Handling with 24v swap

[ed94r]

I could feel a difference in how quickly my car changes direction after removing the A/C. I am doubtful it has any measurable impact on total cornering grip. I am basically trying to come up with a list of reasons why NOT to S5x swap.

Not being able to use my UUC shifter, and megasquirt PnP (future purchase) kit are two of them. I was hoping that the consensus would tell me that a 24v swap turns it into an understeering pig-dog so that I could get the thought of a swap out of my head for good :D

I'll stay out of this thread after this...

What class are you running? Where are these "changes in direction" occurring? Why would someone be so tied to balance as to make it real decision? Unless you are running a specE30, SCCA solo stock, STX, DSP, etc. (M20 only classes)....there really is no question. No comparison. Being a purist is the only good reason to keep the old lump..but that's it.

[02stu]

I felt a huge difference in how tossable the car was (coming from an m42), but the overall handling was just as good.

[hoveringuy]

M54 Aluminum goodness. 'Nuff said.

[Sagaris]

As an automatic (currently in the middle of a 5spd swap) my car weighed in at 2720 lbs with A/C removed, half tank of fuel, no driver, and a weight bias of 53.4/46.6. My car has a tendency to understeer when approaching the limit which I would like to remedy with better static weight balance first before tuning the suspension, alignment, tires, adjusting roll centers, and so forth.

I do not race but I will be starting some track driving instructions and HPDEs this year. Most people who do not race competitively don't and probably shouldn't focus on such minute details, but I am an engineer and therefore somewhat OCD, and I have found such attention to detail to be very rewarding and something to do to keep my hobby entertaining and challenging. My ultimate goal is not to have the highest performing car, but to have the one that is the most enjoyable to drive, and to me that means achieving great handling, balance, and response, while maintaining comfort. Something that is much easier to achieve when the car is in balance.

[VinniE30]

It's simple - increased weight at the nose of the car is bad for handling. The iron block e36 engines will increase this weight at the nose of the car and it will increase in worse handling. Weither or not you notice it is subjective and varies from person to person but it is there.

[VinniE30]

My car has a tendency to understeer when approaching the limit which I would like to remedy with better static weight balance first

You will not help that with an iron block 24v engine. An aluminum one will however give you better weight distribution.

[Leo_328i]

One minor but interesting engineering difference between the 24v motors and the M20 that no one has mentioned is the fact that the 24v engines are cantered over 30 degrees and the M20 sits more upright at 20 degrees tilt.

I'm not sure how much lower/higher an M50 sits in an E30 engine bay with the usual E36 engine arms and E28 mounts compared to a stock M20 but it would be interesting to look at the differences - surely it would be very similar?

If they sit at roughly the same height the M50 would have a lower centre of gravity due to its greater inclination.

[VinniE30]

One minor but interesting engineering difference between the 24v motors and the M20 that no one has mentioned is the fact that the 24v engines are cantered over 30 degrees and the M20 sits more upright at 20 degrees tilt.

I'm not sure how much lower/higher an M50 sits in an E30 engine bay with the usual E36 engine arms and E28 mounts compared to a stock M20 but it would be interesting to look at the differences - surely it would be very similar?

If they sit at roughly the same height the M50 would have a lower centre of gravity due to its greater inclination.

Not necessarily. You're not taking into account the fact that the center of gravity (center of mass) of an m20 is lower than a 24v because of the big heavy DOHC head vs the m20's lighter head.

I completely understand what you're saying but I think the DOHC engine would have to sit significantly lower in the bay for it to make up for having more weight at the top of the engine than the SOHC head engine. Only then would it in fact have a lower center of gravity.

[Wh33lhop]

Yep, there is a reason they went with a 30 degree slant on the 24V motors, and that is that the head is hyoooge and they needed more space.

That said, I doubt you will notice much of a difference if any. Yes technically the handling will be worse and less responsive, but the power increase is worth it, especially if you're doing an S5x. It will be no M42/S14 in the handling category however (although it will smoke them on a track).

[Leo_328i]

Fair call with the 24v head guys. You're bloody right about the 24v head being massive, its extremely awkward doing a head gasket on one.

If you want to try and assist the front weight distribution you can swap the G260 for a G240 gearbox which is lighter? I've never picked up a G260 before but I've carried both a ZF 5-speed and a G240 - there is a HUGE weight difference between those 2 gearboxes!

Feels like around 15kg difference just by judging by how much heavier it feels.

[Jason89i]

......my car weighed in at 2720 lbs with A/C removed, half tank of fuel, no driver, and a weight bias of 53.4/46.6. .

here are some comparisons.

http://www.r3vlimited.com/board/showthread.php?t=90486&highlight=weight

yes, you will notice the difference on track. i've had a few swaps. tracked them all.

do you plan on attending the badger bimmers blackhawk? cheers, jason

[Sagaris]

here are some comparisons.

http://www.r3vlimited.com/board/showthread.php?t=90486&highlight=weight

yes, you will notice the difference on track. i've had a few swaps. tracked them all.

do you plan on attending the badger bimmers blackhawk? cheers, jason

Yep, I haven't signed up with them yet but I am on-board to run blackhawk on the first track day in April and hope to get as much track time as I can during the warm months.

Thanks for the great link!

I am surprised to see the the weight distribution in the 91 318is with the alum. m52 and full tank of gas isn't too much different than the iron block cars.

For the record, I also have trunk tar removed and a bit of forward rake due to the suspension setup. I did the calculations after I got home to see how the weight distribution changes with me in the car and it helps even it out a bit. I should be able to get near 51/49 with me in the car, a full tank of gas, and the weight reduction from the 5spd swap but I will be putting it on the scales to check when its done

[VinniE30]

I am surprised to see the the 91 318is with the alum. m52 and full tank of gas isn't too much different than the iron block cars.

That is a terrible comparison if you want to just compare the difference in engine weight all else equal. It's a terrible comparison simply because the engines are in different cars. Just the difference in the weight of vaders vs "light floor mount seats" in the aluminum m52 vs the s50 would be a big difference in weight not to mention any other info they are leaving out.

There's no sense in doing a comparison like that for the purpose of comparing the weight of the engines. Compare the weight of the engines by themselves...

M50 = 436 lbs
M54 = 375 lbs
That's a 61 pound difference at the nose of the car!

http://www.usautoparts.net/bmw/engines/m50.htm

http://www.usautoparts.net/bmw/engines/m54.htm

Those are the official weights reported by BMW.

[Sagaris]

I should have been more clear, my mistake. I meant that the weight distribution isnt too much different for the alum. block car than for the iron. block car.

I see how it could be understood that way... brb editing post :D

[hoveringuy]

m50 = 436 lbs
m54 = 375 lbs
that's a 61 pound difference at the nose of the car!

I really felt the difference when I switched from the M50 to the m54. I remember that I measured my front ride height before the swap and a few days after and it was definately higher.