monster touque

[iamrenn]

Taking things in a different direction, what can be done to maximize torque on a 1UZ engine? It may be that these are not designed for torque but I have an interest in using this engine to drive a propeller for an airboat application. Automotive engine airboaters use reduction units (2:1 to 3:1) to keep propellers below 3000 rpm. The conventional thinking among airboaters tends toward lower rpm, huge cubes and keeping things simple. (carberators) Big torque seems to rule. These fellas undoubtedly know their stuff, I am sure the 600 cube chevys work, but I just want to explore the area outside the box a little.

Renn

 

[Lextreme II]

I think stroking from 4.0 to 5.2L will difinately help along with a root supercharager along with high compression motor.

 

[iamrenn]

Stroke increases torque, cubes increase potential. I am used to focusing on horsepower with torque as only a side note.

What about the other things. Supercharging is like adding cubes, yes? And compression. So parts need to be stronger. How do you maximize gains below 6000 rpm? Keep a stock like cam profile??? Stock manifold??

Also, and airboat engine sits on a stand without a lot of restrictions on space. Routing for turbos/superchargers can be done for maximum efficiency.

I hate carburators so I wont be dropping the fuel injection. Reliability is huge though. If the engine quits only another airboat (or a helicopter) can rescue.

 

[rms]

Stroke increases torque, cubes increase potential. I am used to focusing on horsepower with torque as only a side note.

How do you maximize gains below 6000 rpm?

For the same capacity, torque is not related to stroke.

Torque is related to capacity, if you want more torque - increase the capacity.

 

[Jake Breyck]

long narrow intake runners and longer primaries on the headers help lower end torque.

 

[iamrenn]

I'm open to this, though I have taught to believe what I previously stated.

Help me out. So, you build two engines - both with the same displacement. One 3.440 bore x 3.375 stroke and another 3.750 bore x 3.440 stroke. Same cam, heads - everything.

The torque and bhp curves are the same?

That seems counter intuitive to me.

I just looked up the formula for torque. t=radius x force -- which seems to indicate that you are correct. I have seen examples engines building big torque at lower rpm (usually attributed to stroke). Is it just the cam/airflow/cylinder filling stuff? How do you promote a big wide flat torque curve? And again is the forced induction like adding displacement while retaining similar power curves?

 

[iamrenn]

Last post was a response to rms. Thank you and to Lex and Jake as well.

It seems that other than increasing displacement typical mods are going to push hp up - typically at the expense of torque.

Per Lex's recommendation I need forced induction to make more capacity, rms says strike is just another means of effecting capacity and according to Jake I need to keep the velocities high at lesser rpm. Yes?

Renn

 

[Jake Breyck]

according to Jake I need to keep the velocities high at lesser rpm. Yes?

Renn

yep thats the effect you get. it works in NA and boosted motors the same, so dont need to count it out even if you plan on turbo or supercharging the motor.

 

[Blizzy]

roots blower, long tube headers, slightly undersized exhaust: hello torque

The roots blower will get the engine churning off idle. The long tube headers will bias the powerband toward the low end, and the slightly undersized exhaust will increase exhaust flow efficicency on the low end. These all, in tandem, will produce more grunt at low rpm, where big torque can be made even without extreme power numbers.

 

[iamrenn]

Ok, this is making more sense to me now. It's about efficiency within a range. The fact that the rpms are low limit the horsepower output but the torque#s are good because of air flow efficiency. Sounds like a turbo is a good way to increase torque.

I understand now at least that the engine works well as and for the reasons the oem designed it. - What I wonder now is about how this is affected by the boost. I have no idea how much more air is pushed in by the supercharger/turbo but --- how long do the small, long passages help efficiencies before they then begin to inhibit them. Does the boost warrant an increase in cam/port size? Does the boost increase air flow efficiency across the range without any need to increase?

I seems that stock cams may be fine. Small pipes are fine but with long tubes (turbos like short tubes???).

I will need, other than a blower, components to increase bottom end durability to withstand maximum boost using pump gas. How much boost is that? What components? Pistons, rods and studs?? What do you think the torque and horsepower potentials are?

Thanks for your responses.

Renn

 

[cribbj]

Here's some curves from the Kenne Bell website that illustrate what the earlier posts are saying and they show where the PD supercharger's strong points are.

The PD superchargers such as the Roots and the twinscrew have a boost curve that does wonders for the low end, while the centrifugal supercharger is basically just a belt driven turbocharger, and it has a progressive boost curve which is dependent on engine RPM.

