matthewswinimer Posted September 25, 2012 Share Posted September 25, 2012 hi there my current setup is bpu running around 17.5 psi, with a meth kit mixed at 25% with smallest nozzle installed that the kit comes with(aem)only can get 91 octane here ,ebc,fmic, anyways when iam giveing it, my a/f ratio hits 12.0 for a sec then drops down around 10.5 to 11, iam only running the stock jpsec 440 injectors with a walbro 255. can i up to the mix of my meth or go to the med sized nozzle to richin it up a little or are these numbers ok. any input is great, new to the supra community. thanks. Quote Link to comment Share on other sites More sharing options...
SteveR Posted September 25, 2012 Share Posted September 25, 2012 Those numbers are ok, perhaps a little rich, for WOT. Don't make it any richer! All petrol engines all have the same ideal AFR: 14.7 under constant conditions (i.e. the car travelling at a constant speed at constant throttle position). Most tuners run things a bit richer at WOT just to be safe, as the worse that can happen is a lot better than if it started to run lean. A stock Supra runs quite rich under all conditions for some reason. Quote Link to comment Share on other sites More sharing options...
listy Posted September 25, 2012 Share Posted September 25, 2012 Are you still on stock turbos? If so, 17.5 psi is a tad too much, and your turbos might not last too long on hard pulls. 16psi or 1.2 bar is the recognised limit of the stock turbos. Quote Link to comment Share on other sites More sharing options...
matthewswinimer Posted September 25, 2012 Author Share Posted September 25, 2012 Are you still on stock turbos? If so, 17.5 psi is a tad too much, and your turbos might not last too long on hard pulls. 16psi or 1.2 bar is the recognised limit of the stock turbos. yes on stock jspec turbos,ive heard ALOT different numbers bounced around for stock turbo limits, i have two settings on my aem truboost,18 psi and 15 psi, i run 15 psi on the street and only use the 18psi when my buddy with his turbo charged mustang gets a big chest. Quote Link to comment Share on other sites More sharing options...
matthewswinimer Posted September 25, 2012 Author Share Posted September 25, 2012 Those numbers are ok, perhaps a little rich, for WOT. Don't make it any richer! All petrol engines all have the same ideal AFR: 14.7 under constant conditions (i.e. the car travelling at a constant speed at constant throttle position). Most tuners run things a bit richer at WOT just to be safe, as the worse that can happen is a lot better than if it started to run lean. A stock Supra runs quite rich under all conditions for some reason. ok even tho 12 for a sec kinda scares me..... Quote Link to comment Share on other sites More sharing options...
matthewswinimer Posted September 25, 2012 Author Share Posted September 25, 2012 also do you guys think it would be more benifical to up the mix to 50/50 or leave at 25% Quote Link to comment Share on other sites More sharing options...
SteveR Posted September 26, 2012 Share Posted September 26, 2012 ok even tho 12 for a sec kinda scares me..... Why? Quote Link to comment Share on other sites More sharing options...
matthewswinimer Posted September 26, 2012 Author Share Posted September 26, 2012 Why? isnt 12 getting kinda lean. Quote Link to comment Share on other sites More sharing options...
Noz Posted September 26, 2012 Share Posted September 26, 2012 I thought 11-12 was where you want to be hitting Quote Link to comment Share on other sites More sharing options...
SteveR Posted September 26, 2012 Share Posted September 26, 2012 (edited) isnt 12 getting kinda lean. Rich, not lean. It's an air:fuel ratio. So imagine it as 12 lots of air, per 1 lot of fuel. So fuel makes up 1/13 of the total mix. 18 air, to 1 fuel (starting to become dangerously lean) = 1/19 of the total mix. See? As I said, rich is safe®, lean is bad. 14.7 is perfect. less than 14.7 = rich, more than 14.7 = lean. Don't worry about being ~1ish eiethr side under normal conditions, and you always want to run a safety margin (run rich) when full or close to full throttle i.e. the numbers should down to around 11.x~12.x is the usual guidance. Edited September 26, 2012 by SteveR (see edit history) Quote Link to comment Share on other sites More sharing options...
Noz Posted September 26, 2012 Share Posted September 26, 2012 Mine hit's 10.0 from 3.5-5k Quote Link to comment Share on other sites More sharing options...
JMB Posted September 26, 2012 Share Posted September 26, 2012 Mine hit's 10.0 from 3.5-5k My rx8 used to run always at 10:0 at full boost : that's cool for flames Quote Link to comment Share on other sites More sharing options...
