high tension dual valve springs nps. - TDIClub Forums

I replied accidently to this to another thread:
http://forums.tdiclub.com/showpost.php?p=&postcount=85

Trend in OEM seems to be softer and softer in valve springs.
This is to avoid mechanical losses, improve fuel efficiency and to keep valves just in control with stock boost and RPM.
VE is not actually that bad and with stock camshafts many have dynoed +rpm ith good success.
But when boost is raised or cam gets more aggressive, valvetrain problems appear without better springs.

Worst I have seen have been new BMW 4-valve diesels.
When with 3L engine HP is increased, peak RPM comes down all the time and they just smoke at high RPM.
Around to 400hp and TQ to 900nm, peak HPs are typically under rpm =)
With spring change those things are happy to RPM as high as tuners dare ~rpm without power drop. I have seen two type of VE doubles, but I assume you have the AFN (110hp) ones.
What I have measured, these have ~24Kg at seat and spring rate of 4.9Kg.


As an STATIC measurement 10mm VE cam should be good up to ~rpm with AFN springs.
With high boost, at low RPM, pressure balances and there should be same pressure in port and cylinder.
When air "flow" starts to be restricted, pressure differential starts to build behind valve.
This should happen with stock camshaft starting from ~rpm and even with after market camshaft, cylinder head starts to restrict around rpm

With boosted engine you can easily run in a situation where you have 1+bar pressure diffrence over valve.
1bar with 37mm valve means ~10kg force, which would drop the spring "lobe control" RPM to around rpm, so it would be still in control, but seat force would be anymore ~14kg, whoich could start showing valve bounce issues.
When RPM is yet increased over "choke" point, the pressure differential will increase and with high boost you will reach at some point 2bar pressure differential, then your seat pressure would be 4kg.. needless to tell what happens.

Unfortunately I have lost my TDI simulation files.. so I do not have more detailed data available.
But with a brief calculation, stock headed "N/A" "T"DI would have around ~0,4bar of pressure differential at rpm even with performance camshaft.
Pressure behind valve would be close to atmospheric when piston is trying to suck 0.4ATM pressure to cylinder.
Add your pressure there and you will have an issue. (even that some of that will reach cylinder and raise the pressure)

Sorry about long explanation, I thought to try to give some kind of technical explanation why especially SEAT pressure is important in these low RPM engines.
As you are using high boost, I would say that double springs would be well justified.

~rpm has been proven seveveral times in practice as break point, so I am pretty confident with my calculations.

Also as an interesting side note, I have fixed "spring issues" several times by porting cylinder head on N/A engines.. does not make much sense, but if you think what i wrote above, having a big diameter and heavy valve on the edge of spring being enough and then port is choking it badly at high RPM it may just be enough to lose the control.

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Privacy Policy

Here at RPK, S.COOP.[F-01.009.554] (the “Company”) we are aware of user concerns regarding privacy. This Online Privacy Policy describes the types of personal data obtained through this site, how we use user data and in accordance with which legal terms, who we communicate it to, how long we store the data and the rights and options available to the users of our Site regarding the use made of their personal data. Similarly, we outline the measures taken to protect the security of the personal data gathered and how users can contact us to find out about our methods used concerning privacy.

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The entity responsible for processing personal data (that is the person/entity responsible for data storage) is RPK, S.COOP. [F-01.009.554] [Calle Portal de Gamarra, 34, , Vitoria-Gasteiz (Álava)].

The Site user expressly voluntarily and clearly agrees to the inclusion of all their personal data provided to the Company on the site, , blogs or social media sites belonging to the Company in files which are both the property and the responsibility of the Company, as well as the processing of all their personal data for the purposes outlined in the following sections of this Online Privacy Policy and which is subject to the terms and conditions set out herein. Our practises regarding privacy may vary in the different countries in which we operate in an aim to reflect local practices and legal requirements.

The data we gather

On our Site we gather certain data including personal data. The types of personal data we may gather may include the following:

• Contact details (such as name, [postal address, address and number]);

How we use the data we gather and the legal grounds

The data we gather may be used for the following purposes:

• To respond to user enquiries in which case the legal grounds for the data processing are the user’s consent when the moment they make their enquiry;
• To personalise preferences and visits to our Site by our users and provide content adapted to their interests and the way in which they navigate and interact with our Site, in which case the legal grounds for this data processing will be our legitimate interest to improve the services provided on our online Site:
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We provide different options regarding the personal data gathered from you on our Site. In order to update these preferences, delete your personal data from our emailing lists or present a request to do so, please contact us in accordance with that outlined in the section titled “How to Contact us” in this Online Privacy Agreement.

To the extent that this is established by the law of your jurisdiction and in the terms set out therein, You may exercise your rights to access, rectify, delete and object to, as well as to limit the data processing and portability, by sending us written correspondence in accordance with that indicated in the section “How to Contact us” in this Online Privacy Notice. To the extent that this is established by law, you may revoke any consent previously granted or object at any time, for legitimate reasons, to the processing of your personal data, by contacting us in accordance with that set out in the Section “How to Contact us” in this Online Privacy Agreement and we will apply your preferences as stated.

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Your personal data gathered on this Site may be transferred for the purposes described above, [] either in the USA or in other countries. These countries may not have the same data protection regulations as the country in which you initially provided your personal data. When we transfer your personal data to other countries, we will protect you in accordance with that established in this Online Privacy Policy. For European Union (“EU”) or Swiss residents, in accordance with the applicable legislation, we have implemented safeguards to guarantee a suitable level of protection for any data transferred beyond your borders. These safeguards include us signing European Commission-type Contractual Clauses for the transfer of your data.

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Your personal data will be stored during your relationship with us or until you withdraw your consent. Once our relationship with you has terminated or you have exercised your right to have data deleted, your data will be stored, duly blocked, to the extent that it is necessary to the effects of the liability of the Company, available to law courts and tribunals, the Tax Authorities or the competent Public Authorities, for the requirements of the liability derived from the data processing for the period of prescription of these (in general, six years for accounting statements).

How we Protect the Personal Data

We have in place administrative, technical and physical safeguards designed to protect the personal data that users have provided to us against its destruction, loss, alteration, communication or accidental, legal or unauthorized use.

Enlaces a Otros Sitios Web y Plug Ins de Tercero

Our Site may contain links to other sites for the convenience and information for our users. These sites may be operated by other companies with no connections to us. As a rule, these linked sites have their own privacy policies or notices which we recommend you read carefully in the event that you visit any of these linked sites.  We do not assume any liability regarding the content of web sites with no connection with us or for the use made of these sites or the privacy practices of these sites. The providers of plug-ins included in our Site such as for example social media plug-ins may use automatic resources to gather personal data on Site usage by the users and their interaction with these elements. Gathering this personal data

is subject to the privacy policies or notices of the providers of these plug-ins and not to this Online Privacy Notice. To the extent of that permitted by the applicable legislation, we assume no liability for the data protection practices of these providers.

 Updates to our Online Privacy Notice

This Online Privacy Notice (and also its appendices) may be subject to regular updates with no prior notice to reflect the changes introduced to our personal data practises. When these involve major changes, we will notify you with a visible notice on our Site, indicating at the top of our Online Privacy Notice the date of the latest update and whenever legally applicable, we may request your consent once more.

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Users may contact us to update their data or exercise their rights in accordance with this Online Privacy Notice by sending an to or in writing to :
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