what are the advantages of a turbo over a belt driven supercharger as far as power is concerned. is the turbo less exspensive than a blower? obviously the engine needs to be built equally stout for either application. i know a intercooled centrifugal blower kit runs around 3500.00 but what does a turbo charger cost? just for fun lets assume a person was building a forced induction nailhead.. will it respond better to a turbo or to a blower. is a turbo easier to intercool than a blower? i read that Buick got nearly 800ft lbs of torque from their experimental turbocharged nailhead..just a little curious here.. Bob
Hi Bob, Maybe I can shed a little light.... A turbo is "free" HP as in it is powered only by the left over "waste" of the combustion process. A turbo system is more expensive as far as all the fabrication in the headers, and exhaust system and additional plumbing (especially if there is not already a kit for your proposed project). A turbo will heat-up the incoming charge more due to sharing a common impellar shaft that transfers the exhaust heat into the incoming intake charge. Couple that with the heat produced from just compressing the air and an intercooler is almost a definate must. If plumbing a carb-blow-thru system the vaporization of the fuel helps there also and will further reduce the charge temperature into the cylinder more than an EFI system will due to the length of the runner and time the charge takes to travel the distance. The fuel has more time to absorb heat and cool the incoming charge. EFi will be easier to tune for the most part, especially if street driven and mileage and street-ability are factors. A carb can still be done by it takes a heck of a tuner willing to spend the time and effort. I still doubt the mileage will be there though if compared to EFI. A centrifugal supercharger/blower (for which there are many kits readily available...even some for our Buick's!) is cheaper in regards that the headers and exhaust can remain standard NA issue (although an upgrade to larger sizes in most cases are beneficial in almost all applications). There is a HP penalty though in the fact that they are belt driven so there will be parasitic losses accordingly. A centrifugal will not heat the incoming charge as much as a turbo due to the exhaust being totally seperated and not allowed anywhere near the incoming charge with a heated common shaft or an other such shared component. Again a blow-thru carb vs an EFI both have their pro's & con's. I did read an article a few years back in 5.0 Mustang magazine of a centrifugallt superchaged 306ci with a 1050 Dominator mounted to a specially built aluminum platform that was directly mounted to the inlet of the Procharger whereas the fuel actually went thru the supercharger and literally "supercooled" the incoming charge exiting the outlet. The outlet tube from the 'charger to the intake manifold actually iced-up and developed frost on it while on the dyno! NO INTERCOOLER NEEDED FOR AN APPLICATION LIKE THIS FOR SURE! I still have this article (or series of) and will dig it/them up. BTW....it made over 900+HP and was still climbing! An intercooler is and will always be a bonus no matter how you decide to pressurize your Buick! And do not forget to plumb in a quality blow-off valve.:TU: Highly doubt I covered everything but I'm sure others will and can add to...
Tons of ways to look at this. The turbo application will probably require modifications to the oiling system, custom headers, and all of the accompanying hardware. On the other hand, the ATI supercharger oiling system is self-contained and doesn't require different exhaust work. If you go the turbocharging route, you would probably need two turbos and would probably want to go to fuel injection. A carb system seems to have worked well in many applications for the supercharger. Your boost is pretty much limited because of the strength of the block (unless you also buy a block), so you are probably looking at 10 PSI boost tops (and you might want to intercool at that level). In this case, I like the supercharger better for the lower-boost application. One potential advantage of the turbocharger is lag- if you are traction limited, you can leave the line without building boost and the turbos will take a little bit to spool up. By the time they are up to pressure, you are hopefully going fast enough to stay hooked. Either way, don't forget to build up your tranny and rearened for all this power! Personally I am going for the supercharger as soon as the budget permits. -Bob Cunningham
thanks for the input guys.. i'm told that there is no concern regarding the strength of a 401/425 block and same goes for the factory forged steel crank. sounds like a supercharger is the least expensive and troublesome option. Bob
Well one thing that makes the supercharger more difficult is the bracketry. I don't know if bracketry exists for the nailhead, or if you would have to fabricate it yourself. That might level the playing field a bit. -Bob Cunningham
A turbo system running a "Blow Through" carb setup is deffenatly ALOT harder to tune than a Blow through Charger setup. I've had my hands on both types of systems. The blower builds gradual boost only at WOT, The Turbo on the other hand will build tons of boost at 1/2 throttle, this makes it a night mair to tune drivablility into a perfectly tuned WOT combo using a carb. Personally if you do decide to go the Turbo route make sure you go with EFI. I can personally tell you that I will be going the Turbo route next time (one big single). Technology in turbos has come a long way and the large turbos spool alot faster than one would think. I can tell you I've been impressed by a couple around here running on small blocks, and the turbos are rated at flowing about 400cfm more than my D1SC, that makes them able to support about 1200 HP Anyway, Chargers are cleaner, cheaper, (unless you can fab) and easier to tune from a carb system stand point. Hopefull this info helps One a side note, I would never do boost again without a intercooler and alky injection, my combo has been happy every since I added the cooler :Brow: --Rich
ok i know nothing about any of this there.. the truth is out!! is it possible to have JUST an intercooler? and what would, if possible, be those benefits?
