HELP! 2JZ-GE Strange Big Peak in Power

Roger UK

Member
Jun 20, 2010
67
0
6
Newcastle
I recently fitted a 2JZ-GE in my Mk3 Supra (manual with a W58 gearbox)

The way I installed it is pretty much as in a Mk4, using the correct ECU, igniter, MAP Sensor and Fuel Pump ECU, all from a Mk4 Supra. But both cats are removed, and using a stock Mk3 2.5" exhaust.

Generally I've been really pleased, it runs really well, everything is as it should be, starts instantly, perfect tickover, sounds smooth at all revs, no misfiring or anything, stays at normal temperature, plenty of oil pressure (we have a gauge on a Mk3 !), clean exhaust, etc etc, and pretty good performance.

But I have noticed something rather strange . . . if I am accelerating hard, full throttle, in any gear, suddenly when I reach exactly 3750 RPM it's as if someone flicks a switch.

Probably the best analogy I can give is that it's as if you've been driving with the HT feed only to 4 cylinders, then suddenly at 3750 RPM someone switches on all 6 !! It really is that dramatic, and also that instantaneous.

But it obviously ISN'T faulty HT leads, as it's not random - it ALWAYS happens at exactly 3750rpm, in any gear at WOT. (but not at half throttle)

I'm wondering what on earth this could be?

It obviously implies that something is WRONG at lower revs . . . but what?

I have checked the ignition timing, ruled out the ACIS by disabling it (although that changes at 4500rpm anyway)

That 3750 RPM must be a clue . . . . anyone who knows these engines have any idea?

(I've asked the Mk4 guys here in the UK, but nobody has any ideas!)

There's a picture of the 2JZ-GE in my car on this page HERE
 

Roger UK

Member
Jun 20, 2010
67
0
6
Newcastle
The Mk4 N/A Supras don't have a MAF Sensor (not the ones from Japan anyway), just a MAP Sensor, which I am obviously using.

And it's not a VVTI engine, by the way.

I have now sussed out the problem - I was getting too much of a voltage drop on the main power cable to the Fuel Pump ECU (due to trying to use thin spare cables inside the Mk4 Engine Loom for neatness - the Mk3 uses a power feed in it's Loom, but the Mk4 uses an external cable)

So at WOT below 3750 rpm the Fuel Pump wasn't getting enough power (with the reduced voltage due to my cable) and causing fuel starvation - once you reached 3750 rpm the Pump got full power, and even with my voltage drop, this was enough!

Now I have run a new external thick cable from my EFI Relay to the Fuel Pump ECU it's all working fine now - no weird effect any more - there's smooth power all the way up the rev range !