[Scythe]

I have been building a SWB 1994 Vitara hardtop up for some time now, and I keep hitting the same impediment to improvement. Despite significant effort (and 4 different motors - 1.6L EFI) I believe the vehicle is still quite shy on performance. The latest motor is well balanced but lacks any punch. I am only running 235/75/15 tyres (29ish inch), and have tried many different tune ups, including Dyno. I understand the engine isn't big, and it is pushing some extra weight with a ABR winch bar, dual batteries, and a tiny Runfa winch (Dyneena rope - all only 18kg), but all this does not seem to account for the poor performance.

I have low range gears in the transfer case, which is fine in the bush, but no help on the highway. This is my daily drive, so stop start driving is common, and somewhat annoying with the current configuration.

Is poor on road performance in such a vehicle common?

I have identified an option through http://www.4xfourart.com/ to buy new diff gears. These would take my 5:12 ratios to 5:72. I believe this may improve the motors performance and imprve the vehicle both on and off road. However, before I commit to the significant expense of buying and installing these gears I was hoping for any advice or opinions on this option.

Has anyone tried these gears?
Is changing the ratio likely to give me the performance benefit I am seeking?
Would it be better to spend the cash on an engine improvement?
What is a good option for an engine improvement?

I have already done all the usual stuff to the motor. (ie: extractors, bigger exhaust, high flow cat, snorkel/cold air intake, Dyno tune) I ain't too fond of the turbo option on an engine that already needs high revs to get going... (not preferred in a 4WD) but it remains an alternative option.

I look forward to hearing from anyone in the collective braintrust

[christover1]

Had my eye on them diff gears for a while.
I reckon they would help heaps on road.
But added to low range gears may render low range too low for 29's.
This is why I never got round to trying them.
If I'd found them before doing tranny would have got them instead.

I don't know anyone in Aus who has tried them.
I did find good reports in Europe web sites.

[Gwagensteve]

Put stock sized tyres on it for road use. You'll get a staggering amount of performance back. - Try it at least as an experiment so you know how much of a deficit you're starting with.

You're running tyres around 10% bigger than standard. Most big car owners whinge about poor road performance if they are running 35" tyres with stock gearing and power.

I'm not sure I'd try those 5.72's. You'll actually be revving a bit too hard on road, and with the transfer gears already in, I reckon the gearing will be stupid low off road. 87:1 crawl with 29" tyres is going to suck on greasy hills.

Steve.

[larry]

the cheapest and easiest option is as steve said: run two sets of tyres. if you decide to do that it only makes sense to step up to a 31 for offroad as your already geared for them and its a great improvement in capability over 29's

tbh i think your expectations from the 1.6 might be a bit high. i used to run 32s for offroad and then put 30s on for my daily tyres to get some punch back haha. surely the 235s cant be toooo bad?

[Scythe]

Good comments, so thanks all so far. I understand the dual tyre thing, and I have tried it before. I really doesn't work for me. You always seem to have the wrong tyres on when an opportunity presents itself. so i will never take that option again. I am also prepared to accept extra road noise and greater tyre wear from the muddies.
I would like to be running 30 or 31ish tyres, but don't want to go further if the motor/drive train struggles.

I have a Vitara 1989 softtop 1.6 (carbie) that is mostly standard, and it goes at least as well, if not better than the EFI. Considering the extra work and upgrade to the hardtop, and the extra power from the EFI it seems to me that I should be getting more from the EFI than the tired old carbie.

Still considering the gears....
Would be happier if I knew someone who had tried em.

[VonDecoy]

I think there's a few Vit owners on here that have looked at those Diff gears. Me included.
Thus far no-one has decided to be the "test case".
I'm too poor to worry about it.

Although like Chris wrote above I have heard/read good things about those gears.

[droverdave]

They arent supposed to go fast though. Does it sit on 100km/h on the highway alright?

[Scythe]

ATM, with the 29's, the car sits on 4k revs at 100kmph in 4th, and about 3.2K revs at 100kmph in 5th. There is no particular issue with highway speed, and it pulls 5th fairly well on flat roads. It is taking off that is the concern. I struggle to use H4 in sand, even if it is not very soft, and doing long easy sand sections in L4 at any sort of speed isn't good, especially with the rock crawlers slowing things down further. On the road, taking off at lights on a hill, or crawling up hill in stop start traffic is quite bad, and involves lots of revving, and some clutch riding. Again, not so good.

I would not like to give the impression it is bad. I would just prefer it to be better, and I am willing to pay for an improvement. I am however, not keen to pay for something that just makes it worse.

Someone must have tried these gears. Where are you that someone????????
Or.....I am still taking motor improvement options.

PS

Good to hear from some familiar names from the VIC Suzuki club on this new (to me) forum. I must get along to another meeting one day and see whats happening. Did you know one of your old club members rolled his Hilux ( off the side of a mountain in the high country recently? It went over 5 times and crashed roof first on a tree with him pinned in the vehicle. No one hurt (wow).

[atari4x4]

droverdave wrote:

They arent supposed to go fast though. Does it sit on 100km/h on the highway alright?

this guy