THE LAST Z

iTrader: (5)

Ive seen on alot of these blower cars on the dyno graph after 5,252 rpm, the torque goes down & the HP goes way up like on this one for example:

https://ls1tech.com/forums/dynamomet...rwhp-tune.html

My question is:
Is the HP any good without the torque being up there with it? Ive seen alot of these dyno graphs like this. what does it feel like having 100 hp more than torque at a given rpm after 5252 on a blower car?

In other words, whats the difference between these 2 cars:
car 1 5k - 6.5k 600TQ 600HP
car 2 5k - 6.5k 600TQ 700HP

EdmontonSS

Yeah, it sucks when the horsepower is there without the torque... It makes the engine spin so fast...

Horsepower= [Torque (ft x lbf) x RPM] / 5252

What you "feel" when accelerating is based on the instantaneous torque at the wheels of the car (F=MA).

THE LAST Z

iTrader: (5)

What im trying to say is, according to the dyno graph above, would it be benificial to make the shift point at 6800 instead of 5400 rpm?

EdmontonSS

You'd definitely want to shift at 6800 RPM as opposed to 5400 RPM. The torque at the wheels accelerates the car, but gearing multiplies torque. Generally you want to shift the engine at point which keeps you at the best average power (not torque).

briannutter

Torque is mostly specific to displacement. Power isn't at all. Think F1...Go for the power.

XtraCajunSS

iTrader: (2)

Horsepower is a function of torque. Therefore, you would want to make as much torque as possible at any RPM. The more torque you make at any point translates into more HP.

Shane

JUNK

It might also help him to understand that hp is calculated from torque.....and don't believe any dyno graph that does not have tq and hp EQUAL at 5252rpm.

Wassup Shane?

SimRacer1

wether its torque or horsepower, the main thing we want iss maximum acceleration right?? Is it possible to hook up some kind of telemetry data logging system to your car? Then you use the gs to find out how hard your accelerating at any given rpm and you basically want to keeping revving higher and higher UNTIL you reach the point where shifting into the next gear will allow you to accelerate harder (higher gs) then where you currently at. That will determine your exact shift point. If you use that then depending on your gearing and what rpm you hit once you shift (which depends on your gear ratios) your upshift point will/can be different depending on what gear you are in.

Basically instead of looking at graphs, and gear ratios ( how short or long each gear is, final drive ratio, etc) looking at graphs and power curves, looking at torque curves or a combo of both and using all these formulas, the simple fact is you want maximum acceleration so you keep it in the current gear until you reach the point where the next gear will give you greater acceleration than the gear you are currently in. Using a telemetry (data logger) system can provide you with that.

jimmyblue

iTrader: (11)

An accelerometer tells you everything you need to
know and you can have one for the cost of a used
red-LED G-Tech (real old style) or about $40 in parts
that can be datalogged. I've built them from eval kits
too (Analog Devices and Freescale both make IC
accelerometers).

Basically, you stay in it until you're skeered of breakin'
stuff.

12secSS

iTrader: (30)

This can not happen. HP, TQ and RPM are interlaced. So if one goes up another one would need to move down, to keep the third constant.

If we have 600rwtq at 5000 rpms, that is 570rwhp
Or, if we have 600rwhp at 5000 rpms, that needs 630 rwtq
And, if we have 600rwhp and 700 rwtq, that would be at 4500 rpms.

As mentioned, if TQ goes up, HP will go up at the same RPM point. Also if TQ drops, then HP will come down as well, at that given RPM. In order to have more HP, the same TQ would need to be higher in the RPMs versus the other engine/car.

SimRacer1

AWhat about those dyno graphs where as the hp and rpms rise the torque curve stays really flat??

Does this mean any car with 600 rwtq at 5000 rpm will automatically have 570rwhp at that same rpm? No matter if its n/a, turbo, supercharger, a 6 litre engine or a small high revving 3.5 litre Ferrari engine, etc etc??

EdmontonSS

Then you have a really efficient high-RPM engine, if the torque stays flat, I would just keep spinning that engine faster to make more power... In fact I would spin the engine as fast as I could until the torque started dropping to the point where the power was no longer increasing as the RPM increased.

To make it really basic.

If you have a kazillion billion ft-lb of torque but no engine RPM, you're not going anywhere, there is no power produced. Similarly, if you had an assembly spinning at a kazillion billion RPM but with 0 ft-lb of torque, it wouldn't budge your car.

Torque is force, RPM is rate. Power is the rate of force.



