ALFAGTV6.COM

[Jim K]

Hi guys,
A few months ago I approached the only local ITB makers and asked about the possibility of making a 24v kit. Well today, they came by with the working prototype which to my eyes, looks good. Throttle plates are 47mm and as seen in the pics (without my fuel rails) it costs 1000€. Two years ago I'd buy the thing but -as you may know- financial conditions here are not in agreement with such hobbies!
Jim K.

[75evo]

Ok so is it made out of oak, redwood or teak?

Seriously, Euro1K is not expensive. AHM wants waaaaaaay more. I wonder if i can get this and have a plate which can swap between a 12v and 24v.

[Jim K]

I would think all you'd have to do is make a short adaptor stub for the 12v.
Jim K.

[Mats]

So I think the question on everybodys mind is: How straight is your wood, Jim?
Has the parts been test fitted to an actual engine?

[Jim K]

Good point! I asked the guys to let me borrow the set for just a couple of days, so that I can play with it and check form/fit/function on the spare 24v I have at home but they were very reluctant... So, I guess nobody knows until I buy a set, right???
As for the wooden jig, I'm pretty sure its good as I put a lot of measurement into it.The 'bolt holes 'match those on the heads. You can't see in the pics but the surfaces are held in place by guide wires; its really quite sturdy.
Originally, I asked them to make ITB's which would bolt on to the short stubby manifold/plates of the 24v, as I had those properly fixed on the jig. Instead, they eliminated the stubs and made something that bolts directly on the heads, eliminating the stubs. In other words, they did more work -unnecessarily, I think. They copied the lower surface of the stubs and worked from there.
Jim K.

[Duk]

47mm is pretty flippin big!
Why are they so large?
These engines aren't exactly known for their low RPM torque and you can make 100hp/litre with 39/40mm runners.
Unless you can use really long trumpets on them (and even then ), in my opinion, 47mm is just way too big for anything other than some demented 10,000RPM monster.

[Mats]

Damn!

Didn't even see that part and I agree, too large for anything really. Throttle control will suffer...

[Jim K]

Its a gradual taper from the mouth of the trumpet all the way to the manifold mounting surface which is std size. The throttle shaft is ~8mm or so, so 47 is not really huge. I may have another look at these things this afternoon and I'll try bolting them on the spare 24v. Throttle control can be 'adjusted' to a good extent by the shape of the crank actuator (the part where the throttle cable fits into). Notice the shape of various Alfa cranks...In some cases, there is significant 'foot travel' required for a small throttle angle change. Will something like this ease your objection? This prototype set has no such provisions -and I can't see who would be willing to make any changes unless they bought the thing.
Jim K.

[75evo]

This could be an alternative

http://www.triumph675.net/forum/showpos ... stcount=14

No no, not the porsche engine.....but the Triumph ITBs. 44mm at the top and taper it down to about 40mm at the port. Suitbale for a very modified 12V.

I'm not 100% sold on the ITBs, especially on a car with a modern EFI and idle quality not being a source of concern at all. But it would be interesting to see the result.

I guess ITBs, in this day and age of modern EFI has the following + points
1) wow factor
2) minor improvement in idle quality for cams with big overlap
3) throttle response
4) BIG SOUND http://www.youtube.com/watch?v=TxYy5iLO ... el&list=UL

Hey JK,

isn't this your car?

http://www.youtube.com/watch?v=JoWQz4l2Cpo

What is that sound after you shift??


And a gratuitous video of me chasing and exige S
http://www.youtube.com/watch?v=c2UVpaU4084

[Jim K]

Well, I agreed to buy the ITB's and do whatever tests and measurements need to be done. However, these things will take time as ITB installation is not a priority -far from it. If I ever use them, it'll be in the future 3.2 which is still missing a crank...
Hah, I hadn't seen the video! Its from our 3-day track weekend in April and a friend is driving the 24v. I don't know what that post-shift sound is, could be the 'boom' and flame due to lack of fuel cutoff (as I've written elsewhere). I got pissed at the driver, as I had asked him not to exceed 7200-7400rpm max. You can see the shift light come on several times -it was set at 7300!! The idiot didn't know about the Stack recall button... and it read 7800!! Remember, this motor has stock pistons and rods!!

Jim K.

[75evo]

Are you expecting any increase in power from the ITB? I would say if any, probably a wee bit on the top end, maybe?

BTW I noticed the injector ports don't fire into the throttle body. So you need to modify the 24V injector plate to accommodate it?

Well I may go with the triumph ITB grafter on the 164 12V injector plates. Then change out my 11.x mm cam. My last cam change for the 12V (funny I thought I said the same thing when I had the C&B cam )

[Jim K]

I am under the impression the gain is ~15-20hp max at the top. If you have hairy cams, you do get better idle and drivability.
If you look closer, you'll see the injectors fit as in the std engine -which is what we really want.
When you think of it, ITB's should only be considered for very high horses as in racing... My 24v has 90hp/liter with the std throttle and 100% catalyst street cams -albeit from another roadcar. With the 3.2liter and fast road M3 profiles, I believe close to 100hp/liter is reasonable, translated to ~320hp. Why then go to ITB's? Ok, I may give it a try since I also have the Emerald K6; but like I said, all this is a long way off. Another difficulty with ITB's is coming up with a suitable air filtering arrangement.
Oh well, at least we'll see how they fit and look on the engine in a few days.
Jim K.

[MD]

75 Evo,

I think we have overlooked the key criteria for ITB's which is the ability of tuning each cylinder according to its specific combustion requirements to extract the best performance that an engine can produce overall.

Nothing else will do this.

The best example of this is when an engine is on an engine dynomometer and you can visually see the individual glow differences in each exhaust manifold which is a result of a lack of combustion uniformity that can then be individually corrected.

Other problems associated with their use is a matter for more problem solving but I never lose sight of the main objective. Best things since sliced bread.

[Duk]

I think we have overlooked the key criteria for ITB's which is the ability of tuning each cylinder according to its specific combustion requirements to extract the best performance that an engine can produce overall.

Nothing else will do this.

The best example of this is when an engine is on an engine dynomometer and you can visually see the individual glow differences in each exhaust manifold which is a result of a lack of combustion uniformity that can then be individually corrected.

Other problems associated with their use is a matter for more problem solving but I never lose sight of the main objective. Best things since sliced bread.

Ah, but some computers, ones with ample spare processing power and the firmware that has been created to use it, can do individual cylinder mixture and ignition correction.

[Mats]

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?