Some have a setup like that where there is a control valve that will divert air to a shorter length runner or just activate a shorter runner. I think mazda did this. Others like the porsche varioram setup has a "trumpet" that slides up and down to extend length
http://www.instant-g.com/Products/36...sion/VRAM.html

On a turbo car i dont see the need for variable intake runner. If you want high rpm, build it for higher rpm and let the turbo do the work and add gear to make up for poor bottom end. Turbos dont need high rpms anyway to work. If you build for high rpm you start getting into large turbine sides which delays spool and combined with larger cam size and lack of compression you start making the bottom end very soft. Only way to combat that is to combine variable runner length with variable cam geometry and that isnt really cheap to do, if even possible on chevy small blocks. You would need huge variance in valve timing and huge variance in intake runner length to develop power down low if you had a motor designed to pull to 7-8K rpm.

Viper V10 does VVT but doesnt have variable intake lengths from my knowledge. The Cam in Cam system should be possible on a SBC, just dont know if that has been tried yet. LSx has something but thats not SBC

 

Another noteable example is Ford's modular engine. On some of the DOHC 4V engines, they used variable intake manifolds, one of the most well known examples is the Lincoln Aviator.

Then BBK got a look at the design, and produced an aftermarket piece which I believe they no longer manufacture, due to the high cost. It was nearly a grand.



Looked like a neat piece, not really sure if they still have it or not. But I can't find it on the site.

List of all applications.

http://en.wikipedia.org/wiki/Variabl...ntake_manifold

 

Because everyone keeps forcing the "RPMS wins races" thing down my throat so I've been trying to understand it. I don't drive a manual, so I don't have real experience of gears and shifting affecting my speed, but everyone is always sayin "....'and when your shifting I'm still revving into my power band and will keep pulling on you.'"

So I decided to see if I can attain a high revving 350 and get the best of both worlds =D

 

Power wins races...... where you make that power is up to you but if its up high, you will have to have the proper gear ratio/tire size combo to make it work for you. Same if its down low.

Area under the power curve helps alot too and some "peakier" high rpm motors may not have alot of power under the curve, so to get them to run fast, you need tight gear ratio spreads to limit the rpm range in which the motor operates. Some high end drag race stuff may operate in a 1000 rpm or less window, while street stuff may see 2000-3000 rpm depending. On a setup like that, area under the curve is important.

Everyone asks me why I run 2.73 gears in my turbo car...its not to help spool...its because all my power is at low rpms. This motor is stout from 3400-5500 rpm. With a small diameter 26" tire, 2.73 gears are pretty close to being optimal. Just do the math, 150mph with those gears and 26" tire means motor rpm is at 5294 rpm if no converter slip. Most converters have anywhere from 5-12% slip... thats now 5559-5929 rpm depending. Thats crossing the 1/4 mile line right at or slightly beyond peak hp. I've only been 141-142 but i plan to hit 150 with this setup so the gears work. Gear and tire the car to match the motor rpm band.

 

Don't listen to what everyone is always sayin. A high revving 350 is meaningless if your not introducing more air up top than down low, and the duration and lift in conjuction with how much air your cylinder heads and intake are actually flowing will dictate that. In the turbo buick world, we go no higher than six grand, so we match our cam, stall, gears and tire sizes based on that. Your buddies can keep it in their power band all they'd like, what matters is your rate of acceleration, and that involves the RIGHT combination of parts found in your drivetrain, collectively. It isn't just about high RPM....

 

That person sounds like an auto fanboy, who probably does not know how to properly shift a manual. This video is of me going through 1st to 4th in the Mustang. This is full lift shifting, using the clutch, just regular shifting. Yet you can barely hear me come of the gas, since it's nearly instant. Not even my quickest, I just wanted to get a decent run on video.

http://www.youtube.com/watch?v=-LtbXmDKGRY

I have an SCT Livewire handheld tuner that I have the shift light set to 5,500 RPM on. My little 4.6 doesn't make any more power past 5,200 RPM stock, and they still manage to make over 300 LB-FT and over 250 HP stock. I'm probably making around 290 crank HP now, right around 240 RWHP.

