What Fuel To Tune On?

[DaveB]

Ok so on the face of it this looks obvious - 98 RON is better fuel - less detonation etc. I have always used, and had my stagea tuned on, BP ultimate '98 (or the occasional tank of VPower )

However I'm getting a lot of pinging. A lot. It's shown up since I've had the engine rebuilt (another story...) and is actually worst under low load, and seems to get worse as the RPM goes up (still, low load). So cruising in overdrive it shows up all the time. If I accelerate just enough not to kick it down out of overdrive it gets real bad (so obviously I don't!)

I'm about to get a more thorough (I hope) tune done at a workshop with a new digital dyno etc. and the technician says he can recreate any load-point, so hopefully he can fix the pinging on the dyno. But I was wondering, should I put 95 RON fuel in for the tune, to make sure the timing is 'safe' enough... eg. for those SA summer days?

[KiwiRS4T]

I assume you have a Nistune chip? Use 98 fuel - a good tuner will sort out the detonation or pin point the problem if there is one other than the tune. BTW a technician who knows how to operate the dyno is not necessarily a good tuner! Had any comments from other users?

[bubba]

Was that fuel sitting around in the tank why the engine was getting built? Do you use 98 from dodgy non-BP servos?

[DaveB]

I assume you have a Nistune chip? Use 98 fuel - a good tuner will sort out the detonation or pin point the problem if there is one other than the tune. BTW a technician who knows how to operate the dyno is not necessarily a good tuner! Had any comments from other users?

Yes should have said; it's a Nistune.

I guess you mean other tuners? The workshop who built the engine have had a couple of goes; I'm not unhappy with them I just thought I'd try another tactic. They first found that the timing was set too advanced (needed to rotate CAS I think) and then I had a cat collapse which caused pre-ignition because it was blocking the exhaust and causing the load points to go weird apparently. But after fixing all that it still seems to have these big 'holes' where I get pinging. One of them is in overdrive, which is annoying.

Was that fuel sitting around in the tank why the engine was getting built? Do you use 98 from dodgy non-BP servos?

I've always used "BP Ultimate" since it was built; I replaced the fuel pump soon after the engine was rebuilt (like a week) - maybe the sitting had something to do with that. The pump was OK, it just wouldn't spin one day and I pulled it out and put 15V through it in a tank of kero and that cleaned it out. It's now serving well in a rodeo lol.

Thanks for the comments guys. I have recently upgraded the SMIC to a better SMIC () and I have booked a more 'thorough' (read as: more expensive) tune on Monday at another reputable workshop who work closely with Matt from Nistune, and the first thing the tuner asked was if the CAS sensor etc. had been checked. He said the first stage would be diagnosis. So have fingers crossed... I guess I'll put '98 in it. It's only another 4 cents/litre after all. Bah one day when fuel gets too expensive I guess I'll just have to sell the stag and get an i30 or something lol. But that's sacrilegious.

[wolverine]

New engine could/should lead to changes in static compression.

It needs a new tune anyway after rebuilding just to see what it is doing. If your fuel was old then that won't help but assuming you have refilled since it will work its way through quickly enough.

Definitely retune on 98ron.

[DaveB]

Cool, will do. Yes have been running like this for about 8-10 months.

[pixel8r]

maybe just tune it with a fair amount of tolerance...and then you'll be fine.

Manufacturers tune their cars to run rich for a reason...and whilst there is still plenty of leeway to lean it out a bit and still have a "safe" tune, don't be tempted to overdo it.

Tune for a 40deg day with aircon on and 95octane fuel - you could be planning a drive in the country (ie. no 98octane fuel available) over summer - who knows?

[DaveB]

Very true. The desired result (ie. 'sports car' or 'daily driver') needs to be made clear to the tuner perhaps?

Second the availability of '98 in the country... never take an import on a long trip without a bottle or two of octane booster!

[bubba]

Very true. The desired result (ie. 'sports car' or 'daily driver') needs to be made clear to the tuner perhaps?

Second the availability of '98 in the country... never take an import on a long trip without a bottle or two of octane booster!

I get over 550km/tank on country runs and I've got 2x20L jerry cans that get strapped in the back, I also plan my route around BP98 availability

[Dunc]

Very true. The desired result (ie. 'sports car' or 'daily driver') needs to be made clear to the tuner perhaps?

Second the availability of '98 in the country... never take an import on a long trip without a bottle or two of octane booster!

I guess it depends on your definition of long, I did a trip to the snow fields and back (from Adelaide) and never even contemplated it being an issue.. and it wasnt. Perhaps I was fortuante in that I started getting low on fuel near some of the larger country towns

[_Ryan_]

Was the comp upped?

