taws6

iTrader: (2)

Hi,

How come a 4 cylinder car can give a V8 a run for it's money?

Agreed most of the 4 cylinder cars are lighter, AWD with turbo, and they're reving in their upper limits.

Eg 2008 Subaru Impreza WRX STI turbocharged 2.5-liter flat-4 engine puts out 305 horsepower.

Yet my na 5.7 V8 runs the same kind of numbers.

It's just the math doesn't seem to add up.

I know hp / liter is ricer math, so I won't refer to it, but my engin is twice the size, does that mean it's half as effient? It cant be, as mpg / liter is as good.... Hmmm......
Please enlighten me, thanks for the info

13lu91rS

iTrader: (1)

They have this stuff called boost. And it's power by the turn of a **** basically. You turbo your car and see if that sti can keep up!

Ice78Transam

iTrader: (1)

Specific output. Higher compression yields more power. Boost isn't a fair comparison. You bascially answered your own question.

Honda B16A makes 170 hp @7800 rpm. 113 torque @ 6500. Not really usable power coming from an ex-honda fanatic. VTEC cam profiles would idle like a old boat, so VTEC helps immensly with street manners and HP.

LS1 makes almost 300Lb ft @ just over 2000 rpm. spins less to accomplish the same work.

Just look at all the variables.

Just some perspective.

ncfastls1

iTrader: (1)

Well I mean like you said they are lighter, higher revving, and the STi has AWD. Also most are FWD so I'm assuming that's less drivetrain loss considering there is no drive shaft. I know there are plenty out there but personally I have never came across a 4 cylinder that I haven't completely raped.

My friend has a RX-8 that probably doesn't have more than 220 at the wheels and he always talks **** yet makes absolutely no power under 4000 rpm, and even though my engine is three times the size of his I get much better gas mileage than he does lol ******* rotaries. Not to mention I probably make as much torque at idle than his max hp..

conan

iTrader: (5)

Is that 305 hp claim at the crank? Because your 5.7 (ls1 ???) makes over 400 hp at the crank and 320 (+-) at the wheels. Also If the subaru is 305 at the crank the AWD will eat up 20% + power in the drive train, so it probly down to 240-250 wheel HP. Then there is the N/A power VS forced induction... I make 200 more hp with boost VS stock N/A.

the_merv

iTrader: (88)

It has a Turbo to compensate.. basically the same reason a Cobra needs the Kenne Bell.

Ice78Transam

iTrader: (1)

Cliff notes: BOOST, little usable powerband, lower weight.

kinglt-1

iTrader: (26)

Its pretty simple, Boost. In theory running 8psi of boost adds 50% displacement of the engine by air flow volume. Since a motor is just a big air pump right. Step up to 15psi and you double the displacement of the engine and so on. So a subaru 2.5 @ 8psi is flowing the displacement of a 3.6-3.8 litre. so at 15psi that 2.5 is flowing at the displacement of a 5.0 litre. Put 8psi of boost to a stock ls1 and it will flow the displacement of a 8.0 litre and make 500whp. The ls1 will have a way better power curve too. That is the one thing that Boosted 4cylinders lack, power under the curve!!!

elias_799

iTrader: (8)

not to mention that the v8 at 500whp will be allot more reliable then a 4 cyl at 500whp. no matter how many cams it has or how high it revs.

it is easy, get 4 people to lift up a have table or get 8 people to lift up the same table, and then ask yourself which group of people will be less tired.

proporio

Kind of depends how they are built don't you think
90 weaklings or 250 pound runningbacks.

that is why many small engines can take huge amounts of boost, they are built to handle it, and why our stock 10 bolt rear end (for example) can break even with stock power- they aren't built to really handle it.

elias_799

iTrader: (8)

yea the case of most 4 cylinder you get 4 small stroke, small bore weaklings with very low cc's. the reason why those 4 cylinders run so much boost is because their motors are much smaller, 8 psi threw a garden hose and 8 psi threw a fireman hose are a different ball game.

and you think the honda's open deck motors can handle big amounts of boost without serious block work, or maybe you think the Subaru semi open deck block is stronger then the ls series closed deck blocks ? not to mention that the Subaru motor uses liners unlike the sleeves you get in the ls motors

taws6

iTrader: (2)

Well, I think I see why the 4 cylinder can be compeatative, not an easy subjet to explain, so thanks for helping teach a newbie

So basicly, it's because they have a higher compresion ratio and forced induction. And as conan pointed out, that (305hp) is probably a crank rating, I never realise the stock LS1 crank rating was over 400 So my stock LS1 should still beat the 2008 STI?

So the only way to add PSI boost is with FI?
And the only way to increase compression ratio is with new heads?

I was watching some LS1's on 'streetfire' I think, and quiet a few LS1 cars on there were beat by smaller engin cars. I guess enough money against a stock car will win....

JD_AMG

To add to what the others have said you also have to understand that GM only wanted to make 345hp with their LS1, its not like they were trying to get every last ounce of power out of it. This same goes for all the LS-series engines GM makes, they set a target hp/tq number and then go for it from there keeping a nice flat torque curve.
Take a look at the LS6. Do you think GM just suddenly discovered that with better heads and a cam that they could bump up the power of their LS1? No, this was all planned, and they didn't need more than 345hp out of the LS1, and 405 out of the LS6 etc etc.

elias_799

iTrader: (8)

^^ yea, but i think the engineers have made the block pretty strong, knowing that the average gm guy will want some more power out of it. what you need 6 bolt mains for on a 345hp motor ? 4 would of been plenty.

michaelbeale

iTrader: (5)

no, the gm ls1 rating is NOT at the rear wheel. It is thought that the stock numbers weren't quite as high as the motor really made, but the 305 hp for an ls1 is at the crank. I'm pretty sure the bone stock wheel number is around 280 or so?

But anyways, don't ever let a damn ricer try to talk ****. Most of them are clueless about cars, and just got a stiffy watching fasty and furious so they went and bought a honda. They are generally good bullshitters though, but really don't let them convince you that 4 banger is the way to go.

Hondas and the such CAN compete with ls1's, but they have to be modded well beyond the ls1. And even if a given honda is faster than a given f-body, its still just gay, and it won't last.

Ls1 > 4 cylinder

conan

iTrader: (5)

The ls1 is not rated for 305 hp at the crank. I took my stock 2000 z28 with a k/n air filter (only mod) to the dyno before I started modding it,and made 323 rwhp 331rwtq in 85 deg weather on 93 octane.

taws6

iTrader: (2)

Yea, the 305hp quote was from the STI, that's what we think is crank.

I always thought the LS1 was 345 / 350 hp at the crank...?

Nice numbers for a stock car conan, looks like it's got a bit more than that now!!

So the only way to increase psi is with forced induction??

Cyris0014

280 is lt1 numbers an ls1 should be over 310

conan

iTrader: (5)

Thanks man! She's a little faster than stock now When you say gain psi do you mean above ambient air pressure?

kinglt-1

iTrader: (26)

There is a sticky above that tells the power of the vehicle for each year.

https://ls1tech.com/forums/new-ls1-o...mile-time.html