Optimal front sway for a 1.7 ? Options

[Literati914]

..
to clarify - far as i know its 15 front and 16 rear.
i could try and double check that.
i didn't mean it had 13 mm sway bars.
i meant it had front and rear sway bars, not just a front one...

Yes that helps, cause you had me confused and thinking 1.8L had a bar I’d never heard of being installed. Thanks again.

And just a side note, while we’re on the subject… the /6 cars apparently (and eventually) came with a 16mm at front and a 15mm at back - so opposite the stock /4 set up… I suppose that’s because of the extra weight of the engine and nothing to do with a power increase over the /4, as super hawk has explained.



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[Superhawk996]

And just a side note, while we’re on the subject… the /6 cars apparently (and eventually) came with a 16mm at front and a 15mm at back - so opposite the stock /4 set up… I suppose that’s because of the extra weight of the engine and nothing to do with a power increase over the /4, as super hawk has explained.

Good student (IMG:style_emoticons/default/beerchug.gif)

[wonkipop]

note - they appeared to have the slightly stiffer bar on the rear,
which kind of goes with your idea of a single softer bar on the front.

Can't judge bar stiffness just by diameter. Although the rear bar appears larger (by 1mm) it is a far less effective geometry than the front bar. I'm sure the overall rate of the rear bar is less than the front based on experience though I haven't done the math to calculate the rates.

The 15mm OEM front bar is basically a stright bar with two very short lever arms down to the LCA's. That aspect makes it highly effective.
However, the drop links are long, thin and probably flex substantially reducing effectiveness some.

The 16mm OEM rear bar has very long lever arms. But then the rear drop links are very short and probably don't flex much at all. But on the whole, the stiffness lost to the long lever arms won't be made up by the short, effective drop links.

Bottom line, I don't know the engineering rates (wish I did - next time I'm bored, I'll do it) but don't judge an ARB just by it's diameter.

very good point. quite a different affair that rear bar.

[wonkipop]

..
to clarify - far as i know its 15 front and 16 rear.
i could try and double check that.
i didn't mean it had 13 mm sway bars.
i meant it had front and rear sway bars, not just a front one...

Yes that helps, cause you had me confused and thinking 1.8L had a bar I’d never heard of being installed. Thanks again.

And just a side note, while we’re on the subject… the /6 cars apparently (and eventually) came with a 16mm at front and a 15mm at back - so opposite the stock /4 set up… I suppose that’s because of the extra weight of the engine and nothing to do with a power increase over the /4, as super hawk has explained.

.



the sixes also have a slightly wider front track?
which makes them a bit different too?

[914_teener]

note - they appeared to have the slightly stiffer bar on the rear,
which kind of goes with your idea of a single softer bar on the front.

Can't judge bar stiffness just by diameter. Although the rear bar appears larger (by 1mm) it is a far less effective geometry than the front bar. I'm sure the overall rate of the rear bar is less than the front based on experience though I haven't done the math to calculate the rates.

The 15mm OEM front bar is basically a stright bar with two very short lever arms down to the LCA's. That aspect makes it highly effective.
However, the drop links are long, thin and probably flex substantially reducing effectiveness some.

The 16mm OEM rear bar has very long lever arms. But then the rear drop links are very short and probably don't flex much at all. But on the whole, the stiffness lost to the long lever arms won't be made up by the short, effective drop links.

Bottom line, I don't know the engineering rates (wish I did - next time I'm bored, I'll do it) but don't judge an ARB just by it's diameter.

very good point. quite a different affair that rear bar.

I spent a lot of time playing around with different things when I did my 914 suspension. Mostly in IMHO this is where you should throw your money and time in the car and not so much on the engine other that have a good running one.

For street and ocasional twisties I ran Billies Sports on all four corners ''progressive" valving set up. Ajustable perches with #140 SR in the rear.

NO rear bar.

In the front the car was ever to slight biased down in the front by torsion adjustment.
Rack spacer to take out any bump steer with a solid steering coupler. Turbo tie rods and stock ball joints....all new.

I found the stock drop links length for this junk and threw them away and used Tarret adjustable links for the bar.

Corner balanced and aligned to sock specs less a little more camber in the front, that car drove like it was on rails......forget the size of the engine it had a 1.7.

I could take 911's ....downhill of course in the corners.

I ran 205's BTW for rubber all the way around not a staggered set up on stock 2.0 fuch's. The fenders were already rolled when I got the car.

Mostly I think the car didn't really need one but Porsche...and still to this day...and I know cause I normally never buy a P car that isn't optioned up makes money by selling options....my Cayman was the only exception. The car is just so fun to drive who needs Nav.

My. 02 without all the technical explanation of why.

[Literati914]

.., that car drove like it was on rails......forget the size of the engine it had a 1.7.

Yeah, essentially I’m just trying to set up a little 1.7L, as a fun daily driver - thanks for sharing! (IMG:style_emoticons/default/beer.gif)


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[flyer86d]

We ran a 19mm front with a 16mm rear on our 71 1.7 which did not come with sway bars stock. They were both H&H bars. The car was a great autocrosser and track car with reasonable ride on the street. One friend in our club ran the 912 small bar in the front only and it worked fine and had a better ride on the street.

Charlie

[horizontally-opposed]

I followed that recipe . . .

The only real problem is that what is good for autocross isn't always what you want for the street. AX tends to favor cars that are easy to rotate at low to moderate speeds. You very well find that ability to rotate isn't appreciated on a big highway cloverleaf sweeper taken at 2x or 3x posted speed. (IMG:style_emoticons/default/dry.gif)

Don't get me wrong, we all follow the recipe to a degree. The moral of the story, don't just follow blindly, tune to what suits you and know why you're doing it.

