mark kibort

i think i saw about 12hp for the headers on the S4... level 2 equal length though. hard to tell, as i did a couple of other things that were responsible for the 30hp gain over stock sans a cat

demetan

Unless your doing other major motor modifications the x-pipe will give you a nice boost in HP.


I do plan on doing mods eventualy, but not all at the same time. I'll probably supercharge it. What other motor mods can beneficiate from headers?

LT Texan

When I look at headers, I see hundreds of square inches of very efficient heat exchanger for under your hood.

Yes, if the exhaust manifold is the weak point, by all means.

atb

My vote would be to not install headers on an otherwise stock motor.

But, yes, they do look nice.

DEVEK L3's on the track motor:

Rob Edwards

William A. had a pretty nice result with 'only' headers and catback (with CARB cats) on his GTS- part of the benefit came from some simple fuel re-mapping (and as it turned out, less ignition timing due to (at the time) all the carbon buildup on the piston tops.

Before:


After:

RFJ

Oh crap you had to do that,I will be slobbering all over myself all day.

demetan

Was the remaping done with a sharktuner? Because that's more than a 30hp gain...

Rob Edwards

It must be pointed out that the 'after' dyno curve is not SAE corrected, so the hp gain is probably closer to 25- that photo is a screengrab, I don't have the actual .drf file of the dyno pull.

That said, the gains really point to the value of being able to re-tune around whatever modification you've made to a particular engine. In this case, the 'before' is a '93 GTS with its typical oil ingestion issues and a lot of carbon. Getting the most out of the headers necessitated a re-tune, which revealed the extent of the carbon deposition, requiring a _less_ aggressive timing map to prevent detonation induced timing retard. The ST2 allowed Greg to maintain a safe detonation margin and still add in enough fuel to buy ~25 hp and ~35 torques. (This GTS later got its head gaskets done and chambers cleaned up- not sure they ever went back and re-tuned, would have been interesting to see the 'after V2.0' gains.

Any time you do something to an engine that alters its ability to move air and fuel through it, you're not getting the most out of the mod unless you're moving the fuel and timing maps to take advantage of the mod, safely.

There is absolutely a learning curve to getting the most out of a sharktuner, but it comes with a crew of experienced users right here that are willing to help, me included.

John Veninger

Ported heads
Larger intake valves
Individual throttle bodies
hotter camshafts
bored engine
stroked engine
larger injectors
aftermarket fuel and ignition system

Slippery slope..........

Ad0911

i guess lots of people, me included, want some extra hp by changing 1 bolt-on thing because we don't know how to cope with the complexity of all things involved. Opening up gbe exhaust seems like a good place to start because it is st ghe end of the line. If that is a restriction that can be taken away....

demetan

I see that you have a 16v engine. On 2v engines, the time the valve must open for efficient scavenging as to be longer than the time on a 4v per cylinder, this mean a longer valve stroke (less compression) or flatten the upper lob of the cam; so why did 'nt they do a 6v per cylinder? Because they knew, beside weekening the flanges of the head cylinder and having to machine extra-precise cams, that there would be someone, some day, that would decide to put headers because they look beautiful...

GregBBRD

You are being tricked by "Internet Dreaming".

No one is going to ever get a 30hp increase by Sharktuning an S4 that is well tuned to start with.

10hp is a lot to expect.

Porsche simply did not leave that much on the table. They equipped these engines with knock sensors, which automatically retard the timing when knocks are present (which allowed them to run near maximum timing) and ran them a bit rich at WOT (and the S4 engines are not sensitive to running anywhere from about 11.5 to 12.5.....so running them rich lost very little power.)

Now if you've got other associated problems that you discover when you are Sharktuning (bad MAF, bad knock sensors, bad hall sensor, leaking dampers or fuel pressure regulator, no full throttle switch, throttle doesn't open all the way) that is a different story.....your car wasn't well tuned to start with.

demetan

Your totally right Greg, the Porsche's engineers did their engine math pretty well & like you say, it's a question of equation. I think the track & race guys comments (atb and John V.) are right on the button; it all depends on what you intend to do with your Tonka...If you start playing with the variables you'll add up to a new equation.

I don't know if you meaned WHP ou just HP, but to put an xtra 10 whp by just adding a new exhaust seems pretty darn good...the 30+ horses advertised by some (for an approximate 3k mod) seems to good to be true...

And having 'web dream' is not that unpleasant!!!

123quattro

4v/cylinder is the ideal number. Others have done 5 and 6, but there is no extra power. It's just for marketing.

LT Texan

M-B did 3 valves per cylinder. I wonder how that stacks up?