is it true that if you run the lexus maf without the 550s that it will cause a lean condition or will the o2 sensor pickup on it and adjust accordingly
Lexus maf question
- Thread starter cruzinbill
- Start date
no, you will run lean. with the lex afm your motor has no idea how much air is getting into your engine. the only way you can tune with the lex is if you start doing some thinking for your ecu, you know that there is more air therefore you have to add more fuel for the car(550's and walbrow).
Caution: This is my opinion.
IMO, you can run the lex afm WITHOUT the 550's. A rule of thumb I have heard about fuel injectors (with Supras anyway) is that 440's will support about 440hp, 550's will support about 550, etc. etc. etc. I would say switch to the Lex afm to avoid fuel cut and get a Walbro and AFPR to even out the AFR. JBL made 430hp on stock injectors with that set-up.
IMO, you can run the lex afm WITHOUT the 550's. A rule of thumb I have heard about fuel injectors (with Supras anyway) is that 440's will support about 440hp, 550's will support about 550, etc. etc. etc. I would say switch to the Lex afm to avoid fuel cut and get a Walbro and AFPR to even out the AFR. JBL made 430hp on stock injectors with that set-up.
I have both a LEX/AFM and 440's and no AFPR. I run a wide band and it is spot on everywhere up to 16.5 psi. After 16.5 I needed a FCD and fuel was still spot on until 18 psi on pump gas. After that I would see detonation so I needed H2O/Meth and its been a tiny bit lean (hi 12's low 13's) in the middle 3.8K to 4.6K but only at WOT. I still dont have 550's and this car is wicked fast.
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short answer: yes
long answer: it will lean you the hell out. my bro recently tested this theory on a dyno and i was interesting to say the least. he went from below 10:1 with the stock afm (high point was around 12:1 when boost started) with the lex he STARTED at around 16:1 (higher actually) and the ecu started compensating down to 12:1 near redline but he was still way on the lean side the whole time.
just a ps incase someone decides to chime in. this was done on a dyno not on the street. the motor never detonated and for some reason never messed with timing at all. i think he got lucky with the weather (cooler than normal)
pm me if you want to see the dyno sheets.
long answer: it will lean you the hell out. my bro recently tested this theory on a dyno and i was interesting to say the least. he went from below 10:1 with the stock afm (high point was around 12:1 when boost started) with the lex he STARTED at around 16:1 (higher actually) and the ecu started compensating down to 12:1 near redline but he was still way on the lean side the whole time.
just a ps incase someone decides to chime in. this was done on a dyno not on the street. the motor never detonated and for some reason never messed with timing at all. i think he got lucky with the weather (cooler than normal)
pm me if you want to see the dyno sheets.
^^^^ Me?!?!? Yes
Im not sure if this matters either but I have 4 inch plumbing post AFM/pre turbo, No ERG anything, 3 inch mandrel bent IC plumbing to and from IC and full 3 inch mandrel bent no cat Stainless exhaust, even the muffler is wide open.
Also I have a 2mm MHG and run about 11deg just to be safe.
Im not sure if this matters either but I have 4 inch plumbing post AFM/pre turbo, No ERG anything, 3 inch mandrel bent IC plumbing to and from IC and full 3 inch mandrel bent no cat Stainless exhaust, even the muffler is wide open.
Also I have a 2mm MHG and run about 11deg just to be safe.
