Tech Forum : Recommendations

redmist

Posted Friday, Jan 14th 4:31pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 491

NY USA
357i , 325i e30 turbo

Ok the shell will be here in a couple of days. As I have a fresh sheet of paper, no paint to scratch and no seats to rip. What structural changes should I make?
This is wide open guys except the motor is going to be an M30 (in the spirit of a B6)and I'm not putting in M3 suspension etc. I want to keep it a e21.
I want to get the car down to no more than 2000 lbs but rigid, but think a roll cage would be too heavy.

ichiwan2

Posted Friday, Jan 14th 5:12pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 64

Kuala Lumpur, Malaysia
BMW320/6(e21)

Once confirmed that the car is rust free, get some chassis stiffening PU foam into the side sills and any hollow chassis areas. You could even fill up the rear quarterpanel with the stuff. Main disadvantage is, its a little bit more difficult to repair dents in these areas.

Benefits
- stiffer chassis - less creaking as you go up a ramp diagonally, for instance.

- Less noise, particularly, road noise.

If u r also into audio, soundproofing sheets on door panels, firewall, the entire floor and the trunk/boot floor, rear and side panels, boot/trnk lid.

Have fun!!!

RDAvena

Posted Friday, Jan 14th 6:02pm [Edit] [Quote] [IMS] [View car]

Staff
Post nr. 961

SELECT * FROM users WHERE clue > 0
1981 323i, 1988 545is, 1997 528i

It depends on how far you will want to go. Just thinking out loud again:

Have you thought of the front and rear subframe in chrome moly or aluminum tube? Quite a bit of weight in the rear. I know some may be screaming on making an aleready light-in-the-ass car lighter, but you can replace that weight with good useable weight like a large diff and a fuel cell. The front should allow you to get the engine lower and further back improving your center of gravity. What is it like one inch thick? The unibody should be plenty stiff as-is, could be a bit more with some angle bracing from the strut towers to the firewall. Mig in a panel to cover the sunroof hole. Permanently fix in in some thicker lexan panels in the rear quarter windows to stiffen up your rear.

You know, the usual

imaradiostar

Posted Friday, Jan 14th 10:04pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 181

Nashville, TN
81 323i, 82 525i, 85 524td, 90 535i

Is it really possible to have a 2000 pound e21 with a big 6? I would think that's pushing it.

Hopefully I'm wrong!

jamie

Jason_323i

Posted Saturday, Jan 15th 1:13am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 193

UK, Scotland
323i 2.7 tripple webber track car. Maserati Biturbo

Hi Pete

I think you can go that light with a roll cage especailly if you strip out a lot inc the heating etc and all the spare brackets and the chassis will be a lot stiffer. Look at David Macntyr’s car is way below 2000lb

There is even a 24v m6 engine on ebay uk at the monument
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&rd=1&item=4517240186&ssPageName=STRK:MEWA:IT .

From a handling point a tension strut fro the front end and a dedicated roll bar is got to be the way to go as it makes a huge difference when used on fords with a very similar front strut set up.

Or you could keep it period, when they built the gruppe 5 e21 Rainer Bratenstien who over saw the project grafted on the front and rear suspension from the CLS to save development time., you could do the same but you need a set of gruppe 2 or korman arches. And of course you know how to sort the steering.

Jason

JJG323

Posted Saturday, Jan 15th 1:24am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 447

Reading MA USA
1979 BMW 323i

Hey I really dig that engine. But it will cost to much to convert so I am stuck in the e30 2.8 liter area.

Yes, a big six is do able. Steve Fizgerald had a 3.2 liter in his e21 for many years.

I think it will work on fine. Pete I like the mini roll cage.

http://www.ioportracing.com/Merchant2/
merchant.mv?Screen=PROD&Product_Code=60870&Category_Code=AP870

Race Roll Bar (shown with optional Shoulder Harness) - 320 77-83

Quantity in Basket: none
Code: 60870
Price: $332.95

I am getting that one from my car.
Later,
J

MayanArch

Posted Saturday, Jan 15th 9:12pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 55

Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978

ichiwan2 wrote:

Once confirmed that the car is rust free, get some chassis stiffening PU foam into the side sills and any hollow chassis areas.

I have always liked the idea of doing this, but never knew where to source the foam.

Any info would be appreciated.

