Quote:
Originally Posted by DavidBoren
My plan is to definitely use fuel injection. Probably just a LS2 intake for starters. But I am open to change it to optimize my powerband, for sure.
No horsepower or redline goals, as long as they're high enough to get me the torque I want.
Inch for inch, I think my undersquare six liter motor will be better than the stock 6.0L out of a truck, because the longer stroke should help power come on earlier (juxtaposed with the 3.6 crank), and I will have a higher redline. So, compared to the stock six liter LS, I should see my torque earlier, AND make power higher into the rpm range... with the proper cam, of course.
Even using a stock six liter cam and stock six liter tune, the 4" crank should give a noticeably broader and flatter powerband just because the torque should be showing up earlier, all other things being equal.
Note, I will be using heads ported to flow AT LEAST as well as stock six liter heads. So in a 6.0 vs 6.0 shootout, even if head flow, cam, intake, injectors, and tune are all the same, the only difference being undersquare vs oversquare... My undersquare motor SHOULD have a better (being broader and flatter) powerband with the same top end. If my heads flow the same, despite the smaller valves, and if the 4" crank doesn't lower the redline, then I will lose nothing up top compared to the stock (oversquare) engine. Yet I should gain a noticeable improvement down low.
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Quote:
Originally Posted by DavidBoren
I do have a question about optimizing induction to compliment engine design.
Do you play to the design's strengths, or use the induction system to make up for weakness
With a stroker motor, you should have all the low end grunt you need as an inherent feature of the design, so do you put a single plane long runner intake on it to help improve the top end, or a dual plane short runner intake to further compliment the low end torque?
Same with adding boost. Do you put a turbo on a high revving short stroke engine to use those extra rpms? Or do you put a positive displacement blower on it to make up for the short throw and add some bottom end?
Or, in the case of my proposed undersquare 359" engine, would a dual plane rpm air gap intake be best to really compliment that 4" crank, and get as much low end as I can... Or do I throw a single plane victor jr intake on it to try get a little more up top? Same question about boost. Trust that the long stroke will provide all the low end I need, and put a turbo to give me some top end? Or just throw a blower on it and have all the low end torque ever?
I suppose it will depend greatly on my intentions. However, I find it very hard to believe that I will require anything extraordinary in terms of the redline for this motor. The supercharged LSA has a 6200rpm redline, the LS7 has a 7k redline, so I will split the difference and establish a theoretical 6600rpm redline for the sake of this discussion. My calculations from the other page put a projected top speed of 166mph @ 6500rpms, which I am okay with.
Any thoughts on induction versus architecture in general? Or in relation to my proposed undersquare six liter?
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Just a few thoughts from your comments:
-LS6 intake is superior to LS2 for cathedral port heads. Difference is how they are made (LS6 keeps intake runners isolated from one another entire length, LS2 has small air-gap between upper & lower runner halves.
-Dual plane intake purpose is to increase vacuum signal to carburator. If injected, no reason to use (actually reasons not to use).
-Proper component selection will likely result in nearly identical power bands from either 6.0L combination. If limiting factor is head flow (even with larger bore), not much difference. Longer stroke means more dwell time (and therefore knock sensitivity) - so if running pump-gas, likelyhood of generating substantially more torque with longer stroke is reduced.
-Displacement will win over bore/stroke combination for peak power and bandwidth. 4" stroke 6.0L is 408" motor (if I recall correctly). Issue with 4" stroke on everything short of LS7 is bore depth - 4" stroke will pull piston pin slightly out of bottom of bore at BDC - not so great for piston stability.
-Either combination could turn to 7-7500 with right internals.
Need to turn to 7-7500 is dependent on cam, heads, etc.
-'Build' the combinations in Dynomation or other capable modeling software and compare. Program is much less expensive than parts (and can infinite number of combinations for free).
-Many people forget that the engine is a 'system' and neglect to select proper combination of parts for optimization.
-Assuming you have a 'limit' to your budget, you will be restricted at absolute optimization of all components. Again, that's why suggestion of running math models prior to parts purchase to see what is best 'bang-for-buck'.
-Forced induction requires same attention to detail as N/A. Either turbo or supercharged you need to look at everything and balance package for your intended usage.
-I always focus on breadth of powerband - and if for street use, who cares if you give up 20-50hp at top end to improve bottom end. You spend very little time at high revs (even on an aggressively driven street car). Example: We changed cam's in a build we did for friend of mine (built LS7). Gave up ~50 hp @ 7200 rpm for a gain of 100 #/ft @ 2000.
SO MUCH better overall package for his street driven (occasionally track, autocross) car.
-Glad to read you are not 'chasing the internet pissing contest of peak HP' - that's a sure way to end up with a pathetic combination that is miserable to live with on daily basis.
-One last note: The power curve I posted earlier was the result of 6 years of continuous optimization of our 7.0 SC package. 1st version made 780hp/830tq. Now @ 1010hp/1020tq. But devil is in the details - and takes time (and money!!) to ferret those out.
Dave