Quote:
Originally Posted by PTAddict
It really is an amazing accomplishment making this kind of HP, pump gas, thermal management, and totally drivable. Crazy good. All on a production block and oiling system, as well.
Does the E67 ECU have any advantages over the E38 for this kind of application? Also interesting to note that you're running hybrid MAF/Speed Density - SD tuning on those ECUs is a PITA, at least with HP tuners, and I've found no discernable advantage in normally aspirated performance applications (the GM crate motor ECUs all run MAF-only as well). But it may well be that, at this HP level, that extra bit of fine transient control is important?
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E67 is needed for supercharged applications if wanting to maintain the same level of control as OEM. There are 3 MAP sensors (BARO, SC inlet and Manifold) as well as 2 IAT sensors (IAT1 in MAF sensor, IAT2 in manifold after intercoolers) and SC bypass valve control. E38 lacks the I/O capability to run this many sensors and have this level of control on forced induction applications.
MAF sensor allows more precise air measurement as well - when you think about it,
speed density calibration is
calculating the mass air flow from MAP, displacement and RPM to determine engine operation. Better to measure actual mass flow and redundantly calculate for better control.
Goal all along as we've refined these 7.0L SC engines has been not just power, but driveability, controllability and practicality (OEM part usage where possible for servicing, pump gas). Mark typically autocross's in 1st gear - not many 900+hp engines (well, none that I can think of) have driveability that allows this sort of operation.
We know there are changes that can be made to make more power, but what's the point if you give up the refinement and control? I think Charlie stated he got ~23-24 mpg in Mayhem on PowerTour this year (and I'm sure it wasn't because he 'babied' the car)- all while generating 880hp/815tq. On pump gas.
Anyone who can drive a stick could drive Hellfire - it is truly that easy to drive. Idles @ 750 rpm, pulls from any gear from idle speeds and never carries on in any way. Just be careful when your right foot gets heavy!
I'm a huge forced induction fan - and love turbocharging. But there is no way I can put together a turbo engine that has the same level of refinement and immediate response that we have with this positive displacement SC engine for same power level.
It's great fun making power (and can never have too much - although we are close.... Nah - just need more traction!) - but the fun stops if the package is unreliable, cantankerous to live with or requires unobtainium fuel, etc.
Dave