M20 B3x Naturally Aspirated Stroker build past, present and future

[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

[digger]

Awesome read Digger! I was the one emailing you not that long ago - I have an almost identical 325iS with M20B31 in Sydney.

I think I will be speaking to Rama in November when he is back in the country about ITB's.. He installed an EMU for me a few months ago.

I only made 143kw ATW at port hacking auto which I was a bit disappointed with but there is always room for improvement!

hi nick, i remember any progress....?

[digger]

I dont really understand why your saying alpha-n doesnt have enough info for the engine or is hard to tune? The only thing it cant do is compensate for atmospheric pressure or altitude but most stand alone ecu's have a function for exactly that. But at the end of the daty the difference it makes is SO small its hardly worth turning on unless you plan on going to relly high altitudes, and could be quite easily enabled to get pretty close with a couple test drives and AFR meter etc.

Your factory one..... of course i can understand its not going to work well because your primary load sensing device is still sitting on you workbench! :nice: which is testament to the motronic that it even runs well enough to drive at all!!.... on what is maybe a limp home mode???

An aftermarket ecu on the other hand can be well tuned using Alpha-n very easily, my tuner loves them! because he can access the whole map and simply run up all the load bands on the throttle pedal with perfect stability and no jumping around. Temp, ASE and other compensations need to be set up but no different to speed density etc. Maybe on an inertia dyno it might be a PITA but I havnt heard of anyone who uses one down here.

I can down load my datalog and my AFR's pretty much draw a straight line from one end to the other. I know its a race car but i drove an alpha-n tuned road car for years too, again cold hot winter summer never worried it. I never used atmo comp or closed loop, which would certainly take care of any little inconsistencies if you were really worried.


Edit: .. Actually Digger you car is a daily driver and has been Alpha-n for a while now, line any tune it always takes a bit of refining, but how has it been to drive around?... compared to speed/ density?
and its an ECU thats not all that good at holding a tune particularly stable i found.

somehow i missed all this.

it drives alot better on alpha-N and ITB than ever when its tuned properly, the only downsides so far is fuel economy by 10% ish but then again with small exhaust leak tuning to O2 at light loads in open loop will be affected by false reading and it will run richer than optimal so i will reserve judgement to when fixed. might be that i use a bit too much throttle now ;)

[AussieTemplar]

Awesome read Digger! I was the one emailing you not that long ago - I have an almost identical 325iS with M20B31 in Sydney.

I think I will be speaking to Rama in November when he is back in the country about ITB's.. He installed an EMU for me a few months ago.

I only made 143kw ATW at port hacking auto which I was a bit disappointed with but there is always room for improvement!

[nando]

Digger's running standalone though. Motronic wasn't really meant to run Alpha-N in anything other than a limp mode. I'd bet Digger's ECU is 10x faster than Motronic was.

[e21jps]

Yup. I tune on DynoJet, it has load capability. Makes it nice when you can hold an RPM/speed and get the map to stay in the block. Makes over all tuning better, but as you said, light throttle/cruising may need some touch up. I tend to do it just opposite. Tune for idle, light cruising/drive ability, then go to the dyno to brush it up and do a power tune. People keep asking why the 24v ITB's weren't on the dyno yet, but wasn't easy to get the stock Motronic to behave. Would be good for light load in one gear, then if bogged a little more than normal in the next the AFR's where everywhere. Had to find a balance, now I see why everyone wants so much for Alpha-N tunes, RPM and TPS aren't enough info for the ECU in reality, so it just takes time.

I dont really understand why your saying alpha-n doesnt have enough info for the engine or is hard to tune? The only thing it cant do is compensate for atmospheric pressure or altitude but most stand alone ecu's have a function for exactly that. But at the end of the daty the difference it makes is SO small its hardly worth turning on unless you plan on going to relly high altitudes, and could be quite easily enabled to get pretty close with a couple test drives and AFR meter etc.

Your factory one..... of course i can understand its not going to work well because your primary load sensing device is still sitting on you workbench! :nice: which is testament to the motronic that it even runs well enough to drive at all!!.... on what is maybe a limp home mode???

An aftermarket ecu on the other hand can be well tuned using Alpha-n very easily, my tuner loves them! because he can access the whole map and simply run up all the load bands on the throttle pedal with perfect stability and no jumping around. Temp, ASE and other compensations need to be set up but no different to speed density etc. Maybe on an inertia dyno it might be a PITA but I havnt heard of anyone who uses one down here.

I can down load my datalog and my AFR's pretty much draw a straight line from one end to the other. I know its a race car but i drove an alpha-n tuned road car for years too, again cold hot winter summer never worried it. I never used atmo comp or closed loop, which would certainly take care of any little inconsistencies if you were really worried.


Edit: .. Actually Digger you car is a daily driver and has been Alpha-n for a while now, line any tune it always takes a bit of refining, but how has it been to drive around?... compared to speed/ density?
and its an ECU thats not all that good at holding a tune particularly stable i found.

[MPLFoster]

sub'd

incredible work.

[LJ851]

bump

[digger]

Where'd you get this beauty from?

burns stainless