is my afr a bit lean/unsafe at the end of the revs? dyno print outs


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had my new boost controller set and the mapp checked, for soem reason he could get the fueling bang on as not enough ajustment with the emanage?? but said it was still safe, it wasnt detting at all when on the dyno but worried when on the road under load ect ect it may be diffrent

is it safe or is it a bit to lean

bit paranoid now that it will blow,


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if its the bold line i would say thats very lean from my understanding! i would have thought 11/12 on boost...


Looks a tad lean to mean on a standard motor. Me personally would prefer a bit richer.
Hence the reason i asked in your other thread if it was a standard engine ;)


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thats what i thought, i think it would be alright but looks as though it would be a bit safer if it was a tad lower..
seems to richen between 4900-6..
if it was me i would want it a bit lower for piece of mind tbh, but im sure it will be fine :)
reguardless if its a standard engine or fully forged out the afr's would still be afr's.. in any case this is how i see your graph and how i do my customers cars and mine aswell. first off you want some what BIG NUMBERS nothing too big either where your gonna throw reliability out the window aswell.. also the driving style aswell cuz you dont want big numbers with a rediculous jump somewhere in the power band because in order to enjoy that band your gonna have to scream the daylights out of it in the streets just to get it there point in case

starting from the 2070 rpm mark to just past the 3780 rpm mark you figure that boost increase is really not the violent till about 3870 where you reach that 1bar of pressure at the point that sudden rich dip all the way to 11.8:1 which is good cuz of the sudden increase in boost so its always good to be a little richer because your getting full load and increase in your fuel and increase in timing advance aswell so it will all work in good harmony.
Now as you start climbing in the rpm band if you notice at about the 4350 rpm mark the afr's are just above the 12:1 afr mark and notice how the boost drop just a little bit your still in the safe zone no where near being to extreme a lean where engine damage would occur you could pull back on the fuel just a tad where you would take advantage of the boost and increase some power aswell because theres a "lean best torque" and "lean best power" and 'rich best power" and "rich best torque" that can be achieved depending on where in the spectrum your at.. i usually try to go for rich best torque cuz thats where you get the most enjoyable "pull" mixed in correctly you get good power and very good torque after all torque is what moves the car foward hp numbers just let you brag to your buddies hence a big v8 with lots of cubes and a 4e-5e is really not that big on cubes soo that torque must be achieved through the motor and turbo in harmony.
moving on if you notice now at the 4920 rpm mark the boost is still somewhat steady correct?? but now as soon as the rpms keep on climbing your afr's go peg rich notice the boost pressure!! keep in mind your afr's do not dictate your turbo performance the turbo doesnt know if it has to speed up or slow down because its pumping in too much airflow.. what causing that is the way the motor is injesting that air with the fuel and timing then the combustion happens and POP that comes out of your cylinder head to your turbine now too much fuel will not make more power if in excess it'll drop in power because if not timed correctly its just to much fuel to be ignited and used correctly in those milliseconds the combustion process is happening so there for you have that drop in boost aswell because its just too much fuel to ignite properly in such short time frame..if you would of aimed at keeping it a the 12.1-12.3:1 afr range you would of noticed a flat boost line from 4920 till that 6k rpm marker remember your turbo by this time is in full boost so there for you really would lean out anymore reguardless if your still going higher in the rpm band thats where your cams would somewhat be dictating your rpm power band because the turbo can only do soo much if your cams arent made to keep on making power past a certain rpm point anyways. past that 6k rpm marker till redline you'll notice your afr's are in the 12.0-12.2:1 afr which is still no where near a lean condition that you would damage anything on your motor unless your timing is increase way too much that you could cause and increase in cylinder pressures and extreme heat and resulting in pre ignition or detonation.... my personal opinion for your motor reguardless if its standard or forged what your looking at is the end product in your combustion events not how well your turbo is boosting or nothing along those lines..
I would leave it alone just past the 3780 rpm range cuz thats where your turbo ramped up into its sweet spot of full boost as the boost levels out id leave around the 12.1-12.4:1 range reguardless of rpm reason being your motor is working good your timing is in the whole advance or retard motion depending on how your controlling whether its stock ecu or aftermarket the stock ecu knows it has too boost retart based on map and the knock sensor is there too safe guard aswell.. try those afr''s and youll get good power that you'll enjoy driving each and everytime and you'll be safe in the afr's aswell.. theres tuners that take them all the way into the low 13:1 range they'll make more power but your risking alot.. soo 12.1-12.7:1 your safe..good luck...

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Was it checked on the road after being on the dyno by the mapper?


Mike Jones
Tuning Developments Ltd
like i said in the other post
i'd prefer to see it richer just to be on the safe if you are using pump gas...regardless of standard or forged engine

chris tunes a lot of engines over that side of the can take what he says into consideration

the ultimate decision rests with you and your tuner at the end of the day

PS - if you were using quality race gas, then that's another story


I'd share the concern that it looks a tad lean high up, that's where things can get a little risky. Not saying she's dangerous, seen cars operate with similar readings, just a personal observation. Tuners will always question the actions of other tuners lol.

Would have thought a final road check would have been in order as real road versus simulated road can affect matters. Once again, that depends on what sort of discussion you had with the tuner mate.



Super Moderator
for soem reason he could get the fueling bang on as not enough ajustment with the emanage??

Personally I'd be a little more concerned with this ^^ rather than the 12.2:1 AFR at full boost.

Maybe a new fuel pump or an increase in base fuel pressure would provide a little more of a safety net.


Member +
cheers for all the imput guys,
no it wasnt checked on the road, im going to get some 1 else to check out the map next month to give me a second oppion on the actual map and ajust it were needed, would you guys say its safe to boost it, its my 2nd car and only gets used one or twice a week if its dry and nice to get to work but is boosted and make the most of the car.

would ajusting the fuel preassure higher a tiny bit on the regulator make sort it out? i know its not going to be 100% spot on and will richen it up through out the revs but will be better at end of rev range


Adjusting the fuel pressure would do what you want, but dont touch it until you share your concerns with the mapper, you could tell him you want it runner a bit richer, as other Starlet owners you know of have had engine failures with those AFRs. That takes the "you did it wrong" bit out of it and puts it down to experience of that engine from others.

He should be prepared to listen to that, even if he feels its safe enough you are asking him for little more margin.


Yeah, just raise your concerns with the mapper asap. Don't be tempted to adjust anything yourself unless you know exactly what effect it will have and are prepared to stand over the consequences.


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Cheers formally the advice, just spoke Andy at passports and it going back in Monday and he's gonna richer it up to 11.5 from 6k onwards for me