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Having lurked around for a while, I've observed many HP/TQ figures for all kinds of Supras, BPU to APU. This question probably stems from my general lack of knowledge, mathematically, how the 2JZ-GTE and its market of stock/aftermarket turbochargers react to the engine the way they do. But anyway, I'm noticing TQ is easily built up to BPU, BPU+, etc. etc., but when you hit APU, massive HP starts coming, yet the TQ kinda slows down. :-\ Most domestics I've seen have bigger TQ amounts, so I'm guessing it's based on engine size? Stupid question, I know, but we were all stupid once, aye?

THNX
 
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2JZGTE4LIFE said:
Having lurked around for a while, I've observed many HP/TQ figures for all kinds of Supras, BPU to APU. This question probably stems from my general lack of knowledge, mathematically, how the 2JZ-GTE and its market of stock/aftermarket turbochargers react to the engine the way they do. But anyway, I'm noticing TQ is easily built up to BPU, BPU+, etc. etc., but when you hit APU, massive HP starts coming, yet the TQ kinda slows down. :-\ Most domestics I've seen have bigger TQ amounts, so I'm guessing it's based on engine size? Stupid question, I know, but we were all stupid once, aye?

THNX
Let me try to be the 1st person to answer this one, I think its b/c ratio of size turbo and size of engine. Supra using a 3.0L will make huge amount's of hp but low tq, mean while domestic's are running bigger engine's 3.0L+, and making huge tq #'s with less hp.

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This is completely incorrect. HP is just the product of torque and RPM. Large engines move more air, so they make more power AND torque. An engine with poor-flowing heads and cams (like those of many 2-valve motors) can't sustain their volumetric effeciency (ie torque) to high RPMs, so they cannot make a lot of HP, and their torque peaks early.

2JZGTE4LIFE,
The reason BPU cars (especially TTC) produce more torque/hp than singles, is because the stock POS turbos aren't capable of high flow effeciently, and most times can't even hold 18 psi to redline. As airflow increases, the turbos becomes less effecient, so HP drops slightly as RPMs raise. A BPU car will get peak HP well before redline, while a single can easily produce peak HP @ redline (or sooner, depending on the turbo).
 
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Excellent post Grant. Torque is all about what I call "effective displacement". You will find most APU cars can make much higher HP at similiar to BPU torque levels. That is simply because they make the torque later in the rpm band, allowing them to utilize gearing to a greater advantage. Make no mistake, the higher HP car is faster, if the driver knows how to take advantage of it.

You will hear a million analogies of torque vs. hp - all I can say is that HP is more directly related to how fast your car is.
 

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I saw a dyno from a T-61 w/.81 exhuast housing that made 620+ RWHP and 620+ RWTQ. I have also seen dynos of larger turbos with 650+RWHP but maybe 500+RWTQ. It's a matter of good tuning and selecting the right size turbo/exhaust housing for what you need.
 

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Mathmatically torque = (5252 x HP)/ RPM

So you see that as you go higher in the RPM range you divide by a much larger number. (example 4000RPM compared to 5000RPM)

A car making 500rwtq at 6000RPM is much more powerful than a car making 500rwtq at 4000RPM.

Since large turbos don't reach full spool/boost until high in the RPM range they miss the opportunity to put down high torque numbers at the sweet spot (3500rpm to 4500rpm) for posting huge torque numbers.

Large displacement engines have low rpm limits because they have much more mass that has to change direction at every stroke of the engine. Piston speed is (inches of stroke x RPM) / 6.
The speed variable for calculating the stress on the rod is squared thus small increases in speed causes huge increases in stress for their heavier parts. So big displacement engines run low rev limits thus it's rare that you will be able to compare a large displacement engine at 7000rpm. If you could compare the big turbos to the large displacement engines 5000rpm to 7000rpm you'd see the the torque numbers would likely be better for the smaller boosted engine.

Yes I'm finally getting to the point......Since large displacement engines make their torque numbers in the sweet spot (3500RPM to 4500RPM) and large turbos don't fully spool until after the sweet spot its unfair to make a peak torque comparison and say there's no replacement for displacement.

