Dear members,
I have decided to do a N/a to turbo project. 1.6 SOHC 8V engine . Stock cam has duration at about 270 degrees and 9,5 mm valve lift both inlet and exhaust. stock engine has 7300 rpm limiter and makes about 105 bhp at 6300 rpm. Inlet - exhaust manifold will be built by me, engine will run untill 8500 rpm, turbo will be TD05-20G or 18G (that fits ok and will give max boost at about 4000 rpm). Questions:

I have read a lot of forum arcticles about turbo cam timing, turbo cam selection, etc

Some say that turbo cam must not have a lot of overlap because of scavenging, others say this is a myth, so what cam should i choose finally? higher Lift or higher duration oriented?

Another question i have is about adjustable cam gear sprockets. In this motor what is best to do? retard or advance? I am asking this question members with d16 turbo engines that has also one cam sprocket (like mine) and they might know what helped best for high rpm power. Theoritically i must choose retard timing, but i dont know how much. 2-3 degrees or more (7-8?).

thank you in advance,

Alex

 

which motor? every honda motor I have worked on has at least 16V even a D16. As far as overlap I dont think it hurts that much as my ITR cams do quite well, although most aftermarket turbo cams dont have much overlap, lift matters more.

adjusting cam sprokets is very dependant on the cam itself and engine setup there is no set number you need to find this on the dyno. I will say most OEM cams wont benefit much or at all from adjusting this

 

thank you for your answer, it is not a honda engne but i posted it here because there are a lot of experienced members here in cam and turbo.
I was thinking about the same thing, but i needed more opinions.

 

any other opinions about cam duration/lift and forced induction?

 

I used to run a 20G on my old Talon. Its an excellent turbo. Too much overlap can cause reversion issues especially if you have a poor manifold design. Depending on your HP goals and the flow of your stock head, the stock cams with a good valve train set-up may suffice.

 

seems the right thing to do. I will do good porting to the head and will try at first stock cam with custom adjustable cam gear. If i don't see a lot of drop in power after 7500 rpm, i might keep the stock cam.

There is also one opinion that i have found out and seems to me very accurate:

The main problem with turbo cam is if the turbo has a lot of back pressure. Old turbos like TB028, toyota turbos, etc, created more back pressure than inlet pressure so at overlap phase the exhaust gas remained in combustion chamber, not allowing a lot of fresh air to enter (making an EGR phenomenon). Thats why most after market cam constructors make turbo cams with wide lobe separation angles (early opening and early closing exhaust valve) and low duration to the exhaust cam.

But now a days modern turbos such as garrett GTX series and MHI TDs make less back pressure so there is no special cam for turbo: Whatever benefits N/A engine, will benefit probably the same turbocharged engine.

less back pressure will do also an exhaust manifold with long and wide runners before the collector.