Not much, but it gets me from a slow roll to 90 in less than 10 seconds. Which isn't bad at all considering a 505 HP Z06 hits 0-100 in 8. Haven't timed it from a dead stop since I either blow the tires off, or have to slip the clutch.

 

It's not about auto vs. manual, it's about RPM range and when you have to shift. Each time you upshift, you're forced to toss away a good chunk of your rear-wheel torque, which is what accelerates the car. The later you can upshift, the longer you get to keep your low-gear acceleration.

 

I know this, but the way he phrased what someone else said to him was as if their automatic was just staying in the powerband while it takes 10 years to shift a manual. Fact of the matter is, most auto cars in stock form are slower than their manual counterparts.

I like both. Which is why I have a T56 in the Mustang, and the IROC is staying an auto. Selling my stock 700R4 to a member on here, and I'll eventually pick up a built 700R4 from PATC if I decide to build a 383.

 

Then why wouldn't a large geared, torque machine be ideal for acceleration? These small high revving cars are flying pretty good with almost no torque in their motors, let alone at such high rpms. I didnt think you needed torque for acceleration after first gear.

 

That's because it's all about work done over time. They're essentially replacing loads of torque with smaller amounts of torque, except very high in the RPM range.

Since HP = Torque X Engine RPM / 5,252, where the torque is in the RPM range, and how much torque is being produced is what determines everything.

500 LB-FT of torque at 4,500 RPM = 428 Horsepower.

250 LB-FT of torque at 9,000 RPM = 428 Horsepower.

It's all about substitution, and for these Italian supercars being mentioned, a very high RPM range is desireable. Let's use my setup on the Mustang as an example.

T56 6 speed gear ratios:

1st: 2.66:1 - 5,500 RPM = 42 MPH - 8,000 RPM = 62 MPH

2nd: 1.78:1 - 5,500 RPM = 63 MPH - 8,000 RPM = 92 MPH

3rd: 1.30:1 - 5,500 RPM = 87 MPH - 8,000 RPM = 126 MPH

4th: 1:1 - 5,500 RPM = 113 MPH - 8,000 RPM = 164 MPH

5th: .79:1 - 5,500 RPM = 143 MPH - 8,000 RPM = 208 MPH

6th: .63:1 - 5,500 RPM = 179 MPH - 8,000 RPM = 261 MPH

Rear tires: 285/35/18

Rear differential gears: 3.73:1

I make peak power at around 5,200-5,300 RPM, and I shift at 5,500. I believe this Ferrari V12 mentioned makes peak power at 8,000 RPM. Let's compare the speeds in each gear. So, with those speeds @ each RPM above provided, I hope you can see why it's important to these supercar manufacturers to have essentially engines with two personalities. Variable cam, variable timing, variable intake runners, all of that technology, to have good low end performing engines, and have the same engine scream and make peak power at 8,000 RPM.

Makes them good for just about anything. Tight tracks, top speed runs.

Speaking of this, now I need to have a twin turbo stock bore/stock stroke forged 281 built, so that I can rev to 8,000 RPM in 6th and do over 260 MPH even with 3.73 rear gears!

 

So the only reason to rev higher is to keep your torque multiplication from gears longer? if you move your peak torque higher into the RPM range wont you see a surging pull as you hit that range? But you have no torque from gear multiplication so shouldn't you slow down as you upshift...

 

It just makes the engine much more useable. A Ferrari FF makes 651 HP @ 8,000 RPM with a 6.3L V12. It makes 504 LB-FT of torque way down at 6,000, which is considerably low compared to where it makes peak power, it seems to have a very wide powerband.

651 HP @ 8,000 RPM = 427 LB-FT of torque.

Between it's peak torque range, and peak horsepower RPM, torque only drops 77 LB-FT, while it has gained a pretty significant 2,000 RPM. You can accomplish a very similar torque curve with something like engine factory's 500 HP 383 stroker. That engine only drops 10 LB-FT of torque between it's peak torque range, and peak HP RPM. However, after it's peak 500 HP @ 5,700 RPM, it's pretty much done. Which means to be any good for a top end speed type of car, it would need very low gears, which are no good for down low in the RPM range.

