I'm currently running Bilstein front inserts in my Boge T Struts, that may have been valved for my 914 but I don't know for sure as they were installed by the PO. In efforts to get better brakes I am putting in some Koni 3.5" Struts. Has anyone here compared the two in there car? What should I expect going from Bilstein's to Koni Yellow's?

Both inserts are a great choice either way. The Bilstein's are mono tube inserts with no adjustment/tuning and the Koni's are twin tube with rebound adjustment (weight transfer). I used to be in the Motorsports department with Koni and like the ability to tune the car for different set ups and tracks. I would not mix the two technologies together.

Sometimes , shock ajustability is a gimmick looking for a need...I am sure there are plenty of people that go thru the adjustment motions with their shocks...I envy their sensitive shock dyno like butts.. I can only tell a general improvement when they are valved to my car weight and springs..the ability to stay that way for a while seems to lean toward Bilstein...and revalve and rebuilds are relatively cheap...most don't have properly valved shocks , just something close....adjusting improper valved ones is akin to polishing a turd...I vote bilstein with my wallet

Thanks. I already have the new 3.5" Koni Struts in hand, I am mostly curious if the driving dynamics will change much between the two. The Koni struts have red inserts which I'll probably set to medium and run for now.

I've found the Koni's to be stiffer than Bilsteins in general. When running in the stock class with our local PCA group, I liked using the Konis because I could crank up the rebound and it would simulate stiffer roll bars during the quick transitions of an autocross. In the longer turn arounds the car would still roll, but in slaloms they reduced the roll.

Now I've moved up to GT class and am actually using stiffer springs and bars so I'm back to the Bilsteins which seem to control the wheel ends better.

Back in the day I had some shortened strut tubes (2.5") with some better race valves koni inserts. Had more wheel travel before bump stops. Only adjusting I did was front push = soften shock.

Thanks guys. One thing I can't figure out is why the PO installed 220lb rear springs and left stock torsion bars up front (17.9mm). With the Bilstein pressurized shocks and a 19mm sway bar it doesn't feel that soft in the front... but seems a little mis-matched. I've been running it this way for 10 years. Once I went from 205's to 225's in the rear it seems to be well balanced enough for a street car. Probably would handle better with 19 or 20mm front bars.

I just want a well handling street machine that I can take to the track or A/X on occasion.

What exactly are you trying to achieve? Sounds like the issue is the perceived mismatch in your head, not necessarily a problem with handling.

Appears that the PO was looking to get some push out of the car by putting the stiffer springs in the back. Probably could have done the same by installing a rear sway instead of the stiffer springs.

Regardless, identify the real problem (if any) and work on tuning it out. Don’t just throw parts at it because it doesn’t seem right...

Ask around the track, drive another or drive in another car, see if there is really something to gain.

It's the other way round... Stiffer = less grip (relative to the softer end).

Well I read a couple articles stating your shocks should match your torsion bars. I appear to have stiffer shocks and softer torsion bars in the front. Typically in autocross I have over steer. However when the back end gets loose its controllable and predicable.

I believe my car would handle a little better with 19 or 20mm front torsion bars.


Funny when I think back to when I ran 205's rear tires and 220lbs rear springs it could spin out really fast, I was 180 before I could blink. Now with 225 rear tires and 200lb springs it's much more predictable. I also have 3.2 motor (had a 2.7L before)

Our autocross/hillclimb/street/fun/ whatever car Huey has Koni adjustables around, 225 lb springs, 21mm torsion bars, and whatever Weltmeisters big front roll bar is, no rear roll bar. 3.2 engine, 245/16 tires around. Car handles PERFECT. Autocross, hillclimb, and through the mountains, it’s predictable and confidence inspiring. Around town it’s definitely stiff, but not harsh at all. I wouldn’t change a thing.

Thanks for sharing! Are the Koni's factory valving? Do you play with the rebound adjustment with different tracks? I have heard leaving the rebound on soft works well.

They are as from the factory.
I do stiffen them up for the track, soften for hillclimb and street and honestly have no idea where they need to be for autocross since we've only had them on for one autocross and i played with them each run. Need more time with them there...

I have been using Bilstein shocks for years on my track only car. I am fortunate to have a major Bilstein facility near where I live. I provided data to the shock engineer to custom valve my shocks. I provided information like: spring rates, sway bar size, corner weights, tire and wheel size, type driving (track only). Custom valving was reasonable in price (less than $100/shock) and turnaround time also reasonable.

Because the shocks are not adjustable, I probably don't have the ultimate in performance gain, but I can live with it because they are install and go race. Don't need a shock expert with me at the track to do constant tuning.

Here is what they did for me. The graphic shows before and after settings and what they did to low, medium and high speed settings. My spring rates are 450 front and 400 rear. Coil over front not torsion bar.

Click to view attachment

koni yellow stiff
Koni reds softer NLA
Koni hydraulic reds the original NLA

do you have red hydraulics or gas ??

No, you need to re-read what I said. “Get push out of the car” as in get rid of the understeer...

A quick test would be to adjust your front sway stiffer (if you can) and see how it responds. If it handles closer to your optimum, get the larger torsions, but loosen up the sway again. Your sway should be set that you can fine tune the handling dependent on course or conditions.

