Terrible Fuel Economy, All Usual Suspects Checked

[Cubes]

Cubes 72 degrees is too low? Damn! I do have a very large aftermarket aluminium radiator and breather tank setup, would that explain the lower temp?

Grigor just got back from holidays mate, trying to get the road tune sorted but I'm going to be installing bigger turbo/inj/afm soon so I dont want to do another tune (unless I can get it for free) just before I get the goodies in. Why would the 72deg be incorrect? Will have a check of the coolant sensor and give my tuner a call again.

Thanks for the help fellas, and keep the ideas coming.

Nick

If your running a genuine Nissan thermostat then yes its too low. Regardless of the larger rad the thermostats job is to retain a minimum temp. In near freezing temps where I've had to scrape ice off the windows the car still runs at 80+degree's.

I'd suggest your running either an aftermarket cheaper thermostat,a nismo thermostat or the original is shagged.

[stolen_s15]

OK, well I'll check it this weekend and see what I find.

Even if its a cheapie/nismo/shagged could that really explain the fact i'm only getting about 300km in the city driving normally?

[Cubes]

If its not tuned to suit then definitely. If you have said it has been then sorry I haven't really read the previous posts.

[J_Red33]

If you're going to go to the trouble of checking it. Get a new one put it in there & be done with it. The bolts on that thermostat housing are a prick of a thing to get to. Genuine thermostat shouldn't be too expensive, think I paid about $40 from memory (don't quote me) & they're very good quality.

Standard thermostat on R33's has an opening temperature of 76.5 degrees. So if it's anything below that (provided your sensor is reading correctly) it's definantely stuffed.

I would be surprised if it's the whole answer to your problems, since your economy is particularly bad, but it could definantely be one of possibly several contributors. The best thing about this is that every part that gains you economy will pay for itself fairly quickly in fuel savings.

Edited January 16, 2008 by J_Red33

[stolen_s15]

Well I'll check the sensor and chuck in a new thermo this weekend.

On the way to work today the car took 9 mins to get up to a temp of 65deg then it took another 15 to get up tp 72, so I'm hoping for a decent gain when i change the thing

[Cubes]

All though the thermostat is rated to 76.5degree's remember its in the lower rad hose and the engine temp sensor is in the top rad hose reading the spent water.

[stolen_s15]

Maybe I'll try and R34 thermo, seems to heat it up a little more.

[J_Red33]

I wouldn't recommend you go higher than the standard rating or you could have overheating issues instead. 20 minutes is way too long for it to reach 72 degrees in the summer. Sounds like the thermostat is definantely shagged.

My 33 was taking that long to reach operating temp in the summer & then in winter it wouldn't reach it at all. Changed the thermostat & it was up to temp in about 5 minutes regardless.

Fair call on the temp sensor location too Cubes. You would definantely expect it to be hotter where the temp sensor is located. So if it was meant to be reading 80 at the sensor when it's 76.5 down the bottom, that means when the sensor's only reading 72 degrees your thermostat it flat out at 68.5!

[mattxwa]

How do you actually read the degrees?

Is it basically the middle of the temp gauge in the dash?or is that gauge too inaccurate?

[stolen_s15]

You need a water temp gauge mate.

[stolen_s15]

Changed my oil last night and it had a strong fuel smell about it. Now Ray @ RE Customs told me to check my injectors/seals as it could be leaking (he said it had a bit of a rough idle, and a fuel leak could cause this). S15 Injectors will be going in this weekend, so I'll see if this makes a difference.

[J_Red33]

Seen leaking seals on these types of injectors before, although only once bad enough to be a real problem.

It's probably the worst thing about side feed injectors, if the lower seals on the intake side are leaking, you can't tell without pulling it appart. Not to mention they're an absolute pain to get out of the rail.

Must be a lot of unburnt fuel for it to end up in your oil. Are you down on power too?

A couple of quick tips with these too. If you find yourself hacking the philips screw heads, get some vice grips or something similar, clamp the head of the screw with them & turn the screws that way. Hex head screws are a better idea & I'd recommed you replace them with these.

Use a socket bit that fits around the head of the injector to press the injector out of the rail rather than try leaver it out from the top with screwdrivers, which could break them.

Thirdly, when you put the new ones in, lightly smear vaseline on the seals so that it pops in easy & properly.

Do all that & it should be a cinch

Edited January 31, 2008 by J_Red33

[Modena]

I got over 605 KMs out of my tank last week... 65% freeway driving and 35% local streets.

Light didnt come on so had another 40-50 K easy to go.

[stolen_s15]

Well I just did 350km out of 60L. 80% inner city driving 20% freeway, def not driving for fuel economy. Car is now making 250rw/kw @ 16psi on a hiflow, so i'm thinking it might be more how and where I drive that is causing me dramas. How i'm not getting less fuel eco with more power and no change to driving habits it beyond me.

I never got to change the injectors and check for a leak due to the car already having nismo 550's installed (nice little surprise) I still have not had a chance to change the thermo, but the car will no longer be doing daily duties shortly so I'm not too worried about it. On that point the I have changed the PFC settings so that there is no enrichment after 50deg (which the car reached pretty quickly) so I dont think this is my issue anyway.

Will be interesting to see what the temp to when the car gets a flogging at DECA or some other track style event. Might shed some ligth on what sort of thermo is in the car, cause I'm just to busy now to check it all out.

Does anyone have anymore feedback?

[siddr20]

What heat range plugs you using.

Could make a difference.

I found that heat range 7 was running more richer for somereason.

Put in heat range 6 and replaced my 02 sensor and my fuel milage is a lot better.

[stolen_s15]

Well I got my first 400km / tank today in 90% city driving in heavy traffic!!! :D

I'm now convinced it was 80% my driving and 20% mechanical (plugs, fuel/air filter, and O2) I drove the first 2/3 of the tank purely for enconomy (inj duty cycle basically never above 10%) but I couldn't keep it up and drove 'normally' the rest of the way.

Siddr20 I'm running NGK BK6EYA I think, will need to check when i get home.

[stolen_s15]

Did some coil pack maintainence last week. Araldyted, and electrical taped all 6 coils to within an inch of their life. despite the fact it was not having any major misfire this has made abig difference. The car is alot smoother, from idle all the way through the rev range. It may have picked up some power on boost also. The idle is still slightly 'lumpy', I have checked for air leaks all over the engine bay, none found. I'm starting to think the car has after market cams installed.

Anyway the fuel economy has improved again. I have got 220km out of an indicatde half tank. Again this is with 90% driving in traffic.

I'll post up the exact results when I empty the tank. I'm also going to take it to RE Customs and get it dynoed again to try and confirm/disprove my theory it has picked up some power.

[Bond]

After all this you still havent changed your thermo??

If it is infact running too cool then your doing a lot of damage to your motor whiles driving it no matter how much money you spend on oil.

[nuffsaid]

So what was the fix?

[stolen_s15]

Just a whole heaps of maintainance parts:

Cleaned AFM

Cleaned intercooler and piping

Cleaned injectors

New fuel filter

Cleaned Air filter

New 02 sensor

PFC TUNE big differnce

Correct spark plugs

Coil packs taped up.

Also changing my driving style helped alot, changing below 3k amd light throttle is the key.