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

install a v8?



hah, what's the application for the car?

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

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



B

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.

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?

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.

no smartass comment, but:

does he really know what torque and power is?

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

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

joe is he streeting the car? in a track enviroment i never found my self in low rpms, even coming out of corners! at worst i was at 4000 rpms, but my redline was only 6000 in the srt-4. if he wants to track the car, and still wants decent mid range torque id do a basic street port, and t2 exhaust inserts he should still be able to make good low end torque with good tuning. he can make the torque he wants by playing with ignition timing and turbo sizing...whats is he planning for fuel and timing control anyway?

we talked about a turbo 3 rotor for NASA SU class (500bhpish), sprints, with some 3 hour enduros, and we figured we couldnt put enough cooling into a second gen to do it.

A 20b with stock twins will get very close to that figure if he's just worried about the numbers. Attila the fun over at the Rx7 club forum has stock twins on his 20b and makes more torque than hp. I think he dynoed at 390lbs and 350 rwhp with the twins running out of breath in the higher rpm's. If his twins could flow a little more, I don't see why he couldn't reach 400rwhp and more torque than what he originally got.

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.



On a turbo two rotor to gain more low rpm power without killing top end power you simply need to get the turbo spooled as soon a possible WITHOUT sacrificing intake or exhaust flow.



If you look at many dyno plots you will see engines with responsive turbos like the GT35R making 100RWHP at 3,000rpm and engines with laggy turbos making less than 100RWHP at 3,000rpm.



You have chosen the motor and the turbo so on to getting the turbo to spool faster-



1) Increase pressure differential between the engine and exhaust sides of the turbo exhaust wheel. Fit as large diameter and free flowing exhaust from the turbo back as you can fit. Bigger than 3" really does help. You can also use a rich mixture and retarded spark in varying degrees to increase exhaust gas expansion, but you have to monitor EGTs to avoid melting engine and turbo bits if you go to crazy with this. Open your exhaust ports earlier so more gas expansion happens in the exhaust manifold, contour the exhaust ports for flow so less energy is lost exiting the engine. Use a divided exhaust housing and manifold, even a wastegate per runner to avoid exhaust communication at the wastegate (I have found this helps the very low end boost response).



2) Decrease pressure drop in the intake system from the turbo compressor all the way to the engine ports. This is one most people don't think about. A turbo spools at an exponential rate becacuse of the relationship of the boost it makes increasing the exhaust volume that drives it. This means if you can cut down on the boost lost to pressure drop in the intake side it really helps spool the turbo faster. Keep the intercooler pipes as short as possible with as few bends as possible. Gradually increase pipe diameter from compressor outlet diameter to larger throttle body diameter. Spend a lot of time porting the inake manifolds modding the TB or fabricate a better one. Don't go too late closing on the intake ports or the turbo has to fight the compression reversion. Open the intake ports earlier, there are 32 degrees of intake stoke without the port open in stock configuration for emmisions purposes.

WOW, awesome info Blue TII. Thanks so much, that all makes sense to me!

We are building a V-mount intercooler setup so the I/C pipes will be very short.



I was thinking of opening the intake ports as far as possible without going to a bridge port and leaving the closing side stock.

Where would I get 32 degrees of intake stroke from? cutting a bridge port?

Would everyone else agree that the GT35R would be the best turbo for this application?



seanm - dont worry this motor will be quite mild compared to yours https://www.nopistons.com/forums/pub...DIR#>/wink.png

Give him 500 hp and a shorter rear end gear?

porting does raise volumetric efficiency, IF its done right. so yes you do get more tq from porting.

a proper port will loose very little power under 2k rpm if any at all and make more tq over that rpm

turbo or na.

Where would I get 32 degrees of intake stroke from? cutting a bridge port?



You can get the intake to open 10-15 degrees earlier by cutting the opening edge enough that it drops the leading sideseal and keeps the trailing sideseal supported. With this porting it is best to bevel and scissor the closing edge of the port to avoid sideseal damage, so you will have a bit later closing.



It is then possible to get the port to open another 15-20 degrees earlier by beveling the rotor edge toward the sideseal.



Mazda used both these old race tricks to get the Renisis to open intake at 0 deg, but didn't properly bevel and scissor the closing edge.







Would everyone else agree that the GT35R would be the best turbo for this application?



I thought you were asking how to get as much low end as possible with the Cosmo 13B and the GT35R. If the turbo is in question, I would choose a turbo with a larger exhaust wheel (at least P trim) and put it in a small housing to get it to spool. Now that Garret T04 turbos are available w/ dual bearing centers you could choose a wheel combination that is proven to work well on rotary and still get the benifit of ball bearing center. If top end drops off too much you can swap to a larger housing. Make sure you have a large well flowing wastegate set-up and it shouldn't hurt top end power much.

So nobody ever really answered my question:



I want to leave the port closing time stock but then port it to open up as early as possible without going to a Bridge port. Will this work for the goal we have set?



Also as for the turbo, I was thinking of a "P trim" exhaust wheel with a .96 A/R housing ??

as for the turbo, thats about what seths got on his, the dyno is in the dyno section, its over 300lbs ft from 4500 to like 6500 rpms.



his port timing closes later than stock.

Good info in this thread. I'm doing a similar thing but with S5 block a 62-1, .96 a/r. The customer wants 400hp at wheels so I'm concentrating on making the engine as efficient and responsive as possible so its not working too hard to make the power. The car will weigh about 1900lb so power to weight should be good, especially for road use.

So would leaving the port timing close at its stock position, but open earlier help with bottem end power?

im not meaning to think outside the square or anything... but if he wants instant power on the roll on(and i agree that the turbo ideas here are very good) but why not supercharge the bloody thing

admittedly it weighs more, but if he really wants fast response down low(and 500 odd hp) wouldnt a s/c be the most obvious answer? or have i just spent the last few sentances commiting sacralige?



Peace

Psycho_Dad

From my experience, its hard to make a super charger efficient all the way to 8000 rpm. Not saying it isnt possible,







Turbo is more efficient on high reving engines.

I think i got the answer for your customer :P get a V8 . For that kinda power and torque with a low rev limit like 7000 it would be good for his applications.