#21  
Old 10-14-2021, 12:40 AM
pastry_chef's Avatar
pastry_chef pastry_chef is offline
Suspended
 
Join Date: May 2003
Location: Ottawa
Posts: 2,300
Default

Quote:
Originally Posted by i82much View Post
maybe the blue one, since it probably makes more average power over the range of rpms that it will see in street use ...
For sure.

  #22  
Old 10-14-2021, 07:40 AM
PAUL K's Avatar
PAUL K PAUL K is offline
Ultimate Warrior
 
Join Date: Feb 2004
Location: Sugar Grove IL USA
Posts: 6,283
Talking

Quote:
Originally Posted by slowbird View Post
Guys this is the street section not the race section. Racing rpm and hp are king but for a street car (one that actually gets driven a lot with good drive ability) not sure rpm/hp is king. Say you have 4000lb car with 3.42 gears and 3000-3500 stall, which one you taking?
If that's the case I'd move the cam timing around and take the blue one.

__________________
Go fast, see Elvis!
www.facebook.com/PaulKnippensMuscleMotors
  #23  
Old 10-14-2021, 08:50 AM
67Fbird's Avatar
67Fbird 67Fbird is offline
Senior Chief
 
Join Date: Mar 2021
Location: GA
Posts: 465
Default

next up would be a 2800lb street car.....
Now you kinda need to go RED as the BLUE would blow the tires off trying to get it rolling....
It's always "the combination" that makes things work out well. The engine is merely a single PART of that combo. We have all seen awesome XXXX that absolutely runs terrible because the OTHER 25 "parts of the combination were NOT matched up with XXX. Some parts can HIDE a mismatch like..great power...wrong GEAR = still runs pretty good. So i will stick with the "application specific" required before buying either of those engines....

  #24  
Old 10-14-2021, 09:48 AM
RocktimusPryme's Avatar
RocktimusPryme RocktimusPryme is offline
Ultimate Warrior
 
Join Date: Jul 2014
Location: Bedford, IN
Posts: 2,166
Default

As long as it actually still drives well, I think Ill take the extra HP every time.

Ive slowly began to feel that the "torque for the street" theory is antiquated mostly from looking at single plane vs duel plane stuff.

When I am street driving, I am mostly just cruising. Its under 3500 RPM, I am not trying to scare old ladies. Its more important to me that when I do want to put my foot through the floor that ALL of the beans are there.

Now no rules are hard and fast. As mentioned if the math were done and the blue line actually makes more average HP, then thats different. Generally speaking however, give me the power up top for the track. I wont miss 20-30 foot pounds at 2500 RPM. I WILL miss the tenths on the ET if I lose them.

It comes down to tangible vs theoretical for me. The butt dyno is inaccurate at best. Even with spirited street driving, as long as you have enough torque to break the tires loose its kinda all the same. But those ETs on the other hand, they are tangible and accurate. I would rather have that top end to make sure I get those hard numbers. Burnouts all look the same. ET Slips do not.

The other asterisk would be drive quality. Nobody wants a hard starting, snotty cam that wont idle below 1200 RPM and doesnt have enough vacuum for accessories. There is a point of diminishing returns.

__________________
1967 Firebird 462 580hp/590ftlbs
1962 Pontiac Catalina Safari Swapped in Turd of an Olds 455
Owner/Creator Catfish Motorsports
https://www.youtube.com/@CatfishMotorsports
  #25  
Old 10-14-2021, 10:00 AM
pastry_chef's Avatar
pastry_chef pastry_chef is offline
Suspended
 
Join Date: May 2003
Location: Ottawa
Posts: 2,300
Default

Quote:
Originally Posted by RocktimusPryme View Post
As long as it actually still drives well, I think Ill take the extra HP every time.
I love this video.
The original tractor engine made more torque / low RPM power but the new Volvo engine makes more horsepower across RPM range that can be used.
https://www.youtube.com/watch?v=9yHl24QynOM

Maybe he should race his neighbors tractors.


Last edited by pastry_chef; 10-14-2021 at 10:43 AM.
  #26  
Old 10-14-2021, 11:03 AM
Tom Vaught's Avatar
Tom Vaught Tom Vaught is offline
Boost Engineer
 
Join Date: Dec 2001
Location: The United States of America
Posts: 31,294
Default

Simple answer, where does the engine spend most of its time on the street.
Are you a aggressive driver who cares little about F.E. vs a smooth driver
like Jackie Stewart on the street.

Build and Cam the engine for those modes of operation. Drives well is a subjective thing.
Tom V.

__________________
"Engineers do stuff for reasons" Tom Vaught

Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward.
  #27  
Old 10-14-2021, 11:24 AM
george kujanski's Avatar
george kujanski george kujanski is offline
Ultimate Warrior
 
Join Date: Jan 2000
Location: palatine, il. USA
Posts: 7,832
Default

The original question is to choose for street application. As mentioned, HP and torque on these engines is interrelated, and as Tom mentioned, choice is determined by application.

Here's a question: you need to choose an engine to power a 18 wheeler weighing 80,000 pounds. Your choices are 1. CAT 900 cu.in diesel, say 900 ft-lb of torque from idle to 2500 RPM, 450HP, or a GM LS, say 450 ft-lb @5000RPM, 450 HP @ 6500 RPM? (Just shotgunning the numbers but probably close....)

State the reasons for the choice.

George

__________________
"...out to my ol'55, I pulled away slowly, feeling so holy, god knows i was feeling alive"....written by Tom Wait from the Eagles' Live From The Forum
  #28  
Old 10-14-2021, 12:00 PM
i82much's Avatar
i82much i82much is offline
Ultimate Warrior
 
Join Date: Dec 2005
Posts: 2,786
Default

Quote:
Originally Posted by george kujanski View Post
The original question is to choose for street application. As mentioned, HP and torque on these engines is interrelated, and as Tom mentioned, choice is determined by application.

