RB Tuning - software,fuel used, and target a/f's.

[evilgtr]

With such a vast variety of tuning software. Professional tuners, and self taught tuners I thought we could put together a thread of what software you are using, the octane of fuel with or with out additives and the air fuel range you have had your car tuned at with either dynoed whp or estimated hp output. This will not be another thread specifically for dyno numbers but more so to find the optimum tuning range in which RB's operate.

Recently there has been alot of discussion on where individuals target there a/f's along with how much boost and timing. If you have any first hand info on Japanese tuning or your personal tuning please feel free to share what's worked for you and what hasn't

All input is welcome
Thanks
Jeff

[evilgtr]

Il start off
Engine RB26 stock displacement
Running 16psi got me 520whp/480lb.ft with wot a/f ratio of approx 10.9
Which I have now been told is to rich and could be potentially costing me hp.
I'm running the Vipec v44 on Mohawk 94.

[sullivanracing06]

rb26
aem ems
aem 3.5 bar map
14.7 psi 571whp
precision 1000s
93 oct

[evilgtr]

Wow that's huge power for low boost, what's your turbo setup ?
Do you know you a/f at wide open throttle ?

[NismoS-tune]

16 PSI on T04Z SPL turbo or -10s or whaaaa?

Il start off
Engine RB26 stock displacement
Running 16psi got me 520whp/480lb.ft with wot a/f ratio of approx 10.9
Which I have now been told is to rich and could be potentially costing me hp.
I'm running the Vipec v44 on Mohawk 94.

And sullivan, is that on pump gas with a giant turbo? That's 1 bar pretty much lol must be a stoic tune?

rb26
aem ems
aem 3.5 bar map
14.7 psi 571whp
precision 1000s
93 oct

[NismoS-tune]

Oh, it's too rich depending who you talked to. Your tuner made it that way, like all cars that come through there. In japan they tune super sharp with nice AFRs but in Canada, it's different I guess. Have you talked to other tuners or other guys with opinions about your AFRs? What did Jurie Human think? Ever talked to him about it?

Il start off
Engine RB26 stock displacement
Running 16psi got me 520whp/480lb.ft with wot a/f ratio of approx 10.9
Which I have now been told is to rich and could be potentially costing me hp.
I'm running the Vipec v44 on Mohawk 94.

[evilgtr]

Nismo-stune - Bim trying to find out what my air fuel should be that's why I started this thread, I think it is to rich to. Where do you think it should be ?

I sent Jurie a few texts but havnt heard back yet

[NismoS-tune]

I made 302whp on a very healthy but stock engine with 1bar, same PSI as the guy with 571whp lol. Same tuner as you. Most likely same AFR. I expect to nearly double that next time

[Blackzenki82]

R32 GTR
stock R34 RB26DET
AEM EMS
GM 3 bar map sensor
T61 twin scroll
XS Power mani
TiAL 38mm WG
Trust 4" FMIC w/3" HKS piping
93 octane

car made 400whp/347wtq @ 12.5 PSI


your target AFR's should be:

15/16/17 at idle
14.7 cruising
12.0/11.5 @ full boost/WOT

running that rich under load/boost, you're loosing HP.






i can vouch for sullivanracing06's power BTW... he is making that, pretty sick set up... and yes, on pump gas...

[evilgtr]

Blackzenki82 thanks for the insight, the consensus is my a/f's are to high so when I re-tune in the spring with my new mods I will be targeting a higher a/f. I still dont understand why it's so rich, does this reduce the chance of detonation ? Provide a safety cushion ? I know we did pull some timing out from the original tune of 540 or 550whp so it would be a little safer. It's still fast as **** so I'm notcomplaining I just want to make sure everything is dialed in properly and running the was it was designed to

[Blackzenki82]

a cushion would be 11.5 AFR at full boost...

the richness could be any combination of things...

most factory cars run on the rich side of things, for safety reasons, the whole "better too much than too little" kinda deal... to ring out the most power you can, you want your AFRs dialed in, and spot on, and STAY there...

10.9 isn't all that bad really, but 12.0 should be your target, you'll notice a smoother boost/power curve...


i have no knowledge of jap tuning, although i know that jap tuned ECU's tend to run a bit weird on US or CAD cars, i think it's something to do with different octane ratings over there, but don't quote me on it...

[GTR-Dad]

In general, if an engine is tuned and operated so there's no unplanned ignition (preignition and detonation are the big ones), peak cylinder pressure is 12 -14 degrees past TDC, peak rpm is (soft) limited to a value within the operating range of all components, and temperatures are well managed you can put ridiculous amounts of power down for a surprisingly long time without super strong components.

Fueling relates to combustion efficiency and cylinder temperature management. If you were to graph, for a given engine load, exhaust gas temperature vs AFR, you'd find EGT increases with AFR until a little leaner than stoich, then starts to drop again. We're really only interested in the richer side of the curve so I'll limit comments to that region.

Both power and EGT will increase as the mix gets leaner, but as temperatures climb, the risk of detonation and exhaust tract damage also increase. The tuner's job is to command an AFR and ignition advance that will produce a balance between power and reliability.