Following that AX recipe forces some ride degration with the 140# springs that might otherwise not be needed had we opted for a softer spring and a smallish rear bar.

Don't get me wrong, I largely followed the same recipie you laid out when I got started back in the early 90's with suspension and chassis tuning and didn't fully understand the tradeoffs I was making. Not everyone want's to go to all the time, expense, and trouble to to learn how tune. That's OK as long as they know they are making tradeoffs in the process. (IMG:style_emoticons/default/beerchug.gif)

Yep, fully agreed re: what one needs for autocross vs street (or track). While I'm a big fan of autocross, the need to rotate the car to get it to turn in at low speeds doesn't always lead to good setup—or muscle memory!—for higher speeds on road or track.

Interestingly, the "no rear anti-roll bar on a fast 914" dictum of the 1980s/1990s should make the car less prone rotate—right? Of course, 140lb springs add roll stiffness at the rear, while front spring rates were often left alone (ish). Reminds me a bit of Porsche's approach with the 987.2 Boxster Spyder: They decreased the rear ARB, but upped rear spring rates by 50%! When you think about how well a regular 987 Boxster/S handles, that's a big "tweak." But it made for the best-handling 987.2 hands down—and that's saying something because all 987s were great! (IMG:style_emoticons/default/wub.gif)

My current setup—911T front torsions bars, 140lb rear springs, 22mm front ARB, no rear ARB, rubber bushings all around—worked well when the car had 80~ hp and still works well with 200~ hp. Everyone who tries the car raves about the handling, though I know it can be a bit better/sharper still. While I followed the advice of 914 autocrossers and track-day denizens when I was a teen, curious to listen to current thinking so many years later…as I will probably do my 914's suspension and brakes one more time. <I hope!> Currently eyeing KW dampers, different ARB(s), and an LSD along with 986 calipers front and rear. Spring rates seem about right. Don't want to go higher for the street…

[jkb081]

I do not feel it is a fair comparison between a 912 and a 914. The 912 has a torsion bar rear suspension, while the 914 has coil over shocks. Both systems have very different handling characteristics. My 76 came with both front and rear sway bars. While my 73 has zero bars. It is my understanding that most, if not all early car did not come with them.

[roblav1]

Pete, adding LSD will make the car push coming out of corners. The primary reason for LSD is to prevent inside wheelspin while hard on throttle out of a tight corner. If no wheelspin, then why bother? The car will rotate better without one.

We all have preferences... mine is spring rate before ARB rate. Good to know about the 987.2 Boxster Spyder going with a lot more rear spring. Too bad they're crazy expensive!

[roblav1]

I do not feel it is a fair comparison between a 912 and a 914. The 912 has a torsion bar rear suspension, while the 914 has coil over shocks. Both systems have very different handling characteristics. My 76 came with both front and rear sway bars. While my 73 has zero bars. It is my understanding that most, if not all early car did not come with them.

All of my SWB 912 coupes came with a front bar. My 912 Targas did not.

All of my SWB and up to 73 LWB 911 coupes came with a front bar. 67 911S was first to have a rear bar. I added a rear bar to a couple of them, which made them more lively. I also removed the front bumper weights on all my SWB 911s but also ran 6" Fuchs. Lottsa fun!

[horizontally-opposed]

Pete, adding LSD will make the car push coming out of corners. The primary reason for LSD is to prevent inside wheelspin while hard on throttle out of a tight corner. If no wheelspin, then why bother? The car will rotate better without one.

We all have preferences... mine is spring rate before ARB rate. Good to know about the 987.2 Boxster Spyder going with a lot more rear spring. Too bad they're crazy expensive!

Yep, felt that with Paul Sayegh's 914 3.6—though I wondered how much of that was due to his type of diff (torque-biasing, I think?), tire/outer track width, and suspension setup.

Have a lot of time in cars with and without LSD, and in a lot of situations. Depending on how they're set up, they can not only cancel inside rear wheelspin when leaving a turn, they can add supreme confidence on the brakes on the way into a turn. ARBs and other elements need to be working in concert to avoid understeer, but I've driven a lot of rear- and mid-engined cars where all elements of the suspension are doing just that—and the feeling is tremendous. And pretty rare. Getting to it adds up quickly, and the fact is a 914 (1.7 too) with nothing more than stock-ish front torsion bars, a front ARB, 140lb rear springs, good dampers, and good tires is a seriously effective car—and a ton of fun too. Probably 85-95% of the ability & fun factor for a lot less money. Maybe that's why the simple recipe for the 914 was/is so popular. All of the above can be done for roughly the price of adding an LSD.

You brought something up I hadn't really thought about: While I got crazy inside rear wheelspin in a lightly modded, 320~hp 987.1 Cayman S with an open diff on back roads years ago—to the point I finally had to turn PSM off and manage it myself, deleting a safety net that rarely intrudes otherwise—I don't think I'm getting much if any wheelspin with 200~hp in my 914. I do want to add short gears, though… (IMG:style_emoticons/default/idea.gif)

But back to the OP's question: For a 1.7, my vote is something like the old Weltmeister front ARB and no rear ARB with stock front torsion bars & 140lb rear springs on adjustable perches. Good dampers, too (Koni reds if you can find or rebuild some). Dead simple setup, simpler than mounting a rear ARB, and can be corner balanced. More than enough for most drivers and most 914s—rides nice, works for autocross, and even good enough for occasional track use. Will work well with tall sidewalls, or short ones. And ready for double the power if/when you get around to it.