TDI low end power increase

has anyone done a write up on how to get the most low end torque ie 1000-2000RPM from the TDI .. i am working with a MTDI but i am kinda curious what kinds of things are done to get the torque up.. i am more looking for torque then HP.. as HP dose nothing for what i am doing..

First, you really do want HP, just that you want it in the 1000-2000 RPM range and not in the 3000-5000 RPM range. Torque does no actual work.

Low RPM power is limited by peak cylinder pressures (rods, rod bearings, oil pressure, head gaskets, pistons, etc) and your smoke tolerance.

There's also two different approaches to low end torque - how much you have and how fast you can get it. For normal everyday driving, how fast you can get it is more important than how much you have. If you're towing a trailer or something where transient response is not as important, then quantity is more important than speed.

With a MTDI, you're really hamstrung by not having ECU control over the injection timing. I've found this to be one of the more significant factors in both response and quantity of low RPM power - particularly before the turbo gets spooled up.

Hard parts are next - cam, pistons, turbo, rods, heads, etc

Keep the highest compression ratio that you can and use pistons with oil cooling channels and reinforced/lowered top ring lands.

Keep the OEM cam or go custom - none of the standard aftermarket TDI offerings will improve torque in the 1000-2000 RPM range

Go with aftermarket I beam rods and the best rod bearings

Go with ARP head studs

A girdle for the block and a smaller oil pump gear is also a good idea if you're aiming for over 300 ft-lbf and will use it for sustained periods of time

Go with big injectors - R520's at a minimum

Turbo selection is varied depending on how much you want to spend/how much you want to fabricate. Again, not having ECU control of a VNT turbo will really be a limiting factor here as well. I'd recommend a VNT15 on the cheap side of things, any any of the smaller GTC/GTD offerings on the market in the last couple years in the 14-15 series range. They'll support 150+ HP and still have very good transient response and spool up at 1500 RPM or below when properly tuned. If you want to stay wastegage I don't have a lot of suggestions - probably some good turbos out there, but with much more compromise compared to a VNT setup.

OP Read this for a greater understanding of HP and torque.
http://www.nrhsperformance.com/tech_power.shtml

I'm going to assume that you don't want to completely rebuild your engine based on the fact you already have an MTDI. I'd say first off you want to ditch the VNT 15 turbo, simply because it doesn't hold up to high pressure ratios-as in max safe boost will be around 18psi. There is more or less a linear relationship between how much boost you have and how much torque the engine will produce. Just playing around with the http://www.not2fast.com/turbo/glossary/turbo_calc.shtml#af guide, you should be able to hit 300ft/lbs with 30psi of boost. This assumes an 85% volumetric efficiency, 30psi boost, 18.5 AFR and .35 specific fuel consumption. The Holset turbos easily withstand this kind of boost, but all the ones I'm aware of are too large to spool for this application. The trick is to find the right turbo that will safely hit the boost numbers while still being small enough. The easiest solution is to get a turbo with a wastegate so everything is mechanical. You will need to replace the factory head bolts with studs or 12.9 hardware store bolts. You should be able to nearly double your torque over factory with just studs, a new turbo and intercooler, injectors, and possibly a 11mm pump plunger.

i am not so much after 300lbs of torque, im more after hitting 220lbs much sooner and just holding onto it for much longer like i would like to hit say 180lbs of torque around 1500 RPM and just move upto 230 by 1800-1900 RPM and hold that to like 2200 RPM

basicly what i am working with as far as parts go is a stock 1997 1Z engine with a T15 Turbo and a LR300 TDI pump and .216 injectors..

my RPM range for driving will stick from 1000-2000 RPM but once i take off and get out of 2nd gear ie after 20 MPH i am rolling at above 1350 RPM every shift after i am not after a huge deal of acceration just enough for everyday driving and a little extra power if i ever needed it..

