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Lowend and topend power in Subaru engine

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Hi guys that is common knowledge that the torque I destroying the ej engines. As far I know the best way is to shift that power to top end.

I tune couple of ej now but I always getting results very high torque numbers compere to HP. Most of tuners in UK do that in different way they always getting more HP the torque numbers. My question is how they do that ? some1 told me you need to make turbo work harder then your engine. So with my understanding i need to push more boost and lower a timing in low end and go more aggressive in top end. Do I'm right or can some1 put me on right track.

Cam profile and timing, porting, turbo selection, boost control strategy, intake design and exhaust design would probably be the main things.

Realize there is a simple relationship between torque and power. Here is one version: Power (kW) = Torque (N.m) x Speed (RPM) / 9.5488, and here is another Power (HP) = Torque (lb.ft) x Speed (RPM) / 5252

So, you can see that if torque could remain flat, more Speed (RPM) will always make more power. If if the torque drops off, as long as it is gradual, you will make more power at higher engine speed. This is why an F1 engine spins to 20,000+ RPM to make massive power. So get your turbo to work efficiently at higher RPMs, and turn up the boost to make power.

If the Torque at lower RPMs is too much for the components in your engine, you can use boost control to limit boost before 5252 RPM and then raise it to keep the torque up as the RPMs go up. Do you have some way of calculating the torque limits of your components? Do you know how to calculate the maximum RPM based on mean-piston speed?, or determine the proper spring pressure to prevent valve float which will also limit RPM.

As David said, there is a three way relationship between torque, rpm, and power - you can increase power by raising the torque, the rpm, or both.

BTW, David, F1 dropped the high rpm, NA engines in 2013, changing to turbo's

I'm not sure what you mean by torque "destroying" the engine, every engine will have weaknesses that will need to be addressed at various points and it isn't "torque" as such, that's the problem, but how that torque is achieved and what weaknesses are exposed. The other issue is how well the engine has been tuned for the mechanical state of the engine.

If idiots, I mean "tuners", try to use too much boost; insufficient charge, coolant and oil cooling control; poor quality fuel; aggressive ignition timing; even incorrect spark plug heat ranges, etc. then one will, indeed "destroy" the engine.

The easiest thing to do is bleed off the boost at lower rpm, as David said, to reduce the potential for other issues to cause problems and, preferably, increase the operating rpm range - within the mechanical limits of the engine.

The better option is to build the engine using parts and techniques to eliminate, or at least minimise, the weak points that limit the boost and, again preferably, extend the rpm range of the engine. To get the bast gains from this, the turbo'charger(s) size and characteristics, the charge cooling, the fuel, etc, should also be looked at to maximise the potential of the parts.

Something that is often overlooked is just , exactly, what the owner is expecting from the engine - within budget - is it a high speed race car that is going to live at high speeds and rpm, is it for twisty track/back road driving where strong extended rpm is expected, a good responsive engine for casual quick driving - heck, it may even be that the owner does a lot of trips loaded with family, or whatever, maybe even with a caravan, and (s)he wants more mid-range for climbing hills, especially at altitude.

Oh, and what fuel octane they have access too - if they only have access to 95/96 it's no good tuning/building for 99/E85.


Torque limiting is important on any package where you can achieve more torque than a component can handle so your topic is important for Subarus and many others.

Torque is a measure of force so it is more directly related to the max force a component like a rod will tolerate before failure, and horsepower is less directly related since it's not a measure of force. For that reason torque is generally what you want to keep an eye on more than HP if you're trying to work within the limit of a component. Excessive engine RPM, heat, pressure spikes induced by detonation or preignition events are some of the other concerns and potential causes of failures.

As David mentioned, achieving a max desired TQ level and maintaining it will achieve increasing HP with RPM, without exceeding the max force a component like a rod will accept, as long as you don't exceed the engine speed where forces related to engine motion become an issue, or encounter significant knock or other issue.

While tuning, increase boost until you achieve a bit less than your desired TQ level. Continue optimizing fuel/timing, taking boost away if needed to avoid making too much torque, then gradually work your way up to the max TQ you want at each RPM. You might as well leave a few degree buffer to knock or MBT in your timing advance in areas where the engine can easily make more TQ than you want, but don't use extreme timing reductions from optimal timing to avoid extreme exhaust temperatures.

As you increase boost, you'll first achieve peak torque near where you achieve peak boost, with torque generally tapering with increasing RPM. Stop adding boost wherever you've made the torque level you want, only increase boost at engine speeds where you haven't yet reached your desired torque level. At a certain engine speed you may run out of airflow, intercooling, fueling, or hit another limit or safety margin, and it will be prudent to let torque taper beyond that engine speed. If you want to maintain peak TQ to redline, mechanical changes will likely be required and the other folks have made suggestions as to what that may include, such as turbo, fuel system to match that added airflow, etc.

Another reason why you see a lot of EJs with higher peak torque than peak hp is that the stock injectors are easy to max out at higher RPM, so you usually need to taper the boost with increasing rpm. Combining that with the fast spooling effect of the oem turbo, I usually end up with slightly more peak tq than peak hp.

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