I did a couple of searches but could not find the info. Can anybody help me figure out how thick the steel that is used in these kits is ?

Thanks

I think it's 16 gauge, but I'm not really sure...

QUOTE (Jeroen @ Nov 17 2005, 09:41 AM)

I think it's 16 gauge, but I'm not really sure...

don't bother with installing it use the Engman kit if you want to stiffen the car. GT kit is a bandaid that doesn't really address the flexing.

QUOTE (Bleyseng @ Nov 17 2005, 10:24 AM)

don't bother with installing it use the Engman kit if you want to stiffen the car. GT kit is a bandaid that doesn't really address the flexing.

I would agree. The factory kit really doesn't address the biggest flexing issue which is the longs.

So the engman long kit is better. Once that's in, is there any benefit in the factory chassis kit? I've got some extra weight and alot more power

Eric

I know, I know, about the engman kit being better. I'd just like the factory look, that's all. 16 gauge is pretty thick, though. Not sure what I'll do.
Thanks for the info.

Michel

if you're going for the look, just use thinner (regular) sheetmetal

Thats kinda silly if you ask me..

Theres like 2 pieces of the kit that actually do anything.. Do some searches...

Make you use "and"...

"Chassis and stiffening and gt"

QUOTE (michel richard @ Nov 17 2005, 01:56 PM)

I know, I know, about the engman kit being better. I'd just like the factory look, that's all. 16 gauge is pretty thick, though. Not sure what I'll do. Thanks for the info. Michel

The look?

You can't see anything until you remove a wheel.

And you have to hammer form some of the pieces to the fit the car.

And rust will form behind the pieces.

A lot of work + can cause rust + really doesn't do anything + you can't see it = don't do it

So does the factory kit provide any help at all? If not, why did they do it?

The 2 kits answer different questions, engman kit for the firewall forward, and the factory kit for the firewal back?

Eric

QUOTE (Jeroen @ Nov 17 2005, 02:02 PM)

if you're going for the look, just use thinner (regular) sheetmetal

Those thought have crossed my mind.

QUOTE (URY914 @ Nov 17 2005, 02:07 PM)

The look? You can't see anything until you remove a wheel. And you have to hammer form some of the pieces to the fit the car. And rust will form behind the pieces. A lot of work + can cause rust + really doesn't do anything + you can't see it = don't do it

As have these.

My mind really is not made up on this. Your comments are contributing to the thought process, however.

Thanks

Michel

Interesting debate, isn't it? The factory guys have the "factory" clout. Yet their solution doesn't match the real-world results of some of the small guys.... who happen to have much more experience in the trenches.... with results that can be proven.

I think you have to boil this down to categories... do you want a full cage? If not, then strengthen within, where it counts most... inner longs, ala Engman style. Personally, I like a hybrid.... strenthen the inner longs, then brace to the shock towers for triangulation.

The major flex in the chassis is in the longs. There is not a lot of flex in the firewall back.

And since the factory chassis kit was poorly designed... it does even less....

QUOTE (Andyrew @ Nov 17 2005, 06:45 PM)

The major flex in the chassis is in the longs. There is not a lot of flex in the firewall back. And since the factory chassis kit was poorly designed... it does even less....

how do we know this?

Rich

Testing?

I know Engman tested the flex of the car before and after the long kit was put on...

But I havent seen anything to prove the GT kit stiffer...

Heres a thread that might help...

Chassis stiffening

OK, so I'll go with the assumption that the factory kit was an experiment that, at best, did nothing positive, i.e. added weight, encouraged rust, etc.

That said, where are the weak spots and what are the solutions?
1. the longs - full cage or engman kit.
2. Trailing arm mounts - inner ear reinforcements?
3. Shock towers - ???
4. firewall to rear console - ???
5. Trailing arms - can be boxed, but should be left as easily repairable "weak link".

