vette_tweak

What's the receipe for the highest HP supercharged pump gas large CID small block you've built/seen/ heard of? (looking for info above 750HP) :cheers:

(Actual measured HP, no Desktop Dyno simulation results please!)

MoMo

Wow. Tall order for sure.
I don't think anyone has much information on anything concrete, but if I were to build a motor like that, I'd look for something that would make good torque, have a very good rod/stroke ratio so that you could get upstairs quickly where the big power numbers are made, definitely a roller cam, and very low compression.
750 hp will be hard to obtain even for that. A big block with roots blower can get there easier. A small block is gonna have to really be able to rev to reach that goal.

My first instinct would be to minimize the stroke and maximize the bore, which improves breathing and lowers piston speeds. That translates into cubic inches without overstressing the rods, so that you can build high rpm's very easily. Then you have your choice of blowers to complement it.

Engine first. Build a 400 overbored and destroked with a 350 crank, (which I've mentioned in a couple other posts). Use at least 5.7 inch rods, but see how low you can drop compression with 6 inch rods. When I looked into that, I seem to remember that you can get down to an 8.5:1 compression ratio using 76 cc heads and a -20cc dished piston on 6 inch rods. That's pretty good.

Blower next. You want a blower that really likes the rpm's. The best one for that is the turbocharger. My first choice would be two turbochargers, no smaller than a Garrett T04. If you use a belt-driven supercharger, I'd lean towards the centrifugal supercharger, even though it is not as dramatic as the turbo boost map. Go bigger, like the Paxton Novi2000 for example. And whatever you use, try to intercool it.

Induction next. You want to fuel inject this. I'd stay away from a tuned port manifold, it's too limiting in the upper rpm's. And too expensive to modify for very modest gains. Maybe you want to go with a custom set up. Something made from a converted single plane manifold, which has a natural tuning to where it does well at 7000 rpm. Holley and Edelbrock both make such systems. But you'll need a "hat" to fit over the carb-mount-style throttlebody, and Procharger makes those.

Intercooling: Bigger is better, but don't ignore flow. Probably the best intercooler for the money is a Ford Powerstroke intercooler. These suckers are like 3 ft by 3 ft square, so it'll have to fit at an angle in front of your radiator, like the way C3 radiators sit. If you have room. Spearco also makes an excellent intercooler, but pricey.

Drivetrain: I think you should be okay here, if you use the rpm-type method to get your 750 hp. What usually kills stock Corvette drivetrain components is the tremendous low end grunt.

Cam: Definitely a roller cam. Maybe a hydraulic roller, but for the rpm's above 6500, I'd suggest a solid roller. You'll need something with say a 3500 to 7000+ range. So go steep on your rear end gears. Nothing less than a 3.70.

What torque would you need to hit a target of 750 hp @ 7000 rpm?

HP=torque x rpm/5252, so Torque= HP x 5252/rpm.

Torque at 7000 rpm = 750 x 5252/7000 = 562 lb-ft.
Keep in mind this will be on the down swing, so you're probably looking for a pretty high rpm torque peak around the 5500 to 6000 rpm range.

This motor really is not going to have too much low end grunt, but it will flat out run like hell at higher rpm's. Good race motor.
But I'm thinking it would be a little frustrating to drive on the street.
Maybe not. It might have a true split personality. Just like a smog-era 350 until you get up above 4000 rpm, and then you'd better have some pretty sticky rubber because things will happen fast on the on-ramp.

I'm thinking low 10's et, maybe even 9's.

The Green Rocket

Would this be what you had in mind:
A couple of months ago at the local doughnut derelicts cruise spot a bona fide PSCA racer showed up with a beautiful '69 Camaro. It runs in the 8's @ 160 mph at the drags. Engine was a 434 sbc with a huge ProCharger, digital efi, and an ice water intercooler that took the place of the passenger seat. The owner claimed dyno pulls of ~ 1,140 hp, and he was expecting to find more power in the future.

