TDI, better MPG from hard acceleration?
 

I read this concept on a TDI forum, and decided to try it out. It was stated on that forum, that it is better for a TDI to accelerate hard to the given speed, than it is to take time to get to it. This statement is completely backwards from what most people do, what i do, and what this site recommends. But i tried it anyway and here is what I have seen.

The last few nights on my drive home from work, I have a stretch a the edge of town where I must stop at a stop sign. After that, it is around 1/2 to 3/4 mile to the stop light, speed limit 35. Most days, i take it easy when leaving the sign, and by the time i get to the light, my torque app is at the same trip MPG as it was when I left.

Tonight when I left the stop sign, the trip MPG was at 47.6. I took off hard, about 75% throttle, and when i got up to speed for OD to kick in (41MPH) i let off and drove 38 mph the rest of the road. When i got to the light my trip gauge said 47.9.

I thought is that it can be more beneficial to do this in my car (02 tdi auto) is i have at least a 1/2 mile for sure before i need to slow down.

I would really like to hear what everyone thinks on this matter.

Your using a Auto transmission so it puts a whole new spin on it, But sounds like its a very good Auto trans. To Hit OD at 41mph is Really good for a Auto , with my Standard Trans I go into 5th at 30mph and accelerate to Speed if need be from there.


So I Push the throttle lightly but shift swiftly keeping the engine under constant load, no Lalley gagging about (Im always under 1,900rpms because of rapid gear shifts) but not 1/2 throttle , for me it takes only about 1/2" of throttle to Propel myself Faster then the rest of the cars leaving an intersection.


So I think its wise to be zippy and coast often

I have a 1999 F150 with the 4 speed automatic. In the first three gears, mileage increases but at 40 MPH it will go into 4th gear or overdrive and then the scan gauge really begins to give the higher numbers. I too have decided that the sooner I can reach the magic 40 MPH barrier, the sooner higher mileage kicks in.

ecomodded, I too was surprised when I found out it was going into OD and not 4th. I have only had this car a few weeks, so it is still taking some time to get use to it. Also this is my first diesel I can run torque with, so I can start to understand what works best.

Goldenstate, Do you watch the load or throttle when you take off? If so, have you found what works best for you (ie mid throttle/load or high)?

Rango318: For years I have followed the common wisdom to drive like one has an egg under the foot. With the egg method, I found I was staying in the lower MPG areas of the Scangauge during acceleration. When I decided to kick things up and no longer use the egg method, I arrived at 4th gear sooner and my overall mileage average picked up a bit. I would estimate a mild to moderate increase in acceleration but still not a hard acceleration.

I have only had the Scanguage a few months and decided it was time to begin trying new things instead of more of the same. With an automatic one is limited to what they can do. I gave the increased acceleration a try and was pleased with the results. I first noticed the improvement when on my regular downhill run from a stoplight. I got to the higher numbers faster when going down hill and decided it might work on the flat land part of my drive as well.

Goldenstate, That's what I thought was happening as well, just staying in the low mpg to long. Where I live is almost completely flat so it should help when I go test this out. I think I might go out today before work and drive around the mile a few times, do some A-B-A-B testing and see what it comes up with.

I started with full throttle acceleration (having found this works great on my petrol cars). I then tried 80% load (which is often very little throttle) and got the exact same results. I shift at 1500-2000 depending on traffic etc.

I don't trust SG or any ODB tool for instant consumption for diesels. The calibration fluctuates wildly if you change techinique.

oldtamiyaphile, I'll keep that in consideration. I figure even if it isn't the most accurate, I still have something to look at and keep me motivated to get better numbers.

I accelerate at 90% engine load in the civic, then shift to neutral and coast. The chevy is automatic and doesn't have a gauge, but I do the same thing. For example, there are two stretches of a 1/2 mile between stop signs that I drive often in the chevy. I accelerate the first part, then shift to neutral and coast the rest of the way. If there is traffic ahead, then I just accelerate enough to get closer, then coast and repeat. This works well in the civic, so I figure the results are similar in the chevy, as it is a very good coaster.

I too use to drive like a little old lady, then discovered you can really beat on a car and still get decent fuel economy if not better in some cases. :thumbup:

Cobb, I still drive like an old man to a point, I take off hard, but still only do about 49 in a 55. I found that my OBD reader shows 40-45mpg at 55, but shows 50-55mpg at 48.

I just filled up my 4th tank on my TDi, my first tanks were my usual foot to the floor approach, which netted me 9l/100km.

On the third tank I went with the 80% load method (which is really slow in my case), SGII promised 8.4l/100km, but the fill up was a disapointing 9. My best to worst tank so far have only been 0.2 apart.

If I can't evaluate different driving styles with it, SG and others are of limited use as a diesel saving device IMO.

It seems you are also getting the turbo spoiled up higher which helps mpg.
It is critical that if you eco drive a diesel that it gets a good hard "Italian tune up" regularly to keep the VNT from freezing up.

JasonG, I have never heard of an Italian tune up, so i had to look it up. Took me straight to TDIforum. That seems to be about how I drive now so I'll just keep doing it. I know my Torque app isn't correct, but I like seeing 53mpg on my 26 mile drive home from work.

I try to use the same briskly method of acceleration, since I have discovered this website, but I cannot understand how can be done this under the 2000 rpm. If I have to use around 80% throttle method, then I will reach around 2800 rpm, before I will change the gear, because I cannot accelerate briskly starting form low rpm! So how do I have to do?

Mcbota, when I accelerate, I don't keep it under 2000 rpms when I am driving this way. My car usually shifts around 3.5k-3.8k under hard take off. If I am taking off slowly, the way I use to, it would shift around d 2k.

