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Discussion Starter #1
ok. I have 3 BPU supras that testified that they run lean using 94 ECU at between 13-14:1 A/F ratio.

I myself is also running extremely lean at 14:1.

I know that everybody says at BPU our ECU starts dumping fuel like crazy and make our car run rich...can I get some feedback from BPUs that has a wideband O2 sensor?

thanx
 

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Well i went BPU few weeks ago as well and made about 411 RWHP with 50/50 of 100/93 octane and my A/F ratio gradually peaked to 13.0:1 at 5500 RPM and came down to 11.8:1 at red line.After that run i richened my old style AFC by 4% at 5500 RPM even though Steve Jarvis who helped me installed the mods,said that 12.5:1-13.0:1 is safe. BTW this conclussion came from his own experience of running A/F ratios of 13.5:1-13.9:1 on his older black TT car and he also put close to 30,000+ BPU miles along with 5-6 trips to road courses.Steve I hope i'm not quoting you wrong,and also please feel free to comment;)
Regards. Yasir
 

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yasir said:
...12.5:1-13.0:1 is safe. BTW this conclussion came from his own experience of running A/F ratios of 13.5:1-13.9:...
AAAAAHHHHHHH!

We have tough motors, but lets not test our luck!

My '97 could be leaned out by about 2% to 3%, and still have plenty of extra fuel for saftey (that a/f is probably still too rich). This info was not gotten by a wideband, but rather by watching timing advance.

FYI, the absolute highest EGTs (and worst detonation) is had at 14.7:1. Your only 1 a/f point away from that at 13.5-13.9. Not even NA cars run that lean.

I find it hard to believe that any turbo car could last even a few pulls at 14:1, but I really don't have any experience with blowing motors.
 
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Discussion Starter #4
if you're 14:1, why are you still driving around? wouldn't you want to figure out why you are running that lean? it only takes a fraction of a second to blow your motor at those ratios and it's always better to err on the side of rich.

I've been around lots of bpu supras and most bpu's without fuel control are rich as hell. Fuel issues are not difficult to figure out and if you're in cali, i'll bet the bulk of your problems is the gasoline octane. Easy solution, run higher octane or lower the boost! simple.
 
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Discussion Starter #5
Should i worry about running too lean if i live in CA and i use 91 octane all the time? BTW, i am straight BPU w/o fuel controller. My max boost is 1.3kg/cm2.
 

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Please don't run over 12.5:1. I ran 12.5:1 on my old Supra on the street and typically 12.0:1 on the roadcourse. I did run 12.5:1 on the roadcourse once (for one 20min. session) by mistake. I forgot to change my S-AFC settings. Yasir's car only ran 13.0:1 at around 5,500rpm and continually got richer from that point on. I didn't see a problem because I know the wide band O2 seemed to be giving some misleading numbers in the 5,500 rpm range. The operator actually ended up replacing the O2 after 2 more cars made runs that showed wrong a/f's. I would guess that Yasir is actually in the 12.5:1 or 12.0:1 range at 5,500. His car reacted very similar to my 95 and that is where it ran at those S-AFC settings.

Later, Steve
 
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Discussion Starter #7
NOVAsupra said:
if you're 14:1, why are you still driving around? wouldn't you want to figure out why you are running that lean? it only takes a fraction of a second to blow your motor at those ratios and it's always better to err on the side of rich.

I've been around lots of bpu supras and most bpu's without fuel control are rich as hell. Fuel issues are not difficult to figure out and if you're in cali, i'll bet the bulk of your problems is the gasoline octane. Easy solution, run higher octane or lower the boost! simple.
thanx for the warning...I've been working on this problem for over a month now....and my fuel system is FINE. I replaced/tested almost everything I can think of.
my A/F ratio droped to 10:1 at 4000rpm and clims steadily to 14:1 by 6000rpm-reline.....not fun.

how can A/F ratio be effected by octan rates?

anybody running over 13:1 is running lean IMO. when I was runing 13:1 boosting 18psi my EGT will go up to 740-760c at top of DP! insanely hot...all I want is lower my A/F to aronund 12:1.

BTW I have a HKS AFR and it doesnt help much, and yes, its hooked up right.

for those of you who run 13:1 A/F, ever notice your EGT shooting pass 700C on a high gear pull?
 

