engine tuning question

[truggy83]

today I was running my Jato 3.3. I was running high speed passes with the body on. It was running around 190 degrees. Smoke was still visible from the exhaust. After running speed runs the engine would hang reving kinda high. If I hit the brake the engine stops hanging at high idle. The idle speed screw is set to the proper idle. I saw that a hanging high idle after a speed run normally means that the engine is running too lean. I let the car sit and idle for 1 minute and punched the throttle. The car bogged down before accelerating. From what I understand that means the hsn is too rich. So what gives, the car is hanging after acceleration like the engine is lean. Temps are somewhat lower than they should be and the car bogs down after sitting at idle like the HSN is too rich. Any ideas.

 

[Racer 1966]

If hitting the brake immediately fixes the problem then my mind leads me to believe your linkage is binding or servo is weak and you need a throttle return spring.

 

[olds97_lss]

Having it load up after sitting at idle is due to the LSN usually not the HSN. Having a high idle after a high speed run is usually indicative of the HSN being too lean and the LSN being too rich to compensate properly.

These may help you tuning:
http://www.rchobbies.org/cars_eng-tuning.htm
http://home.comcast.net/~98gmarquee/pics/misc/ParisRacingEngineTuningTechTips.pdf

 

[truggy83]

I noticed the HSN is harder to turn for some reason like it is gummed up or something. It is harder to turn either way. Also when the car idles it will idle pretty good but as it sits the idle drops down somewhat almost to the point where it sounds like it will shut off.

 

[truggy83]

also my tuning flow chart which I have says that I am supposed to let the engine idle for 1 minute and than punch the throttle and it should take right off. I have heard other people that let theirs idle for 20-30 seconds and punch the throttle. What do most people use? I would imagine if you let the car sit for longer and still be able to punch the throttle and have good acceleration, you would be running the LSN more lean than if you do it for 20-30 seconds

 

[olds97_lss]

10-20 seconds of sitting/idling is all they are really built to do. If you tune it so it can sit and idle longer than that and take off cleanly, it's more than likely as you suggest. Way too lean.