Outer Limits 4x4 Board

I have a coily with a gti motor. I am having issues trying to drive it at 100-110kmh. 3rd gear sits at 5300rpm and 4th at about 4000rpm. the engine needs to be at about 4600rpm to hold speed (through inclines and normal driving conditions) so I find myself sitting on 120 odd to get the revs up.
Its never been a concern until yesterday where I did a 170km hwy stint and could not sit on the speed limit in 4th gear, let alone use 5th. Add to that my fuel consumption was way up...
My thoughts were either one of the following;
1. W/T xfer case with rockhopper
2. change diff ratios (unsure about coily avail)

What have others done, if any one has?

what tires are on it?

30" mud terrains, 40mm suspension lift and 50mm body lift.

I vote you have a problem with the motor. 4000 rpm shoudl be plenty to hold 100kph. Even my 660cc LWB holds 100 at 4200rpm..... with 34" swampers on it.

It should hold 5th at 3500 rpm too IMHO

Steve.

i have same sized tyres and a jimny engine(not as powerful as gti) and could hold 100km/h easy on flat ground but would be sluggish if any sort of hill. Now i have 4.9tcase and can hold 100 easy on any highway. My quess engine. Check your compression?

My Gti engine sits on 100km/h no worries at 3000RPM in my zook with standard 1989 wide track gearing in 5th gear with 235/75/15 tyres (speedo is out a little). Your motor is fudged I'm afraid.

my gti with stock gearing sat on 100km in 4th with 31' on flat ground 5th was basically useless unless you were doing 120+ any beyond level groundand i would lose speed or drop back to 3rd and abuse the goodness out of it. i think the gti can handle the abuse but i got sick of listening to it. i think if you can get the gearing to around 4000rpm in fifth it would be ideal and you would be able to grab 4th at reasonable revs to maintain roadspeed should the bituman become a little steeper.
steve loves the calculater so he can tell you what gearset to use to acheive this if you ask him nicely
jason

I don't know what busted GTi motor you guys got but mine can do 80km/hr in 5th at about 2500RPM and hold it easy enough. Fair enough it requires a far bit of pedal but it's not flat to the floor.

Your GTI engine might be a bit tired, I have to agree there, but won't a rockhopper only become effective in 4WD and therefore be pretty much useless for you on the highway?

I would have thought that if your motor is in ok condition, then, because of the size of your tyres (which you'll need to keep with the amount of lift you have), then you're gonna have to go with the diff ratio change.

Just my 2c worth. Good luck...

Rockhoppers lower both high and low range in a sierra.

To answer Mr Greens question - to run 4K at 100km/h with 31's you would need 4.6:1 vitara diff gears and a Trail tough 6.4:1 transfer. This would equal 4003 rpm with an actual 31" tyre. However, you don't have access to different diff ratios (unless you swap a front Jimny diff and find a jimny with 4.3:1 diffs- that's as close as it will get)

However, this doesn't change Grant W's problem - his motor is way down on power. As I said, even my 660 will hold 4000 rpm @ 100kph heavily laden on 34's, and empty will pull 100 kph @ 3300 rpm in 5th easily.

ATM you have way less power at 4000 rpm than a stock sierra 1.3. I've driven a swift GTI and know this isn't possible if the engine is healthy.

Do you have a check engine light?
Are you getting trouble codes?
What's the condition of the catalytic converter?
Is the TPS and VSS hooked up?
When was the last time you changed the O2 sensor?
Checked the timing lately?

Just some ideas.

Steve.

Thanks guys. Will investigate more this weekend when time prevails.. Did notice today that it feels a little "doughier" than usual up to 4500rpm. But doesnt get hot or use oil, and seems to be as usual in the top end. I should be able to trouble shoot from the microtech handset right? or is that just for tuning?

hand set is mainly 4 tuning and monitoring temperatures.
do a compression test first

So it's running microtech? Just an (literally) innocent question... why? Is it running coil packs or something else the stock computer couldn't control? Aftermarket cams? Boost?

IMHO unless there is a very good reason (i.e a big change in the engines V/E,) you won't beat the stock mapping.

I'd get it to a shop that has a dyno and is familiar with microtech and get it looked at.

