If our engine, transmittion or whateever is 100% effient, does that mean we will have 255hp to the wheel? Is that the correct way to think about flywheel hp and wheel hp?
If that is correct, upgrading the exhaust and intake only makes the engine more effiecient, right? It doesn't really increase the engine's hp output. Therefore, no matter how free flow they are, the maximum hp can be produced to the wheels from our 3.5VQ engine is still 255? Is this correct? In other words, if Nissan made our 2k2 maximas with Injen intake, and all the exhuast mod out there, they would still have to rate their car at 255hp. Am i correct? Anyone know the facts? speculation is alright too i guess....

 

you were correct to start but then you were mistaken. the maxima's VQ is rated to produce 255 horsepower at the crank or flywheel. but due to physics and all of that good stuff some of the horsepower is lost in the drivetrain while it is on it's way to the wheels. usually around 18-25% of the crank horsepower is lost in the drivetrain depending on the car and depending on the type of transmission. (manual transmissions are more efficient than automatics)

adding things such as an intake or exhaust will increase the overall horsepower that the engine is producing. so with an intake the maxima is theoretically producing about 268 horsepower at the flywheel but some of THAT is lost in the drivetrain. so an intake will only net you about 10 horsepower at the wheels (And 13 horsepower at the crank)because you are still going to lose that same 18-25% through the drivetrain.

adding bolt-ons increases the total horsepower of the engine but does increase not the efficiency of the automobile.

 

So you are saying the hp lost is at the drivetrain, not because of restrictive airflow and what not?
is transmission the samething as drivetrain?
are those upgrade performance clutch system the whole transmission or part of the whole transmission?

 

And, how do we make the drivetrain more effeiceint? there are far more effeieceint cars out there, so it can be done obviously.

 

right. its like if heat up the end of a fork with a lighter. one end will be very hot (the crank) and the further away from the flame the less hot the fork gets because the heat dissipates as it travels through the fork. kind of a dumb metaphor but i think you get what i an saying.

the transmission is part of the drivetrain. everything that connects the crank or flywheel to the wheels are part of the drivetrain and they all rob a little bit of power as the power runs through them.


the clutch is only part of the transmission. it is what allows the gears in the transmission to engage and disengage when gears are shiftd.

 

Newman is right, adding mods increases the actual output of engine, but you were right in a sense. A restrictive intake and restrictive exhaust would limit the power of the engine, for instance, covering up half the intake filter and making a tighter exhaust diameter would make the 3.5L 255hp engine make less output, lets just say 220hp, freeing up the intake and exhaust entirely, meaning no filter and no exhaust, and the output may increase to lets say 280hp. In this case, the actualy capable output of the engine would be 280hp, meaning Nissan made a 280 3.5L engine, but after they put on the intake and exhaust for the maxima to quiet things down and so forth, the output had been brought down to 255. When u add aftermarket intake and exhaust, what you are doing in essence is freeing up the HP that the engine would have made originally had the restrictive designs not been there. So yes, u are technically freeing up HP that the engine can already make, with simple bolt ons ur nearing the output that the engine can make when unrestricted. the 3.5VQ is a perfect example, the Altima makes 240(debateable), Maxima 255, 350Z 287(debateable), G35 260, G35Coupe 280, Nissan put the most restricted one on the Altima, Maxima and G35, then freed up the existing power for the 350Z and G35Coupe. The engines itself makes more power, but its not to say the power to make wasnt already there to begin with, if the design of the 350Z and G35Coupe is so good, there might not be much to free up, those 2 cars getting I/H/E might net them 15-20hp while on the more restricted ones net them 25-30hp. Take Hondas DOHC 4bangers for example, a full I/H/E setup on those cars rarely nets them more than 10WHP, doesnt mean the engines are weak, or that the power isnt there, but that the stock designs werent extremely restrictive.

Sorry about the long post, but Newman is entirely right, adding mods does make the engine make more power.

 

there are more efficient cars out there but it has to do with all of their compnents. you could make your maxima's drivetrain more efficient but that would require making MAJOR changes to everything on the car. it CAN be done with A LOT of time and money it would definitely NOT be worth it.

 

horsepower, typically without ANY parasitic losses from water pumps, alternators, power steerng pumps, etc etc ad nauseum.

HP to the wheels is the output of the engine as installed in the car -obviously, driving all those 'parasitic' devices plus reduced by the inefficiencies/losses in the drive train.

The basic reason why automatics lose more HP than manual trannies is because most of the gears inside the tranny itself are 'planetary' gears where one gear actually drives a few smaller gears inside the larger one -so you have more gears (up to 2x the gears) per gear ratio than a manual box where you have just two gears for each shift (gear ratio). The second is that to run a slush box you need a high-pressure oil pump inside the tranny itself tasked with building up the pressures the hydraulics inside the tranny need to operate: valve bodies, clutches, etc. This pressure pump consumes anywhere from 6-8 hp alone....

UDPs work well because they reduce the parasitic losses from the engine-driven ancilliaries, but on a manual tranny itself the way to reduce losses are to change to low-friction bearings throughout
and/or change to straight-cut gears from the helical gears in it now -at the expense of HUGE increases in gear whine, which is why racing boxes have straight-cut gears, BTW.

Lighter clutches and flywheels do NOT reduce drive train losses, they merely reduce rotational inertia throughout such that you do indeed see some improved acceleration but...that doe not equate to more wheel HP in a steady-state full-throttle pull.