Thomas

rainman69

http://www.badasscars.com/engines.html

N/A 383 engine...

:smash:

C4-Wolf

Go to this site and check out the specs on the car.
http://www.geocities.com/vette200mph/

804 hp (out of a 350 i think)


[Modified by C4-Wolf, 3:21 PM 2/14/2002]

korvetkeith

http://www.tpis.com/engine_development.html

Theres a 410 making those sort of numbers at only 6000rpms. There are a couple of guys that hang out here making almost 600rwhp, they should know what you'll need specifically. I think you should do a 383, you don't necasarily need to spin the motor fast to spin the blower fast. Just swap the pulleys to reach rpm range for the blower. You'll want to try and max out something like a T-trim vortech with an intercooler. About 8.5:1 CR, the stroker's inherent torque will get you moving until you can build boost. A 396 might be possible but you'd have to run short rods and the ring package on the pistons might not be able to handle the boost. Some sort of front feeding fuel injection manifold will be needed, like a MiniRam, Ramjet, or even an LT1 intake can be retrofitted.

BrianCunningham

Here ya go
John Meaney's 1,300hp, Daily Driver Vette
http://www.popularhotrodding.com/arc...atures01.shtml


Good luck getting it
a) through the drivetrain
b) to the ground :eek:

bill mcdonald

this car was for sale about a year or so ago, I emailed about some detials. I dont have that email any more but, for some reason I think that car has a 427 SB in it.
I also dont think it would get near 800 hp with the S trim on it, The CFM is just not there.

BrianCunningham

For a car that doing more or less
here's a 9sec C4
http://www.corvettemagazine.com/2001...ette/fsv-1.ASP
I've actually seen this car run! :eek:

vette_tweak

Thanks for all the great info!

Here's my actual dilema: turbo or supercharger

My 420CID is now making 540HP and I think I can tweak it out to around 600HP. Adding a supercharger and only making another 150hp isn't really worth the hassle. I did see the 1300hp C4 TT and I wondered how much HP is possible with a SC setup. Yes, the obvious question would be "why not duplicate the 1300hp TT setup"? The cost and complexity of such a project is not miniscule. If I could buy a SC for $5K, slap it on in a weekend and see 1000HP, I'd go for it.

It looks like around 800hp is the "average" SC SBC ceiling with the odd motor making up to 1100hp but this is a street car and replacing my passenger seat with an intercooler isn't a option :D

Monty

I'm duplicating John Meaney's twin turbo setup, except I'm going with 427 ci's rather than 400, since that's what I already have. The car should be done in about 3 weeks.

Not including the engine, engine management system, or any fuel/ignition upgrades, the turbochargers, intercoolers, wastegates, blow-off valves, and the fabrication of the headers, downpipes and full exhaust, custom intercooler and plumbing, and a cold air setup to feed the turbo's is costing about $20,000.

The turbo's, wastegates, and blow-off valves are the cheap part, adding up to only around $2500 or so. The materials to construct the headers, exhaust, cold air, and intercooler are almost $6000. The project is estimated to be around 120-150 hours and the labor bill is around $9000.

Needless to say, if you got the time, welding experience, and the knowledge to fabricate it yourself, you can save alot of money. I seriously debated doing it myself - you can by a pretty darned good TIG welder and equipment for that kind of money, but I don't have the time. I don't have the experience either, but I could have gotten advice and direction from the guys at Fast Times. In the end, I figured that I'd be better off letting the pro's do this job, and since they are all in the same circles as John Meaney, they be able to discuss the details of his setup and figure out what he would have done differently. While there are numerous people who think or say they can do a setup like that, and a lot of them probably can, it takes some knowledge as a result of previous experience and research to know how to do it right to achieve maximum results.

In the end you'll have more power than you could ever want for a streetable car and it will be something hardly anyone else has. I'm pretty certain I won't be seeing too many other custom twin turbo cars at the Friday night cruises.


