Why Our Turbo Cobra's Don't Have Torque

Juiced46

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My point exactly, people who left heads/cam/intake stock made a TON of torque, what was your HP by the way?


So what if the car makes more HP then TQ. Since when is 600-700ftlbs with 15-18#s such a bad thing?? A KB/Whipple wont do that. The only reason KBs and Whipples make more TQ then HP is when the blower is reaching its efficiency limit and it cant make more HP but it will pick up TQ because its being overspun. Look at a KB with 13#s it will make more HP then TQ.

I built a 78mm car .96 ex housing, ported heads/cams and it made 865rwhp 834rwtq on 22psi what is so bad about the TQ? I can see if the TQ was 600ftlbs, then yea there is a problem.


Its just like a pullied eaton car. You slap a 2.76 on it and it will make around 470/470, add a 4# lower, you may gain 10hp but pickup probably another 50 ftlbs because you are past its efficiency. You will see that with a turbo to. The more you lean on it, the more you will see the TQ come up and HP not when you start reaching its limit.
 

Onelfastlride

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After thinking about it some more, I think I was struck by the obvious.

An engine does not make horsepower, it makes torque. Torque is a measurement of force (ability to do work). Horsepower is the measurement of work over time.

· Torque is a twisting force that rotates or turns an object.

· Torque is measured in lb-ft, meaning a force in pounds acting on the end of a lever measured in feet. In our case the length of a length of a rod acted on by the force of a piston. Thus a larger displacement engine can make more torque. Either by rod length or a larger force (piston) pushing down.

· horsepower = (torque x rpm) / 5252

Long story short.....it has to do with at what rpm a particular set up makes peak TQ and how long it carries that TQ through the rpm band. Things like turbo efficency, intake, cams......... all make a difference in shifting the power band up or down.

Take a look at the table below and you will notice the break even point for this table is 5000 - 5500rpm.

If the TQ peaks and falls off before 5500rpm in the table below, it makes more TQ then HP. If it can carry the peak TQ above 5500rpm, it makes more HP then TQ.

RPM TQ HP
2500 800 381
3000 800 457
3500 800 533
4000 800 609
4500 800 685
5000 800 762
5500 800 838
6000 800 914
6500 800 990
7000 800 1066
 
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Silver03Termi

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There are many factors to where you car makes your tq and hp but the biggest factor in a turbo car is of coarse the turbo. When you guys compare hp and tq you really need to see dyno graphs to see why different set ups make different numbers, or at least the rpm when peak tq and hp happen. Silver03Termi, your math is off because those numbers I'm pretty sure do not occur at the same rpm. Which is why rpm is important when comparing hp vs tq.

MY MATH ISNT OFF. ID SEND YOU A CALCULATOR, BUT I ALREADY BROKE THE FORMULA DOWN FOR YOU ON THE POST. THE ALGEBRA SHOULD BE EASY TO FOLLOW. There are only 3 variables in the equation, rpm, torque, and horsepower. 2 of them are given, horsepower and torque, you can use those 2 to solve for the 3rd variable, rpm. Its 8th grade algebra in its easiest form. As far as the 13% torque loss from 4000 to red line, that is just an estimate. Depending on turbo efficiency, you might see less or more.
 

smashedheadcat

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There are many things that can shape your power curve. The stock heads/cams are designed to promote low rpm power at the cost of losing top end power. So it's going to be more biased to creating more power sooner (torque will be higher in lower rpms but lower in upper rpms). Next is the intake. If you use an intake with long runners it will want to build low rpm power but sacrifice peak performance on the top, it's opposite for short runner intakes. The sullivan intake is a shorter runner intake so it is going to do its part in shaping the power curve accordingly. Next is the power adder. Different power adders have their advantages so selection is critical to find a successful combination. For example, the stock 03 cobra uses the following:
low/mid range cams
low/mid range blower
Super short intake runners
Roots/twin screw type blowers are low/mid range blowers but this setup ended up working out great for street and strip. You get the cams and the blower designed to build all kinds of badass power down low and used an intake (super short runner) that can hold the torque curve flat in the upper rpms. All in all, it gave us a nice flat torque curve which pretty much everyone fell in love with.

Look at my twin turbo setup.
Low/mid range cams (stock)
low/mid range intake (unmodified 99-01 cobra)
low/mid range turbos (50mm with small a/r)
---------------------------------------
No rocket science or math required here, odds are I'm going to make more torque than HP, I am going to see a fast spool (full boost by 3100rpms) and power is going to peak at or around 5200-5500 rpms, stay flat for a little bit then fall off rapidly as rpms increase.

Messing with the combo poses some interesting changes. A sullivan intake will shift my power curve to the right. I'm contemplating this change as I have tons of things going for me to support low/mid rpm power and could use the intake to flatten the torque curve (this would reduce my power down low but keep my torque curve from dropping so much at the top).

