Practical Dyno Tuning

Discussion and questions related to the course Practical Dyno Tuning

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would it be possible to be operating a car that is without using a stepper motor ( idler valve ) and have no issue of stalling once we give it a free rev or any load apply to the car (e.g Air cond load) or even after decel and free gear the car while coasting ( while slowly letting the car RPM drops to idle ).

If so , what are the methods that might to be used? increase more timing on the area where the rpm tends to drop? (e.g 200-500rpm increase more timing? and add more fuel?)

Raise the base idle by adjusting air bypass screw or throttle plate., if possible use spark feedback to help compensate for accessory load.

What exactly is the engine?

You can get reasonable control by using an idle ignition control function which many ECUs now offer. To get the best results you need to set a slightly higher hot idle speed than you'd normally use and then rely on the ignition control to pull the idle speed back to your desired target. This will still likely result in a low idle speed during cold start so you're not going to get absolutely perfect results without an ISC valve.

Arghx7 - Thanks for the responds.. will try to adjust the throttle plate opening. spark feedback? im using a haltech PS2000 on my car.. what option are the adjustable virables in the haltech?

Andre - the idle ignition control that you mean if i was going to use on the haltech PS2000 is the zero throttle timing correction right? at the rpm point where it tends to stall ( say below 500-600rpm ) increase the timing advance to get more torque on the engine so it wont stall? is this method correct?

owh, its a 2jzgte mk4.. the iacv valve are shot.. and the replacement are outrageous in pricing.. planning to go for a ford iacv valve replacement for the 2jz made by PHR soon..

If you are already going to get a new IAC valve I wouldn't spend much time on this unless you have to get the car running now. You will have to re adjust the throttlebody when the IAC valve is installed. When you adjust the throttle plate stopping position you need to check the throttle position sensor values. Make sure the ECU doesn't get confused about whether the throttle is closed or not.

From memory, on the Platinum Sport you want to go to Idle control-->Ignition correction.

Arghx7 - thanks for the input, i did slightly increase my throttle opening and raise the idle condition than normal, every free rev the car would go back to idle nicely with a slight dip on the rpm. the AC would cut in and a slight dip on the rpm. but to achive this, on the ECU option were only the zero throttle ignition timing map were to be used. if i were to use the ignition timing base map, the car would idle nicely but within 30 seconds, the car stalls for no reason (no AC or free rev) but once i enable the zero throttle timing map correction.. the car would not stall.. but except only to stall if the AC compressor kicks in after free rev.

1- the issue is the car would stall on after free rev (with zero throttle ignition map enable) with the AC on. Any free rev with out AC, only slight rpm dip ( almost stall)

2- the issue is the car would stall on after sometime while sitting on idle (with zero throttle ignition map disable) with or without the AC.

3- the car cant seems to sit at lambda 1 at idle, would suddenly shutter going to stall state. the car need to sit nicely at idle at 0.88 lambda. cams were not aggressive. (bolt on 264BC cams with stock springs). Using ID1000 with correct injector timing scaling according to base pressure being used at the moment ( paper comes with the ID specs)

any other input would be nice though.

Can you post a screenshot of your zero throttle map and your Idle Control-->Ignition correction map?

Bigger cams-->more overlap-->more unstable combustion due to internal exhaust gas recirculation, requires rich idle, or a higher idle speed, or maybe some spark timing change. I am not surprised.

I solved this on my car by looking where the load goes when it want to stall and put more ignition advance there... for example, car idle at 16 and the colum below is at 21 so it rescues from stall. In my case I could set a closed loop idle but... it was a pain in the ass to make it work properly so I did this direct way.

As Andre said my idle when car is warmed up is a bit high 1050rpm or so... but... there is no problem I think.

Arghx7- sorry for the delay, its been a buzy month for me.. i will update anything soon.. Hibernation mode at the moment for the car. im encountering other issues with my daily driven cars and need to sort the things out. will soon update any post on this issues and share the outcome.

Cool keep us updated.