UpFixenDerPorsche

Alright. Ok Ok Ok ... I promise this is the last time ...

Again, just in from a short run to the mall, and it's again. Every time I drive.

One thing I forgot to mention: my rear tires are 50 profile, not 45. (16". All that was in stock on the day I was desperate).

50 profile tires have a 7% greater rolling radius, which equates to a 7% rise (taller) overall gearing, (and which I could readily feel when I first drove the car with the new rubber). Hmmm, but the side benefit was that it almost zeroed out the 8% high speedo readings. (Over here we have seriously bad speeding law margins ie you can be booked for 1mph over the limit. No joke).

This will have had nothing to do with my dyno readings as they were done on a chassis dyno (Dynapak), but the take-away message is that the throttle response is still way sharper with the 50 profile rubber than it ever was with the 45 profile rubber. Even with the A/C running.

Those who have fitted 18" 35 profile rubber will have this (uninteded) taller gearing.

In one way I'm looking forward to returning to the 45 profile (acceleration ... mwaaah harr harr) but in other ways not, in that with the shorter o/all gearing I spend so much time shifting instead of going forward that it makes me want to go back to my S4 auto. Heaven forbid. (A 6-speed manual? Whyyyyyyyyyy???)

But as I plan to fit 18" rims (when I find an elegant, stylish design), I know the car will be the same 'fun' car to drive as it is now. (By then I may have also fitted Colt TriFlo cams).

OK. Heads up: Take Away message(s):

- IMHO the S4 manifold, when re-finished, is a Thing of Artistic Beauty and really makes the engine bay, so who would really want to throw it away?

- at the same time, who really wants to spend a couple of thousand $$$ to liven up their drive? (most of that outlay being to overcome the well-acknowledged choke value of the S4 manifold) Not many.

I'll be the first to acknowledge that tackling this DIY in your shed may be challenging to some, but to others, given the right build details, will be a bag of fun, and I have no doubt that somewhere, in some snowed-in shed, a Rennlister is beavering away at this as we speak.

Having finessed my design as I went, I now know how to go straight to the 'guts' of the build and finish it with minimum fuss in minimum time.

Should anyone want to tackle this mod, I'm prepared to provide all assistance (except I won't blow your nose for you ... ) to get you on your way, just as long as you promise (Scouts Honor) that in your first attempt you will absolutely replicate my modifications without question.

Knowing US ingenuity I can see an enterprising Rennlister finding a way to provide this mod on a core exchange basis.

I watch (and really enjoy) American Pickers for a few reasons:

- the always beautiful countryside of their travels
- the picker personalities.
- and the often off-the-planet wacko owner's of the decades-old moth-eated sheds full of stuff reflecting the inventive personal freedoms of the US Constitution. Something of a survival-of-the-fittest approach. but we won't go there ...

- but most of all - through the astonishing range of featured inventions / ideas and successes / failures - the series, to my mind, is a fascinating social mirror into the history of have-a-go US free enterprise, and to my mind, one from which the entire world has benefited. Worthy, to my mind, of a modern history archealogical study.

Hence my belief that there is someone, somewhere, in their shed ...

):-]


UpFixen

Speedtoys

Apologies if I missed it..did we get dyno numbers posted?

UpFixenDerPorsche

Ohhh dear ... somehow one child always seemed to be away from school on the day ... LOL.

Hey Speedtoys. I've posted the before/after SAE corrected dyno runs below.

BUT BUT BUT ... as I've ranted here many times ... the measured dyno improvement does not for one moment the measure of instantaneous throttle response - viz the 'new life' in my car - you know - that what puts a big GRIN all over yer face.

You feel the tiniest dab on the throttle, as if the car had lost 300lbs. Or something like that


Ciao.

Speedtoys

Im not arguing against ya..

And ya..im away from school too much these days. Currently in a brutal 3wk Germany trip for work.

SteveG

Apparently we did not, at least not in this thread.

Maybe he was, but the some others were in school and did not see it. "Where's the beef?"

UpFixenDerPorsche

Oopsie.

Is there an icon for a red face?

ptuomov

What is the fluid dynamics / resonance method by which you are picking up 50 Nm or torque, or 40%, of torque at 1500 rpm? Which one of your modifications did that?

Speedtoys

...I know what im doing with my spare manifold this summer...

atb

Okay, you caught me.

I've been carefully and secretly amassing all of the requisite tools and supplies to undertake this brazen step toward performance nirvana.

Now.....the only remaining question....do I start with the crepe paper streamer or the elmer's glue...

It's too overwhelming....perhaps I'm not worthy....

Hilton

In the spirit of the modern BMW M3, I'd go with the piece of cardboard attached to the spokes using a clothes pin. The noise will make you feel faster

Jerry Feather

By my calculation the 245 45 16 tires are 24.68 inches tall and the 245 50 16 tires are 25.64 inches tall. That makes the 50 profile ones only 3.9 percent taller. Where did you come up with 7 percent?

terry gt

rolling radius is different than height . think pie 22/7

Jerry Feather

Yes, but it is still the same percentage difference which is 3.9%

UpFixenDerPorsche

Arrrhh geeee Ptuomov. How would I know? LOL.

After looking at lots of CFD images depicting airflow into bellmouths in various configurations, all I did was to look very closely at the existing bellmouth arrangement within each plenum, attempt to visualise the existing airflow/turbulence, and the set about re-shaping the bellmouth lips and lead-in's to what, in my Mind's Eye, would improve airflow to the bellmouths.

I mean it's not all that hard to copy if you have an eye for lovely smooth flowing curves ... ahem .. koff koff ... like those on the body of the 928. |:-\

So I did. Not for a moment do I think these are optimised, but neither for a minute do I doubt these are 90% better than the original design.

Don't know how many pics I've posted re my process.

I repeat ie repeat ... that I did what I did on the basis of an "it can't hurt" experiment, and a chance to test my understanding CFD theories.

Again, for the n-th time, the result was beyond my seat-of-the-pants expectations, so I paid for a dyno test to check the improvement. (See earlier post).

I have no idea which of the three areas of modification gave the greatest improvement.

Fair go ptuomov, how on earth would I?

It was a once-only opportunity so I had to make all changes at once, and was a spur-of-the-moment decision, in my garage, while I was changing out a manifold with rattling flappy shaft bearings and a defective flappy valve actuactor.

What would you have done, given the uncertainties involved?

Even now, given the low cost and simplicity of the changes vs the in-yer-face results, why would you not consider the exercise?

Hey ptuomov, from memory I've explained all this several times over, so surely there must come a time when all that is left is to get on with it, don't you think? Well should you have the need.

It's not as if S4 owners have to mortgage a kidney for this so pls don't complicate life for those who want to replicate my manifold mods.

In due course I anticipate similar gains with GT and GTS manifolds.

Look - I did what I did and got what I got.

If the truth be known, as a 40 year degree qualified electrical engineer with a heavy mechanical engineering leaning (no - I don't wear overalls and carry an oil can), I have serious mathematically-based insights into the underlying driving forces of this air flow stuff, and it's around this that I've done what I have.

So Ptuomov, in my most polite manner, I ask that you stop over-analysing this result, and, given the very low-cost handyman/hobbyist nature of my methods, that you go with the flow.

After all what on earth does any Rennlister or reader have to lose but some extra performance?

UpFixenDerPorsche

Hilton, you're being a very naughty boy!

LOL