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Discussion Starter · #1 ·
As you all know the supra runs rich naturally and so I asked a guy at a performance shop what I should do. He suggested a AFPR.

How is that going to help?
 

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boost freak
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think of fuel press as a global fueling scaler. more fuel press = more rich, less fuel press = more lean. higher press means that more fuel is released for a given pulse duration.
 

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It's a poor way of tunning. Injectors are designed to work with a specifed pressure. Cutting the pressure reduces the overall flow. Safc , other piggybacks or standalone is the better choice.
 

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slowly giving up...
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i don't think it's a poor way of tuning. i don't think it should be the ONLY way of tuning, but coupled with an SAFC or a MAFT /MAFTpro unit, it can be valuable.

i gained 14-15rwhp by dropping fuel pressure on the dyno...

-shaeff
 

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RoastBeefCurtain Commando
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deff shouldnt be the only way of tuning, but it is a great tuning aid, esp with a piggy back. You can max out an SAFC easily. Fuel pressure helps
Also when you start running higher duties on your injectors, higher pressurse help
 

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boost freak
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shaeff said:
i don't think it's a poor way of tuning. i don't think it should be the ONLY way of tuning, but coupled with an SAFC or a MAFT /MAFTpro unit, it can be valuable.

i gained 14-15rwhp by dropping fuel pressure on the dyno...

-shaeff
agreed. large AFM corrections = wacky timing stuff. use fuel press to get you close, fine tune w/AFM corrections.....
 

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Discussion Starter · #7 ·
Yeah a while back I mentioned using a SAFCII to prevent the 7m from running rich, but a few of you suggested that the TCCS would not let you adjust the amount of fuel being injected and will just compensate for it thus rendering the fuel computer useless, until WOT.

So does the AFPR in a sense override the TCCS?
 

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boost freak
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LordLo said:
Yeah a while back I mentioned using a SAFCII to prevent the 7m from running rich, but a few of you suggested that the TCCS would not let you adjust the amount of fuel being injected and will just compensate for it thus rendering the fuel computer useless, until WOT.

So does the AFPR in a sense override the TCCS?
TCCS will always attempt to achieve stoich closed loop....regardless of what you do. the trick is to tune so as to maintain proper A/F @ WOT and proper Vf.
 

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RoastBeefCurtain Commando
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?
a fuel computer isnt useless. Its only really useless at part throttle because the ECU does the work. You can help it a little if you have huge injectors with the SAFC at part throttle. but the ecu will do most of the correction.

at wot is most deffinately helps
 

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Discussion Starter · #10 ·
PM-Performance said:
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a fuel computer isnt useless. Its only really useless at part throttle because the ECU does the work. You can help it a little if you have huge injectors with the SAFC at part throttle. but the ecu will do most of the correction.

at wot is most deffinately helps
So when does the ECU allow fuel corrections? 50%+ throttle?
 

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I'm just getting my FPR installed this week,what pressure should I set it at? And once I get it installed I can add my VPC and SAFC,are those hard to learn to tune with?
 

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drjonez said:
idle is closed loop, albeit @ a slower rate....
Hey Doc,
I thought I read idle was open. Oh well. Maybe you can answer another question for me then. Why do fuel computers (at least the ones I've had) have a separate idle adjustment? You mean I've been setting idle and the ECU has been coming behind me and readjusting?
 

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Suprastar88t said:
I'm just getting my FPR installed this week,what pressure should I set it at? And once I get it installed I can add my VPC and SAFC,are those hard to learn to tune with?
Stock base FP is 33-40PSI. That is with the vacuum off and plugged. Set it on the high side to be safe then work from there.
0 out the VPC and SAFC and get it as close as you can with the FP then fine tune with the SAFC. Most people just 0 out the VPC at the 12:00 position. It's doing it's job just by converting to speed density and allowing free air passage without AFM restriction.
 

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drjonez said:
TCCS will always attempt to achieve stoich closed loop....regardless of what you do. the trick is to tune so as to maintain proper A/F @ WOT and proper Vf.
I guess i'm blanking right now, what is Vf?

And since the VPC unit was discontinued, is there anything new that accomplishes the same thing (converting to speed density)? Without going maft pro and gm maf sensor?
 

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Most injectors are rated at 40-43 psi. Anything less redudes flow. 40 with the vac off would be best IMO. It will pull it down a few more psi when on at idle. Closed loop is at idle and cruise, unless cold and start up. I don't know at what load of tps setting it goes open loop but it happens beffore WOT. Try unlpugging the O2 with a wideband handy at idle or on the highway.
 

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LordLo said:
So when does the ECU allow fuel corrections? 50%+ throttle?
When ever you're in open loop mode, which (please correct me if I'm wrong) occurs based on coolant temp and throttle position. So if your TPS is disconnected, ECU is effectivly bypassed or if you run no thermostat or a lower temp thermostat (160F I think???).
 
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