No benefit in running an intercooler on a naturally aspirated combo.......technically. The incoming air(even underhood air) isn't really heated enough to make intercooling produce a noticeable gain. A ramair system will provide the same air inlet temps as an air to air intercooler would since both use outside ambient air as the intake medium. The reason intercoolers are used is because forced induction compresses the intake charge and thusly heats the air. Too much heat and all compression benefits are lost with a side helping of detonation. An intercooler on a forced induction motor is there to try to bring the air temps as close to ambient as possible. Most intercoolers are about 70-75% effective at this job. However.....Theoretically you could use an air to water intercooler on a naturally aspirated motor although not on the street since you'd quickly run out of cold water. On the track though, you could put ice in the water reservoir of an air/water intercooler and supercool the inlet charge on those hot summer days. Might get 15 to 20 hp out of it....Hmmm Not really worth the expense in the long run on a non-blown engine. Unless you have bags of money laying around and want that extra .15 in the quarter.
thanks for the reply apollo i know a lot of guys ask questions then disappear... i do it sometimes, but trust me i read and appreciate every answer i get
check out these Ford sites for info on turbos read as much as possible www.toohighpsi.com or www.turbomustangs.com I was building a budget turbo 455 in a 81 g body wagon. gave up, not because I couldn'tbe done, but because I have no time and the torque would tear the rusted car apart
Supercharger would work better on a nailhead, why? Because of the horrible port design on the exhauste ports would choke the turbo down and lead to rediculously high valve temperatures which is the #1 cause of preignition. On a more general note, turbos take less power to run since they are using the waste energy from the combustion process and when properly sized don't up backpressure too bad. Superchargers, roots or centrifugal, consume power dirrectly from the crank and put the crank in sheer loading with the pulley. Also pointed out, turbos make power based off of exhauste volume and temperature, while superchargers are dependent on rpm. This can be a good or a bad thing depending on what you are looking for. As far as the temperature at the outlet, it shouldn't be much different between a centrifugal SC and a turbo, they both use nearly the same compressor design and the heat transfer though the shaft is minimal, even without watercooling. I seriously doubt it was the outlet tube that was icing, that is completely violating bernoulis principle because you are increasing pressure in a fixed volume meaning the temperature will go up, The carb, like anyother draw through carb, will have icing problems due to the pressure drop across the carb lowering the temperature. There also is the issue that a procharger is not designed to have fuel running through it and will most likely die of bearing contamination pretty quickly not to mention the impact of fuel droplets on the compressor wheel at 50,000rpm! Fuel will have roughly the same specific heat across the phase, ie liquid, gas, solid; so you'd want cold fuel going in at the hottest intake point so that you can use Newtons law of cooling which states the rate the heat drops in proportion to the difference in temperatures. This will also give you the lowest average temperature since you get to soak up heat with both the change in temperature of the fuel but also in the phase change energy to go from liquid to gas. Compressing the fuel/air mixture does nothing but heat it up and waste the cooling potential of introducing it later after the SC or turbo. In responce to intercooling an NA car, they tried that on a Buick, its call the KB coolrunner, honestly didn't sell or work too well and I'd be worried about cracking the manifold if I put too cold of water through the passages with the thermal stress between the hot oil on the underside and cold water in the "cooler" channels.
