[30ONA]

Just wondering what potential there is in the stock j20 with a custom tune dynoed piggyback, full custom exhaust and snorkel?

I'd like to see more power at 2000rpm.

Gearing too tall for 2nd, too short for 1st for what I'm doing.

[Gwagensteve]

Far better, cheaper and more guaranteed outcome to gear the diffs lower.

[atari4x4]

^^^ this

5.12:1's are your answer

[Gwagensteve]

More specifically, there’s little that can be done to boost torque at 2000rpm. Advancing timing and pulling some fuel out is about the limit of what could be done along with tuning exclusively for 98 octane. Beyond that there’s retarding the camshaft, which will lower peak power but improve cylinder filling at low rpm. Would you notice the difference? Maybe. Will it be enough to overcome the wide gearing gap? Maybe not, especially if you give up some KW to improve the bottom end.

[30ONA]

Changing the diff will make highways horrible.

I do highway more than off road so would prefer not to kill highway speeds.

What's revs would I be at with those ratios at 100k's I'm already at about 3100

[30ONA]

Regarding my question in the first post, a piggy back can allow two tunes, stock and tweaked. So what gains might be possible? 15kw across the poorer band would satisfy me.

[Gwagensteve]

So you’re running stock sized tyres?

You won’t see 15kw. No way.

And I think you’re asking the wrong question. From what I understand You need a significant increase in torque at ~2000rpm. HP (Kw) is simply torque x rpm.

Trying in increase torque significantly at such low RPM will be very difficult becuase you’re working against the cylinder head design which is optimised for sylibder filling at around the intersection of the power and torque curves, so circa 4500rpm or so. Engines optimise for torque don’t spin high rpm, have small valves and long stroke. You can’t change the hardware so all you can do is advance timing to optimise the longer burn of 98 octane and adjust fuelling slightly. Expect a tiny change, well under 10%, and expect plenty of dyno time to be required to do it.

[30ONA]

I'm about to go slightly larger tyres but only within the legal limit.
From stock 27(688mms dim) inch to 28.7 (729). So this is going to drop the revs right? In all gears for the same speed.

Will this lower

[Gwagensteve]

Effectively reducing torque at the wheels further and widening the gap between the gear ratios.

[30ONA]

my issues have been running at about 45klm/h uphill in H4. What is a safe speed to drive in low range. Can I safely maintain 40-45Kim/h without killing anything?

[Gwagensteve]

45 km/h should be just fine in low range. I don't exceed peak torque in 4th in Low range, (and that's only my rule - plenty of people don't care and use all the revs in 5th) but even that should comfortably exceed 45km/h in a GV.

I'll add, (and I'm not nit picking) but you'll note where we've ended up vs where you started. Lets just say your first question was "my car has a huge gap between 1st and 2nd when climbing in H4 at 40-45km/h - is it OK to use L4 at these speeds" and the answer would have been a simple "yes"

Steve.

[30ONA]

Gwagensteve wrote:

45 km/h should be just fine in low range. I don't exceed peak torque in 4th in Low range, (and that's only my rule - plenty of people don't care and use all the revs in 5th) but even that should comfortably exceed 45km/h in a GV.

I'll add, (and I'm not nit picking) but you'll note where we've ended up vs where you started. Lets just say your first question was "my car has a huge gap between 1st and 2nd when climbing in H4 at 40-45km/h - is it OK to use L4 at these speeds" and the answer would have been a simple "yes"

Steve.

Yeah I realize that now. I appreciate you entertaining my line of questioning though because I couldn't find anything regarding the ECU thing so at least that question is still answered. Hopefully too if someone else is searching this thread should come up.

[ZUZUKI]

This is not an easy solve to the original question, by any means, but has anyone considered doing / done a J24 swap from a NGV into a J20 engined Vitara / Grand Vitara?.

Early version head cracking issues aside, the J20A in a late GV was good for 94kW @ 5,900rpm / 174Nm @ 4,300rpm, where the J24 in a NGV was 122kW / 225Nm.

Or...... sell the current car (if it is 2004, likely to be a SWB as I think the J20 was dropped for the 5door wagon by then, so might not be 'like for like') & buy a 5door, by which time (2004) the H25A was up to 116kW @ 6,200rpm / 213Nm @ 3,500rpm - with the option of upping capacity to 2.7litre from the XL-7 (130kW @ 6,200rpm / 231Nm @ 3,300rpm)

Rgs, Michael