7A Exhaust Cam

[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.

[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)

[M_GORDON]

Thanks Rocco and RWD19T

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

[Nik0las]

What about 7A vs NM cams?

[Audi-Porsche Avant RS2]

Hello friends, what do you think about this head and engine setup with a K24/7000 or 7200 hybrid or SMS turbo?
Can I have some benefits or not and is possible that I have problems with correct setup of the engine?

Head setup:

- Lightweight lifters
- Titanium retainers
- Hi-rate valve springs
- 3rd angle valve seats with swirl polished valves
- Intake and exhaust ported and polished
- New valve guides and Viton stem seals
- 7A exhaust cam ABY inlet cam

Engine setup

- Pauter rods
- Je pistons
- 3B flywheel
- Original crank or what?

Thanks!
Alessio

[A80Avant]

Alessio,
you have posted this 3 times already. Rather than that, just read through 'search' on all those things that you are asking. they have been covered numerous times and that is why you are not getting a straight answer now.

[Audi-Porsche Avant RS2]

I think that with my setup there isn't another one, I have search before post and I have not find anything because normally 7A exhaust cam is used for over 500 hp not for range from 300 to 420-430 hp.
Alessio

[A80Avant]

a cam with different lift will always work on either setup. Depending on the setup you may gain a few more hp or not. Similarly if you have a larger turbo it will help. YOu wont get a straight answer from anyone unless there is one with excact same setup as yours. So all answers are going to be a best guess and nothing more. Whatever you think that might be true, it probably is, so no point in posting and reposting until you get an answer

[Rusty]

From what I have read rather than what I have actually done - RS2 cams + wheel for torque, ABY / 7A + correct timing for power.

[Audi-Porsche Avant RS2]

Interesting Rusty, what you mean for wheel? You mean adjustable cam pulley for example from Dahlback? Or flywheel?
Thanks!
Alessio

[Rusty]

Again, it's all covered on here... RS2 cam wheel changes the timing by 10deg. Adjustable wheels that work with the cam sensor are a rare thing.

If you're mixing and matching cams, then it's worth getting them setup properly to get the most out. I've recently been playing with my BMW cams and timing (it's all adjustable from the factory ) and have managed to get a setup that irons out some flat spots, as well as giving decent mid-range torque and 6k5 power. Overall, it was very much worth the effort, as it's much nicer to drive now.

[Faheemo]

I've been running the 7a exhaust cam with the aby inlet cam on my car with good results so far. This is a 600hp Engine.
I've been thinking about re profiling the 7a intake cam i have to have a similar duration of the ABY intake cam but with the advantage of the higher lift of the 7a.
This will keep the duration close to the original intake cam but with more lift. I'm not sure if the added lift will benefit the VE.
Has anyone done this ? , thoughts and opinions welcome.

[Jamo]

I've been running the 7a exhaust cam with the aby inlet cam on my car with good results so far. This is a 600hp Engine.
I've been thinking about re profiling the 7a intake cam i have to have a similar duration of the ABY intake cam but with the advantage of the higher lift of the 7a.
This will keep the duration close to the original intake cam but with more lift. I'm not sure if the added lift will benefit the VE.
Has anyone done this ? , thoughts and opinions welcome.

Did you perform this?

I'm investigating cams again as i'm thinking of changing to an ABY Inlet with NM exhaust for something a little more street friendly or maybe completely new cams?

No doubting the setup I requested from Repo kills it in mid and high but I want low to mid and transition rather than peak power

[Faheemo]

yep i have done it.
I'm not too certain what difference it did make, i did do back to back g tech runs , and the results are very close to each other, the modified cam did make more hp from say 5600 rpm till redline about 5-10kws, but the curve looks the same so hard to tell if it was an external factor or if it was the cam.

[ADP]

NM cams are great and cheap than ADU!Just retard the inlet cams with 6 degrees and..................................WELLCOME TO REALITY BABY!