PeachParts Mercedes-Benz Forum - 617 Torque improvements, no interest in HP

PeachParts Mercedes-Benz Forum (http://www.peachparts.com/shopforum/)

- Diesel Performance Tuning (http://www.peachparts.com/shopforum/diesel-performance-tuning/)

- - 617 Torque improvements, no interest in HP (http://www.peachparts.com/shopforum/diesel-performance-tuning/251665-617-torque-improvements-no-interest-hp.html)

Its not a matter of what should be done first. Gaskets for adjusting the pump are under $5 and the IP takes 1/2 an afternoon to remove the rack limiter and about an hour or two to adjust the torque capsule. It can be done at any time, its not "one or the other".

Quote:

Originally Posted by ForcedInduction (Post 2190710)

Spoken as somebody who truly has never had the pleasurable experience of driving a VNT equipped car. :rolleyes:

A VNT is a far more noticeable change in performance than 20hp from the rack limiter. The rack adjustment and torque capsule will have no significant effect on low end torque since power is limited by the same air availability and the stock turbo's poor response time.

The graph curves tell all. The only difference between the two graphs is time and a GT2256V instead of a K26. There is no difference in fueling, only air.
http://www.peachparts.com//shopforum...chmentid=63130

Which curves would you rather have? ;)

JDmills wants low end torque over anything else so clearly a VNT should be priority, if not a supercharger.
The GTA2056V from a Jeep Liberty or M90 supercharger from a Buick or Ford would be about ideal for his needs.

EDIT: Here is the video I was talking about earlier. Right is exhaust pressure, left is boost. http://www.youtube.com/watch?v=eM7SNOc3nMY Its interesting to watch the exhaust gauge, you can see how the vanes open and close to control boost through exhaust velocity (exhaust pressure). Try doing that with your T3! :D

Forced,

This graph shows output at the rear wheels, correct? If that is so, then a VNT would be just about all I am asking for. as your car has got to be close to 250 at the flywheel..

Is this after a bunch of fueling modifications? I am guessing that it must be?

...amazing how the low end is totally tranformed by a modern turbo.. I cannot imagine what a difference it makes when driving the car... but it has got to make a HUGE difference...

FI, how can torque with VNT (~195) be that much higher over the stock one (~137)? You're only supplying air earlier. Also the VNT HP is about 10hp higher over the stock one. Air alone can't do that.

The HP graph looks nice and smooth :D. Over 100 hp starting from 2900 rpm if I'm not wrong :cool:.

Quote:

Originally Posted by JDmills (Post 2190836)

Is this after a bunch of fueling modifications?

No, just the turbo change. Fueling is as stock for both runs (except the ALDA which was adjusted a long time ago).

Quote:

Originally Posted by Deni (Post 2191048)

FI, how can torque with VNT (~195) be that much higher over the stock one (~137)?

Starting with 7psi of boost @ 2000rpm instead of 1psi. The engine has 30% more air available at the same RPM and boost builds much more rapidly from there. Notice the boost curves are opposite in profile, the K26 is concave while the VNT is convex.

Quote:

You're only supplying air earlier. Also the VNT HP is about 10hp higher over the stock one. Air alone can't do that.

You're somewhat right, but flowing that air more efficiently does. The compressor wheel is much more efficient at compressing air (72% for the T3 vs 80% for the 2256 at the same flow and pressure ratio), all the exhaust is flowing through the turbine instead of most being wasted bypassing it and the rotating mass is much lighter. All of that means less exhaust manifold backpressure, horsepower, is needed to drive the turbo.

Do they compensate for the differential in those dyno runs? (giving flywheel torque) Otherwise you would expect 3x the torque at the wheels in 4th gear.

I don't know. You'll have to contact Superflow.

The IP will limit fuel based on RPM, pedal position, and boost pressure. FI has increased boost pressure and therefore the IP should be allowing more fuel (thus more power).

For more power, get a 603. You're already 195lb-ft @ 2400rpm stock, and with close to 150hp and a higher RPM range, you can hold low gear longer for pulling or climbing.

If the 617 is free or already installed I understand.

Quote:

Originally Posted by Deni (Post 2191048)

Quote:

Originally Posted by ForcedInduction (Post 2190550)

Not at all. Its one of the first things that should be done in the search for performance, after getting the engine in proper tune. The difference between the T3/K26 and a VNT is night and day. 200lb/ft torque below 2000rpm is normal with an otherwise stock engine. Thats at the wheels with a manual transmission, instead of the stock 180lb/ft @ 2800rpm at the engine. An automatic will have even more torque on the low end thanks to the torque converter's multiplication.

Any weekend shadetree mechanic can do it. The flange for the Liberty turbo can be bought for a reasonable price, oil lines are cake to make if you know where to find a hydraulic shop for fittings and the stock exhaust can be used. The hardest part is making a decent air filter system (thats not just an open filter on a tube).

An intercooler will have no effect on torque, just top-end power.

I C

Quote:

Originally Posted by babymog (Post 2192068)

The IP will limit fuel based on RPM, pedal position, and boost pressure. FI has increased boost pressure and therefore the IP should be allowing more fuel (thus more power).

But there's only so much fuel that the IP can provide, so only by increasing boost it doesn't necessarily mean you'll have more power (unless you're not burning all the fuel that is injected).

I didn't increase boost, I made it build boost much sooner.

Quote:

Originally Posted by ForcedInduction (Post 2190637)

Check out my youtube videos. One shows me revving the engine without a load. Its an older video so it was only set for 11psi at the time, I have it set for 14psi right now.

(I'd link but the shop computer blocks youtube)

OK on the youtube block. Well, I've never seen any any formidable boost unloaded. Unless you have done something in the mods to make exhaust boost go up. Or run on a dyno?

A VNT turbo is all thats needed. I use the stock exhaust system. http://www.youtube.com/watch?v=eM7SNOc3nMY