Compression ratio affecting boost? Nada, cam timing can but SCR? Help me understand that one.

Knowing Ray has a 3.4 front pulley doesn't help unless you know the ratio of his rear pulleys. Oh, and I think SuperSub has a 8.0" crank pulley.

Has anyone done better than 12-14lbs of boost with a 2300 yet on any sized engine?

 

Well damn!

 

When dealing with a positive displace superchargers, Compression Ratio directly effects the amount of boost and power from the given boost. You have to remember that we are talking about pulley sizes and rotor rpms on a given engine package.

If you build a 9 to 1 compression 427 it will take a higher rotor rpm to acheive the same boost level as a 10 to 1 compression 427. This is the same no matter what the compression.

Why do you think all these factory LS3's are making such good power at the boost levels they are given. We did testing on my TBSS with the 10.5 to 1 compression 370 with L92 heads almost 2 years ago. We were able to give it as high as 17.5 psi of boost with the Front Inlet/Rear Drive MP122HH setup we just pulled off.

 

Ok, but I don't agree that boost measured in the manifold is affected by compression. I think your confused with cylinder pressure in your 427 9 to 1 or 10 to 1 analogy.

Edit.
Technically raising compression would raise boost by decreasing cylinder volume. But I'd think the effect of this would be marginal relating to a SCR vs DCR

 

WOT Boost is directly effected. We have worked with too many different packages and watched it happen. In the end build your engine the way you want.

Cylinder Pressure will effect it by making more power at the same boost level.

 

I agree that higher static compression will make more power at the same boost but can't understand why it should make higher boost if rpms and pulleys are kept the same!

Boost in a supercharger FI setup depends on pulley size and rpm compared to boost in Turbocharger FI setup which is affected by static compression since exhaust pressure is higher.

Anyway, my question now is; can the TVS1900 build a 10Ibs of boost on a 427ci engine. I have the option to go for 10:1 (72cc heads) or 10.5(64cc heads) by swaping heads and different gaskets' thickness.

 

I don't think your going to get to 10lbs with the 1900. With a 2.8 and a 8" crank pulley you might touch 9lbs. (I'm guessing) Good luck either way you can't go wrong. I'm kind of wishing I would have kept my 1900 and just tossed a 75 or 100 shot on top of it..

I'd go with the higher SCR setup myself

 

I forgot to mention that I plan on running pump gas and will not spin it that high, 6400 rpms.

 

Get the 2300 and be done with it. 1900 is too small for your engine. Boost for boost, the 2300 will spin slower and cooler and make more power than the 1900.

 

You can also open up your exhaust with headers (with all other variables static) and watch your boost drop 1 psi or more, while your RWHP increases.