NefMoto

Hi,
I would like to know if anyboby has experience with 2.8l natural espirated cylinder heads on a RS4 (2.7BT)?
many thanks in advance
Greg

You can change the cams, but I would not change the heads.
The 2.8L is a big port head on the intake and on the exhaust.
The S4 2.7TT head is a small port head on intake and exhaust.
The RS4 2.7TT head is a big port head on the intake, but small port on the exhaust.

The smaller ports on the exhaust prevent the exhaust gases from expanding too soon and better maintain their exhaust velocity.
This helps to increase spoolup.

So the question is about your application... how much power you are aiming for.
The intake port shape on the RS4 head is also different, and specially angled injectors are used in the intake manifold.

Hi prj,
I am struggling with a vehicle where the heads are changed. This Car has a Problem with too High exhaust gas temperatures. Even with series Production calibration. The temperature increases at n>4500rpm higher than 945deg. Then t3 limiter Becomes active. To make the Story short: all sensors and all actuators of this Engine are already changed. If you Want to decrease the T3 you have to go to very early timing (20deg earlier !!!). This is Not a prefered Way for me to go. Therefore i Would like to understand what is happening in this engine. My thinking was, that due to the missing thumble of the head, the combustion moves significant towards Outlet valve opens. This would explain a high temperature. But i do Not have an idea of the amount of combustion elongation due to missing thumble. And i heard voices saying that a change to N/A heads is never a problem. But to be honest i have doubts about that. But i have no experience regarding the change to these cylinder heads.... Does anybody have experience?
Many thanks in advance
Greg

Is your cam timing correct? Are you using naturally aspirated cams?

Yes, the Cam Timing is correct and double checked 4 times now. The Inlet Cam is natural aspirated, the exhaust is rs4. All valves (in and Out) are from rs4.
Therefore i slightly disagree regarding the valve diameters.

I have used 2.8 heads with NA intake and S4 exhaust cams. That's a good mod on an 2.7 engine.

Could it be that the Cam actuators do not work properly? How can i Check this in a relieable Way? Dies anybody habe experience with the Cam actuators?
Many thanks in advance

No, it's not. It's a bad idea all around on a k04 car.

Performance wise it might not be the best choice i think. But i am more focusing in the Existing Problem with too high T3 with series Production calibration....

Can somebody that knows this give a real answer:  At what HP or TQ level do the big ports actually matter?  Are we talking like greater than 5000 RPM with 25 psi or greater?
My 2.7t holds 21 psi to redline and supposedly this won't add any tangible hp.

Ddellanger i might not know about tuning the ECU, but when it comes to hardware I know my ABC's About 20 years long. I am not doubting you but I have done and been around a lot of builds. Having big ports 99.99999% are neutral (meaning don't lose power) If not making at least a little more power.
Big cams might hurt (meaning duration not lift) overlapping can be the issue.
Big ports with NA 2.8 intake cams do make power ;)

You will make some hp at high rpm and very high boost over 30psi. At 21psi just run 2.7 heads  with rs4 or 2.8NA intake cams.

RS4 cams = 2.4NA

:) thats what I said. But some people don't know that. They refer to them as RS4 cams.

You never did, I just clarified.

ok, let me ask another more finite question.

2.7t runs 23 psi from 4500-7000.    what's your guess on how much i'd see from:

2.8 n/a heads with 2.8 cams
rs4 intake manifold
rs4 / w8 tb
everything port matched

versus

2.7t heads 2.7t cams
2.7t intake manifold
2.7t tb

i'm trying to weigh doing the 2.8 head upgrade when i do my next timing belt or waiting until i build a motor.

are we talking 5hp?  or are we talking 35hp?
it will be tuned correctly (timing / fuel / etc).

Waste of time IMO.

perfect answer.  thank you!

http://www.audizine.com/forum/showthread.php/279637-TiAL-R650-Kit-Big-Ports-615whp-545wtq-Small-Ports-580whp-550wtq?highlight=2.8+cams

Looks like you're standing to gain ~35 HP. Not even close to worth IMO. Response and torque are pretty much spot on with each other.

You are taking things way out of context.
1. In that post RS4 heads are used, not 2.8 ones. This is not the same thing.
2. The car is running over 600whp. This is not something the OP is running. Much better to say that there was 5% difference.

prj, my original point was that, if you do a top end rebuild.. at least where i live, its absolutely cheaper to find a 50-60k set of V6 heads and just swap them on there in their entirety...

its very clear that "wasting money" on this isn't worth it, but there could be other reasons why somebody is fixing the cylinder head... in which case it might be worth it since the N/A parts are that much cheaper even with low miles...

esp if you get low mileage cam tensioners and lifters, in addition to the big ports, along with the repair...

Please elaborate as Im planning a set of 2.8 heads for my B5 S4 (N/A intake, S4 exhaust) in a few months.

Thanks,
Adrian
02 S4