My point is that the engman kit is not a replacement for the factory kit, it's a different modification. (if someone asked "what size torsion bar", I would not reply "not torsion bar, use swaybar" even if it's a better answer)

As long as I'm highjacking the topic, is there any flex issues in the rear susp assembly as a single unit, trailing arm mounts to shock towers across both sides? Is the problem just tying the whole rear suspension unit to the rest of the car?

Eric

QUOTE (michel richard @ Nov 17 2005, 02:56 PM)

I know, I know, about the engman kit being better.  I'd just like the factory look, that's all.  16 gauge is pretty thick, though.  Not sure what I'll do. Thanks for the info. Michel

"Factory Look" I don't think even the Factory Cars used the kit


The weakest part of the car is where the long is joined to the bulkhead. Lots of cars with big engine and big tyres tear apart there! Thats why the Engman Kit stiffens the car like no other as it "fixes" a design flaw, not enough metal at that chassis point.

The argument that keeps hitting me is that if I really wanted a properly engineered cold-hearted, not too expensive machine, I'd get a Miata. (ok, I do have a Miata, but it's my winter car). If I got an original 914/6 that had an engine fire, it's because I'm after the slightly zany stuff that does'nt quite make sense. But in my money earning life, I'm just as cold hearted as the next guy.
That's why I'm considring a sub-optimal (probably) solution, that has some purely aesthetic advantages.

Michel

Here, quoted from Brad is why the Chassis Re-inforcement kit was designed....not as a mistake...not as a test,,but to solve a specific problem area...

Brad States

"I need a pic of the kit laid out. I'll circle the ones you can use. If you have a cage that passes through the rear window or ties the rear shock towers together.. you wont need it at all. The chassis cracks on the tub right where the centerline of the shock goes up (draw a virtual picture inside the fenderwell following the shock) The only reason the chassis' crack is when you add more spring (225 and up will start the process within a few months of TT or RR) The problem is: the tops of the shock towers are not strong. They are only held in place on 2 sides (both of which are weak) The actual frame rail ends in front of the shock tower....leaving the sides vulnerable to cracking.

The outside mount normally wont crack until the inside one lets go.

B "

So, again I would ask when these opinion are being thrown out there....show the proof that the chassis re-inforcing kit has no value before you claim it...


Rich

Okay, the argument I just dreamed up: it's like a girl wearing nice undies, even though very very few people are going to see them (hopefully)

I think the factory kit has gotten a bad rap here.

Find Jeroen's thread. Both Gint and I weighed in heavily there when Troy was building Gint's tub. We were there with an ex-Boeing ariframe engineer, a bare tub and a factory kit.

I started out thinking the same as the others here (the thread bares that out... watch my posts change, also, weight in if you've actually had a bare metal tub in front of you and reviewed this at that level). We found that a lot of what was said here didn't hold water and a lot of what the factory designed did.

Find that thread (sorry, not very good at the search thing) and you'll get a lot of good information on the subject and "other" stiffening tricks the factory used. I think Gint did a great job of weighing the facts and using what was out there.

We installed the factory kit, windshield post reinforcements and Mark's kit.

My $0.02 but what do I know...

QUOTE

2+4+3 are questionable. 4+3 dont do anything. Several old school racers figured out that the chassis will still crack even under number 5. Number 5 helps support that increase in spring rate that I spoke of above.2 right above 5 (when mounted on the car) really doesnt do anything. The piece below it is whats left of the frame rail. I think people install these pieces (because the factory did) (because so and so has it) (they think it increases the value) After seeing factory race cars from that era (they where designed in the early 70's) Porsche hacked together whatever they could to get the cars on the tracks. They where the factory.. they didnt expect this stiff kit to last..they would throw the chassis away and build a new race car. I even doubt that the factory designed this kit. I'm finidng more and more that they listened to racers and adjusted accordingly.

I think thats Brads Follow up statement......

I dono... Seems to me like he's bashing it pretty darn well....

I never said it did NOTHING.. but I did say it did very little in comparison to the Engman Long Kit...
wait.. I'll just quote myself, so you dont miss quote me..

