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Old 10-17-2006, 06:21 AM   #1
HuGo
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Default Torque Pwr Increase?

Its easy to increase horsepower but i hear that torque is the best power that comes out of the engine. Even though you may add stuff to the engine, HP increases but not torque. Well what kind of aftermarkets increases torque and not just horsepower?

Just wondering, do our engines have Cam Gears or are they reffered to something else? If there are cam gears, what performance cam gears can i buy? After the DASC, what else can i do to increase power besides NickG?

When doing a 1.9 to a 2.1 conversion, what do you have to buy/replace to make the conversion?

1.9stock is 138hp, what does 2.1 become in HP? If the engine gets upgraded to 2.1, is the DASC still compatible? TIA.
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Old 10-17-2006, 06:47 AM   #2
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Horsepower and torque are both methods of measuring power. They are directly related, and you can actually calculate one from the other. However, that is not to say that an increase in hp equals an increase in torque.

Greater torque is generally increased from a wider bore or longer stroke. Both however, have a negative effect on the rev limit of the motor (more weight disrupts the rotational balance of the motor, putting stress on the crankshaft & bearings).

Camshafts (the gears just drive it, and yes we have these, attached to the timing chain) can be changed to retard the valve timing which can but not necessarily will, result in an increase in torque, but at the risk of bending valves or poor emissions. With an increase in torque here, you sacrifice hp. Given the way BMW engineers their motors, I'd say this is a BAD way to go about it. I know the guys at Avus had to rebuild a motor from a guy that did cams on a FI'd motor.
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Old 10-17-2006, 06:06 PM   #3
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hehehe.. No, I think you will find that as soon as you add a supercharger you really limit yourself with what you can do with the car. Which is why I told you I wasn't going to be a part of the DASC group buy. You can do the stage3, but anything after that will have to be a completely custom job, and will cost you a lot of money. If you are not going to be happy with the power put out by the dasc with the stage3 you should have gone with an i6 conversion, or a built out NA m44. But honestly, you should wait until you have the dasc into the car before you worry about whether or not it needs more power.

The other big problem that I have heard with trying to get more power out of the dasc is that it is just about impossible to run any type of intercooler with the car because of how it mounts. I know that one member had put together the parts to do it, but there wasn't much interest. I think it was 1500 for just the intercooler parts. If you don't cool down the supercharger you are going to have issues with predetonation. The last time I was out at Sebring I was talking to another Ti owner and he told me that a few months before the event that we were at some guy blew up his DASC Ti. It just got to hot running in excess of 10psi in the Florida heat out at the track. I'm not sure if he was using the TT Stage3 kit, or had bumped up the output of the DASC on his own.

I really don't think you have the ability to do a 2.2 liter conversion. It is not as simple as just dropping in some new parts. The parts alone to build a 2.2 liter properly are a few grand.
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Old 10-17-2006, 08:26 PM   #4
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90% of torque (slightly made up number, but it is high) comes from displacement. That is where the saying "There is no replacement for displacement" comes from, and to an extent it is true. The alternative source is to force more air into a smaller cylinder at a higher pressure. So the only real replacement for displacement is forced induction.

Power is a function of the torque at a given RPM. Torque is the force that makes the vehicle move. Grossly over-simplifying vehicles tend to have 1 of three torque curves. One, where most of the torque at low RPM, two, have a flat torque curve (where most of the torque is available in the middle RPMS), and three, where the torque is available at high rpms. A torque curve skewed to the low RPMs will tend to have a higher peak torque, the flat curve has about the same torque over a wide range (although a lower peak number), and the high RPM engines tend to have the least peak torque.

Trucks tend to fall into the first category, with large displacement engines and they are tuned (with cams and such) to produce most of their torque at low RPMs so they can pull a load effectively. Some of the lighter duty trucks have a flatter torque curve. Most BMWs and the like are known for their flat torque curve, that is what makes them so nice to drive; the engine doesn't feel peaky (like you have to rev the crap out of it to get any power), although the power number might be slightly less. Honda's tend to have peaky engines with all their torque at high RPMS and you have to rev them to 7000 rpm to make any power. These tend to be smaller engines with lighter parts. The reason they are fast is they can accelerate longer in each gear (8k rpm redline). Their instantaneous acceleration will be much slower than a big truck, it is just that the truck has to shift by 15 mph where the little civic can keep revving.

The vehicles that accelerate the fastest tend to have slightly more horsepower than torque, but it depends a lot on the vehicle weight, gearing, etc. Larger engines and vehicles will be closer to 1:1, whereas smaller vehicles and smaller engines might be more like 3:2 hp to torque. Too little torque and the vehicle can't move, and too much torque and the vehicle won't be able to rev very high. Variable valve timing helps reduce this, having the ability to have some torque at low RPMs and have power at high RPMs by effectively having multiple cam profiles.

This is why the Acura 1.8 from the GSR performs so much better than the M42 from the same time. The BMW has only standard cams and no variable valve timing, whereas the Acura has VTEC. It can keep its flat torque curve, but still have the upper end revs that the BMW is lacking. Both vehicles have about the same torque and will accelerate about the same under 6500 rpm, but the Acura keeps going for another 1000 rpms, boosting its peak hp to 170 (or about 30 more than the bimmer). If you don't want to run your engines at that high of RPM (I think the GSR rev limits at around 8000), buy a larger displacement engine.

Forced induction forces more fuel and air into the cylinders, upping your torque at all RPMS where the supercharger works (turbos don't kick in until the exhuast gas gets the turbine spinning fast enough). Forced induction has a very similar effect as switching to a bigger engine.

Again, all these descriptions are over simplified.

To answer your question, if you are increasing horsepower you are increasing either your torque, or changing where it is distributed. For example, a free flowing exhaust may shift your torque curve to a slightly higher RPM, so you will see a decrease in low rpm torque for a trade off in peak power at higher rpm.

Forced induction (or adding displacement) are really your only means to gain significant torque AND power. Otherwise you are essentially tuning your torque curve to produce more torque and less power or visa versa, e.g. changing to a racing cam might make your car undrivable on the street but give a huge boost on the track.
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Old 10-17-2006, 08:34 PM   #5
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In order to bore out the 1.9 to 2.1L, you need to physically remove metal from the cylinder to make the volume bigger. You will need a larger piston and different components inside to add stroke or bore. It's not an easy task and I don't think you could do it without a large expense and sending it to a professional. It's just not easy. I don't see why it would be a problem with FI though as long as compression is lowered (since FI will add more stress to the motor and increasing cylinder volume weakens side walls). You will basically max out your motor with the DASC unless you add nitrous or water/alcohol injection (Which are both inherently risky).
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