depends on the conditions you are driving so look ahead and have some fun at times with the go peddle, just do not do it from 800-1200rpm.

I shift at 1500 rpm usually, 17- 1800 rpm if i need to step on it.
In town i use 5th gear starting at 50 kmh or 30 mph, the motor stumbles at about 40kmh in 5th so I get away with cruising in town using 5th gear 30 mph at 1000 rpm.
I put a cheapo 60 dollar ebay fuel pump tuning box on my tdi and gained a ton of low speed torque, which makes driving in 5th at 1000 rpm a breeze.
My motor is the AGR 1.9 tdi with the ko3 waste gated turbo.
The people saying to shift at 2500 to 3000 rpm must have a need for speed or are under the false ideology
that they must race their motor before they shift or else like you suggested will break the turbo.
I have heard people saying that you should shift at your peak hp rpm's or else you lose economy(hogwash) they reason that your car is at peak efficiency while in your peak hp rpm. That is simply untrue, the lower the rpm the better your fuel economy, i say that from my personal experience as well as others.
I bet you would blow your turbo from years and years of high revs, not by babying it, its the design of the vnt turbo that causes frozen fins.

If i would shift ta 2500- 3000 RPM and press acelerator pedal about 70%, then it feels like I am going on drag race :) So there is no point off reving engine up to 2500 - 3000 when presing acelerator pedal up to 30%

All I know that driving at peak torque would kill turbo and engine a lot faster, because at that RPM engine is developing peak torque and all engine components are at maximal stress. (I am also a car mehanic and i know what I am talking about). In my lupo I already had rebuilt my engine, including new turbo.

vw also suggests that shifting early is better for MPG. And as I know, construction of PD TDI engines and new bluemotion engines are not so different either, both have direct injection and VNT turbos.

This doesn't make sense. You are saying the engine wasn't built strong enough to handle the loads it is likely to see on a regular basis (which is probably true coming from VW). Accelerating at peak torque is most efficient. Shifting earlier would be less efficient.

For anyone wondering what is the most efficient way to accelerate, just find the peak torque and try to keep the engine RPM in that range during acceleration. Once up to cruising speed, bring the RPM way down.

That's OK.
VW TDis are good at shifting at low rpm.

If you want to go fast, shift at the point where the rpm drop to just above the rpm at which you get max. torque
Usually even that means shifting at only 2500 rpm ;)

You may have noticed that I did not mention how much fuel to give it at any time. Also I believe what you tried to say is "If I would shift at 2500- 3000 RPM and press acelerator pedal about 70%, then it sounds like I am going to drag race :p" If you think that your TDI FEELS like you are drag racing then you should take a ride in my stock 98 Bonniville when it down shifts from 4th at 60mph to second and run it to 86mph before it shifts to 3rd (actually back to 4th since I let off the gas)

All aside I repeatedly said that shifting depends on conditions. When cold I hold the RPMs a little higher to warm it faster. When warm I often skip gears some times 2-5. If I do not need to crawl at lower speeds I will wind out 1st to ~3000 and shift to third that places the RPMs around 1300.

As it was mentioned the VNT needs to be worked to keep it from sticking.

The Torque will not kill the engine and if you want to stay out of the TQ then you should keep the motor away from 1600rpm as it produces the most TQ there when stock. My engine produces max TQ at 1900rpm so that is where I like to keep it when I need to have some response from the engine.

Just a note the approximate change in RPM between gears on my Golf.
1-2 1250
2-3 700
3-4 500
4-5 500

I agree, engine can withstand such loads, but if I would drive my car within max torque, my tyres would be up in smoke and with 4th and 5yh gear after month of such driving my clutch would be gone :D

On lupo gear ratios ar something similar.

I know that best BFSC is at max torque for TDI, But I have seen that my MPG drops when I try to shift at higher RPM (2200-2500)

My car is far enough from stock. Stock lupo 1.4 TDI has wastgate turbo, 75HP and about 200 Nm torque.

MY car is chiptuned several times, has been upgraded to Hybrid VNT turbo from lupo 3L and now it develops 110 HP and 250 Nm, my peak torque is at 2300-3000 RPM

As some have stated, it's all about the terrain, road conditions, traffic, etc. I've been driving a 2000 Jetta TDI since March of '02. It has virtually no mods and has attained a life time average above 50 mpg. (Over 400 fill-ups, all in a rather detailed Excel Spreadsheet)

I generally shift above 1900 RPMs (peak torque) up to 3000 RPMs. But, I do a lot of shifting in the 2300 to 2500 RPM range.