QUOTE

The major flex in the chassis is in the longs. There is not a lot of flex in the firewall back. And since the factory chassis kit was poorly designed... it does even less....

I dont claim to know anything... I have a long kit sitting in my garage, and I plan on semi tube frame work simular to Jeroens

Eric,

You mean this thread ?

http://www.914world.com/bbs2/index.php?act=...f=2&t=13925&hl=

Nope...

It was one that Jeroen started about stiffening his long at the rear. It involved cutting and welding a section back by the rear shock tower. The discussion turned to how to handle such a thing in a street car vs. a semi-tube frame or tube frame car.

I believe that the factory engineers did a bit more than guess, and they were reacting to structural stresses that they had seen from racing cars....


Lets not forget that these are the guys that built a 19 lb tube frame for a race car...they had to fill it up with helium and put a guage in plane view of the driver so that if the frame cracked...the driver would see it..

Granted that the same designers were not present when the 914 was designed...but when a problem with the frame came up,,,you bet that the best frame guys came and looked, all gave some opinion and possibly added more than was needed...but you dont see the resulting stress that is being transfered by building up one area and not another...

I was reading an article in Up-Fixen Der Porsche and someone brought a 914 chassis to a lab in CA somewhere...cant remember exact details...anyways they put the chassis through some vibration testing to determine how to stiffen the chassis.

The end result was a roll cage system unlike any I have seen designed in many years...

the cage was firmly secured to the middle of the long,,,triagulating to the front hoop and the rear hoop and back down to the suspension console...and back to to the trans mount...

The interesting thing was that most of the stress that they saw on the middle of the car was right in the middle of the long...this point is a negative point...it needs to be ties to two positive point (so these engineers were explaining.)

If you take a look at Jeroens thread about how he cut the bulkhead from the rear trunk and found a very weak , non existant weld joint that ties the front of the rear shock tower to the car...

This load created is supported by the outer frame area instead...right were the rear chassis re inforcement kit goes....

It is a bandaid...for sure...but it fixes a known problem that hasd only one other solution...

I think that if you look at how Jeroen dealt with this situation, you will have more info about how to proceed...

Jeroen addresses this directly by dissasembling the tub to a certain extent and welds/rewelds this critical connection...

Again, the stiffening kit is designed to fix this problem from the outside...that would explain why there is so much metal...to spread out this load and not create another problem...

I think if it this way...if a structural engineer gave you a set of drawings with all the calulations based upon you putting in five posts under a given beam....you choose to only use four....you just changed all the math and calculations of the entire solution...

Same with the chassis kit...you are changing the math by eliminating some of the pieces...the stress fracture will occur somewhere else instead....but that stress is still there somewhere and if its is not properly spread out and you focus it on one acute corner....you have created a new break point.


But....It sure depends on the purpose of the car...the tires..engine etc...

Rich

I'm way with Rich on this. Rich is talking about the right thread... I tried but I can't find it.

The problem I saw with welding that joint in a street car was...

1.) You have to do some massive cutting (weakening) to do some welding. In Jeroen's case it's not a problem because that bulkhead was removed. You can weld it back up but as JP weighs in on that thread... the metal around the weld will weaken

2.) The bulkhead for the rear trunk acts as a ladder frame no more than 1-2 inches from that point so I don't see it as a weakness for a street car.

3.) The factory pieces that span that area (as Rich describes) go precisely from that area back to where the tranny mount comes over to form another ladder. It was mentioned here that "the factory piece didn't attach to the long at all" when in fact, that outer piece of sheet metal "is" the 4th side of the long (we have cut up cars to prove it).

The airframe guy literally drew out a stiffening kit on the tub and "then" we showed him the factory kit. His recommendations were nearly identical. We found that every piece in the factory kit had relevance.

All pieces were installed.

Now, I'd like to see that thread!

