[steak_knife]

Always had a the impression the the eng "de rate's" in 5th gear.

Can anyone smarter than me answer this??

I am aware that 5th is overdrive but that doesn't account for the loss of power even on flat road's..

Cheer's.

Oh.

[Gwagensteve]

I reckon it does.

Put 20% talller tyres on your car and see how much power you loose in 4th.

[alien]

You reckon that's to do with emissions testing? let's not forget VW owned a fair portion of suzuki for a while =)

[Gwagensteve]

Nope. With an efi car of G16b complexity it will move from open loop to closed loop at <80% throttle regardless of gear. Obviously egr is triggered too under similar situations, but that won't make the power drop off- it's happening because you're not asking for the power. Ask for the power and then engine will go back to open loop.

I still say it's gearing. Drive along at 80km/h in 4th with 31's on and then swap to 37's and drive along at 80km/h in 4th. I bet the car feels like it lacks power. That's the effect of shifting into 5th.

[steak_knife]

This is my GV, but since EFI became the norm I've always wondered why it needs to know 5th is engaged.

I do see what your saying MrG, but from 1 to 1 in fourth to a slight over drive in fifth doesn't account for the amount of power I lose.

A slight head wind will drop off 10kph.

Oh, I commute in a 100 zone H/Way everyday.

[Gwagensteve]

It looks numerically slight but if you think about it in terms of tyre size the % rev drop and according reduction in torque at the wheels.

There is no practice of "derating" of engines in overdrive that I'm aware of. EGR and closed loop operation can occur in any gear so long as the parameters are met (steady engine speed, light throttle, engine at temperature etc.

In fact the Ferrari 488 is torque limited in every gear other than 7th.

Steve.

[jdk81]

Drag is proportional to velocity in m/s squared.

So 80km/h (22.2m/s) to 100km/h (27.8m/s) is 493 compared to 773.

While the 20 km/h difference doesn't seem like much, it is actually 57% more drag.

A 10 km/h headwind effectively increases relative in air velocity by 10 km/h.
at 100 km/h a 10 km/h headwind will increase drag approx 29%.

It really sucks the power.

[steak_knife]

Sit's on 140 easier than 100 in fifth, but gotta get it there in fourth.

MrG I think you answered my question.

She has 225/75r16 on but when first fitted the only difference I noticed was the speedo was out.

Cheer's.

[jdk81]

At 140 in 5th, it's much higher in the rpm where the power is made.
So much easier to overcome the loses.

Any idea of the power curve?

[watermouse]

2L/4cyl GV or V6?

[steak_knife]

jdk81 wrote:

At 140 in 5th, it's much higher in the rpm where the power is made.
So much easier to overcome the loses.

Any idea of the power curve?

I drop's bugger all in rpm from fourth to fifth.

Nope.... I put foot down I want power....

[steak_knife]

watermouse wrote:

2L/4cyl GV or V6?

SQ625. can get a 2.7 but sierra need's coin first....

[steak_knife]

F*#K I'm an idiot, driving to work tis morn, I realised I pass through 4 different weather pattern's & end up in a stinking hot ( like Cairns) town...


What a tosser.....

[THE_DICTATOR]

What happens if you unplug the 5th gear thing?

[steak_knife]

THE_DICTATOR wrote:

What happens if you unplug the 5th gear thing?

Bout to do a clutch in the next week or so, I'll give it a go....

My last post was about the air temp sensor, only looses power in the low lands.....

[Gwagensteve]

I'd be surprised if there's a physical switch that's relevant (unlike EGR control on a carby sierra or vitara) ECU will control egr and closed loop operation based on VSS and throttle positon, not gear selection.

Id suggest more of the problem is due to the narrow torque band of the 2.5 V6 and factory gearing optimised for fuel economy with standard sized tyres.

The taller gearing and increased rolling resistance of the tyres will increase load and lower revs enough that it won't hold speed at 100. Your comment that it holds 140 in fifth fine but not 100 is proof it's a torque related problem not a tuning or ecu characteristic.

I dislike small capacity v6's for this- they end up very short stroke motors for their capacity and so manufacturers try to tune them for torque which results in peaky torque curves even though power and smoothness are impressive and exceed that of a comparible 4 cylinder. Compare a 2.5 GV motor to a 3rz for example.

[steak_knife]

Know of a GOOD piggy back then???

May just LS it...

[Gwagensteve]

One that increases stroke?

[steak_knife]

Gwagensteve wrote:

One that increases stroke?

