Author Topic: how about a homemade supercharger? (Read 6782 times)

SMOKEYDUB · « **on:** January 05, 2005, 06:59:21 pm »

I have an extra turbo lying around and i was wondering about doing a belt driven turbo (supercharger). I would probably have to use a cog belt system but how could i make it spin fast enough? could i do it with a songle pulley that way i can have full boost just over 2000. I dont know its just a thought.

thanks
Jeff :twisted:

QuickTD · « **Reply #1 on:** January 05, 2005, 07:38:42 pm »

Average speed for a smallish turbo would be in the area of 120000-150000rpm. That would require a speed up drive with a ratio of about 60:1. I don't think you'll get it in a single reduction, that would require a 60" (5 foot :shock: ) pulley on the crank and a 1' pulley on the compressor. Paxton uses a planetary friction ball drive setup to achieve this ratio in a very small space. Some other manufacturers have come out with planetary gear drive setups that last longer (but are noisier) than the paxton setup. Fancy compressor wheel geometry allows the gear drive models to run at significantly lower rpms than the original paxton.

Centifugal superchargers also suffer from some of the same lag problems as turbo's even though they are crank driven. Any centrifugal pump follows "fan law". The flow vs. rpm curve is not linear but roughly quadratic. Air pressure does not double if the speed doubles, it quadruples. A diesel engine tends to draw air in a roughly linear fashion so in order to have a sane amount (say 20psi) of boost at 5000 rpm the boost at half the max speed (2500 rpm) will be around 5psi.

jtanguay · « **Reply #2 on:** January 05, 2005, 10:54:29 pm »

cant you get turbos that spool up at around 1800 - 2000 rpm? that would be your best option, as maybe the friction might damage your turbo shaft

Has anyone tried an electric blower fan in their engine? I saw an electric turbocharger on ebay before, from Germany. It produced around 7 PSI at around 48 volts (using a volt stepper from the 12v battery) That would be a neat option too, but will put stress on your alternator (sorta like an on-demand supercharger!)

shakakan · « **Reply #3 on:** January 06, 2005, 03:58:16 pm »

The electric superchargers where a gimmick, they did not work.

cadmo · « **Reply #4 on:** January 06, 2005, 04:43:31 pm »

how would that guy from the vw dealership mount the step-up gear box on the turbos?

jtanguay · « **Reply #5 on:** January 07, 2005, 01:08:00 am »

electric superchargers do work. Just not the ones you see on ebay claiming 18'000 rpm and 8 psi boost etc. The ones that do work will drain your battery in a matter of... oh say minutes?

unless you have a good enough supply to it (100 amps alternator might do it)

Dr. Diesel · « **Reply #6 on:** January 07, 2005, 08:36:39 am »

I'm driving a vw diesel engine outfitted with a turbocharger. I can get any boost up to 27 psi with the twist of the wrist. I can launch it so boost comes on full before i'm even halfway through the intersection. Everything bolts on, no fugging around, factory reliability.
Easy!

MacGyver · « **Reply #7 on:** January 07, 2005, 10:21:59 am »

Quote from: "Dr. Diesel"

I can launch it so boost comes on full before i'm even halfway through the intersection.

:twisted:

jtanguay · « **Reply #8 on:** January 07, 2005, 04:26:01 pm »

Dr. Diesel PLZ share with us your secret!! I wanna have boost like that too!!

Dr. Diesel · « **Reply #9 on:** January 07, 2005, 07:30:52 pm »

eez no seecret! boost controller and a healthy k24 will do it. it's too much for a k24, but it'll do it. a hybrid on the other hand.....

moTthediesel · « **Reply #10 on:** January 07, 2005, 07:47:20 pm »

How about a really large turbo compressor from a big heavy equipment diesel or even a tank? Wouldn't they produce the needed volume and pressure at lower revs?
moT

jtanguay · « **Reply #11 on:** January 08, 2005, 02:07:58 am »

i think smaller turbo would spin up at lower revs

about the boost controller. I thought they just regulate at what psi the wastegate opens up at... Must be a good turbo if it can boost that high at lower rpm

chrissev · « **Reply #12 on:** January 14, 2005, 09:38:43 pm »

Quote from: "QuickTD"

Average speed for a smallish turbo would be in the area of 120000-150000rpm. That would require a speed up drive with a ratio of about 60:1. I don't think you'll get it in a single reduction, that would require a 60" (5 foot :shock: ) pulley on the crank and a 1' pulley on the compressor. Paxton uses a planetary friction ball drive setup to achieve this ratio in a very small space. Some other manufacturers have come out with planetary gear drive setups that last longer (but are noisier) than the paxton setup. Fancy compressor wheel geometry allows the gear drive models to run at significantly lower rpms than the original paxton.

Centifugal superchargers also suffer from some of the same lag problems as turbo's even though they are crank driven. Any centrifugal pump follows "fan law". The flow vs. rpm curve is not linear but roughly quadratic. Air pressure does not double if the speed doubles, it quadruples. A diesel engine tends to draw air in a roughly linear fashion so in order to have a sane amount (say 20psi) of boost at 5000 rpm the boost at half the max speed (2500 rpm) will be around 5psi.

I wonder, could you not just somehow waste gate out the extra psi at 5000 rpm and then max out your psi at say 2000 rpm with a supercharger? You could have some sort of dual intake set up where the first intake supercharged the air up to a certain psi breaking point then wastegated it, then have your regular turbo keep pumping right up to max rpm through the second intake. Supercharged at low rpm, turbo'd at high rpm. Doable?

jtanguay · « **Reply #13 on:** January 16, 2005, 04:05:05 pm »

hehe but the mpg will decrease

I'd say get one of those electric superchargers, stick 2 batteries in the back of your car and create a switch for it in the cab. Some of those electric superchargers can produce 9 PSI boost!!! in the idle stage this would mean some serious performance increases, but at the same time drain those batteries

. Then with the aid of a boost gauge, you can shut off your supercharger, and let the turbo do its job