98/91 fuel, how much difference?

[Brett_jjj]

Hot days effect the cars power,not because of retarded ignition timing,but mainly because of the intake air temp, when the air is hot it gets thin,whereas cold air is a lot thicker or dense..The more dense the air is,the more power the engine makes because theres more air being "fitted" into the cylinder,which makes for a bigger bang..It is especially noticable on some turbo cars on a hot day..A good example is Nitrous oxide,it is a non flamable gas that makes the air going into the engine a lot denser,thats why it makes more power.

 

[2DIE]

Just went for a drive about 100km total, 50km on the way there with 91 and I was low on fuel so I topped it up with 98 before I drove home again.

Its back to how it was before, relived its back to normal and it was only the fuel that made the difference.

I would there be noticeable difference between 95 and 98? Its just a standard tune Ecotec.

 

[Brett_jjj]

Mate I woundnt even bother using 95,you may as well pay the bit extra and get 98.But its up to you really,I suggest you try them all and see what you think is the best.Also it doesnt hurt to put a bottle of injector cleaner in the petrol tank once a month or so.It seems to keep them running a bit better.

 

[2DIE]

Ok thanks, might as well just keep it on 98 then. I put half a bottle of injector cleaner in it a bit less than 2 weeks ago when I filled the tank.

Instead of making a new thread Ill ask something else here,

Where or who can test my speedo, will I have to get it put on the dyno to test it or can mechanics ect do it?

Only asking because I seem to be flying past every car where ever I go, I asked my bro to sit on 100 in his car and I flew past him too, when I asked if he was doing 100 he said he was doing 110km.

My tyres are fine according the the tyre/wheel size calculators, I doubt it has had the diff changed before.

I really need to get it checked and possibly recalibrated.

 

[Brett_jjj]

Im pretty sure some phones have GPS which can measure your speed.A dyno is another way,but too expensive just to get that done.Do you have the speed alert on the dash.Its also an electronic speedo,some speed alert units will set to the speedo mode permanently ,and some wont ,even though the units themselves are identical.The ones that wont, will still set to the speedo but the orange light will flash on and of whilst its in this mode, and when the ignition key is turned off,it will automatically go back to speed alert mode again.If you dont know how to set the speed alert to digital speedo,yell out and I will post up how.Its not very hard.

 

[2DIE]

My phone has GPS and a Speedometer function but I find it to be inaccurate also, the speed jumps up and down as much as 20km over and 20km under.

I have the speed alert on my dash, but when I hold the menu button and down arrow to bring up the digital speedo before I start the car its pretty much the same as what my normal speedo says, I think its roughly 2km under all the time.

Ill try my GPS speedometer a bit later and see what it says but in my last car it wasn't a very good way to measure my speed, constantly doing 80km down a road near me it displayed anything from 60-100km due to suspected lag with the satellites.

 

[Brett_jjj]

The only other thing I can think of is get a couple of mates to drive along behind or beside and measure their speeds against yours. Also setting the trip meter and passing the road distance markers along the highways will give you an idea of the speedo error,and whether its reading slow or fast.The speedo can be adjusted in the memcal to read slower or faster.I done a chip for a guy who wanted a tune done,plus he had fitted lower diff gears,and because of the lower gears, his speedo reading was out to buggery,along with the auto trans shifts..I changed the settings in the memcal and shes reading right,and the auto's shifting gears properly now too..The trans uses the same signal as the speedo.If you find out its out by a lot,then this might be an option to get it reading right again.Id try a different speedo first though.Yours might be faulty.The only thing Ive seen effect the speedo reading on these cars is tyre/wheel size, or when fitting different diff gears.So it could be worth fitting the standard 15 inch rims and checking it out to see how it reads then.

 

[2DIE]

Went 2 short drives just now, sitting on 50 the GPS read between 49 and 54 but mostly on 50.

The same happened on 60, it sat mostly on 60. Went up and down a tiny but only like 59 and 63.

Seems pretty close to spot on spending most of the time on 50 and 60km when I was doing the same speed.

I'll try it again in the next few days when I get to some 80/100km zones and see how it goes, so far its looking like everyone else is driving 10-20km below the speed limit everywhere I go.

I have standard 15's on it, 225/60/15. Stock is 205/65/15

Using this calc Tire size calculator

It says when I'm doing 60mph I'm really doing 60.3mph, thats not much really, about half a km or so.

 

[Jezza]

i think its just adelaide drivers because i find that on the weekend and on holidays that alot of drivers dont go the speed limit and drive alot slower then normal