How do engine and chassis changes affect performance on the track and on the road?

[pbondar]

I, like many before, have changed many aspects of our cars, with a combination of cosmetic, functional, handling and powertrain modifications.

The question I'm asked and I ask myself is how do these changes impact on the 'performance' of the car.

So what I've done for both Z4 E89s I've owned is try and chart the broad impact of the powertrain and chassis modifcations in three scenarios, two theoretical, short and long track and one real, fast road use.

The changes didn't actually happen neatly sequentially but I've grouped them together for simplification.

The theoretical versions for track use place emphasis on things that are not as relevant for road use eg powerful brakes rather than say softer long travel suspension is not relevant for track use but important for use on public roads.

Its one man's view, and based on my type of driving (probably described as upper quartile driving at speed) on open, uncongested, derestricted roads that we in Scotland can enjoy so much.

I've compared my 2012 20i MSport Auto against my 2011 35is.

Enjoy!

 

[SlowE93]

Is this a rhetorical question ?

 

[pbondar]

Is this a rhetorical question ?

Yes it is..but the question is what are the quantum for each change ….

 

[Torgus]

These charts are just made up using your own made up data? Like you just arbitrarily assign points to categories based on your feels?

What is the other Axis? Total pbondar points?

How is an N20 faster than an n54 stock? How is an OTS tune N20 faster than a OTS tuned n54?

Going Big single turbo gives you a tiny bump over the n20? No offense but the N20 is meh. I've been in a awd auto coupe with the N20 and holy shit it was slow.

Run flats to non run flats are a HUGE jump in the chart but adding a tune does almost nothing? A tune wakes the n54 up big time. ~275whp to 375 whp on 93, much more on E85 OTS tune.

It's a 1.8-2.0 single turbo vs a 3.0 twin turbo https://en.wikipedia.org/wiki/BMW_N20

The n20 replaced the NA N52. It makes roughly 50whp/50wtq less than the n54 stock.

I don't get your charts man?

 

[wheela]

I'm also not sure how to interpret these graphs

 

[SlowE93]

Good! So it's not just me

 

[pbondar]

So what I was trying to encapsulate is how does the car feel when driven moderately quickly over say 200 miles in 4 hours over a mixture of fast, open, twisty, bump roads.

Its not how fast it launches off the line with a quick 1/4 mile dash.

In that 4 hours, how comfortable we’re you driving that car, how fast did you feel you could extend the car without feeling scared , strested etc..

Then taking into account the 100 plus changes (in the case of the 35is) and a lot less but still touching all the key ares, how much ‘better’ did the car feel as a result of those changes.

For example changing from runflats to non runflats had just about the single biggest impact on the behaviour of both cars.

When both cars were stock apart from non runflats the N20 would leave the 35is way behind over 2oO miles.

The 35is was slow to turn, ponderous, poorly damped, undersprung, with vague steering and a lack of communication about what was happening on the road compared to the identical N20 powered car.

Its power advantage was negated by the fact that it then had to be hauled down on its brakes, wobbling and feeling at ease on the turn in.

Yes in a straight dash no contest, on a typical Scottish road it was probably 5-10 mph slower for the same level of assurance ‘ comfort etc..

The 35is compared to my by then modified N20 was so so profoundly disappointing that for the first 5 weeks of ownership I told non of my friends I’d bought it and only after much debate decided to keep it on the basis it would be heavily modified.

I continued to run the N20 and 35is for a year , often taking the N20 out on the same roads immediately after the 35is and the 35is remained a disappointment till the middle of the year when I thought I’d got it to a satisfactory point..

The 35is as a 1/4 missile was no doubt ..as a roadster on Scottish roads a massive dissapointment.

Why?

Many factors..

Too much front end mass

Too much mass beyond the front axle

Underdamped / poor damping

Soft springs

Tired / inadequate rubber bushing in almost all steering and suspension points

Poor geometry

Runflat tyres

Too much torque / power for those components to cope with

Its a European view of driving..

 

[wheela]

So what I was trying to encapsulate is how does the car feel when driven moderately quickly over say 200 miles in 4 hours over a mixture of fast, open, twisty, bump roads.

Its not how fast it launches off the line with a quick 1/4 mile dash.

In that 4 hours, how comfortable we’re you driving that car, how fast did you feel you could extend the car without feeling scared , strested etc..

Then taking into account the 100 plus changes (in the case of the 35is) and a lot less but still touching all the key ares, how much ‘better’ did the car feel as a result of those changes.

For example changing from runflats to non runflats had just about the single biggest impact on the behaviour of both cars.

When both cars were stock apart from non runflats the N20 would leave the 35is way behind over 2oO miles.

The 35is was slow to turn, ponderous, poorly damped, undersprung, with vague steering and a lack of communication about what was happening on the road compared to the identical N20 powered car.

Its power advantage was negated by the fact that it then had to be hauled down on its brakes, wobbling and feeling at ease on the turn in.

Yes in a straight dash no contest, on a typical Scottish road it was probably 5-10 mph slower for the same level of assurance ‘ comfort etc..

The 35is compared to my by then modified N20 was so so profoundly disappointing that for the first 5 weeks of ownership I told non of my friends I’d bought it and only after much debate decided to keep it on the basis it would be heavily modified.

I continued to run the N20 and 35is for a year , often taking the N20 out on the same roads immediately after the 35is and the 35is remained a disappointment till the middle of the year when I thought I’d got it to a satisfactory point..

The 35is as a 1/4 missile was no doubt ..as a roadster on Scottish roads a massive dissapointment.

Why?

Many factors..

Too much front end mass

Too much mass beyond the front axle

Underdamped / poor damping

Soft springs

Tired / inadequate rubber bushing in almost all steering and suspension points

Poor geometry

Runflat tyres

Too much torque / power for those components to cope with

Its a European view of driving..

Wow, I wouldn't have thought there would be that big of a difference in handling between the two. Very intersting that bmw wouldn't have adjusted suspension between models sufficiently to keep feel similar across the different engines.

Now that you mention it, one time I got an f30 320i as a loaner from the dealership. That thing struck me as very fun to drive, I just assumed it was because I could keep it floored around corners without thought vs. having to activily manage throttle to not lose control. Reminded me of driving a go-cart. But now you have me wondering if there was more to my perception of how fun it was to drive. Perhaps it just handled better from less weight up front

 

[pbondar]

Wow, I wouldn't have thought there would be that big of a difference in handling between the two. Very intersting that bmw wouldn't have adjusted suspension between models sufficiently to keep feel similar across the different engines.

Now that you mention it, one time I got an f30 320i as a loaner from the dealership. That thing struck me as very fun to drive, I just assumed it was because I could keep it floored around corners without thought vs. having to activily manage throttle to not lose control. Reminded me of driving a go-cart. But now you have me wondering if there was more to my perception of how fun it was to drive. Perhaps it just handled better from less weight up front

I fully agree it’s all about perception rather than ‘facts’…..as I said I had the two yellow Zeds side by side for a year so could do direct A B comparisons..

The spring rates and damper rates were different ..but they were very very poorly matched to the weight and power of the car.

Much may have laid at 11 years and 50k miles of use…at the same point the N20 was 4 years old and 25k miles.

Almost every bush we took off the 35is when we were updating items was ‘shagged’…

My N20 use to say to me ‘that was fun, it was easy, we could have gone faster’

My N54 would say ‘careful mother fucker, push me any further and I’m going to bite..hard’

 

[SLOWESTN54]

is the M badge on the Fender factory?

 

[pbondar]

is the M badge on the Fender factory?

No…if it’s present , which it was on some versions it‘s slightly smaller and set below the side repeater….