Alfa Pages

Admin · Posted: Thu Mar 13, 2008 5:20 pm Post subject: Dyno graphs

Hi

Anyone got any charts from dyno runs for their cars. Power against rpm? And what wheels / tyres / gearbox they have?

If so any chance of scrounging a look?

All the best

Keith
_________________
I owe, I owe, its off to work we go.
Bimota Forum
Stafford Christmas Lights

Oggie · Posted: Thu Mar 13, 2008 9:28 pm Post subject:

I will ask Adie Hawkins if he can print out/email me the info reguarding me motor before it got sick, we still ain't found the problem with the mis fire and it looks like it might get expensive heads off and a good look around.
_________________
PHAT 33

Admin · Posted: Thu Mar 13, 2008 9:35 pm Post subject:

Hi

Cheers.

I have been playing around knocking up some php to take power or torque against rpm, and save it. Then give a graph of power against torque, and with the gear ratio the thrust in each gear against speed.

Mainly done for bikes but no reason cars cannot go in there.

An example for a 1200 Bandit:-

http://www.alfa-pages.co.uk/phpBB3/TorqueThrustGraph.php?Id=8&x_max=700&y_max=500

Next stage is to allow different vehicles to be overlaid on the same graph.

All the best

Keith
_________________
I owe, I owe, its off to work we go.
Bimota Forum
Stafford Christmas Lights

Oggie · Posted: Thu Mar 13, 2008 9:41 pm Post subject:

Are you trying to compare newer cars against the older car ratio's?.
_________________
PHAT 33

Admin · Posted: Thu Mar 13, 2008 9:46 pm Post subject:

Hi

Just doing it for fun. Once sorted I might set up another site so people can enter their own details (entering is already sorted out, just not very user friendly).

Actual idea was to end a few arguments on bike forums about V twins vs inline 4s. And gearing is pretty important when you are dealing with engines with dramatically different strokes so different rev limits (so the 4s can run lower gearing).

Only real difference between cars and bike is that almost every car has a fixed 1:1 primary drive ratio, so no reason they cannot both go on the same system.

If I can (at a later date) add an overlay of drag then it will be interesting to see the changes in theoretical top speed depending on the gearing used.

All the best

Keith
_________________
I owe, I owe, its off to work we go.
Bimota Forum
Stafford Christmas Lights

Ben_nz · Posted: Fri Mar 14, 2008 11:54 am Post subject:

Here's a dyno graph of my s2 1.7QV.
http://www.axys.co.nz/ben/alfa33/DYNO1BIG.JPG
It has the standard wheels and gearbox, and the minor modifications (K&N filter and rear muffler at that stage) probably don't compensate for 20 years of engine wear.
_________________
"Now, all that is left to do ... is wait that something else brokens, to fix up again!"

Admin · Posted: Fri Mar 14, 2008 12:28 pm Post subject:

Hi

What gear was that in? 4th I presume but not certain.

I haven't yet written the input script to take power at road speeds and convert it to rpm (on the list of things to do) so it may take me longer to play with that.

All the best

Keith
_________________
I owe, I owe, its off to work we go.
Bimota Forum
Stafford Christmas Lights

RBL · Posted: Fri Mar 14, 2008 12:42 pm Post subject:

Admin · Posted: Fri Mar 14, 2008 1:12 pm Post subject:

Hi

Claimed was (from a book of old road tests) 145lb/ft @3500rpm.

Looking at that graph something strange is going on. There is a direct relationship between power and torque with rpm. No rpm in that graph, but knowing power and torque you can work out rpm.

Power (Kw) = Torque (Nm) x 3.14 (pi) x RPM / 30000

Rearrange that and you get:-

RPM = (Power (Kw) x 30000) / (Torque (Nm) x 3.14 (pi)

From that looking at the graph at 110kmh you seem to have 47kW & 200nM. That gives you 2244rpm, which seems VERY high gearing. At 6000rpm (point of claimed peak power) that would give you a speed of 294kmh.

Although that should really be based on flywheel readings rather than rolling road readings.

All the best

Keith
_________________
I owe, I owe, its off to work we go.
Bimota Forum
Stafford Christmas Lights

RBL · Posted: Fri Mar 14, 2008 2:17 pm Post subject:

There's some helpful specs here - looks like torque is usually around 109ft/lbs according to this?

I'd love 145 ft/lbs!

http://www.carfolio.com/specifications/models/?man=257&f=4c
_________________
Porsche 550 spyder replica with Alfa Sprint 1.7 engine

Ben_nz · Posted: Sat Mar 15, 2008 1:34 pm Post subject:

I don't have a special sixth gear and magical super torque - ignore the torque curve on that graph. I said to the dyno operator the torque looked way too high and asked how to calculate actual engine torque from that, and he said he didn't know - nobody ever asked that question! Confused

I don't remember what gear the run was done in, but it finishes at 150kph which was 6000rpm. The first run was done up to 140kph / 5500rpm but it looked like there might be more power (and the first torque curve came out even weirder) so we tried pushing our luck a bit more.
_________________
"Now, all that is left to do ... is wait that something else brokens, to fix up again!"

Admin · Posted: Sat Mar 15, 2008 4:02 pm Post subject:

Hi

Had a play:-

http://www.alfa-pages.co.uk/phpBB3/TorqueGraph.php?Id=12&x_max=800&y_max=600

Red line is torque, black line is power (on a graph with lbft and hp they should cross at 5252rpm.

I think you were in 4th gear. 3rd would put you at 6800rpm at 150kmh, while 4th puts you at about 5300rpm (although still debugging so may have made an error - entry in kmh certainly doesn't work yet!).

Thrust through the gears is here:-

http://www.alfa-pages.co.uk/phpBB3/TorqueThrustGraph.php?Id=12&x_max=800&y_max=600

All the best

Keith
_________________
I owe, I owe, its off to work we go.
Bimota Forum
Stafford Christmas Lights

Ben_nz · Posted: Sun Mar 16, 2008 11:51 am Post subject:

Eenteresting.
The dyno guy would have been going from my car's analogue rev counter which overestimates a bit.
Why do you think there's high initial torque, then a dip, then it wakes up again?
It's not as weird as an Alfa V6 dyno plot though, if you've seen one of those:

Lookit that jump around 120kph!
_________________
"Now, all that is left to do ... is wait that something else brokens, to fix up again!"

Admin · Posted: Fri Mar 28, 2008 9:35 pm Post subject:

Hi

I have now done most of what is needed for this. Mainly aimed at bikes but no reason cars cannot be used on it (just with a car you cannot change the final drive ration easily, and the primary drive ratio is almost always 1).

http://www.bikegraph.co.uk/

You can enter your own details and display them. And release them for anyone to see or just keep them to yourself.

All the best

Keith
_________________
I owe, I owe, its off to work we go.
Bimota Forum
Stafford Christmas Lights