FredR

Well they do say great minds [almost] think alike !!!

Bulvot

Your question seems to boil down to: What 0-60 performance improvement can you expect if you install a cross pipe and do some shark tuning. Is that accurate?

The answer will be in the tenths of a second. Between 0.1 to 0.5, all other things being equal and you being consistent with your launches. You can use 0-60 calculators to give you some offline comparative analysis of different power levels, but they will just be rough ball parks.

If you want more than that, you need to add serious power, which it sounds like isn't in your plans. Every second faster in 0-60 times requires a geometric progression in power. Not to mention gearing, traction and weight distribution. Turbo Todd's work on his car is a really good insight into what it takes to improve the acceleration of the 928.

You might want to consider a smart phone application to track your 0-60 times before and after your modifications. In the following thread, I documented what I selected: https://rennlist.com/forums/928-foru...on-timers.html

In short, I like Torque Pro for quick and dirty in motion numbers and last 0-60 time. For more data and accuracy, I really like PerfExpert. Paired with a high speed GPS unit like the Garmin GLO, it has proven to be very consistent. Consistency is most important to me since I'm just tracking the changes to my own car.

If you go with PerfExpert and want all the numbers to plug into it (coefficient of friction, gear ratios, etc), let me know and I can share what I came up with.

Petza914

When I bought my 79 and supercharged it, the most disappointing part of driving it was that I had this 350 HP engine that wasn't fast because of the manual transmission. That's when I decided to have 928MS install a C5 z06 6-speed and that completely changed the drive and experience with the car. Being able to snap through the gears under hard acceleration with the carbon synchros now let's me utilize the power form the supercharged motor.

As Hacker says, the fastest 928s are forced induction with automatic transmissions as the 5-speed manuals are the restriction to what the car can do.

jcorenman

Excellent suggestion, particularly something like PerfExpert which can plot torque/hp versus RPM. One of the challenges with tuning is finding the optimum fuel and ignition timing for each cell. There are some rules of thumb, but being able to do better/worse experiments for each cell would be a real advantage. And a heck of a lot cheaper than buying your own dyno...

Bulvot

Another application to consider for the original poster's purposes is "Speed Logic". They have a free version (aka "Lite") and a paid version (aka "Pro"). The free version has an acceleration timer that has lots of preset options for 0-X speed. But, what I really like, is that you can create a custom timer that starts and stops at any speed that you want. For a manual transmission, like mine, that means I can do a rolling start instead of hammering the clutch, and stop the timer at the end of my gear rather than introduce shifting into the equation. Which is ideal for my purposes of just seeing how my modifications are affecting acceleration over a specific RPM range.

For your 0-60 tests, the application might be ideal.

merchauser

Exactly! and thanks to everyone for all the useful information.

I am fully aware of what my GT is, and what it isn't. just looking forward to a few (reversible) mods to have a little more fun, and curious about how that translates in "feel." while I would like to emulate some of the incredible builds on this forum, I have too many other projects going on to sell the GT and start over. I am content and more than satisfied with this car.

I grew up with small block chevys, and then a variety of 911's with 2.2, 2.4, and 2.7 engines. there was an infinite number of parts available to personalize performance. most were pretty simple with immediate results its not like that with the 928. I have noticed a huge difference just doing the maintenance that hadn't been done; an X pipe and ST2 will certainly be icing on a great cake.

docmirror

Er,,, I'm not sure if you read it in the thread above, but those things are going to net you exactly the square root of bupkis in terms of accel.

The folks on here with real stories to tell of 0-60 improvement are talking blowers, turbos, drag slicks, weight shedding, weight transfer, change trans to auto, etc.

Ok, so I was a little flip to start. But - seriously, why not just get a roller chassis and do it right. You have history with SBCs, so go what you know. Make a real 928 F&F fart can killer.

FredR

Strosek Ultra

Hacker, are the Murf Supercharger kits still around? Can one order a kit?
Åke

Strosek Ultra

Paul, it is actually more interesting to know what the car can do between 60 to 120. It tells you a lot more of how much power you have.
Åke

ptuomov

Somebody should sell a (thoroughly tested) kit for making the 928 S4 automatic transmission take off as fast as possible from standing stop while still maintaining reasonable street drivability. I've demonstrated my ignorance of transmissions in other threads, but higher flash stall speed might help acceleration, as well as shorter rear end. Add some reliability improvements, including extra auxiliary cooling, for high power, and I think one might have something for the modern world that is all about accelerating from one traffic jam to another going thru a traffic light, stop sign, and a radar trap.

Catorce

Alright, I'll play.

Here is the secret to a real fast 0-60 car......TRANSMISSION. Period, end.

Let's use my McLaren 12c and 570 as examples. Both cars are regularly tested on Youtube, etc at being 2.X second zero to 60. Both are 10 second cars, STOCK.

My 12c weighs about 2850# dry and makes 616 HP. Lots of 928s have 616 HP, many are on this board. Yet none of them, not even Todd's car, even come close to a mid 2 second 0-60 pass.

The 12c has "just OK" traction control, nothing fancy.

But the transmission is out of this world. The 7 speed Ricardo double clutch trans shifts in like 20 milliseconds, and there is NO perceptible pause in acceleration, it just feels like the car will keep accelerating forever. For every instantaneous shift, you gain a couple car lengths over a manually shifted car or a conventional automatic.

Without a trans like this, it doesn't even matter how much power you have.

Consider that my stock 12C with the radio blasting and air conditioning on will post times that are as good as or better than Todd's car, which is a full on race car practically speaking.

Modded McLarens are easy to do, and they are low 9 second cars....

100% transmission, that's why they are so fast. You quest for more power is somewhat fruitless because you can have 1000 HP and still not be a fast accelerating car with the transmissions that are available to a 928.

vanster

I find that with everyday driving it's the 30 to 70mph that is important not 0 to 60. With a 6.5 stroked motor I can easily spin the tires in 1st and jump up against the limiter. To me torque is the most fun I have about 440# of it.

merchauser

well said...agreed. your motor is a beast. you must be the envy of every 928 gathering you attend.

ptuomov

It must be a sweet engine for a street car with the smaller intake ports, longer intake runners, two Helmholtz tuning peaks, smaller exhaust ports and header primary runners, bigger cams, and 30% more displacement than the stock S4. I haven’t driven your car or seen a dyno graph, but logic dictates that, when the engine rpms approach the power band, there’s a wall of torque.