How Much Boost is SAFE
 

If you are going to build a blower engine with the most durable parts how much boost would be acceptable to use?
The most it seems well built engines are good to is about 250 hours but this is not a exact science of course but to run a engine like this to 250 hours how much boost.With 20 pounds I dont think you would make 250 hours
But how much boost would be recommended.I was thinking 10 pounds no more

Alot of variables.. pump gas 93..most I've seen is around 10 for your every weekend boat

Whatever your engine builder will stand behind;). 5# off of a 14/71 is a lot different than 5# off of a 250. So many variables.

a lot depends on what supercharger you are using,a screw blower like a whipple or a psi makes less heat than a roots blower,compression ratio and camshaft selection also come into play.

I am starting with 6 new 548 871 sc builds with all good internals and aluminum heads 8.2:1 comp +/- static and no intercooler. I will likely go up from there potentially to 7 plus but I fill up at the station 99% of the time. Will have a few pulleys during dyno session coming up soon.

john,i have just about every 8mm pulley size so if you need to borrow some for your dyno session let me know.i also have a spare superchiller and belts if you want to try that.

tks mike. I recall you mentioning that some time ago and I haven't forgotten. I will get in touch and Tks. Never thought about taking a few pulls with chillers while it's on the dyno.

I was skeptical on whether or not chillers did much on the roots stuff. After installing air temp probes in the intake manifold with an actual air temperature gauge, the skepticism stopped. They simply work. Seems like on your average larger sized blower, they knock 20-30 degrees out of the intake charge. 20-40 degrees is ALOT. According to Kenne Bells formula, a 20* reduction in charge temp, allows for 1/2 pound more boost. A 10* reduction in charge temp, nets about 1% power gain.

Knock 40 Degrees out of a 900hp engine, youre looking at a 36hp gain just from the cooler air. Throw another pound of boost at it, and now youre looking at 50-75hp gain over not having an intercooler at all.

They do create a restriction of airflow in the intake tract, and will need to spin the blower a little faster to overcome that, but its worth it. Spinning a 10-71 , 5 or 10% faster, isnt gonna create much more heat. Matter of fact, When Mike tkach and I dynoed our buddy joes engines, we went from like 6psi to 10 psi of boost with pulley swaps, intake air temps pretty much stayed where they were irregardless of the increased boost level. Saw that on my own engines as well.

When I dyno'd my 555 this spring, on one pull I forgot to turn the water on to the chiller. It dropped over 30hp without touching anything else.

I'm running 9 Lbs at 6000 RPM with an M4 Procharger

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