What do you have for chassis stiffening? Options

[Chris Hamilton]

Joe, My car does that with an autopower rollbar bolted in.

This is why it would be nice to actually MEASURE flex before and after.

Stiffening is great, and 914s need a bunch of it, but it's pretty hard to just eyeball a car and tell where it needs stiffening without some way to measure it, otherwise you're just welding lots of tubing into it and going "well that looks good", with no idea which bits actually helped and which bits didn't. The car will probably be faster and feel better afterwards, but could you have accomplished the same thing with less weight?

It cost me $500 for my aluminum pressure plate to lose a couple pounds and it is going to cost me another $500 for a fiberglass trunklid to lose a few more pounds after that. I'm sure as hell not going to add 20lbs of steel tubing until I know for sure what it's going to do.

[J P Stein]

It doesn't take an engineering degree to see where the points of load are on a 914......hint....there are 4 and round black things right near em'.
Once that tough bit is over, then you gotta figure out where you can attach structure & how to bridge between them.

As Brit wrote, a butt dyno reveals a huge difference. The chassis moves more like a single unit and the suspension does it's work in a more controlled manner.
This causes the car do the same thing every time when loaded....or close enuff. (IMG:style_emoticons/default/biggrin.gif)

BTW, there is closer to 60 lbs than 20 lbs extra. Bridges aren't light.

[Randal]

It doesn't take an engineering degree to see where the points of load are on a 914......hint....there are 4 and round black things right near em'.
Once that tough bit is over, then you gotta figure out where you can attach structure & how to bridge between them.

As Brit wrote, a butt dyno reveals a huge difference. The chassis moves more like a single unit and the suspension does it's work in a more controlled manner.
This causes the car do the same thing every time when loaded....or close enuff. (IMG:style_emoticons/default/biggrin.gif)

BTW, there is closer to 60 lbs than 20 lbs extra. Bridges aren't light.

I've taken JP's approach on adding front and rear bars tied in front to the shock towers, then to the front torsion bar mounting. In the back we have run the bars as close to the towers as possible, although not as nice as JP did it.

Can't wait to see the performance difference. Who knows, with a clear head, the car might be competitive.

[J P Stein]

I've taken JP's approach on adding front and rear bars tied in front to the shock towers, then to the front torsion bar mounting. In the back we have run the bars as close to the towers as possible, although not as nice as JP did it.

Can't wait to see the performance difference. Who knows, with a clear head, the car might be competitive.

My car is no shining example. It's kinda like a house remodel.....rip this out add this here...and here.....here too.....since I've got the welder fired up & this estra stuff is just laying around. No original ideas, just built on other folks'.

IF I knew then what I know now, it would be lighter & prettier....prolly safer too. Mine is the homebuilt CSOB method......my whole 914 project was like that...learn & build as you go. I wouldn't want anyone to think I had an overall plan. (IMG:style_emoticons/default/rolleyes.gif)

[Chris Hamilton]

It doesn't take an engineering degree to see where the points of load are on a 914

This is where I think we'll have to disagree. (IMG:style_emoticons/default/smile.gif)

The 'build it so it feels better' approach isn't scientific enough for my tastes. Just like people who dyno their engines after every change I'd like to see a quantifiable result.

My 914s and yours are built specifically for autocross. This means that we are not concerned with crash protection. Are the bars in your picture of the doors actually providing structural support or are you just adding weight with those? I think it takes more than an eyeball and a welder to determine that.

[J P Stein]

I've been building stuff for 40 odd years....most of it engineered by some damn good folks that I've had access to. I'm the curious type and have talked to those guys asking just why they do things as they do. No, not everyone has an "eyeball" but it can be developed over time. A good hand can make a bridge strong, but it takes an engineer to make it light.

You want to break things down to numbers...be my guest. Get/build your self a chassis rack (or rent one), drag out the load cells, strain gages, micrometers & jacks, get an engineer to interpret the data and design a cage to stiffen your 914. I would guess you'll end up with something very similar to what guys have been doing for 20 years.

You're right, those side bars are for chassis strength. The lower ones were one attempt to do the job from a few years back......but were inadequete. The upper bar tied into the front & rear shock towers is much more effective.....but not ideal because of the bend. The verticle bars twixt the side bars is an attempt to help the upper bar do what I wanted.
Again, a remodel.

The safety aspect pertains to them bunny ears on the top of the hoop. A higher roll bar would have been mo better....but the car had a lid back then and it wasn't required......remodel. (IMG:style_emoticons/default/biggrin.gif)

[Joe Ricard]

Chris there is no way your bolt in autopower cage is anywhere near the stiffness of my car or even JP's for that Matter. You don't have any diagonal attaching upper right rear corner to lower left front corner. Tubes to tubes not body panels and tie all the suspension pick up points to the cage.

Race cars are measured in 1000's of pounds per Centimeter of deflection. (or some sort of huge factor)

Not an ME but I know a bunch of them that race cars.