470 LB-FT of torque @ 4,800 RPM. 500 HP @ 5,700 RPM. That comes to 460 LB-FT of torque at 5,700 RPM.

Being all tuckered out at 5,700 RPM just would not be preferrable for a supercar.. The 383 I used as an example has an INCREDIBLE torque curve, but just doesn't have it in it to make much power past 6,000. You could force it to rev a lot higher with super light forged internals, different cam, different heads, higher flowing intake manifold and carb, but there's really no point in making an engine that'll be sloppy down low since it'd be built to be a top end screamer, when you can have that same sort of power before 6,000 RPM.

That's where infamous technologies such as "VTEC", the dozens of different variable intake runner manifolds come in, variable timing, all of that stuff that helps the engine perform as best as it can at any RPM.

But I mean, if you want a 350 that can rev to 10,000 RPM or whatever, go for it. I'm happy with my Mustang making peak power at just over 5,000 RPM and having over 300 LB-FT of torque, and I'll be happy with making power under 7,000 when I eventually build a 383 for the Camaro. I'm not building a world class supercar, so I don't care if I produce optimal power at every RPM for the best possible corner exit. The Mustang has a pretty good combination of acceleration, and top end with the T56 and 3.73 gears. I'm happy with not having all sorts of variable cam technology.

 

However, some day, even if it takes me 10 years to save for it, I will buy myself a damn Ferrari F430, speaking of Ferraris. They're one of the few supercars I love, them and the Lambo Gallardo.

Them F430's SCREAM at almost any RPM. There's over 200 F430's for sale on autotrader for under $200,000. I need one.... Even though I only have a little over $2,000 right now. 100 times what I have now, and I'm there!

 

So that 383 can't perform because it can't make power above 5.5k rpms?

 

Oh my goodness.... You are not getting the point.

Yes, that 383 has a hell of a lot of torque and a lot of power for a street car. But in identical cars, that Ferrari 6.3 V12 that outrevs it would most likely win. Plenty of low end torque for recovering speed from corners, and a huge powerband to continue revving without going through all of it's gears.

In short, a better powerband will typically win when it comes to anything besides drag racing. With drag racing, you can just throw a stalled auto behind any cammed out engine, and keep it right in it's peak power range.

This thread is starting to be nothing but fail. It seems like you only want to rev high because a Ferrari can make peak power at 8,000 with all sorts of variable cam technology. Just build yourself a nice stock stroke 355, or a nice 383 and be happy with it. Or, get yourself a 1999-2000 Civic Si, or B18 Acura Integra, and rev the hell out of that 1.6 and 1.8.

 

I don't think it's fail, I was starting to understand a bit about wanting RPMs, but whatever. I just cant wrap my head around powerband theorys with RPMs. I keep thinking HP is HP regardless of how you get it but then I never see any high-end sports cars aside from the Vette and Viper that use that method of power generation, so I wonder why. Not trying to **** you off, just finding info............

 

In a way, you're correct, HP is HP. Whether you make 500 LB-FT @ 4,500 RPM or 250 LB-FT @ 9,000 RPM, it's the same 428 HP.

However, designed correctly, that engine that makes 428 HP way up @ 9,000 RPM could potentially have a way better powerband. It depends. With peak power at 4,500 RPM, it'd need very low ratio gears and a ton of torque throughout the powerband to be competitive. While the car that makes that same 428 HP @ 9,000 RPM could run higher ratio gears to have a lot of low end grunt, and still achieve high top speeds with the RPM.

Depends what you're trying to do. What is your goal for your car? Autocross? Drag racing? Top end speed? Personally I prefer top end speed, and a little bit of cornering. That's why my stock 4.6 won't be around long if I ever decide to go with an MMR shortblock. I just have too many projects/ideas right now. A few weeks ago me and a friend were driving around, and I went down to 2nd to take a corner. Tires broke loose a little bit, and I was out of RPM in a matter of a second and had to grab third.

