Contour Enthusiasts Group Archives Forums Modifications Forced Induction cam timing vs. ignition timing

stock honda cams are set up to be very emissions and mileage friendly. i.e. not power friendly. that is why they see decent gains from adj.cam gears. SVT cams are quite the opposite. pretty hot cam for a street car. at least from the factory anyways. they will more than suit anybodies needs on a force fed duratec.
as far as using a stand alone system i can't answer your question. my guess is the cam position sensor and crank position sensor are what tell the pcm when to supply a spark and what advance to use. i do not know the details on this though. and i know there there is quite a bit more involved than that as well.

thanks zm that was where my question was geared to. i notice that alot of turbo charged hondas retard there valve timing a bit. just wondering why and if it might be benificial for some tweaking.

Cam gears can be very usefull. We don't have enough (more than one person) who have used them to know how much they help.
Retarding cam timing will generally shift you torque curve higher up the rpm range if done on both intake and exhaust equally. If you tune both separately you can adjust the width of the power band a little at the expense of quick drop-off in torque. Generally you can help fine tune the operational range where you want to maximize torque...within a small range based upon your base cam grind.
FI likes it if you use cam gears to make large torque bumps at certain rpms, can be done by chaning the intake/exhaust valve overlap since the cams are separate. THis just improves the breathing where the turbo is really efficient and makes for large power over the selected range. The range usually isn't very broad though.

Keyser uses adjustments in ignition timing and fuel along with a lot of boost. His big numbers have more ignition timing but require higher octane. Lower numbers are for street gas and essentially the only difference is ignition timing and boost level. Cam timing would allow him another degree of freedom in adjustibility.

thanks warmonger. much better explanation than i could have ever made.

What you are talking about Chode is efficiency loss from excessive camshaft overlap.

The point (more specifically the duration) at which the intake & exhaust cam overlap and the pressurized air flows right through the cylinder and out the exhaust port.

Excessive overlap is not a good thing but some overlap is not bad to make the car more streetable and it will produce a better overall power curve.

Also the valve timing points play a role as well. A turbo camshaft would want the intake valve to open closer to TDC then an NA cam.
Some drag turbo engines even open them at or after TDC and also even run negative overlap.

Either of those conditions would make for a piss poor street car though as off and light boost power would plummet dramatically. As would your overall power curve. I just stated them as a point of reference.

Ohh and Chode, not all supras have stock turbos. alot are NA. now i would bet money the na and turbo motors use diffrent cams. But thats neither here nor there.