[PetroDola]

i personally wouldnt put anything but 98 fuel in my cars. whats 20 cents per litre against the life of your engine.

and octane ontop of that on occasion.. bearing in mind jap fuels are octane 102+ (RON) which these cars were designed for.

also who else likes BP98? in my opinion its the worst of the 98 fuels.

my personal favourite is caltex -vortex 98.

and then secondly shell v-power

and bp probably lastly.

but like oils i guess people get different results for different motors. so each unto their own i guess.

can't wait to go E85 and forget about it.

cmon brisbane.. start selling e85 at the pump ffs!

Edited November 1, 2010 by PetroDola

[DaveB]

...I also plan my route around BP98 availability

lol!

Unfortunately it's starting to look as though the static compression went up. There is still a slim chance it's a faulty cam angle sensor; if anyone knows where I could borrow a NEO CAS unit from for a day so I could rule it out that would be appreciated If it's not that, well, then begins a bit of a saga to workout who will be sorting it out and who will be paying for it!

[wolverine]

I don't think the CAS is faulty it just sounds like it needs to be checked by a reputable tuner.

[DaveB]

Well I have had it checked by a tuner which I think is reputable, and I have a bill for a day's work to diagnose the problem. Which is not exactly pinpointed at this stage (but if they did any more work on it, it would probably be cheaper just to rebuild anyway). But I'm fairly certain it's either:

- cam sensor

or

- incorrect static compression

The latter requires a rebuild. They builld the CAS sensor and reset base timing because it was reading high at idle. They noted it semmed "lumpy" and said it may have a bent shaft or something like that. Timing seemed to be behaving but they didn't have a way to check timing at high RPM to verify it was getting what the computer requested.

So I could get a new sensor, and if it turns out to be not faulty then go ahead and rebuild. Or I could rebuild now on the assumption that it's very unlikely the sensor is at fault. I don't know the price of a sensor or a part number for NEO... I'm guessing about $400 from Nissan though Anyone have info on this sensor?

Edited November 2, 2010 by DaveB

[scotty nm35]

Why dont you tune it for E85, it loves high compression. Will also prove the sensor is fine.

[KiwiRS4T]

Why can they not check timing at high revs? Do they not have Nistune software? Sounds like your main problem is you're in the wrong city!!

CAS do go wrong and yes they are expensive. Try and find someone with an R34 to borrow one off. Try the general skyline forum under forced induction - someone may be able to help you. I wouldn't be in a hurry to rip the motor out without good cause!!

[wolverine]

If base timing is set correctly (and assuming the timing belt is not out a tooth or anything mechanical) it leaves the tune as the most likely reason.

Dave if the car is pinging it is running more timing than it needs. What changes has the tuner made to the car? Do you have any printouts of the AFR's? How much power is it making?

[DaveB]

Thanks guys,

no I don't have AFRs, the tuner did suggest I swap a CAS sensor to try it out (but I think the tune's been 'corrected' now to have all the timing pulled out; so it isn't really pinging anyway now).

they have checked that the timing belt is not a tooth out (pulled timing cover). He has Matt from Nistune there sometimes (in my case I'm not sure), and definitely has Nistune software. I think the only way to measure timing is from a data logging function which he said was telling him that all was well (ie. the expected timing of around 15 degrees advance at 5,200 rpm for instance).

I *think* if I understood it correctly, the issue with reading the high-speed timing was that it is measured through the nistune software, VIA the CAS sensor (which could be faulty). So I need to substitute or replace that (seems NEO stuff is rare as hens teeth so I may end up just getting a new one; he said the old one 'felt weird' like a spun bearing or a bent shaft, said it had a lot of play in it. So maybe replacing it is not such a bad idea).

[DaveB]

If base timing is set correctly (and assuming the timing belt is not out a tooth or anything mechanical) it leaves the tune as the most likely reason.

Dave if the car is pinging it is running more timing than it needs. What changes has the tuner made to the car? Do you have any printouts of the AFR's? How much power is it making?

Oh yeah, in case I haven't mentioned (thread is getting long...) I had the engine rebuilt and the head machined & rebuilt at the same time, January of this year it was finished. So it now has about 11,000kms since rebuild. This is another tuner that I have looking at the engine now, not the tuner who built the engine. They were... exasperated with the timing issues. 4 degrees maximum advance is apparently very low. When they started work on it all the timing had been pulled out to try to stop it pinging. So they completely remapped the timing from static and verified it matches what the engine is actually getting (verified at idle/low revs via a timing light). The engine just won't take any timing, and apparently the NEO RB25 'loves timing'; 16 degrees is possible at high revs high boost apparently.

Edited November 2, 2010 by DaveB