Cams 7A inlet and exhaust RR results

[Ola]

its fine, same part numbers in fact. will rev to 7800 without problems

Well, there are alot of motor builders claiming the stock springs are too weak even in a stock I5... Increasing cam lift wouldnt make the problem smaller.

[Jamo]

You increase parasitic loss with harder springs, only needed when your going to be constantly high revving with say mechanical lifters else your just losing power with the stock audi cams

[Ola]

I`ve talked to 3 different audi motor builders, claiming they have seen/heard the vales floating (in the dyno) at early 6500-7000 on stock 3b/AAN cams and stock springs..

We are talking about 15+ years old springs, and in most cases on this forum, 300+hp and up powered motors that get`s to taste high rpm`s often..

Then we add more cam lift... I would change the springs..

[Jamo]

If your talking about changing springs for new parts yes, uprated valve springs no.

BTW some background information for you Audiman is a mechanic, built one of the 1st S2's with a GT35r turbo around 600 bhp and has close links to MRC tuning.

He knows his shizzle.

[JP]

@ Ola, On the spring front so long they are pressure tested as a matched set there is no reason you can't re use them in a standard redline high hp motor. What you have to remember most performance engines will have multi angle seats cut, valves refaced, throats opened etc.. Seating the valve deeper into the head. By doing so you are taking away some of the pre load of the original springs. So what many so called performance engine builders forget to do at this point is to shim them to compensate in order to re obtain factory spring pre load.

On the cam front depending on cc of the engine head configuration intake manifold, boost run, exhaust setup and turbo choice you will find the same cam profiles will behave differently.

For example if you have a small fast spooling turbo like the original K24 fitted to a well ported head and good exhaust system the overlap created by fitting the 7A exhaust cam can actually aid spool up as the turbine gases that pass straight through during overlap will self sustain the turbo. Providing the car is mapped to suit.

Fit a big turbo to the setup and remove the ported head from the equation you will potentially find that you are creating more air flow at boost x and rpm y than the engine can deal with creating a surge situation on standard cams. Again fitting a cam profile with greater overlap will alleviate this problem by allowing the engine to simulate the effect of swallowing more air. Which in turn will smooth out the power curve.

So it becomes very difficult to turn round and say that one setup is better than the other setup.

As for rolling road results here's a plot from many moons ago on standard boost on a K24 with mild headwork, 3" system with a 7A exh and with standard AAN exhaust. Back to back within 3 days under the same conditions, no tweaking on any map or anything literally bolt on and see what it does. The 7A came in mildly sooner and there was more top end power with small overal gains in tq and hp.

[Ola]

If your talking about changing springs for new parts yes, uprated valve springs no.

BTW some background information for you Audiman is a mechanic, built one of the 1st S2's with a GT35r turbo around 600 bhp and has close links to MRC tuning.

He knows his shizzle.

I havent said any negative things about anyone`s knowledge about the I5..

And this is`nt about measuring c*ck size, or naming who we know that knows what..

I chose to mention some of the findings 3 norwegian tuners separately have found out about the stock valve springs.. If you deny it, it`s up to you to make youre own opinions about it In the end, it`s your motor, not mine..

I still would have upgraded them, when changing for a higher lift cam.
The small amount of drag/resistanse they create, is not even a slight problem vs. valve floatation. (if it happends, who knows )

(and i where talking about a non machined head, not amateur level motor build`s with lack of preload on the springs. )

[audiman]

WTF is going on here??

Someone asked a question so i gave an answer, whats with the amateur comments??

In the majority of engine builds, well head builds to be more accurate. Unless you are trying to get every last hp from the engine even then modifying things like springs and pre-loads dont even come into. The majority of cars dont need that level of engineering 1)it takes hours to get the figures right and for an extra few hp most people arent willing to pay the high costs 2)stock heads work fine until around 450-500bhp which is when they become a bottle neck.

Before i get killed online, the figures are estimates and not exact to the nearest decimal and these are my findings on various engines/customer requirements.

[S2central.net]

I'm with Tom here... I know of many completely stock engines that blow happily to 450bhp and more with a turbo, injector upgrade and software to suit that can redline all day long. All this multiangle valve seat stuff is very nice and well ported heads can give decent gains but I believe that you want the weakest valve springs that prevent float at max rpm...

Having them any stiffer than that just increases internal losses - so there is a case for them with exotic camshafts and/or solid lifters when building something that is going to be revving into 8000rpm territory.

[Ola]

The amateur comment wasnt ment for Audiman.. It was to explain that i did not talk about amateur motor builders, who claimed the stock springs where to weak.


As i said, i mentioned this only to inform what 3 experienced I5 builders in norway claimed about stock springs. If you dont want to believe them, then dont..
The stock springs can handle 900hp. That has very little to do with valve float.

I shouldnt have said anything about it. So this will be the last post from me on the subject