For all those running FAST XFI or any other FAST configuration. Can you share your timing strategy for cruise. Say up through 75 KPA and 4k rpm, I have been slowly dialing the car in and I see no more than 30 degrees and I am wondering if there is more to be had here?
FAST XFI Timing Strategy under Cruise
- Thread starter Mad_Trbo
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I run as much as 50 degrees in a few parts of my map, most of my cruising area is 45 degrees or above.
Remember that in the "old days" with a distributor, you had initial advance (perhaps 10 degees) plus mechanical advance (maybe another 24 degrees) plus vacuum advance (perhaps about 16 degrees) when cruising on the highway.
(If you have very high compression or some other changes, you'll have to adjust accordingly, but trial and error will help you find the best tune)
-Bob Cunningham
Remember that in the "old days" with a distributor, you had initial advance (perhaps 10 degees) plus mechanical advance (maybe another 24 degrees) plus vacuum advance (perhaps about 16 degrees) when cruising on the highway.
(If you have very high compression or some other changes, you'll have to adjust accordingly, but trial and error will help you find the best tune)
-Bob Cunningham
Unfortunatley I have never worked on a system with a distributor. But I do get your point and thanks for your feedback.
How did you come to your final resting point, did you do your tuning on a dyno? Or was most of highway and adjust while you drive?
How did you come to your final resting point, did you do your tuning on a dyno? Or was most of highway and adjust while you drive?
For me, it was just trial and error while driving. If I went with too much advance, it felt like the engine was skipping, so I would just retard the timing back to where I felt the engine was running evenly. But keep an eye on your KR as well. For me, it wound up that gas mileage was very good at those numbers, so I stuck with them.
I'm not an expert, but as I understand too much advance could give you two possibilities- first being that the mixture is not ignited (harmless) but the other is that you ignite so early that you hammer the piston like detonation. Different engines react differently, I'm sure.
-Bob C.
I'm not an expert, but as I understand too much advance could give you two possibilities- first being that the mixture is not ignited (harmless) but the other is that you ignite so early that you hammer the piston like detonation. Different engines react differently, I'm sure.
-Bob C.
i have the older B2B system i have my timing anywhere from 35*-40* at cruise but my target A/F is anywhere from 15.5-16.
thing that i have noticed is that you can watch your kpa @ a given speed @ a given air fuel to tell how hard the engine is working. keep changing the timing @ to see if the kpa goes up or down. lower kpa means less throttle opening. KPA changes faster that the TPS percent.
i can cruise @75 mph @ 15.7 air fuel with 39* @ 68-70 kpa
thing that i have noticed is that you can watch your kpa @ a given speed @ a given air fuel to tell how hard the engine is working. keep changing the timing @ to see if the kpa goes up or down. lower kpa means less throttle opening. KPA changes faster that the TPS percent.
i can cruise @75 mph @ 15.7 air fuel with 39* @ 68-70 kpa
