ZoomZoomH

after 5252, the torque curve doesn't necessarily fall off, in fact it is perfectly normal if the torque continues to increase after 5252. The only thing that is certain is, after 5252 RPM, the horsepower will always be higher than the torque at the same RPM.

Traveler

Okay. You're right on that one. I was looking through a bunch of old dyno charts and reading some more articles about testing. It depends on the state of tune and what the engine is designed for. Most of the stuff that I'm used to doing didn't rev past 6500 or so and usually torque fell off past 5300. Small and large v-8s mostly.

Orange Crush

I thought that's the only place a Super AFC would work. At wide open throttle all cars function in closed loop, right?! Not just Mazda. Its a predetermined fuel map for power as opposed to efficiency/pollution. The AFC is a very simple device. All it does is intercept the signal from the MAF and fool the ECU into believing there is either more, or less air moving into the engine than there actually is, resulting in more or less fuel accordingly. Where as in open loop mode, the ECU is looking at all the sensors and adjusting accordingly to keep emissions low and keep fuel economy up, so that if you adjust with an AFC, the ECU would just fix your corrections to meet its goals? Am I just mixed up here or what? Could someone explain to me why it won't work?

DanMan

Can I remove my muffler and get those gains. What do Proteges sound like without the muffler. Should I do it , I think I will

Eric F

You are correct. Torque is what is measured by a dyno, and it is multiplied by RPM to get HP. If you see a dyno with one or the other rising while the other is falling, somethings suspect about the dyno.

ZoomZoomH

HP = Torque * RPM / 5252

note: Torque as measured in ft. lb.

this will be on Friday's exam

Eric F

Quoted from Dastek:

"If we measure the torque at the flywheel we will multiply the result with the RPM. On a proper chassis dynamometer we measure the torque on the rollers (of the dynamometer) and multiply it with the road speed of the wheels. Because this torque is not an indication of the torque that the engine delivers I prefer to use the term "tractive effort". Theoretically it doesn’t matter what gear we use to measure the power on the wheels. If we use third gear the tractive effort (torque) will be more than using fourth gear but the speed will be lower. If we use fourth gear the speed will be higher but the tractive effort will be lower. Theoretically the power should be the same.

Unfortunately this is only in theory. Because the speed of the wheels, differential etc are substantially higher in fourth gear than in third the losses are more. In most cases third gear will give a good balance between speed and torque. We only use fourth gear on very high-powered cars where we have problems with the wheels spinning on the rollers.Horsepower, Brake horsepower and Kilowatt

Once we have measured the torque (or tractive effort) and multiplied it with the speed we get the power. The power is expressed in Horsepower or Kilowatt. In the olden days Horsepower was calculated by looking at the displacement of the engine only. This was used to determine the amount of tax that vehicle owners had to pay. This probably worked fine until some clever guy came on the scene and managed to squeeze a lot more power from a 2-litre engine. When the engines started to produce more power per CC than before a new term called "Brake horsepower" came into being. This means that the power is actually measured by making the engine work against a brake. It is measured how hard the brake works to keep the engine at a given RPM. This determines the torque, which is then multiplied with the RPM which gives us power. Kilowatt is the Metric unit for Brake horsepower. One Brake horsepower is equal to 0,746 Kilowatt. Here is another rule: Because power is torque times speed, if a vehicle makes more power at any given speed it must make more torque at the same point! I have seen dynamometer printouts where the power supposedly went up at a certain RPM point but the torque remained the same! This is impossible.

Torque on the wheels doesn’t mean much because a slight difference in tyre profile will show up as a major difference in torque on the wheels. (The power on the wheels will remain about the same). If we take two similar cars with only slightly different profile tyres and run them on a chassis dynamometer we should see that the power is very similar whilst the torque will be radically different. If we test these cars on the road we will find that the power will be an indication of how they perform against each other and not the torque. (Realise that torque on the flywheel is not dependent on gear ratios, tyre profiles etc and has true meaning.)"

zeus

Eric, you need to give this one to Jesse, Dastek is wrong. ZoomZoom's got the conversion, and it can be simply shown, that as torque falls off at a rate less than the rate revs increase, Hp will continue to rise. This is very common in high rev race engines, where small amounts of torque make huge power at high rpm.