Yes

DanO

Yes

For NA engines there is a limit of how much torque they can make per displacment. You wont see a 3.5L engine making 600 lb-ft of torque, but that doesnt mean it cant make 600 hp... it just has to reach 600 hp by applying its torque output at a much higher RPM, where a larger engine can make 600 lb-ft of torque, it wont have to spin as fast to reach 600 hp. (actually, it will only have to spin to 5252 rpm)

Boosted engines is a different story for the amount of torque vs displacement, however they still must follow the same rules for torque vs. hp

HP = Torque (lb-ft) * RPM / 5252

To get more HP you can either increase Torque or you can increase RPM... or both. For NA to get more HP you must increase RPM (once you've maxed out the torque vs. displacement ability, i.e. Formula 1)

SimRacer1

So theoretically speaking, without changing any parts, you can get more hp out of a n/a engine by just raising rpm?? What about those dyno graphs where the torque and hp starts dropping off at like 7000 or so rpm? Would you simply just dyno tune the low end power out, raise revs and then raise max power and work to optimize the tune for the higher rpm? Sorry I know im out of my league with these technical threads but i find this stuff fascinating, im a hardcore roadracing fan and racecar simulator/game lover so this stuff really interests me.

crashly

deleted....

crashly

here is a engine dyno sheet, from one of my drag engines .....
355 cube sbc , twin 57mm turbos, about 24 psi

the torque is flat , UNTILL the turbos run out of air ( read: out of compressor map)
at about 5400 rpm , the turbo's stop flowing enough air to sustain the required air to fill the cylinders.

ok,
some othe guy's above have already stated that HP = TQ x rpm / 5252
a basic principle of physics...
5252 is a common value, and any engine dyno graph , that does not cross here , is not correct....

as the TQ drops, the the mathamatical equation changes,
the hp continues to rise, UNTIL the TQ figure , falls enough to make the HP figure go south as well....
the rpm value rises, and 'masks" the loss of TQ ,


by reading the dyno graph , we can see where the engine 'falls over' , and can work out a shift point....
by reving the engine past the point of max hp, the gear change will allow the engine to 'hit" the sweet spot of the power , on the rpm drop....( due to change in gear ratio's)
and then allow the engine to be healthy enough to contine to make power and accelerate...

back to the 57mm turbo's,
we can see @ 5300 ish rpm, the turbo's are out of air...
this engine was 355 cubes

355 cubes x 5400 rpm / 3456 = 554.4 cfm

24 psi = 2.63 p2/p1 boost ratio

therefore ( assuming 100 % volumetric effiec)
554.4 x 2.63 = 1459 "turbocharged CFM"

1459 Turbocharged cfm roughly = 100.8 lb's of air per min

sooo , roughly 1008 hp... ( close enough, the engine went 1016 hp )

the turbo's are only good enough for 49 lb's each....
the turbo's are out of air....
so the engine 'falls over"....

this also happens with N/A engines too, due to port size , camshafts etc,

hope this helps to under stand the topic...

ash

wht97ws6ta

Thank you for clearing that up. Ya beat me to it. Ultimately if you never ran out of airflow and had a stable valvetrain and negated friction then any givin motor no matter what the displacement would never stop making power as long as you kept winding it. But everybody with good since knows you cant defy the laws of physics. What lots of people dont know is alot of HP is left on the table with valvetrain combination. Ex. rule of thumb is if you lighten a valve by 1 gram thats an extra 25 rpms before the valvetrain becomes unstable and causes torque to nose over. So 30 grams is an extra 750 rpm that you add to the power band. Not saying this is exact but its an idea of how valvetrain affects power.

got-a-ls1

iTrader: (12)

basically all you need to know is horsepower is a calculation. A car accelerates directly proportional to its torque curve. An engine only makes torque, it doesnt make horsepower. The higher the engine can make torque in the rpms the more mechanical advantage you can use from gearing to multiply that torque to the wheels.

so You want to make as much torque in as high of an rpm as you can(while maintaining driveability) because you can then take advantage of GEARING or more simply put you can do more work (horsepower). F1 cars make shitty torque but since they make that shitty torque at 18,000 rpms they can run gearing to take advantage of that.


Say A turbo ls1 makes 600 ft lbs of torque at 6000 rpms with a 3.42 rear end ratio. Assume 4th gear is used (1:1) so we'll only take into account the rear end gearing. that means the turbo ls1 is putting down to the rear wheels =2,052 ftlbs of torque after gearing.

say An f1 car makes 200 ft lbs of torque at 18,000 rpms. The f1 car can run 3x as high gearing because it has 3 times the rev range. So an f1 car could run a rear end ratio of 10.26. 200*10.26 = 2,052 ftlbs at the rear wheels. obviously not something your looking for in a street car cruising at 6000 rpms lol.

Like said before after a certain point N/A an engine will only make so much torque. After that point bigger heads and bigger cams only raise that peak torque to higher rpms. look at the dyno section for head cam cars. The big head cam cars arnt making more torque then some of the smaller cams but they are making that torque at a much higher rate (rpm) and thus the engine is doing more work. To take advantage of that though you need to run a higher rear end ratio.

A simple way to understand this concept is to see how much harder your car accelerates in 1st gear compared to 2nd gear. gearing is the key, you need to match it to your motors operating(rpm) range and hp/torque output and what your needs are.

I know im kind of rambling now but just trying to help

crashly

great post guys