In general, ignition should be advanced until torque stops building. On forced induction engines running on pump gas, ignition advance is typically limited by the knock threshold, so there are gains to be made by increasing octane or improving cylinder cooling. Cylinder cooling can be improved with better charge cooling, injection of water or methanol, or by adding fuel. Adding fuel is probably the least effective of these options, but is always available.

That said, You'll never double your power by leaning out the mix. Cam timing is probably the culprit on a car making 300 hp on 15 psi.

Some tuners love to brag about how much power they made on the dyno, while others prefer to brag about how many of their cars finished in the top bracket of whatever motorsports they race in. The first will be biased toward a 'razor sharp' tune and the second will be biased toward reliability, typically by leaving a degree or two of timing advance or a bit of AFR on the table.

Remember, reliability wins more races than a few more horsepower. Choose whether you'll listen to the advice of someone who tunes engines for a living, or some guy on the internet. (Including me!)

GL!

Dan

[NismoS-tune]

Excellent write up Dan! Clears it up for me anyways. As for the 300hp on 15psi lol that's on a stock engine with good compression, oem head too. Only real mods at that time was (nismo plenum, tomei manifolds/outlets, nismo DP, no CAT, and -5 turbos. AFRs around high 10 if I recall. I don't know why it's so weak but I guess that's why I rebuilt every inch of it now.

[LIGHTSPD]

AFR is such a large question and unfortunately there is not one right answer. Anyone who says there is does not take the unknown in to account. The internet has become a treasure chest of information but you have to sort through the fools gold to find the truth. Tuner A says the AFR should be (insert expert number here). Is this the correct AFR though?

I have to ask myself alot of questions when I set up a car. Is this a track only car? Is this a street car? Will this car be abused (not used at full potential there is a difference)? Will the owner go out and do alot of long sustained highspeed runs? Does the owner recognize when they have got cut premium(it happens all the time not going to list out stations but I see it at least once a week.)? Will the owner substitue fuel in a pinch but not be able to control themselves? Is the owner a racer, driver or just an enthusiast? Last of all a common sense rating of the client? Why do I have to do this after all I am just the tuner? Alot of responsibilty is placed on the tuner for everything and as a tuner when the car leaves our possesion we have no control over the fuel used, mechanical upkeep and most of all the driver. What does this all come down to I can't control HEAT.

HEAT breaks everything it brings our engines closer to the detonation threshhold. Pump gas tuning it like playing with a loaded gun bad gas, different octanes from station to station etc it is an uncontrollable variable. The owner is the other uncontrolled variable and a super long highspeed run could result in uncontrolled heat.

Detonation basically boils down to heat. When we tune an engine we run our cylinder pressure to the max for our fuel. Now when tuning a race gas engine you can actually lose power by having to much timing without getting detonation. In otherwords on racefuel you will hit MBT without getting detonation many times. On pump gas you will get detonation before MBT. Each tuner has there own style and what works for one is not what another necessairly believes as well. I balance cylinder pressure and AFR out to do give what I believer to be the best possible combination. This is a huge toss up is it better to run less timing and leaner AFR or is it better to run a richer AFR and more timing? I have tried alot of different things over the last 14500 hours I have logged on the dyno. This is where a tuner makes decissions based on engine type and use etc.

The other thing is to take in consideration. Until only a few years ago widebands were unafordable for the average user. Widebands that are in your car are a good monitoring device and should in no way be considered as the gospel truth. It is a tool to make sure you are not having a problem. In the shop I use 3 high quality widebands they all read within .1 of each other which could be cause by sampling rates. I can tell you that most of the cheaper widebands read .4-.6 richer than what they really are but not as a scale it changes all the way through as we tried to calibrate an Innovate to read the same as my higher end Lamda meters, but not always. If cheaper widebands were 100 percent accurate I wouldn't keep using a wideband that the replacement cost on the sensor was $425USD and has to be ordered in from Australia. So what you are reading is not necessarily exactly what is there. So the AFR question is still out there.

Lets put another thing on the table. How much actual useable power does a leaner AFR create and we can be real generous here. I would say 35 whp. How much did your motor cost? Tell me how close to the edge do you really want to be. If you want to set records and have a budget that allows that lets take it to the edge. I just thought of something if you have a budget that can allow for a motor here and there maybe just run racefuel.

So what is the right AFR it is a balance that really doesn't have a right answer. For the record on most street cars I target 11.4 until higher RPMs then I target slightly richer.


Cheers Cam
Lightspeed Innovations

[Skym]

About varying octane of gas, I would think that's why factory ECU has main, knock maps.

I hear Link ECU's can have a additional knock module? and have to tune frequency of knock into ECU, etc. I would assume ViPEC ECU's are similar and have the same capability.

I noticed in Japan they tend to stay rich and use ignition timing.

From what I understand, with higher octane fuel it burns slower so can rotate crank more to move piston (past TDC more) before firing sparkplug and get no knock (unstable combustion). Lower octane fuel is the opposite.

Ideal (safe) A/F ratio at peak hp for stock engine is around 11.6:1 and have seen tuner use this without problems. Idle should be around 14.7:1 with stock engine.

Once you add cams, engine has to be run richer throughout powerband due to more air entering engine via cams. But cam specs determine how rich you run engine, as they determine how much air enters engine.

Also when switching to different fuels, A/F ratio's change. Ethonal, Methonal, Nitro require more fuel to be injected over what you normally inject with pump gas.