RDAvena

Posted Saturday, Jan 15th 9:16pm [Edit] [Quote] [IMS] [View car]

Staff
Post nr. 971

SELECT * FROM users WHERE clue > 0
1981 323i, 1988 545is, 1997 528i

it is better not to use foam as foam traps in humidity and parts start to rust. If you need structural rigidity it is better to add steel.

jesse

Posted Sunday, Jan 16th 11:28pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 310

SF, USA
Dinan 1978 333i, honda insight, audi S4

hey red,

all the rally cars are seam welded.

if you have about a billion hours of free time, a chassis and a welder why not seam weld the car
for extra stiffness?

bmw_m_320i

Posted Monday, Jan 17th 1:31am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 141

Helena, Montana
none right now :(

the next question is, are you going to have a back seat?

ichiwan2

Posted Monday, Jan 17th 3:57am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 66

Kuala Lumpur, Malaysia
BMW320/6(e21)

RDAvena wrote:

it is better not to use foam as foam traps in humidity and parts start to rust. If you need structural rigidity it is better to add steel.

The PU foam expands tremendously and depending on the grade u use, is water repellent. As the PU expands, it will push out moisture through any cracks or openings in the chassis joints. Even if moisture is trapped,surface rust may occur on the inside surface of the chassis, but is prevented from getting worse by the PU blocking access of air/oxygen/moisture, which are the main requisites for rust, i believe.

We will know in a few years time, as I have done it on my e21.

The PU foam gives additional stiffness without a major weight penalty - the whole lot of foam I put into my e21 weighed not more than 1.5kg (3.3lbs)

aussie323i

Posted Monday, Jan 17th 9:58am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 280

australia
1979 323i

Hi there

A mate of mine did this for a rally car- he totally seam welded the body and foam filled everything- body rigity was great but once completed he found the car wanted to go up on two wheels all the time! It was very quick, but you had to have big balls to get the speed!

He also had a second rally car without as much chassis stiffening and it was much easier to drive as under load the chassis had more flex keeping the wheels on the ground but ultimately if you could handle the stiffer one it was quicker..... ie. if you didn't back off when on two wheels

Cheers

Ben

Posted Monday, Jan 24th 1:57am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 48

Eureka, California
1982 320i, 1981 323i

This is a bit more radical than you're looking for, but I'd like to try this.

imaradiostar

Posted Monday, Jan 24th 4:21am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 194

Nashville, TN
81 323i, 82 525i, 85 524td, 90 535i

whoa...looks like an old ugly benz or something now!

kpeters

Posted Monday, Jan 24th 8:44am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 257

San Jose, Costa Rica
1981 320/6 Kastanienrot-Metallic 5spd

Ok man! that short E21 looks awful!

redmist

Posted Monday, Jan 24th 9:14pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 497

NY USA
357i , 325i e30 turbo

Thanks everyone for the input.
The tube front and rear subframe is very enticing Ray (low cost, greater stiffness and weight savings etc etc) I am not sure if I have ability to do it though. I'll give it a try.
I want to keep the car a semi-sleeper if possible so the roll cage is out , I am going to try to keep the back seat as well.
Don't have a billion hours Jesse but selective seam welding is a definite as is ditching the sunroof.
The foam is attractive as well, I have to do more reasearch on the mosture retention.
Great ideas. Thanks again!!

M42powered

Posted Monday, Jan 24th 11:10pm [Edit] [Quote] [IMS] [View car]

Staff
Post nr. 434

Arizona, USA
1981 BMW 320i

The best and cheapest way to get that body stiff is to weld the doors shut. Kind of sucks for entering and exiting, but will definately tie the whole body together. Besides seam welding the only real way to stiffen the chassis is to triangulate the shock towers together some how. You could do a low profile cage that sits below the windows down the length of the car. Another idea would be to just reenforce all the mounting surfaces. Rear subframe, shock towers, front subframe. A good bit of chassis flex can be attributed to where the suspension mounts to the car. Other than that, you'll have to build a cage.

David_in_Golden

Posted Tuesday, Nov 20th 10:55pm [Edit] [Quote] [IMS] [View car]

Junior Member
Post nr. 3

Colorado, USA
320iS

I am designing Sub-Frame connectors for my car, the rear section has to be removable to access the gas tanks but I think I have a design that will help stiffen the chassis. has anyone tried this?

DVD