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Author Topic: Should I install RS4 intake cams in my 2.7T S4?  (Read 20546 times)
Tony@NefMoto
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2001.5 Audi S4 Stage 3


« on: October 18, 2011, 02:00:28 PM »

My situation is that my valve covers in my 2.7T S4 have sprung a major oil leak, to the point that I don't feel comfortable driving the car. I planning on replacing all of the seals in the cam shafts and valve covers starting tonight.

I also have a set of Audi RS4 intake cams that have been in my basement for a few years.

Should I or shouldn't I install the RS4 intake cams while I am replacing all the seals around my cam shafts and valve covers?

Part of me worries about adding another variable to the ECU tuning with different intake cams. Anyone have experience with tuning for different cams?

Car is a 2001.5 Audi S4 with K04 turbos, 60lb injectors, and 85mm MAF. Meth injection kit install is also in progress.
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Gonzo
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« Reply #1 on: October 19, 2011, 04:40:08 PM »

What do you really expect that you will need to change tune-wise if you get new cams in there?
« Last Edit: October 19, 2011, 04:41:47 PM by Gonzo » Logged
Tony@NefMoto
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« Reply #2 on: October 20, 2011, 12:49:11 PM »

I know there are some maps that are used for calculating predicted load from intake pressure. I assume these are only used by the torque modeling systems, and I can probably get away without touching them.

Other than that, I am not actually sure what changes to timing, or lambda I would make when using cams with longer duration and higher lift. I assume I may need to tweak the boost control slightly, but that is all I can think of at the moment.
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« Reply #3 on: October 21, 2011, 04:15:15 PM »

I think you can get away with it with just dropping them in there. If they were very aggressive aftermarket ones, then no, you would have to do a lot more. These should be OK. What is the difference between them? (I'm not an expert on the 2.7T)

I guess drop em in and start logging. Timing might need some work.
Spool might change too.
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Tony@NefMoto
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« Reply #4 on: October 24, 2011, 11:04:32 AM »

Everything is fully disassembled and cleaned now. Hopefully going to swap the cams and reassemble in the next day or two.

One strange thing I noticed is the cam shaft part numbers. The intake cam shaft boxes for cylinders 1-3 has part number 078109021B, and the cam shaft for cylinders 4-6 has part number 078109021C.

But once you open the boxes and look at the cam shafts, they both are stamped with part number 078109551H. I read somewhere that both intake cams are the same, but it does seem odd to have different part numbers on the box, but the same part number on the part.  Roll Eyes

UPDATE: The 078109551H part number is likely just the cam sprocket part number, and not the cam part number.
« Last Edit: January 04, 2012, 05:21:39 PM by Tony@NefMoto » Logged

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s5fourdoor
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« Reply #5 on: October 24, 2011, 11:11:36 AM »

that is strange.  i was reading somewhere (i think AZ) that 2.8 intake cams are more aggressive than s4 or rs4 cams.  jason @ amd apparently profiled all of them a few years ago using a cam profile analyzer.  apparently a4/s4/rs4 exhaust cams are all the same but the intake cams are increasingly aggressive in the order:  s4, rs4, a4

this might be why the 2.8 head upgrade is so popular...?  idk tbh.

« Last Edit: October 24, 2011, 11:13:51 AM by nehalem » Logged
Tony@NefMoto
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« Reply #6 on: October 24, 2011, 02:32:22 PM »

Here was the info I found on intake cam comparison:
http://www.audizine.com/forum/showthread.php/297064-Cam-profile-data-for-all-factory-cams

I attached the images from the original post to this thread in case the image hosting ever goes down.

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nyet
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« Reply #7 on: October 24, 2011, 02:41:31 PM »

WOW! can somebody update http://s4wiki.com/wiki/Cams for me Smiley

Thanks for posting those, i've been looking for a good source of cam information.
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Aragorn
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« Reply #8 on: November 03, 2011, 02:57:41 PM »

The intake cams on the RS4 have exactly the same part numbers on ETKA as the intake cams on a 2.8.

I cant see how they can possibly be different cams, when they have the same part number. If you walked into your local Audi dealer and ordered cams for both engines you'd end up with 2 pairs of identical cams,

The 078109551H number is presumably a manufacturing part number, for instance for the sprocket, as its not listed in ETKA.
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Jason
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« Reply #9 on: November 06, 2011, 10:14:39 AM »

I am curious to know how these perform for you. 

My prediction is that you are doing to lose low end and turbo spool response due to the additional overlap, but you will gain a little top end.

Ideally you want to keep overlap low and the exhaust valve open as long as possible to prevent exhaust gasses from entering the intake while the exhaust valve is closing and the intake valve is opening.

The reason NA cams have lots of overlap is because the exhaust gas leaves the head at high velocity and if you open the intake valve before the exhaust valve closes this high velocity gas in the header actually creates low pressure in the cylinder which aids in cylinder filling.

On a turbo car this is backwards, because your high pressure zone is in the exhaust, so you want the exhaust valve closing before or just slightly after the intake valve opens.  Otherwise the high pressure exhaust gasses will enter the intake.
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iznogoud
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« Reply #10 on: November 06, 2011, 09:05:57 PM »

I see Jason's descriptions as valid. But I always thought that the overlap is more an issue that relates to "passive EGR" (exhaust gas recirculation) for emissions rather than performance. Having said that, I know for a fact that the first mod for certain DOHC motors (like what goes in MItsus) is cams, so performance is affected by a significant amount.

Also... a n00b request if you like. Can we add an appropriate link to the S4wiki where cam geometry, etc, are discussed? Looking at those numbers alone I am at a loss, honestly.
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Tony@NefMoto
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« Reply #11 on: January 04, 2012, 05:26:42 PM »

It took me longer than expected to get my cams installed. When I was removing my cam shaft tensioners, the plastic guide bushings broke. I had to wait a week to get new guide bushings from Amazon since there is no official replacement part. Then I snapped a bolt in my viscous cooling fan mounting bracket. The bolt was mounted behind the pulley on the bracket, so there was no official way to replace the bolt. I ended up drilling an access hole through the pulley so I could replace the bolt.

Then after getting the engine back together, I got side tracked installing my lower bumper RS4 grill mesh and my meth injection kit. Car is all back together now and is running great. I don't have any before and after logs for how the cams perform, but the car doesn't "feel" any different.

PSA: When installing the cam shafts, one engine bank has 16 chain rollers between cams, and the other bank has 14.5 chain rollers between cams. The official repair manual only has information on how to replace the cams on one bank of the engine, and so only state that you need 16 rollers between cams.
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« Reply #12 on: August 23, 2012, 03:41:58 PM »

So Have you made any new logs or dyno'd this swap yet?
I've been researching Camshafts vs stroking, and I'm leaning towards more head work and ultralight porting.
« Last Edit: August 23, 2012, 03:44:51 PM by johnjohn » Logged
ta79pr
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« Reply #13 on: August 23, 2012, 04:38:43 PM »

The bolt was mounted behind the pulley on the bracket, so there was no official way to replace the bolt. I ended up drilling an access hole through the pulley so I could replace the bolt.

Does one need to drill another hole in the pulley symmetrically so that it remains balanced?
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Jason
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« Reply #14 on: August 23, 2012, 05:20:01 PM »

No, it won't cause any balance issues.  I have 2 of those stupid brackets lying around if anybody ever needs one.  EFK + PWM for the win Smiley

Also, when I recently did cams I didn't run into the 16/14.6 tooth issue.  The one head did have the notches offset, but you count to the next nearest notch and it equals 16.

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