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Discussion Starter · #1 ·
what A/F ratio do you guys aim for when tuning your supra for the best spool up and obviously still be on the safe side. I know tuning for low 11s is the comon A/F ration that we should air for under boost (safe tune that is) but does that mean I need to tune for low 11s at even only 1 psi??

if not, then I was thinking I should tune for like high 12s from 0-3 psi then lower that to maybe low 12 to high 11s for 3-8 psi, then low 11s from 8-maximum boost, does that sound right??? what do you guys recommend. please note that I am not messing with the timing at all (Map ECU2)

thanks

Ahmed
 

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There's no one set method or one correct way to do it, thats why tuning is an art... but you're on the right track, you always want to be smooth with your maps, so ideally both your fuel and timing will transition smoothly as your boost rises.
Another real general idea to keep in your head is that they say AFR should look like an inverse graph of your torque curve...
 

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Another real general idea to keep in your head is that they say AFR should look like an inverse graph of your torque curve...
Do you mean that your *timing* map should be inverse of your torque curve?

AFR should be safe under all conditions, and although the optimum would be well into the 12:s on a turbo app, 11's gives a much larger margin of safety. 0-10 psi, you should be ok into the 12's.

Justin
 

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More spool will be found in the timing map.

so alot of timing or retarded timing during spool up. I've heard arguments for both. Just would like to hear your opinion.
 

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The "Tactileneck"
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More spool will be found in the timing map.
^^^^ditto. Also, instead of going straight 11.5 or w/e for your desired final AFR is at high boost, you can slowly transition it down from your cruising values of stoich. Ex. would be like 14.7 cruising value, then as soon as you hit WOT and start seeing boost you can do something like 12.8 at 1-3 pds, 12.4 at 3-6 pds, 12.0 at 6-8 pds, then as you approach you 10 pds it should be getting into the mid/low 11s AFR on pump gas. Again that is just a very crude example and is dependent on a variety of factors. If you can find the right mix of timing w/ AFR and keep everything smooth in the first 10 pds of boost or so it will make a difference.

so alot of timing or retarded timing during spool up. I've heard arguments for both. Just would like to hear your opinion.
There is no set guidline for every car. Advancing it is usually what yields results but this isn't always the case. It's just something that you have to play and see how the car responds.
 

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There are methods regarding "tuning for earlier boost".. Are you trying to tune for earlier positive manifold pressure, or are you trying to tune for earlier torque delivery?

If you want to tune and get earlier boost curve to impress a few guys with an early spooling setup and show off your boost graph, then retarding timing and adding fuel will get "boost" sooner, just like how your anti-lag builds boost off the line. This is dependant on turbo selection, because a lazy spooling turbo will benefit greatly if the turbine quickly picks up its initial speed and then work its way up to full boost of 22 PSI for example. You will get a brief moment of lag due to lack of timing, but as a result, once the turbo picks up speed, it tends to reach higher boost sooner.

If you are looking for quicker and earlier torque delivery, you want to advance the timing and lean out the fuel. You will be tuning for maximum torque at that given load cell with timing and fuel. This lets the engine make use of all the air and fuel going into the engine, and optimum timing (best would be right at knock limit if applicable) will basically give you more HP and torque at a given PSI. If you have a really large and lazy turbo though, the drawback is that all the energy inside the air/fuel mixture is already spent from making power inside the engine and doesn't have much heat energy left to aid in spooling the turbo faster. The boost will usually be a much slower climb up to target (22 PSI for example). What this gives though is the initial "throttle response" and that car begins to pick up and doesn't feel as laggy when you first put the throttle to the floor at lower RPM's. For cars with smaller turbine housings and medium sized turbos, adding timing and tapering the AFR curve is the best way to get quicker power overall.

So when I tune for spool, I ask the owner of the car what characteristic they way from their car. There is no one size fits all.
 
