7A Exhaust Cam

[M_GORDON]

Thanks Rocco and RWD19T

Well, I can put the DB camgear with my mods. and advance or retard, not?

[JP]

Further to my previous post there are some generalizations you can make when timing cams providing you hit their sweet spot in relation to the crank.

Leave exhaust alone and advance intake = more torque and power drops of sooner
Leave exhaust alone and retard intake = less torque but more hp in the top rpm band
Advance both intake and exhaust = power comes in sooner and drops of sooner (not necessarily more though)
Retard both intake and exhaust = power comes in later and has a higher peak rpm (not necessarily more power though)

[JP]

The effect of altering cam timing varies depending on the rest of the engine spec. With regards to stroke, desired rpm band, turbo and headflow.

My original 7A combo on paper redlined at around 7500rpm which it did at 1.7Bar of boost. Once I turned the boost upto 2 bar this peak power came down to around 6900rpm as the hotside of the turbo (0.63) was too small to support the extra exhaust gasses. But same cam profile.

Very smooth power delivery, real nice on the track but missing midrange grunt for the road. So after numerous calculations on an engine simulator I advanced the intake cam only (left the exhaust alone) by 7 degrees. Result in difference in power delivery is attached.

Now by advancing the intake cam the redline changed from 7500rpm to 6800rpm on 1.7bar of boost but on 2bar it made no difference to the original non advanced intake profile as you can see from the attached.

I've sorted the voltage out on the fuel pump to ensure no more lean spikes, fitted a .82 housing and a vernier on the cambelt and once Mihnea is in town I will have a little play on the dyno. My suspicions are the whole setup will need to be retarded by a couple of degrees to make more low, mid and top end. As by advancing and retarding the whole cam combo doesn't necessarily shift the same shape power curve on a turbo car the way it does on an NA like I have found in the past.

[Rocco]

Hello boyz.
I have ABY cams, water pump and fpr with ADU turbo, EM, inyectors, IC and Paul remap.
And I have to put a DB camgear.
Do U think I must put/instal the camgear only? A 7A Ex cam only? both?
I don´t know who do.

Or sell the DB camgear?

I don´t want remap to runs ok with those mods, only know who make.
Thanks and excuse me if U don´t understand me correctly.

Gordon you are wanting to say Dhalback cam pulley not cam gear true??

with your ABY cams you could install alone them with Dhalbacl regulable cam pulley and ad some advance or retard degrees in it. the same as if you decide to install it with ABY intake cam and 7A exhaust cam. i dont know how it is better anyway

[M_GORDON]

Hello boyz.
I have ABY cams, water pump and fpr with ADU turbo, EM, inyectors, IC and Paul remap.
And I have to put a DB camgear.
Do U think I must put/instal the camgear only? A 7A Ex cam only? both?
I don´t know who do.

Or sell the DB camgear?

I don´t want remap to runs ok with those mods, only know who make.
Thanks and excuse me if U don´t understand me correctly.

[rash]

I agree, but I am before testing... and so I have to do some therorie first

and I´m not gonna do some dyno... I only use Logging Tools to measure acceleration times and boost behaviour compared to rpm and TPS... for my purpose enough

[Ola]

I havent written a word about degrees, and cam profiles.. For a reason.

I am after experience where 1 car with the same setup, changes cams or cam timing, to see the difference..
The info i`ve got so far about the 7a intake cam, is telling me stock timing works the best, and that it`s most likely is a total waste to innstall, compared to a stock intake cam.

This is based on dynocharts i`ve seen posted, both here on s2forum and other places..
Therefor i`ve gone from "timing of 7a" to "what cam`s to choose" now

If anyone got something that claim me wrong, i am very interested in you`re experience. But i`m not interested in teories with no dynocharts (or similar) to back it up. If we are just talking degrees in teori, we could talk about it for 10 years and still not have a clue.

And btw, i AM going to adjust my cams in the dyno. Separately. I just want the most info i can get, before choosing cam`s.
I might even bring several cams to the dyno. But every hour in the dyno costs alot of money, whitch i dont mind saving with a little research.

Ps: Audi_CQ did read the 7a`s EXACT measurments once. He has written them on this board somewhere. But it`s still irrelevant for my research for experience..

[rash]

If someone knows better, please tell. But dont guess.. (not ment "rude" in any way`s).

let me explain a little bit...

i was reading in several forums and on many websites manuals and books for hours and days - to find out what is really up about the timing of the 7A inlet cam...

...there are 2 different data to find for inlet open in the web: 6deg before OT and 6 deg after OT..

...and many times you read about the overlap (6deg bef. )... but ist that a rumor?? depending on an mistake in some old documentaries?

the more you read the less you know :-(

by comparing many timing Data of Audi Camshafts in 2.7T, 2,2 20VT, 2.2 20V, 1,8T, 2.8 30V etc... i know, that there are no camshafts with overlap in these cars - only when the use systems to adjust the inlet (RS4 2.7) camshaft timing automatically, there is overlap in lo-mid range to reduce pollution (internal exhaust backflow)(sorry i dont know the english word)

...i found an old posting of somebody who had direct access to Audi blueprints of the 7A camshafts an he said 6deg after OT

...i found also an old posting of somebody who had data from electronic repair manual an he said 6deg before OT

so in this special case and after all these "fakts" i can only "guess" or belive that 6deg after OT sounds to be real... know i have to test...