what i am trying to figure out is can i get my power goals with the T15 turbo or would going with something like a T25 or K04 get my LOW RPM goals but also my Higer RPM goals as well as i kinda understand that the T15 might get me my boost presure but might now flow enough out the turbine section and end up costing me Power.. but what i dont know is if a T25 or K04 would spool up as fast as the T15 thus costing me power where i might need it for the first few shifts

Ah, that makes sense what you are trying to do. Your first step is to make sure the pump will deliver the fuel in sufficient quantities at the low rpms. I can't remember off the top of the head how to change the torque rise on those pumps; its a lot easier to change the torque curve by updating a numerical table when the engine is drive by wire. I think I have the same or similar pump on my 4bt cummins. I'm sure a lot more of the cummins guys have modded their pumps for more power in the range you are looking at, so you might look and see what they are doing.

benhart16 said:

Ah, that makes sense what you are trying to do. Your first step is to make sure the pump will deliver the fuel in sufficient quantities at the low rpms. I can't remember off the top of the head how to change the torque rise on those pumps; its a lot easier to change the torque curve by updating a numerical table when the engine is drive by wire. I think I have the same or similar pump on my 4bt cummins. I'm sure a lot more of the cummins guys have modded their pumps for more power in the range you are looking at, so you might look and see what they are doing.

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i think it can the 300TDI's are 100-110 HP engines that make 188-210lbs of torque stock

Oh, I'm sure it can produce the fuel. . .it's just a matter of the governor springs and such letting the pump do it at that rpm.

benhart16 said:

Oh, I'm sure it can produce the fuel. . .it's just a matter of the governor springs and such letting the pump do it at that rpm.

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yeah i told my pump builder what i am wanting it to do. and from i gather he knows what he is doing.

I'd go for a smallish vnt turbo for what you want.

turbobrick240 said:

I'd go for a smallish vnt turbo for what you want.

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are there some VNT's that can be Vac controled like the waist gate ones?

ryanjames170 - below is the dyno plot from my engine - signature copy for reference, but I don't have half of the things I recommended

03 Jetta, Cat 2u, DG Steel SP w/MOGolf Mod, 3"DP, 4"EXH, EaBP110 Bypass, Euroswitch, ECodes, Driving Light, PD Lift Pump, R520's, RC5,RC6, TDTuning, Malone, ScanGaugeII, 3" TIP, 2" TOP, GTC1444VZ, 3 Bar MAP, VR6 MAF, Vented Fender Liner, Battery Cover Mod, 11mm, Monster Mats, 215/55/17 (27.9/53.0/75) Monthly MPG Links, Euro Trunk Latch, IDParts RSB, SDI or ALH Intake, ARL Ceramic Pistons, Rosten Rods, DRW, Wavetrac, SBC, FSD's, Beef Springs, Rebuilt Head, Recaro's, Colt II, DG Sigma 6, RMT200

I'd be surprised if you can duplicate this, or even close, without an ECU. If you do, there will be significant compromises made to achieve it. I've been through 3 different turbos, 3 sets of injectors, 6 tunes from 3 different tuners, two different injection pumps, 2 different cams at various degrees of advance/retard, etc and without a doubt, the modification with the most significant impact on everything you're looking for is the ECU/tune.



Not trying to rain on your parade here, but I think you're in for an uphill battle. The injection pump/nozzles and turbo are really the only variables that you have to play with, and if it's not what you want, they're difficult/expensive to change.

I guess my question is why do you want to keep the RPMs so low when its going into a Dodge ram 1500? You will make it practically undriveable if you limit it to those RPMs unless you regear the axles to some really long gear but then your reducing the torque reaching the tires.

Dirtracr95 said:

I guess my question is why do you want to keep the RPMs so low when its going into a Dodge ram 1500? You will make it practically undriveable if you limit it to those RPMs unless you regear the axles to some really long gear but then your reducing the torque reaching the tires.