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Also take into consideration that adjusting the bypass screw makes quite a difference. Take a LexAFM and put a screw in that's long enough, and you end up with the same result as a stock AFM. I run Lex/440's, and a base fuel pressure (vac removed) of 50psi to keep Vf happy. I'm sure I could lower the fuel pressure if I closed the Lex bypass screw (which also lowers FC threshold), but it's running so well as it is, that I'll leave it.
diy guy said:
Adding fuel from increased fuel pressure to suit closed loop requirements (non-WOT conditions). My S-AFC is pulling from -13% to -18% to get WOT tune down to 11.5:1 AFR across the board.
hmm, i wouldnt have thought a little bump in base pressure and the screw bypass would make such a big difference. the afr difference between the stock afm w/ screw out vs lex afm on the dyno posted is huge. do you have a dyno of yours w/ afr readings?
btw if you have a safc couldnt you just trim more fuel to trick the ecu into thinking theres less airflow instead of getting a bigger afm?
btw if you have a safc couldnt you just trim more fuel to trick the ecu into thinking theres less airflow instead of getting a bigger afm?
diy guy said:
To view wideband logs (small free program, worth the DL):
http://www.zeitronix.com/images/ZDL_V_2.0.3_InstallationFiles.zip
Best dyno:
Was a dyno-day event, didn't get enough runs to fine-tune the AFR's beyond what you see.
http://members.provalue.net/moon/dyno/dynoday11_19_05.jpg
http://members.provalue.net/moon/dyno/dynoday2.zto
Best tune:
..and the .ZTO log to go with it
http://members.provalue.net/moon/dyno/moorman_silv_dyno.jpg
http://members.provalue.net/moon/dyno/silv_dyno.zto
diy guy said:
Really, I sure it's possible, (if I'm understanding this part of your post correctly) but I wouldn't. Since all the Lex AFM does is tell the ECU there's less air than the engine is really receiving, the AFC can do the same by modifying the signal -BUT- I'd rather not attempt to modify the closed-loop range since it's too easy to end up battling the ECU. Lex afm makes it much much easier. The only reason for the Lex is to push fuel-cut out farther. Bumping the fuel pressure or using bigger injectors is to even the scales while keeping FC out of reach. I happened to already have an AFPR, so I used stock injectors. If I'd had to *purchase* the means to increase fuel, I'd have chosen 550 injectors over AFPR since they allow more headroom for future mods.
MKIIINA said:
The metered area inside my Lex measures the same as my stock afm, but the bypass area is both wider and taller. A custom screw would be required to make the Lex function the same as stock, but it can be done.....though I don't know why anyone would.
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Heres my bros dyno. red line is the stock afm, blue line is no change other than swapping out the lex afm. nothing else. mods are intake, exhaust (catback only stock cat), lower hardpipe, blitz DD and this oddball turbo
(its a t3 hybrid with a garrett center section) AND THATS IT! so look at the graph and tell me you want that blue af....
MKIIINA said:
Heres my bros dyno. red line is the stock afm, blue line is no change other than swapping out the lex afm. nothing else. mods are intake, exhaust (catback only stock cat), lower hardpipe, blitz DD and this oddball turbo
Yeah...don't do that, it's not a good thing. That's a lot of air getting in that isn't accounted for. Don't do it unless you have the means to compensate fuel for that unmetered air.
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moorman, how sure are you that you have the correct afm? because according to my calculations, using 40psi as base pressure, youre getting about 12% more fuel by bumping to 50psi. the lex maf is supposed to be 25% bigger and you still trimmed fuel another 18%. I know the stock ecu runs pig rich but 30% plus is ridiculous. btw, are you sure the second is the best tune? 13:1afr at peak torque sounds on the lean side
about the safc, you dont have to change anything in closed loop. only make adjustments in the hi throttle map where it matters. you're not going make full boost, and therefore not hit fuel cut at part throttle anyways. as a matter of fact this would be a better way of doing it since nothing is changed in low throttle conditions aka closed loop operation.
this sounds too easy, anyone want to chime in and explain why this cant be done or isnt recommended.
about the safc, you dont have to change anything in closed loop. only make adjustments in the hi throttle map where it matters. you're not going make full boost, and therefore not hit fuel cut at part throttle anyways. as a matter of fact this would be a better way of doing it since nothing is changed in low throttle conditions aka closed loop operation.
this sounds too easy, anyone want to chime in and explain why this cant be done or isnt recommended.