Mods and MPG

[Courior]

as you might of read in the other thread i made my K10 SS is a thirsty little thing.... now i dont mind this if its MY fault with the mods i made, cause then i have a reason and i know how to fix it.. so im ment to get 50mpg, ok its an old car, say 45. Im currently getting 36mpg. now would the following mods really make ~10mpg difference??:

14" Alloys wheels with 185 tyres,
10" Sub, Amp, and all wiring,
2 6by9's on the shelf,
50% of the time i have 1 passenger,
10% i have more than 1.

 

[Jinata]

Bigger Alloys = More Weight
Sub = More Weight
6x9 = More Weight

anddd... after all its an old car. :s

 

[Courior]

Bigger Alloys = More Weight

i was thinking more that
bigger alloys = more rolling resistance and as they are bigger you need more power to turn them, therefore burn more fuel to get from 0-30mph say than with smaller wheels.

 

[sonic]

very true, mine is a lot more thirsty with the 15" on, hence my decision to go down to 14" wheels with narrower tyres.

 

[Courior]

but my question is... will what ive done hurt the mpg by -10mpg?

Cheers, i just wanna put my mind at rest the motor is ok, just i have silly mods.

 

[Arnold]

50mpg is achievable if you drive like an old granny! I'd say 36 is a more realistic figure. This figure will also vary depending what sort of driving you are doing - long/short - town/motorway.

14's wont decease the mpg by that much, it's not like you've upgraded to 18" wheels!

If your MPG gets to around 20 like my K10 did, then you know you've got problems. That was down to a dodgey carb.

 

[frank]

courier

those 185,s will have thrown your speedo out !
mine reads over now, with the 165/55/13.s on and i have to take it into account when working out my mpg.

 

[sonic]

what profile are the 185 tyres Courior ?

 

[ollyc98]

yeah i went up to 185's but with a lower profile so the overall diameter is the same.

 

[bens851]

yeah i have done exacly the same i have 195's, 15's but i have 35profile so they r exacly the same size as my origional steelies!! well aparf from nearly twice the width!

 

[Courior]

frank, i know about the speedo, i had 225miles to a tank accoring to the trip, i added 20 (10%) to make it back to normal. i think my tyres are 55 profile, im at work now so cant check. i bought them off speedle, maybe he can remember?

arnold - so your saying 36 is good for a 1.2 SS .. i know it has bigger head on the engine, so more wieght, all the goodies inside, more wieght, all the trim, more wieght etc..

 

[sonic]

185/55x14 tyres are only 2% bigger in circumference than standard, so shouldnt make that much of a difference to be honest.

 

[ollyc98]

Make sure all your plugs, leads, fuel jets etc are in full working order

 

[Courior]

Fordy did a big overhaul on my car and it so i rekon it to be in good condition, its only got 48K on the clock!

the only thing i can think of is the ECC system is failing somewhere. maybe the 02 sensor is screwed?

 

[ollyc98]

Dump the ECC system?

 

[Courior]

well fordy and ed rekon its well worth keeping, and they are the experts.. i jsut dont know what to do really. if my SS was running ok then i would love it, but everytime i drive it im more concertrating of how much fuel its taking, trying to drive to save fuel etc.. not enjoying it.

 

[superls]

Yes Keep The Ecc, Just Remove The Egr. It Could Be Your O2 Sensor, A Problem In The K11's I Believe

 

[Fordy]

it wouldnt hurt to change the o2 sensor for a new one mate

its just a basic single wire o2 sensor but get a ngk/ntk brand one as they are better than the bosch ones

 

[Courior]

yeah, i will get one tommorow and try it, then see how it goes. is there any way of testing them with a volt meter or something?? like wire it up to a V meter and rev the engine? i dunno.

Fordy, i have (i think i already said to u) a full non cat 1.2 system. If i put this on with a standard 1.2 manifold (drill a hole in the downpipe for 02 sensor), will this help with mpg/power?

cheers mate, i also sent u a pm, did you get it?

