Kenne Bell install

Ray,

I'm getting ready to turn in for the night but after rereading your first post, I would get bigger injectors so you don't run into any surprises A/F wise. That way you don't pay for a dyno tune session to find out you don't have enough injector then have to go back after you do upgrade. I'm running 10deg initial timing on my motor but you might be able to run more since you have aluminum heads. I don't know about 91 octane at 9-10lbs of boost. I always run at least 93 just to be on the safe side. Hopefully you should be ok with the 190lph fuel pump. There's calculators for how much hp a given pump will support also. I'm running a 255lph just to be on the safe side.

With regard to your fuel pressure regulator, most adjustable ones won't fit due to clearance issues unless you remote mount it. I'm running the stock one to no ill effect. It also removes one variable from the tuning equation.

Once you get everything working, you'll have a permagrin on your face.

From what I understand about the optimizer (and it's not a whole bunch I've never run one) it adjusts the signals going into and out of the computer to make fuel injectors of different sizes work with mass air sensors not specifically calibrated for them. Great solution for part power settings but at WOT all of your sensor readings and computer adjustments go out the window and the computer reverts to it's WOT fuel tables. Those fuel tables are set for the stock injectors. I'm not sure what (if anything) your optimizer will do in that case considering that the tables were designed with stock sized injectors and fuel pressure in mind.

Daggar,

I've lost sight of what we were discussing but I think we need to decouple internal compression and measured boost when we talk about roots vs. twin screw. Twin screw has internal compression (adds heat to air in blower body) while roots does not. You will see pressure at the outlet of the twin screw if it is decoupled from th engine while the roots in theory would not see pressure.

Roots has all its compression in exhaust manifold like you said. Twin screw is more thermally efficient than roots because since pressure in compressor body is greater that what is in the outlet manifold, the air charge expands and therefore cools to some degree.

The boost we see on the boost gauge is just a measure of the restriction of the air going into the motor.

Ray,

Try doing a search on the Corral in the supercharging forum. There was a thread on there within the last two weeks (i think) regarding using adjustable FPR with Kenne Bells. Which one are you trying to use?

5ptgo said:

Daggar,

I've lost sight of what we were discussing but I think we need to decouple internal compression and measured boost when we talk about roots vs. twin screw. Twin screw has internal compression (adds heat to air in blower body) while roots does not. You will see pressure at the outlet of the twin screw if it is decoupled from th engine while the roots in theory would not see pressure.

Roots has all its compression in exhaust manifold like you said. Twin screw is more thermally efficient than roots because since pressure in compressor body is greater that what is in the outlet manifold, the air charge expands and therefore cools to some degree.

The boost we see on the boost gauge is just a measure of the restriction of the air going into the motor.

Click to expand...

In a round about way I think we are saying the same things. About the only differences are our repsective views of where the largest amount heat in the air charge temperature is gained during the entire process. It's true that screw type SCs are actual compressors (meaning that the air does not have the choice back up or escape through where it entered the engine). That does cause a degree of heat of the air charge temp but is largely disipated by it's opportunity to expand when it hits the engine inlet manifold like you said. Your last line above here pretty much sums up what I think our discussion is about and is the "primary" though not the sole culprit of the amount of heat going into the cumbustion chambers. Ok... I think that part is finished.

I believe this started while we were talking about the reason for they bypass valves on larger blowers. The word I got from KB and confirmed by Bob Kennedy at Kennedy's Dynotune was that screw type superchargers are great blowers but terrible suckers. Centrifugal superchargers have created all of their boost by the time the air leaves the SC outlet and sends it directly to the TB. When you pull you foot off the gas that charged air smacks into the TB and over time can take it's toll on mechanical parts. The same can be said for the KB SC but not to near the degree since the TB is on the inlet side of the SC. For the smaller displacement of the 1.5L blower it's considered insignificant enough that a bypass valve wasn't required. The larger blowers move a considerably larger amount of air an required a way to recirculate a portion of the SC air when the TB slammed shut while the screws had time to slow. While the heat you mentioned inside of the supercharger itself may be a factor it's not a determining one since the 1.5L SC creates more of that than the larger 2.2L at all readable boost levels. Particularly when we talk about the 1.5Ls ability to make boost quicker at lower pressures (something I think you alluded to in an earlier post and I also agree with).

Daggar,

I think we can honestly agree to agree on 95% of all that's been said. The only thing I'm not sure of is thermal efficiencies of the 1500 vs. 2200 at mere mortal pump gas boost levels (8-10 psi). You're saying (I think) that the 2200 is more efficient (less added heat) that the 1500 at these boost levels and I think the opposite. Time to do so more research. Is the physical size of the 2200 the same as the 1500? If so, the difference in capacity has to do with the thread count of the screws, correct?? For a given boost level, does the 2200 uses a bigger pulley than the 1500?

Thanks,

5ptgo said:

Daggar,

I think we can honestly agree to agree on 95% of all that's been said. The only thing I'm not sure of is thermal efficiencies of the 1500 vs. 2200 at mere mortal pump gas boost levels (8-10 psi). You're saying (I think) that the 2200 is more efficient (less added heat) that the 1500 at these boost levels and I think the opposite. Time to do so more research. Is the physical size of the 2200 the same as the 1500? If so, the difference in capacity has to do with the thread count of the screws, correct?? For a given boost level, does the 2200 uses a bigger pulley than the 1500?

Thanks,

Click to expand...

I found this as part of an article in MM&FF where they bolted the 1.7L blower and 2.2L blower onto the exact same motor for comparison. This may help:

The benefit of the larger blower was that it is possible to move much more at a reduced blower speed. Less blower speed means a reduction in the parasitic losses associated with spinning the supercharger, not to mention a slight drop in charge temperature thanks to the increased efficiency. When it comes to positive displacement superchargers, it is always more efficient to spin a larger blower slower than a smaller blower faster. The smaller (faster spinning) blower will usually produce better boost response (at a given maximum boost level), but spun the same speed (with equal drive ratios), the larger blower will produce more boost throughout the rev range. The increase in airflow from the larger blower equates to more power. When you combine more boost with less charge temperature and a reduction in parasitis loss, you're looking at some pretty impressive power gains.

Click to expand...

MM&FF
September 2004 Issue Page 99

Using the same size pulley on both blowers, the larger 2.2L produced 4.3 lbs more boost (meaning both blowers werew spun at the same speed). So to answer one of your questions... for a given boost level the larger blower does use a larger pulley (spinning the blower slower to achieve the same boost). The screws themselves are physically larger in the 2.2 vs. the 1.5 and 1.7 versions. The valleys between the screws are larger as well allowing more air to be trapped as it travels along the screws towards the outlet end.

Thanks for the info Daggar. I actually have that issue and forgot all about that article. LOL!

5ptgo said:

Thanks for the info Daggar. I actually have that issue and forgot all about that article. LOL!

Click to expand...

You and I are in the same boat brother... I often forget more than I retain. LOL