Hellstrom Posted September 26, 2012 Share Posted September 26, 2012 14.7 is for maximized combustion nothing to do with it beeing perfect. 14.7 is the best combustion in terms of emissions not power. Also as he is using 91 octane its fair bit more likely to knock erlier then using 95-99 octane. running less then 12 would be your aim imo. probebly around 11.5 as max value during WOT/maxboost. using exhaust temprature would be good to make sure it does not go out of hand. Quote Link to comment Share on other sites More sharing options...
SteveR Posted September 26, 2012 Share Posted September 26, 2012 14.7 is for maximized combustion nothing to do with it beeing perfect. 14.7 is the best combustion in terms of emissions not power. Also as he is using 91 octane its fair bit more likely to knock erlier then using 95-99 octane. running less then 12 would be your aim imo. probebly around 11.5 as max value during WOT/maxboost. using exhaust temprature would be good to make sure it does not go out of hand. Fair play: Quote Link to comment Share on other sites More sharing options...
Hellstrom Posted September 26, 2012 Share Posted September 26, 2012 maximum power is 12:6 AFR however it is still pretty lean so most people tend to go richer (loosing power) to keep exhaust temps down to a more controllable level. Quote Link to comment Share on other sites More sharing options...
matthewswinimer Posted September 26, 2012 Author Share Posted September 26, 2012 very helpful guys thanks for the input. one more question tho where i only have 91 octane would it be benifical for me to up my meth mix to 50/50 to help with timing and such or should i leave it at 25%, iam running the smallest nozzle the aem kit comes with Quote Link to comment Share on other sites More sharing options...
matthewswinimer Posted September 28, 2012 Author Share Posted September 28, 2012 bump for info Quote Link to comment Share on other sites More sharing options...
Noz Posted September 28, 2012 Share Posted September 28, 2012 50/50 vs 25/75, 25% water or meth? Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted September 28, 2012 Share Posted September 28, 2012 I think he means water to meth, theres no advantage in going from 25% to 50% meth, you would need to tune on a dyno in order to see if you could safely advance timing, and as mentioned before, unless you have some reliable form of fail safes in place its just not worth the risk for a few BHP. Quote Link to comment Share on other sites More sharing options...
matthewswinimer Posted September 28, 2012 Author Share Posted September 28, 2012 I think he means water to meth, theres no advantage in going from 25% to 50% meth, you would need to tune on a dyno in order to see if you could safely advance timing, and as mentioned before, unless you have some reliable form of fail safes in place its just not worth the risk for a few BHP. 25% meth is what i mean, as far as failsafes i have the boost safe wire from the aem meth kit hooked to the scramble boost wire of my aem tru boost so it will knock the boost back to stock if somthing happens Quote Link to comment Share on other sites More sharing options...
Samurai 20V Posted September 29, 2012 Share Posted September 29, 2012 Mine goes down to 8.9 on WOT at 1.2bar.. Thats in Japan on 100octane.. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted September 29, 2012 Share Posted September 29, 2012 very helpful guys thanks for the input. one more question tho where i only have 91 octane would it be benifical for me to up my meth mix to 50/50 to help with timing and such or should i leave it at 25%, iam running the smallest nozzle the aem kit comes with 25% meth is what i mean, as far as failsafes i have the boost safe wire from the aem meth kit hooked to the scramble boost wire of my aem tru boost so it will knock the boost back to stock if somthing happens It appeared in this post that you are asking if there is any point going from a 25% meth/water mix to 50-50% mix:blink: And the impression was that you where asking if this would help with timing, presumably advance? so my reply was it basically not worth the risk without fail safes for the few BHP gained, Great you have a boost cut should you run out of water, but what happens if you get det! do you have any form of knock meter? and will it then retard the ignition if the engine sees det? this is why i said its not worth the risk for a few BHP. However going to 50% meth will not harm anything, and may give you a bit of extra insurance, but i found that 50% meth wouldn't let me add any more than 2deg advance when i mapped my singe turbo Supra. Quote Link to comment Share on other sites More sharing options...
matthewswinimer Posted September 29, 2012 Author Share Posted September 29, 2012 It appeared in this post that you are asking if there is any point going from a 25% meth/water mix to 50-50% mix:blink: And the impression was that you where asking if this would help with timing, presumably advance? so my reply was it basically not worth the risk without fail safes for the few BHP gained, Great you have a boost cut should you run out of water, but what happens if you get det! do you have any form of knock meter? and will it then retard the ignition if the engine sees det? this is why i said its not worth the risk for a few BHP. However going to 50% meth will not harm anything, and may give you a bit of extra insurance, but i found that 50% meth wouldn't let me add any more than 2deg advance when i mapped my singe turbo Supra. ok thats all i wanted to know. in conclusion i will just step up to the med sized jet and leave the ratio at 25% meth. thanks everyone for the replies Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.