ALFAGTV6.COM

Jim K · Post by **Jim K** » Sun Dec 24, 2006 5:47 am

Here are the 12v 3liter measurements I did last week. As one might expect, they have a reasonable relationship with each other, when you read the inset legend (not very clear because of downsizing). The most interesting curve is yet to come; it will be the current 217hp engine with my fast road/trackday cams (when I finally get them!)
Oh, everything is engine power (lets not go back to that) and naturally all runs are in the same dyno, same conditions.
You can appreciate the std Jetronic cat. 3liter having 170.5hp as compared to the factory claimed 184.
The blue curve belongs to my previous engine (sold last month to a friend) where I had ported the heads but it had std runners! This is part of the reason of the decreased power below 3200rpm (velocity drop in the head tract). The other part is slightly retarded cam timing which gained a bit higher up in the rev range. The cams are on the factory marks for the other two curves.
Jim K.

Greg Gordon · Post by **Greg Gordon** » Sun Dec 24, 2006 7:20 am

That's a great graph. I assume that's flywheel horsepower. If so I wonder how you measured it.

It's interesting to note that up to 4000 rpm it's tough to beat the stock setup. After that the mods really start to help.

fedezyl · Post by **fedezyl** » Sun Dec 24, 2006 7:58 am

Very intesting!! what piston brand are you using Jim? can't wait until your book comes out, by the way, your mods in a 1.6 I have, excellent results so far with 45 webers!

Jim K · Post by **Jim K** » Sun Dec 24, 2006 8:29 am

This is the coastdown type of measurement. From all such dynos we have here in Athens, this is the most conservative one used by a major carmag for all kinds of tests (new cars, shoot-outs etc). For most new cars presented and tested, they meet the advertised power specs, at least where serious manufacturers are concerned. In some instances they even measure more than the claimed power (not the case with AR's though!) Conversely, when they measure less than what the mfg. claims, they never get any complaints from them...All in all, its probably the most respected and consistent dyno around. I talked to them about my thoughts of plotting wheel power, but they said its not a good idea and it could be misleading to many, for several valid reasons that will be explained in a special section about power measurement in the book.
The guy doing the mapping is also very knowledgeable and I'm really happy with his work with the wide band sensor. I did over 80 laps in the local track, really beating the daylights out of the car without so much as a single misfire, pinging or whatever, spending most of the time between 5-7000rpm for 2 hours at a time! This should be enough to prove reliability of a newly built engine. They will actually market this chip after the book is out for anyone wishing to build a similar engine. This is the dyno I will use for all measurements in the book. There's one 12v run still to make and a few 24v ones, with and without mapping.
Fed, the pistons are JE bought from Paul Spruell.
I am really looking forward to testing with the 'good' cams next month! As for laptimes, the new engine drpped them by 1", a good result in our track and an even better one for the 1400kg pig!
Merry Christmas everyone!
Jim K.

ar4me · Post by **ar4me** » Sun Dec 24, 2006 9:21 am

That's a good-sized increase in power.

Any chance you can post the corrected (SAE or DIN) rear-wheel HP charts? Am I reading it correctly, that 20-25% increase in power (about 40 HP) dropped lap times by 1 sec? The double-quote unit can't mean 1 inch, nor 1 min, can it?

Jes

junglejustice · Post by **junglejustice** » Sun Dec 24, 2006 9:51 am

Really brings Alfa Romeo's claim/ratings for the SZ in to serious question...

kevin · Post by **kevin** » Sun Dec 24, 2006 11:05 am

Really impressive results. Are you saving the fourth graph for Christmass day.

