s38 motor and flex - who knows?

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mark

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hi guys

i have been dreaming about a s38 motor e9 project for a long time. in reading what i can from this site and elsewhere, i see that many of you are of the view that the e9 body will have some trouble standing up to all the horsepower/torque. and that the csl race cars were stiffened up relative to the ordinary line cars.

i am completely ignorant as to whether it is feasible (as i said, i have just been dreaming).

but i have now been offered a v.good deal on the motor and gearbox of a low miles 3.8l m5 (the 340 hp s38 motor).

i like, no love, the idea of a more or less standard looking car (not my csl)with this engine.

can anybody help me with some thoughts? i need to answer up on the motor on monday.

thanks a lot.
mark
 
That is a very nice motor. Just make sure you get the whole package, like the harness, DME, sensors, everything.

Based on corsachili's build up, you will have to pound out the firewall a bit to fit the S38. As to the exact amount, he'd probably know best at the moment.

As for the frame, a competent race shop should be able to reinforce the chassis with a minimum of fuss, possibly with a roll cage. The chassis structural strength is a general unknown, as nobody want to put in a fire-breathing monster only to have it take off while the driver and the body are left behind. Based on metal behaviours, the frame has probably lost a significant amount of strength since it was made, due to fatigue and thermal stress microfractures.

There are some coupes running around with S38s, but I have never read about them ripping themselves to shreds due to the motor. Come to think of it, there is a scanned article on a very nice S38 E9 build in the tech section of this site.
 
I am in the process of swapping out the M88/3 engine in TBL for an S38 and am discovering that even though they are the same engine family it's not a straight swap. To go from an M30 to S38 can be done, will not be easy but in as much as you are getting a deal on the parts, buy 'em and if you decide later not to do the engine exchange, you can always sell the stuff. (pic of M88 in TBL http://bmwbatmobile.com/_wsn/page5.html ) As for chassis stiffness, it's not so much the extra power that will tweek it, but the fact that you will be driving the car with much more gusto that might bring flex into play. A four point roll bar will help quite a bit with chassis stiffness but will, however, make the back seat all but unuseable. A six point cage would be even better. All that said, I don't know if any of the coupes with M88 or E38 engines have cages or bars. There are some people on this forum that drive four cam coupes and hopefully one of 'em will show up to refute everything I've said. Hey Dan K and Peter S, what's your two cents (ummm, that would be four cents) on this?
 
Mark,
The e9 shell has the torsionally rigidity of a cardboard box!
To stiffen it you will need to seam weld the whole of the floor pan and add a roll cage, a "weld in" 16 point cage would be the ultimate plus, at least a strut brace at the front

Its a lot of work (read money!!!) to turn one into a compeditive track racing car.

Remember when BMW built the cars for the European touring car championships in the 1970s' to compete with the Ford Capri RS 3100's they were concidered "disposable" ie the life expectancy was very low, about a season, assuming they car was not crashed so if they started to break up the shells were just thrown away!

So if you want a car that will last a while then please concider the above
Good luck
Malc
 
This S38 M88 and various variants there of keeps coming up . . .

There are numerous street E9s with this level of power, unfortunately very few get driven to their full potential, and the rest are garage queens, sorry, I need to call it as I see them.

And I respect those who have invested the time and monies to build a car of this nature, and can sometimes understand why the aren't D R I V E N!

So what if you wanted to build an E9 with real M power . . what would it entail???

Chassis stiffness
Bigger brakes
Stiffer suspension and bushings
Seats and harnesses

The latter 3 are easy, the first is hard for a street driver. Full roll cages are dangerous on the street, and a 4 point rear roll bar will only add minimal stiffness where it's needed.
What the chassis really needs is seam welding, starting with the front fenders off the car, and some critically placed reinforcements in the front structure. Rocker panels should be seam welded, and possibl have an internal structural beam added to tie the A pillar to the rear subframe mounting points. Front frame rails could be tied into the rocker panel structure as well.

Seam welding , or stitch welding an old chassis is hard, you have seam sealer, and paint that needs to be completely removed .. and then all welded areas need to be treated to avoid rust and the resealed and painted. Front fender removal is pricey, and not for the home builder.

You really want to do this, find a rust free coupe and start with that!
IMHO building an M power E9 for the street is like bigger implants on
Pamela Anderson ... . you can buy a nice CSL and have a car that appreciates in value for the same monies . . .
 
There are numerous street E9s with this level of power, unfortunately very few get driven to their full potential, and the rest are garage queens, sorry, I need to call it as I see them.
Click to expand...

I totaly agree with this statement.


Full roll cages are dangerous on the street
Click to expand...

But I'm a little confused by this statement, why do you think that full cages are dangerous? I'm currently restoring my CS and I intend to fit a full cage when it's done.
 
A full cage, although it adds strength in a car, also makes the potential for injury to the body much higher.

The stiffer the chassis the less energy it can absorb before the human body impacts the structure. A good crash worthy car for street use is designed to be structurally stong and incorporates collapsable crush zones away from it's passenger compartment to absorb impact energy. Contempory cars use air bags, dashboards completely made plastic, etc. A CS has none of this.

In a car the human body will bend, flex stretch and ultimately contact a roll cage with out the protection of a helmet or 5 point harness and race seats, much less a Hans device.

Please also consider that a full roll cage installed within the passenger compartment and will be on average 2 inches closer to the head and torso with rigid impact surfaces. Add SFI padding and you are now moving these surfaces another 3/4" closer to you. SFI padding is designed for helmets . . not the skull!

If you make a close inspection of a race car there's lots of padding and safety items installed around the driver, safety nets in windows, etc. All this padding will resrict visability for street use. A street driver needs a greater field of view around is car than a track driven car . . IMO, hard to understand untill you have driven race cars in race conditions.
 
Got ya. I'm well aware of the issue with crumple zones I just didn't understand what angle you were coming from in your statement. While I agree in principle with what you are saying I feel that its probably less of an issue with older cars like the CS as they probably didn't have crumple zones designed into the body back in th 60s.
When my car is finished I'll be fitting harnesses also.
Regards
 
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