The Turbo can be "exercised" for working purposes without taking the engine up to 4000 or more RPMs. If you get on it (above 2100 RPM) with a steady push on the pedal taking the RPMs up to 3000 ..........the boost will max for an instant!..... shift and do it in the next gear. That means the Turbo actuator went full range. I've practiced that method and have never had any issues with my Turbo (still original). I do take the RPMs up to 3600 to 4000 at least once per tank of fuel.

I must be doing it all wrong with my Mustang. I shift between 1500 and 2500 RPM, depending on driving conditions. Peak torque is @ 3500 RPM. I rarely see 3500 RPM on the tach.

If on the flat, I usually let the clutch out at idle without the throttle, shifting so that I have the car in top at 30 mph. I don't skip gears but let each ratio do their job, to let the engine work efficiency. My car is an IDI with only 68 hp, doesn't have a tach YMMV.

You do not have t o accelerate rpm up to 4000 to "exercise" turbo actuator. it makes full movement already up to 1900 rpm, when ecu is "asking" full boost from turbo. when you rev up engine higher, the actuator acualy decreases turbo pressure. The exhaust gas flow and heat is what actualy cleans vanes of vnt turbo. when you realy want to clear a turbo vanes drive for a mile or two with rpm at about 3000-3500, then the heat an lean burning from the engine will burn up all the ash in turbo and exhaust system.

Vnt15
 

That's a new one on me!

So, the little old lady driving style (babying it) isn't what causes the VNT15 to stopping working?...........Hmmmm

Well, I've disassembled "numerous" VNT15s for cleaning. I've yet to find one with the VANES all clogged up! The ACTUATOR operates the internal levers that in turn move the VANES in the path of the Exhaust blast coming out of the manifold. Soot gets blown back into the "internal" working parts of the VNT15 away from the exhaust gas blast. That soot, along with moisture, during slow warmup will eventually restrict the movement of those parts. I've seen VNT15s that the ACTUATOR would not move but the VANES were perfectly clean! After disassembly, cleaning and re-assemble, the ACTUATOR had full movement with no restriction at all!

There's a "ton" of info about the VNT turbos on the net and specifically at the TDIclub.

The ACTUATOR operates per the N75 valve which is re-acting to ECU demand. As demand for more power (during acceleration) the angle of the VANES is changed by demand of the ECU to direct the exhaust gas on to/across the blades of the Turbine for additional boost. I run a ScanGauge and have never seen maximum boost at 1900 RPM, quite the contrary!

I repectfully disagree with your assesment of the operation of a VNT15! Reading and hands-on are quite different.

Nah, just driving different engine technology.
You're using those cubic inches as they pump out more than enough power, and keep the rpm low.

With petrol engines you can't shift at peak torque for economy because it's usually far too high up in the rev range - but that's changing on downsized, turbocharged petrol engines like the newish Beemer 20i, 25i and 28i.They have their max torque from way down on the charts.

I have rebuilt turbo on my car myself.

when I start my car turbo actuator right away pulls vanes into position to max boost. for my car it is 20% PWM signal for n75 valve. While driving when turbo spools up and boost rises, the actuator moves back an turn vanes to reduce boost up to 99% PWM signal for n75.

The only car i have seen which at idle is not pulling actuator for max boost is lupo 3L.

A lot of times I have seen that cloging of VNT vanes is due to bad (cloged) catalytic converter.

Shifting will be engine, drivetrain, terrain dependant. Anyone who says not to shift the 7.3 PSD at peak torque, when under load, doesn't understand diesels. IH and Ford recommend a shift range w/ the 7.3 and the 6spd to occur between 1800-2000 rpms, right where the peak torque is. It doesn't kill the 7.3 and it for sure wont kill the turbo:confused:.

I had an 02 7.3 PSD and I short shifted that 8k truck all the time unless I was loaded. 18 mpg for a 8k brick wasn't bad but I did well due to shifting around 1500, just under the peak torque.

