ALFAGTV6.COM

Duk /Mats

My take on it this. Air is metered indiviually by each TB and each induction path has is own minor differences depending on the path it takes and minor quirks in profile and total lengths, air turbulences under the bonnet etc. Just enough differences so that one could not say (as a rule) that each and every induction segment of the engine is ABSOLUTLEY identical.

Because there is no common air feed like a manifold (that creates its own air tubulances internally and is another topic of its own) individual air and fuel mixtures are more readily tailored for each cyclinder. This is assuming that the FUEL is going to be adjusted for each cylinder while the air remains a constant ratio.

A gas analyser on each exhaust port soon tells the story of what is required.

So no, I don't mean indiviual air adjustments on the TBs at all *. (only to calibrate the butterflies so they all open in synch with each other and the same rate which is really only most critical for idle balance)

*Well perhaps to this degree. Given that air movement under the bonnet is not a uniform thing, individual induction for each cylinder could be modified in terms of length, id , intake direction and the like that may influence the air relationship across all the TB's thereby indirectly "tuning" each air intake to overcome under bonnet turbulences and resonances.

Come on guys! Next thing we'll build an improved Space Shuttle! I forget how high we rank in gazillion-buck pro motorsport so that we can deal with individual cylinder tailoring!! Life is much simpler... leave it be! If the thing can make 300hp with a 'normal' aftermarket ecu and ~400€ mapping time, I wouldn't bother with a high end Motec ecu and 1000€ of mapping -and for how much gain? 5? 10hp? I just don't think its worth it. One very important related concern, is to make sure your injectors are identical and very few people can claim this. I ordered 'matched and balanced' injectors from UK and I measured them with my crude -but very accurate- setup and they differed by up to 4cc/minute: UNACCEPTABLE! I then looked around and eventually, made up a set with 1cc difference, but I had to clean and check ~15 injectors before I could get there. So, to my mind, injector balance is most crucial to avoid the need for cylinder tailoring.
Jim K.

Your Q4 ECU does individual cylinder compensation to a degree, as do many modern OEM ECUs.

Magic words: to a degree, but not to the extent Duk and MD mean it. I believe the Q4 ecu (and several others) have some latitude in retarding advance for each cylinder, by 'knowing' which one knocks but not for fuel correction, where its just a gross correction per bank of cylinders in this case -correct me if I'm wrong.
Btw, when the 3 good ecu's arrive next week, I'll send you the fourth one (0261203834) so that you can do your magic regarding fuel cutoff. This ecu is exactly the same as the ...301, but has the (now disabled) immobilizer. This is the alternate ecu for the Q4. The car runs fine with it, albeit with the std eprom.
Jim K.

MD: I think I understand what you mean, downstream of the TB it's more likely that the ITBs are more similar then when you have a plenum.

But then again you seem to run the air horns in free air under the bonnet? Are you mad?
Warm air and not to mention unfiltered air will seriously lower HP output A LOT more then cylinder imbalance. You still need an airbox around the runners, sure it can be HUMONGOUS to even out everything but you still need it.

Cold filtered air is a must. In the case of these ITB's, I think I can adapt and use the large air filter from the old Alfa 6 -the one with the 6 Dellortos. I found one such air cleaner here last week, but I was surprised at the weight of the thing! Damn, it must weigh ~7kg or more! Seems to have a sturdy (and thick) steel plate underneath. Maybe I can replicate it from lighter alloy. Man, I wish I was good with fiberglass! I've seen some very nice induction arrangements in various cars.
Jim K.

Mats wrote:Had a chat with a friend yesterday regarding ITB sizing and he said it didn't sound that bad, it's not a direct translation between single throttle vs ITB and it has probably something to with the fact that the airflow is much more uneven for a single cylinder application and the airspeed is a lot higher and might choke. Normally you have quite a big buffer behind a multi cylinder thottle that helps even out the flow.

MD, how do you tune the individual cylinder with ITB's? Are you assuming that you can adjust the throttle plates individually?

what about a map sensor each ITB to tune the plates.?

Hey Mats. You asked me if I was mad. Well if you had been tracking my posts a little closer you would have realised the answer by your own accord. Absolutely ! (and nuts as well for good measure) I have said it before, sanity is overrated.

However I am not stupid or ill informed.
Indeed I pay attention to cold air in the path of my intakes which are filtered by the way. The arrangement I am using is no accident. Nevertheless, I do not intend to go into a verbose explanation or justification for it here. Here's a short one..

Mats, just to recap as I don't think you realise what the Cab' job is at the moment. It's a trainer so the important stuff is handling and brakes which are doing a splendid job. It uses a street engine and the ultimate power is not important. It just needs to be reliable and simple to maintain. When it gets a proper racing engine, the story will be different.

I got the ITB set yesterday and bolted it right away on the spare 24v. All looks good, no mismatch steps inside the bores. You can see the horns are ~5mm apart: my original intention was to use phenolic spacers (same material as under the 12v runners) for some heat isolation. With those in place, the horns will be very close to each other. Still, their distance is influenced by head milling and the fact there are no head gaskets on this engine. Throttle shaft diameter is 8mm and distance from horn mouth to valve is 235mm, about 45-50mm shorter than the std chrome curvy pipes.
Price haggling is ...mandatory in some countries and I finally paid 900€ for this first set, since I helped with the jigs. They've already listed the set in some site for 1300€ (see http://mfsolution.car.gr/parts/?ca=112).
Jim K.

Mats, I have a clarification edit for you above regarding intakes. Cheers.

Right, but you already said you had a cold air filtered intake and that's all I needed to hear.

One thing I noticed is that all 3 seem to be on one single shaft.
I think they might bind under temp as the thing expand.
I would think it would need one or two of couplers that let the shafts expand a tad per bank.
unless there is something hidden I can't see.
I thought 2 close together like in a carb or a SPICA was the limit for a single shaft with out experiencing binding with thermal expansion

There's only one way to find that out and it it won't be anytime soon....
Jim K.

The South African guys have had tripple ITBs for a while iirc, maybe they can chime in?

I would love to have some of these for my 3.0 12V.