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Young At Heart
1993 Mr2
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463 Posts
Discussion Starter #1
I heard from a reliable friend that if I were to purchase the S-AFC, and tune the car running 16 psi going from 11 to 1 to 12 to 1 ratio with the stock turbo, not only does the turbo pull through the entire rpm range, but also increases me 45 hp???This is with aftermarket exhaust, BC, stock IC, Greddy Cold air intake, everything else is stock.... is this true... he has an 13.1 second 2
 

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I love Cin
91 Turbo MR2
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2,312 Posts
Nothing makes the stock turbo pull to redline ... it's physically impossible as the turbine housing is too small in relation to the displacement of hte engine X the rpms "up top."

I would never run the stock turbo over 15 psi.

If you want more boost, get a bigger turbo.

Although the SAFC can be used to lean out the A/F for an increase power,
this can be a very dangerous game to play on the MR2.

The SAFC lies to the ECU about the amount of air coming in so that the ECU sends less fuel.
The problem is, on the MR2, the ECU sees this less amount of air and it advances timing.

Advanced timing + leaning fuel + boost = blown up engine

SAFC can be used succesffuly on the MR2, but they are a risky game to play.
At the absolute least, you are going to need to set up an ajustable fuell pressure regulator.
Like this: http://www.trueleo.com/fpr.htm
All of those parts aren't exactly cheap either.
 

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Audi Technician
91 MR2
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774 Posts
yea it requires alot of replacing parts not just tuning to alter your power band...

and i would imagine your car has higher than 12 to 1 A/F ratio...

because 14.7 to 1 A/F is where any car runs while producing the least amount of harmful emissions... its called stoictiometry (sp?) this what every manufacturer sets it for... except newer cars they found a way to run higher keeping emissions down... only problem is NOx... which starts to become a problem around 16 to 1 A/F.

the fact your / someone is running 11 to 1 right now sounds way to rich to me...
 

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I love Cin
91 Turbo MR2
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2,312 Posts
tHa kNiGHt FaLL said:
yea it requires alot of replacing parts not just tuning to alter your power band.
Just the fuel pressure regulator stuff I referred to.

tHa kNiGHt FaLL said:
and i would imagine your car has higher than 12 to 1 A/F ratio...
A/F ratio is not constant. It changes as you drive. What you see at idle, is not what you would see under boost.

tHa kNiGHt FaLL said:
because 14.7 to 1 A/F is where any car runs while producing the least amount of harmful emissions... its called stoictiometry (sp?) this what every manufacturer sets it for...
The MR2 might see around 14.7:1 during idle and cruise, but I assure you Toyota does not have it "set" for 14.7:1 while you are under boost. Most turbo MR2s see around 10:1 - 11:1 when boosting ... yes, that is rich, but it is also safe. If you were seeing 14.7:1 under boost, you would most likely be blowing engines.

tHa kNiGHt FaLL said:
the fact your / someone is running 11 to 1 right now sounds way to rich to me...
11:1 is a fairly safe place to be under boost.
12:1 is a good target for making some power and not being too lean.
See my A/F graph at the bottom of the chart as it floats just under 12:1
http://www.mr2ownersclub.com/mr2records/dyno/Hyde_dyno_567.jpg
 

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i would also recommend not touching it until you get on a dyno to tune it. also remember you need to purchase the extended wiring kit. wiring it is a piece of cake though.

my tuner set mine to about 11.5 : 1 on a stock motor. saw a nice little jump (about 15-20rwp iirc) but i was running a jdm ecu and the a/f was buried under 10 under boost.

when all is said and done, i would have just went with the ats tuned rom. that way the timing is safe and it allows the ecu to monitor all of the true values. i sometimes worry about how much "lying" is going on.
 

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Zz_005_zZ said:
This is with aftermarket exhaust, BC, stock IC, Greddy Cold air intake, everything else is stock.... is this true... he has an 13.1 second 2
is this on a gen 3 engine? its *possible* on a gen 2 but it would be VERY remarkable. most of the mr2s i have seen at the track with similiar mods run 13.8-14.2 on street tires.

another thing to think about is the subpar fuel rail the gen2 has. i would address this b4 i start leaning the mixture out.

excellent writeup:

http://www.mrcontrols.com/primers/power.htm
 

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Young At Heart
1993 Mr2
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463 Posts
Discussion Starter #7
keck03 said:
is this on a gen 3 engine? its *possible* on a gen 2 but it would be VERY remarkable. most of the mr2s i have seen at the track with similiar mods run 13.8-14.2 on street tires.

another thing to think about is the subpar fuel rail the gen2 has. i would address this b4 i start leaning the mixture out.

excellent writeup:

http://www.mrcontrols.com/primers/power.htm
I guess I confused you... those are the mods on my car... my friends car has an aftermarket intercooler, and a stroker motor... alng with many other mods.
 

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oic now. i actually hear great results with a powerfc on a gen3. i *think* you can control both the timing and the air/fuel so everything is still safe.

and yeah with a stroker your friend shld have no problems hitting those numbers.
 

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MRQturbo said:
^^a power FC is not comparable to a SAFC..one is an EMS while the other is a "piggy back" box...
i know but the added features of the powerfc would lessen the chance of blowing up the engine.
 
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