OVERSPEEDING a turbo is what kills them, besides lack of oil. A stock 7.3 turbo will live forever under factory injectors and factory tuning going 250-300k miles as a pulling/hauling vehicle. However, a simple "chip" add on creates extra boost that, over time kills the turbo due to repeated over speeding, and even for the aftermarket GTP38R Garrett Ball bearing unit, they recommend not to exceed 40lbs of boost.
I know that aftermarket HO Precision and Bullesye turbos die from being oversped.

FWIW, having owned two large vehicles there is a variable that people some times forget and the 14mpg semi on this forum should be a reminder to all:

1) Keep rpms as low as possible w/o lugging the engine. It takes fuel to make revs. He's running 1200rpms @ 55. A member on another forum I frequent is getting 24mpg hand calc in his 8800lb F350, dynoed at 700Hp. He got the hwy #'s by using 3.31 vs the factory 3.73, keeping rpms low.

2) Aerodynamics. Factory cars will never get super duper mileage from the factory for now since the public as a whole doesn't want bullet cars. This also falls back w/ RPMS, it takes more fuel to push your barn door or even your small door through the air, the faster you go the more fuel that is burned.

3) Parasitic loss, poorly lubricated drivetrain components, sticking brakes, etc.. I noticed a 2 mpg drop recently and i had a caliper sticking. Fixed it and things are normal again.

I come here to pick up some ideas and its interesting to see the innovation that is made.
I truely miss the 50mpg, in stock form, mid 1980's honda civic. People get exicted about a 30 Honda accord, oh how we've forgotten what was not only possible but what was.

Really, if you are a mechanic and have experience w/ cars and diesels. You should feel comfortable and know to take advantage of the torque the TDI provides. Shift just above the lugging point so you're not having to go beyond what your current throttle position is and still provide enough power to continue at your desired rate of accelleration. I'd say there is no magic # as I mentioned before there are plenty of variables to discredit a set RPM #.

Complitely agree to your points. I love to have a car that is esaly capable of 66 MPG :D

As I see in this forum, it seems there are a lot of Americans, who has not have so much experience with TDI engines. In my opinion if some one says you must to keep your RPM at 2500 -3000 to get good MPG, then he does not know nothing about diesel engines (more over about TDI).

Anyone, American, Brit or whatnot, who claims that is a good rpm range is a fool but whatada do? :D The TDI is a neat little engine and I'd love to pick one. My buddy has a NA diesel in his 80 something rabbit truck and gets 45mpg. I'm trying to talk him into a small turbo to help w/ his low end torque but he's hesitant. Banks, which is over priced/over hyped, has a kit for the NA 6.2 and 6.5 chevy diesels and they see improvements in both daily mpg and a small HP jump.

Good luck w/ the 70 mpg goal :thumbup:. My 1st goal is a repeatable 20 mpg w/ my 600hp setup. If I can regear and start working on some aerodynamic improvements I hope i can get maybe 23-24 repeateable at hwy speeds. I have a lot of hurtles but it will be interesting to try.

With my ko3 turbo when at 1000 rpm and i give it half throttle my boost goes from 0 to 20lbs for a spike then settles at 15 lbs until i release the gas pedal.
At 1900rpm my car is making full torque, I need about 1/4 of the torque to accelerate, attempting to use the whole torque is non sensible unless you are in a race or are trying to tow a house.

Anybody with a boost gauge and vnt turbo should be aware of boost levels.

~ A health monitor for the turbo ~

A boost gauge may be the best thing you could do for your turbo, You can see over boosts and no boost problems and anything in between.

I'm new to the eco thing but gauges are smart for any turbo'd vehicle.
I'm always eyeing mine, trying to keep EGT's as low as possible in the highest gear. At a bare minimum a boost and egt. One thing some turbo guys forget is EBP. The more EBP you have 1) You stress components more 2) That is increased rotational resistance. The factory 6.4 Twin turbo is 1:1 WOT and is about 10-20% higher at cruise. W/ a non-VNT/VGT/VVT (brand dependant) a waste gate and proper A/R housing is important as well but often over looked by rookies, sometimes resulting in an over-sped/blown up turbo.


Theres a fella on PSN who's building a mazda diesel and IIRC he's set up to have about 15lbs boost max and the rest is waste gated and hes getting 32-35 in his mini 4x4 at the moment. Someone else has a 500-600 dyno hp 5.9 in a 1/2 ton dodge w/ the 6spd who, @ 55 on flat ground has acheived 50mpg. He's supposedly had difficulty repeating it but claims high 30's/low 40's when driven properly. He matched components carefully and runs 308 gears and the 6spd trans and the whole thing is lowered. Rant, my bad but point is he trys to drive just above idle 12-1300.