Steve.

I have to agree, I'd go with the stock ecu unless there is big mods. Even series 2/3 GTi motors have numerous chips available to suit different cams. turbos and even blowers.

So how many cold starts was the microtech tuned with?

Programming an aftermarket ecu costs $$$ - it takes sooooo much time to get the drivability right. For some guy wanting to run 10 sec 1/4's at the drags it doesn't matter, but the real $$$ are n getting the car to run economically and drive nicely "under the curve" or when your not a full throttle.

I am sure that something has changed that's made you notice a drop in performance, but if you'd had a stock ECU, you could pull out the FSM for a GTI and check all the inputs/outputs and ensure all was well before you do a compression test.

Steve.

What series GTi motor do you have? Series one has the ecu control fuel only and not ignition and series 2/3 runs both so if it is series 1 then I'd say it could prbably only be running to rich or poor timing. If it was series 2/3 it could be more.

Does it blow alot of fuel smoke?

All this info and thoughts are great.

Some background info. Its a 1996 gti engine, apparantly culltus version or something ( could an engine number tell me this info) running a microtech ecu. I did not do the conversion, I bought it as is. It runs perfect in the high rpm (redlines over 7000rpm) and has a bucket load of grunt. (more than my 1.6efi W/T and 4age20v ute). Last dyno sheet has it producing 80hp at the wheels.

It has been a while since my previous sierra but my ute was fitted with S1 rockhopper and 4age20v giving me full use of 5th gear on the hwy, and my W/T before that had a 1L xfer and also gave me the use of 5th. Maybe I have been accustomed to this over the years.......

My sierra was loaded on the trip last weekend but was not expecting to drive in 4th at 125kmh (about 4600rpm) to allow for any inclines etc. I went for a squirt this morning and when its empty it does do 100kmh in 5th but does require downchanging at inclines.

I guess I am chasing gearing to prevent me having to use 4th. I dont mind it revving high, it does not seem to worry it, and its used predominately around town.

I am confident that its nothing major, its due for a tune and dyno so i shoudl assess after this.

I am in brisbane and dont know a reputable tuner for the microtech or gtis. Any recommendations???

.

talk to drew on here as his 4ag runs a microtech i think and should be able to tune it as he works doing this stuff now. in brissie also i beleive.

The cultas version has a bit more compression and slightly different intake manifold and exhaust with a few other tweaks. That seem like good power for a cultas so I can't see why it won't pull 5th at 100km/h.

Has it got aftermarket cams perhaps like bd14's that only make power way up high?

Grantw wrote:All this info and thoughts are great.

Some background info. Its a 1996 gti engine, apparantly culltus version or something ( could an engine number tell me this info) running a microtech ecu. I did not do the conversion, I bought it as is. It runs perfect in the high rpm (redlines over 7000rpm) and has a bucket load of grunt. (more than my 1.6efi W/T and 4age20v ute). Last dyno sheet has it producing 80hp at the wheels.

It has been a while since my previous sierra but my ute was fitted with S1 rockhopper and 4age20v giving me full use of 5th gear on the hwy, and my W/T before that had a 1L xfer and also gave me the use of 5th. Maybe I have been accustomed to this over the years.......

My sierra was loaded on the trip last weekend but was not expecting to drive in 4th at 125kmh (about 4600rpm) to allow for any inclines etc. I went for a squirt this morning and when its empty it does do 100kmh in 5th but does require downchanging at inclines.

I guess I am chasing gearing to prevent me having to use 4th. I dont mind it revving high, it does not seem to worry it, and its used predominately around town.

I am confident that its nothing major, its due for a tune and dyno so i shoudl assess after this.

I am in brisbane and dont know a reputable tuner for the microtech or gtis. Any recommendations???

.

maztech in springwood is a microtech dealer and has a dyno, there really good at there tuning

Oh and BTW an 86 model is a series one like mine. ECU only controls fuel not ignition, cams are hollow so they like to rev a little more, fuel rail is bigger than series 2/3 which is restrictive. Although it's not as easy to chuck on an SR20 throttle body like the series 2/3, and there is no chips available either. Series 2/3 have a chip to suit a stock motor that bumps the rev limit up to 8300