Bottom line, there is no cheap, feasible way to reduce these parasitic losses except an UDP and nothing on the tranny itself -except buying a manual in lieu of an auto to begin with...

 

. so with an intake the maxima is theoretically producing about 268 horsepower at the flywheel but some of THAT is lost in the drivetrain. so an intake will only net you about 10 horsepower at the wheels (And 13 horsepower at the crank)because you are still going to lose that same 18-25% through the drivetrain.


Wow what kind of an intake r u using that it gives your 10 hp at the wheels, I want one too

 

frankencar intake dyno'd 10 HP to the wheels.

 

With intake we have more like 250 crank HP

 

yeah, i was pretending that nissan actually makes a 255 HP maxima.
you get the idea

 

Galo, I believe that when the SAE changed the standard in the early 70's to net HP on engines, water pumps, alternators, etc. were included on the engine to get the "net" HP ratings. the prior "gross" HP system was a bare engine with no accessories.

Thus, the 255 HP rating of the VQ in the Maxima "should" be "net" HP (with all accessories attached) at the flywheel.

Hope this is of some use.

 

PoweredbyNissan, you seem genuinely interested in cars and what not, given all the questions I've seen come from you, I would suggest getting a thorough automobile mechanics book. I've got one and it explains just about everything. I highly recommend Automotive Mechanics by Crouse and Anglin or the Automotive Encyclopedia by Goodheart and Willcox. They are somewhat dated using a lot of Detroit examples, but good references nonetheless.

 

i dont think thats right. if you decrease any rotational weight the car will accel faster, and in order for the car to accel faster is has to be putting more hp and torque to the ground. so adding things to the tranny, like a clutch, flywheel, better fluid and better diff is going to "free" up hp, it may not be a large amount but its something.

 

Thanks for all the input guys. That does help clear things up for me. Am I the only one curious about those technical questions? I am surprised no one else asks these questions more often.

 

It's not really a surprise IMHO, these items have been discussed actively and passively in a lot of posts. In fact i learned more about cars and how the Max works just reading through other people's posts.

 

it doesnt free anything up. read your second sentence..."if you decrease any rotational weight the car will accel faster,". you are correct with that but the way you followed it up was incorrect. less weight will allow the car to accelerate faster because the SAME amount of power is being used to propel a lighter weight.

its like if you throw a 10 lb weight with 1 hand it will only go 5 feet. but if you take 9 lbs off and throw a 1 pound weight it will go 20 feet. it doesnt mean you are getting any stronger. it just means that you are able to do more with the strength you already have.

 

nice example. couldn't have said it better..
i wanted to actually say something in this post.. but i just read it today. and some questions i actually knew some answers.. but post after post.. it gets too thorough and precise that i didn't even know.. can't believe im learning lots of stuff. especially this thread lol

 

thanks for all the posts, I've found this thead to be very informative.

 

you know what, i completely forgot about the weight of the car, so yes you are right that your not actually crteating or "freeing" up hp or torque but making the rotational weight lower and thus the overall weight. although the only things i can think of that would make the car's drivetrain more efficent is a harsher clutch, wont make much difference but some, a better diff and better motor mounts. the motor mounts is something a lot of people overlook and just take for granted, but new cars come with softer and softer mounts today in order to decrease in cab vibrations.

now with the UDP i dont understand how that is freeing up hp. its kinda like changing the gear ratio in a tranny. its creating hp and torque.

 

at the SAE (Society of Automotive Enginers web site & confirmed you are correct...SAE 'net' HP should consider all the parasitic anciliaries normally operating..A/C not one of them, but PS pump, alternator, etc yes -good catch!

To the last post, an UDP will improve both SAE net crank (see, I learn quick) HP and then of course wheel HP as well because it spins these anciliaries at slower speeds (PS pump, alternator, etc) thus reducing the parasitic losses required to operate these accessories

 

An UDP will also free up horsepower due to lighter weights. You can gain a little more than 2.5 hp for every pound taken off the crankshaft...

 

That's not all that much.........and it costs like almost 200 bucks....

 

please read and think before you respond-- I mentioned 2.5 hp per every pound lightened, not a 2.5 hp total gain. UR claims at least 5+hp on a n/a engine, significantly more on a forced induction engine. Along the same lines, a lightened flywheel cound free up 10+ hp depending on the application...

 

lets face it, there is no dirt cheap way to get horsepower in cars these days. I read somewhere that in cost, it averages about $15-$25 per 1 hp in a car. For example frankencar 10hp = $150 (just off the top of my head... don't get me on specific pricing), Injen CAI 10hp = $220, $22 per 1 hp.. etc etc

 

well put. and this is especially true for our cars.

 

I read what you said, but an aftermarket UDP only weights like 1 or 2 pounds less than stock UDP, probably not even that much less......

 

http://www.custommaxima.com/UnorthodoxPulley.htm

the stock pully weighs in at 4.8 lbs. Unorthodox Racing UDP weighs in at 1.56 lbs. that is 3.24 lbs less.
going by the numbers stated by Unorthodox Racing saying that an average of 2.7 hp is gained from every pound taken off the crank shaft:

3.24 lbs x 2.7 hp per lb = 8.748 hp

 

AND the pulley has a smaller radius. Like switching from 20" chromes to 15" light weight rims.