What do you think about of tune to 12.0 A/F ratio?

[Adrian]

I've found a intressting thread on the sr20-forum.

http://www.sr20-forum.com/tuning/16056- ... lcome.html

They say you should tune to a AFR of 12.0!

What do you think about and what are your preffered target A/F ratios?

[RomChip200]

This is typically my real-life AFRs on E85:
(not WOT but 15.4psi reached below (TPpeak=80 with 740cc injectors on Z32, at WOT, my AFR goes quickly to 11.5-12, to go back to 12.xx)

Code: Select all

Time	RPM	Temp	Speed	TPS	Inj time (LHS)	Inj time (RHS)	Timing	TP	Lambda LHS	Lambda RHS	AFR	AFR RHS	TP (MSB)	Injector duty
05:38.0	3725	80	86	2.3	8.61	8.61	24	11751 [45]	1.06	1.07	15.72	15.74 45	26
05:38.1	3775	80	86	2.44	10	10	23	13481 [52]	1	1	14.77	14.77	52	31
05:38.2	3812	80	86	2.44	10.74	10.74	22	14429 [56]	0.82	0.82	12.08	12.17	56	34
05:38.3	3837	80	88	2.3	11.25	11.25	22	14997 [58]	0.8	0.82	11.86	12.08	58	35
05:38.4	3887	80	88	2.12	11.2	11.2	21	15035 [58]	0.78	0.8	11.52	11.86	58	36
05:38.6	3937	80	88	1.96	10.8	10.8	23	14516 [56]	0.75	0.79	11.12	11.75	56	35
05:38.7	3975	80	88	1.9	10.54	10.54	23	14205 [55]	0.78	0.8	11.58	11.86	55	34
05:38.8	4025	80	88	1.9	10.44	10.44	24	14126 [55]	0.81	0.84	11.98	12.37	55	35
05:38.9	4050	80	88	1.92	10.57	10.57	23	14329 [55]	0.82	0.85	12.17	12.64	55	35
05:39.0	4112	80	88	2.08	11.72	11.72	23	15273 [59]	0.84	0.87	12.4	12.83	59	40
05:39.1	4187	80	96	2.34	13.65	13.65	21	17465 [68]	0.83	0.86	12.23	12.78	68	47
05:39.2	4250	80	96	2.56	14.55	14.55	21	19334 [75]	0.79	0.86	11.74	12.68	75	51
05:39.3	4312	80	96	2.78	15.44	15.44	21	20529 [80]	0.79	0.83	11.64	12.34	80	55
05:39.4	4375	80	96	2.82	15.08	15.08	21	20010 [78]	0.79	0.82	11.65	12.2	78	54
05:39.5	4425	80	96	2.8	14.02	14.02	21	18595 [72]	0.81	0.84	11.95	12.48	72	51
05:39.6	4512	80	96	2.82	14.22	14.22	21	18881 [73]	0.84	0.89	12.36	13.14	73	53
05:39.7	4600	80	106	2.84	14.04	14.04	21	18629 [72]	0.86	0.87	12.74	12.93	72	53
05:39.8	4625	80	106	2.9	14.1	14.1	21	18706 [73]	0.85	0.87	12.55	12.86	73	54
05:39.9	4637	80	106	2.96	14.01	14.01	21	18562 [72]	0.83	0.88	12.34	12.96	72	54
05:40.1	4775	80	106	2.96	13.74	13.74	21	18297 [71]	0.83	0.88	12.33	12.98	71	54
05:40.1	4837	80	106	2.94	13.77	13.77	21	18332 [71]	0.83	0.88	12.33	12.96	71	55
05:40.3	4887	80	106	2.94	13.76	13.76	21	18327 [71]	0.83	0.87	12.06	12.93	71	56
05:40.4	4950	80	106	2.94	13.78	13.78	21	18354 [71]	0.82	0.87	12.06	12.93	71	56
05:40.5	4937	80	114	2.94	13.85	13.85	21	18344 [71]	0.83	0.87	12.33	12.86	71	56
05:40.6	5075	80	114	2.94	13.84	13.84	22	18341 [71]	0.83	0.86	12.3	12.78	71	58
05:40.7	5050	80	114	2.94	13.74	13.74	22	18191 [71]	0.82	0.86	12.17	12.74	71	57
05:40.8	5137	80	114	2.96	13.76	13.76	22	18212 [71]	0.82	0.86	12.14	12.68	71	58
05:40.9	5212	80	114	2.98	13.7	13.7	22	18141 [70]	0.83	0.87	12.33	12.83	70	59
05:41.0	5262	80	114	3.06	13.77	13.89	22	18212 [71]	0.84	0.86	12.45	12.71	71	60
05:41.1	5262	80	114	3.12	13.7	13.7	22	18131 [70]	0.84	0.87	12.45	12.9	70	60
05:41.2	5337	80	124	3.16	13.74	13.74	22	18187 [71]	0.85	0.87	12.52	12.9	71	61
05:41.3	5437	80	124	3.14	13.68	13.68	22	18107 [70]	0.83	0.87	12.3	12.84	70	61
05:41.4	5450	80	124	2.68	13.58	13.58	23	17977 [70]	0.84	0.87	12.46	12.83	70	61
05:41.5	5387	80	124	0.46	4.02	4.02	20	5007 [19]	0.79	0.8	11.71	11.9	19	18
05:41.6	5337	80	124	0.46	1.11	1.87	20	1653 [6]	0.77	0.67	11.4	9.96	6	4

[Bernardd]

I rely heavily on methanol injection for detonation control/octane and found that I lost a few horsepower at a high 10 afr and didn't gain anything by leaning out the afr's beyond 11.8. I tune for 11.2. Timing is critical and holds the key to power more so than afr's. YMMV

[RomChip200]

Agree about timing.
But I think fuel economy too.

[bachig24u]

I think that one man's experience is never another's.

Try not to be blinded by science as it's far from reality at the best of times. (take global warming for instance)

I have personally proven that leaner mixtures make more power but to what extent?
well, in less than 3 seconds a perfectly healthy engine can become a $30K boat anchor. The owner neglected to tell me that the previous days blended fuel had not been blended the same for the current day. If the engine was on the safer side, would not have been a problem but the AFR's under load went up by just 2.1%

If you plan to push the boundaries (which we need to do atleast once) ensure to monitor/record every conceivable parameter.
When/if you get away with it, pat yourself on the back, spend the next few days understanding what happened in the engine to achieve the results. then, go out and prove your theory.
make 1 small change at a time and test it atleast 3 times in the same session to get best mean result.

good luck!!

Romchip E85's Stoich is 9.7:1 .. how does your AFR results come out so lean?

[RomChip200]

Romchip E85's Stoich is 9.7:1 .. how does your AFR results come out so lean?

AFR are a matter of display of the widebands gauges.
I tuned E85 since the beginning having my widebands displaying the AFR values related to unleaded fuel and keeping the same references in mind.
Lambdas are consistent behind.



This is just not to modify the parameters of my gauges when sometimes, I put some unleaded fuel in the tank b/c E85 is not available.
My widebands gauges are fixed installed in my car, so I always have an eye on them.

[bachig24u]

a viable workaround.