That is one of the advantages to a broader powerband. Not shifting as often, maintaining that torque multiplication on the differential throughout a corner, while being able to continue accelerating.

The second fastest production car in the world is American. It has a big 387 cubic inch twin turbo V8. The SSC Ultimate Aero. It's underrated at 1,287 horsepower @ 6,075 RPM and 1,112 LB-FT @ 6,150. It actually produces 1,300+ HP and them turbos keep feeding it until 7,200 RPM. Runs 9.9's and has done nearly 260 MPH.

If a car like that could only rev to 5,700, it would need gears as low as about 2.70:1 to achieve the speeds in each gear it can by revving to 7,200 with a 3.44:1 differential. That's another huge example of the uses of a higher RPM range.

It has plenty down low grunt with decent 3.44 gears, and revs to over 7 grand to achieve the speeds it does. Orr89rocz runs really low gears, (I think he's said 2.73?) but only because they fit his setup. He has a big 401 that doesn't need to rev high to make big power, and he's running some very high trap speeds, so he needs the low gear ratio for the speed. I believe low 140's MPH.

 

BOTH of the Mopars I get to drive on a daily basis touch the high 13s in the 1/4 and both have a 6,800 rpm rev-limit and both get shifted around 6,500 rpm and make power to that RPM. One is a 5,500 lbs Hemi Quad Cab Ram and the other is a 4,600 lbs 4.7 Club Cab Dakota. Nothing done to either engine other than springs, mild cams, opened up exhaust, and programming. Both engines are cammed properly to make as much torque as possible from the stall speed to the fuel shut-off. It makes for a fun street experience, because no matter what RPM and speed you put your foot into it, it goes.

The key to reving like that on the stock bottem end is the fact they were built with close tolerances from the factory, fairly balanced for a production engine, have lightweight rotating assemblies with long rods, and good oil control with a quality synthetic oil.


http://www.youtube.com/watch?v=H7dYtz2xga8

 

Speaking of that, I forgot Orr89rocz's post was in this thread. Heh, looked up and there it was where he mentions his gears.

 

This car is going to be high end speed, acceleration and turning. I'm not building it for low end because it has enough torque from that motor (plus it will be turbod later) that it will have plenty of low end throttle to have fun in the city without accidentally spinning tires taking off from a red. I'm trying to make it competitive with M3s and M5s and that class of a car.

 

I wish I had the power to run 160+ MPH. I've had the Mustang up to around 130 a couple times. 140's a couple of times. Left it just pinned in 5th for a little bit one day when a friend who doesn't like Mustangs much was with me, came close to 150. Don't have the power to really turn 6th gear though. It's pretty low at .63.

It's not actually that bad up top. Pulls pretty good past 100 and to around 130 for having a stock engine besides a cold air intake. All my mods are basically between the gears, T56 swap, tuner, exhaust.

http://www.youtube.com/watch?v=tgJxjhC5EKI

My handheld tuner won't display anything more than 128 MPH for some reason, did low 130's there. Looked down at the speedometer one morning when I had an empty highway, 130's, 140's, tuner still said 128.

It's fun, just don't get a lot of opportunities to really do anything. Only get a quarter mile at the track, there's only a few mile events around. I'm more of a top end speed person too, so it's annoying. Either have to break the law or have no enjoyment.

 

All my friends in college have import cars. We got a tuned A4 turbo, a Talon turbod, my Firebird, an 89 Supra turbod. Everyone of them is tuned for top end. Thats where I'm competing

 

If your 305 at least runs, you may already have them.....

I honestly wouldn't be concerned with college kids with an 80's Toyota, a DSM, and a Volkswagen powered Audi, unless they have some serious part time jobs and dump a lot of cash in them.

 

Build a 355 with long rod and 210cc heads with a solid roller. Ask for 7000rpm peak hp and shift by 7500...I think you will be VERY happy with that build and it will still have good torque down low.

