ok let me know if im wrong, vtec functions better with high compression, more power…but in turbo, you lower the compression, so then would vtec turbo be pointless? i dont know what i wanna do…ill get 9:1 pistons and eagle rods, balance the short block… i just wanna know about the vtec, plus with vtec and turbo isnt it harder to tune cuz vtec messes with the airflow and all that?
thanks
i know its a bad thread so some guru;s please help me b4 i make a mistake
so is vtec really worth with a turbo or not, i hear it isnt needed
the reason is EXHUAST OVERLAP i guess when ur filling(forcing)the chamber with air and the exhuast valves are still open air goes right in and right out. Not all the air im assuming but enough and im sure its taking fuel with it. Note this is happening before burn. I could be wrong but thats how i always understood it. Just trying to help with the little info i have on the topic. Oh yeah and the fact ive seen vtec heads on ebay for 600+$ ready for lsvtec(tapped). With zdyne units going for like 900-1000$ fully adjustable from ur personal laptop. id rather have the gains of reliability and power from the zdyne units then raising my rev limit with our great R/S(:bs: ) to get the full potential of vtec. $/Hp/TQ ratio is apart of tuning in my eyes
The myth of high compression + turbo = bad is getting old. The real reason you want lower compression with a turbo car is that it gives you a larger tuning window, to hit the spot where you make max power. Higher compression setups will be very finiky to smaller changes in ingition and cam timing compared to a lower compression motor.
As for IF you should get a vtec head, you’re going to have to take a lot of things into consideration. First off, a stock vtec head will outflow a LS head no question. They also are designed with proper springs and retainers to run higher rpms. As for the downsides of running a turbo ls/vtec, there is the cost and extra work (not a whole lot…), you’ll be t-ing two oil lines off the back off the block (one for the turbo, the other for the vtec head), it will be a little tougher to tune, as most vtec turbo setups go a little lean at cross over since the increased lobe size. And you’re going to have to make sure you make the bottom end strong enough to take advantage of heads higher rpm capabilites.
If it was up to me, i would send a stock LS head off to portflow, where for $900 it will come back flowing better than a vtec head, if you plan for running high amounts of boost.
I remember reading on honda-tech some anit-vtec ls turbo people saying “With a turbo, you’ll forget what vtec even was.”
Personally, it doesnt seem worth the extra work to me, when a turbo ls has so much potentional anyway, but its really up to you!
-matt
EDIT: as for the overlap factor. Over lap is when the exhast valves are open for a moment while the motor is sucking in air. This is dictated by the duration of the cams. If you notice specific “turbo cams” will have a shorter duration then your typical NA cam. As for vtec cams and overlap, it seems that the stock vtec cams (b16a/gs-r) dont have a horrible amount, as this is what most turbo vtec people use. Its when you get to more aggressive cams like the ITR/CTR cams that people start to not reach their potentional. Also, overlap is something that can normally be reduce by a set of cam gears, and some good tuning.
