7A Exhaust cam, what does it do?

[newsh]

I fitted the 7A Exhaust cam to my car expecting to get a bit better breathing up the top end, I'd read that fitting both cams might lose me some low end so just went for the Ex cam.
What I think I'm noticing is that the car actually doesn't pull so well up the top in the high gears, boost is starting to drop off above 4k and the engine seems to go a bit flat above about 5k, I'm actually tempted to put the 3B Ex cam back in as I seem to remember that the car used to just keep on pulling past 5 in top, it used to just drive up to the top end of the speedo..(The old speedo though, the plasma speedo goes up to 180..) Obviously its difficult to test this without going to an autobahn..
Problem is I havent got any actual figures to compare, does anyone else have any experience of this?

[s2dude]

I fitted the 7A Exhaust cam to my car expecting to get a bit better breathing up the top end, I'd read that fitting both cams might lose me some low end so just went for the Ex cam.
What I think I'm noticing is that the car actually doesn't pull so well up the top in the high gears, boost is starting to drop off above 4k and the engine seems to go a bit flat above about 5k, I'm actually tempted to put the 3B Ex cam back in as I seem to remember that the car used to just keep on pulling past 5 in top, it used to just drive up to the top end of the speedo..(The old speedo though, the plasma speedo goes up to 180..) Obviously its difficult to test this without going to an autobahn..
Problem is I havent got any actual figures to compare, does anyone else have any experience of this?

Sounds interesting Newsh. I've no experience of 7a cams but look forward to your findings
Does the car need mapping to make the most of this swap I wonder?

[newsh]

Car has been mapped since the cam swap.

[zlobo]

with wich turbo? and em?? i think you need atleast an rs2 turbo and em to see the difrence.

[Jamo]

with wich turbo? and em?? i think you need atleast an rs2 turbo and em to see the difrence.

Newsh hasn't got a standard turbo. He had an Rs2 and then a garret 30 IIRC

[Chris M]

Car has been mapped since the cam swap.

Thats interesting The exhaust cam should be opening the exhaust valves open for slightly longer or further open allowing the better removal of gasses from the cylinders, also helping the turbo spool up quicker. Can't see how it would have an adverse effect, unless it was out by tooth on the chain?

Cheers

[Jamo]

Ditto Chirs, But it would be interesting to see what the AFR is at the higher levels on the car at that point.

with the 7A cams both in bhp ( just!) increases but the power delivery profiles changes and most dont seem to like the change.

IIRC Doug did this but changed back, but there are other forum members running 7A cams.

I have a 7A inlet RS2 exhaust on mine.

[Audi_CQ]

Thats interesting The exhaust cam should be opening the exhaust valves open for slightly longer or further open allowing the better removal of gasses from the cylinders, also helping the turbo spool up quicker. Can't see how it would have an adverse effect, unless it was out by tooth on the chain?

Cheers

The 7A ex cam doesn't open the valves longer. It got the same timing as std cam, but has more valve lift. Shouldn't have any bad effects if timed right

[Chris M]

valves open for slightly longer or further open

Wasn't 100% sure valve timing was the same, hence my post.

I know the 7A inlet is a bit 'peaky' for some when used with 7A exhaust. Maybe best putting the stock cam back in.

Cheers,

[newsh]

Thanks very much for the replies chaps! The car is running an RS2 turbo and EM. I'm still thinking about the GT though..

It may be that I'm being fooled by the hefty midrange grunt between 3 and 4k into thinking the top end isn't there.. I'll try to get some figures of what boost I'm getting at what RPM. I'll also double check the timing marks. Looking at the 2 cams I'd have said the 3B cam has more duration and the 7A cam more lift.

I'm also aware that Mihnea has told me that the top end is now being restricted by my stock downpipe.

Also I STILL haven't fitted the catch tank, doh!

[Jamo]

The 7A ex cam doesn't open the valves longer. It got the same timing as std cam, but has more valve lift. Shouldn't have any bad effects if timed right

It's timing is different to the turbo cam as it has more potential overlap so how are the valves not open longer?

[newsh]

I seem to remember someone posting the timing data on all the available 5 cyl cams quite a long time ago and none of them actually had any overlap, I think it was Pisobiker? Overlap is not considered a good thing on a turbo motor as the fuel ends up getting blown out the exhaust.

[Jamo]

I seem to remember someone posting the timing data on all the available 5 cyl cams quite a long time ago and none of them actually had any overlap, I think it was Pisobiker? Overlap is not considered a good thing on a turbo motor as the fuel ends up getting blown out the exhaust.

Pisoboker and 4wheeldrifter posted them there was more duration on the 7A

[Audi_CQ]

Pisoboker and 4wheeldrifter posted them there was more duration on the 7A

Only 7A inlet has more duration. If you're using both 7A cams you get more overlap.

http://not2fast.wryday.com/audi/info/20_cams_1.xls

http://www.s2forum.com/forum/showthread.php?p=54107

[jogi730]

Only 7A inlet has more duration. If you're using both 7A cams you get more overlap.

http://not2fast.wryday.com/audi/info/20_cams_1.xls

http://www.s2forum.com/forum/showthread.php?p=54107

What are the different profiles on the various cams as a matter of interest - is this information available somewhere?
Cheers
Chris