7A Exhaust Cam

[spink]

I have another pair of 7a cams(70,000 miles) for sale if anyone is interested.Can be collected in yorkshire or south london(next monday)

[Mark Halligan]

Spink, you have mail.

Mark.

[Doug_RS2]

Originally posted by Mihnea
On a real K26 @8 it is 56mm or thereabouts, Doug, what about measuring it so we know once and for all BTW???

FWIW, an RS2 K26 #6 exducer bore is 54mm.

I'll measure it tomorrow.

[Doug_RS2]

Originally posted by Mihnea
On a real K26 @8 it is 56mm or thereabouts, Doug, what about measuring it so we know once and for all BTW???

56mm

This is the inlet diameter to the hot side(the bit that bolts to the manifold ( is that what you wanted measuring? )

[auditude]

I would like to point out some aspects about 3B/ABY/AAN vs. ADU vs. 7A cams:

analizing data I have there are some in my opinion interesting things to consider when choosing among different cam's options:<snip>

Marco/anyone,

How about some analysis of the different 20vt cams offered by CATCAMS? This is from their webpage. I'm particularly curious which would be best for a 2.5l stroker. I know that Audi_CQ on here is using the 266° version on his 2.5l stroker with good results. Unless there's a reason to pick a different grind, I'll try to go that way (assuming I can afford them).

From: Cat Cams Website:

manufacturer:    V.A.G.
cam layout:      DOHC
engine layout:   5cyl - L
follower type:   DTH (Direct Tappet Hydraulic)
valves [in/ex]:  4v [2/2]
rotation:        cw

car model     capacity   engine code   from     until

audi 80,100,  2226cc     RR,3B,AAN,    09/1990  1996
coupé,A6,RS2             ABY,ADU
(all quattro)
 
audi 90,coupé 2308cc     7A            08/1988   09/1991
(all quattro)
     
partnr.  duration  duration  maximum lift   lift at TDC  parts   application
         [0.1mm+cl][1.0mm+cl][cl=0]         [cl=0]       [-]     [-]

1002331  242/258°  211/223°  9.65/10.00mm   0.40/0.95mm  O.E.M.  HYDR: sport
1002303  266/266°  226/226°  11.20/11.20mm  1.10/1.10mm  O.E.M.  HYDR: sport
1002305  279/275°  242/238°  11.50/11.45mm  2.30/2.05mm  O.E.M.  HYDR: rally & cross
1002422  284/284°  234/234°  10.90/10.90mm  1.55/1.75mm  custom  MECH: rally & cross
1002423  270/270°  241/241°  12.00/12.00mm  2.65/2.60mm  custom  MECH: rally & cross
1002426  282/278°  254/250°  13.20/12.55mm  3.75/3.30mm  custom  MECH: rally & race
1002424  301/288°  267/255°  12.70/12.15mm  4.40/3.50mm  custom  MECH: rally & race
1002427  288/280°  261/253°  13.95/13.20mm  4.70/4.05mm  custom  MECH: rally & race

[Sweeper]

Marco : Simple question

What benefits of 7A exhaust cam on 3B engine with RS2 turbo,manifold,injectors,fuel pump and remap(Some 360HP?). Will I see any benefit of installing 7A exhaust cam on such configuration ? On which revs ?

Thanks in advance.

[audiman]

You will gain some top end power. Its not a lot, but every little helps. Im usng both 7A cams in my 3B. The more air the engine flows the better.

[Sweeper]

Tom: Is it safe to run just exhaust 7A cam ? Or should I put both ?

P.S. I do have access to both of them.

[audiman]

Its safe to use just the exhaust one, but IMO its best to fit both. It doesnt make idle lumpy or anything. Increased valve lift from ~8.6mm to ~11.5mm with 7a cams.

[auditude]

Tom: Is it safe to run just exhaust 7A cam ? Or should I put both ?

P.S. I do have access to both of them.

I'm not Tom, but... The only thing I've heard is to make sure you at least have an RS2 EM or better. The 7A exhaust cam supposedly has longer duration so there is more of a chance of burning valves over the stock cam, so getting the gases out (evenly/equally) is more critical. This is what I recall from the Kruemmer list discussions.

I think most people just run the 7A exhaust cam with whatever turbo intake cam their car normally has, just like most use factory-type upgrade paths use the RS2 exhaust cam only. It's supposed to be a cheaper, more easily obtainable, and more aggressive upgrade than the RS2 exhaust cam. Once again this is all just reading online, not from personal experience.

[audiman]

I think Vadim is using RS2 manifold as he is after at least 360bhp, thats why i said yes. But that Kreummer site, has loads of info about cams and loads of other projects. Check it out Vadim, you may find your answer in that site

[Pisobiker]

Yeah, as Tom says, more aggressive cams (more lift and more duration) will give some gains in the mid to high rpm.
Problem with cam comparison is I don't have an important data for comparing them:

real opening area which is the number that effectively says how much charge can be driven in the cylinder:

There is no gain in having 2mm more lift if, for example, opening of the higher lift cam is slower. In this case total area might even be the same for both with an advantage for the lower lift one, having more "mid opening area" (which is the most effective for flow). On the other hand a "steep" cam will put more stress on lobes, followers and springs so there is a safe limit on how quickly a cam can open valves.

Only data I have so far:

- as for duration 7A and the 266° Cat cams are similar (224°/213° Ex/In for the 7A; 226°/226° Ex/In for the Cat cams, both @ 1.0mm +cl) while the Cat cams has 11.2mm max lift on both Ex/In and 7A has 10.5mm (exhaust. I don't have lift for the intake).
- 3B-ABY-ADU have 22° less intake duration than the 7A one while on the exhaust 3b-ABY have same duration as 7A. ADU has 8° less exhaust duration but 9.5mm lift vs. 8.6.

NM camshafts seem midway between ADU and 7A but profile seemed to me less steep than the ADU cams, so, not having the equipment to check effective opening area, I will stay with the latter ones.

Of course another important thing will be the timing. You can play with it advancing and retarding a bit, accordingly with where you want max VE in the rpm.


Marco

[auditude]

I think Vadim is using RS2 manifold as he is after at least 360bhp, thats why i said yes. But that Kreummer site, has loads of info about cams and loads of other projects. Check it out Vadim, you may find your answer in that site

Oh I'm sure Vadim is at least running that; a guy who sells RS2 and SQ EM's left and right had better be running something better than stock on his own car! I was including that info for others.

(Also, I was typing my reply before I saw yours posted, so I wasn't trying to rebut or anything. )

[audiman]

LOL, thats cool. Cheers for that Marco.

[Sweeper]

Audituda: You are too kind :-). I guess I have too much link in this field. Need to open a shop maybe.