There are a few variables that can manipulate the powercurve some like timing curves, messing with a/f ratios etc. but the big stuff is the cam(s), cam timing, intake and power adder if used.

Some random setup.
mid/high rpm cams (aftermarket cams)
mid/high rpm intake (sullivan)
mid/high rpm turbo (61mm twins)
----------------------------------
Odds are this is going to sacrifice bottom end power (slow spool) and as rpms increase so does torque, once you get to 4500-5000rpms you start hitting a sweet spot and then big power in the high rpms. More HP than TQ, still fast, just biased in the mid/high rpms. There are tons of things you can do with this setup. Adding an automatic with a loose converter would make for a badass ride.

One more setup. F1a procharger on 03 cobra.
low/mid range cams (stock)
extreme high rpm intake (super short intake runners (stock lower with hat)
mid/high range supercharger (Big centri)
------------------------------------

Cams help build low rpm power but the benefits are severely outweighed by an intake with 2 inch (insanely short) runners. An intake that short makes huge sacrifices down low and should help out in the upper rpms. (this intake should be ideal from 4500-10000 rpms). The supercharger doesn't help things much in the low rpms but should really come alive in the high rpms. So the stock cams' benefits are overshadowed by too much bias in the other direction. Using what we know, we could probably figure out that this setup would make dog shit low rpm power and then really try to bring the power in on at the top. Probably have a torque curve that continues to climb from the low rpms all the way to redline. A very one sided, setup that's poorly thought out. You could fix this by switching blowers to a KB and get a flat curve, or switch to a long runner intake to try to achieve balance.
 

Turbo98

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Messing with the combo poses some interesting changes. A sullivan intake will shift my power curve to the right. I'm contemplating this change as I have tons of things going for me to support low/mid rpm power and could use the intake to flatten the torque curve (this would reduce my power down low but keep my torque curve from dropping so much at the top).
The question is why would you want to do this? Would it make your car any faster? Your set-up is optimized and everything works together very nicely from your numbers that I've seen. The intake is going to be a HUGE factor and may mess up everything working together. Plus, I don't think it would be as much fun on the street.
 

smashedheadcat

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The question is why would you want to do this? Would it make your car any faster? Your set-up is optimized and everything works together very nicely from your numbers that I've seen. The intake is going to be a HUGE factor and may mess up everything working together. Plus, I don't think it would be as much fun on the street.
That's a good question. What I need to do is adjust my powercurve to meet the rpm range that I want the car to perform best in. For one, I make an assload of power below 5000rpms. That's perfect for things like spooling up quickly, building boost on the sct 2-step (which I don't use anymore) and insane "tooling around town" throttle response. If I can shift my power curve up some I will lose some of that power down low and gain some up top. Since I'm rolling with an automatic with a somewhat loose stall converter, my car rarely sees anything less than 4500rpms when I'm playing around or racing (never below 4500). So shifting my curve will really help me where my torque converter can keep my engine in the upper rpms, which right now, is where my torque curve is falling quickly and the horsepower stays steady. If I can shift it some my converter will make the very bottom of the rpm range obsolete and take advantage of the gains I would see on the top end. I'm thinking about doing this or just tightening up the torque converter some to bring the rpms down into the meat of my powerband. I haven't ruled out the option of a bigger exhaust a/r housing either. Tons of options and unfortunately there aren't many setups that can do it all.
 

Turbo98

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I kind of forgot you swapped in the auto. That makes a difference for sure. Sounds like it should work out for you shifting power up one way or the other.
 

kmracer

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Am I wrong in thinking that it has a lot to do with the flow potential of the turbo(s)? A lot of single kits make more torque than twins, but 1-76mm has less flow than 2-57mms (or 61mms, etc). Kinda like adding a 2.76 pulley to your Eaton which already had a 2.93/4#... you are closer to it's "limits", so the HP gains are smaller than the torque gains.

i think it has to do with power band, ie: when the turbos reach full boost, as well as camshaft selection. what you need to do is look at is the rpm peak t occurs, a dyno chart would be even better, but i honestly think that the sooner a turbo reaches full boost, the better peak tq is gonna be.
 

smashedheadcat

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i think it has to do with power band, ie: when the turbos reach full boost, as well as camshaft selection. what you need to do is look at is the rpm peak t occurs, a dyno chart would be even better, but i honestly think that the sooner a turbo reaches full boost, the better peak tq is gonna be.
True statement. Like I tried to explain above, the quicker you get things going the more power you are going to have down low (obviously). The trick is to get things moving down low. You need small turbos and long intake runners to pull this off usually.
 

turbo'd 03

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I'll just state right now that I did not read all the post in this thread. I can only go by setup.
I am not lacking in the Tq department at all. She makes 1010/895 rw. To me that is a A$$ load of Tq. I didn't change my heads or cams. This is not a drag car, just a little street cruiser that is a blast to drive. Depending on what fuel I have in, I can run anywhere from 5psi to 29psi at the push of my eboost.:pepper:
 

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