The mod mentioned in the "missing"thread was to weld the seam where the long meets the shock tower (blueish arrow in the second picture). The problem with accessing this section in a street car is that the boxed support (purple/pink section in the first picture) encloses this area so that you can't access it without cutting & welding. The yellow arrows in the second picture show where the boxed section attaches to the long on the left and the shock tower on the right. I'm sure that could have been stated more clearly.

here it is welded up

Hay, I an't gonna weigh in. I believe in cages which are OT here. Ya'll do what you think is best.

the more things change the more they stay the same...

and for the record, I'm leaning towards the (partially) factory kit.

I installed 1/2 of the factory kit and none of the engman kit.

Its not that the engman kit is not good..... for me it was all about weight.

I carefully weighed each and every brace on my car and thats how it got to 1850lbs with a fully metal body.

I did partial factory kit and I also did the seam welding where applicable.

here is my long welding after it was sealed back up:

Engman's kit has an obvious function: it keeps the front and the rear of the car from moving independently of each other by increasing the material connecting the two, as well as strengthens the connection between the left and right sides of the car. What is the point of the Porsche kit? Is it to counteract the twisting forces of rear suspension movement (i.e. maintain suspension geometry)? That seems to be the answer since the pieces a limited to the outer control arm pivot back to the shock tower.

This all leads me to think that the inspiration for Porsche to design the kit was perhaps because they developed their race suspension to a point where the chassis was limiting further improvement. So it would seem to be that obviously the Porsche kit did something right. What is debatable is if the Porsche kit is more help than hinderance (weight).

But the way I look at this is that the Porsche kit is for serious race cars that have pushed their suspension to the limits and need to tighten up the rear end, Engman's kit is for all cars to tighten up the front to rear and left to right connection. The only matter left that I can think of is if someone can create a more effective rear stiffening kit.

Thanks for tuning into the McMark's 3 am Stream Of Conciousness show. Tune in next week for more long winded, obvious, and barely readable opinions.

the gt-kit and Engman's kit is like comparing apples to oranges
they both address different things

the gt-kit is meant to prevent cracking of the rear frame, mostly the rear shocktower and reinforces the outer susp.pickup

engman's kit addresses longitudinal and (some) torsional flexing of the chassis
this works very good in cars without a rollcage, but if you have a cage, it is just access weight

What the heck ARE you doing on at 3:30 am mark?

Im writing a term paper due in 3 hours...

Whats your excuse??


I think the weight argument is a little redundant.. Your going to add... what, 20 lbs to the car? if you use ALL of the pieces? There has to be some chassis stiffening if it is placed in the right location... which if its done by the factory, it'll do something... hopefully..

QUOTE (Jeroen @ Nov 18 2005, 03:25 AM)

the gt-kit and Engman's kit is like comparing apples to oranges they both address different things the gt-kit is meant to prevent cracking of the rear frame, mostly the rear shocktower and reinforces the outer susp.pickup engman's kit addresses longitudinal and (some) torsional flexing of the chassis this works very good in cars without a rollcage, but if you have a cage, it is just access weight

I totally agree with this. If you don't want to add a cage, add the sheetmtl kits.

And from what I've read about the factory and the 914, I don't believe they spent a whole lot of resources on the 914. They were up to thier ears in 917 design issues. There was not a real "factory" effort to develop the car. They didn't have a true factory team, they really just supported the private teams. Much more develop time was spent on the 911 also.

Why didn't the factory just add some bars from the main hoop to the rear shock towers? This may have been a rules issue.

Sorry to get a little OT

QUOTE (Andyrew @ Nov 18 2005, 04:29 AM)

What the heck ARE you doing on at 3:30 am mark? Im writing a term paper due in 3 hours... Whats your excuse?? I think the weight argument is a little redundant.. Your going to add... what, 20 lbs to the car? if you use ALL of the pieces? There has to be some chassis stiffening if it is placed in the right location... which if its done by the factory, it'll do something... hopefully..

