How much power is actually needed?

[vega]

Yea, I am aware of the can of worms I just opened here. Please bare with me here.

 

How much power is actually needed to achieve a flat 11 quarter mile time (estimated of course, perfect conditions bla bla bla);

1. in a 280z, factory interior (not stripped) just a front and rear park bench removal (bumpers)

 

2. keeping the 3.54 factory r200.

 

3. using a small block chev (i am in the build of a 327 for mine right now)

 

4. using a 4 spd 700r4 detente cable transmission (factory 700r4 gear ratios)

 

what kind of tq and hp (at the fly not at the wheels) would be needed to achieve this? by that matter new corvettes and other cars are hitting that 11 flat(or damn near it) on NON drag radial tires, what width tire would one need with that power output and the above guidelines?

 

I am asking this because I know how fast I would like my car to be when all said and done, and I don't really want to over build it. I am aware that power is addictive bla bla bla, you will always want more bla bla bla. That is not so much the case for me. I have been in 8, and 9 second cars, no thank you. I think it takes the fun away a little bit. This is just my opinion and I am aware many other disagree with that. I would be overjoyed with a low 11 second fairlady.

 

Thank you for the input in advance!

Vega~

Edited February 5, 2012 by vega

[rejracer]

Click me for answer

[Gollum]

280z without stock bumpers and full interior = roughly 2600 lbs. There's no reason you couldn't get lower, just time, energy, and money. Fiberglass hood is a good example of easy weight removal.

 

So with that figure, your weight added, and that link above you should be set...

 

Regarding tire, I'd recommend at least 245 but wider would require flares or serious attention to fitment. 275 is able to fit in the rear if your suspension and rim package are perfect and you roll the fender. 245 if fine IMO though.just means you have to be a little more careful.

Edited February 5, 2012 by Gollum

[RebekahsZ]

Think about running at an 1/8 mile track. I used to do 11 seconds all day long with a worn out 240z, all stock. (Just a joke for all the non-hybrid folks). Traction may be a problem. Why are you against a drag radial-some sort of racing classification or street racing issue? Drag radials are not much more expensive than good street tires and they totally rock, especially if you don't have an LSD. Not trying to totally thread jump you, but tires can really make a big difference in terms of getting the power that you make to the ground-cheapest power adder you can buy. Good luck with it.

Edited February 5, 2012 by RebekahsZ

[vega]

I work for bridgestone firestone its not about cost- its about class- i can use re-11 tires.

[vega]

Those calculators don't factor in what rpm the power comes in, they don't factor in tq, they don't factor in gear ratios. et calculators are boloney.

 

I guess I would like to know the guys with v8s in the 11s without drag radials what kind size tire and how much power are they making.

Edited February 5, 2012 by vega

[BLOZ UP]

They don't have to. Knowing a car of X pounds goes however many feet in Y seconds requires, at a minimum, Z average horsepower (or integral, or whatever). It does assume perfect traction, etc. So it's a kind of best case scenario. Unless they give some kind of humanizing offset built in to the calculators. I wouldn't be surprised.

[Pyro]

A 11second flat 1/4 mile will take 120 to 130 mph trap speed (depending on traction).

 

A Z with street tires and stock rear end will have bad traction

 

So, plan on going 130hp in the 1/4 mile. That will take 620hp at the crank with a 3000 pound car.

 

I would build a 400hp 327 and add a 200hp shot of n02. Will be tough to make 620hp with a 327 with no power adders.

 

If the traction is good then all you need is 485hp to make 120mph in a 3000 pound car.(total weight). This can be made with a 327 but more gear would be required (3.90 or 4.11).

 

I found the stock 1/2 shafts and axles start to break at mid 11's, 120 mph range.

[Michael]

The trouble with Hp-weight-mph calculators is that they assume constant-power applied during the entire run, and then multiply by a fudge factor in attempt to account for aerodynamic drag, slippage, gear shifts and so forth. For a pro car with a pro driver, these assumptions are reasonable and the fudge factor is stable. But for an all-purpose car (street car, road-race car, and part-time drag car) the assumptions break down.

 

I recall some advice from Marlin Davis, the tech-guru at Hot Rod Magazine, on much the same question. He said, if I remember correctly: for an amateur car intended to achieve a speed in the 10-second to 12-second range, go ahead and use the calculators, but calculate an Hp figure for a car that would be 1-second faster. In other words, if your goal is 11.00 seconds, then look up the Hp number for 10.00 seconds, given the estimated weight, and use that value for required Hp.

