Regarding the earlier comments touching on the subject of cam/valve timing, as Monty is predominantly a road car, and I'm now moving to Phase 3 cams, it's likely there may be some benefits waiting to be enjoyed by dialling in the valve timing a few degrees either side of Newman's suggested numbers?
On the Phase 2 cams, I've been able use the excellent idle management features within the EMU Black software to dial in a super clean 'drum roll' idle at 970rpm, closed loop ignition timing (scatter spark) and PID idle air control valve management helped me give Monty truly superb idle quality. I've been especially proud of this as idle tuning is one of the big challenges when fitting a more progressive camshaft profile.
However, before I pat myself on the back too hard, the truth is the Newman Phase 2 cams really aren’t that aggressive at all. Idle tuning is also greatly helped by my choice to use the Fusion Fabrications long runner inlet and steadfastly refusing to follow the herd by fitting ITBs that present many additional challenges in this area, challenges people selling the itb dream conveniently fail to tell you about.
While I will be continuing to use with the excellent long runner inlet with its well sized plenum and IACV, I am now taking valve timing to the next step by fitting Phase 3 cams. These Phase 3 cams are proper fast road spec so have more lift, more duration, and importantly more overlap too, all of which introduce additional challenges if I want to maintain Monty's refined idle quality.
However, there are a few tricks we can implement that can significantly help, for example:
1.
Retarding the exhaust cam slightly by 2 degrees will recover some of the idle quality as it effectively moves the onset of valve overlap above our new and very slightly lifted target idle speed of 1,000rpm, and couls also improve urban drivability at the low engine speeds seen during town driving
2.
Advancing the inlet cam 3 degrees from Newman's recommended number, will also certainly give Monty even more mid-range punch. This doesn't come for free of course as these valve timing stratergies will mean power will fall away earlier in the rev range.
Being completely honest with myself about how I use the car, I'm perfectly happy to trade 5-10hp or so at the top end for a strong pull in the 3,500rpm - 5,000rpm window to further enhance real world overtaking on the road. There's also good evidence to suggest if we time the PH3 cams as recommended, the engine will continue to make power all the way to 7,800rpm! In reality this is pretty wild for a street driven car, the top end power loss I'm proposing through the above small valve timing tweaks is also partly irrelevant anyway as I plan to limit the engine to 7,500rpm.
I need to be honest with myself about how often I will really take monty over 7,300rpm on the road, personally I think we'd be better off trading 5-10hp at the top end for a stronger mid-range pull, I'm still on standard rods and pistons so setting the rev limiter to 7,500rpm makes a lot of sense for engine reliability.
At the end of the day, what we’re creating here is effectively a Caterham 420 engine, but with further tuning via the ported big valve head. We are then dialling it back a fraction using the long runner inlet and less radical cam timing, the idea being to trade a bit of wild top end power for a far stronger pull in the mid-range.
Well, that's the theory
