2.8 heads on 2.7

[nevrenuf]

i found what i could but the jury still seems to be out on some of the details....everyone agrees that the 2.8 flows better but some think it flows too well for anything outside of a big turbo...from what i read, i would see the most benefit from swapping cams from the 2.8 into my 2.7 whereas swapping the complete head may actually hinder performance...from what i read, the smallest turbos that would see a benefit form the full head swap are tial 650s or similar...thoughts?????



my car is a stage 3...

[euroguy666]

i found what i could but the jury still seems to be out on some of the details....everyone agrees that the 2.8 flows better but some think it flows too well for anything outside of a big turbo...from what i read, i would see the most benefit from swapping cams from the 2.8 into my 2.7 whereas swapping the complete head may actually hinder performance...from what i read, the smallest turbos that would see a benefit form the full head swap are tial 650s or similar...thoughts?????



my car is a stage 3...

Single turbo!

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[nevrenuf]

^^^ are you saying that it's useless without going to a single turbo??? that' s the first time that one's come up...

[laserb5]

2.8 cams have much more overlap than s4 and rs4 and many say it can be detrimental to performance, although this has yet to be proven. The rs4 cam has lift and duration closer to that of the 2.8 while maintaining almost the same overlap as the s4 cam. So if you are willing to shell out $500 for intake cams I'd say do the rs4. ESP since they were designed for use with k04s

[rogersb6]

Were there any reasons given for the 2.8 heads hurting performance? I can't fathom how having better flowing heads that come off of a stock NA car can hurt performance...

[S4AudiSilver]

go with the rs4 cams instead of the 2.8...unless you are going single turbo!

[ThunderWuss]

i found what i could but the jury still seems to be out on some of the details....everyone agrees that the 2.8 flows better but some think it flows too well for anything outside of a big turbo...from what i read, i would see the most benefit from swapping cams from the 2.8 into my 2.7 whereas swapping the complete head may actually hinder performance...from what i read, the smallest turbos that would see a benefit form the full head swap are tial 650s or similar...thoughts?????



my car is a stage 3...

You have to understand overlap in order to understand why it would hurt your performance. 2.8's have overlap to "pull" more intake air in while the exhausted gases are rushing out, where the 2.7, because it is forced induced, does not need this "pull" to grab more intake air because it has the turbo to cram more air in. Also, with overlap you cool down exhaust gases witch in turn condenses the exhausted air and reduces the airs velocity which means slower spool up times.

[summer]

well,i think 2.8 head is okay....

[1FastB5S4]

how could condensed air hurt spool up time? the denser the air the greater the effect the air will have when it comes in contact with the turbine.

[ThunderWuss]

how could condensed air hurt spool up time? the denser the air the greater the effect the air will have when it comes in contact with the turbine.

It's sience man, you can argue aganst sience [;)]

[Yea.Nice.]

Are there different cams available for the 2.8 heads to eliminate that overlap?

[Trailrider]

Temperature is simply a measurement of how fast things move, atoms and their electrons. Hotter exhaust temps means those molecules are ACTUALLY moving faster. Faster movement then in turn transmits its inertia to the turbine, creating more boost. The cycle then repeats.

[vtraudt]

Temperature is simply a measurement of how fast things move, atoms and their electrons. Hotter exhaust temps means those molecules are ACTUALLY moving faster. Faster movement then in turn transmits its inertia to the turbine, creating more boost. The cycle then repeats.

Sidenote: you want as much 'heat' or energy (=volume) in the exhaust stream BEFORE the turbo. Wrapping headers goes in that direction (not practical with our log style manifolds). Ceramic coating for the same purpose (keep heat in the gas). more volume = more energy to 'drive' the turbine, which is the 'motor' for the compressor.

[vtraudt]

2.8 Heads vs. 2.7 Heads: can someone eliminate the guessing and provide some comparison data for the heads?
Compression, valve sizes, etc.

Ditto on the cams discussed here: lift, duration.

My setup will be K04 turbos with RS6 internals (custom machine turbine housing for RS6 turbine wheel, custom machine RS4 compressor housing for RS6 compressor wheel).

Knowing beats guessing.