[J P Stein]

BTW, our trip down to your house at Marina was quantifiable enuff for me.
Andrew showed up with his usual set up (as did we) and got his hat handed to him.
His changes for the next day produced quantifiable results also......and good for him.
Did he consult your engineering type....?

For our first time on concrete, we did OK. I would definitely make some changes if we ran there full time.

[Chris Hamilton]

JP, it will be fun to see how Andrew and Britain do this year at the mid engine shootout! Will you be coming to drive your old car, or bringing an MR2 to the mix?

[J P Stein]

Brit is headed down that way for the SD National Tour event in April. The timing
of the shoot out is still up in the air and much will depemd on that. Of course, ya'll could setp out of your little pond & all get together at the SD event. At present, I have no plans to make it, but would for a Tour event get together.....I wouldn't miss that for the world. (IMG:style_emoticons/default/biggrin.gif)

[Joe Ricard]

Raced in the little pond yesterday. PCA had an event that was supported by our / My Gulf Coast SCCA region.

Drove my buddies box stock Miata amongst the 09 Carrera S, New Caymen S and some other really nice cars.

Smoked em, like shooting fish in a barrel. Bunch of nice people that all got an invite to our next event.

[Randal]

It doesn't take an engineering degree to see where the points of load are on a 914......hint....there are 4 and round black things right near em'.
Once that tough bit is over, then you gotta figure out where you can attach structure & how to bridge between them.

As Brit wrote, a butt dyno reveals a huge difference. The chassis moves more like a single unit and the suspension does it's work in a more controlled manner.
This causes the car do the same thing every time when loaded....or close enuff. (IMG:style_emoticons/default/biggrin.gif)

BTW, there is closer to 60 lbs than 20 lbs extra. Bridges aren't light.

I've took JP's approach on adding front and rear bars tied in front to the shock towers, then to the front torsion bar mounting. In the back we have run the bars as close to the towers as possible, although not as nice as JP did it.

Can't wait to see the performance difference. Who knows, with a clear head, the car might be competitive.

Update:

Having gone pretty much all out I believe using (essentially) a cage from the front torsion bars to the front shock towers, then back from there to the cockpit cage and back from there to the rear shock towers plus bars in the cockpit to the engine hump, all make a huge difference. In addition reinforced ears with alumimum standoffs to the firewall and Foley reinforced trailing arms, with needle bearings really work.

Reinforcing the ears is simply a requirement if your going to run big slicks, as the sheet metal won't hold up otherwise. In fact I broke mine my first time to the track.

Anyway the car not only does what you want it to do it has lost any tendency to snap spin under extreme situations. But some of that has to be credited to the tires and tire setup, which is another subject.

And you can buy this chassis if you'd like. (IMG:style_emoticons/default/idea.gif)

[Randal]

Raced in the little pond yesterday. PCA had an event that was supported by our / My Gulf Coast SCCA region.

Drove my buddies box stock Miata amongst the 09 Carrera S, New Caymen S and some other really nice cars.

Smoked em, like shooting fish in a barrel. Bunch of nice people that all got an invite to our next event.

Amazing how well a Miata handles, isn't it.

Anyway nice going Joe... You ought to offer to drive their cars next time. (IMG:style_emoticons/default/biggrin.gif)

[Joe Ricard]

Geeze I was reading this thinking wtf did I do? Man that was a long time ago.

The snap oversteer I think is less now because you took some of the "spring" out of the chassis. I noticed the same thing in my old car, just point it in and it went exactly where I wanted.

[Randal]

Geeze I was reading this thinking wtf did I do? Man that was a long time ago.

The snap oversteer I think is less now because you took some of the "spring" out of the chassis. I noticed the same thing in my old car, just point it in and it went exactly where I wanted.

Right, there is a video, of the Medford Spring Enduro from last year on YouTube. https://www.youtube.com/watch?v=7XTxvcpka5w

At about 1:06 you see me enter a corner a bit fast, with a poor line, coming off the straight. Check how far the car rotated and then came back with a simple off throttle steering correction. Somewhat unusual for a 914, hey?

I agree with you that the stiffer chassis does help as well.

[smokey]

My
Lilbasterd
Gets much stiffer wen chancing any Porsche car. Aft smoking it . She porscheeeee .always wants to rest , and it smokes a bit .
Hee he,,,,,,,,,,


(IMG:style_emoticons/default/smoke.gif)

[ThePaintedMan]

Dafuq?

[Bullethead]

How did this thread get reanimated? Last post was 1/6/2015. (IMG:style_emoticons/default/poke.gif)

[d914]

egman inner longs
tangering racing rear console support with bolt in bars, reinforced suspension ears. plate steel swing arm brackets.

cage if I start tracking car. I like the gt one but not sure how much that does.

[mlindner]

I had a full roll bar cage for many years. The last upgrade while building the 914-6 GT Tribute I extended to all suspension points.