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i am trying to stay away from having to regear anything.. basicly if i leave the truck as is with the gearing i can cruse the truck at 2000 RPM at 55 MPH which puts me right in the sweet spot of the TDI's torque curve.. i am only realy worried about the below 1500 RPM for the first 3 gears i shift as and for intial pull of in 1st gear and i kinda thing that is not a whole lot of torque realy being used as evan with the V6 i am not using much of the gas peddle to get it moving

1st gear i go to 2000 RPM at 12 MPH
2nd gear i go to 2000 RPM at 20 MPH
3rd i go to 2000 RPM at 32 MPH
4th gear i go to 2000 RPM at 45 MPH
5th i hit 2000 at 55 MPH
6th i hit 2000 RPM at 70 MPH

of those speeds i hit the sweet spot for my average driving spot 4 times

1st at 25-30 MPH in 3rd
2nd in 4th going 40-45 MPH
3rd in 5th going 55 MPH
4th at 70 MPH my freeway crusing speed

Have you ever driven a manual transmission before?

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I've got a 76 C10 chevy with a 120hp/320ft-lbs 4BT cummins and a turbo 400 automatic transmission with 2.73 gears. I'm turning just over 2000rpms at 60mph. Even with this torque monster, the thing won't fall out of a tree dead unless the engine is revved to at least 1800 rpm. It really starts pulling strong around 2200rpm up to the governor at 2500rpm. Considering you have a gasser truck, you probably have a 3.73 rear end, so you'll be turning right around 2500rpm at 60mph. This is actually a little faster than my Jetta, and if anything above the factory torque curve. You really need to focus on power from 2000-3200rpm for this thing to get out of it's own way.

79jasper said:

Have you ever driven a manual transmission before?

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yerp my DD is a 6 speed haha this truck is my DD

benhart16 said:

I've got a 76 C10 chevy with a 120hp/320ft-lbs 4BT cummins and a turbo 400 automatic transmission with 2.73 gears. I'm turning just over 2000rpms at 60mph. Even with this torque monster, the thing won't fall out of a tree dead unless the engine is revved to at least 1800 rpm. It really starts pulling strong around 2200rpm up to the governor at 2500rpm. Considering you have a gasser truck, you probably have a 3.73 rear end, so you'll be turning right around 2500rpm at 60mph. This is actually a little faster than my Jetta, and if anything above the factory torque curve. You really need to focus on power from 2000-3200rpm for this thing to get out of it's own way.

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it will turn almost 2200 at 60 MPH.. i got 3.21 gears in the rear.. just more gearing in the trans i think

Torque shouldn't be an issue. With a heavy vehicle like that, I'd be looking more at making power. If the rig will be used on the road you'll want well over 100 hp.

You definitely want more than 100hp. If you poke around the 4BT forum, you will see the 3200 rpm governor spring (from 2500rpm) is a popular upgrade. I'd be reading up on both the 4bt swap info (similiar power and vehicles), and the vanagon tdi swaps.

Then don't be afraid to rev it higher.

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ryanjames170 said:

i am trying to stay away from having to regear anything.. basicly if i leave the truck as is with the gearing i can cruse the truck at 2000 RPM at 55 MPH which puts me right in the sweet spot of the TDI's torque curve.. i am only realy worried about the below 1500 RPM for the first 3 gears i shift as and for intial pull of in 1st gear and i kinda thing that is not a whole lot of torque realy being used as evan with the V6 i am not using much of the gas peddle to get it moving

1st gear i go to 2000 RPM at 12 MPH
2nd gear i go to 2000 RPM at 20 MPH
3rd i go to 2000 RPM at 32 MPH
4th gear i go to 2000 RPM at 45 MPH
5th i hit 2000 at 55 MPH
6th i hit 2000 RPM at 70 MPH

of those speeds i hit the sweet spot for my average driving spot 4 times
1st at 25-30 MPH in 3rd
2nd in 4th going 40-45 MPH
3rd in 5th going 55 MPH
4th at 70 MPH my freeway crusing speed

Click to expand...