Here's a question: you need to choose an engine to power a 18 wheeler weighing 80,000 pounds. Your choices are 1. CAT 900 cu.in diesel, say 900 ft-lb of torque from idle to 2500 RPM, 450HP, or a GM LS, say 450 ft-lb @5000RPM, 450 HP @ 6500 RPM? (Just shotgunning the numbers but probably close....)

State the reasons for the choice.

George
of course you would choose the diesel. two engines with equal peak power.

that said, a 700 HP LS engine with enough mechanical advantage will accelerate any load, including an 18 wheeler, faster than a 450 HP engine with far more torque. there are many reasons why it is not practical to do so, but power, not torque, is what determines how *quickly* you can do work. and accelerating a vehicle - be it a crotch rocket or a space shuttle - is work.

  #29  
Old 10-14-2021, 12:11 PM
Tom Vaught's Avatar
Tom Vaught Tom Vaught is offline
Boost Engineer
 
Join Date: Dec 2001
Location: The United States of America
Posts: 31,294
Default

If you are not changing rear axle ratios, trans ratios (except by manually locking a trans in a given automatic gear), then engine rpm and if the engine is happy at those rpm points, gives you the answer WITHOUT a lot of math or opinions.

Choosing a dyno curve without real world vehicle information (engine installed) in that vehicle and road tested is purely bench racing and a waste of time.

Tom V.

__________________
"Engineers do stuff for reasons" Tom Vaught

Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward.
  #30  
Old 10-14-2021, 01:59 PM
pastry_chef's Avatar
pastry_chef pastry_chef is offline
Suspended
 
Join Date: May 2003
Location: Ottawa
Posts: 2,300
Default

Quote:
Originally Posted by i82much View Post
power, not torque, is what determines how *quickly* you can do work. and accelerating a vehicle - be it a crotch rocket or a space shuttle - is work.
Yes.
formula is.
pounds of force to the tire now = (horsepower now x 375) / MPH now.

Not factoring for aero or rolling resistance.

----

900 ft-lbs of torque sounds like a big number to some, in context it is not. I can do that with my hands and a sturdy length of pipe.
I doubt any human could generate even just 5 HP, most not even 2 HP.

Horsepower is what puts thousands of pounds of force to the tires. High horsepower launches 10,000 pound monster trucks over many cars.

  #31  
Old 10-14-2021, 02:54 PM
i82much's Avatar
i82much i82much is offline
Ultimate Warrior
 
Join Date: Dec 2005
Posts: 2,786
Default

I think one way to look at it is this. The peak HP rating doesn't tell you the full story of how much work you can accomplish in a given amount of time with a given engine in a given car, because the engine doesn't spend the whole time at the HP peak. The peak torque number is just another data point that gives you some idea of what the power curve looks like, and thus provides some insight into the "area under the curve" that a given engine will provide in a given car.

in a heavy car with highway gears and a tight converter, the engine will tend to operate at lower RPMs. as a consequence, the data point for the peak torque number is more important than for a lighter car with gear and looser converter that spends less time at lower RPMs.

in either case you are trying to optimize average power.

  #32  
Old 10-14-2021, 07:00 PM
turbo69bird's Avatar
turbo69bird turbo69bird is offline
Ultimate Warrior
 
Join Date: Feb 2005
Posts: 1,421
Default

Quote:
Originally Posted by Tom Vaught View Post
Simple answer, where does the engine spend most of its time on the street.
Are you a aggressive driver who cares little about F.E. vs a smooth driver
like Jackie Stewart on the street.

Build and Cam the engine for those modes of operation. Drives well is a subjective thing.
Tom V.
This is what I’d do too.
Usually I go for a long broad torque curve but that’s because it usually suits the engines power band with a Pontiac even in drag racing.

But occasionally a perky HP engine is what’s needed for certain applications say a light weight speed boat that spends a lot of its time at max rpm and HP

__________________
Happiness is just a turbocharger away!
960 HP @ 11 psi, 9.70 at 146.
Iron heads, iron stock 2 bolt block , stock crank, 9 years haven't even changed a spark plug!
selling turbos and turbo related parts since 2005!
  #33  
Old 10-18-2021, 01:27 PM
jonmachota78's Avatar
jonmachota78 jonmachota78 is offline
Ultimate Warrior
 
Join Date: May 2007
Location: Salisbury, IL
Posts: 1,391
Default

Is this the OF/dual plane vs Road Paver/single plane thread?

__________________
'78 Macho T/A DKM#95, 460cid, SRP pistons, KRE 310 D ports,
3" pypes, Hooker 1 3/4" headers, hydraulic roller,
10" Continental, 3.42 gears
11.5 @117.5mph 3900lbs
([_|_] ##\|/##[_|_])
  #34  
Old 10-18-2021, 01:39 PM
slowbird's Avatar
slowbird slowbird is offline
Ultimate Warrior
 
Join Date: Jan 2001
Location: Montgomery, IL
Posts: 10,638
Default

Quote:
Originally Posted by jonmachota78 View Post
Is this the OF/dual plane vs Road Paver/single plane thread?
No.

  #35  
Old 10-20-2021, 10:59 AM
Pontiac Derek Pontiac Derek is offline
Senior Chief
 
Join Date: Sep 2009
Location: portland or.
Posts: 328
Default

Easy, when I was 16 I'd want that red line now that I'm almost 40 I take the blue line LOL

__________________
Build it Right Build it Once!!!
Just another Engine Builder from the Northwest lol
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 04:40 AM.

 

About Us

The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.

 




Copyright © 2017