Cheers for everyones replies!

 

[Alienfish360]

yeah i went up to 185's but with a lower profile so the overall diameter is the same.

You still have more rolling resistance due to the extra width, and more weight in the wheel.

 

[Arnold]

50mpg is probably the maximum figure that car will do. Being a book figure, Nissan probably drove it very conservatively. As above, this also depends on the conditions you are driving, the roads, the weight, and how you use your right foot!

The Super S should still be very good on fuel, but it is the heaviest model of the lot (exc ST) I really can't see the wheels making much difference when it's only a minor increase. I'd follow the advice of changing the o2 sensor and see what happens there, but that's still quite a good mpg. As i wrote, mine did about 20 or less.

 

[SammoHung]

Driving style / habits too

1. How the engine revs are used during normal driving

Frequent & sustained higher revs (for obvious reasons) fuel consumption 4k rpm is double that of 2k rpm

2. Accelerator pump

Swapping from brake to accelerator allot ...or lots of pumping on the accelerator (demand then no demand) will cane MPG

In mechanical carbs, the accelerator pump squirts liquid fuel as the accelerator is moved downwards. This is to momentarily enrich the mixture before progression. Electronic controlled carbs normally have algorithms to mimic this too but have a more efficient progression algorithms.

There is a lot of liquid fuel in one pumps-worth compared with normal fuel vaporisation made at the venturi.

(i) Frequency
Since the pump squirts a full vial of juice when the peddle moved from the top to the bottom (W.O.T.) and refills itself when the pedal moved back up....a good tip is to avoid any unnecessary pedal up and down-ing

(i) Amplitude
Also, learn the minimum amount of acceleration press that is required for best acceleration with RPM, load & gear...ie in the sketch, if you’re riding 2-up and you know the car will respond and perform well in the green dotted section of pedal movement within a certain rev range, but that you find that pushing the pedal into the red area doesn’t really give you much more...then try to keep out the red area because this results in fuel squirting(!) that isn’t producing efficient performance (wasted fuel)....

The red section will constantly be changing with load gear & RPM...so you have to get the 'feel' for it.

Any use?

 

[Courior]

yeah i get that, and thats what i have been trying... the first tank full i thrashed the car (to get bad mpg to see how bad it could go. and i got 220miles (on the clock) and guage was at 1/4 left. then i tried going so gentle, hardly ever letting the revs go above 3K, was in 5th at 35mph. this gave me 230 miles on the 1/4 mark. now im using the revs and changing when i know i will have power in the next gear to keep me moving/accellerating at the same speed (basically changing when it says so in the handbook ). so not flat out, but smooth gentle accelleration. im on 70miles and at the 3/4 mark. so we will see!

 

[SammoHung]

Oh :-( at least you can elimenate that idea to then.

if you were on a std carb I would suggest new plugs & air filter....but youre on ECC right?

Could be worth trying a plug change (£10 ish)

Does the car 'feel' less spritely than it used to be?..or about the same

Does the combustion/ exhaust 'sound' wheezy or clicky??

 

[Courior]

since ive had the car it backfired when rolling off the throttle in gear or not. like its over fueling...

well ive been doing some thinking and i was about to just give up and sell it, but i think now ill just save up and put a nice carb on it (fordy if your selling lemme know!! ) and a better exhaust as the motor itself has just 48K on it.

 

[SammoHung]

Yeah definately keep and sort it!!

backfired as in an explosion from the inlet

or

backfired as in an explosion from the tail pipe

??

 

[Courior]

tail pipe, it "pops" on the way down the revs, and sometimes missfires slightly when accellerating very gently.

 

[frank]

courior

you usually get an overrun backfire if there,s a slight leak in the system, drawing fresh air when you lift in i think !

 

[Speedle]

since ive had the car it backfired when rolling off the throttle in gear or not. like its over fueling...

well ive been doing some thinking and i was about to just give up and sell it, but i think now ill just save up and put a nice carb on it (fordy if your selling lemme know!! ) and a better exhaust as the motor itself has just 48K on it.

dont go selling it you daft old fruit! ill drive up there myself and fix it if i have too!