[Modified by Monty, 9:00 AM 2/15/2002]

AKS Racing

I know of a couple of individuals who have had these high HP (race only) street supercharged cars. Both of the cars were from Houston (both pretty much gone now) and both were well above 1000 hp. Both are on ATIs website homepage. One was above 1300, while the other was in the 1175 range if I remember correctly. These cars were not street cars! One had the gas tank converted to ice tank/recirculation and ran a small seperate fuel cell. The faster of the two I saw multiple times ride the rear bumper, slamming down hard, damaging suspension and engine components. But it was capable of 8s.

Now on the forum ther are several guys who claim in excess of 1000 hp and claim to be street supercharged cars. It is merely my opinion, but either they are not street cars, or they are nowhere near 1000 hp. Look at the components that make up these monsters, and I would lend towards the later, not the former. Now as for a turbo car, they can make very large hp and still be quite tame. I have seen a few of these as well. I used to play with 300ZXTT in the early 90s along with vettes. They can make nice hp.

Define streetable and then build to the maximum that that definition will allow. Some of the larger ATI Prochargers (i.e. D-1X - 1900cfm) will deliver excellent flow, yielding good hp numbers. I am using one of these in my latest build. One thing is for sure, the motor that you currently have will probably have to be changed considerably to work with either the S/C or the turbo. Some things that a na motor loves, a boosted motor may not survive very long with the same conditions.

Best of Luck in your decision.

Aaron

vette_tweak

My definition of a street motor/car is:
- runs on pump gas (94 Octane Sunoco Gold in Canada)
- doesn't overheat in town in the middle of normal traffic ( rush hour not inc.) on an average warm summer day (28 DEG C?)
- doesn't require sacrificing the use of a significant part of the car ( front pass. seat/ stk gas tank/ hood
- doesn't require constant maintanence ( resetting lash or changing plugs every week )
- capable of 400km+ trips (to/from the drag strip )
- the whole setup is good for 25,000Km + with minor maintenance only

It's difficult to compare apples to apples when I read about all these high HP cars. Does John's 1300hp C4 fit my definition of street car? What about Callaway's sledgehammer? Somehow I don't think guys are making 1000hp+ running 20psi boost on pump gas (please correct me if I'm wrong!)

Yes, turbos are awesome. They are more efficient. But are they as reliable as a supercharger? I am frequently hearing about guys replacing the turbos on their Callaway cars.

Then there's the whole "area under HP/TQ curve" consideration. A big TT or SC setup will sacrifice low rpm torque for high RPM power. The TT tradeoff must be larger due to the turbo lag. But then the turbo isn't stealing power from the crank either. Is it a wash? I guess it depends on how much time the engine spends at either end of the RPM scale. On the street, I'd tend to think the SC would be a better ride. How often can you peg the gas and shift at redline on you 1000hp+ vette while driving around on the street? I can't do that very often with my NA 383!

Decisions, decisions...
:rolleyes:

AKS Racing

You will know the correct path when it comes time to make that decision. And I do gaurantee that your wallet will fill the bite no matter which optio you choose.

I concur with your definitions of a street car. At a bare minimum, these are requirements.

Aaron

Monty

I also agree with your streetability definition, but I would also add that it doesn't EVER overheat. I personally wouldn't want to give up air conditioning, power steering, or power brakes either. As much as I'd love to put a huge water-air intercooler under the dash or where the passenger seat is for maximum performance, I don't think my wife would find it very comfortable to sit on.

Unfortunately, I think there are some misconceptions regarding turbos. Turbos do not sacrifice low rpm torque for high rpm power - depending on the size and design of the turbo, nothing could be further from the truth. The only reason I can think of that people believe that turbo's are for high-rpm engines, is possible due to their use in Formula 1 cars that do run high rpms on the fast tracks. However, they run high-rpm due to gearing and top speed requirements, not as a result of using a turbo.