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I am beginning to think I am running out of fuel. I though my S-AFC wasn't working, but now I think I am just asking for more fuel than the my stock system will deliver. My S-AFC seemed to work fine at lower rpms (up to about 4,500rpm), but not at all when the boost comes up. I have replaced the S-AFC with a new one and it did the same thing. At about 16.5psi (around 460rwhp) I can maintain 650c (at the top of the downpipe) with my S-AFC set at 0. I can then richen the S-AFC up 50% and the car still runs about 650c by redline in 3rd gear. If I turn the boost up to 18.5psi (about 490rwhp) my EGT's will stay at about 650c until 6,000 rpm (about 475rwhp) and then steadily climb to 680c by redline. The most I have seen is 720c after a run through 4th and partially into 5th. My car isn't too lean, but I don't seem to be able to give it any more fuel. I wonder if the fuel pulsation dampener is more restrictive than we might think. I have seen several cars make 530+ rwhp with the stock pump and injectors, but only one had the fuel pulsation dampener (Brad Mayo). I already have the FPD bypass hose, I just need to installed it. I will let everyone know if this allows me to reduce my EGT's at 18.5psi. My point is the FPD may actually start running out of fuel at around 460rwhp. A BPU car with around 430rwhp could be make around this number on a cold day with a high volume of air going through the intercooler vs. a fan on the dyno. Plus the stock twins would be pushing higher EGT's because they are heating the air considerably more than my SP63. Just a thought.

Later, Steve
 
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Discussion Starter #9
Intersting thread... I also am BPU and I am wondering what is the most efficent way of controlling fuel on a BPU car...

AFC? Any others?
 

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Steve Jarvis said:
Please don't run over 12.5:1. I ran 12.5:1 on my old Supra on the street and typically 12.0:1 on the roadcourse. I did run 12.5:1 on the roadcourse once (for one 20min. session) by mistake. I forgot to change my S-AFC settings. Yasir's car only ran 13.0:1 at around 5,500rpm and continually got richer from that point on. I didn't see a problem because I know the wide band O2 seemed to be giving some misleading numbers in the 5,500 rpm range. The operator actually ended up replacing the O2 after 2 more cars made runs that showed wrong a/f's. I would guess that Yasir is actually in the 12.5:1 or 12.0:1 range at 5,500. His car reacted very similar to my 95 and that is where it ran at those S-AFC settings.

Later, Steve
My apoligies Steve for misunderstanding you and that's why i wanted you to comment and thanks for the clarification ;) BTW your car is looking great.
Yasir
 

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SpdRcr0 - have you given any thought to the AEM ECU? Full control of fuel, timing, and max boost in a PnP unit. Reading some of these threads on fuel control and the PTA it seems to be tuning to get things right has led me to decide the AEM is the way I'll go. Not cheap but when you add up all of the gadgets it will replace it becomes a little more attractive IMO. $350 for the FC alone....
 
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Discussion Starter #12
Fuel issues are not difficult to figure out and if you're in cali, i'll bet the bulk of your problems is the gasoline octane. Easy solution, run higher octane or lower the boost! simple. [/B]


BTW, I just rememberd when I was on the dyno running 60/40 mix of 100 octan my A/F was 13:1 no better than when I went back to 91 octan....although just recently it went up to 14:1.
 

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Steve,
Did you try changing both the High and Low throttle setting fuel maps on the SAFC?

I'm not sure how the SAFC senses throttle position but wondered if a problem with how it senses it might be why you can change the fuel at low boost but not at high boost.

To be honest, I have no experience with this yet but I'm getting an SAFC put in over the next week with a bunch of stuff (including VPC, Fuel FJO WB O2, SP57) and I picked it because I hope the High setting can be set so it only modifies the Open Loop behavior of the ECU.

From all I've read modifying the Low Throttle setting is useless other than an "across the board" fixed delta so the ECU comes out of reset with the right correction factor for the larger injectors and VPC. Modifying the low setting aka "closed loop" seems to just result in the ECU adjusting for what the SAFC is doing. I think that just results in the ECU backing out the Low throttle SAFC settings after it comes out of reset and starts learning based on the air fuel ratio it actually sees vs what it wants to see.

All theory for me right now but with the FJO wideband O2, Sp57, 750cc injectors, VPC & SAFC going in, I'm going to have to start my real world education.

BTW, recently started lurking here & this is my first post. Been lurking on the MKIV list since I got the car in May. '93 auto w 8,158 miles. BPU at 9600 with some advice off that list. (RMM DP, HKS EX, BCC, Superdragger). Blew #2 at 11,200 a couple of weeks ago in the first planned street race of my life on the 4th run. Cold night in the 30s and at 1.42 kg/cm2. Was sequential due to the auto and sure it was shaft twist. Bad luck and maybe an actuator problem??? Before you ask, lots of reasons I'm sure about the mileage.

