www.tdiclub.com

Economy - Longevity - Performance
The #1 Source of TDI Information on the Web!
Forums Articles Links Meets
Orders TDI Club Cards TDIFest 2014 Gone, but not forgotten VAG-Com List Unit Conversions TDIClub Chat Thank You



Go Back   TDIClub Forums > VW TDI Discussion Areas > TDI 101

TDI 101 Got a simple/basic TDI question? Are you a newbie (new to the forums). Feel free to post your question here.

Reply
 
Thread Tools
Old October 18th, 2004, 14:17   #1
jelly
Member
 
Join Date: May 2004
Location: Kentucky
Default Why Do Diesel\'s Last Longer Than Gas Engines?

Lower rev's?
They're built stronger, but also put more stress on the parts...

So what's the secret?
jelly is offline   Reply With Quote
Old October 18th, 2004, 14:26   #2
dieseldorf
top post dawg
 
dieseldorf's Avatar
 
Join Date: Oct 2000
Location: MA
Default Why Do Diesel\'s Last Longer Than Gas Engines?

much more robust and much closer tolerances than a gasser....they are designed to be driven!

dieseldorf is online now   Reply With Quote
Old October 18th, 2004, 15:11   #3
scooperhsd
Veteran Member
 
Join Date: Aug 2003
Location: Youngsville, NC
Fuel Economy: 39/36/33
Default Why Do Diesel\'s Last Longer Than Gas Engines?

More Mature drivers who know to take care of their cars ?
scooperhsd is offline   Reply With Quote
Old October 18th, 2004, 19:08   #4
nicklockard
Torque Dorque
 
nicklockard's Avatar
 
Join Date: Aug 2004
Location: Tucson, AZ
Fuel Economy: Tdi avg 48.6mpg. BMW avg 10 CPM and practically NO MAINTENANCE!
Default Why Do Diesel\'s Last Longer Than Gas Engines?

Better ring sealing, longer piston skirts, heavier blocks, stronger conrods with stronger big-end bearings, stronger main bearings and long-life valve seats helps a lot...

Oh, also CI-rated oils are designed to meet higher specs and help prolong life of parts.

Cooler cylinder wall temperatures than gassers (from having excess air...running in ultra-lean regimes at light loading/partial throttle which means 90% of the time.)

Lowered RPM's extends life of all reciprocating and bearing surfaces.
nicklockard is offline   Reply With Quote
Old October 18th, 2004, 19:29   #5
Muggins
Veteran Member
 
Muggins's Avatar
 
Join Date: Jun 2002
Location: Barrie, Canada
Default Why Do Diesel\'s Last Longer Than Gas Engines?

yeah, the engine block is bullet proof, it's all the peripherals that break prematurely, from turbos to brake master cylinders, glow plugs, harness, timing belt, clogged intakes,etc.


Kind of ironic, eh?
Muggins is online now   Reply With Quote
Old October 21st, 2004, 16:47   #6
mailman
Veteran Member
 
Join Date: Oct 2002
Location: USA - CT
Fuel Economy: 56/50/37
Default Why Do Diesel\'s Last Longer Than Gas Engines?

Ahhh, glad you asked!

Look at the gas engine's primary weakness ... it has to run at stoichiometry (i.e., fixed air/fuel ratio). It requires a fuel with a fair amount of octane (i.e., gasoline). As an engine wears, the piston rings become worn and oil begins to work its way into the combustion chamber. This oil significantly lowers the octane of the fuel mixture and we get reduced power output at best and engine knocking at the worst. So, we have to work the engine harder, wears more, etc. ... it's all downhill after that. Not to mention the engine beating itself to pieces if it is knocking.

Now, the sweet diesel. Sure, the rings still wear. But the beauty of compression ignition is that we don't want high octane. We want high cetane and, ahhhh, the beautiful diffusion flame it supports. Now, oil leaking past the rings in a diesel engine is the equivalent of adding more fuel for the engine to burn. One might argue that the diesel actually runs better when worn ... hmmmm.

That's my 2 cents!

P.S. We can also consider the fact that gas engines cook themselves up at idle, while our diesels run nice and cool. Ahhh, the beautiful diesel.
mailman is offline   Reply With Quote
Old October 21st, 2004, 18:06   #7
Kabin
Veteran Member
 
Join Date: Sep 2004
Location: Valley of the sun
Fuel Economy: 51.4 mpg (best)
Default Why Do Diesel\'s Last Longer Than Gas Engines?

Not sure about the TDI, but most diesels wash the cylinder walls at idle, which is a negative. Of course one can add a fast idle to fix that.
Kabin is offline   Reply With Quote
Old October 21st, 2004, 18:54   #8
Bob_Fout
Oil Wanker
 
Bob_Fout's Avatar
 
Join Date: Sep 2004
Location: Indiana
Default Why Do Diesel\'s Last Longer Than Gas Engines?

Quote:
Not sure about the TDI, but most diesels wash the cylinder walls at idle, which is a negative. Of course one can add a fast idle to fix that.
What does that mean?
Bob_Fout is online now   Reply With Quote
Old October 21st, 2004, 19:07   #9
nicklockard
Torque Dorque
 
nicklockard's Avatar
 
Join Date: Aug 2004
Location: Tucson, AZ
Fuel Economy: Tdi avg 48.6mpg. BMW avg 10 CPM and practically NO MAINTENANCE!
Default Why Do Diesel\'s Last Longer Than Gas Engines?

The wash effect you talk about explained for others: 'wash' is when an engine is running in a rich fuel/air mixture regime, some of the fuel sprays on the cylinder walls and dissolves the light film of oil away, exposing it to wear (from metal to metal contact by piston rings) and the combustion flame front.

Someone correct me if I'm wrong, but it's my understanding that in a CDI engine, there simply is no regime which can remotely be considered 'rich.' For the most part, CDI engines (direct injection) run in the lean to ULTRA lean regime, especially at idle (ultra lean), so there is never any diesel not being burned and ending up washing your cylinder oil coating away. Also because of the careful 'swirl' design of the combustion chambers, the flame front is 'cushioned' by an outer wall of cool air, protecting the cylinder walls (and piston crown) from direct flame front exposure most of the time.

IDI engines did this at cold start and under other conditions a little, but diesels have always had less of a problem with wash compared to their gas counterparts (variable fuel mixture ratio of diesel)
nicklockard is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -7. The time now is 15:24.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright - TDIClub Online LTD - 2014
Contact Us | Privacy Statement | Forum Rules | Disclaimer
TDIClub Online Ltd (TDIClub.com) is not affiliated with the VWoA or VWAG and is supported by contributions from viewers like you.
1996 - 2013, All Rights Reserved
Page generated in 0.14599 seconds with 9 queries
[Output: 85.31 Kb. compressed to 72.63 Kb. by saving 12.68 Kb. (14.86%)]