Real hp guesstimate just for fun

[cdover73]

Anybody wanna take a stab to help me figure where I'm at in my build? I am curious to see what the opinions are. I haven't made it far yet, but I think I have enough to at least start bumping the numbers a little. Looking for either crank or rwhp guesses. This will also help me determine how much further I have to reach my goal.

Starting from stock advertised numbers:

K&N cai
Lighter than stock Spec Stage 2+ clutch & pp
Fidanza flywheel
Stock gears
Stock headers
Random Tech high flow cats
Mopar Performance (made by Borla) cat back
No power adders

I still plan on adding gears, head/intake work, cam, and a dyno tune. What you think would be the final numbers while we're at it? We'll confirm how close we get when I do the tune and spin the dyno.

Thanks,

 

[ViperJeff]

And whats the starting HP # (crank/wheels)

I don't know if you dyno'd it before you started

 

[steve e]

With basically just a K&N and exhaust, maybe 20 to 30 hp over stock, if you can ditch the cats maybe 40 to 50 not all cars react the same with mods, some cars gain more than others.

 

[cdover73]

Stock before. No prior dyno. Just assuming advertised hp as a baseline.

Steve-e, i totally agree with outcome. Thats why im asking here, as well as for fun as stated, but it gives me more of a justification for the work im doing if I can expect to see real numbers.

 

[steve e]

One thing is for sure, its going to be fast.

 

[shooter_t1]

03 Gen III started out at 505 HP @ the crank. With the K&N CAI, RT Hi-flow cats and Mopar catback, I bet your 540-550@ the crank. The Fidenza flywheel and clutch will allow it to build revs quicker, plus lower the weight. The real benefit was getting rid of the "snakes mess" Gen 3 Exhaust with crossover. The Mopar is much cooler and lighter. Now find a CC oilpan and swingarm pickup to make it more reliable around long sweepers. I think a Gen IV oilpan& swingarm will work too.

 

[MoparMap]

I don't think you'll see that much gain with just a catback and no tune. Stock cars dyno around 430 at the tires, I'd guess maybe 450 with the basic bolt ons and no computer work. With a tune you might get closer to 480-500. For what it's worth, my car with just a K&N and Borla catback (still had the factory cats) and a tune dyno'd 480-490. I put M&M headers on and had to remove the cats to do it and it bumped me to 500, though I haven't had it retuned, so it might have a little more to give if I wanted to.

Gears and flywheels always seem to have funny effects. To a certain degree they should not add or remove any power, they just allow it to be delivered a little differently. You might "lose" some power spinning up a heavier clutch/flywheel, but you have more inertia that keeps the engine spinning between gears, so you kind of get it back. I've heard higher numerical ratio gears tend to sap a little more power because they're slightly less efficient, but I'm not sure I quite follow the physics behind that one just yet.

 

[Kirkinsb]

Another thing to think about is the elevation you live. I live about 4700 feet.....which really ***** HP!

With similar mods as OP, mine dynod at 445hp and 490tq at the wheels at 4700 feet elevation. If I were to dyno it at sea level, I would gain nearly 50-60hp.

HP Loss = (elevation x 0.03 x horsepower @ sea level)/1000

Anyways....elevation is HUGE and I don't see many guys throw that in the mix. Perhaps because most live in lower elevations??? Dunno. But 4700 feet elevation blows!


I am catless, with Roe SCT tune, 3.55 gears, Roe Air Filters, Under-drive pulley (yes it added 10hp), New plugs & wires, still have full OEM exhaust-but with large diameter Magnaflow muffs,.....but that is about it, no other power-adders.

 

[cdover73]

Anyways....elevation is HUGE and I don't see many guys throw that in the mix.

This is definitely true. I bought a truck once up in Washington state and ended up driving it home when I moved back to Louisiana. I was pulling all our stuff in an enclosed U-haul trailer and was getting ~10mpg. I figured once I got home and dropped the trailer it would pick back up to the 17 or so I was getting. Nope! I still got 10mpg. So I took it in one day for a crankshaft position sensor and the dealership told me they re-flashed to PCM to change the barometric settings. Apparently it was programmed for higher elevations and when I brought it to sea level it was confusing the computer. It was getting more air so it was cramming the fuel to it to compensate. Once they reset it for sea level I immediately went back up to 17-20mpg.

Also, regarding parasitic loss, there is an expected 15-20% loss from crank to ground. The friction of the gearing in the tranny and rear diff robs power. We all know that and it is expected. That's why dyno results at the wheels is always lower than an engine dyno at the crank. However, these cars are running an advanced design drivetrain so I would expect a little less of a loss. For example, when I had my car on jack stands doing the exhaust the other day, I could spin the front wheels and they would keep turning way longer than those on my other vehicles. This tells me the wheel bearing are higher quality and have less rotating friction. This reduction in friction is what I would expect to decrease the percentage of parasitic loss. But how much is the question.

Basically, the only way to truly know your power is to spin it on a dyno. As a reminder, the main purpose of this thread was to get my mind wrapped around what is to be expected as I progress through my upgrades. I'm not doing anything nobody else hasn't done. I just wanted to put some realism in the equation, and everyone that has replied is spot on what I was looking for. Once I finish and get the dyno tune I will post back here for comparison. It will be a while before that happens though. The end result is to have a go-to post on our board that other people doing the same mods can have some sort of a guideline as to what works and what doesn't. And above all, to let everyone know that throwing money at "go fast" goodies doesn't always produce the advertised results.

 

[cdover73]

Another question I have is once you exceed 500hp, which is basically where most of our cars start as advertised (at least Gen3's), is it really possible to 'feel' hp increases in short increments (~40hp at a time)? There is already enough seat of the pants feel when stock. I would imagine short bursts of increases in hp wouldn't be as noticeable as say adding 50hp to a Camry. Since a Camry is more around the ~200 hp mark(I'm guessing here), then 50hp would be very noticeable. But what does it take in our cars to really feel additional hp? 100hp? 200hp? What do you think?

 

[cdover73]

And one more question (sorry...) For those of you with cams, is it worth the expense versus the gain? I ultimately want a lopey idle that gives the car that true muscle appeal when it's sitting there idling and 'counting' off as the cam hits. Nothing extreme, just a nice lope. Is that possible with a Gen 3 stock cam and custom tune? Or do I need to consider a cam swap to get there? Of course I want the added power as justification. Doing a swap just to change the way the car sounds is not what I'm asking for, but what are the real options to get what I am looking for?

 

[MoparMap]

Also, regarding parasitic loss, there is an expected 15-20% loss from crank to ground. The friction of the gearing in the tranny and rear diff robs power. We all know that and it is expected. That's why dyno results at the wheels is always lower than an engine dyno at the crank. However, these cars are running an advanced design drivetrain so I would expect a little less of a loss. For example, when I had my car on jack stands doing the exhaust the other day, I could spin the front wheels and they would keep turning way longer than those on my other vehicles. This tells me the wheel bearing are higher quality and have less rotating friction. This reduction in friction is what I would expect to decrease the percentage of parasitic loss. But how much is the question.

Yeah, this is certainly true and I think modern drivetrains have gotten much better about it. In a certain sense this is free power that was just being wasted before. I always heard the 20% for an automatic and 15% for a manual as the rule of thumb numbers. They say automatics are getting better, but I'm still not sure I believe it based on some numbers I have seen. I do know that it is much easier to push a modern car than an old one though, lol. I had a 2000 XKR that I would almost swear that if you leaned against it in neutral it would roll away. My 67 Dart (despite having a modern engine and transmission) dang near requires three people to roll it up a shallow driveway.