i was woundering which one is a better mod to go with. i heard that Ls enigne can hold it’s turbo better then Ls/vtec. please give me some info on what’s better and why. Rebuild Ls or Ls/vtec turbo.
From reading up, and studying LSvtec, and FI vtec motors, I would say that FI stock LS motors will make more HP and TQ in different areas on the power curve, than LSVtec FI. (But not necessarily more HP.)
Depending on HP applications, with “lower” HP numbers, lower lift and duration is better because of smaller amounts of boost to tune on.
With appx. 300+ HP, on the stock LS, the turbo would begin to outflow the head, and then the camshafts become the bottleneck/limiting factor. (Hence the reason for Vtec cams.)
Also, considering that NA vtec motors have the middle vtec cam lobe to help increase the >100% volumetric efficiency, (that is, to get closer to 100% V.E. of the displacement), the Vtec camlobe becomes useless, until a certain point of ALOT of boost.
Considering that FI engines work above 100% Volumetric efficiency above zero psi of boost, having the increased lift and duration from Vtec cams becomes redundant. That is–until you start making ALOT of HP. (If I’m being a bit unclear, an FI engine will work above 100% V.E., the moment positive air pressure begins to enter the engine. Or 1psi > ATM. For example, a B18a1 at 10psi of boost, is operating at appx. 106% V.E.)
Also, because there are so many variables, that unless you have all of the control variables the same (i.e, turbo, boost psi, injector pulse width, etc…), and the only difference is the Vtec head, this would be difficult information to quantify.
Let me know if anything I said might be incorrect, or unclear.
-Andrew
aey think alot for the info. and from my understanding, the non-vtec is pretty good except the fact that it wont be able to get me more power when the engine has meet it’s max cap… right. hummm. dang, do you know of any other engine conversion or anything too boost up my car. please help me out here. thank you very much.
There’s alot of good info on this site. Just hit search.
-Andrew
Hmm
So if I stay with my stock ls engine and upgrade cams then it should perform nicely enough when boosted? (Assuming of course a few other necessary mods take place?
The cams will not have the biggest determining HP factor with moderate level HP. The turbo boost pressure will. The increased lift and duration help for an increase in volume, but not positive intake manifold pressure.
Often times, people who convert their engines from NA to FI, actually switch to lower lift and duration camshafts, for better tunability, streetability, fuel economy, and a more linear power curve. (Because generally, FI power curves are more exponential than linear, the momment boost kicks in.)
Come summer time, I’m actually ditching the CTR intake cam, and running both B16’s, int and exh.
-Andrew