engineermike

Just found this on a Comp car:

"8.905 @ 167.24 mph. I have 2.22 seconds of throttle stop on so i don't break out. I am running a rail at 1191 pounds, a 226 CI Buick V6, a custom Glide with a 5000 and a 5:38 gear."

1racerdude

Don't need lessons about racing,probably been doing it longer than ya are old.
We are talking LT-1 here with a 7000RPM limit.
I build engines in my little hole in the wall shop and have a real good idea how they work and preform,in a streight line or turning left and coming back the other way.

They rev um to MAKE HP and torque and if ya choose to raise the band then ya will need lot's of gear.Try running a 5.13 or lower in some of the builds on the board and see if ya run out of rev's.

engineermike

My whole point is that gear and converter will fix soggy low-end, and that the adage that "torque wins races" is totally incorrect.

Now that you've narrowed it down to an LT1 car with the stock ECM, let's do some calc's.

I'll assume a healthy all-motor set-up, making 575 fwhp, in a 3400 lb car. That would run right at 130 mph in the quarter.

Now, I've run my stock-computer LT1 to 7200 on the dyno, so I'll assume that's the rpm limit.

Assuming no slip in the clutch and a 28" tall tire, 7200 rpm equates to a 4.61 gear, so you would probably be fine with a 4.56, which won't require much engine torque at all to get the car moving.

Now, let's assume you have an auto with a converter with 10% slip. Factoring that in yields a 4.15 gear, so 4.11's with the auto would work well. Get a properly matched converter with a high STR and I'm sure it would run well in the quarter.

It's kind of bizarre that I'm making this arguement, though. I have a turbocharged 383, which is a torque monster, coupled with a 2800 converter an 2.73 gears. It runs quite well.

1racerdude

My whole point is that gear and converter will fix soggy low-end, and that the adage that "torque wins races" is totally incorrect.

I never said torque wins races,I said "TQ gets it moving and HP takes it out the back door"there IS NO assumption about that,it's fact.Ya can rave about your gear and converter, but these guys don't want to run a 4-4500 stall on the street

The "torque wins races"statement should be taken up with Joe O not me,for he is the one said to have made that statement.

Boy ya do a lot of assuming.

O try running that gear(513) and converter(4-4500) on the street.
Like I said don't need any lessons.

engineermike

Still disagree, but I've already posted my rebuttal, so I won't beat that dead horse. (221 cid N/A rail running 8's)

I really don't care who said it. If it's a broad statement that's taken out of context, I'm going to disagree with it.

Yes, well, it's kind of hard to do calculations if you don't do some assuming. You'd have a non-existent, mass-less, power-less, tire-less, transmission-less car.

No arguement from me here! Like I said, my personal car is a torque-pig with 2.73's and a 2800 converter. But I can just as easily get beat by a small-motor, N/A car with a 5000 stall and 5.13's with a WHOLE LOT less torque, like Joe Overton's personal car, for instance. Just because I didn't choose that route due to personal taste and streetability doesn't mean they aren't fast.

Sorry. . . didn't realize you knew everything. . .

1racerdude

Bet Joe aint running a 2.73 gear and he don't drive it on the street.

Sounds like your car has a severe chassis problem if ya are running that tall of a gear.If ya could hook it a gear change would make it a lot quicker or stand it on the bumper.Torque ya know.

Ya can disagree all ya want,"torque gets it moving,HP takes it out the back door".

Don't know everything.Learn stuff every day,but can't learn from people that don't know.

All those assumptions are just that,assumptions.Don't feel ya have tried all combo's.Neither have I but I pretty well know what works and stick with it.

Dude,math is "fact" not assumptions.

Kraest

The LT1/LT4 is a great design. No need to **** money away. If you're going to spend $1500 on a new intake manifold/fuel rails, etc, you might as well keep the LT1 intake manifold and get the heads done by AI. They have a car running a medium-sized very streetable solid-roller cam 383 with ported LT1 heads, ported LT1 intake, 4.30 gear, 4500 stall, full interior car running low low 10s @ 130+ on motor.

**** an aftermarket intake manifold, especially when you have to trade high rpm horsepower for low-end torque.

Mike

engineermike

I see we're not going to just let this die. . .

Dude, that's my point. Joe, with his naturally aspirated, relatively small displacement motor, needs alot of gear and converter to make up for the lack of low-end torque. I have plenty of torque.

Do the math. For chrissake let's not call these assumptions. . . my car: 1000 hp and 3750 lb = 150 mph. 6200 rpm redline and 10% converter slip with a 25.5" tire. That yields a 2.82 gear requirement, so I think my 2.73's are close enough.

[sarcastic]Yes, I bet the naturally aspirated, 221 cid rail with 550 hp makes tons of torque. . . [/sarcastic]

Are you calling me ignorant?

I don't think you have to tell me about "math". Engineering is the application of math to mechanical problems. Any time you do that, ASSUMPTIONS MUST BE MADE. I do it every day. The calculations I did were based on a hypothetical 3400 lb 575 hp car and yielded its optimum gearing. Do you like the word "hypothetical" rather than "assumptions"?

Mike

1racerdude

Ya multiply torque with the gears ya know. Don't need math lessons either.

"hypothetical" is not real world and neither are assumptions.

