Turbo setup questions...

[E30godz]

yes i know how an AFM works.

did i miss something?

http://www.bmwe30.net/cgi-bin/datacgi/database.cgi?file=articles&report=view&ID=00056&Section=15

look at the AFM....why wouldnt the AFM just blow back to being completely open under boost?

[Matto]

It sure does look like the afm would just blow back with any kinda boost.

[Kavkazia]

Why the AFM seem to go bad faster when it's after the turbo? And not before turbo? Any profesionally built turbos run AFM before turbo!

You might be alright under low boost, but once you start running high boost, and that pressure hits it, you'll know what I'm talking about.

[skat 325is]

I think the least it could happen to the AFM is the black plastic cover outside would blow out of its place and fall in the road. The worst it could happen is the sensor inside the AFM would die sooner.


Just my .02

[diegom6]

Why the AFM seem to go bad faster when it's after the turbo? And not before turbo? Any profesionally built turbos run AFM before turbo!

You might be alright under low boost, but once you start running high boost, and that pressure hits it, you'll know what I'm talking about.

TechnoS50 or Tech550 a member of Bimmerforums did it...he knows a lot of turbo and turbo tricks...he was using before in his 525i (m20) and the moved to "after" and he felt the engine bit better...

[hotghias]

I, too, have never heard that presurizing the afm would cause the flaps to break apart.

i read some speculation that putting it after the turbo makes it work differently in this way: before the turbo, the flapper door bottoms out way before redline due to the boost causing such high volume of air to be sucked past it. but when it is placed after the turbo, it doesnt work like that. when under boost it doesnt bottom out as early because, though the intake charge is denser and has more air molecules, the volume of air passing the door is nearly the same as if it were not on boost for a given rpm. the pressure one side of the afm is equal to the pressure on the other side, minus the drop caused by the ineffiency of the restriction, which is present NA or turbo. makes sense to me.

this leads me to believe that when using an FMU, placement would be better after the turbo. if the afm is before the turbo, keep in mind that the door will be wide open relatively soon in the rpm band due to boost, meaning the computer will be giving the injectors all they can give, as well as the FMU giving it the max pressure. seems like this would cause a rich condition at midrange that would be unavoidable unless you want to lean out near redline (boom). whereas if the afm is after the turbo the computer would be giving the engine the regular ammt of fuel for that engine speed, then the FMU would compensate for the extra air needed by boosting.

you'll have to correct me if i'm wrong there. my knowledge of fuel injection isn't that great, but i'm sure there is some validity in the above. and if i'm talking out my ass, cut me some slack. i don't own a bmw, or any car with fuel injection- '71 vw karmann ghia, baby, but i want to get an e30 someday.

but back to the topic at hand, unless you are planning on running really high boost or low quality fuel, i don't think low compression pistons are necessary. if you have that money laying around, invest it in really good tuning. the stock compression ratio is 8.8:1, which is a good number for boosting. lower than that risks turning your motor into a slug off-boost. by the way, i've heard bad things about thicker headgaskets. plus, it's relatively intuitive that the gasket is weaker than the aluminum head or the cylinder walls- why put two in or one thicker one?

[E30godz]

TCD has his afm pre-turbo with great success, and is running a rising rate too...crazy AFM's ; )

[dolphinblueE30]

hey how much would it cost to drop a good turbo in A E30 ?

[skat 325is]

hey how much would it cost to drop a good turbo in A E30 ?

i would say $1,000 - $3,500, i lost count on mine...mine was around 2,700 or so

[325is_e30]

what specifically is everything you need to make a basic setup ($1000-$1500)??

[E30godz]

turbo
oil feed/drain lines
exhaust manifold
charge pipes
fuel/ignition managment
new exhaust once turbo is built
boost gauge.
various fittings and hose clamps

[Hortos]

Fun with junk

$75 from Wrecking yard Toyota CT26 turbo its bigger than my friends $300 T3/T4 I lucked out and found one with no shaft play.

$30 sawed the two flanges off the bottom of a 325i exhaust to make a turbo adapter.

$FREE Starion Intercooler that mysteriously sailed over the wall at a local junk yard. To this day I don't know what happened <Word on the street is this is too small for my turbo so I'm looking for the supra the turbo comes off of>

$40 Mustang 19lb injectors

Now I need piping. I'm thinking about maybe 1 1/2 inches to my intercooler and then 2 1/2 out of the intercooler.

FMUs and SMTs to be determined.

[E30godz]

just use 2 inch all the way around

the turbo isnt "too big" for the intercooler, it depends on how much boost your running.

you sawed off the flanges of the stock manifolds? You plan on welding to cast iron?

[Hortos]

lol

My bad they said it was the DSM intercooler off the eclipse it would choke on anything more than 7 PSI from the CT26.

And we're only using the flanges as guide to make sure the one we make fits on my car. I could just jimmy rig around witht he ones on my car but I don't want to mess with them.

And I thought if you run piping thats bigger than the outlet of the turbo it'll create more lag. And then larger pipe after the intercooler for the high pressure to low pressure effect.

[decay]

Re: Fun with junk

$75 from Wrecking yard Toyota CT26 turbo its bigger than my friends $300 T3/T4 I lucked out and found one with no shaft play.

toyota used more than one config of CT26.

for an m20b25, *make sure* you're getting one from a Supra, and not an MR2 or Celica.