Larry_g

I used to tune motorcycles back before fuel injection and have used tuning software on my ZX14. However, that is really basic by only adjusting fuel according to a matrix of RPM vs throttle position. I'd like to think I know enough to defer to experienced tuners when it comes to my cars. It worked in the past with my WRX.

I recently joined the LS3 ranks when I bought a used 2014 1LE in November. Shortly after, I bought a Rotofab intake and SCT X4 tuner from a vendor on another forum, I'll call him Tuner A. This purchase included a free custom tune for my setup (just the intake and 93 octane). After loading the tune, I did some data logging.

I immediately noticed a bunch of knock retard, pulling as much as 8 degrees in the upper RPMs. I sent Tuner A the data logs and he said it looks like false knock and to not worry about it. That's when I decided to engage Tuner B and emailed him some questions. His answers made more sense so I paid for a tune from him. Of course, Tuner B's tune had almost identical knock retard but he said to give it more time to learn.

The interesting thing is, I really preferred the throttle response of Tuner A but the one from Tuner B actually made slightly more power according to vdyno. I'm more interested in the driving experience than the numbers.

I then started to think maybe our 93 octane is not so good locally so I added octane booster and then tried fuel from a station out of town. Knock retard was significantly reduced, but not entirely gone, so I asked both of them for a tune set to 91 octane.

Tuner A sent me a tune modified for 91 and said I would see slightly less power. I did another data logging run and the knock was better but still definitely there and there wasn't really a noticeable drop in power so I spent a bunch of time reading online and studying the data logs.

It looks like I have a problem with fuel pressure tapering off on WOT runs right when the knock retard is most intrusive. I was able to see this on more than one log. See the attached image of the graph.

One thing I am still trying to figure out is the kPa to psi conversion on the data log. Using the google conversion calculator, the numbers on the chart make it look like I am only getting 20 psi and tapering off to 17. However, I found one thread where they mention that you have to take the SCT reading times 3 to get the actual pressure. This would mean it's running about 60 psi (normal) and tapering off to the low 50's (not normal?).

Once the weather gets better, I'm going to data log the stock tune and see if the fuel pressure still tapers off. If it does, I'm thinking that it should still be eligible as a warranty repair as I have done nothing to the fuel system.

The thing that pisses me off is that neither tuner felt the knock retard was important enough to investigate further, but I am glad I wouldn't let it go. I plan on more mods and tuning for the future but now I'm questioning the wisdom of these mail order tunes and wondering if I threw away money buying the SCT X4?

The tuners lock their tunes and it looks like I can't do much of my own tuning with the SCT handheld. I guess I'll have to see how their tunes do once the fuel pressure issue is fixed.

TLDR; Are there really any reliable remote tuners out there?

06MonteSS

Make sure you're using GOOD gas, it makes a difference..

mobil, exxon, sunoco, amoco, bp, chevron are best brands to use, with mobil and exxon being the best..

NEVER use Shell, costco/bj's, mom-n-pop, or no-name brands, as it's crap gas that tends to cause a lot of knock retard...

ChevFTW

Don't you have 98 octane in your area? That's all I've ever used and ever will.
91-93 octane in your high performance monster engine? Not sure if serious.

How are you having trouble reading and converting your fuel psi?
Maybe try measuring your psi and volume the old fashioned way. I measured my psi with a $20 gauge from ebay. 58psi on the dot. Measured my volume with that ignition on/off procedure. Think it was something like 300-380ml after 8 seconds..
I'd fill up a tank of 98 octane before doing that ^ and see how it goes.

I would ONLY buy a mail order tune if my car was completely standard + never planning on modifying or tuning it afterwards + read/heard a bunch of positive reviews about it from other people.

Larry_g

98 Octane is not readily available in this area. This is my daily driver so I need it to be able to run on the local 93. I am going to do some fuel pressure testing after I get a gauge and the weather gets better.

The idea on the mail order tune was to cover the simple bolt-on mods I make over time, intake, headers, etc. and then get a real dyno tune once I get into more serious mods like cam, heads, and/or forced induction.

ChevFTW

Well that sucks (regarding no readily available 98 octane).
I wouldn't bother with petrol engines if I was in your shoes, I'd be looking into doing a performance battery/electric motor swap lol. What's your engines compression ratio?


I thought those mail order tunes lock out tuners/people from tuning your ECU? So after you get a mail order tune, how would you get your car dynoed?

And umm, I'm sure you know this but just in case.. the mail order tune won't cover the engine mods you do in future (if you get the tune before all the mods), so you'll "have to" (you don't have to, but there's a chance that you could run too lean and fry your engine) get another mail order tune and tell the guy you want a custom one (because of the mods) and you'll have to log/record your driving so he sees what's going on with spark, timing, load, a/f... and even then he might still not get it right and then you'll have to sit there emailing him for days, trying to get him to re-do the tune for you for free since he didn't get it right and send him your ECU again which means you won't be able to drive your daily driver (unless you have a spare or he sends you one).....

Better off just doing the mods and then getting it dynoed. No headaches, no paranoia, no risks, no bs.

Larry_g

Depending on where you are from, I think your 98 is about the same as our 93 octane. Different calculation methods.

There are vendors that will send you a "custom" tune if you purchase the parts from them. Not ideal, but close enough for short term use. They just email me an updated file, I upload it to the handheld and then load it in the ECU myself. When I'm ready for the real dyno tune, I will use the handheld to return the ECU to stock and let the tuner use their own software for the tune. I can then sell the handheld because I won't need it anymore. However, any future mods will require a proper dyno tune.

LSX Power Tuning

iTrader: (4)

Depends on the tuner. We do NOT lock our tunes but others due.