Also when it comes to which car is faster you must keep in mind that high RPM engines allow you to install better trans gear and rear axle ratios which multiply the actual torque force being applied to move the car. That's why a wimpy 120ftlb honda with a 9000rpm rev limit can keep up with a 6000rpm rev limit 230ftlb V6. The high rpm limit allows for better gear ratios in the trans and rear axle. That's why low torque Indy engines with 18000rpm rev limits would smoke a 600rwhp 600rwtq Viper from a roll if the car weights were equal. The gearing allowed by the 18000rpm limit makes up for the low peak torque value which is one reason why the pros race using high RPM low displacement engines.
 

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One more thing.....the tubo efficiency does not decrease with RPM.

As rpm increases air is input and output at a higher flow rate. Turbos work off of the flow rate exiting the engine. Higher flow to turbo means faster spinning turbo which means turbo blows more air ino the engine which starts the increasing cyle again at the new flow rate.

A good analogy on why turbos cannot hold a high psi at redline is this. If you turn your sink faucet on full (symbolizimg max flow for a small turbo) and you partially cover the drain the sink will fill up to the level you desire. The drain is the rate at which the engine consumes air flow. So at this point your faucet/turbo can supply more than what the drain/engine needs. There is a certain point of uncovering the drain where the drain flows water at the same rate as your faucet. If you uncover the drain further the faucet flow cannot keep up with the flow at the drain thus the water level starts to go down which symbolizes boost falling off.

The 3liter engine at 5000rpm requires a smaller air flow rate into theengine than at redline. If heengine ingests air faster than the turbo can flow the air the boost drops. Note that at highr boost levels the engine consumes more air at a given rpm.

Sorry for all the typos but I have a baby in one arm.
 

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the reason you they dont have hgih tq like the hp is cause the lower compression. if you run the same setup on say a na supra with a sinlge turbo it will have 5000 and about500ft lbs tq. plus you sould change the ratio gears for more torque~Xdreamer
 
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another reason with upgraded turbos is because of cams. in my experience adding cams makes less torque but more horsepower. just a thought.
 
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meggleto said:
Mathmatically torque = (5252 x HP)/ RPM

So you see that as you go higher in the RPM range you divide by a much larger number. (example 4000RPM compared to 5000RPM)

A car making 500rwtq at 6000RPM is much more powerful than a car making 500rwtq at 4000RPM.
Going the other way with this, a car that can hold a given torque number higher in the RPM range will make a proportionally higher HP number. This is how a Honda engine making 130 Ft/Lbs of torque can make 200+ HP... at 8000 RPM... and it doesn't have enough pull to peel the skin off a grape unless you're at 8000 RPM

Someone older, wiser and sneakier than all of up put together said this... "Horsepower sells cars, Torque wins races". I choose to believe him, if you want to argue the point you will need to shoot yourself in the head because he died about a year ago.

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DuCeY DuCe said:
another reason with upgraded turbos is because of cams. in my experience adding cams makes less torque but more horsepower. just a thought.
This just goes back to the same principles meggleto explained. Cams are instaleed fro more power in the higher rpms. As you can read in the previous posts, this results in higher hp but less peak tq.
 
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Someone older, wiser and sneakier than all of up put together said this... "Horsepower sells cars, Torque wins races". I choose to believe him, if you want to argue the point you will need to shoot yourself in the head because he died about a year ago.
Hey, there's other ways! Jumping off a bridge for instance, or Miss Cleo.

I think it's an unfortunate quote from Shelby. Rednecks have rallied behind it as validation for their lack of understanding of basic mechanics. I hear the Mullet Militia has a Dodge Cummins turbo diesel engine that makes 1000 ft/lbs to the wheels that they are entering in F1. It'll be a bloodbath for all those other torqueless wonders...
 
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Walser said:


Hey, there's other ways! Jumping off a bridge for instance, or Miss Cleo.
Does the prison system allow for psychic readings during visits?

Rob_O
 
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I think I'll go put one of those 14 liter cat in my 3ton pickup so I can run 9's, since it make almost 2k lb ft/tq at the crank :rolleyes:
 
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