ITB Sync

[wjtesquire]

There is a really smart guy over on mye28.com named Dean who built a Manometer for synchronizing individual throttle bodies. I used it yesterday on my M635 and it works better than I could have imagined. Here is my engine before sync:

https://www.youtube.com/watch?v=x91Dia4 ... load_owner

Here it is after sync:

https://www.youtube.com/watch?v=nINNnME ... load_owner

I am also posting the link to the original post on mye28.com

http://www.mye28.com/viewtopic.php?f=5&t=132257

He loans out the Mantis Manometer for next to nothing. Get in line, this thing is pure genius. My car idles perfectly and accelerates like I added a turbocharger. My fuel mileage has improved too.

Bill

[Carlp336]

There is a really smart guy over on mye28.com named Dean who built a Manometer for synchronizing individual throttle bodies. I used it yesterday on my M635 and it works better than I could have imagined. Here is my engine before sync:

https://www.youtube.com/watch?v=x91Dia4 ... load_owner

Here it is after sync:

https://www.youtube.com/watch?v=nINNnME ... load_owner

I am also posting the link to the original post on mye28.com

http://www.mye28.com/viewtopic.php?f=5&t=132257

He loans out the Mantis Manometer for next to nothing. Get in line, this thing is pure genius. My car idles perfectly and accelerates like I added a turbocharger. My fuel mileage has improved too.

Bill

pretty cool

but these are cheap! ive used it and its great and super cheap.

http://www.amazon.com/43-5712-Universal ... nchrometer

[GazM3]

Nice one.
You have inspired me to make a 6 gauge one. Just ordered 6 vaccum gauges and will mount them on a plate.

I have the e24 to do and they will come in useful for the dcoe45 carbs on my 2002 project.

[ericono]

Congrats Bill! Did you replace the little plastic caps when you were done?

I need to get the suspension work done on my car and then engine care is next.

Take care,

Eric

[wjtesquire]

Big E! I have had those little blue caps for years but i never felt worthy in putting them on. Now, proudly I shall mount them! We need to get together soon!

[ericono]

I understand that feeling. Congrats. You deserve it.

I agree we need to hook up. Any chance you are coming to the Euro Car Fest next weekend? BMW is the featured marque this year. I'm not entering anything this year, but will be there to check everything out. Let me know if you can make it so we can hook up.

Later,

Eric

[wattsmonkey]

I think everyone should build their own manometer at some point in their life.

I'm just worried that anyone with - I don't know - just one throttle body might feel a bit left out!

On a serious note, many thanks for this post. I'd just about forgotten about this, but I'll definitely be making one of these to sort the M out.

Rob

[Brucey]

pretty cool

but these are cheap! ive used it and its great and super cheap.

http://www.amazon.com/43-5712-Universal ... nchrometer

good for carbs and alpha-type fuel injection I am sure, but is it just me or am I the only one who can't see how you would ever use that on an M-motor with an AFM? Somehow you have the engine running with that in a bellmouth, and the AFM is still able to measure the airflow and run the engine....???

FWIW I think the manometer scheme is a pretty good one. In terms of accuracy, the manometer is miles ahead of a bourdon tube gauge; it is about two feet of head per psi on the manometer, and on a bourdon tube gauge it might be, what.... about 1/4" tops?

In fact I'd suggest that you might be wasting your time tuning the bypass screws to get that last 1" or so on the manometer; the pressure difference is tiny.

Also note that if the screws end up being set more than a fraction of a turn different to one another, this is a clear indication that the butterflies are not set correctly - or at least they are not flowing the same amount of air, anyway..... Thus if you get the idle vacuums spot on, the engine may not be running optimally just off-idle.

I dunno exactly how it works on an M-motor, but on a lot of engines the base setting for the bypass screws is (say) 1.5 turns out, and if the ITBs are 'balanced' at idle with settings that are outside the range 1.3 turns to 1.7 turns (say) then you could probably do better with the mechanical balancing of the butterflies.

Perhaps I'm stating the bloomin' obvious here, but the balancing procedure should be carried out with the ICV deactivated, and the engine speed controlled (for setup purposes) with the throttle stop screw. If you check the balance at two different rpms, the balance can only be the same at both speeds if the bypass screws and the butterflies are evenly matched. [This is a very tough test BTW....]

Also I wonder if there is a better fluid to use in the manometers; I'm not thinking about accuracy, I'm thinking about what happens if the fluid gets sucked into the engine accidentally....

-jut my two pence worth-

Overall I think it is a really good scheme (and is pretty much the same as what I have had in mind for my DIY flowbench too.... )

cheers

[Carlp336]

pretty cool

but these are cheap! ive used it and its great and super cheap.

http://www.amazon.com/43-5712-Universal ... nchrometer

good for carbs and alpha-type fuel injection I am sure, but is it just me or am I the only one who can't see how you would ever use that on an M-motor with an AFM? Somehow you have the engine running with that in a bellmouth, and the AFM is still able to measure the airflow and run the engine....???

FWIW I think the manometer scheme is a pretty good one. In terms of accuracy, the manometer is miles ahead of a bourdon tube gauge; it is about two feet of head per psi on the manometer, and on a bourdon tube gauge it might be, what.... about 1/4" tops?

In fact I'd suggest that you might be wasting your time tuning the bypass screws to get that last 1" or so on the manometer; the pressure difference is tiny.

Also note that if the screws end up being set more than a fraction of a turn different to one another, this is a clear indication that the butterflies are not set correctly - or at least they are not flowing the same amount of air, anyway..... Thus if you get the idle vacuums spot on, the engine may not be running optimally just off-idle.

