7A cams

[Audi_CQ]

@ Mark H. and anybody who might be interested,

Exhaust Cam

I already sayd in another thread 7A exhaust cam looks significantly more "high performance" minded than 3B/ABY/AAN and also of the ADU one.
And this couldn't be different because it cames off a NA engine wich needs much more "aggressive" timing for best possible VE.
Gains of using the 7A ex-cam on the turbocharged engine (knowing there still is no overlap, which we don't want on a forced induction engine) will probably be percentually less than the worstening of using the turbo cam on the NA engine, but it should anyway give some good gain in the mid to high rpm.


Intake Cam

Compared to the turbocharged ones:

Given I don't have lift among the other parameters (which might make some rilevant difference), timing is as follows (always according to data I have)

7A: opens 6° before TDC; closes 38° after BDC; duration = 224°

3B/ABY/AAN: opens 3° after TDC; closes 25° after BDC; duration = 202°

ADU: opens 13° after TDC; closes 35° after BDC; duration = 202°


1) All three of them (coupled with 7A exhaust cam) won't give overlap:

7A = -3°
3B/ABY/AAN = -12°
ADU = -22°

2) ADU one seems to me will give too much delay on intake valve opening;

3) 7A gives sensibly longer duration (while being a little "at the limit" with overlap) therefore giving higher flow gains (thus VE) expecially on high rpm.

"Reading" the timing from a theoretical point of view, since the use of the 7A exhaust cam already pushes VE optimization to higher rpm (together with rising stresses of valvetrain with higher lift) I would personally chose both intake and exhaust 7A cams.
Alternatively I think the 3B/ABY/AAN intake cam would be even better then the ADU one.

As I sayd many times, though, things on real life might change a bit, maybe due to not considering some other parameter right now.
So if anybody has something to say about this and/or has infos and feedback on weather using one option better than another and why, pleas tell.

Marco

Old thread, but some new info about 7A cams:

Have anyone tried to measure the actual lift and duration of the 7A cams? Everyone seems to take for granted that the quoted numbers in manuals are right, but are they

I've just fitted some 7A cams(nr. 054 xxx xxx) to my 2.5 and when checking cam data I was in for a surprise. The 7A intake cam isn't as agressive as people think. This is the measured data at 1mm lift:

Exhaust:
opens 45° before BDC; closes 7° before TDC; duration = 218°
Lift ~10.5mm
(Manual says 42° before BDC; closes 3° before TDC; duration = 219°. Looks like my cams are ~3° advanced. Not stock engine so..... )


Intake:
opens 4° AFTER TDC ; closes 35° after BDC; duration = 211°
Lift ~9,6mm
(Manual says opens 6° BEFORE TDC; closes 38° after BDC; duration = 224° )


Is it possible that the 6° before TDC quoted for the 7A intake cam is a typing error and should actually be 6° after TDC? If so, it's like a NM-cam but 6° retarded.

Cheers,
Roger

[Josh-stateside]

I've been confused about this stuff too.

Bently manual states:

intake valve opens before TDC 6
intake valve closes after BDC 38
Exhaust valve opens before BDC 42
Exhaust valve closes before TDC 3

valve timing is at 1mm valve lift and zero clearance?

The majority of naturally aspirated audi engines that I saw text for cams stated that the intake valve opens "after" TDC.

[Josh-stateside]

Old thread, but some new info about 7A cams:

Have anyone tried to measure the actual lift and duration of the 7A cams? Everyone seems to take for granted that the quoted numbers in manuals are right, but are they

I've just fitted some 7A cams(nr. 054 xxx xxx) to my 2.5 and when checking cam data I was in for a surprise. The 7A intake cam isn't as agressive as people think. This is the measured data at 1mm lift:

Exhaust:
opens 45° before BDC; closes 7° before TDC; duration = 218°
Lift ~10.5mm
(Manual says 42° before BDC; closes 3° before TDC; duration = 219°. Looks like my cams are ~3° advanced. Not stock engine so..... )


Intake:
opens 4° AFTER TDC ; closes 35° after BDC; duration = 211°
Lift ~9,6mm
(Manual says opens 6° BEFORE TDC; closes 38° after BDC; duration = 224° )


Is it possible that the 6° before TDC quoted for the 7A intake cam is a typing error and should actually be 6° after TDC? If so, it's like a NM-cam but 6° retarded.

Cheers,
Roger

How are you measuring this btw? Is the engine in the car and have you had any head work like milling the block or head?

From what I read that can cause changes with valve timing.