Turbo's are load dependent, relying on exhaust energy, not engine rpm like a supercharger. You can size a turbo to provide maximum boost off idle, but unfortunately if would quickly become inefficient as the engine rpms arose because it would be too small to maintain the boost as the cfm requirements of the engine increased.

I beleive that most misconceptions regarding turbo cars is due to the poor examples that the domestic OEM's produced in the 80's. As with all production crs, compromises are always made, and the cars are intended for the general public. On a production car, the OEM's typically undersize the turbo's to produce boost at very low rpms becuase it gives the typical driver a sense that the car is fast and powerful. But unfortunately, the engine runs out of steam in the mid-rpm range. However, since most people are just concerned with getting from A to B in traffic, they never realize this.

I would argue that modern turbos are more reliable than a supercharger, assuming they are properly sized for the application and maintained properly. New materials, water cooling, better bearings have minimized the causes of past failures. This is also true for a supercharger application as well. Consider that turbo's are commonly used in diesel applications where their use is measured in thousands of hours, which equats to 10's of thousands of auto miles.

Overspinning a turbo or supercharger that is too small to provide the necessary volume and boost will quickly lead to it's failure. As far as maintenance is concerned, it's just a matter of common sense. Use a high quality motor oil, and follow a regular oil change schedule. Same as you would on any high-performance engine. Turbochargers are very simple devices, and it surprises me that so many people are wary of them.

Cost and complexity aside, a turbo is superior to a supercharger, especially if you want to compare "area under the curve." A turbocharger can go from producing zero to maximum boost in less than 1000 engine rpm, that's why turbos are superior to supercharger in producing torque. Superchargers are engine rpm dependant, not turbo's. I've heard people mention that the Top Fuel guys use roots blowers and make 5000-6000hp. That's certianly impressive from a 500ci engine, 10 hp/ci. But consider the turbo Formula 1 cars making 1300-1400 hp with a 90ci engine - around 15 hp/ci.

Everyone always mentions lag when discussing turbo's. Again, most people's experiences with turbos are from production cars (compromises). Lag is only an issue at low rpms, like off idle. If the engine rpm is already at a moderate rpm, say 3000+, then lag will be virtually nonexistant. There will be sufficient exhaust energy to instantly spool the turbo up. In some cases, lag is not necessarily a bad thing, especially if traction is limited, as with a street car running street tires.

As Corky Bell says in his book 'Maximum Boost' - "If you have no lag, you have no turbo. You also have no HUGE TORQUE increase to look forward to."

"Torque peaks are virtually always at lower rpm on turbo engines. Chart all the published data and no other conclusion is possible. The more performance oriented the atmo engine, the greater the difference. The ent effect on the driver is that he or she need not rev the turbo engine as much to move rapidly. This is quite contrary to popular opinion but is inded fact."

Think about what he says and you realize it is true. Another thing that he correctly points out is that a turbo engine makes more torque than a high-performance normally-aspirated engine at low rpms. To make power and torque with a normally aspirated engine, you must increase rpms at some point. My NA SBC 427 made great torque, 500+ lb ft from 3000-7000 rpms, but it made peak torque of 580 lb ft at a relatively high 5100 rpm. I would guess that my TT SBC 427 will make that much torque at 1500 less rpm.

Since you are not having to spin the motor as much to produce the power and performanc eoyu wnat, you can argue that a turbo engine could actually be mor durable than a high-performance NA engine, assuming you maintain reasonable boost levels, and the fuel and timing is tuned correctly.

You pointed out that 1300hp at 20psi of boost is not probably on pump gas, that is true. 12psi or so is generally the limit of boost on pump gas, but even then, you're talking huge amounts of power and torque. HEck, even a low 6psi of boost will increase torque by about 40% (using an intercooler). For those days you want to hunt Snake or hit the track, run some Toulene or Xylene, or race gas, and run it in 'kill' mode and then you can make the big power.





[Modified by Monty, 9:57 AM 2/16/2002]