MSefi.com read only forum (Jan.15,2018)

I need some feedback from some of you guys with tuning experience. I have a 406 SBC in my dragster with an pretty agressive cam. I am worried that it may be difficult to get it to idle with a SD control algorithm. Drag race only application, running on methanol, 120 lb/hr low Z injectors. This engine was dyno'd at 700hp with a alcohol carb., and it had a pretty nasty (lope) idle. It now has an individual runner intake

here are my cam specs:

Lift 6.90, 6.38
duration @.050 282 deg IN, and 292 deg EX
adv. duration 318 deg IN, and 326 deg EX

Individual runner intake - so, like, 8 throttle plates now? I'd run straight Alpha-N. I struggled with SD for a long time on an ITB engine, and now I'm running straight AN.

Yes, 8 throttle plates. i do not think i will go with straight alpha-N as if i were going to do that i would have just stuck with a mechanical injection, alpha N is just a mechanical setup with electronic injectors in function. There has to be a way to make it work with SD as kinsler and others make and sell a similar setup that works on SD.

SkinnyG, What was the problem getting it to work with SD?

If you search the threads for the synchromap topic you will find many posts on the problem with ITBs and a circuit that can be built to reduce them. There is also measured data from Bruce and others to back up the improvement that might be expected with this circuit.

grippo wrote:If you search the threads for the synchromap topic you will find many posts on the problem with ITBs and a circuit that can be built to reduce them. There is also measured data from Bruce and others to back up the improvement that might be expected with this circuit.

Thanks for the tip.

Some things i have found to be unclear are:

Discussion has been about 1-4 cylinder engines and how bad the Map signal is, even when multiple cylinders are merged together, is it as bad with 8 cylinder engines?

Discussion has also been mainly about the idle signal, i assume as the RPM goes up, the signal smooths out some (when merged together), at what point does this happen (if at all)?

what benefit does this have over a blended alph-N/SD control?

i am just trying to figure out if in my application if this is really going to benefit me much over a blended AN/SD control algorithm as i am not going to be fighting with low end drivability, (besides the fact that the engine idles erratic with a carb and standard intake)? any info would be helpful.

JAM wrote:SkinnyG, What was the problem getting it to work with SD?

Atmospheric pressure where I am is 94kPa.

Cruise is 93kPa

WOT is 94kPa.

If I datalogged a run with a lot of cruising, it would often be too lean when I'm more aggressive. If I datalog an aggressive run, it would be too rich when I cruise. I have a very solid MAP signal (stock cams), but I could not blur the lines between cruise and WOT very well.