ALFAGTV6.COM

[Duk]

Last night I got a call from a friend saying someone had cancelled their dyno appointment and asked if I wanted to fill the spot... So, today was dyno day! The first runs checked everything out and then it showed I drove in with 208 wheel hp. Couple of hours later and after severe engine-bashing, we saw 237 wheel hp, which is damn near a 14% increase from a good tune!
Jim K.

Fixed it for yah!

Nice Jim!

Looks like there is work to do if you want to break the magic 100Nm/liter though...

Can you consider the torque numbers accurate enough to make that claim? Torque increases by being under driven by the transmission. Even if it was in 4th gear, there is still the 3.9:1 diff ratio jacking up the torque. Not to mention parasitic losses. As Jim mentioned, the conversation about transmission loss is endless.

Surely an engine dyno would be needed to get entirely accurate numbers of what the engine is really doing.
Me thinks that the inlet ports are too big to get near the 100Nm/Litre with the Alfa donk.

[Jim K]

This is mostly a street engine, using the Renault Williams catalyst production cams. with 11.3:1 and just minor port cleanup and full rotating parts balancing. There's ample room for serious upgrades. Consider it a blueprinted street engine. Cam positions can be fiddled with but not now, like I said. Torque would improve quite a bit I think, if there were headers available with long primaries like the CSC's for the 12v. There's a thought to use the CSC system with new top sections made to measure for the 24v, but all expensive projects are put on hold indefinitely, due to our well-known financial conditions.
As I had zeroed the odometer before the session, I saw 95km on the clock! After my car, my 12v 3liter was checked out and investigated to see if more power was hidden and again gave 205 wheel hp (~236 engine). The operator said we could see maybe another 10hp if we go to ~7500 but we left this for another session.
What I was really amazed at, was the relative bucking and squirming of the two engines. The 24v was moving about a lot, while the 12v very little. Since all mounts are new or close to it, I can only assume its because of the light 12v flywheel (more than 3kg lighter) as opposed to the std 24v one (which is the std Milano one). Can anyone comment on this? I mean it looked as the 24v would jump out of the car!! And, the same operator beat the crap out of both cars. Of course, the violent bucking was when suddenly opening or closing the throttle.
Jim K.

[Maurizio]

What I was really amazed at, was the relative bucking and squirming of the two engines. The 24v was moving about a lot, while the 12v very little. Since all mounts are new or close to it, I can only assume its because of the light 12v flywheel (more than 3kg lighter) as opposed to the std 24v one (which is the std Milano one).

Yes, I think it is due the energy stored into the flywheels / rotating masses (needless comment: flywheel mass is not the right thing to compare, you have to look at moments of inertia).
Then there is probably a difference in rpm's (12v compared to the 24v). As in rotational energy the rpm's play a ^2 role....

But also a difference in CR will decelerate more when going off throttle = move the engine more.

[Greg Gordon]

Surely an engine dyno would be needed to get entirely accurate numbers of what the engine is really doing.
Me thinks that the inlet ports are too big to get near the 100Nm/Litre with the Alfa donk.

I don't know, engine dynos seem to vary at least as much as chassis dynos. This is especially compounded by the fact that when tested on an engine dyno the engines usually don't have their actual exhaust, air intake, electrical loads, and sometimes not even a water pump! Don' t underestimate the combined effects of these variables. When the US switched from SAE gross to SAE net around 1972 rated horsepower dropped about 20%-30%. Under the old gross system they measured power without everything connected. When they switched to net, all that stuff was required.

Greg,
www.hiperformancestore.com
www.okinjectors.com

[Jim K]

Ok, here's the dyno run. Can't see much but it sure was hair-raising at 7800rpm!
http://www.youtube.com/watch?v=pe5h682GW4s
There's also a run of my 12v 3liter, right after we finished the 24v:
http://www.youtube.com/watch?v=Bxs1LrxZ ... ure=relmfu

Jim K.

[Greg Gordon]

They sound great. Both must be fun! Normally I like the sounds of the 12 valver better, but your 24 valver sounds awesome.

Greg

[Jim K]

Ok, now that the dynomap (new word?) is out of the way, I have a short comment to make which seem to agree with those of the garage nuts who drove the 24v car: IT SHOULD BE BETTER AT LOW RPM. I searched the web high and low for any 24v dyno plots and they all look the same! What I would like to see, is the usual 'lump' in the middle of the curve, common to well-prepared 2liter 4-bangers. Indeed, that would impress anyone driving the car. But, a linear ramp that seems to go on forever is not pleasant, unless you have forged internals, you rev the pi$$ out of the thing and you have a short rear end. Playing with the simulator, I barely managed to gain some lower end torque by going to 750mm exhaust header primaries and 106/106 lobe centers. Not much else one can do to this engine! It can apparently make lots of power high up because of the 72.6mm stroke but it will always lack a decent lower end. Hmmm, going than to 3.2liters makes sense, as the 78mm stroke is a serious game changer. The basic shape is still an almost straight line, parallel to the 3liter, but I suspect it would make for a totally different driving experience. Alas, it'll be a long time until I can find this out for myself!
Well, I'll sum it up briefly again: all in all, what this engine needs is a SC kit and I'm sure there will be no complaints regarding the relative lack of low end performance! ...And NO, Greg Gordon did not pay me to say this!
Jim K.