The extra credit question is - Why 5252?
There is a mathmatical explaination, but it only has to do with some old British unit for the amount of work an average horse can do. Why don't we all just use NM and KW like the rest of the world.

Eric F

I give up! It's all a mystery to me. I'd just like to figure out an easy way to make more torque OR HP, I don't really care which.

azrakain

Don't give up Eric!!!! In the new SCC they just installed the unichip on their WRX and saw decent gains. They also discussed the pros and cons of the system. I really like the article because it gave me a better understanding on how the piggy back does its magic.

Traveler

You've got it reversed. Closed loop is when all the sensors are giving information and the computer is making adjustments, and open loop is when the computer ignores the sensors and goes to pre-set values and calibrations. Open loop is when it's easier to change values going to the injectors since the computer won't try to adjust anything based on sensor input. That's why you can adjust WOT and not part throttle on a Mazda ECU with a piggy back.

Eric F

Yeah, I read that article also. The pros and cons are close to what Traveler just posted.

Traveler

Houston, we have an exhaust cam! Okay, I've got the cam and I'm going to install it tomorrow time and work permitting. If not, then I'll just do it as time allows this week. I'll try to get it on the dyno again when it's done. I've also found an exhaust shop that does a lot of custom work here. They'll do a 2.25" cat back (eliminates the resonator) with a striaght through design stainless muffler and tip for $190 plus tax. I'm going to probably just do that instead of the Mazda sport exhaust. $30 cheaper and larger pipe to the cat plus it eliminates the resonator. I'll try to test the car with the cam first the same way I had it tested last time. The way it rolls in, open the intake up, and remove the muffler. Should give a pretty good idea what's up. I'll be putting a CAI and the cat back on in the next couple months and will dyno it when it's all done once again.

I'm also pursuing 1 5/8" mandrel bent pipe. I'm going to try to build an emissions legal equal length header similar to what JBA makes for the Focus. I've found the short radius pipes locally. I'm going to need 4 U-bends and 4 90 degree bends. It will retain the stock primary cat in the stock location. It will probably take me a while to get the flanges done and get it all put together. First time trying to make a header (I've done a bunch of exhaust stuff though) so bear with me.

Traveler

I'm probably going to use regular header pipe. The stainless mandrel bends are seriously expensive. The bends I need are still going to run close to $140 for all 8 sections. They are $15-20 each. The 90's are about $15, and the 180's are around $20. The gauge is 16 I'm pretty sure. Do you have a copy of this months Sport Compact Car? I'm trying to duplicate the header that JBA makes for the Focus. It's a shorty header, but loops forward and upward from the head, then turns 180 degrees downward and collects just on top of the primary cat and is an equal length design. I checked into extrude honing the exhaust manifold, but it's way too expensive. How's $385 for the one manifold sound? Yikes!

The biggest prob with making a header is getting the flanges made. I'll have to remove the manifold and take it to a metal fabrication shop. That's what I did with the lower piece that attaches to the bottom of the cat. I'm expecting those to run about $75 for the head flange and cat side flange. I'll look into having it ceramic coated if it ends up producing decent gains.

Traveler

Got it pulled apart today, but will have to re-assemble it tomorrow. Modified the airbox while I had it apart. The K&N drop in filter has a large filter area but the airbox only has a 2 1/2 inch inlet that is restricted further upstream. I put 1/2" holes in an overlapping pattern on the underside, and did the same to the driver's side of the airbox. Should get more air now without getting too much warm engine air.

The Sport 20 exhaust cam is much higher lift than the stocker. The J-spec cam was approximately the same lift as the stocker with longer duration. Not so with the exhaust cam. Gross lift is .340 instead of the stock .320. That's a .020 increase in net lift to .330 from .310. The duration looks about the same as the J-spec intake. I'm guessing that the biggest gains will come from this cam since it will be giving the engine what it needs most, Exhaust flow.