mx5cartalk.com

Hey guys.

So this is a power run of my car from the previous owner

Just after a bit of feedback about it so I can understand it properly.

360nm seems like a massive torque figure for only a 1.6L with 130rwkw. Should I ignore this as I have heard many tuners dont set up their dyno for accurate torque readings.

I realise every car is different but I have seen other mx5s run higher power with less boost. What might be the reason I'm running 13 psi for only 130kw.

I'm running a stock 5 speed and open diff. Torsen is 1st on the list.
2860 turbo, intercooler, 3 inch exhaust, rx8 injectors.

How do the curves look? Safe? Reliable? Well tuned?

Regarding the torque.

Wheel dynos are just measuring the torque at the wheels, which has been multiplied by the gearbox and diff.
Assuming the run was done in 4th gear (on a 5 speed it's 1:1) the main multiplication is due to the diff.
That's a pretty simplified explanation, i'm pretty sure it's been explained elsewhere on the forum in a much better way than I've done here.


As far as the kw figure, there's heaps of stuff that can affect the reading. Diff ratio, wheel size, tyre size, air temp, humidity, etc, etc.
http://mx5cartalk.com/forum/viewforum.php?f=43

Have a poke around there and see what other similar setups are making, noting that it will never be exact. (and note that a hub dyno will read higher again)

hks_kansei wrote:Regarding the torque.

Wheel dynos are just measuring the torque at the wheels, which has been multiplied by the gearbox and diff.
Assuming the run was done in 4th gear (on a 5 speed it's 1:1) the main multiplication is due to the diff.
That's a pretty simplified explanation, i'm pretty sure it's been explained elsewhere on the forum in a much better way than I've done here.

I'll have a look around but thats a good start, cheers

I just don't want to blow things up if the torque is stupidly high. I assume the forces in the engine are much lower which is good to know

PM Okibi or a mod.

They can move the whole thread/post rather than delete.



But alos worth noting, this section is more active than the dyno one.
The Dyno one is a bit like that corner in the back of the shed, the one where there's the old mop, a few dropped screws, and a small leak. Yeah there's useful stuff there, but most people forget it's there until they need it.

It's the right spot.

Torque readout is wrong.

We don't know if the AFR or the timing is any good from that graph but there is at least 60rwkw left in it. With AFR left off the graph I assume that it's passable at best and no doubt timing is weak as hell.

Dann

Afrs are in the 10s sometimes 11s on boost. I guess the tuner ran it a little rich to be safe.

At some point in the future I'll get you, Dann, to put a proper cat and tune on it to pass emissions. That'll be the time when I'd like some more power out of it

If you come down I'll turn it up for a lot less than engineering.

10's isn't safe, it's lazy. It's got a good modern ECU and can hold 11.6-11.8 all day. There is no such thing as a safe tune, just the right tune, and another tune.

Also, the car is only on like 10.5psi at redline where you make max power. It really needs 15-16 up there. It has 13psi, but only in the midrange, where it should have 10.

Look at this dyno again:



See the point at 95kph where it makes 90rwkw? We will calculate the torque at this point, it seems to be the highest torque part of your rpm band.

So we take 7200rpm (redline) and divide by 150 (kph at redline on the graph).

7200/150=48

That's rpm/kmh

Then multiply by 95 (the kmh at that point of peak torque I already mentioned)

48*95=4560

Now plug that into a hp/tq calculator (because I cant be bothered doing it longhand).

121hp@4560rpm = 140ftlb

The limit for longevity is around 220ftlb tq.

Why you're making 140ftlb at 4500rpm/13psi instead of nearly 200 is going to come down to the tune or some mechanical failure.

Dann