I dunno exactly how it works on an M-motor, but on a lot of engines the base setting for the bypass screws is (say) 1.5 turns out, and if the ITBs are 'balanced' at idle with settings that are outside the range 1.3 turns to 1.7 turns (say) then you could probably do better with the mechanical balancing of the butterflies.

Perhaps I'm stating the bloomin' obvious here, but the balancing procedure should be carried out with the ICV deactivated, and the engine speed controlled (for setup purposes) with the throttle stop screw. If you check the balance at two different rpms, the balance can only be the same at both speeds if the bypass screws and the butterflies are evenly matched. [This is a very tough test BTW....]

Also I wonder if there is a better fluid to use in the manometers; I'm not thinking about accuracy, I'm thinking about what happens if the fluid gets sucked into the engine accidentally....

-jut my two pence worth-

Overall I think it is a really good scheme (and is pretty much the same as what I have had in mind for my DIY flowbench too.... )

cheers

not sure i follow your use of "scheme"

it worked perfectly in my scenario with no AFM. this is a tried and true means to balance butterflies in many setups..

[TBM]

HI Guys...

Not to spoil the anything for anyone...

I own this : http://www.thedigisync.com/digi-sync-top-page.html
I bought it for my M635sci. It is VERY accurate and very easy to use.

I will gladly loan it out for a nominal fee if anyone is interested. The usual applies with regards to shipping and your handling of it.

PM me if you are interested. I am leaving town on business for a couple of weeks but will be checking my in box to communicate.

[GazM3]

That digisinc looks good.

Too bad I ordered 6 vaccum gauges and will build one. There are a few of us with the s38/m88 here in Melbourne so it will get used regularly hopefully. B

[Brucey]

not sure i follow your use of "scheme"

it worked perfectly in my scenario with no AFM. this is a tried and true means to balance butterflies in many setups..

sure. As I said before I agree it will work if you have (say) sidedraught carbs or an Alpha-N style EFI setup (which does not use an AFM).

But M6 and M635CSI have an AFM fitted and this won't be able to take a reading in a normal way (so that the engine will run...) once you have taken the airbox to bits to fit that airflow meter into each TB in turn.

If you have actually found an easy way of using that tool on a motronic EFI setup, e.g. by 'fooling' the AFM, do say how you did it. [Note also that what works on an M6 may not work on M635CSI, because the latter runs open loop...]

cheers

[Brucey]

....Too bad I ordered 6 vaccum gauges and will build one....

the issue there is one of accuracy; as I mentioned above even a really good matched set of bourdon tube gauges is nowhere near as accurate as a manometer; basically 1psi vacuum is about 24" on a manometer vs one increment on a dial (bourdon tube) type gauge. Normally this means that a typical bourdon tube gauge is about x100 less accurate/sensitve than the manometer.

I have no idea how accurate a digital vacuum gauge set is going to be, but if it is any more accurate than a manometer I shall be amazed; it is a tough thing to have six gauges (mechanical or electronic) that agree to the required level of accuracy. The main benefit to a digital setup may well be ease of use.

cheers

[TBM]

http://www.thedigisync.com/why-the-digi ... etter.html

[Brucey]

well, playing devil's advocate... "they would say that, wouldn't they?"

Their assertion that it is only the vacuum drawn on the intake stroke that is relevant is not necessarily the case; during the other ~3/4 of the time there is air going past the throttle butterflies in a way that is related to their opening too, and that air also goes into the engine, nowhere else!

Remember that the whole idea of using vacuum is as a proxy for airflow into each intake. This is determined by the average vacuum, not just the vacuum peak seen on valve opening, which can vary for all kinds of other reasons. Note also that airflow is in turn is only meaningful (in terms of engine running) if the fuelling in each cylinder is perfectly balanced too.

Note that engines running a lot of valve overlap see pressure pulses in the inlet that come from the exhaust, so in this case the fuelling can affect the vacuum reading (during valve opening) directly too. [Try unplugging one injector and see what happens].

[In some engines -M88 being one? - the inlet ports are effectively linked via the ICV air passages too; this means that you may well see pressure pulses from neighbouring cylinders even if the ICV is not showing any net flow. Because the timing/interval of these pressure pulses is not uniform between neighbouring cylinders, the effect of this may not be uniform. It may even 'confuse' a digital system, giving false rpm readings etc as it does with a siamesed intake.]

If the digisync people wanted to sell me a system they would have to produce some more evidence than that; for example showing how their system works on different engines ( with different ICV operation, smart fuelling on each cylinder, different valve timing etc) showing how it is more accurate than Bourdon tube gauges (not difficult) or how engines that were 'set up' using manometers were actually not set correctly. If it does all that, and works quickly and easily, I can see the value in it for someone that does this kind f thing on a regular basis.

As it is, whilst I can absolutely see the value in seeing the shape of the vacuum signal, their system appears not to offer that; it just generates a number that is based on that, using an opaque protocol that may be subject to errors under some circumstances. Also, maybe it is there somewhere but I didn't see an indication of the actual resolution of their system, or how it is calibrated, or when it needs to be recalibrated.

I'm sure that manometer systems have their shortcomings but they are extremely sensitive, simple in operation, and effectively immune from certain types of error. For an occasional use I think that these are considerable benefits that perhaps outweigh any improved convenience offered by other systems.

cheers

[wjtesquire]

I just calculated my fuel consumption over the last two tankfuls after using the manometer and averaged 16.6 miles per gallon. That is up from 14.3!