Righto, that other thread is not worth me commenting in but the interesting point was raised about VTEC (or any similar system i guess) with a hair dryer bolted to it.
Righto, my understanding was that with a system like vtec the timing is modified and the lift is modified to suit a NA system where the engine has to suck in the air itself, and therefore the effect of scavenging and maximum utilisation of the air's momentum is considered in the design.
On the turbo front, dont turbo cam profiles rely significantly on the air being forced in, and without the boost going then they are not that good at sucking air in.
I can imagine with forced induction and a system designed for NA then the cylinder would see very large amounts of air coming in, and possibly detonation from over compression as a result. Am I on the right track!
This is probably a good topic for discussion
jason_247,
Jan 10, 9:41am
at low boost the air behaves much like n/a and the factory computer with MAP is very sophisticated and can handle this easily.
at high boost the vtec can be times to kick in when the boost hits via a pressure sensor as thelow cam gives good bottom end torque withno boost and the on vtec iswell matched to what a turbo cam would be anyway
vtecintegra,
Jan 10, 9:42am
No reason it can't work if its properly designed (rather than just a turbo slapped on to an n/a engine)
Many modern performance turbos have some VTEC-like (or more advanced) system to adjust valve lift and timing
happylad3,
Jan 10, 9:54am
The brother of the foreman at work has a 600hp Integra. And the way he has the cams is different in the valve overlap. On an N/A you want a fair bit of overlap, to get a decent air charge in the cylinder, but turbo he closes the exhaust earlier and then the turbo compresses the boost into the cylinder instead of pushing it out the exhaust.
happylad3,
Jan 10, 9:56am
And his cams are just stock B16B type r cams. With adjustable cam gears to change the overlap/cam timing
tussocknut,
Jan 11, 12:53am
sr20vet.production turbo engine with vvlt.very similar to VTEC. other than the fact ya can't do it on grand turismo on the play station i don't know why people thought you can't do it.
Most of them allow a piggyback system to kick the VTEC settings in at set revs as well don't they!
So rather than get it all at once, the engine can change the cam profile in advance of the turbo kicking in. Instead of all of it arriving at the same time.
smac,
Jan 11, 1:28am
Variable cam timing and/or lift makes perfect sense for forced induction. Valves behave differently based on the boost being seen. Using the same profile both on and off boost will always be a compromise.
sr2,
Jan 11, 1:54am
We run variable valve timing and twin (parallel) turbo's on our 135i rally car, the combinaton sure works!
bwg11,
Jan 11, 2:25am
Not wishing to be pedantic, but it is not a case of "sucking" and "blowing", but simply increasing the pressure of induction air. In the NA case air is "forced" into the induction system at atmospheric pressure (14.7 psi) and once a turbo or supercharger is added, pressure is increased to say 24 psi (9 psi boost). None of the dynamics actually change - just the pressure of air to the manifold. The effect of variable valve timing is the same as in the case of natural aspiration.
timmo1,
Jan 11, 6:53am
Most modern turbos do.dunno about other manufactures but Toyota added VVT heads to its turbo J series engines in 1996 (1JZ-GTE and 2JZ-GTE)
unbeatabull,
Jan 11, 8:04am
My Twin Turbo '89 300zx has VVT, and as others have said most modern turbo cars do use Variable Valve tech on there cars, so there must still be a reason/improvement for them to be running it.
clark20,
Jan 11, 8:53am
That will be me and my nephew on Sunday, him bluebird turbo does 13.8, me 6.0L V8 hopefully about the same time! About time for more mods.
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