I got to try a TDI.

As I stated previously, my 2000 Jetta with the ALH TDI engine has given me just under 51 mpg overall average since I have owned it (March 2002). It now has almost 308k miles on it. The vast majority of my driving has been the norm............doing nothing special to attain the results.

As I think I also stated, I'm in the process of installing an '02 ALH TDI engine in an '84 VW Vanagon. I'm trying to finish the project in time to head north to Alaska.... August 6th being the date of my window closing. I plan to maintain records on the performance as well as a Thread on the trip.

It will be interesting to "learn" the best shift points for the TDI/Vanagon set-up. I did rebuild the transmission, including the installation of taller 3rd and 4th gears. On paper, at 65 mph with 205/75/14 tires, the .77 ratio 4th gear and the 4.57 R&P, the RPMs should be about 2850. That is about 700 RPMs lower than the stock gearing but, about 550 RPMs higher at that same speed in the Jetta! So, I'm hoping that 30 to 32 MPG will be attainable!

The project is in the TDIclub.com, TDI Conversions.

Varn the tdi's are nice to drive, i can literally barely feel my jet ski behind when towing,including accelerating from a stop. My previous vehicle a 3L v6 Ford Ranger Struggled towing the same set up, Nutz.
Too bad they don't make a pick-up.
Powerlifter, Good points you made.
Wow, twin Turbo's on the F350, That is pretty damn sweet.
I dream of adding a second k03 to my beetle..
I notice people throwing big turbo's on their cars without much concern for spool up times,seems like most are interested in max hp gain.
Andy i bet if you shifted at 1500rpm you would see even a higher mpg. Just shift quicker, I rarely skip gears, if on a decline i will.

K03 is a wastgate turbo and it makes a boost spike, with VNT this spike is much lover, because actuator can regulate boost much more precisely.

My boost spike is 20-22 lbs it last for 1-1.5 seconds,
and only when i punch the gas.
What is the boost spike on the vnt turbo?
I personally am happy i have the waste gated turbo on my car, it spools up instantly can be be adjusted via different waste gates and has none of the issues associated with the VNT turbos.
The Audi TT uses a waste gated ko4 turbo.
I am curious if the VNT turbo has a boost spike as well.
I seem to remember reading that it does spike.. but its not my turbo so i never really looked that hard into it.

Based on a ScanGauge, my VNT15 (no mods), will max out at Manifold Absolute Pressure (MAP) slightly above 32 psi. Generally, at idle, the MAP is about 14.2 psi in my neck of the woods (about 1000 foot elevation). Doing the math, that would be 17.8 psi maximum boost.

I see that boost response while taking the RPMs up steadily but agressively in 1st and 2nd gears........ it's not exactly instant and begins to drop back well below the MAP of 32 psi at about 3200 RPM, give or take, depending on the terrian.

Yes, below 2100 RPM, there is a definite lag in boost. But, the "advice" is to never do a WOT below 2100 RPM. In fact, I've never done a "sudden" WOT with my car since I've owned it. When I do WOT, it's always on a gradual basis being a little more aggressive toward the end.

Must be the fins slowly opening up to catch exhaust that takes the time for boost to build on the VNT.
With mine the waste gate opens up and it gets full flow.
I rarely give my car full boost mostly on steep hills on fast roads, then the car is using full torque and boost.

And wow the VNT15 has a fairly high boost spike. That should keep things moving freely you would think.
I wonder if its the EGR that's leaking oil and crude to the turbo that is causing the sticking vanes/ mechanism.

When I learn how to post pics, I'll stick some up of several VNTs that I have worked on.

Typically, the problem is not with the VANES (actually, I've never seen a problem with the Vanes). Directional Vanes, since they change the angle of exhaust gas hitting the Turbine blades of the Turbo. The issue is that exhaust gasses pass around the 9 levers and get inside the rotating ring that operates the Vanes........ you will see this in the pics. The crud builds up and eventually causes it to become "sticky."

You can go to TDIclub.com and search my Albums for the VNT 15 photos. I think this link will get you to the VNT 15 photo album.... TDI VNT 15 - TDIClub Gallery