Roll bar and Engman question, Trying to decide Options

[Joe Ricard]

Got my roll bar hoop the other day and fitted in the car. Works nice and sits just a tick above the targa bar.

Anyway I am going to put the forward diagonals from 4" below the curve of the hoop and have them end up 3-4 inches forward of the hand brake cut out.

I am also going to penetrate the fire wall and tie in the rear shock towers to the hoop.

is putting the Engman kit a good idea or would 16ga. scab plates under the bars at car connection points be enough. Remember lighter is better. Mainly concerned with stiffening the car for Autocross. at this point I wil never run Wheel to wheel racing in this car. (IMG:style_emoticons/default/driving.gif)

[DNHunt]

Joe

This is just my observation. I installed an Engman kit this weekend. On my car the surfaces of the longs at the firewall was not flat and so it took some effort to force the kit to adapt to the long. I suspect that you would have an easier time with a scab plate and it would make more consistant contact with the long under it.

[Krieger]

I remember many people in the past compaining (world/club) that the shock towers are only connected to the long on 3 sides and is one of the places where the frame cracks. Why not run them bars back to the top of the frame rails near where the trunk lid springs are?

[Joe Ricard]

Because I plan on cutting into the rear firewall and tying the shock tower to the upper top section of the long. then attaching the tube to scab plate.

[J P Stein]

Why not kill 3 birds.....
See the pic. Under the doubler plate is an unwelded area from the factory.....bout a half inch gap, tower to long end. I put in a "slug" and welded the mess together.
Over that, the doubler, then the tubing. That is .120 wall stuff. It goes up to the roll hoop.....well, you get the idea.
I got rid of the hoop around the top of the cage after bonking my helmeted haid on it's padding.....bout knocked me out.

[URY914]

(IMG:style_emoticons/default/popcorn[1].gif)

Five replies.... (IMG:style_emoticons/default/confused24.gif)

[Joe Ricard]

Maybe if one of ya posted a picture of your car's roll bar with a naked chic hand cuffed to it.

Each site has it's own charm.

[jhadler]

I was thinking about where one would best want to tie a cage into the suspension. It make more than perfect sense to tie into the front shock towers, deflection there results in alignment changes. And the tower is under a fair bit of lateral stress. But the rear shock tower? Wouldn't it be better to tie into the lower mounting points? I'm not a chassis expert, so someone please correct me if I'm wrong, but the upper shock towers in the rear don't particularly effect location, and are really only under vertical stress (against the spring). Lateral deflection there doesn't effect the alignment, or at least I don't think it does. The lower mounting points for the trailing arms are doing all the hard work, I'd think that would be the best place to tie to the cage. Best maybe? But not the easiest. Am I wrong here?

-Josh2

[J P Stein]

No, Josh, you're right, but verticle deflection is what needs to be eliminated at both ends of the car. Reduced pitch bending of the chassis is what I am after.
It also helps with roll (twist) of the chassis. It stiffened things up quite nicely...shoulda done it years ago. The towers are a handy place to tie into.

One other thing. The rear towers are NOT welded directly to the ends of the longs, but tied together with some sheet metal bits. I hear as rear spring rates rise, the towers can pop loose......that would suck. I saw some indications of that on the shitbox...minor, but not ignored.

[Joe Ricard]

One problem we discovered on a certain course with very high grip was the car must be twisting a lot because we could not shift the car 2-3 or 3-2 while under hard cornering. We had to wait till the car was going straighter. So I suspect the rear half of the car was twisting and doing that vertical thing ya'll are talking about.

[jhadler]

One problem we discovered on a certain course with very high grip was the car must be twisting a lot because we could not shift the car 2-3 or 3-2 while under hard cornering. We had to wait till the car was going straighter. So I suspect the rear half of the car was twisting and doing that vertical thing ya'll are talking about.

Stupid question maybe, but why would you be shifting at the moment you were heavily loaded in a turn? Sounds like a recipe for spin...

-Josh2

[ottox914]

One other thing. The rear towers are NOT welded directly to the ends of the longs, but tied together with some sheet metal bits. I hear as rear spring rates rise, the towers can pop loose......that would suck. I saw some indications of that on the shitbox...minor, but not ignored.

