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Old 01-09-2008, 11:46 PM   #1
vaccine
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Default Timing for Torque Vs power.

i have noticed that looking at pretty much all the standard subaru ROM's that they run less timing around the torque area then ramp it up for power?

Can anyone enlighten me on the idea?
I am about to start playing with my ADM 02STi ROM.
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Old 01-10-2008, 12:34 AM   #2
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Quote:
Originally Posted by vaccine View Post
i have noticed that looking at pretty much all the standard subaru ROM's that they run less timing around the torque area then ramp it up for power?

Can anyone enlighten me on the idea?
I am about to start playing with my ADM 02STi ROM.
Well, you have to think of the engine as it burns the intake charge. At peak TQ/VE, you will need the least amount of timing because the charge burns fast. As engine speed increases, so does power of course (as HP is work done, not force) and the window for the charge to burn decreases as well as the engine falling out of it's peak VE range (which will require more timing). So what you do is ramp timing up as engine speed increases. The key to low end TQ is lean fuel and high boost, not so much timing, but you can get good low end TQ with lower boost and more timing too, but definitely fuel is key here.

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Old 01-12-2008, 06:13 AM   #3
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i am planing on running about 23psi of boost through the mid-range and 20psi @ redline.
By lean mixtures and less timing you mean what mixture wise. i was under the impression that rich mixtures and less timing was the key to torque??

i would much prefer to be tuning for torque rather than outright power. you can see VE/TQ with g/sec. is this the only way to tell if torque is increasing, without the aid of a dyno?
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Old 01-12-2008, 10:46 AM   #4
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20 PSI at redline is a bit much.
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Old 01-12-2008, 11:58 AM   #5
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Originally Posted by vaccine View Post
i am planing on running about 23psi of boost through the mid-range and 20psi @ redline.
By lean mixtures and less timing you mean what mixture wise. i was under the impression that rich mixtures and less timing was the key to torque??

i would much prefer to be tuning for torque rather than outright power. you can see VE/TQ with g/sec. is this the only way to tell if torque is increasing, without the aid of a dyno?
Engine load is related to torque by a constant. If you are increasing engine load, you are increasing torque. However, engine load also is highly dependent on weather conditions (ambient temp, pressure, humidity).

What turbo are you tuning with those target boost numbers?
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Old 01-12-2008, 05:07 PM   #6
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Also... you're looking at this the wrong way.

The point of tuning is to maximize the explosion in the combustion chamber. This never changes, regaurdless of RPM. There's no such thing as "tuning for torque" vs. "tuning for power", at least not with fuel/timing. Shifting the VE curve will change where you make torque, and thus if you make low end power or high end power, which is more what you're thinking tuning will do. But you can only change the VE curve with mechanical tuning, not electronic tuning (except for boost of course, but that's partially mechanical. And even then, you're not actually changing the VE curve of the engine at all, depending on what you consider VE).

Now, in a perfict world, you'd always run 14.7:1 AFR's (as this is stoichametric for gas, and thus means that 100% of the gas could burn), and you'd simply adjust timing as engine speed increased to compensate for the burn time of fuel (yes, there is a 'perfict' timing for every AFR, RPM and VE, called MBT). Unfortunately, we don't live in a perfict world. Because you see, 14.7:1 AFR's burn very, very hot. This is all well and good when you only have, say, 3000 explosions a minute, and are only flowing a couple hundred CFM's (IE Low RPM, low boost). But as you increase the number of explosions and the amount of air you're shoving into the cyclinder increases (remember, the size of the explosions is proportionate to the amount of air you put into the cylinder, and the ratio of air to fuel, with 14.7:1 being 100% burn), the stress on the eingine becomes too much. And so you have to run richer AFR's to make the explosions both cooler and less powerful, and sometimes you can't run optimal timing because the fuel, as piston speed and cyclinder heat starts increasing, starts not burining optimally. This means you'll have to (generally) retard timing, because the fuel is burning faster or in a less controlled maner then it should. When you don't do that, you get detonation.

This is just a basic, BASIC intro to the principals of tuning. But the point is that you don't really "tune" for torque vs. power with your ECU. You always are trying to get maximum power and torque at every given RPM (assuming WOT... cruise is a totally different beast), and are simply limited by the fact that we live in a non-ideal world and that physical limitations of the strengths of our engines means we have to sacrifice some potential power/torque in order to stop the engine from blowing up.

What seperates a good tuner from a bad one is their ability to maximize power at every RPM given the limitations of the system (IE your safty concerns), and how they go about doing it. Do they run richer AFR's, allowing them to get timing closer to MBT without fear of detonation? Or do they run leaner AFR's, and retard timing? Or do they run less boost but leaner AFR's AND closer to MBT timing. Making those choices correctly is THE key to tuning (again, at WOT)

Last edited by AruisDante; 01-12-2008 at 05:14 PM.
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Old 01-12-2008, 05:15 PM   #7
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Originally Posted by wage0052 View Post
Engine load is related to torque by a constant.
This completely ignores optimum fueling and timing. Wrong, wrong, wrong.
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Old 01-12-2008, 05:19 PM   #8
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Indeed. Engine load is simply a measure of how much air you're sucking through the intake (at least with a MAF). It has absolutly NOTHING to do with how efficiently your engine is turning that air into power (and thus torque).
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Old 01-12-2008, 05:26 PM   #9
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What produces the most torque at an RPM point also produces the most horsepower at that RPM. The relationship between torque and horsepower is constant and linear. The original question by OP is not framed in a way to get a good answer because it doesn't seem to grasp this.