 

[ollyc98]

tail pipe, it "pops" on the way down the revs, and sometimes missfires slightly when accellerating very gently.

Cars aren't meant to do this??? lol I always thought it gave the car a racecar feel lol.

 

[Courior]

speedle after Xmas i may take you up on that offer in exchange for a place to crash and some beer lol . also lemme know if you can get hold of another carb/mani setup on inlet, and a standard 1.2 exhaust mani.. then we can have some fun

 

[daveeeeee]

if your gonna go about changing the carb why not go for an uprated one

lol suppose that completly contradicts this thread.

 

[Courior]

well the kinda carb speedle said he may offer would be an uprated one.. i wouldnt mind 36mpg if i was getting more than stock performance!

 

[PeteST24]

Cars aren't meant to do this??? lol I always thought it gave the car a racecar feel lol.

Small little pops are ok, thats just the way the gases are escaping. But bigger pops and bangs usually mean that fuel has detonated in the exhaust which sounds cool

Overfueling or bad spark can cause the fuel to detonate in the exhaust. Dont think it will do any harm to the exhaust though.

 

[ollyc98]

Mine is running quite rich, but that's less damaging than lean so I'll leave it that way.

 

[Speedle]

speedle after Xmas i may take you up on that offer in exchange for a place to crash and some beer lol . also lemme know if you can get hold of another carb/mani setup on inlet, and a standard 1.2 exhaust mani.. then we can have some fun

i have a spare exhaust mani now mate you can have that next time im at the scrappies ill try and find you another carb, although i do have a 1.0 hitachi carb which has bigger jets than the 1.2 carb (believe it or not) that would prob be ideal for your car and mean we could remove the entire EGR system which would increase power whilst still maintianing good MPG

 

[Courior]

Sounds good speedle!! i want rid of the EGR but i need another inlet manifold then as when we remove it i'll have a hole in my inlet mani.. Im going to scrappy (bridges) on saturday, what carbs will straight fit my car??

also if i put a webber/hitachi or other non ECC carb what part of the ECC system will i still have in use???

Many thanks!!

 

[ollyc98]

Sunny carbs fit.

 

[Speedle]

Sounds good speedle!! i want rid of the EGR but i need another inlet manifold then as when we remove it i'll have a hole in my inlet mani.. Im going to scrappy (bridges) on saturday, what carbs will straight fit my car??

also if i put a webber/hitachi or other non ECC carb what part of the ECC system will i still have in use???

Many thanks!!

removing the EGR will cause no problems, TBH i think the ecc carb on a standard inlet would be best.

however the only carbs that will fit the k10 that i know of are the n13 sunny 1.3 carb. i have not tested the others so saying sunny carbs fit is not corrrect only the 1.3 is one that i know fits.

i went to brigdes last weekend wasnt a great deal of k10 stuff there, got a spare super s spoiler tho which i should put up for sale

Sunny carbs fit.

no only the 1.3 carb is Known to fit as it the only one ive tried so far

 

[slyboogie]

speedle, got a pic of thats spoiler? what colour and how much + P&P?

 

[Courior]

Well i kinda sorted the problem/found there was nothing wrong with the car. all this with one more mod!!!

DRIVE LIKE A GRANNY!! 65mph for 70 miles on A3 ment i got 50+ to the gallon!

 

[Arnold]

See, it's down to the right foot - which people usually forget! Micra's are very good if you run them around 60mph, anything higher and they start to drink quicker! Old people drive them slow to save fuel perhaps lol.

 

[Courior]

But no matter how easy you are with the right foot, and coasting to red lights, keep revs low etc... its still around 35mpg in town! but i do loads of short trips and dont let the o2 sensor warm up, so my ecu thinks it aint got one and as fordy says uses extra fuel for some reason so that explains a lot. i love me car now.

i have installed a stealth shelf and dvd player now