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Originally Posted by CallMeCrazy So going by your motor which is 4,900cc or roughly 299 cid (not sure what your redline is??)
(CID × RPM????) ÷3456 = CFM
(299 × say 6000?) ÷ 3456 = 519.10 CFM
The engine will flow 519.10 CFM of air assuming a 100% volumetric efficiency and assuming a common redline of 6K. Most street engines will have an 80-90% VE.
519.10 × 0.85 = 441.23 CFM
Your 299 cid would flow 441.23 CFM with an 85% VE. A good rule of thumb is that for every 10 hp a gasoline engine makes, it needs roughly a lb of air/min delivered to the intake manifold, so, you'd multiply 441.23 CFM by .07 giving you 30.89 lbs/min and putting your motor at roughly 300 hp naturally aspirated, am I right?
Add in pressure ratio, you said 6-8 psi?
(6 + 14.7) ÷ 14.7 = 1.41:1 pressure ratio. Looking back at the RHC6 chart, you'd be operating on the low end, BUT, I still haven't figured out the density ratio. If you give me your redline and your plans for the motor (how much are you looking to get out of it and at what boost level?) I can figure out where the turbo operates most efficiently.
I still need to come up with a compressor map, but bear with me, I have a lot going on right now. |
The redline for the 4.9 liter is 5200 RPM's. As for the amount of boost, I want no more than 6 psi when all is said and done.
Some 4.9 liter engine specs:
200 hp @4100 RPM's,
275 lb/ft @ 3000 RPM's,
Shift points @ 4900 RPM's.
I'll have to dig up the cam profile if it is needed. Let me know.
Basically I would like to add a few hp above the 4100 RPM line, and not let boost come on till about the 2500 RPM line. I'll scan over everything you've supplied and see if I can't do the compressor map myself for my particular turbocharger. But please, feel free to beat me to it...
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Originally Posted by N0DIH My point early on in this thread is with a high compression 4.9L, you DON'T want to make it efficient until high rpm. The high compression and boost will destroy weak pistons like 4.9's have. Be careful. I would recommend not hitting more than 2-3 psi until above 3500-4000 rpm.
Unless you drop the compression I don't feel you will ever have a good running 4.9 Turbo. |
Tom is right Stoney. We want the high end power and keep the natural low end torque for now. I just hope this diesel turbo does the trick...
As for the compression ratio, I've thought about taking the heads off and giving some more room in the combustion chamber area. That should lower it some...