Could you or someone post pics of this, or perhaps pics and where to look to see if this is a problem? With little arrows? While my car is not a red hot road racer like some of yours, it gets twisted a bit at the auto cross events I do. I have had a loud mystery klunk in what sounds to be the rt rear. Started when I lowered the car too much. I found front lower control arm hitting the tub. So I raised things up a bit, re-corner balanced things, raised the rear spring rates from 175 to 200, and went with a bigger front sway bar to keep things balanced. I still get the klunk, mainly at higher speeds with a sharp hit, like a pot hole or freeway expansion joint at 75 mph, although when the car is loaded laterally on the rt side at an auto cross, and I hit a bump in the pavement, I can hear it again, but not nearly as often as I hear it on the way to and from the event. I hate to think I'm tearing my car up, but I've checked the rear shocks, both are good, and checked every bolt I can back there, both sides, all tight, but still have the klunk.

Sorry. Ending hijack. Back to discussions on cages.

[J P Stein]

Dumb shit me didn't take any pics "before" the doubler plates were installed.
I exposed only the top of the long at the tower.

I have seen pics from Jeroen, I think, on this site a few years ago of the vertical interface of the long/tower.
This area hides behind the double sheet metal of the rear bulkhead. The lower extremities of this sheet metal has suffered some cracking ....hopefully, before the doubler plate/down tube install. I have been running 275-300 lb rear springs for a couple-3 years on a very rough AX venue.

You have to cut that sheet metal out to get at the joint. I may, since the engine is out, get at that if I can do it without sacrificing the sheet metal.....doable, me thinks. I've been rootin' around the engine room anyhow, what's a bit more?


Found it....old.
http://www.914world.com/bbs2/index.php?sho...c=15765&hl=

[grantsfo]

One problem we discovered on a certain course with very high grip was the car must be twisting a lot because we could not shift the car 2-3 or 3-2 while under hard cornering. We had to wait till the car was going straighter. So I suspect the rear half of the car was twisting and doing that vertical thing ya'll are talking about.

Yeah I get this with mine. Hitting 1st on your way to 3rd when your at limit exiting a corner can really suck. Sent Nathan spinning off track once. Eventually I'll need to work on traingulating rear of the car a bit.

[McMark]

I would expect a car with only a roll hoop and forward diagonals to find some gains in using the Engman kit. If you're going to increase the cage size in the future (more bars) then adding the E-kit will probably end up being unnecessary.

[Joe Ricard]

Well at Saturday's Autocross I thought of Josh's comment everytime I was going through a very long increasing radious turn. entering in middle of 2nd and shifting at 5 grand under pretty good lateral G's.
Car shifted ok but I was careful.
So sometimes ya just gotta shift through a corner.

[J P Stein]

entering in middle of 2nd and shifting at 5 grand under pretty good lateral G's.
Car shifted ok but I was careful.
So sometimes ya just gotta shift through a corner.

Not if your motor can pull 7Krpm. (IMG:style_emoticons/default/biggrin.gif)

[grantsfo]

entering in middle of 2nd and shifting at 5 grand under pretty good lateral G's.
Car shifted ok but I was careful.
So sometimes ya just gotta shift through a corner.

Not if your motor can pull 7Krpm. (IMG:style_emoticons/default/biggrin.gif)

..or 7500 RPM (IMG:style_emoticons/default/biggrin.gif)

Although there are plenty of courses that require a shift on long bends. Especially on the track. At Laguna I have to shift into 3rd as my car is in heavy compression coming out of the corkscrew. One of the harder shifts I have to make.

[Joe Ricard]

Well I certainly am not going to spin a motor that was in several different boxes last week. None of them are balanced and the bottom end ain't too purdy.

Better to short shift than scatter it for a plastic trophy. I did get the trophy anyway.

New motor will even make power to 7500 RPM.

[J P Stein]

So, Joe........whatcha gonna do?
Your season is about over and you need a plan. (IMG:style_emoticons/default/biggrin.gif)

Adding tubing is gonna add weight to an already kinda heavy car (for XP).
Seems to me that you will have to do some serious weight reduction to make up for it, eh?

I have probably 80ish lbs of tube in mine and it's still lighter than yours.....even with the 6 & all, so it can be done..... ya gotta be ruthless about it tho.