Goal: To build a "retro racer" type engine that is period-correct in terms of hardware but modernized in terms of fueling and control. Priorities are as follows:
1. Period correct looks and parts (1.6L, 8V, normal manifold)
2. High efficiency (high CR, low rotating mass, good fuel system)
3. Modern technology (EFI, Crank ignition, Knock sensing, closed loop EGO control)
4. High Torque (I know its tough without a displacement increase, but I like the peak powerband around 3000-6000)
5. Sweet feel and sound (square/oversquare, nice power ramp up to about 7000)
6. Under $5000 total engine build. And that's 5000 Canadian pesos...
Me: This will be my first time building an engine from scratch, but I have done headwork and engine swaps before. I have access to machining and fabrication equipment. I am very good at custom fuel systems, megasquirt, and anything electronic/programmable.
The car: My car is a 1980 VW Scirocco in excellent condition. It has a 1.6L EJ motor (83hp) with 160k and runs strong. It has a well supported chassis (bracing, suspension, brakes upgraded) but the powerplant is stock.
Parts I want to use: I would like to use my OEM block. I have a NOS 1.6EG Heron head. I have a mk4 exhaust manifold and a downpipe to match, and a 2.25" custom exhaust already mounted.
So, what I'm looking for is some advice on the following:
- I have sourced some Heron-style pistons, 80.5mm, with a 11.6:1 CR, from Techtonics. They are reasonably priced. OR they can custom build whatever piston for around $750. Since I want to stay at 1.6L, and realize quite large power and efficiency gains, the 80.5mm pistons seem right to me. What do you guys think?
- What else can be done to the Heron head to increase efficiency? What should I NOT waste my time with?
- The head currently has a G-grind cam installed (OEM). I am considering the Autotech 286. I want good driveability and torque, and I want it to freaking scream when I ask it to. I would like to avoid having to machine valve cutouts into the pistons if I can get away with it, so I need something with not too much total lift.
- 11.6:1 compression?. There is so much information out there on whether this CR is too high for pump gas. I plan to order an MLS head gasket from Cometic:
which are available in many thicknesses. Hopefully I can find a good combination which will net a decent CR and leave enough room for the valves with whatever cam I choose.
How do modern engines get a way with CR's as high as 14:1? Is there anything else I can do to the head and/or pistons to handle the higher compression? Perhaps if I run a very high fuel pressure and special injectors? Special Atkinson cycle cam? Some suggestions I have read is to use a long duration cam so that the effective CR is lower. However, this goes against the goals of high midrange efficiency and torque. I want to keep the throttle opening high at cruise to boost efficiency. I'll probablly initially build the motor with the G-grind cam. Since the EG makes 105hp stock, 120 or so should not be unfeasable with other modifications. Are there any other cam options out there with a good balance of reasonable lift and duration that are better than the G cam?
Hopefully we can have a discussion here, people don't seem to care much about small non-turbo engines anymore!