In my opinion, if you're willing to move your shift points up by 250-300 RPM, you'll make your (M-TDI) life so much easier. Your torque peak will be ~2000 RPM and fall off quickly below 1800 RPM. If you're shifting at 2000 RPM as you indicate above, you'll be at 1400-1500 RPM when you get into the next gear and be on the wrong side of the torque curve.

If you target your upshift points to be 1800 RPM or greater when you get into the next gear, you'll have adequate power to accelerate rather than having to fight your way up the torque rise curve. The stock turbo will likely work fine for you and hopefully your injection pump rebuild will deliver the fuel/timing in the lower RPM's where it'll have adequate response and not a big smoke show.

Fix_Until_Broke said:

In my opinion, if you're willing to move your shift points up by 250-300 RPM, you'll make your (M-TDI) life so much easier. Your torque peak will be ~2000 RPM and fall off quickly below 1800 RPM. If you're shifting at 2000 RPM as you indicate above, you'll be at 1400-1500 RPM when you get into the next gear and be on the wrong side of the torque curve.
If you target your upshift points to be 1800 RPM or greater when you get into the next gear, you'll have adequate power to accelerate rather than having to fight your way up the torque rise curve. The stock turbo will likely work fine for you and hopefully your injection pump rebuild will deliver the fuel/timing in the lower RPM's where it'll have adequate response and not a big smoke show.

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i have no issue with pushing my shift points up as past 3rd gear its not a huge issue but yeah i don think pushing it upto 2250vs 1900-2000 would be much of a issue i was just more worried about the first 3 gears that are low in the RPM band but perhaps once i get it into the truck i can actualy see what is happning.. the more i think about it i am sort of have this feeling that evan a stock unmodded 1z/AHU would still push the truck down the highway with my gears i just might not have alot of reserve power.. my truck only has 210lbs of torque at 2000 and a stock AHU/1z has 145lbs at 1900 RPM.. what i would see i dont see dodge using all 210lbs of torque to move a truck that only weights 4460lbs at the curb and the TDI should cut about 200lbs off that weight..
what i know is that the truck has a total weight moving capacity of 8000lbs but they kinda derate the truck with the manual "warentee issues"

perhaps i will be fine with a few minor power adjustments

The first 3 gears are also the easiest from a power standpoint because your aero load is very low compared to the top 3 gears.

With a stock 1Z/AHUYou won't have a speed demon on your hands, however it should be able to accelerate responsibly in town. Out on the highway, trying to pass on a two lane road will likely take some planning though given the significantly higher aero load at any given speed compared to a Jetta/Passat.

if that LR300 pump is a 12mm head, he keeps the .216 nozzles and he swaps the gt15 for a 2052 or a he200wg to flow enough air... ahhh the dreams i have...

i think then it will be adequately powered for a 4000lb truck. i want the same basic setup but in a smaller ~3000lbs truck. ill wager you can tweak and get it to have similar HP levels as the straight 6 (300CI) that was in F150's for eons but with more torque.

i'll grant that the 300CI is no speed demon though... lol

ketchupshirt88 said:

if that LR300 pump is a 12mm head, he keeps the .216 nozzles and he swaps the gt15 for a 2052 or a he200wg to flow enough air... ahhh the dreams i have...

i think then it will be adequately powered for a 4000lb truck. i want the same basic setup but in a smaller ~3000lbs truck. ill wager you can tweak and get it to have similar HP levels as the straight 6 (300CI) that was in F150's for eons but with more torque.

i'll grant that the 300CI is no speed demon though... lol

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dont need to realy go any faster then 75 lol..

i am not sure what the 300TDI pump is got for a head on it but it comes from a 2.5L 4 banger

i am looking into a turbo but i dont know nothing about them to honesly know what to look for.. i would like one that bolts right upto that triangle flange though..

options pretty limited on that 3 bolt flange i think. maybe someone has an idea that bolts to it though.

a different manifold would be straight forward to bolt different turbo on while swapping.

http://www.eurotrashmotorsports.com/?product_cat=manifolds

probably can be found for less $$$, i didnt search too hard.