DIY_EFI Digest V5 #88

[dennis]

>The speed of sound (Mach 1) varies with the square root of the absolute
>temperature of a gas, NOT with its pressure. So--if it is NOT intercooled,
>you need somewhat longer runners to get the same effect. The pulses will be
>pretty well proportional to the density, thus stronger.
>
>You might also want somewhat larger runners--because the friction loss in a
>tube is also proportional to the density of the gas--but friction loss
>would be the same % pressure loss if boosted with the same size runners.
>
>Greg

>
*Thanks Greg!* My Encyclopedia Britannica said that too:) I just wondered if there was more to it than that. I appreciate the input! The car is intercooled, soon to be water to air intercooled. This is in a drag only car that will be using dry ice in the resevoir to supercool the intake charge. I have heard of people with similar setups actually getting below ambient temp at full boost the whole 1/4mile. I guess this would then negate the variables caused from the increase in air temp. Being an engine that will never see lower than 3500rpm, I am leaning towards shorter runners, something like 6 inches from valve to plenum is convenient, and a plenum that is 90% of displacement. Sound good?

dennis


>Greetings!
>
>I'm curious, what sort of racing, and what peak boost?
>
>Mike


It is a 1/4 mile drag race setup in a Dodge Charger Shelby FWD with an automatic. It is setup with 18-20psi depending on atmospheric conditions, gas available, and such. Best et so far is 13.43 at 102mph. We plan on running higher boost levels once we replace our air to air intercooler with a water to air one. Thank you for the interest! This is my father's car. I also have another similar car with a manual transmission that I just acquired for autocrossing and occassional club events on road courses. This is the car I was inquiring about the anti-lag system for, as we won't need it on the auto, it allows you to spool the turbo before you launch. The auto car is a drag race only vehicle.

Thanks,

dennis



>Hi!
>I have seen setups with 2 trottles ,one in front of turbo and one after.
>The compressor spinns much easier in lower pressure.
>This was on a dirttrack rally car.
>I have tryed carb in front of turbo and the adjustability of the output of
>the engine was much better.
>After the trottle is open I think the wastegate should be controlled by TPS
>possition.Adjusting the boost by increasing trottle. 
> Espen
>-

Espen, you've been quite helpful! I've heard of people using one way valves in paralell with the turbo charger before. This two throttle setup would do the same thing I suppose? 
My boost is controlled by throttle opening:-) 
Carbs and turbos scare me when mixed! 
I've thought of using an electronic Blow Off Valve that stays open while spooling the turbo on the line, and imediately closes when you let off of the brake in order to attain more boost off of the line. Currently, the car will push through the brakes, causing a red-light with anything more than 9psi. Although the boost gauge would read 0psi when this BOV is open, and I'm afraid of overspinning the turbo while brake-boosting. One of those turbine speed sensors would be cool, but they don't fit into my budget. Any ideas?

dennis

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