I know you can get the Koni reds for a Koni strut, I think you can still get them for a Boge?

The struts came with hydraulic Koni reds. They are original, seem to function ok. But when I compare them to my Bilsteins by a hand push, they are waaaay softer. The Koni struts ended up having a bad deformation on the top by the gland nut for some reason, so I sent them back to the seller. I am now going with Boge struts and I can use either insert. I think I will look for some Koni Red gas inserts to try.

You should be able to get Konis for Boge struts - that's what I have. The newer gas shocks are better than the older hydraulics, but you may be able to find someone to rebuild and possibly revalve your hydraulics if you are wanting to keep those. Probably almost as much to do that as to just buy new ones though.

Scott

This is great to hear. What are you running for a- arm bushings? I hear that can make a difference too.

And are you running Koni reds or yellows?

Ah....good question!
Elephant Racing Polybronze bearings... and yes, supposedly they do make a difference.

https://www.elephantracing.com/porsche/914/...914/polybronze/

big dif in valving

Some one told me the Koni's are better for a mostly street car because they absorb the small bumps better with the dual tube design. Has anyone had experience with this?

The two brands offer 2 different technologies for stock bolt in configurations. Twin Tube (Koni) vs. Mono Tube (Bilstein). Mono tube dampers have a larger piston than twin tube and depending on valving, will begin to create force at slower shaft speeds. Koni's have a separate foot valve at the bottom of the inner cylinder that creates compression force and not at the piston. The Bilstein/Mono Tube damper creates compression and rebound force at the piston. When adjusting a Koni, you are only adjusting the rebound forces and not compression. So yes, some people may say that a stock Koni may be "softer" over small bumps than a Bilstein.

On my track-oriented 914, I have had both and much prefer the Bilstein shocks. Unfortunately, I have the Koni's on the all four corners at the moment - that will change. The Koni's ARE noticeably softer...for a street car go with the Koni.

T

To be clear I am not a suspension expert and most of what I have here came from reading various sources and certainly is more of opinion than fact.

First I think having an adjustable suspension is a must if you want to control how your car behaves. But if you want a solid and well proven solution it is hard to look past Bilstein. Adjustable components are very useful in dialing out over steer, or under steer, increasing handling characteristics, and getting a better balanced car. So that is the choice I made.

There is not a one specific setting on an adjustable shock that makes all 914s handle well and there is no non-adjustable shock that is perfect for all 914s.

If you have adjustable shocks you need to understand what you are adjusting.

Typical "street" applications use either 1-way adjustable or 2-way adjustable shocks.

1-way adjustable changes the rebound only. 2-Way adjustable can be adjusted for bump and rebound. During bump, the shocks and springs absorb the upward movement from cornering or the road. Rebound is when the shocks extends back to their original positions using up the energy from the compressed springs.

Most Konis are 1-way (8010, 8041, 8210, 8241, 8610, 8641, 8710, 8741 Series). 2-way Konis includes 8011, 8042, 8211, 8212, 8242, 8611,8711, 8742 Series.

So you have to understand with 1-way adjustable you are only controlling how quickly the shock returns to its original position. That means too stiff of a setting and it is possible shock movement wont keep up with changes in the road surface = tires lose contact with road. Too little rebound stiffness and you ride waves of oscillation after each bump.

I have the Koni 1-way 8641-1077 Sport shocks on front and rear so I will discuss those. If you are advanced enough have purchased the 2-way you likely know this already!

While this is simplistic and there are many more factors to consider, this is a generalization of what happens when you play with the rebound stiffness on the front and rear.

Front rebound increase = More Under steer
Front Rebound Decrease = More Over steer
Rear Rebound Increase. = More Over steer
Rear Rebound Decrease. = More Under steer

So while we all want to crank up the settings to 11 (Spinal Tap reference for the young ones) and drive like hell. However, depending on your car, that might not keep the handling of your car consistent.

You can see that either increasing/decreasing rebound at both the front and rear tends to have a canceling effect. But depending on your sway bar, springs, ride height, and many other factors I don't claim to understand, it is possible that for the best or most neutral handling car, taking the approach of simply dialing everything up to 11 may not be right for your car.

I had been keeping notes on the changes I made on my car and found a slightly softer setting on the rear than the front kept the over steer more in check. So if you have adjustables resist the temptation to immediately go to the max as you will likely find that is not the best setting.

Of course now that I have added adjustable front shocks, adjustable sway bar drop links and rear sway bar I get to start all over.

Thanks guys! All points noted. Great info Mblizzard.

I love how the 914 is like a street legal race car, that if I want I can even take it to the local race track! So much fun...

I was surprised I was recently on the track with many modern cars (focus rs, wrx, genesis, newer mustangs) and I got my butt kicked. Even though I got a good power to weight ratio I have a lot to make-up in suspension and braking (and seat time too). None of those cars really interested me, but I would like to get it a little more dialed in and go back to hang with them better. It was cool though, many people there were enamored with the nostalgia of my 914. Part of my problem was I was to worried to wreck the car, so didn't want to push it too hard.

Worrying about wrecking the car is a good thing..

I learned a lot about what I was doing wrong and greatly increased my understanding of how a car works by reading How To Drive by Ben Collins aka The Stig.

No magical secrets just sound fundamentals we all should review.