 

My Z weighs in the neighborhood of 2600 lbs (completely stripped, lots of stock sheet metal removed, but heavy mild-steel roll cage and big block (aluminum heads etc.). It makes maybe 400 hp in present state of tune, but would be lucky to run 14s with the present suspension, tires, transmission etc.

[vega]

A 11second flat 1/4 mile will take 120 to 130 mph trap speed (depending on traction).

 

A Z with street tires and stock rear end will have bad traction

 

So, plan on going 130hp in the 1/4 mile. That will take 620hp at the crank with a 3000 pound car.

 

I would build a 400hp 327 and add a 200hp shot of n02. Will be tough to make 620hp with a 327 with no power adders.

 

If the traction is good then all you need is 485hp to make 120mph in a 3000 pound car.(total weight). This can be made with a 327 but more gear would be required (3.90 or 4.11).

 

I found the stock 1/2 shafts and axles start to break at mid 11's, 120 mph range.

 

I am not too familiar with n02 with a 200 shot like that could I run a bigger intake port on the heads like a 195cc port vs a natural aspirated application would be best to run a 180cc? Also what kind of compression are we talking about for something like that? could I still run 10.5:1 compression on 93 octane with a 200 shot- or do I have to run a something lower like a boosted application? I am eventually going to drop a Wipple charger on the sbc. I will be running itbs and a custom grind flat tappet cam 110lsa, 110icl, 236intake, 247exhaust, not sure on the lift yet it will depends on what heads do on the flow bench.

[vega]

I am also not so sure that 620 fly hp is needed to take this down the track at an 11, look at the new zr1

 

http://www.corvettemuseum.org/specs/2009zr1/index.shtml

 

http://www.motortrend.com/roadtests/coupes/1011_2011_chevrolet_corvette_zr1_2010_porsche_911_turbo_comparison/viewall.html

 

http://www.dragtimes.com/Chevrolet-Corvette-ZR1-Timeslip-19701.html

 

620hp, and some pretty damn steep gears. 3.4 rear end, 11.5 on 335 sticky street tires (ps2)with crappy magazine drivers. A 10.7 with stock ps2s, and a guy not afraid to really drive it.

 

I don't think a lighter car like the z (by at least 340 pounds)really needs 620hp.

 

Does anyone have more real numbers?

[vega]

with an 18% drive train loss this guy would have 540hp at the fly (claim of 442whp)

 

http://www.dragtimes.com/Datsun-280-ZX-Timeslip-21234.html

he is at 3080lbs with driver

and only 235 MT ET Streets that is kind of small to me.

 

this is on crappy conti tires (different car)

 

I really don't think 620 is needed.

Edited February 6, 2012 by vega

[rsicard]

With a 327, you are going to need a REALLY GOOD power adder. It is doubtful that 11 sec 1/4 mile will be achieved. Everything will have to be right on the money. Lightweight 2618 forged pistons, lightweight con rods and crankshaft. Best cylinder heads available. The right amount of machining of the block. The block itself may be the weakest item in the bunch. The induction system will need to be top rate. Ignition and induction tuning will need to be optimum. Experienced racers would have difficulty achieving the 11 sec goal.

[vega]

With a 327, you are going to need a REALLY GOOD power adder. It is doubtful that 11 sec 1/4 mile will be achieved. Everything will have to be right on the money. Lightweight 2618 forged pistons, lightweight con rods and crankshaft. Best cylinder heads available. The right amount of machining of the block. The block itself may be the weakest item in the bunch. The induction system will need to be top rate. Ignition and induction tuning will need to be optimum. Experienced racers would have difficulty achieving the 11 sec goal.

 

Based on what? 327s don't NEED to spin so damn high to make that much power. Its about picking the right part. I personally am not a huge fan of no2. Hence my lack in experience in it. Mine is 40 over small journal forged crank I am having a custom itb efi setup made for it that is designed to be from 3500 to 7500rpm, the is made for a about 22-6800rpm. That really isn't all that high to me.

 

http://www.chevyhiperformance.com/tech/engines_drivetrain/shortblock/0811chp_327_small_block_chevy_engine_build/viewall.html

 

553hp fly at 7100rpm is nothing to spit at. With a better intake system (and far better cam choice) like I am running with EFI not carb, I would have no problem making power.

 

Calling the 327 a difficult motor to pull a time with is not a informed answer at all, one just has to know what part combination is needed.

