Originally Posted by JjCoDeX75
Originally Posted by RWD_cossie_wil
Originally Posted by Chip-3Door
JJ, not with pistons going up and down we dont have, thats a terrible idea, a decent form of rotary engine would be far better!
Hence the invention of the jet engine
all four strokes of an engine in a line with no recieprecating parts
- look at the power they make
Mind you - its gonna be a stretch to get the cosworth to match that configuration with general tuning! ROFL
Okey dokey - shall be get cracked back into it - I know that some of our tech chaps will be Ringbound, so lets take advantage of them whilst they are still here!
Can we focus in a little on the cam timing? I want to see if we can shed a little light on this area of tuning.
Lets create another hypothetical. We have agreed now the following;
1. The bottom end is now configured for mildly low compression (i dunno say 7.2:1 - Does that sound about right?) All else is std - stroke, piston size, cc etc.
2. The clyinder head has been mildly ported - lets say equivalent to a Norris Stage 1?
3. The Turbocharger at the moment is to be say a T38 (I guess with a 0.63 zorst housing IIRC). I know that the popular choice would be the T4, but bear with me
4. The fuelling and mapping is a given, and will be correct for whatever setup we finally work with.
Now you will note that we havent referred to the cams as such. Having built my virtual engine, I now have a Boost threshold of shall we say 4000rpm or there abouts, and it is proving to be very unresponsive off boost. The car owner (Mr Blobby) has asked that
Jacobs independent car tuners (patent pending) set up his car to if possible reduce the boost threshold, and improve the off boost running.
So where do we start?
JJ
First of all we need to accept that any change we make to effect low speed running positively will nearly always result in a detrimental effect on high speed, and particuarly high boost running.
So, after our sombering acceptance, we look first at altering the lobe centre angle of the cams so that we can improve the bottom end response with the existing hardware (well, other than the addition of a set of vernier pulleys), a couple of degrees can make a big difference here.
with regards to where we go next with cams, well, it depends what cams are fitted, because if its the standard ones, you are pretty stuffed really, as you arent going to get the top end response if you go any more mild than that.
So i would imagine in this instance, if the cams are "wrong" its because mr blobby has read that BD16s make good power and has slipped a set of them in or similar.
But to answer the question you are trying to ask, the vital thing to getting good turbo spooling is to hit it with short sharp pulses low down where you have limited airflow, so a short duration camshaft is the order of the day here as a longer duration one will dampen the effect.