I was thinking that even if I have to do briskly/hard acceleration, some are saying to not go above 200rpm, and I didnt understand how is this possible!)))

My car makes full torque at 1900rpm so 80% load is somewhere under that.

I have a fuel pump tuning box hooked up between my fuel pump and ECU that gives my car snappy acceleration , making the 1st 1/2" of throttle powerful & energetic on my tdi.


Shift fast , stay in each gear for 2 seconds or so.

I have made also a chiptuning to my car, an economical one, but I am afraid to accelerate briskly under 1800 rpm, to not provoke some lugging!

That is the same for me. The EX has higher rpms than other models of civic.

I just watch the % engine load, speed, instant and trip mpg.

I decided to start checking out the load on the engine today. Even at 50% throttle, I hit 80% load. I'm not to worried about it. I plan on putting larger injectors and a tune sometime this year.

higher rpms = higher mpg
 

By the way, as the rpms increase in the EX in 5th gear at a certain % engine load, the instant mpg likewise keeps increasing, meaning the mpg is higher at a higher rpm. I think the reason is because the EX is most efficient (BSFC?) at 5500 rpm.

You can shift from 1st to 2nd to 3rd to 4th to 5th all within 250rpm if you like, its slow but sure sometimes i do it when I am in slow mode / no rush.
But it seems more load is Better so shifting every 500rpm increase should be more beneficial.

What I mean is you take off in first till you reach 1500rpm shift to 2nd your rpm will be about 1100 then accelerate to 1500rpm,again , shift up to the next gear repeat until your in 5th gear at 1000rpm. You should be able to accelerate from 30mph using 5th gear to what ever speed you require.

I never lug my car , its takes 900rpm to lug mine, at 1000rpm I can accelerate up to speed with no lugging from any gear.

*But* this is more my style then the 80% load theory , my technique is more like 40-50% load.. I can not handle high rpm driving for low speed driving it just seems wrong to me. It might be a mental Block.. but I think high rpm is not the right direction to go for fuel economy.

I think your mixing performance and economy up and your mpg gauge is whacked !

As it does not agree with my religion ... . of the snail

:snail::snail:

But your waste gate turbo spools differently.
When the skinny pedal is pushed on an ALH the n75 valve commands the vnt to open thereby spoiling the turbo higher.

I have 455Nm at 2000 rpm so wheelspin is the bigger problem than lugging :cool:

I try to keep load at 80% below 1200 rpm, after that it's pedal to the metal. I shift at 2000-2500 rpm, keeps the turbo, egr, dpf etc clean.

My SG shows 40% load at idle (neutral), very slow indeed ;)

It takes very little throttle to max out the load gauge at the low RPM of which you speak. I typically cruise at 80% load at 40MPH/ 6th gear.

I don't want to be augmentative but I think your scan gauge is misleading you , 1dle is not 40% load

I think my ko3 Turbo spools fast and pushes good psi , on hills it maxes out at 20psi and settles at 15 psi @50mph. I can go from 0 psi to 15 -20 psi in about in a couple of seconds if I floor it.

I found this reference to the ko3 that speaks of it linear and max power and gradual..

Quote from tdi forum:
with the K03 setup its around 275 hp to the crank...... I really like the horsepower curve though as it does not peak early but gradually increases to redline......

The ko3 is the better Performing Turbo of the two given my little diesel the advantage / fast 20 psi of boost.


I should take a video of the Boost gauge going from 0-20psi , it seriously only takes about 2 seconds. Using my normal 1/2" of pedal to accelerate it maxes out at 5psi instantaneously or 1/10th of a second.

I've only ever felt this lugging in 4th gear, intown. It was down to about 1200rpm and it felt a little shaky. The tranny didn't downshift, and it only lasted 2-3 second.

I wish I had the money to upgrade my turbo. Hell, I wish I had the money to buy the $90 injector nozzles I want.

My cheap tuning box / glorified Every Mod type costs $35 on eBay , I put a link but noticed the prices are higher now.
http://www.ebay.com/itm/Tuning-Chip-...f116b7&vxp=mtr
Tuning Chip Box Volkswagen Golf IV 1 9 TDI 90 110 PS More Power Powerbox Diesel | eBay

If I turn the set screw clockwise 2.5 revolutions from its stock position the car is peppy / fast throttle response. but if I turn the set screw 1/4 more of a turn the exhausts starts smoking soot. So I keep it turned down to +2.5 turns from stock.
This little cheap tuning box works !

I may get that sometime. This weekend I'm going to order a Vagcom from newegg. Maybe if I'm lucky I'll get my new nozzles next month.

That sure beats the hell out of twisting set screws on the injector pump. :thumbup:

http://tuning.enginechiptuning.stref..._analogowy.jpg

Its convenient to use as it plugs inline with the factory connectors.
Having the set screw makes it more useful as you can tune it to your car.
Some people might leave is set smokey so they can be special(lol) and get noticed
or is it go faster , I'm not sure what the point is.

Also this cheap type of tuning box does not work well on gasoline motors ,the results would be disappointing.

Once a diesel starts to smoke, you still get performance gains, but they start to drop off fast. You need something extra like propane or NOS to go with the extra fuel to keep the power coming. :thumbup:

Well I finally broke down and bought the parts I wanted. Bought .216 injector nozzles, the in-line tuner that you suggested, a new timing belt, and a VagCom

Sounds fun :)

Sweet , I think you will see about a 50hp gain , I'm not actually sure what hp the .216 do over the stock .185 , the tuning box will work good with them.

The Propane would cheap n easy to do to , enticingly interesting for a boost.