7A Exhaust Cam

[S2central.net]

Good man - I like some evidence - especially on something like this where I haven't tried anything for myself. I'll go have a look at that sticky thread.

[Jamo]

According to Mihnea Paul in previous posts, the 7A exhaust losses some low end torque but that it can be mapped back in.

Also running a 7A exhaust will lean out the AFR at high revs if not mapped for it.

The 7A inlet changes the car a hell of a lot less torquey and moves boost higher up the rpm.

Mihnea corrected me on this when I thought it wasn't different and having a car with a 7A inlet I agree.

I made this thread a sticky about a month ago with Doug's RR plots

http://www.s2forum.com/forum/showthread.php?t=10461

[S2central.net]

IIUC - it is the 7A inlet cam which changes the engine characteristic a little in that the engine doesn't generate as much torque in the low-mid range with the 7A IN cam - compared to stock 3B, ABY, AAN.

In saying all of this, I am due for a new timing belt and some new top side gaskets anytime soon - for a little extra effort I guess I could drop in my 7A EX cam to try it out on an otherwise stock engine - with the exception of homefried ECU of course.

Paul

[Audi_CQ]

but there's no real benefit on a normal homefry....or is there? When I raised this a while back it seemed that I'd lose on the low end stuff. Be interested to see by how much though

7A Ex cam has same timing as stock cam so OK to fit to stock / homefry without loosing low end power. If there are any gains I don't know for sure because the small turbo is such a restriction that the turbo is the weakest link and not the cam.

[Azman]

I have both in and the car is bit revvy to be honest, not the best for normal driving but I live with it due to when you hit a certain RPM (about 3500) the car just pulls and pulls all the way to 7K rpm....

[s2driveruk]

but there's no real benefit on a normal homefry....or is there? When I raised this a while back it seemed that I'd lose on the low end stuff. Be interested to see by how much though

[S2central.net]

Two dot alignment as per the norm - yes.

I've not seen any dyno plots for a stock 3B running the 7A EX camshaft but I'd be really interested in seeing the results if you get it on the rollers as the larger lift on that cam means you should be breathing better - pushing and pulling more air thru the engine.

[20Vcqdriver]

I will be swapping my 7A engine for a 3B in the coming winter months, and having read various threads it appears it is worthwhile swapping the 7A exhaust into the 3B. Questions that have not been answered on here are a) Will just changing the exhaust cam have any effect on an otherwise standard engine, if so what? b) Is the 7A cam set up in the head as per the 7A i.e. 2 dots aligned together with top face of head. Thanks.

[layuca]

I need help identifying a turbo I bought a few years back, and your thoughts on whether it makes sense to install in my car.

The turbo has a K26 compressor housing part no. 5236 970 6411. The center section has the following numbers on it (though not 100% sure) 552-?-2699 035149585A.

The compressor wheel is as follows:
16 blades
exducer .75
inducer .51

compressor outlet is .45
compressor inlet is .53
exhaust outlet is .61
exhaust inlet is .61

I was told that the compressor wheel is off a k27, but I don't know if it's true.

I have a K26 in my car and have been considering replacing it with this one. The k26 that I have in my car has a much smaller hot side. I believe the compressor housings are the same, but the compressor wheel on the one I have in my car does not have as many blades.

The inlet of the exhaust was worked on to smooth out the lip into the turbo, which I hope does not affect the integrity of the turbo.

While I would like to replace my k26 with this other turbo, I don't want to end up with more lag than what I now have.

Your thoughts on this will be greatly appreciated. Thanks...

[Audi_CQ]

Hi Roger,

did you use them with the tioming on the marks as is, or did you changed something?

Because of different block height the timing was ~5 degrees advanced with stock cam pulley. Changed to mech cams before testing with an adjustable pulley

[Albert]

I will make my self more clear. Shoul I use Inteke cam form 3B and exhout form 7A or use both 7A cams ?

[Faheemo]

Use just the 7A exhaust and if u havent got the turbo as yet take a turbine with .86 AR the .63 AR is a bit too violent when boost comes in, and i assure you that the 7a and .86 AR will make a good match in the upper revs.
I got plenty logs and data.

[Albert]

If I want the power to come early and the output to be ~ 450HP (GT3071R) should I use both cams or just exhoust from 7A ?

[Billman]

Hi Roger,

did you use them with the tioming on the marks as is, or did you changed something?

[Audi_CQ]

Is anything on the assumption that with both the 7A there is more danger for the exhaust valves? What about the drivetrain stress?

Is anyone running both 7A on a stroker?

cheers,

Vasilis

There is no more danger for the exhaust valves.
More power = more stress, but the cams alone doesn't make much power increase on a std motor so driveline stress isn't an issue before other mods are done.

I've used both 7A cams in a good ported head on a stroker. Works great

Cheers,
Roger