Try 281CID with a Vortec runs 8.96-9.10 made 1062FWHP on the dyno shifting at 9200RPM's and had enough TQ to stand it on the bumper.Ran a 4.88 gear and a glide weighed 2932LBS with driver--fastest Mod Motor door slammer on the planet. It made plenty of both so don't tell me about ya little motors.I wrenched on the car and it had stock suspension location points.


ALL I'm gonna say about this subject....

Alvin@pcmforless.com

Is this over yet

engineermike

Helllloooo!!!!! That's my point exactly!!! If a motor is down on torque, you gear it up, and the axle sees more torque!

I give up on trying to explain this to you. You clearly have no idea what an assumption or hypothetical combination is, or what it's used for. Maybe if I call it a "mathematical model", you'll be happy. Oh, but I'm sure you'll say that's totally invalid also. . . Do you at least agree that a 3400 lb F-body with a 575 hp motor, shifting at 7200, with a 28" tire and a 6-speed will be optimally geared with 4.56's to run 130 mph??? If so, then you agree with my mathematical, hypothetical assumptions.

OMG, why don't you just come out and agree with me. . . A 281 with forced induction is not short on torque. A naturally aspirated 221 cid 550 hp motor is short on torque. Somehow, the 221 runs in the 8's also on a throttle stop, though.

arnie

Guys, guys, you're acting like a couple of... like a couple of stubborn 'Arnies'. Geez, anyway.

There have been HP/torque discussions here in the past. If you have been a member for any length of time, you are aware of those threads, unless you live under a rock.

In a nutshell, I basically agree with Larry. Torque is what turns the tires. Without it, you stuck on the starting line. How many ways you have at your disposal, to generate that torque, will depend on the RPM range of the engine. It ALSO has been stated, it is HP, not torque than wins races. AFAIC, it takes torque, but with RPM to finish the race. Those rigs that haul cement building blocks generate huge amounts of torque. Would that torque win races? Not with their 2500 (guessing here) RPM limit you will. Even though I TECHNICALLY disagree, it is difficult to state the HP supporters are incorrect, as HP is in fact, a product of torque and RPM. So, if you agree that it takes torque with a respectable RPM range, you may very well be stating HP.

Alvin, thot I'd bring this thread to the top, so it is probably NOT over yet. Just doin' my part.
As one person would agree, I must think I know EVERYTHING.

:scratching head: Wasn't this a thread about intake manifolds?

engineermike

Hmmm. . . how is it possible that you agree with Larry, I agree with most of your post, yet I don't agree with Larry???

Obvisously, you have to produce torque in order to make horsepower. Conversely, if you have hp, you are producing some amount of torque. However, this debate, as I see it, is based on which is quicker; a low-torque high-hp combo or a high-torque low-hp combination. I'm saying that the low-torque high-hp combo will win every time if geared properly EVEN THOUGH people generalize and say that "torque wins races" or "torque gets the car moving". An example is that an LS6 can be geared to deliver the same amount of torque to the axle that a Duramax diesel truck has. A Duramax diesel, however, can not be geared to produce the same amount of hp that an LS6 has. The bottom line is: Torque can be multiplied with gearing, whereas Horsepower can not.

When choosing manifolds, if you get the one that makes the most hp, then gear/converter the car accordingly, it will be faster like that.

Mike

arnie

Specifically, you are referring to the RPM capabilty of the engine, which is one of the inputs to generate that HP? As for below.... Personally, I want a manifold that makes the most torque, over the broadest RPM range. A broad flat torque curve will generate a desireable HP curve, that must keep climbing. My priority is not on a manifold that makes humungous HP in a narrow RPM band, ESPECIALLY if the engine will be operated outside of that narrow RPM range. Give me a mountain at a 10,000 ft. elevation, that I can build a 10 unit complex on, not one at 14,000 ft. that I've barely enuf room for a fancy crap house.

Cam tuning is similar. I'll sacrifice a LITTLE high RPM HP, for more over a broader RPM range. Header tuning is another. I wouldn't establish my collector length based on my peak dyno HP. Peak HP #s, are like peak head flow #s, they are for advertising.

engineermike

My point here is. . . if you have 300 hp going into the transmission, there is also 300 hp coming out of the driveshaft, and 300 hp in the axle. The speed of each shaft is slower, but the hp is the same. However, if there is 300 ft-lb going into the transmission, there could be 900 ft-lb in the driveshaft, and 2700 ft-lb in the axle. Each step reduces rpm and increases torque, so the hp stays the same. Want more torque to the axle? Put more gear in it.

Now, we're getting into the finer points. . . There's a local carbureted twin turbo camaro that runs in the 8.80 range. When he leaves on the trans-brake, the converter stalls to 6500 rpm and he shifts at 7200. It doesn't really matter what the motor does below 6500. However, that 700 rpm range is critical. So, in that case, he wants as much hp as he can get in a very narrow range. Any car can be set up like that (though it's not very streetable). Now, if you're talking about a broad torque curve over that narrow rpm range, then I agree with you.

Conversely, if you're stuck with a 2200 rpm converter in a heavy vehicle with 2.73 gears for whatever reason, then I'd agree that a very broad, torque-intensive engine would work best. That engine might have to operate over a 4000 rpm range rather than only 700 rpm.

Mike