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Discussion Starter · #10 · (Edited)
thanks for the great input guys.

as I mentioned in my first post, I am not really able to tune via timing (map-ecu 2) and currently I have it tuned to where it goes to low 11s as soon as I hit boost, I thought I could improve things a bit and make more power down low by leaning the mixture a bit at low boost (0-3, 3-7, and 7-18) but I am not sure how lean I could go before melting things down at 0-3 and 3-7 psi.

I failed to mention my current mods list in my first post, so here it is.

94 USDM MKIV 6MT.
- DBB Boost Logic T71/81 GTS
- Boost logic 880 injectors and dual denso fuel pump.
- HKS 264 cams with HD springs and retainers.
- ARP head studs torqued to 85lbs
- 4" turbo back exhaust system.
- Map ECU 2

I start seeing positive boost at low 3k rpm and full boost by 4400 or so (18 psi)

another thing, when I first tuned the car via Map ECU2 things were nice and rich at both closed and open loop, a couple of hundred miles later, closed loop became too lean for my taste, I was seeing high 15s A/F at 5psi during part throttle/closed loop driving (stock ECU and fuel trims is what caused it to lean out I guess). so I yanked the stock main O2 and re-tuned to almost perfection (~14.7 during part throttle and below 0 psi, mid 13s A/F 0-5 psi but in closed loop as well. so far I have not had any cold start or warm start issues, nor stalling problems or any negative effects by removing the main O2 sensor, I am planing to keep it disconnected for good as this seems to give me more control over closed loop tune, what you guys think?


thanks again

Ahmed
 

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There's no one set method or one correct way to do it, thats why tuning is an art... but you're on the right track, you always want to be smooth with your maps, so ideally both your fuel and timing will transition smoothly as your boost rises.
Another real general idea to keep in your head is that they say AFR should look like an inverse graph of your torque curve...
correction, your TIMING graph should be the inverse of your torque curve. not AFR
 

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Do you mean that your fuel map should be inverse of your torque curve?

AFR should be safe under all conditions, and although the optimum would be well into the 12:s on a turbo app, 11's gives a much larger margin of safety. 0-10 psi, you should be ok into the 12's.

Justin
typo or was i always mistaken? was under the impression that timing map should represent the opposite of your torque curve.
 

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Discussion Starter · #15 ·
I know Map ECU2 is capable of advancing or retarding timing at a set RPM/Vac/Boost. but I have yet to find someone who has successfully done it. plus to be honest with you guys, messing with timing kindda scares me off a bit (advancing to be more specific)


Do you guys know of any ill effect caused by disconnecting the Main O2 sensor other than cold start or stalling????

thanks


Ahmed
 

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I know Map ECU2 is capable of advancing or retarding timing at a set RPM/Vac/Boost. but I have yet to find someone who has successfully done it. plus to be honest with you guys, messing with timing kindda scares me off a bit (advancing to be more specific)


Do you guys know of any ill effect caused by disconnecting the Main O2 sensor other than cold start or stalling????

thanks


Ahmed
crappy drivability overall...

Justin
 

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Generally a richer then Ideal mixture and a lower then ideal timing value will generate more heat out the exhaust for a quicker spool. So if you do this in a region that won't effect your driveability and transition it out to where the boost comes on strong on it's own, it could help for your application.
 

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The "Tactileneck"
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Generally a richer then Ideal mixture and a lower then ideal timing value will generate more heat out the exhaust for a quicker spool. So if you do this in a region that won't effect your driveability and transition it out to where the boost comes on strong on it's own, it could help for your application.
Explain. How would creating less energy to the turbine wheel help it reach boost faster?
 

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The "Tactileneck"
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????? It creates more energy (heat) out the exhaust ports and to the turbine wheel.
Well then I am missing something here. A leaner mixture gives you hotter EGTs right? Hotter EGTs = more energy right ( to a point of course don't take it to extremes)? So leaner matched with the right timing would then give you the most energy to the turbine wheel. But you're saying richer w/ less timing gives you more energy?
 
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