...I agree with you - but in this case it seems to be hopeless to find hard fakts about the 7A inlet cam because 100 people posted 100 different data...


...but it is a fakt, that retarding the Inlet close will increase the mid range Power cause this is the way RS4 2.7 and 1.8T do it for this purpose...

...by retarding the inlet close you prevent that the upmoving piston presses back out the mixture trough the still open inlet valve - because there is no boost pressure in mid range...

PS

Im talking about 500HP + Engines with big turbos

sorry about my bad english

[GazzaG60]

after reading a lot i dont think there is a hard and fast rule. its all dependent on setup.

i have

sc61 turbo, tubular header, wagner inlet and IC, stock head, skimmed pistons.

with the aby cams the car felt to pull harder and on boost produce more torque. it felt snappy. i could feel it tightening up over say 6000-6300 at 1.3bar or so.

i fitted the 7a ex cam and found it to be flat low down and take longer to produce the snappy feel. in fact it didn't really until i lifted boost over 1.5bar. it feels a little lazy coming on but over say 5500 it feels better than the aby cam.

this is all standard timing. i feel that smaller turbo's dont benifit from it as they are dropping away by 5500 and the standard aby cams hold that great. you need a turbo that will hold to 7k to benifit at all. general road use and its worse than standard cams, on boost higher up, bearing in mind i dont see boost proper till 4000-4500 the 7a works.

i cant give dyno figures other than standard cams 1.3bar 321hp/325lbs ft at 5k. fueling poor over that. maxing standard injectors.

[Jamo]

Several people seem to have had problems with the quality of DB cam pulleys mate - specifically the keyway IIRC. Have a search on here

Several? I know of about 7-8 people including DJones, AndersS2 running these without issues

[Jamo]

Exhaust, yes.. Intake? hmm.. After alot of dyno reading on 7a intake cam vs stock, i cant see any gains at all.. Perhaps 1-4hp, with alot of midrange loss..

I dont see any reason for running 7a intake cam, on a 450-600hp I5 right now..

Most people are running 7a cams on std timing (or 5`adv on ex for better spool), claiming this is _the_ best setting, after dynotesting them.. Talking about people with dyno experience, not guess-timaters..

If someone knows better, please tell. But dont guess.. (not ment "rude" in any way`s).

I dont want to loose midrange/spool, and really dont care about 5hp extra on top. So i dont want the 7a intake cam, before anyone has great experience`s in timing these alot better than stock..

Even "Mineah" stated in a post here at S2forum from 05`, that a 3b intake was a better choice than a 7a intake, based on dyno results.. Thats over 4 years ago though, so for all i know, he has changed his opinion on the subject again?

http://www.s2forum.com/forum/showpos...79&postcount=5

That must be an old post, as it was Doug at MRC who did the post on his S2 that the car pulled harder with both 7a inlet and 7a exhaust but with more lag.

It's a sticky thread on the forum

[Error404]

Several people seem to have had problems with the quality of DB cam pulleys mate - specifically the keyway IIRC. Have a search on here

[Rocco]

me for example i am using 3B intake with 7A exhaust....and i am "happy",aniway i dont have any dyno result for compare with for example both 3B cams or both 7A cams.

Guys....do you know if Dhalback Racing has for sale a Regulable Cam wheel for 3B engines with the hall sensor in the distributor of course

[Ola]

7A gains are high up the rev range and they make the car pull harder in acceleration from mid to high.

Exhaust, yes.. Intake? hmm.. After alot of dyno reading on 7a intake cam vs stock, i cant see any gains at all.. Perhaps 1-4hp, with alot of midrange loss..

I dont see any reason for running 7a intake cam, on a 450-600hp I5 right now..

Most people are running 7a cams on std timing (or 5`adv on ex for better spool), claiming this is _the_ best setting, after dynotesting them.. Talking about people with dyno experience, not guess-timaters..

If someone knows better, please tell. But dont guess.. (not ment "rude" in any way`s).

I dont want to loose midrange/spool, and really dont care about 5hp extra on top. So i dont want the 7a intake cam, before anyone has great experience`s in timing these alot better than stock..

Even "Mineah" stated in a post here at S2forum from 05`, that a 3b intake was a better choice than a 7a intake, based on dyno results.. Thats over 4 years ago though, so for all i know, he has changed his opinion on the subject again?

http://www.s2forum.com/forum/showpost.php?p=110479&postcount=5

[Ola]

Sorry, advanced of course..

retard?? i remember he sait 5 deg advance...


I also guess the 7A inlet cam is the same as the NM inlet but the NM is 4deg advanced

--> NM 2° nOT to 34° nUT
--> 7A 6° nOT to 38° nUT

I will try so set the 7A cams both 5 deg advanced

7A ex from original 42deg before UT and 3deg before OT to 47deg before UT and 8deg before OT

7A in from original 6deg after OT and 38deg after UT to 1deg after OT and 33deg after UT