KV6 2.5: power & torque loss?

[Dorchester2]

Just to end with my dyno, here are the charts.
Rather mean profit as expected.
Nonetheless 5 bhp more in power (every little helps!) and a smoother & better curve mainly in the 2k revs that flattens and help not to notice a bit less the gap before & after the setting off of the VIS motors.
And icing on the cake the professionals validated my ethanol mod and found it efficient.
Hence I'm not that disappointed because I've got a good optimistic nature!
Thanks to all who helped me to understand the difference between figures from the flywheel and those from dyno and gave me skillful and comprehensive explanations on that matter.
EDIT: the slightly depressed areas of the curves are due - as you may guess - to the auto box changing gear.

[SD1too]

Originally Posted by Dorchester2

Just to end with my dyno, here are the charts.

Those are very good results Arnaud. Looking at the torque graph, the designers of the VIS system would be very pleased indeed.

Originally Posted by bl52krz

As Simon said, dynos always bring dissatisfaction ... if it ain’t broke, don’t try to mend it.
... increasing power by a mere 10/20 Bhp is a waste of time ... More torque in gear can be better than outright Bhp.

That's a brilliant summary Dave. As you say, what's the point of an extra 10 or 20 bhp at the top end? Who drives with the engine screaming at 6,000 rpm? Torque is indeed the answer and that was the idea behind the VIS system.

Simon

[Dorchester2]

Thank you Simon.
Nevertheless thanks to the (modest) remap the power increase beginning around 4.4k revs it may be very helpful while overtaking. Going at my younger son's and back, along 1100 km (700 mls) 13 times I went over 6k revs while kicking down. Never ever I asked to go so high but it's the ECU who did it. At other occasions kick downs went up to 4k to 6k.
I don't like a noisy engine as well but mind that didn't last more than a handful of seconds. And finally I should confess that a kick in the ass and an engine growling a few seconds gives a rather voluptuous feeling... Sorry I think I've got wicked pleasures !!!

[kaiser]

Originally Posted by Dorchester2

Thank you Simon.
Nevertheless thanks to the (modest) remap the power increase beginning around 4.4k revs it may be very helpful while overtaking. Going at my younger son's and back, along 1100 km (700 mls) 13 times I went over 6k revs while kicking down. Never ever I asked to go so high but it's the ECU who did it. At other occasions kick downs went up to 4k to 6k.
I don't like a noisy engine as well but mind that didn't last more than a handful of seconds. And finally I should confess that a kick in the ass and an engine growling a few seconds gives a rather voluptuous feeling... Sorry I think I've got wicked pleasures !!!

Ha ha. Sounds like your previous car was a 2CV.

[Dorchester2]

Originally Posted by kaiser

Ha ha. Sounds like your previous car was a 2CV.

Cheeky rascal how dare you?!
You aren't wrong nonetheless: twice I had a 2CV but they are long gone... The first was built in 1957...
The truth is never I had a 6 cyl. Only 4 at the best. The more recent ones being a 1991 214Gsi (destroyed) and a 2002 25 1.4 (my better half's daily).
I can't see any use of a 75 or ZT V8, given those awful & disgusting speed limits here: 50 mph on roads up to 80 mph on motorways. My lovely V6 is largely sufficient for that and I'm enjoying her every day I'm at her wheel and dreaming of her when she's garaged!

[kaiser]

Speed limits??
What is that?

I used to have an R4! actually I had three!
Take the whole back seat/bench out and enjoy a pick nick.
One wing nut, and the seat is out!
One even had canvas seats! No foam, just canvas.

Those were the days! Better than a bicycle, by far!

[Dorchester2]

Excellent choice, I'd an R4 as well (or 4L as we say here).
We overloaded her once along 350 mls with a whole wood kitchen kit: the poor soul back was very low but we arrived! It's of no use to tell that wasn't as speedy as my lovely V6 when driving uphill!!!

[Ahrle]

Originally Posted by trikey

Don’t forget different dyno’s can give different readings, I was speaking to a bmw owner who ran his car on two dynos a week apart, one showed 530bhp the other showed 590bhp!

Yep, afaik "rolling" dynos can make the wheels slip and therefore show wrong outputs. Drivetrain loss shouldn't be more than 10 or absolutely max. 15% for any 2WD vehicle.

[Dorchester2]

I fear I might slightly ramble but I'm still chuffed about my lovely 75! How amazing...
Here are the figures taken by Torque on the fly while I was overtaking and kicking down yesterday.
And mind that each time I'm kicking down I get a rough kick in the ass: it pulls hard and sudden!

Mind the headache!





To make a long story short at 6,535 revs I reached 129.41 hp at the wheels (I assume there might exist a very short delay - around 1 sec. - between the maximum power and the higher revs).
129.41 hp is equal to 127.64 bhp at the wheels.
Besides I understand that Rover 75 V6 2.5 engine efficiency (engine optimisation rating) is 72% as you may find at ​Specs Rover 75 2.5 V6 Auto 177 ps​​​ and as I was told here.
Then by a very easy rule of three 127.64 bhp at the wheels gives 177.277 bhp at the crank, that is the actual engine power and that looks the exact maximum engine power genuinely given by Rover!


Nevertheless back to the official remap figures given last summer, the pros got a better result on their dyno:
- before the remap 140.48 bhp at the wheels (6717 revs) hence 191.740 bhp at the crank,
- after the remap 146.202 bhp at the wheels (6277 revs) hence 198.250 bhp at the crank.
That difference might be solved because the conditions were different (on the road / on the bench) and that Torque may likely be not that bad but slightly approximate and delayed.
BTW I'm told that fuelled up by E85 (octane 105) and with my different mods (air intake box admitting more air, K&N filter & derestrictive SS exhaust line) TBH my engine should drive a tad better than in the first place.


How does that sound?

[bl52krz]

Seems as though you have a healthy engine there. I know my viz motors are working because we have a nice sharp hill near to us, and enjoy doing the acceleration trick on cars behind. Acceleration to 40 mph, and hold it at that, and then get the 3000 revs up and fly.. Surprised a few motors in my ‘old’ Rover.