M20 B3x Naturally Aspirated Stroker build past, present and future

[QuiqueUy]

thats amazing , great work! i was wondering how's the relability of the engine by stroking it to 3.1 since i don't know about this and in my country no one has done it because this factor that we don't know :p the life of the engine might be lower right? keep up the amazing work!

[digger]

hit an unrelated "snag", will reveal more when i am able

[Nutzy]

Yah man, post some dyno vids or something!

[LJ851]

How is this progressing, digger ?

[Mfever]

Any sound clips of new exhaust?? Looks pretty damn badass!

[digger]

it was simply too short/close for the rpm i was using.

[CorvallisBMW]

Wow, I wouldn't have expected x-pipe placement to make such a difference.

[digger]

i have moved the X-pipe from 4th to 3rd harmonic and it seems a positive move.

The AFR or timing has not been adjusted at all and you can see that the engine runs alot leaner in parts now and make alot more power in midrange as i was hoping and no loss of topend hp.

i will get it properly tuned in the next couple of weeks and will update as i imagine there will be some additional gains from a tune



im not sure why the operator ran it from such a low rpm but 100km/h is 3400rpm so the peak torque is 220twq 4200rpm give or take and hp 224whp 6100rpm

[The Dark Side of Will]

i still have to tune the front to rear with sway bar settings by adjusting the front. anyone know the difference in % stiffness by using the strut pickup vs control arm?

Mechanical advantage is the relationship of the length of the lever with the load to the length of the lever with the force.

The load is at the ball joint, the force exerted by the sway bar link.

The relationship of spring rate to wheel rate is the square of mechanical advantage (really it's the motion ratio multiplied by the mechanical advantage, but motion ratio and mechanical advantage are the same in most cases).

So if you have a mechanical advantage of 0.8 (spring acts at 80% of the distance from the inner ball joint to the outer), then the rate ratio is 0.64. A 100 pound per inch spring would result in a 64 ppi wheel rate.

[digger]

that's quite a dramatic effect, im wondering if it might be too big of a jump? i have a 16mm rear bar on middle setting and it feels quite a bit stiffer in the rear than the front especially when you turn in at speed. The front is hollow 25mm on the softest bar setting.

maybe its worth trying something more subtle to start so going to the next setting on the bar.

[tinkerputzer]

Found this:

http://www.r3vlimited.com/board/showpost.php?p=3185991&postcount=10

IMO to dial in suspension you kind of just have to get a feel for what the car is doing and adjust from there. If the car is a little pushy and has a tendency to understeer use a little less front bar or a little more rear bar. If you are getting too much rear rotation use less rear bar or more bar in front.

[digger]

my WB doesn't work at the moment, i will be sorting it out in a couple weeks though.


i still have to tune the front to rear with sway bar settings by adjusting the front. anyone know the difference in % stiffness by using the strut pickup vs control arm?

[tinkerputzer]

Looks great digger :up:

Can't wait to see the dyno validation. If you can get some readings with your wbo2 sensor you'll know it's working the way you want if it's running a bit lean due to moving more air. I know you already know that though.

Good to hear you got you suspension sorted out.

[digger]

Exhaust has been done....... ;D

I forgot to take some proper pics while it was on the hoist as it was late on Friday afternoon when I picked up the car.

Here is the BEFORE pics





Here are the AFTER pics







I ended up just getting the X-pipe moved downstream and re-configuring a few things, and stayed dual pipes rather than re-configuring to a 3” exhaust. I wanted to keep my existing twin muffler and prefer the sound of twin pipes.

The exhaust changes are as follows:

1) Collector Length changed to from ~400-420 mm to ~800-850 mm long. Basically I doubled the length from the end of primary pipes to the expansion of the X-pipe
2) New Burns X-pipe 2 x 2” in with 2 x 2-1/4” out. Previously it was BTB X-pipe with 2 x 2” in and 2 x 1-7/8” out.
3) 2 x 2-1/4” high flow metal cats and vibrant bullet resonators
4) All pipe work post X-pipe is 2-1/4” previously it was a mix and match crush bent.

I’m very happy with the work, it turned out quite a bit better than I expected, all mandrel bends stainless 304 nicely TIG welded. It sounds really good you can hear the exhaust “working”.

Seat of the pants feels like midrange has again returned with a vengeance which was the whole idea but the dyno will have final say.

It will be interesting to see how the power and torque curve have changed as I think it will be quite a dramatic difference. i imagine it will need a decent remap to get the most from it based on the level of change when it was moved back in 2012
I may do a quick power run untuned at the end of the week if I can get some dyno time as a proper tune is several weeks away yet.

[digger]

ive been busy doing suspension that's why it took so long

REAR:
all rear bushes done
GC 475lb springs
koni SA (top)
GC RSM
reinforced TA tabs (turner)
reinforced rear sway mounts (IE billet)

All front bushes done except tierods which are relatively new

FRONT:
GC 375lb springs
sectioned housing
koni SA Top
GC street camber plate

rides excellent and handles well

All other bushes are OEM rubber except for sway bar bushes which are poly

exhaust is done will start to do a writeup soon....no dyno results yet though