ALFAGTV6.COM

[Zamani]

JimK,

I was implying that if we took 7% as the accepted loss, then basically you're saying, for example, the Civic SI (rated at 160 bhp) and only getting 135 wbhp is actually a 148 bhp car. Of course I am quoting a sample size of... 1 . Anyway for the sake of this discussion, it implies that Alfas are not the only manufacturers inflating their figures.

IMHO, the best way to determine transmission loss, besides just taking the word of tuners or dyno operator is to go to a dyno shop, ask for hard data of previous baseline runs of various cars. Get as much as you can. See how the measured power relates to the manufacturer's claim.

The more data you have, the better as you can roughly determine an empirical loss factor and estimate what your car should put out.

Anyway this touches the issue of sampling size for a given car model, weather condition, tires etc. Can of worms.

Now back to the regular programming....

[Barry]

Jim,In my experience hare in S.A.(no bloody quips,ok.....)I tend to go with Zman`s 17% figure..We have 4 major dyno manufacturers hare who export thiere dynos worldwide...The Dastek dyno(From Unichip fame )is probably the best darn dyno you can get...Peter de Weerdt actually has schooling sessions for international clients who buy his product.What Im getting to here is that I and most I talk to get the 17 to 20% figure...Some front drives are better while some Falcon v8`s(hint hint Zamani....)Are just down right terrible...like 25 tp 30% losses...We have a chap here revered greatly by the Porche factory for his dedication and knowledge on Porches..Brian White is internationally known for his Porche prowes and has managed the factory works team entered in the Le Mans 24 h.on many occasions...The one thing he said to me is datalog temperature in the gearbox as you drive round the track..Come back and analyze the temp data and work out the losses.Im not sure how to do this but apparently on a G50 box it amounts to much more than 7 %.And as we know there are many more contributing factors...
I actually trust the driven /coasting method of measuring losses(for the average joe)I think it is a good indication as long as your comparing apples with apples..
I suppose the final test would be on an engine dyno,straight into the car and then on to a chassis dyno........her we go again,2 different dynos.......You know what??LOTS of losses make me happy-means I have a MUTHA engine under my butt!!!!!Who cares that the Fiesta td nailed you,I have more power........

[Jim K]

In that case we all get an ego boost, adding 17% to our wheel power! Still, one of the most respected names in the dyno industry, Rototest of Sweden, talk about 7-10%. Read this: http://www.rototest.com/index.php?DN=16
and also, to add more confusion:
http://www.ultimategarage.com/dynapack.html
I'm still confused, I understand your people claiming 15+% losses, but there seems to be great disagreement among experts in the field. Bottom line is, when I got 186 wheel, it means I have anywhere between 199 and 217 engine, using 7 and 17% losses.
I know the only way is to pop the motor out, test it and throw it back in, well, it just ain't that simple, I wish it were!
Nice no-end subject we got here, one of the few that can't be resolved! I'm inclined to hit 3-4 local dynos in the same day, but unfortunately, they're not free (70-80Euros per shot).
JimK.

[Zamani]

Actually one thing that has surprised me is that, from lots of discussion I've read in magazines, no one has ever substantiated a given drive train loss figure using a proper statistical approach.

Determine an acceptable level of confidence, an appropriate sample size and off you go! Easier said then done I guess.

[Jim K]

Z, even if they did, it still wouldn't give an indication of real engine power, just a uniformity of dyno calibration. Then again, is there any agreement in the first place on indicated wheel power between dynos?? The whole subject is floating on both ends, if you ask me!
Jim K.

[Zamani]

You are right Jim. Any trials for a given dyno is only good for that dyno and that dyno alone.

[Mats]

Try different tires, they make a huge difference.

[Micke]

As I said, the rolling resistance of the rear tires is included in the drivetrain losses. As the car is usually (even alfas) strapped to the ground with much higher pressure than normal the impact of this must be significant.

[SamW]

We did three GTV6's on a Dyno the same night last year, I too heard the 17% loss, which makes sence if you look at our results, two cars were mostly stock (no cats), one running stock tires, the other two running one size over (205/55/15). They made 135,133,132 hp, the highest on the stock tires on the most miles on the engine. This gives (w/17% loss) 159hp - 162 hp, which seems about right. I know this is not very scientific, but seems pretty reasonable. I would hate to think all three are down 10% on power.

[Luis]

Here is a dyno run from a Spanish magazine, euro specs gtv6 (no cat), so here the cars can have 5 hp more than cat versions.

The text says that the Ford Sierra (2.8 v6) have high mileage, and maybe doesn´t give the factory hp for this reason.

The Gtv6 maybe need a check (ignition advance) because other ones gives near 160 about 6000 rpm.

The 3.0 engines are around 185 hp, and the QV version (whit cat) 180 !! (factory claims 192...), alfa 164 are up to 184 hp (almost the same engine as 75 QV).

[Jim K]

Ok guys, this hp loss business is a whole container of worms, way past the can stage! I found some more interesting reading here:
http://www.eng-tips.com/viewthread.cfm? ... 240&page=2
Personally I'm at a loss and it looks like the best thing to do, is to take dyno figures on a comparison basis for mods and cars measured on the same rig! You wanna compare your tool with someone else's? Use the same dyno, if possible on the same day!
Jim K.

[Mats]

engine dyno and normalized numbers and test procedure is the only way, everything else is just not giving any comparable numbers.

Try asking someone if it was tested static or sweep...

[Zamani]

Mat's,

I have asked Beninca about this. He has both type dynos and tons of data from both the engine and chassis dyno.

Aren't most dyno runs a sweep from 2000 - redline?

[Barry]

Aaah,got it-load or inertia....

[Jim K]

Load or inertia what, Barry?
Jim K.