[Josh-stateside]

Online computer calculations:


Your 7a has an Overlap of 3.00 degrees and has in Intake Duration of 224.00 degrees. The Exhaust Duration is 219.00 degrees. The Inlet Cam has an Installed Centerline of 106.00 degrees ATDC. The exhaust cam has an Installed Centerline of 112.50 degrees BTDC.

Online calculator gave me those results for the 7a cams via the bently manual spec.


Take particular notice to the importance of (-) negative #s.

6
38
42
-3

are the #s you want to enter into the calculator for the 7a cams.

Rs2 cams:

Your rs2 has an Overlap of -12.00 degrees and has in Intake Duration of 202.00 degrees. The Exhaust Duration is 205.00 degrees. The Inlet Cam has an Installed Centerline of 114.00 degrees ATDC. The exhaust cam has an Installed Centerline of 101.50 degrees BTDC

#s to plug in:

-13
35
24
1

http://www.actionspeedparts.com/calc2.html

[Josh-stateside]

look what I found :-)

http://webplaza.pt.lu/~kinnenma/adu1.htm

ADU:
@1mm ventilhub & ventilspiel 0mm
IN open OT:n after 13 Grad
IN close UT:n after 35 Grad
EX open before UT 24 Grad
EX close OT AFTER 1 Grad
EX max hub 9.5mm

AAN & 3B:
IN open TDC OT:n after 3 Grad
IN close BDC UT:n after 25 Grad
EX open before BDC UT 42 Grad
EX close BEFORE TDC OT 9 Grad
EX max hub 8.6mm

NM:
IN open TDC OT:n after 0°
IN open BDC UT:n after 32°
EX open before BDC UT 35°
EX close before TDC OT 3°
EX max hub 9.6mm

7A:
IN open before TDC OT:n 6°
IN close BDC UT:n after 38°
EX open before BDC UT 42°
EX close before TDC OT 9°
EX max hub 10.5mm

[Josh-stateside]

Before I go to bed I wanted to make one comment.

Even if the 7a cams have overlap it's not as bad as one thinks?

The C0s in the exhaust should actually help to cool the cylinder chamber down and help prevent knock.

Am I correct with saying this? It's a mild form of water injections to some degree.


ttyl
josh

[Audi_CQ]

How are you measuring this btw? Is the engine in the car and have you had any head work like milling the block or head?

From what I read that can cause changes with valve timing.

Measured with a "degree-wheel and verniergauge" (right words?). I have "custom everything " so no surprise that cams where a bit off, but that intake cam had much less duration then quoted in manuals and so on, was not expected.

Cheers,
Roger

[Audi_CQ]

look what I found :-)

http://webplaza.pt.lu/~kinnenma/adu1.htm

7A:
IN open before TDC OT:n 6°
IN close BDC UT:n after 38°
EX open before BDC UT 42°
EX close before TDC OT 9°
EX max hub 10.5mm

Yepp that's what the text says, but when I measure myself I get different numbers

[AAH!]

Figures aside and just to confirm what I understand does this all mean that 7a cams give you less bottom end torque but more top end?

Are there any other benifits over ADU cams.

My cams are supposedly of Dialynx's own design (fitted about 7 years ago), but I have no details and Dialynx have not being too forthcoming about the actual spec, they just say "they are performance cams that make the power more progressive". The cams have an audi stamp on them but they might have been remachined by dialynx(?) or they could just be straight 7a cams. It would be nice to know.

[Jamo]

Figures aside and just to confirm what I understand does this all mean that 7a cams give you less bottom end torque but more top end?

Are there any other benifits over ADU cams.

My cams are supposedly of Dialynx's own design (fitted about 7 years ago), but I have no details and Dialynx have not being too forthcoming about the actual spec, they just say "they are performance cams that make the power more progressive". The cams have an audi stamp on them but they might have been remachined by dialynx(?) or they could just be straight 7a cams. It would be nice to know.

I bet they're 7A cams!

[dan_b]

I bet they are too

[slow2]

TOP posting guy's

I have been scratching my head over these points for months

[jon]

lobe height on 7a ex cam ??

[Jensk]

Before I go to bed I wanted to make one comment.

Even if the 7a cams have overlap it's not as bad as one thinks?

The C0s in the exhaust should actually help to cool the cylinder chamber down and help prevent knock.

Am I correct with saying this? It's a mild form of water injections to some degree.


ttyl
josh

Old thread, i know.. but anyway;
leakage of exhaust from one cylinder to another in that way would use up cylinder volume otherwize filled with a fresh charge of air/fuel and thus reducing the volumetric efficiency of the engine. If the exhaust was to cool down the cylinder, it probably wouldnt be enough to counter the loss of fresh charge. And anyway, a hotter cylinder burns fuel better than a cold one. And less energy wasted heating it.