You maybeable to do that with a hydraulic roller with a real good custom grind cam, hollow 8mm valves, and plenty of spring pressure, titanium retainers... AFR heads come with the 8mm valves..not sure if anyone else is doing it. LSx guys use 8mm stems and I personally know a friend of mine who has taken a 4.8L lsx to 7500+ rpm with a hydraulic roller. Its about lightweight parts and proper cam lobe design but can be done although pushing limit on hyd rollers. If you do that, go Morel lifters, you can run alot of spring on those without it collapsing

7000rpm in any sbc is turning pretty darn good. They sound amazing. I used to shift my 383 at 6800 but have hit the 7k limiter many times. It was a top end motor

 

I have a 355. And they all push 300 to the wheels, btw. I like their cars, the Supra is ridiculous. being thrown against your seat like that is a huge rush when that turbo spools up haha.

And yea thats why I was originally asking this stuff, I need to decide how to proceed with my 350, while keeping in mind it is my driver till I buy another vehicle.

 

Now I need to order some Hitech stage 2 cams, and a few other bolt ons for the Mustang so that I can hit 300+ RWHP.

I was actually going to in February/Early march and aim for 300 RWHP since that sort of power and the T56 would be nice. Then I decided I'd just keep stock cams, still go with the 6 speed swap, and just eventually save for a centrifiugal blower or whatever I'm going to buy next.

Should just go with the plan I've had for a while. Jetta TDI as a new daily driver to give the Mustang a break, since they're cheap and get awesome mileage, and a bike as a warm weather daily driver to split up the miles. And just keep the Mustang and Camaro hidden in the garage, as weekend cars. Well, at least the Mustang anyway. It is unclear at this point when the IROC will ever live again.

 

You could also build a 377 (destroked 400) if emissions aren't required.

 

IF done right, a big hydro roller 355 can make peak power to 7000 rpm but you will need light valvetrain stuff. It can still be streetable but will be rough. you can make well over 400whp like that.

 

my god, see its fast and furious that messed with alot of people.

to me its not about being the FASTEST car, or owning a SUPPER CAR LAMBO, w.e i would never own a lambo, theres a reason lambos are so expensive, theres a reason so many lambos get wrecked by rich white guys because they wanted to change the radio station, it just doesnt appeal to me,

to me its about doing what you can with what you have, the experiments they did in the 60s with hogging out heads, and playing with cam designs is what it is, if i had 50k$ i could build the best damn motor out of premade parts from summits sight. then pay someone 60$ an hr to build it, and pay him 60$ an hr to maintain it. so i can drive around rich and high and mighty. but not knowing how to change my damn plugs? to me your not a hot roder your just a bunch of fail. these kids with there hondas and a pipe clamped fart can on it is not hot roding, its just a kid who saved his lunch money to make his car sound like crap so he can talk crap. thats all.

if i had money for a lambo, i would buy a 55 chevy 210, home build a 454, two holley 750s and toss an i beam front axle on it, and toss primer on it and a 4speed. grand total, eh 5~7k into the car if that. then drive the crap out of it. and still take 75% of cars in the area, its not about being fastest or going 400mph. where could you besides the salt flats? dont need it. just want to be happy doing what im doing with what i can get. thats how hot rodding was.

just my 2 cents, guys, to whom his own.

 

Thats exactly why I want to have a high revving streetable 350 and not another 383 or big block form an old chevy :P I stopped criticizing the tuners when I met a bunch who didn't have fart cans, they were just a 3 inch exhaust for their turbo'd 4 making 280 horses on a 1500 pound chassis. Say what you want, but they fly.

I don't think any one in here is mechanically inexperienced, we were just discussing high-revving motors in various applications and what the real benefits are compared to a classic 350 build.

 

naw i understand, and i understand the tuners, they are the same our camaros or my camaro is to me. i just think the supper cars are cool in there own way, but id never strive to build something or own something like it. but the key phrase is to whom there own. my friend wants an audi A4 and i basically said well bud, better have deep pockets when it breaks down or something happens, but if thats YOUR DREAM CAR, get it man, my camaro is my dream car, my 79 is, and someday i hope i can afford a 55 gasser, but thats down the road, but still to whom there own.

but the kid with the fart can on a civic hatch back, and stock everything else, just so he can talk crap. or give him an excuse to bad mouth, are just LAME.