Venturing outside of my comfort zone a bit, as I don't really know much anything about NA headers: Isn't this just a question about the length and diameter of the primaries and the length and diameter of the collector? Maybe these MSD headers are too large diameter, or the wrong length, for a stock S4 engine. Maybe the pressure wave terminating element is too far from the collector. But one should be able to build headers that would improve power and/or torque of otherwise stock S4 motor, no? I think the only reason why the car factories don't usually build welded tubular headers is cost and reliability.

 

Would the 85-86 manifolds give any hp/torque gain? And would these manifolds fit a 4.5L engine?
According to an article I received there would be a really nice gain in hp/torque on a 4.5L engine using the MSDS headers,

 

they are a pretty ancient design, and the collector does leave allot to be desired, but you cant argue with the price, and im sure they make more power than the stock parts.

 

These were installed on my 928 in the mid 80s. I have absolutely no idea how they compare performance-wise to the MSDS headers (they're staying on my car so it doesn't affect me either way), but visually they look less constricting at the collector than the MSDS headers do (second picture)

 

What kind of work needs to be done to fit these MSDS headers to the stock 4.5L engine? The article says the ports need porting. Why? is the inside diameter of the headers different from the stock manifolds? And is it possible to do the porting on reconditioned heads (not yet fiitted to the engine) without dismantling them all over again)? And what kind of work is needed to fit the MSDS headers to the stock exhaust? Is there any point in doing that? Is it still a better idea to use 85-86 manifolds?

 

Hello all,

This is my first post. I have owned my shark about six years and followed this forum since beginning. I like to thank the people for valuable information to keep my shark running and make it better year_by_year. I have had the Motorsport X-over in my -87 S4 AT US about three years. Last winter, I switched to MSDS headers and X-pipe. I have also had RMB since beginning.

I have newer dynoed the car, but after playing with exhaust stuff and Autohority chips, also doing lot's off tune-up, I think, I have some basic feelings to share with you.

The X-pipe will give nice and broad torque and HP, across the rpm range. It works wery well with AT and US final drive ratio, since good low end torque.
The MSDS + X-pipe, wakes up somewhere around 3krpm. I can even feel some mild vibration and the exhaust tone chages dramatically. The engine definitely breaths much better on higher rpms, with headers and X-pipe. Below 3krpm, the car feels slightly weaker than with M-sport X-pipe.

My personal feeling is that if you have manual gearbox and even better, planning to go for cams with more lift/duration, the headers and X-pipe is way to go, since you aren't that interested of low end torque as with AT-box.

I have also installed PEM's and 24lb 4-hole injectors from Roger since the plan is to ST:ing the shark in near future. Mr. Speake changed the PEM's maps to work with 24lb injectors, so I have been able to drive the car without ST:ing. The car was working fine with those modified maps, it even passed the smoke test. I belive, the ST:ing will give nice improvements, but it has to wait by now.

Also, I'm on list for getting cams from Lizard. Last winter, Erkka(vilhuer) changed the final drive gear ratio to euro-model and the torque tube stall speed was raised to around 2150 rpm. Hopefully those modifications will work with AT + headers + new cams + ST:ing. We'll see that by early next summer

All the best, Simo

 

Hey everyone,

Just updated original post on the group buy.

 

Dual 2.5" w/ X-pipe and Flowmasters, Stage 3 Murf....8psi backpressure @ 12psi boost.
Measured at the emissions port on passenger manifold.

 

Good work!! That's the kind of data we need to be seeing.

I would be curious to see a direct comparison before / after the flowmaster's.

 

So this is with close to 500 rwhp?

+1

 

I hope, dyno runs scheduled this Saturday.
Will have pressure gauges hooked to manifold, before and after muffler.

 

Brian that was using the OEM SS exhaust manifolds right?

 

Yes.

 

Was the 8 psi with or without cats?

A lot of people that actually measure exhaust issues drop the flowmaster fast, single chamber magnaflows are favored by many.

 

Sorry if I missed it, I'm reading this on my phone... Did we find out if a mixture of 16v and 32v orders count together toward the number needed?

I want a set of 16v. My email to them regarding if they would have another 50%? off Columbus Day sale has gone unanswered. I can put aside being annoyed about that for a decent deal via other means.