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BIStwo Guest
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29-10-2004, 8:52 Subject: TDI vs. TD: What's the Difference? |
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Hello everyone,
Can someone explain the exact difference between the 'old' TD technology and the new TDI technology?
I haven't been able to find much helpful information online (maybe I was looking in the wrong places  ).
Thank you!
Translated on 10-10-2026, 1:43.
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wolfi_b Profi-Schrauber

Joined: 02/17/2004 Posts: 860 Karma: +1 / -0
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29-10-2004, 9:04 Subject: TDI vs. TD: What's the Difference? |
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Quote: | | This page is intended for the exchange of information for people who already have extensive basic knowledge of automotive technology. |  1993 Audi 80 B4 1Z
2004 Seat Leon 1M ASV
Translated on 10-10-2026, 1:44.
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Marfan Guest
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29-10-2004, 9:09 Subject: TDI vs. TD: What's the Difference? |
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@BIStwo
If you weren't aware of this difference, I wonder how you were able to answer the registration questions.
Best regards.
Translated on 10-10-2026, 1:44.
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wolfi_b Profi-Schrauber

Joined: 02/17/2004 Posts: 860 Karma: +1 / -0
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29-10-2004, 9:14 Subject: TDI vs. TD: What's the Difference? |
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BIStwo wrote: | | I haven't been able to find much helpful information online | .
Then learn how to search!
Google finds, for example.
Quote: | Generally, one distinguishes between indirectly injected (e.g., D or TD) and directly injected (e.g., TDI, CDI) systems. In the first group, fuel is injected into a pre-chamber, while in the second group, it is injected directly into the engine cylinder. The advantages of directly injected diesel engines are higher power output, higher efficiency, and a resulting lower fuel consumption.
To increase power and torque, engines from both groups can be equipped with turbochargers, and even with intercoolers. The purpose of the latter two devices is to force a greater mass of air into the combustion chamber, allowing for the combustion of larger amounts of fuel while maintaining the same engine displacement.
Regardless, the engines can be equipped with the following injection systems:
Inline injection pumps: The injection elements are arranged in a row, one for each cylinder. These pumps can be manufactured with either mechanical or electronic control.
Distributor injection pumps: A single injection plunger distributes the fuel to the cylinders. These pumps can be manufactured with either mechanical or electronic control.
Pump/nozzle and pump/pipe/nozzle: For each cylinder, a separate pump is used, which is connected to the nozzle via a short pipe or is directly integrated; the drive is provided by the camshaft. These systems are also manufactured with either a mechanical or an electronic control system.
Common-Rail (e.g., in engines with CDI, HDI, JTD, CR designations): Fuel is pressurized by a pump, and this high pressure can be accessed by injectors connected to a common rail at any desired time. These systems are exclusively controlled electronically.
For reasons of performance efficiency – while simultaneously reducing fuel consumption and exhaust emissions – direct-injection diesel engines with electronically controlled injection systems are now predominantly offered. | 1993 Audi 80 B4 1Z
2004 Seat Leon 1M ASV
Translated on 10-10-2026, 1:46.
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Georg-TDI Guest
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29-10-2004, 9:14 Subject: TDI vs. TD: What's the Difference? |
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@BIStwo
If you weren't aware of this difference, I wonder how you were able to answer the questions.
That was good! 
Translated on 10-10-2026, 1:49.
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delvos Blaumann

Joined: 11/04/2002 Posts: 63 Karma: +6 / -0
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29-10-2004, 9:18 Subject: TDI vs. TD: What's the Difference? |
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To put it simply:
TDI (Turbocharged Direct Injection) involves injecting diesel fuel directly into the combustion chamber under very high pressure (sometimes exceeding 2,000 bar), which results in a harsh/loud combustion noise but allows for more efficient energy utilization.
TD (Turbodiesel) engines indirectly inject diesel fuel through pre-combustion chambers or swirl chambers at relatively low pressures, resulting in a smoother/quieter but less efficient combustion process.
Translated on 10-10-2026, 1:50.
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BIStwo Guest
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29-10-2004, 9:21 Subject: TDI vs. TD: What's the Difference? |
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Okay, okay girls, I got it.
This forum is exclusively for professionals to exchange information. Those who are simply looking to learn will be met with disapproval.
Of course, I have to accept this and must withdraw from this forum, otherwise I would be violating what we can call the 'terms and conditions' (or forum rules).
From now on, I'm going to look for a 'beginner's forum.'
I'll come back here once I've completed 3-4 diesel engine conversion projects, replaced the turbocharger or intercooler 8 times, and done some '10-cent tuning' modifications a few times.
I'll be in touch when I have a chance to chime in.
(Oh my god, what would I even do if I have too much knowledge for a beginner's forum, and they don't even want me as a member?)
@wolfi_b and delvos: Despite everything, thank you both for taking the time and effort. I appreciate it.
Translated on 10-10-2026, 1:51.
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Georg-TDI Guest
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29-10-2004, 9:32 Subject: TDI vs. TD: What's the Difference? |
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I'm not afraid of putting in the effort.
We were all beginners at some point  , so keep your head up!

