Stay in High RPM's?

[cjtorres]

My car is semi-new, bought in 8/11 has close to 8k mi on it now. Two weeks ago I brought it into the dealer for a violent vibration at idle. (Hasn't done it since, Still worried) I took the tech for a ride to try and simulate what it was doing, was unsucessful.

THE POINT : While we were driving, he noticed that I was shifting around 2500-3000 RPM's. He said that I should be taking each gear as high as I can given the speed limit, and other variables. Wanted me to keep it above 3K, and even as much as 4500. I asked why, he said it's better for the diesel, and will save the engine in the long run. He did not get into to much detail, even after I told him I have a technical backround and he can use fancy words with me. I do R&D on small gas engines, automotive gas engines, heavy duty diesels, and alt fuel burning engines. I don't understand what he's talking about. Someone here with VW TDI knowledge can hopefully explain this to me...

Thanks,
-Chris

[Jim W]

I do not see the advantage of shifting the transmission in a high RPM range as the TECH said to do. The TDI engine makes its peak torque, 236 FT LB's @1750-2500 RPM, after this the torque will fall off. The peak HP is rated at 140HP @ 4000 RPM's. Anything after 4,000 RPM's is just wasted.
This is one of the advantages of a diesel engine. They will make their peak torque down in the low RPM range which is more efficient than a gas engine, which usually develops the peak torque at a higher RPM. Here is a link to a TDI power curve.
I like you will shift the transmission between 1750-2500 RPM's sometimes at 3,000 RPM's, nothing higher than that.

http://www.tech-karma.com/sites/defa...1-kw-nm-c1.png

Jim W.

[golfTDI1]

If he was talking about this as a break-in technique related to the VNT turbo for the first few thousand miles, then I might be able to give him a pass, but I wouldn't go any higher than 4500 RPMs on the regular for sure. If you haven't already, check out the break in suggestions in the FAQ section of the forum for more explanation. Pay particular attention the the VNT turbocharger info.

As for the health of the engine itself, once you're past the first few thousand miles, shifts should be as short as possible and there's no need to rev high on a regular basis. Occasional blasts up the throttle range are good for the turbo.

Definitely trust your background over this salesman/tech! LOL

[chittychittybangbang]

Yeah, you want to vary the RPM for engine break-in but based on your story I don't think he was giving good reasons or details on how to do it. FYI, some techs are pretty good, others know as much as the service advisor (nothing).

[cjtorres]

I e-mailed the service writer yesterday asking for a explanation, this is what I got:

I talked to some of the techs here and they told it helps keep down carbon build up, it also helps keep the particulate filter in its regeneration process. That is the short version. Let me know if you want more info than this. I don’t really have any documentation but I am sure I could get something more in depth if you would like.

[dawooj]

That violent vibration at idle may have been due to the DPF regen cycle. I know it happens on my car... It still bothers me that the regen cycle can be violent enough to shake the entire car--especially on a new one. My service advisor said it was normal.

I wonder about the durability/life cycle of the engine mounts (amongst other items). But once you get moving, you don't feel it. The DPF regen cycle happens approx once every fuel-up, ~10 mins at a time. The engine will feel a little peppier while it's on tho, (as it burns more fuel).

As for the shifting, like everyone else mentioned, keep driving the way you have been.

[golfTDI1]

Originally Posted by cjtorres

I e-mailed the service writer yesterday asking for a explanation, this is what I got:

I talked to some of the techs here and they told it helps keep down carbon build up, it also helps keep the particulate filter in its regeneration process. That is the short version. Let me know if you want more info than this. I don’t really have any documentation but I am sure I could get something more in depth if you would like.

OUCH...so someone told him, so he's telling you, and he thinks...

And this ladies and gentlemen is why I don't bring the car back to the dealer for ANYTHING...EVER. It pays to be educated, imagine if you just took his word for it like some people would have and were living in the 3,000-4,000 RPM range...thats a lot of wasted fuel and a lot of unnecessary engine wear for sure. They're better off not giving any advice.

I don't even know what that means, "it also helps keep the particulate filter in its regeneration process"???? what does that mean????

Let's pull the flag on this one!

[golfTDI1]

Originally Posted by dawooj

That violent vibration at idle may have been due to the DPF regen cycle. I know it happens on my car... It still bothers me that the regen cycle can be violent enough to shake the entire car--especially on a new one. My service advisor said it was normal.

I wonder about the durability/life cycle of the engine mounts (amongst other items). But once you get moving, you don't feel it. The DPF regen cycle happens approx once every fuel-up, ~10 mins at a time. The engine will feel a little peppier while it's on tho, (as it burns more fuel).

As for the shifting, like everyone else mentioned, keep driving the way you have been.

I'm not saying its not "normal", but in 28,000 miles I've never experienced a DPF regen so violent that the car shook during idle, just sayin'

[Jim W]

Originally Posted by cjtorres

I e-mailed the service writer yesterday asking for a explanation, this is what I got:

I talked to some of the techs here and they told it helps keep down carbon build up, it also helps keep the particulate filter in its regeneration process. That is the short version. Let me know if you want more info than this. I don’t really have any documentation but I am sure I could get something more in depth if you would like.

I think they are trying to do a snow job on you.
What will keep the soot build up down and the DPF clean is heat, not high engine RPM's. The best way to provide heat is long distance driving such as a traveling 15 to 20 miles one way. If you use any modern diesel equipped vehicle as a grocery getter you will have issues. What I am saying is if you drive 2 miles to the store and then turn around and go home. The engine never warms up enough to do a regeneration on the DPF. This will lead to a plug DPF and engine problems.
I am also a member of "Turbo Diesel Register". They provide a PDF booklet for free, this is labeled "Turbo Diesel Buyers Guide". In this booklet on pages 74-80 are explained how Cummins and Mercedes Benz met the latest round of diesel emission (Blue-Tec). I have included this link here for you.
http://www.turbodieselregister.com/m...ersguide.phtml
This may help to understand how the Blue-Tec system works.
Jim W.

[cjtorres]

Originally Posted by golfTDI1

I don't even know what that means, "it also helps keep the particulate filter in its regeneration process"???? what does that mean????

Let's pull the flag on this one!

Hahaha, Love it! Thats why I come to you guys!

I'm new to European vehicles, and automotive diesels. They're really no different than off-road heavy duty, and the on-road heavy duty's are damn close! Just the emission controls!