I did a search and didn't find anything specific.

So I was wondering if anyone has successfully run ITB's on a R53. I know the SC isn't necessarily conducive to a quick install, as the system needs to be holistically built, but was hoping someone took this task on.

Thanks!

 

i doubt it, i bet the NA guys have run them though.

to realistically run ITBs and forced induction on a R53 you would have to go turbo. there just isn't enough room to do all that. infront.

 

Sounds like a lot of money and headaches for probably not a lot of gain, if any,

 

Soccerbummer on here is planning on running ITB's on his build.

https://www.northamericanmotoring.co...d-updates.html

 

news to me! but I am excited! haha. jk.

No ITB here (yet). I am running a 76mm throttle from a '07 330i and its a pull through setup on a turbo (exact same setup " path " as stock except stuff is relocated and the compressor is a turbo instead of a supercharger)

That being said, if my throttle volume is too large I may do ITB's... but that requires going to a completely different type of throttle setup. (and possibly running a throttle cable and different pedal in the cockpit)

For the stock ECU I would say it is more trouble than it is worth.

For those like me that have stand alones it is just a matter of want, money, and time, the last two not being that bad, but still factors.


What I was planning on eventually doing ( which you may have confused) was running sequential ignition instead of wasted spark.

idk if I am still going to carry that through, but I have the ignition modules



Also!

you most certainly CAN run a supercharger with ITB's,
but! you would have to have your map sensors inside the runners (say whaaa?!) where they would see a lot of pulsing, which is altogether why speed density (the way ours is set up... ish...) is NOT used for ITB's. it is unreliable as a clean pressure signal representative of air going into the motor is not really possible.

Most of the time on ITB, an Alpha N - hybrid type tune or a MAF sensor is used (maf is easier and more reliable imo)

So this all together would be another headache to get around.

but as for running a supercharger with ITB's, that is easy. You run it the exact same way you run a turbo, but you use a very low weight spring in the blow off valve and have a reference line to hold it closed when the throttles are open (basically activates the boV/bpv when there is a delta of 2psi across the throttle or so.

 

Damn, I could have sworn you talked about putting in ITB's.

 

Electronic TB prohibits ITB's on an R53, not to mention clearance issues as others have said. Additionally, seeing as though on the R53 the ETB is on the inlet of the blower, not the intake manifold itself like most "normal" cars, how would you even build an ITB set-up? You'd need a custom plenum that mounts to each ITB and some elaborate linkages, me thinks.

In my mind, installing an ITB system that requires an additional plenum / piping, negates the whole purpose of ITB's (improved throttle response & lessened restriction). Also, SoccerBummer is right-on with the tuning woes; attempting to tune this via Speed Density (instead of MAF) would be troublesome. TPS based fueling is an option, albeit a very crude one. Megasquirt could be used to tune via TPS at low-throttle, and switch to MAP at WOT or when under boost.

If you want ITB, go buy an AE86 and be somebody

 

well a new plenum is a given, but it would be possible with an E-throttle.

you would have to essentially make an entire new intake manifold with a bolt-on plenum.

The throttles would be at the inlet of each intake runner, and would share a common shaft that the throttle plates were all bolted to and on one end you would have an E-throttle controlling their position.

Best way to do the fueling would really be with a MAF sensor on the inlet to the plenum, and have the BOV in front of the MAF, recirculating to before the SC or dumping to atmosphere (again, 2psi spring), but it is still difficult to get that referencing quite right due to the sinusoidal pressure waves in each of the runners.

source: currently working through these headaches on a ITB factory car that we are putting a turbo onto.

 

I get why you'd run a blow-through MAF setup, but am not understanding why you'd be getting such disruptive pressure sine waves in the runners.

Are you building an MX5, or some type of BMW?

 

its a BMW. not allowed to disclose what at this time, but it is special

Car was originally at FMU (fluid motor union) but they did some things just... wrong.. so we are re-doing them (the owner and I and a few other of our car buds. divide and conquer)

the sine waves in the runners would be a problem all of the time, but definitely at part throttle and idle when the throttle valves are partially, or completely closed.

you *might* be able to get by with it at WOT conditions, or tuning around it (hybrid alpha N - basically alpha N with a pressure sensor) to make it work, but MAF is easiest.


You have to remember that air is a compressible fluid, and an engine is a dynamic system.

each runner connects to one cylinder, and on a 4 stroke motor, it will be only "pulling in" air through the runner 1/4 of the time, and that pull is not even linear due to cylinder fill, exchange, ram effect, the list goes on and on.

Pressure waves are why ITB's give better throttle response (engine is always pulling the same volume of air, but only responds as fast as it can consume air between the intake valve and the throttle and see a change in pressure. The more volume, the slower the rate of change)

in an ITB, the throttle shuts, and the engine idles down much faster due to the small volume of air.

Open the throttle and revs go up quicker (response time) due to the pressure wave from the outside @ 14.7 psi reaches the engine sooner as it starts from the itb and not from the single TB located next to the air filter (like our cars)


This actually encompases the only problem with the setup I am working on for my car (pull through setup on a turbo) as my throttle volume is increasing some, and if it gets too large, the ecu will have a difficult time controlling revs at idle due to the slow response of the system (may have to change PID controller settings on the throttle and decrease the gain and deadband)


anywho,

To illustrate the finite details, and really get down to what you asked I guess, you have to realize that when the intake valve opens and the engine starts pulling in air, it creates a pressure drop at the valve. This pressure drop then pulls air from the incrementally-further-away piece of air in the runner, and causes it to flow towards the valve, creating a pressure drop where it resided, which then pulls from the incrementally even further away section.

AKA, each time the engine intake valve opens, a wave of pressure flows up the runner, and air moves towards the cylinder.

Then when the valve closes, the air is still moving towards the cylinder (it has kinetic energy) and some of it hits the back of the valve. This causes a spike in air density (increase in pressure) which then flows back up the runner towards the plenum.

This is universal for ITB and non ITB setups.

now (simplifying grossly) on an ITB, this pressure wave does not propogate into the plenum (again, simplifying, it does, but the magnitude is much much less) but is contained in the runner.

In this case, when the first wave (the negative wave) reaches the throttle plate, it pulls air from behind the throttle in an effort to place the plenum and the runner in equilibrium, but the waves are (for the most part) contained within the runner, and the plenum could be a much higher pressure than the runner on the negative wave stroke, and lower durring the returning pressure wave when the valve closes,

At any rate, air is constantly moving in and out and around in the runner due to waves of pressure, which a good map sensor should pick up if in the runner.

and seeing as it is cyclic, the waves should look sinusoidal with a period equal to 1/(engine RPM/2)

In a non itb setup, these waves do propagate into the plenum, but due to the multiple cylinders in different phases, there pressure waves all combine and smooth out by the time the "signal" reaches the sensor at the plenum entrance, so the signal car receives is nice and steady, and not all over the place. (same reason why our map sensors are not in the runners and at the inlet to the intake manifold)

Tried to simplify this as much as I can, but it is difficult if you do not already have a fluids background and an understanding of engine dynamics (and me not in a room with you drawing on a white board)

 

Thanks for that explanation. I was thinking that air reversion caused by different variables (namely, valve and throttle plate movement) is what you were referring to, but wasn't 100%.

I'm an Engineering Technician at GE Global Research (Aero and Mechanical Systems), so I do have the background and understand, but it's always nice when someone can help draw a mental picture as it applies to a car's engine of which I'm familiar with.

I bet your project is an old M6...