If you want lots of grunt, you may want to oversize the supercharger and/or overdrive a normal size unit, so it's reaching its max RPM at 5000 engine RPM or so. But if you overdrive it, you'll need to be careful that you don't overspeed it.

With an oversized charger, you can get lots of boost down low, and then when you exceed what you want or need, either bleed it off, or put a recycle valve in to control it to what you want, ie Dial-a-Torque. Just be sure you have enough octane to keep the motor together with all that extra torque :fingersx:

Simplistically: Boost = Torque

 

[iamrenn]

thanks cribbj, this is getting more clear. This forum is very helpful.

I think I like the idea of building boost with engine speed. An airboat would benefit little from off idle torque. The prop doesn't do much until 2500 to 3000 rpm. I will have to check that for sure. It might be nice for fuel and wear if cruise speed can be at only moderate boost. Maybe 4 psi at 3500 and full by 5000. Sounds to me like centrifugal might be best. What do you think?

 

[Lextreme II]

My next project would be all lower grunt. 5.2L with M112 high compression build motor.

 

[cribbj]

thanks cribbj, this is getting more clear. This forum is very helpful.

I think I like the idea of building boost with engine speed. An airboat would benefit little from off idle torque. The prop doesn't do much until 2500 to 3000 rpm. I will have to check that for sure. It might be nice for fuel and wear if cruise speed can be at only moderate boost. Maybe 4 psi at 3500 and full by 5000. Sounds to me like centrifugal might be best. What do you think?

I'm certainly no expert on your airboat application, but IIRC, the power requirements of a fan/blower/propellor increase as the 4th power of its speed, so you'll need "lots" more power if you increase the prop speed, yes?

So in this case, perhaps a progressive boosting device like a turbocharger or centrifugal supercharger would be just the thing for you.

 

[Lextreme II]

John,

Like the idea of WG application for the Supercharger. Bleed off certain psi when reached.

 

[iamrenn]

I'm certainly no expert on your airboat application, but IIRC, the power requirements of a fan/blower/propeller increase as the 4th power of its speed, so you'll need "lots" more power if you increase the prop speed, yes?

So in this case, perhaps a progressive boosting device like a turbocharger or centrifugal supercharger would be just the thing for you.

cribbj, you are reminding me that I should have stayed in school a bit longer. You are an engineer yes?? Thanks for that info. I have experienced the diminishing returns thing on the airboat I ride with my neighbor. He has a 572ci Chevy and his boat is nearly 3000 lbs. His cruise speed requires about 4000 rpm. Breaking free from sticky mud in the Great Salt Lake often requires more than full power - 5000 plus rpm. Seven miles from the shore in 1/2" to 6" of water with mud that a person sinks 3" to 12" deep when walking is the reason for needing reliability.

It seems that a power band spanning 3000 to 5500 seems about right.

 

[Lextreme II]

John is one of the Godfathers in here.

 

[Blizzy]

John,

Like the idea of WG application for the Supercharger. Bleed off certain psi when reached.

Check out this article:
http://www.musclemustangfastfords.c...gal_supercharger_wastegate_install/index.html

It is a Saleen Mustang that ran an EBC to a wastegate on the hot side of the intercooler piping with a Centrifugal S/C to limit boost to 15psi while on the streets, even though the pullies are calibrated to 20psi. The boost curves are linear until the gate opens to blow off the excess air.

Personally, the use of a wastegate is the only way to increase boost response while being certain not to outblow your motor or your driving circumstance. The result is the most low-end friendly power curve possible, regarding of the blower type in discussion.

------------

In this discussion, however, a positive displacement blower is the only way to truly get the "monster torque". Check out the PD blowers on those monster trucks: holy smokes!

 

[rms]

Seems like you need to work the numbers back from the prop diameter/pitch/rpm.

Do you have a hp curve v prop rpm? You can then work back to reduction ratio required/engine rpm/engine bhp.
You will be chasing bhp not torque.

If it is an aircraft prop you should be able to get the numbers.

 

[iamrenn]

Blizzy, good article, very informative. I think I will plan to use a centrifical, probably a turbo and use the wastegate as suggested.

rms, the airboat manufacturers sell props in horsepower ranges. They supply composite blades mounted into a aluminum hub. The props are marked so that you can rotate them to vary the pitch and thereby dial the rpm. If you can not achieve full rpm you decrease pitch. Different gear reduction ratios are used to best match the power range of the engine.

here is a link http://www.sensenichprop.com/sen_html/airboat/carbon-faq-5.pdf

thank you all for your input

Renn