If you could only pick one timing value across all loads and RPM, then yes, there would be a dichotomy between choosing that one value for best torque or best horsepower. However, we have a value that is highly dimensional, varying on many, many factors such as RPM, load, air temp, coolant temp, etc.

The discussion might as well start from scratch and ask, "how do I tune timing?" I'm not putting down the question, but this will be a wasteful discussion if it is coming from an angle that is based on false assumptions about being optimal for torque vs. being optimal for horsepower.

Last edited by Freon; 01-12-2008 at 05:31 PM.
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Old 01-12-2008, 05:59 PM   #10
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What produces the most torque at an RPM point also produces the most horsepower at that RPM. The relationship between torque and horsepower is constant and linear. The original question by OP is not framed in a way to get a good answer because it doesn't seem to grasp this.

If you could only pick one timing value across all loads and RPM, then yes, there would be a dichotomy between choosing that one value for best torque or best horsepower. However, we have a value that is highly dimensional, varying on many, many factors such as RPM, load, air temp, coolant temp, etc.

The discussion might as well start from scratch and ask, "how do I tune timing?" I'm not putting down the question, but this will be a wasteful discussion if it is coming from an angle that is based on false assumptions about being optimal for torque vs. being optimal for horsepower.
Actually, I think his biggest problem is that he's confusing Torque for Low End Power. When he says "tuning for Torque", I think he means tuning for low end power. And by "tuning for power", he means tuning for high end power. This is why I said that you can't actually change the shape/position of the VE curve (which would determine if you made low end power or high end power) using air/fuel/boost, which are the things the ECU controls. There isn't a compromise that you have to have in the electronic tuning to get more low end power or more high end power. It's always just trying to get maximum power at all RPM's.
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Old 01-12-2008, 06:03 PM   #11
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Looking back that the origonal question again... I think you might be right as well

To the OP... HP=TQ*RPM/5252. They're related to each other. You can't increase one without increasing the other, and likewise you can't decrease one without decreasing the other.
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Old 01-12-2008, 06:07 PM   #12
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thanx for the answer freon and AruisDante.
i ment increasing TORQUE period, not low end power.. ie like getting torque similar to the rally cars.
so it pulls hard, so that even if there was a trailer on the back , it would not be noticed.
yes i could put a 2.5STi block there, but no, 2ltr is the go.
was un-aware if there was bound relationship between torque and power.

gabedude -> i am running a vf34 with a P20 housing from a vf22 that has had a slight port job on it by myself. i was running this turbo on a LGT before the STi and was running the same boost levels with no problems. the boost levels had been checked on the dyno and were not putting putting it out of its efficiency range and just pushing hot air. fella here in australia is running same setup but 1.5-1.6bar to redline without AVC-S in his GC8 and is doing 11.8 down the quarter very regularly. it makes around 215-220kw atw dependant on dyno. also confirmed by one of the aussie rally gurus whom has done extensive testing on different setups.

Last edited by vaccine; 01-12-2008 at 06:20 PM.
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Old 01-12-2008, 06:28 PM   #13
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thanx for the answer freon and AruisDante.
i ment increasing TORQUE period, not low end power.. ie like getting torque similar to the rally cars.
so it pulls hard, so that even if there was a trailer on the back , it would not be noticed.

You're saying you want low end power.

Look at it this way... if I have 500 FT*LBS of torque, but I'm making it at 6000RPM's, and I only make 100 FT*LBS at 3000RPM's because I have a big turbo on a small engine, you would still say that engine has a lot of torque, but it's not going to be able to tow your trailer to save its life.

People confuse "torque" for low end power all the time. Just because most engines make torque at low RPM's doesn't mean it HAS to be that way. It's just that that makes for good around town driving, since the engine is usually in the low RPM range. Therefore, the car needs low end power, and thus low end torque. But you can just as easily have an engine with high end torque and very little low end torque. In fact, this is how almost ALL race cars, except for WRC cars, are set up, because they want to maximize power, and since power increases lineraly with RPM for a given torque, you want to make as much torque as high in the rev range as possible. As for why WRC cars aren't set up this way, that's a totally different story and has to do with airflow through a 35mm restrictor.

POWER is what accelerates a vehicle. It's directly reltable to acceleration via speed by the equation A=(HP/Speed*375)/Mass (ignoring slip and areo). So if you're making more power at a given speed, you're accelerating faster. Since we're limited in the real world by gear ratios, we have set speeds for given RPM's. So for my "high RPM torque" engine example above, in 1st gear it would have to be going some 25MPH using STI gears before it actually made any power, and thus acceleration.
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