Is the 2.7 a longer stroke???

Eng has to come out to fix an oil leak, so would rather put a 2.7 in than just fixing leak.

[squibby]

I'm going bigger tyres next week, so interested in this topic.

I've noted similar, the gearing on the SQ625 and power and torque delivery feel properly unusual compare to the 30 plus other cars I've owned. I can contently drive it using 1st 3rd and 5th skipping 2nd and 4th absolutely no problem, in fact the changes in rpm don't even sound or feel strange. This car revs relatively slow and will not be rushed when it comes to gear changes, it has only 155hp (not particularly great for a late 90's 16V 2,5 V6), AND YET most of the passengers will comment that it "goes alright doesn't it?" and actually it seems to have decent poke if you watch the speedo climbing instead of feeling for the power band or the next gear. It'll cruise at 50kph in top on the level no problem.

It looses speed rapidly uphill, and yet around about 2000rpm in 4th or top it'll pause loosing speed and you start riding the torque all over again. I had to drop the windscreen when towing my boat since it wouldn't hold 110kph with the wind resistance, and yet it'll tow the boat up to 100kph no problem whatsoever. Funny car, I like it despite it's foibles. Probably my second or third favourite car out of the 30 plus despite being a complete old crapper compared to many of the cars I've owned. Hope my bigger tyres don't mess up the 110kph cruising, I'm only going 47mm larger diameter.

[Gwagensteve]

I think so?

Another option is probably easier- regear to get the engine away from the torque hole. My guess is you have 4.3 now (?) gearing to 4.6 would transform it.

Steve.

[steak_knife]

squibby wrote:

I'm going bigger tyres next week, so interested in this topic.

I've noted similar, the gearing on the SQ625 and power and torque delivery feel properly unusual compare to the 30 plus other cars I've owned. I can contently drive it using 1st 3rd and 5th skipping 2nd and 4th absolutely no problem, in fact the changes in rpm don't even sound or feel strange. This car revs relatively slow and will not be rushed when it comes to gear changes, it has only 155hp (not particularly great for a late 90's 16V 2,5 V6), AND YET most of the passengers will comment that it "goes alright doesn't it?" and actually it seems to have decent poke if you watch the speedo climbing instead of feeling for the power band or the next gear. It'll cruise at 50kph in top on the level no problem.

It looses speed rapidly uphill, and yet around about 2000rpm in 4th or top it'll pause loosing speed and you start riding the torque all over again. I had to drop the windscreen when towing my boat since it wouldn't hold 110kph with the wind resistance, and yet it'll tow the boat up to 100kph no problem whatsoever. Funny car, I like it despite it's foibles. Probably my second or third favourite car out of the 30 plus despite being a complete old crapper compared to many of the cars I've owned. Hope my bigger tyres don't mess up the 110kph cruising, I'm only going 47mm larger diameter.

Most of my passenger's say "HOLY F*#K WHAT'S IN THIS THING!!!! (on dirt they just giggle & shit)

I took out the HUGE friggin muffler & put in a small sport muffler, sound's awesome & goes even better.

Cat's next....

[steak_knife]

Gwagensteve wrote:

I think so?

Another option is probably easier- regear to get the engine away from the torque hole. My guess is you have 4.3 now (?) gearing to 4.6 would transform it.

Steve.

But, but, but bigger eng!!!!!

Could go back to std tyre's but I like the limited clearance I have now.

[squibby]

Had a look online quickly the breakers I found asking over $2000 , and no doubt they'll want another $500 for the ECU. No thx. My other conversion only cost about $700 for the M18 donor. everyone wants to be millionaire and retire early now for selling anything.

[steak_knife]

squibby wrote:

Had a look online quickly the breakers I found asking over $2000 , and no doubt they'll want another $500 for the ECU. No thx. My other conversion only cost about $700 for the M18 donor. everyone wants to be millionaire and retire early now for selling anything.

A what???

[squibby]

Sorry, a H27A. Not even that low a mileage

[steak_knife]

Oh!!!! Wrecker's....

Heap's of wreck's up ere, can get a JB 2.7 wreck for 1800 complete.

Sq wrecks in every wrecker's to.

[squibby]

Sorry it's the English lingo in me, it still rears it's ugly head after 8 years in sunny australia

[steak_knife]

squibby wrote:

Sorry it's the English lingo in me, it still rears it's ugly head after 8 years in sunny australia

Thought ya spoke a bit funny