Quote:
Originally Posted by mikels
I'm raising the BS flag very high for anyone 'realistically' making 650 RWHP with a 6.2L @ 12 psig even with cam & CNC heads. The math just doesn't support it. Neither does the dozens of SC engine combinations I've worked with.
An otherwise stock LSA with 12 psig will make 625 CRANK HP in my experience - but like I said, the lower compression allows better spark timing resulting in this power level. I've done many, many LS3's with same boost that will not clear 600 HP due to knock sensitivity with higher compression. An engine is a system - not just a pile of parts. All need to be considered together to optimize capability.
Remember - properly calibrated dyno's don't lie, but dyno operators do. And chassis dyno's are all over the place. Great for doing A vs B work - but horrid for absolute numbers. Changing your tire pressures can result in 20 HP (more with bias tires). Tell me the airflow rate and/or fuel flow rate and I can tell you how much power you can POTENTIALLY be making.
Thicker head gasket to lower compression - BAD idea! Ruin the quench in the chambers and make engine even more knock sensitive than it was with higher compression. Dished pistons for lower compression always keep quench of chamber for better flame front propagation.
Reason to run lower boost with cam and maybe CNC heads: Better adiabatic efficiency. You stated you want to road race this combination - not gonna happen with 12 psig on stock compression ratio. Well, at least not making full power for anything more than part of lap 1. Plot where you are asking SC to operate on compressor map and look at drive losses & adiabatic efficiency then figure out how many kW cooling system you'll need for not just engine, but intercooler as well. Best to optimize efficiency to get the power. Drag racers can get away with some crazy crap (and can run air-to-ice intercoolers) - but they have no duty-cycle to contend with like road racers or even Auto-X.
If you are running an LSA SC, why not run LSA CTSV accessory drive? I assume you are talking old (2004-2007) CTSV accessory drive - which means you are limited to 6-rib drive belt - for everything including SC (unless re-pulley everything to 8-rib - more $$). 6-rib will not drive the 1900 TVS SC without slipping @ 12 psig. There is a reason factory drive is 8-rib (and that is for SC alone).
Yes, VVT can broaden torque band. But with a positive displacement SC - you'll have all the torque band you'll need. Up to you - but I'd ditch it.
Yes Thomson can calibrate any of these combinations - I do most of their calibration work so I can answer that.
Matt @ Sled Alley does exceptional work - reason you see Mark's cars there frequently. He also has a '67 Camaro we did a 418 SC engine for that made great power. And an old Caddie with an LSA in it we did.
Dave
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I can't vouch for their dyno's, hell could be just internet boasting of RWHP. Also likely they're tuned pretty "risky". I was more concerned on have they popped or not and how many miles... And I'd be doing rare HPDE's so not real road racing I'd say. I've read your threads on Mark's cars...I'm not at that level of use so my cooling will be much more street than track.
I just talked to Matt and recommended I talk to you actually and I mentioned I think I was already lol.
I am talking about the GMPP CTSV FEAD, there's a part number that puts the alternator up top like a vette but is otherwise the same. It's 8 rib for sure.
http://paceperformance.com/i-1999062...em-w-o-ac.html
So I have access to the engineer for water pumps (we can all put together location and guess where I work haha) and unfortunately it's been years since he worked Gen IV stuff, but we determined that anything that definitely clears the VVT cover is truck spacing. However, he said there is sufficient material to possibly create clearance in the back of a CTS V pump, but we weren't sure how much needs to come out. I'm going to try and look at the math tomorrow. and see what's possible.
So assuming I can solve the water pump issues, but am stuck at 10.5 how much power would you guesstimate at stock LSA 9 lbs vs 12 (stock L92 heads, LS7 throttle body unless that's limiting too)? How about then with a LS9 cam and no VVT same two options? Which leads to what's the gain on dropping below 10 (or whatever's optimal) w/ dished pistons? I didn't want to take apart the short block but everything's about tradeoffs right?
Thanks again, sorry for so many questions... Just kinda wanted to figure out how to be "first" w VVT and FI, but if not worth it it's not worth it. Like I said if I had the dough a LS7/2.3 blower setup would be in the works haha.