AFR numbers

[Faheemo]

I've got a logging device with a knock sensor that makes it easier , so I was looking for a quick
Rule of thumb that says you can run xx amount of timing b4 boost kicks in and then take it from there.

[GazzaG60]

no hard and fast rule. lot depends on compression ratio etc.

best way is a set of det cans to listen for knock. one way is to advance slightly. you will feel or should feel the changes as it gets too much. power increase stops as does the cooling effect of the advance.

[Faheemo]

Hey guys i'm rather new to tuning, but my figures are close to what been mentioned above - i'm Running my car on 102 Octane with 2 bars of boost, 22deg of timing and AFR @ 11.8 - 12.0.
The car runs very well once she is in boost but i would like to know what would be optimal timing to run before the boost comes on , to reduce lag ?

[Simons]

[QUOTE=Rocco;460615]it´s very nice to learn day a day few to few with all of you
QUOTE]

I think the same as you

[Rocco]

BIG many thanks for all these coments


it´s very nice to learn day a day few to few with all of you

-Tomas-

[EspenW]

Good point about top speed runs and drag/normal driving as well. Huge difference between pushing a car for minutes at WOT on the autobahn and occasional 2.7 second bursts of WOT from 60 to 90mph.

[EspenW]

On gasoline, aim for around 11.5 at mid to high rpms (where the exhaust gas temp starts to skyrocket).
On E85, we often go leaner (0.85-0.88) as stoich is 9.6 (in petrol terms) and the cooling properties of ethanol are much better.

On my K-Jet Lambda Golf (USA spec), there was no full throttle switch (unlike the GTI model), so the car was running at stoich (14.7 / lambda 1) even at full throttle.

[AUDIS2avant]

I´m running 12,2 on WOT and 98ron in my cossie, with app 650bhp and it´s just fine, egt in collector is arr 950-970` and 21deg advance.
Would say no higher then 12,2-12,4 on WOT for drag, and 11,5 for topspeed.
As espen says, with the right fuel, you can go higher afr cause of the better coling features in the fuel but not on normal gasoline

[GazzaG60]

its dangerous for all normal gas FI engines that. its on the lean side. more NA numbers id have said.

over 12.5 and its getting lean.

a general rule of thumb is 14-15:1 on cruise and 11-12.5 for boost. i tend to aim for 11.8 or so.

its worth noting the accuracy of wideband sensors is not so good at the cruise levels as a narrow band. wideband is better at the extremities of the ranges more so the lean and the rich.

[Rocco]

it is dangerous for our engines under full acceleration and foot down the lambda numbers like 0.90/0.95 , that´s the same as 13´2/14.0 ..... ????????????

one up for this thread

i would love to know the question as i´ve marked

someone with engine tune knowledge can help??

[Rocco]

it is dangerous for our engines under full acceleration and foot down the lambda numbers like 0.90/0.95 , that´s the same as 13´2/14.0 ..... ????????????

[A80Avant]

only needed on wideband lamdas. It has to do with what the probe can measure as 14.7 mixture so that it can then show all the rest of the values properly. All standalone systems have a routine to make the lamda calibrated. VEMS has its own.

[T2Andy]

What and how is lambda calibration ,is it important

[EspenW]

Low 12's will probably be OK, even though mid 11's is usually the target on boost.
I run high 12's, sometimes into low 13's, but that is on the proper fuel for a turbo car.

[A80Avant]

you are absolutelly right Gary.
in current setup on motronic i had 21.50deg of advance dialed in on all high rpm/load values.That was the lowest timing i had there, although on lowering the IATs(colder weather, methanol injection etc) i could get as much as +4deg advance on the map.However, when i plugged the wideband to check the fueling, it was going as low as 0.70 on high gears,without ever stuttering from being too rich!! This is amazing cause once i started using vems, it would always do that when mixture gets below 0.72 for more than seconds!!

however on vems, im on 17.50deg on 2bar and 20deg on 1.8bar which as you know are the max they can go as there is no IAT advance feature. These are for safety reasons and with those values and mixtures of no less than 0.73 (mostly 0.75) on high rpms i get slightly better EGTs or about the same as the motronic. feelingwise, i would say that the car is about the same,but without doing runs under the same conditions i can never know.dyno session might give me an answer to that.
my compression is 9:1 roughly but i may decrease it in the future.