2JZ-GE torque dead spot

[Nim]

What is with the 2JZ-GE torque curve? I'm talking about the non VVTi models. I just drove a JZA80 SZ yesterday, and that big 'ol dead spot is so painfully obvious. What makes the torque drop so hard at 4500rpm?

Dyno sheet demonstrating what I mean.

Anyone got any ideas as to what causes the crazy torque curve?

[gianttomato]

'Tis where the ACIS butterfly opens.

When the engine speed is 4500 rpm or less and throttle valve opening is 30* or more, or engine rpm is 4500 rpm or more and throttle valve opening is 30* or less, the engine ECU turns the VSV ON and closes the IACV. At all other times, the VSV is off, so the IACV is open.

So dyno run = 100% throttle. At 4500 rpm, ACIS butterfly opens resulting in change in torque characteristics.

FYI, should be the same for the VVTi models - I have the manual here and the same conditions apply.

[Nim]

Thing is, the torque DROPS so much! And only seems to come back up slightly... I wonder what would happen if you kept the ACIS butterfly closed?

[gianttomato]

Try it and let us know....not hard to do.

[Nim]

You have ITBs on your 2JZ don't you? I'd be interested in seeing a dyno readout for that.

[Alchemist]

Not knowing a whole hellava lot about reading dyno graphs....anyway here is mine, it has some different scales on the side, so the graph may not be representing torque. My graph doesn't really drop off like some of the other 2J ones I've seen. Certainly don't notice it driving.

[1983supra]

My dyno graph shows the change in torque characteristics as well.

http://img206.imageshack.us/img206/7...oresizekm9.jpg

[gianttomato]

You have ITBs on your 2JZ don't you? I'd be interested in seeing a dyno readout for that.

Smooth, no lumps as you'd expect..


And here is the pic I was looking for a little while ago. Basically the valve acts to create a variable length inlet manifold.



With the ACIS butterfly closed, effective runner length is long, so this enhances torque. When the valve is opened, runner length is shortened. Seeing as the valve remains closed below 4500 rpm, torque is enhanced below this cutoff rpm.

HTH.

[Nim]

Alchemist, you can see quite a drop in your AFRs though... interesting

My dyno graph shows the change in torque characteristics as well.

http://img206.imageshack.us/img206/7...oresizekm9.jpg

Yours looks less like a drop when ACIS changes the intake, and more like the torque is dropping off normaly, then comes back on again once it's changed. Yours looks more like, dare I say it, VTEC. The Supra I drove really felt more like a turbocharger came on at about 5000-5500rpm, and just felt kinda lifeless before it, with quite the deadspot at around 4500. Very odd.

[takai]

Interestingly Rod's doesnt show this same dropoff. Ill let him post his dyno graph.

Oh its in Conversions not Club Members Rides. So here we go:

[Nim]

Hrm, so perhaps there's something wrong with some of these older 2JZ-GEs making the ACIS act a bit funny? There is no way the Supra I drove had the power curve shown on Rod's graph.

Oh wait...

QUESTION: 1983supra and Alchemist, are you guys using pod filter in the engine bay? Or running some kind of modded intake setup? What about Rod's? What kind of intake is that using? Perhaps a pod filter on these things is making the ACIS act a bit stupid? I know the one I test drove had a pod.

[Alchemist]

OK...

Alchemist(me) & 1983Supra both have HKS Pods with custom intake piping, CAI & boxes, we also both have extractors and cat back exhausts with High Flow cats. Both manual.

1983Supra also has a piggy back ECU, mine is stock ECU only.

Rods is stock airbox, practically stock, although I have a feeling it didn't have a cat at the time that dyno was done. Not sure on the rest of the exhaust. Rods is also auto, not that, that would change terribly much.

Also of note, at the time that dyno chart was done my car had faulty O2 sensors, which have now been replaced, don't have a graph of it in it's current running state.

[Nim]

I'd be really interested in taking a healthy JZA80 SZ out for a spin, just to see what they're supposed to feel like. Perhaps the exhaust and intake mods are making the ACIS act stupid then? You'd think it wouldn't matter though...

[Alchemist]

If it's a pod sitting just behind the clutch fan, with no other breathing mods I'd dare say it's slower, and less responsive than a stock SZ.

A Stock SZ, or SZ-R with < 150K Km's on the clock, should be pretty responsive, have plenty of mid-high power, and some low down torque.

I took quite a few fresh imported SZ-Rs with 60 & 70K Km's on the clock for a test drive when I bought mine, and they didn't disappoint.

Bought my car with 77K Km's, done 105K Km's now but still going strong.

[TheToyman75]

mmmm My torque curve is dead flat ! whats the easiest way for me to check if that butterfy is switching without putting it on the dyno. Does it switch on free rev ? Anyone else checked there's (Nathan ? )