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Old 12-21-2009, 05:08 PM   #62
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Join Date: Sep 2007

Originally Posted by J Howerton View Post
We have done quite a bit of intensive data logging(I won't bore you with the details) on roots SC cars and some on centrifugal's, and same as turbo cars, it can be very application specific.

One rule of thumb that seems to hold is boost based water/meth systems on roots cars are difficult to get the most out of. You can get a high percentage of max boost near instantly at low RPM. So you have to either set the boost based systems to spray correctly in the midrange, in which you are lacking in some jetting on the top end giving up power, or you jet correctly for the top end and drown out the midrange losing TQ. The roots cars really like an IDC based system to meter injection though the entire rev range, or at a minimum a MAF based injection scheme.

Where you put the jets and what mixture you spray then gets more car and power level specific. I do agree with Snow, the roots cars put out a lot of heat and can tolerate more jetting.

We have found that too. We started going with MAF based injection on positive displacement setups and also quick spooling turbos years ago because of the need to have a large jet without bogging on the low end. A boost based system can still be very effective, but it is a bit tricky to dial in and find the happy medium. This is one reason we also do a PW/Boost referenced system in so many applications as well.

I will look over the charts as time permits Its not a matter of patience, as I love that stuff. It's just trying to get everything done as the year comes to close.
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