[75evo]

This engine needs VVT.

Or why don't you try the 164 style runners with a custom plenum?

Having no VVT, short stroke, very short runners, sounds like a recipe for no torque.

BTW, 106/106, will the idle be ok??

[Greg Gordon]

Forced induction is the answer. Compared to VVT it's less complex and provides far more power, especially within the rpm limitations of most production engines.

That said, I certainly have no plans to supercharger/turbocharge a 24 valve Alfa V6. It's a very rare engine in the U.S. and I don't even know anyone who owns one. I just don't see a market for it.

All my current forced induction work is focused on the NORD. I don't want to hijack here, so I will put up a picture in another thread.

Greg,
www.hiperformancestore.com
www.okinjectors.com

[Jim K]

Closer lobe centers (increased overlap) does destroy idle quality. Even with the mild cams I have, idle had to be set to 1000rpm to be acceptable. The stock 164Q4 idles at 750rpm...but std cams are lower performance than mine.
I'm not about to change runners to fwd, length is only longer by a very few mm -I don't recall the actual difference. Anyway, the hell with it; I'll just have to ride it out until the 3.2 is born.
Jim K.

[kevin]

Jim , those torque figures are only an issue if you have a tall box the car . Even with the 10/41 that torque curve on the track with those cam profile ( I believe mine are the same) still makes your eyes water after a couple of laps . With the 10/43 it's perfect .
Have you tried going into a 50 mm secondary after headers not a 57mm . I'm sure I felt there was more torque in the 50 mm . I did not take any readings unfortunately for proof when I swapped engines over .
Car sounds awesome .

[Jim K]

The secondaries are 55mm OD, ~52mm ID.
I use the 1.8T box, 3.91:1 (43:11), much longer than the ones you brought up.
Just got back from a track weekend, where I had my first chance to explore the 24v and compare it to my 12v car. Fair comparison, as both cars have 205/50-15's and 1.8T boxes.
I must say I was somewhat disappointed with the 24v. While the sound was excellent (irrelevant to our topic) performance was lacking from 3500 to ~5000. Then it was great up to ~7200 where I shifted as max, because of the stock internals. Since I intend to drive this car frequently on the road, I think a short box like you mention is a detriment ...mostly to fuel economy! You may say 'who cares' and 2-3 years ago I would agree, but things are very different now....
My final idea is to wait until I can build a bulletproof 3.2liter (most likely with ITB's) long headers and a bit more cam than I have now. I would expect something around 95-100hp/liter, but I still think it will be lacking in midrange -although the higher capacity would go a fair way to patch up the 'hole'..
Reliability proved excellent after ~320track kms (100 laps) and the only faster Alfa was a very light 1.8T with 295hp (at the wheels). I was also glad to find there was zero oil consumption! Maybe this VR1 10w-60 is what this motor likes to run on!
Jim K.

[kevin]

Jim this actually is great news because I am currently building a 12v 3.0 to your specs and was really worried tnat my bad driving is gonna be exposed . When I compare my laps times to the3.0 24v . This particular track needs really good torque motors with the hairpins .my only issue it's 3.0 injected motor from gtv 3.0 which does not have the same pistons and heads as the 3.0 12v of the 75 .
However my dyno figures in kw for my 3.0 24v is still crazy high compared to both my gta's
156kw wheels vs 138kw.

[la_strega_nera]

So, I guess this raises the question, is a set of 2.5 24v heads going to be a better starting point for a hot 3l? Much like the 308 Ferrari guys chasing 208 heads as a starting point... obviously the 3l ports are too big unless you're turning 8500rpm+

[Duk]

So, I guess this raises the question, is a set of 2.5 24v heads going to be a better starting point for a hot 3l? Much like the 308 Ferrari guys chasing 208 heads as a starting point... obviously the 3l ports are too big unless you're turning 8500rpm+

Other options are to either shrink the ports or apply something like David Vizard's 'Polyquad' http://www.motortecmagazine.net/article.asp?AID=1&AP=1 approach to valve sizes and porting.
Or both.

I was always amused by how big the ports are in the 24 valve heads.