Brainstrom: ghetto turbo mod

Kenny_McCormic · Post by **Kenny_McCormic** » Sun May 25, 2008 6:22 pm

While working on the OHV piece of s*** mower engine that shouldn't be allowed to be called a briggs I noticed something, the fan shroud has a big hole on the side that blows into the air cleaner, making a sort of ghetto turbo system.

Anybody ever do this to a spree or something to see what kind of gain could be had? All one would really need is a spare airbox lid, fan shoud, and a pile of jets. This would probably be best on a 4 stroke where you wouldn't just be blowing gas out the exhaust if you over blow it.

Post by **noiseguy** » Sun May 25, 2008 9:27 pm

I research this once; turbocharging a 2-stroke leads to some pretty poor results compared to building a tuned pipe or just raising compression.

Kenny_McCormic · Post by **Kenny_McCormic** » Sun May 25, 2008 10:34 pm

Like I said best done on a 4 stroke, I have been thinking of doing it to this POS briggs I have.

tru72 · Post by **tru72** » Mon May 26, 2008 1:13 am

if i could find a small cheap turbo, i defiantly have a way to get the exhaust to work.. lol if ...."small, cheap turbo" haha

fireblade · Post by **fireblade** » Mon May 26, 2008 3:18 am

Don't get me started on briggs and scrapiron motors. Despite having one on my highly unsafe go-kart, I loathe them with a passion. (With the white hot intensity of 1000 suns)
Their are a bunch of hapless souls http://karting.4cycle.com/ here, who have an affinity for briggo motors.
If you were really demented, you would fit an Asin AMR300, or AMR500 roots supercharger. But two smokes dont like forced induction do they?
Although in saying that, I once saw a blower for sale that was advertised as a scavenger supercharger, from the exhaust side of a two stroke. But I'm not 100% cetain how that might work.

spreer' · Post by **spreer'** » Mon May 26, 2008 9:43 am

Posted: Sun May 25, 2008 8:27 pm Post subject:

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I research this once; turbocharging a 2-stroke leads to some pretty poor results compared to building a tuned pipe or just raising compression.
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Admin, Hondaspree.net

A tuned pipe is a good idea, but raising the compression ratio on a scooter will likely slow you down on top and add a little power lower in the rpm range. In my KX250 the compression ratio drops pretty low at high rpm. It helps the thing rev.

Kenny_McCormic · Post by **Kenny_McCormic** » Mon May 26, 2008 11:49 am

fireblade wrote:Don't get me started on briggs and scrapiron motors. Despite having one on my highly unsafe go-kart, I loathe them with a passion. (With the white hot intensity of 1000 suns)
Their are a bunch of hapless souls http://karting.4cycle.com/ here, who have an affinity for briggo motors.
If you were really demented, you would fit an Asin AMR300, or AMR500 roots supercharger. But two smokes dont like forced induction do they?
Although in saying that, I once saw a blower for sale that was advertised as a scavenger supercharger, from the exhaust side of a two stroke. But I'm not 100% cetain how that might work.

What POS made you think briggs sucks? Any of their pan head, cast iron or iron lined motors old enough to have an adjustable carb will run for * ever if you keep it full of oil.

CharlotteSpreeRider · Mon May 26, 2008 12:05 pm

I don't like the plastic carbs, but if you can get ahold of an aluminum one, you can run it forever. I had a 1977 Montgomery Ward lawn mower that was still running strong when I moved out of my mom's house in 1996.

-aseigler

Kenny_McCormic · Post by **Kenny_McCormic** » Mon May 26, 2008 12:43 pm

CharlotteSpreeRider wrote:I don't like the plastic carbs, but if you can get ahold of an aluminum one, you can run it forever. I had a 1977 Montgomery Ward lawn mower that was still running strong when I moved out of my mom's house in 1996.

-aseigler

Iea, I got a 1970 8 hp vert shaft on a beater mower (this is a transplant engine we put in mowers with blown engines so we have a back up) barely burns oil and will mow an acre of thick grass on a half gallon of gas without bogging down (on a 42" deck).

jstone · Post by **jstone** » Mon May 26, 2008 1:15 pm

I'll stick to my 27hp Scag

gobucks · Post by **gobucks** » Mon May 26, 2008 11:40 pm

what if you made a turbo by carrying a compressed air tank on board and forcing the air into the intake manifold.

or what if you ran a propane tank into the intake as a "nitrous" system.

fireblade · Post by **fireblade** » Tue May 27, 2008 3:36 am

Kenny_McCormic wrote: What POS made you think briggs sucks? Any of their pan head, cast iron or iron lined motors old enough to have an adjustable carb will run for * ever if you keep it full of oil.

The 5hp side valve on my suicide kart came off a fuel pump from a fuel tank to a generator on a ski field. Kea's (A New Zealand alpine parrot, with a penchant for stealing stuff out of the back or your car. And pecking stuff to bits) had attacked the motor. I spent ages getting it to go again. (It had seized from lying dormant for too long) All the dis, and reassembly, put me off these motor BIG TIME. Also trying to keep my briggo powered Lawnmower going has really given me an especially hard spot in my heart for these under designed piles of crap.
At work most of our small plant uses Honda engines. Comparing hondas to briggo's, is like comparing stihl chainsaw to a stone axe.

Post by **noiseguy** » Wed May 28, 2008 11:51 am

The Honda OHV engines are a marked improvement over a sidevalve of any design. Also more expensive; you get what you pay for.

One of my buddies once "supercharged" a bench-mounted Briggs with a hairdryer... it screamed along for about 30 seconds until it finally failed; they didn't bother compensating for the compressed air by upjetting the carb.

Running hot air from the fan (it would be hot air) probably wouldn't be that efficient. If you want some boost, try running an ice (or dry ice) cooled intake runner into the carb mouth; that should give you a bit of boost over surface temp air.

Kenny_McCormic · Post by **Kenny_McCormic** » Wed May 28, 2008 3:50 pm

Where I would take the air (and where this mower took air) was before the cooling fins where the air would heat up. But I dont want/cant afford a blown motor so this idea is staying on back burner till dad swaps the oil burning (like fill it up every gas tank) 8 hp on the splitter out for a big * ANCIENT 12hp engine.

Throw the 8 horse on my cart (we have agreed we are gonna destroy his POS after we have no need for it) after I wipe the oil coating off it cut some holes run an old vac cleaner hose, back out the the needle on the 1970 updraft carb, run it till she fries. 60+MPh should be fun on that little cart.

Burgleflickle · Post by **Burgleflickle** » Wed May 28, 2008 5:13 pm

noiseguy wrote:The Honda OHV engines are a marked improvement over a sidevalve of any design. Also more expensive; you get what you pay for.

One of my buddies once "supercharged" a bench-mounted Briggs with a hairdryer... it screamed along for about 30 seconds until it finally failed; they didn't bother compensating for the compressed air by upjetting the carb.

Running hot air from the fan (it would be hot air) probably wouldn't be that efficient. If you want some boost, try running an ice (or dry ice) cooled intake runner into the carb mouth; that should give you a bit of boost over surface temp air.

You could just go find a cheap intercooler.