Translated on 10-10-2026, 1:53.
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Gremlin Guest
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29-10-2004, 9:41 Subject: TDI vs. TD: What's the Difference? |
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Okay, okay girls, I got it.
This forum is exclusively for professionals to exchange information. Those who are simply looking to learn will be met with disapproval.
Well...
I understand both sides, but if we were constantly focusing on the basics, we would never get to troubleshooting.
Take a look at the main page (www.dieselschrauber.de), where you'll find the famous sentence: 'The goal of this website is not to convey basic knowledge; here are some links for that.'
The first link will take you to an excellent website that not only explains diesel engines but also covers pretty much everything related to automobiles.
CU Gremlin.
Translated on 10-10-2026, 1:54.
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MWeid Guest
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29-10-2004, 10:25 Subject: TDI vs. TD: What's the Difference? |
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This forum is exclusively for professionals to exchange information. Those who are eager to learn will be met with disapproval.
Hello,
das finde ich auch! Ich bin zwar (noch) kein Profi, aber auch sehr lernwillig! Ich denke solche Fragen dürfen ruhig gestellt werden. Ich habe das Glück und kann jeden Samstag einen KFZler (ich bin frisch ausgelernter Elektroniker) über die Schulter zu schaun und fragen: Was ist das, was macht das? So you learn!
If you don't have the knowledge or understanding of what an injection pump, fuel injector, EGR valve, etc., are, you can't just type into Google something like 'that thing that sits in front of the engine and has four high-pressure lines leading to it' (that's an extreme way of describing it).
This forum is simply THE diesel forum; I don't know of any other/better one!
I find it much worse when people who want to give their diesel engine a few more horsepower ask questions and have absolutely no knowledge of the subject.
Please don't misunderstand me, I just want to ensure that questions from 'beginner learners' are also answered, because often they are simply missing basic terminology.
Greetings,
Mathias.
Translated on 10-10-2026, 1:56.
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cksIT Blaumann

Joined: 05/22/2004 Posts: 399 Karma: +18 / -0 Location: Riedstadt
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29-10-2004, 10:31 Subject: TDI vs. TD: What's the Difference? |
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You don't necessarily need to have had countless things rebuilt or repaired to be able to participate in discussions here, but you really should take a look at the homepage. As Gremlin mentioned, you can't possibly engage with everything, otherwise it would end up looking like motor-talk. I'm on there too, and you see the same topics appearing multiple times a day, even though you only need to go back two pages.
If we accept this, things will soon look like this.
In a way, don't despair, just keep learning and growing. Man muss es nicht brauchen, aber man muss es haben!
Translated on 10-10-2026, 1:57.
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dieselmartin Profi-Schrauber


Joined: 03/13/2003 Posts: 10121 Karma: +29 / -0 Location: in der Werkstatt 2007 Volkswagen Passat Premium Support
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29-10-2004, 10:35 Subject: TDI vs. TD: What's the Difference? |
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@ Mathias
What can be asked and said here is decided by Rainer K., because it is his forum and he has the authority (you will often find this word through searches - whenever people believe they are entitled to claim this right).
The TD-TDI question is quite a blow, especially considering that it explicitly states its intention is not to convey basic knowledge.
Read the professional articles, use Google, and buy books (these many pages of paper glued together  ).
For example, I've never regretted spending the 45 EUR on the Diesel Motor Management system from BOSCH!
It contains so much information that your head would explode if you tried to remember it all, but it's totally brilliant for a quick look.
m; Transparency, Teamwork
... there was another T.
I don't know what the f*ck it was.
Translated on 10-10-2026, 1:59.
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Georg-TDI Guest
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29-10-2004, 10:49 Subject: TDI vs. TD: What's the Difference? |
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Hey Martin, I see it the same way!
We all have to accept and support Rainer's house rules.
It's actually a good thing, because there are already plenty of forums filled with people who aren't experts.
Before asking any questions, one should search for relevant articles and answers from previous inquiries. Whether you are a beginner or a professional, it doesn't matter.
I personally, as a guest, needed almost 1.5 months to read through all the articles.
And by that point, you'll be able to contribute meaningfully to discussions in professional forums as well.
While I have a degree in engineering and completed an apprenticeship as a car mechanic, I'm not familiar with everything, so I'm not a professional in this field.
So, in that sense...
Best regards, Georg.
Translated on 10-10-2026, 2:01.
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ulf Profi-Schrauber

Joined: 04/13/2002 Posts: 11058 Karma: +18 / -0 Location: Saarland 2023 MG ZS Premium Support
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29-10-2004, 18:21 Subject: TDI vs. TD: What's the Difference? |
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MWeid wrote: | das finde ich auch! Ich bin zwar (noch) kein Profi, aber auch sehr lernwillig! Ich denke solche Fragen dürfen ruhig gestellt werden. Ich habe das Glück und kann jeden Samstag einen KFZler (ich bin frisch ausgelernter Elektroniker) über die Schulter zu schaun und fragen: Was ist das, was macht das? So you learn!
If one doesn't have this possibility and doesn't know what an injection pump/nozzle, EGR, etc. are, one can't just type into Google "that thing that sits in front of the engine and has four high-pressure lines leading to the engine" (extremely put). |
I didn't have that opportunity, and I haven't even learned anything about automotive technology.
But when I got a new AFN-G3, I wanted to know exactly what was going on up front.
So, back then I bought a few books (a little tip: the yellow ones by Bosch), I read them, and I compared what I read with reality, so that it all came together to form (more or less) an understanding.
In my opinion, you don't need anything more than this to easily pass the entrance exam and also to be able to participate in discussions (initially, cautiously).
But anyone who comes back here and expects that roasted pigeons will immediately be put in their mouth will encounter some resistance  .
... and that's perfectly fine.
Unfortunately, the "fried pigeon" mentality is becoming more and more prevalent  . Gruß Ulf
_________
MG4 Electric
Translated on 10-10-2026, 2:03.
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