R.P.M.

So a customer wants as much torque as possible out of the 13B Cosmo RE motor I'm putting together for him.

He's planning on using a GT35R turbo which should easily produce 400whp. But now his goal is to get around 400ft/lbs of torque.



How can I acheive this? Would it be best to leave the ports stock? maybe just port the exhaust?



What do you guys think?



Joe

BigTurbo74

install a v8?



hah, what's the application for the car?

Lynn E. Hanover

Well, you have to pick one of the below................





Torque is what a dyno measures.



you supply an RPM where that torque is being delivered

and you can come up with a HP figure.



One HP is 33,000 pounds lifted 1 foot in one minute.



So a distance (one revolution)is required.



A weight (33,000 pounds) is required.



A length of time is required (one minute).



An easy to use formula is: Torque X RPM

----------- = Horse Power

5252



(HP=A statement of work in a period of time)



Let us say that we dyno the proposed engine, the best torque is recovered at 8,000 RPM.



Your 400 HP requirement would mean that we would see a torque reading of 262.5 foot pounds.



The requrement for 400 foot pounds of torque plugged in to the same engine would produce



609 HP at that same 8,000 RPM.



So the customer is asking for two things.



How about just the fasted street car ever built, or one that can fly to the moon.



If you could stand a bit higher revs you could do the 600+ streetable HP number.



For example, that 262.5 foot pounds at 10,000 RPM would be 500 HP



Torque output is the expensive part of engine design.



However, RPM is available at the throttle, so more revs will add to the HP number in most cases, right up to

max revs Depending on where that might be.



About 12% driveline losses would mean you need about 682 at the flywheel to show your customer 609 at the wheels.



I would avarage a bunch of turbo dyno runs and build a data base on the boost, mixture, ports, advance

and so on. Suggest the customer would be happier with a bit less power from an engine that will last a number of years rather than weeks.





Lynn E. Hanover

BDC

400ft/lbs of torque roughly equals 500hp out of your garden variety, ported 13B.



B

diabolical1

my thinking is the exact opposite should yield more torque. i'd probably do a regular streetport on the intakes, but leave the exhausts smaller than usual. keep the RE exhaust inserts. doubt if that in itself will lead to 400 ft-lbs, but i think it should shift the engine's torque characteristics closer to a plateau.



however, i'm not an expert and i've yet to put together a 400 HP motor, so take it with a grain of salt.

j9fd3s

lyn summed up the dilemma best, actually the request isnt very clear. does the guy want low rpm power? or high rpm power? or are we trying to make 400lbsft at 5250rpms?

R.P.M.

Well basically he will be using the car for track events and some street rally races, so he wants low end torque to pull good out of the corners.



I'm assuming we are going to need to build him a 600whp motor to get the 400ft/lbs of torque?

Or is there some porting tricks that would help with the torque. Would leaving the RE exhaust diffuser in the housing actually help with low end torque? We are going to be using the stock RE intakes and throttle body so none of that will be changing.

Old Splatterhand

no smartass comment, but:

does he really know what torque and power is?

Lynn E. Hanover

Remember, Math is our friend.



400 foot pounds of torque will produce 500 Horse power at 6,565 RPM.



If you can build it they will come.



I have never worked on a turbo so I should shut up and read, but there are some constants that may help.





The rotary is low on torque due to the short stroke. (Short lever arm).



You wouldn't buy a breaker bar with a 6" handle. You would buy a breaker bar with a 26" handle and slip a 4' length of pipe over it to get additional leverage. (A longer lever).



So the rotary is poor at making gobs of torque because of its design. In order to put out gobs of torque at any RPM a high amount of boost wll be required. I do not know how much you can get away with before detonation takes the engine away from you.



That is why I would plot the large number of dyno runs and pick a boost figure a bit on the modest side.

A 15 second blast on the dyno is good for big numbers to talk about. If the customer crosses (or attempts to cross) Nevada on a hot day at 100MPH+ will he make it? Will even an aftermarket cooling system be enough.



Well, actually, a low drag car needs less than 150 HP to go 100 MPH, so a higher heat load would be a few runs through the gears back to back.



With an efficency of less than 28% how many BTUs will we need the radiator to reject at XXX HP? What is the radiator rated for rejection wise?



A few weeks back I was in Texas buy some airplane parts, and got a ride in a 93 with big turbos intercooler water and the whole works. It had the biggest tires you can fit under the stock bodywork.



It was wheelspin limited up to 140 MPH. You could only use full throttle near the end of each gear. Otherwise it would start to go sideways. The speedo looked like a tach. When we got the the diner, he locked it up and walked away. It kept running. It shuts itself off when the turbos cool down enough.



So wanting 500 HP is often more fun than owning 500 HP. But not always.



Lynn E. Hanover

incubus_boader

whose motor is this joe? None of your other customers are allowed to make more power then me! Just to add, porting doesnt really change the max torque output of the motor just where it occurs. if they want a low torque band then there sacrificing horsepower due to poor top end volumetric efficency, if they want a high torque band, like my motor, then thell lose street ability due to poor low end volumetric efficency. all porting changes is where the motor has peak volumetric efficenecy, at low rpms a motor needs air velocity not volume, and the oppisite at high rpms, hence why v-tec and six port induction exist! max torque is modified by boost and ignition timing, beacause they change peak cylinder pressure, where the torque occurs is modified by porting, beacause it changes where peak cylinder pressure occurs! hope this helps, though im guessing you already knew this