If its a race car then I don't think weight is redundant...
20lbs here and 20lbs there eventually add up to 400lbs.

I agree with the comments above about the 2 different kits addressing different areas. and I should have clarified that I do have a cage (not tied to suspension points per rules)

but overall the factory kit has some usefullness and isn't a complete "waste of time" as is often thrown around.

QUOTE (Jeroen @ Nov 18 2005, 04:25 AM)

the gt-kit and Engman's kit is like comparing apples to oranges they both address different things the gt-kit is meant to prevent cracking of the rear frame, mostly the rear shocktower and reinforces the outer susp.pickup engman's kit addresses longitudinal and (some) torsional flexing of the chassis this works very good in cars without a rollcage, but if you have a cage, it is just access weight

My /6 has both. And it isn't a race car. I think it's going to work out quite well.

BTW - We also welded that shock tower/longitudinal seam from the back side (inside the shock tower). The thinking was that the weld would penetrate through both peices. Nothin to lose really...

QUOTE (Andyrew @ Nov 18 2005, 03:29 AM)

What the heck ARE you doing on at 3:30 am mark? Im writing a term paper due in 3 hours... Whats your excuse??

Well tonight it's that my girlfriend and I went to see that 12:10 showing of Harry Potter.

But I'm up till 2 am or so most every night.



Anyone have any pictures of cracked rear frames? It would seem that the debate about the GT kit is due to lack of information. We can only accurately evaluate the solution if we truly understand that problem.

While we're talking about skipping less necessary parts of stiffening kits...

I was wondering if the rear part of the Engman kit is REALLY necessary. The part of the firewall it goes on is already double walled, above that is a couple feet of firewall, and another small double walled section just under the rear window. That makes for a REALLY deep beam, and it seems like it would be more than strong enough.

With ya there Royce but I don't know much about Marks kit other than the fact that it's well made and goes in easily. (like all his stuff) That area has some serious double walled goodness.

I'm agreeing with:

* Two different kits.
* Cages are great but... another story (car w/o a cage)

This is why I think Mike made a great decision with his tub:

Factory kit (plus some top secret additions)
Engman Kit, and
Windshield post reinforcements

For a car without a cage and bars welded to the suspension points... I don't think it gets any better than that.

(Our ugly little cars won LeMans in 70 and 71... I think the factory put a little effort and resources into them)

The only stuff I've ever seen...printed actually....was about a 914/6 running a Mexico to Alaska rally several years ago in Excellence. The fella that owned the thing was a well known racer....whose name escapes me.......Porsches on Pike's Peak guy, IIRC.
Anyhew, that made me assume that his car was well prepaired.
Again (IIRC) he had to stop twice to get the car rewelded up in the back end in the area of his "stiffening kit".

I had a kit at one time. Took one long look, figured how it would have to be welded in, and shit canned it....just my .02, of course....do what you think is best.
The clamshell stiffener/repair kit from the guy back East (another missing name) looks like a worthwhile piece. There are disagreements as to where the weakest part of the 914 chassis is.....and how to improve it.

Sorry, I said I wouldn't post....I lied

I believe the clamshell is made by Brad M.

Jeff Zwart

Thanks guys, this old fart would be lost without ya

Brad Mayuer makes the Long kit but not the clamshell kit. The clamshell is Restoration Design. And if you want to add some serious weight get Brad's kit.

Jeff stopped here in UT to get his car welded at a friends (fellow PCA'er) shop... are you sure it was the factory kit that was the problem??

QUOTE (Eric_Shea @ Nov 18 2005, 08:17 PM)

Jeff stopped here in UT to get his car welded at a friends (fellow PCA'er) shop... are you sure it was the factory kit that was the problem??

No, but the article refered to it......IIRC.
Suppose I could go dig it out. I'll do that.

(edit)
Couldn't find the article....then thought about 9eleben Porsche World....nope. Found some other gud shit that I'll have to re-read tho. I ain't given up...just for tonite.