 

The validity of a 327 is not what this topic is about, can we please stay on topic.

Edited February 6, 2012 by vega

[Michael]

The fellow at in the link [http://www.dragtimes...slip-21234.html] is making his Hp numbers with 415 cubic inches, aftermarket heads and relatively sophisticated engine management, intake and exhaust. That engine has nearly a 1.5L displacement advantage over the 327.

 

The point is not to disparage the 327 or to insinuate that the displacement is too small to be useful. That is not the case. Rather, the point is that more cubic inches offers a route that's likely to be simpler. Not guaranteed to be simpler, but widely regarded as likely.

 

Alternatively, how about an incremental approach... shoot for a reliable car with no power-adders that comfortably runs 13.0 without breaking parts or displaying any ill manners. Establish that as a baseline. Then incrementally improve, experimenting with exhaust mods, cylinder head porting, and so forth. The advantage is the gaining of experience with a running vehicle, and the testament of personal evidence for what does and does not work.

[Jasonmreiss]

It seems really funny to me that most people only see two type of engine 'animals' ...the American muscle, and the 'tuner' , however it's all the same, v8 guys 'like me' just don't think they need to tune because they already have a good stock hp. Apply the same tuning tricks to any motor and you'll have a monster

[vega]

It seems really funny to me that most people only see two type of engine 'animals' ...the American muscle, and the 'tuner' , however it's all the same, v8 guys 'like me' just don't think they need to tune because they already have a good stock hp. Apply the same tuning tricks to any motor and you'll have a monster

 

exactly.

[vega]

Displacement is not everything, and I am simply not going to get into an argument about that. My sir II b16a is making 170fhp that is 98 cubic inches that equates to 1.73hp/ci. Your argument is flawed- its not just pure displacement that makes power. If the stroke is too long it can't spin rpm without issue (think piston speed). If the piston is too big- it becomes too heavy. More displacement by number of cylinders is the ONLY advantage displacement has. 4.4 v12 will make way more power than a 4.4 v8 sbc and it will be balanced naturally because of the firing order. There is way more to get into that discussion for a different thread.

 

V8 z guys in 11s what kind of power are you seeing?

[Gollum]

I've build/rebuilt/worked on a couple of 150+whp B16's and a 500+hp B16 (on nos) and can attest that it's amazing what the RIGHT parts can do. It's not just throwing parts at a motor sometimes, but choosing the right parts for the application.

 

I personally don't feel you need 620hp to get to flat 11's, but that's just me. I also think you can get under 3,000lbs including driver, unless you're 400lbs yourself. Light bumpers, fiberglass hood, and careful attention to othre weighty bits can really trim down a 280Z. With all that time and energy you're looking at putting into the motor I'd suggest looking into the rest of the car as well.

 

 

I have a feeling you might have a hard time getting all the guys in the low 11's to chime in because many of them don't spend their time checking out every thread. That said, many of them have quite a bit of information posted on the forums to be found...

 

All that said, my across the internet edumacated guestimate is that you only need about 475whp to reach a solid flat 11 on street tires. But that's my guess. What really matters is your guess, your wallet, and your time.

[rejracer]

Sorry for the lack of detail. HP calculators don't consider a lot of factors. Since you are running an automatic, are you going to run a stock size converter or go to a newer 8 or 9" unit. The smaller converters really smooth out the power application and allow you to run more power on a given drive train, but more importantly they lay the power down to the wheels smoother, which helps with the traction.

 

Another detail HP calculators don't consider is component matching. For example where does your cam come alive? Your cam selection is a major factor in choosing what stall and STR you choose for your torque converter. The right choice in converter is capable of dropping 1/4 mile times by .5 sec by itself.

 

I guess the question you need to answer is are you really looking for a number, or are you asking what you need to do with the entire car to attain your goals? Drag racing is all about optimizing combinations, not numbers. Get the weight down low, pull off the sway bars, move the weight to the rear of the vehicle. Just some guidelines that make you get lower times with less power.

 

You had also mentioned drivetrain loss. Make sure your drive line and half shaft angles are good under load.

 

The reason for me bringing this up is that the closer to ideal the chassis and drive train setup is, then the more accurate the HP calculators are going to be. In a nutshell start with the HP calculator and add 1 hp per suckage point your drive train, chassis and driving rack up.

 

So how much does your chassis, drive train and driving suck? I say this in jest, but I think the point is made that there is very little that others can tell you on the forums without much much more information on your car. In my opinon, your goals are very attainable with a 327ci engine.