Chris Johnson who does all the work on SW's Supras and did my BPU is doing the work. Starting with the SP57 while waiting for the new multi-disc PI Torque Converter and seeing whats up with the recent tranny options and also to make sure I can handle 500 rwhp before I go near 600 with the SP63 :)

Same philosophy I used by waiting a couple of months and 1500 miles before I went BPU. Sure I'll never go past an SP63 because I want the car for more than straight line drag/street racing. The winding roads are still my love. Just can't stay away from some of the adrenilin kick that rwhp brings:)

BTW, beautiful car!
 

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Steve Jarvis said:
Plus the stock twins would be pushing higher EGT's because they are heating the air considerably more than my SP63. Just a thought.

Later, Steve
The intake charge is almost completely cooled by a good FMIC, and the stock IC does almost as well during street bursts and drag racing (I used a multimeter thermocouple to test this).

The stock twins do produce a shitload more exhaust backpressure, because it takes so much more energy for them to move as much air as the SP63 (And because their a/r and manifold is restrictive). This raises EGTs, although it might not show up in the DP.

Why not read voltage of the stock O2 sensor? Its no wideband, but it will give you a good idea of whats going on. I'd look for no less than .92v with those kind of EGTs (narrowband O2v varies a lot with EGT). That should be about 11.5:1.

BTW, every car is different, some can run leaner than others w/o problems. I datalogged my car when it still had both turbos, and anything above 690 at any speed was too high IMO. This is with the DP completely heat soaked at high speed. Any higher than 690 ment the ECU was pulling timing.
 

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Well I installed the fuel pulsation dampener bypass and a new fuel filter Friday night. It made no difference. :( I will be checking the MAF voltage into and out of the S-AFC to once and for all determine if it is at least trying to do something.

Another thing that may be a problem is the MAF. It was at 97% on my 526rwhp dyno run and I actually hit 99.2% on a 20.5psi pull this weekend. I am wondering if the MAF is really that accurate at those levels. At the top of third I see 650 degrees at 15.5psi, 680 degrees at 18.5psi and 720 degrees at 20.5psi. Regardless of what I set at the S-AFC at.

Mike_Austin,

I have tried the S-AFC in several different configurations including one that doesn't use the low and high throttle settings. I can make the car where it won't rev past 4,000 rpm, but if I lean out at 4,000 rpm and the boost comes up the car revs fast whether I have the AFC set at 0 or +50%. At the top of third I see 650 degrees at 15.5psi, 680 degrees at 18.5psi and 720 degrees at 20.5psi. Regardless of what I set at the S-AFC at.

Later, Steve
 
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Discussion Starter #17
Steve,

is it hard to install the FPD bypass hose?
I just received also from Dusty and gonnna install it myself soon.

I'm having problems with my EGt also as you know, but I'm at BPU. I've been having problems with EGT and A/F ratio. my EGT raises to 740C at the end of 4th , so I can never go into 5th.
whereas my A/F reads 14:1 using 91octan at 18psi.
I replaced my fuel pump, FP regulator, filter, and MAF. nothing is making my EGT nor A/F go down. I even swapped my ECU with my friends but its not ECU cuz his car runs fine with my ECU... my HKS AFR doesnt seem to work either with 20% fuel dialed in. the next thing I'm gonna check is my injectors voltage and signals.....BTw, I have a FP gauge and it reads I have enough fuel pressure.

so my question is, when there is enough fuel presure, does it mean there is enough fuel for the engine?

thanx

Merry Christmas guys!
Jonas
 
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Discussion Starter #18
have you flow matched and / or cleaned your injectors? not just by running injector cleaner but by removing the injectors themselves and sending them out to get them cleaned. I've seen people who send them out and find out 5/6 are basically dribbling and not even spraying.
 
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Discussion Starter #19
that is what I'm gonna do actually, but instead I'm just gonna buy a new set of new injectors. The reason I didnt wanna take out my injectors are because first, its expansive to have them taken out, second, my car wasnt hesitating or sputtering (usual symptom when injectors goes bad), the car was running very smooth and picks up good except for top ends.

thanx for the advice.

Jonas
 
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Discussion Starter #20
i would just send the injectors to rc engineering to have them cleaned and flow matched. i would do this over getting new injectros because even with new inj. you still don't know what you are going to get. if you send them to rc eng. they give you a print out of all 6 injectors to show you that they are all matched and within spec.
 
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