XtremeVette

I have been doing a lot of reading lately and was wondering...am I correct that boost starts to come on right around the 2500-3000rpm range and builds up with RPMs on the Centri units? Does the amount of max boost have a relation on where the boost would start being made or is that all determined by the particular pulley your running?

I was also curious if anybody had a chart/graph that showed boost levels at certain RPM's all the way up to max boost.

I have read so many posts and it just seems odd that many say...their boost is coming on at around 2500-3000 rpms but then there are others that say...they don't get any real type of boost until 4500-5000? Seems like a huge difference.

ajrothm

I really dont see much of anything until 3500...maybe 2 psi there...Around 4000 I am at 4-5 psi and it quickly jumps up from there..... By 6500 I am around 11 ish...

This is with a D1sc, 4.38" pulley and stock crank pulley. It would be nice to have more boost earlier in the power band for 3rd-6th but 1st/2nd would be even more of a waste then it is now...

XtremeVette

Thanks for the input...I hear what you saying...so hmmm wondering what 2psi at 3500 would equal in terms of additional torque vs stock.

I am guessing it is a game of play with the pulley's size to give your the best torque at a certain RPM for your particular application?

MawneeC5

You do feel a power difference at lower rpm. Once your boost guage shows positive pressure your car "gets up". It is progressive with rpm, but you can still have alot of fun just rolling on the power and staying in the mid rpm It wont be anything like positive displacement where the torque is instant, but that doesnt mean its nonexistent either
I actually had a small cam(not a blower cam) in mine which supplimented my low RPM torque a bit until the boost came on.

Carlmc1

Its too many factors to give you a straight answer because boost isnt boost. Its all about efficiency but generally speaking if you use a smaller pulley you will build boost faster and have more low end tq than if you use a larger puller. A smaller pulley will also give you more peak boost so you will need the right supporting mods or a way to limit peak boost.

Carl

DOUG @ ECS

Increasing the low end boost/TQ is the reason why ECS kits come with a restrictor plate for stock engines. That way we come much closer to making the same TQ numbers as HP, which is not common with a centri blower usually.

Josh@AandASuperchargers

Properly matching a compressor/blower has a big effect on how responsive it will be. Just ask the guys over at Vortech. They offer what's called a Performance Estimate Sheet. You can fill one out and their Engineers will match a blower for your application. They don't want you to use a blower that's to small, or too big for your setup. Typically boost on centrifugal comes on at 2500 - 3000 RPM because it needs to overcome vacuum. The centrifugal build boost off of engine RPM, the higher you rev the motor the more boost it makes. They all make peak boost at redline.

As far as charts that show boost levels at different RPM, look for dyno sheets that show boost. They will vary depending on the mods and how efficient the motor is.

XtremeVette

Thanks guys...Iam learning lol

Anybody have a dyno sheet with boost measurements on it?

robert miller

Love the YSI head unit... Robert

Mike04

YSi is great

Boost building depends on a lot of things such as SC size, pulley size, and displacement. Here is my 427 with a Vortech YSi. At 2500-3000 rpm I'm seeing 5-6lbs or so

I have used the ECS restrictor plate in the past to build boost lower in the RPM when I was running the stock block and a different SC..

4SFED Z

Damn Mike. That's sweet. Any vids?