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What are your points of view in dialing-in the best compromise on adjustable camshafts?
Turbo HKS (exact model unknown right now), used to run around the 800 hp mark previously, slightly laggy.
Camshafts HKS 264
Head adequately ported, Combustion chamber optimized, squish area standard, Standard valve size.
Pistons Wiseco asymmetrical
Block True blueprinted build
The client wishes for best everyday use , low end torque. I am familiar with the tuning strategies that can be applied to aid spool but my goal is to find the best "balance" of camshaft timing to satisfy the customer's needs without overly restricting top end performance.
I know that Andre has touched on this subject in courses and webinars previously, but I am looking to gather more in depth knowledge on the strategy of approaching this particular tune.
Thanks for sharing
I'm not sure there is any 'perfect' answer to your question as the best compromise is very subjective and is going to vary from one person to the next. Other than engines that I'm very familiar with such as the multiple 4G63 combinations we built over the years where I knew a base cam timing position that would suit my aims, I always start by dialling the cams in to the manufacturer's recommendations and then testing on the dyno from there. The general trend which I'm sure you're aware of is that advancing the cams will tend to aid low rpm performance, while retarding them will improve top end performance.
Personally I'd think the 264 is quite a mild cam for a 800+ hp 2JZ. It's certainly going to aid bottom end performance when compared to a larger cam but almost certainly going to strangle the top end in comparison to something a bit more aggressive. Again this all comes down to personal preference.
what I am after is the strategy. What you have said makes sense and I am aware of this. I am not looking for degree recommendations but rather how I best pursue and apply the methodology.
I figure this:
1. Take base runs with factory timing, neither advanced nor retarded on both cams.
2. Advancing the Intake cam, step by step.
3. Retarding the exhaust cam slightly
...after that.. I am unsure how to proceed because from previous experience I find it easy to get somewhat "lost" in determining what comes first.
Hi Dom, no problem, that makes sense.
Everyone is going to have their own angle on how to approach this but here's mine:
1. Generally the engine is going to be more sensitive to changes in intake cam timing so I'll start here. I make changes in 2 degree increments to gauge the effect of the change. It really doesn't matter whether you start by advancing or retarding as you don't initially know what the result will be.
2. After any change I always perform two dyno pulls and delete the first run. I've found this to give more consistent results.
3. If you see the sort of change you want, continue in the same direction. At this point we're only moving the intake cam.
4. Once you get to the point that you're seeing no further improvement, or you're going backwards, stop and move on to the exhaust cam.
5. I follow the same procedure with the exhaust cam and since we're leaving the intake fixed, this is altering the overlap. Continue until you see no further improvement.
6. At this point you should be fairly close to optimal however I'll also now advance and retard both cams together 2 degrees each way to assess the effect.
I've tried various techniques and while the above strategy isn't going to test every possible combination of cam position where both cams are adjustable, it is a commercially viable technique that's going to give you the best results for the time spent.
Thank you very much Andre!
Your reply is of great value to me and I trust to others too.
Is it possible to do this without a dyno?
for example if you made a 2degree change then do a road equivalent of a ramp run and record a log and you find its leaner down low and richer up top would this then show that you in move the power band lower?
I guess the biggest problem would be optimizing timing But I guess you could make adjustments until the power band is in the range you want it then go on a dyno and optimize the timing, this way reducing your dyno time/costs (for those without a dyno)
Cam timing is one of those aspects of tuning that I strongly believe requires a dyno. The changes that you're going to see, particularly when you're getting close to optimal, are just too subtle.
Your point is valid that a positive change in cam timing should improve VE and hence you would see the AFR move lean, but again the subtleties of how much change you'll see would make this very difficult to do with any real accuracy.
I've attached a screen grab of a Nissan SR20DET I was tuning at the weekend, this was the difference of 12 degrees intake and 10 degrees exhaust. They are by no means completely dialled in but have gained the customer enough top end power that he's happy with the results.
chris250 any details on the motor turbo combo?
surprised cam timing made that much difference, also is that crank degrees or cam degrees?
It's crank degrees.
The motor is stock except for a metal head gasket and ARP head studs, cams are Tomei procams with Tomei pulleys, turbo is a modified TD06 on a top mount manifold, externally gated.
Thanks for sharing !
Also remember if you are adjusting the cams which have a CAS attached to (honda b18 or Nissan sr20) you need to compensate for that in your base timing.
Good point Tommy! You could get yourself into quite a lot of trouble, not to mention see some confusing and potentially useless results if your base timing moves each time you adjust the cam timing.