Boost Monitoring?

[Tony Corley]

I don't think they are limiting boost, just the way that you make it. Changing pullies should be illegal, same as running a cam over the specified lift is. But just like a cam rule, it's what you can do in between all the variables makes the difference. Any blower is going to have a limit of what it can produce, and specifying pulley size helps limit it. For the record. I have not raced Stock. but have a lot of experience with a power adder class that used to exist with a another sanctioning body that had very strict rules, similar to stock. Pully size was specified, so then it becomes a matter of reducing restriction, (porting was not allowed), and increasing rpm's.No different really than a naturally aspirated engine.

[Ed Wright]

I do some tuning for a couple of supercharger mfgrs. Internal impeller changes alter boost levels and boost curves, with no pulley changes. Anybody with any experience working with boosted engines know raising the boost makes much more difference than altering the valve job. If a boosted engine is classed with NA cars, boost levels certainly need controlled. DUH! :-)

[Tony Corley]

Which is why impeller modifications and pulley changes should both be against the rules. This is not rocket science, other sanctioning bodies have been running limited power adder rules for years. Blowers should be required to be as produced, along with mandated pulley sizes. Trying to mandate boost is a lost cause. With everything else being the same power adder wise, what if one guy figures out a way to turn more rpms? Boost increases. Less restriction, boost lowers, but power increases. Mandate the pulley size and power adder modifications, and hp increases are earned just like any other engine.

[Tony Curcio]

I believe it is already illegal to change or modify the impellers/rotors, that's part of what I'm on about. But I took a few minutes to check the 2014 rule book, and the only mention of superchargers in the Stock or Super Stock sections is in the engine blueprint specs, where a Whipple part number is specified for the COPO's and CJ's that are so equipped.

The boost sensor graph overlays the rpm graph anyway, so additional boost that results from more rpm would be easily separated. I suspect the CJ's will have the potential to eventually wind much higher than their Chevy or Dodge counterparts, but that's a whole 'nother topic.

Anyway, I can't help noticing that no one who actively participated in the FS classes last year has spoken up, so I guess they're happy with the status quo.

[kdanner]

Changing the cam profile or even just the cam timing will change boost. Your proposal to measure manifold pressure is just a proposal to measure a meaningless number which really is nothing more than a measurement of restriction in the intake tract. They'd like boost to be zero, power would be even higher then, as flow would be up. Physical inspection of the pulleys, blowers, etc to ensure they are the correct and unmodified parts is already the right approach.

[Tony Curcio]

Thank you, that makes sense. I was asking questions because I wanted to know.

The BTCC also mandates factory spec cams, more like Pure Stock than NHRA Stock, so maybe boost monitoring works for them for that reason.

[D.Johns]

Like stated the boost is a measurment of back pressure with-in the system. A supercharger will not spin faster or slower in order to regulate this pressure like a turbocharger would. That system uses a waste gate to bleed off the exhaust pressure in order to change impeller speed to maintain a certain boost pressure in the intake manifold.

In a supercharged set-up there are several ways to change how much air the supercharger will move. Most of them are checked in tech... It's up to the competitors to figure out how to make more HP given the set rules.