Jim K · Post by **Jim K** » Sun Dec 24, 2006 11:05 am

Yes, the time is better by 1sec. This though is not an important or very scientific fact, as track times are very volatile and depend on a multitude of variables: if you visit a clean track to play right after the end of a race, you will most definitely log great times with all the sticky rubber on the pavement! If you return the next day when its nice and windy blowing dust and/or sand....your times are useless, a fact we have all seen time and time again I'm sure! Main thing is the way the car feels all around (seat of the pants!)
Don't forget now, we are talking about a 1400kg pig with 6.83kg/hp previously and now 6.45kg/hp, not a very significant change at all. Previous laptimes were logged with the 'blue' line engine and now with the 'red' one, a difference of only 12hp. I never had the std (green) engine to measure. I'm sure it would be several seconds slower though.
On the dyno, when the car is coasting down, the loss curve is being slowly drawn on-screen, and when it about zeroes, it disappears and the power curve appears. That's the way their software works. Numbers shown are supposedly to DIN std, automatically corrected for temp/press. I inflate tires to 34psi for all tests (its what I use on the street too).
Unfortunately there are no SZ's in this country, I'd really like to get one on this dyno. Its supposedly rated as 207hp. I'll give you something to think about though: My previous engine was the 75 Potenziato engine (AR061503) officially rated as 192hp/6000rpm with cat! I increased CR to 11:1, ported the heads about 50% of best possible, ordered valves with 8mm stems, balanced everything, added CSC headers and a 63mm exhaust (no cat) and measured 197hp. Then I remapped and measured 205. Does this make sense considering that the CSC alone is good for 8-10hp and the absense of the cat is worth another 3-4? We are now talking about engines in great mech. condition, no oil guzzlers and 215psi cranking press on all cyls.
The SZ has exactly a Potenziato engine + headers, thats all, same electronics too (ECU+AFM). Maybe the rest of the exhaust system is better, I'm not sure, I'll have to check the microfiche for P/N's and look.
The fact remains that we cannot correlate results from different dynos nor can we bank on 'correct' readings. We can only test for gain/loss using the same dyno. I cannot claim to have 'true' readings any more than anyone else can and we cannot compare engines this way unfortunately. The before and after is what counts and no other claims can be made (case in point, the 205hp mapped engine above, measured out at 235hp on another rig, the kind they take the drive wheels off and bolt the hubs to the dyno).
Kevin, I wish I had the cams now; I'm off work for a couple of weeks and nothing to do...
Jim K.

Jim K · Post by **Jim K** » Mon Dec 25, 2006 12:57 am

Oh, I found a nice article with some power values here:
http://www.europeancarweb.com/features/ ... lfa_romeo/

Although in the article they measured wheel power,the numbers relationship with my engine power measurements is very interesting, both the std and modified ones.
As far as torque curves go, I'll post the plot again when (if) I figure out how to print a scale on the right border through Excel (not through Paint!) The damn Wizard isn't too much help on this!
Jim K.

jol · Post by **jol** » Mon Dec 25, 2006 6:39 am

JimGreek wrote:Oh, I found a nice article with some power values here:
http://www.europeancarweb.com/features/ ... lfa_romeo/

Although in the article they measured wheel power,the numbers relationship with my engine power measurements is very interesting, both the std and modified ones.
As far as torque curves go, I'll post the plot again when (if) I figure out how to print a scale on the right border through Excel (not through Paint!) The damn Wizard isn't too much help on this!
Jim K.

I use office excel 2003

Jim K · Post by **Jim K** » Mon Dec 25, 2006 8:51 am

Thanks Jol, will have to work at it!
Spent all afternoon trying to shoehorn the torque curves in the graph and I think it looks half-decent.
Jim K.

Post by **Zamani** » Mon Dec 25, 2006 10:53 am

Jim,

I would suggest wheel power, let the readers decide what to use as loss factor.

Jim K · Post by **Jim K** » Mon Dec 25, 2006 11:45 am

Like I said, that was my original intention but the dyno guys said its the wrong thing to do for a number of reasons which will be explained in time (if you recall, Mats and Micke have also disagreed with the wheelpower idea on technical grounds when the subject came up a while ago) So, I'm stickng to this method. If anyone has different data from their own dyno runs, relationships between our numbers should be fairly constant between two particular machines. I bet there are both lower and higher numbers than what I've printed but such is the nature of the beast. I have a vague idea that my loss is around 8 or 9% but as has been pointed out this varies with speed and other parameters (oil type, temps, tire pressures and even roller size and number etc).
For our purposes, going to the same consistent machine will give us valid power differences to evaluate and that's the bottom line. The actual power number may never be known! Personally, I prefer to see conservative figures as they somehow convey more credibility...
Jim K.

MD · Post by MD » Mon Dec 25, 2006 1:17 pm

Gotta say I agree with you 100% JK (Don't sweat it, it's Christmas. I have to give it break some time).
All your efforts are about the engine and providing engine performance without all the other variables is the way to go.

...mind you my BMW powered lawnmover makes more grunt and chaff, haha

Jim K · Post by **Jim K** » Tue Dec 26, 2006 12:32 am

True, emphasis is on the engine now as this is where a lot of work is spent when building/improving a car. I feel that other crucial areas like suspension and brakes have some obvious ready-made solutions like RSRacing, roll cage and umpteen big-brake proposals presented here.
Jim K.

12v 3liter dyno runs.