WOT vs. Timing

[FreeBeeTony]

I backed my timing down to ~6* from 8* BTDC and my wot seems to have dropped to 4500 from 4800.........can 2* of timing have such an effect?
Had 2 people at 6*/4500 vs 1 person at 8*/4800........am I looking at things to closely?

 

[JustJason]

Re: WOT vs. Timing

sure can.... backing off your timing means that your giving up a couple of hp's at the top end... not a whole lot but just enough to cost ya few rpm.

 

[wca_tim]

Re: WOT vs. Timing

Perfect timing for this question... My answer is an emphatic yes. I'm curious why you backed the timing down?

My new 383 is running 4-5 mph faster wt 10 initial (22 advance which gives 32 at 4k rpms - I checked total timing to be sure the module was dead on). It also idles beter, throttle response is better, etc... That's with aftermarket cam, heads, intake, exhaust.... I've read everything from 32 to 36 total timing giving best performance and have been playing around with it a bit. I'm thinking it will probably run a little better still at 12 initial 34 total but am being very careful due to detonation concerns. It ran noticable worse across the range at 6...

this is a topic that I'd love to hear more about from those with more experience in tuning (not trying to hijack your thread... seems like the same kind of thing your thinking about...).

What an awesome day on the water...

 

[FreeBeeTony]

Re: WOT vs. Timing

I backed the timing down because I had some problems at WOT.....backfiring/popping through carb but I am almost 100% positive it was water in the fuel..........also worried about detonation............don't usually run more than 3600-3800RPM while crusing.........

 

[John_S]

Re: WOT vs. Timing

Tony,

I think you have the ignition from your 350Mag in your Rapido vortec, but don't remember what year, but think you have Thunderbolt V. If so, stock advance was 10 BTDC. The T5, and yours would have included a knock-sensor, has adaptive capabilities. Your ignition module was designed for the non-vortec head version, so running at 8 btdc is OK, but the stock 10 BTDC shouldn't hurt it. Also if T5, I'd run the merc knock module test to make sure it is working from transffering sensor/module to a different engine.

If T4 than 8 BTDC. Set it back to stock.

 

[FreeBeeTony]

Re: WOT vs. Timing

hey John..........

Yes, it's a T4.........will look at it this w/e..........

 

[wca_tim]

Re: WOT vs. Timing

have read a lot of your posts and know you got good sense. Also remembered what your engine set-up was. The timing thing in the range you're talking about is going to be incrimental, something else is creating the backfiring propblem. honestly, seems more like fuel problem or perhaps electrical problem if backfiring through carb at wot...

might check every wire and esp ground connections (especially since you just recently put it back together). If tothing there fixes it... what story do plugs tell. Hope this is helpful...

 

[FreeBeeTony]

Re: WOT vs. Timing

Backfiring is gone........after I did Don's trick with the carb, changed fuel filter/seperator and backed off timing..........but I really think the bacfiring was caused by the water/fuel problem, not the timing..........don't know if it's really neccessary or beneficial to readjust the timing to get the few RPM's at WOT because I don't run it there..........and isn't it safer to have a little less advance than too much?

 

[Bondo]

Re: WOT vs. Timing

Ayuh,....

I agree,.. the skipping,+ backfiring was a Fuel issue...

I'd set the timing to 8?,....

You don't just loose a few rpms at the Top,....
You loose HorsePower right from idle.....

 

[Maclin]

Re: WOT vs. Timing

In your case you seem to have noticed the performance fall off some when you went back 2 degrees so I think you are safe to bump it back up.


The 2 degree figure is what tuners usually go by. Move the timing up 2 degrees until the performance does not change then move it back 2. On cars it is easier to produce the same conditions to test the performance. With boats the water conditions and trimming adjustments can make a lot of difference from one run to the next so it is not as easy to test same-same.

 

[FreeBeeTony]

Re: WOT vs. Timing

Readjusted to 8*.........haven't tested yet........

 

[FreeBeeTony]

Re: WOT vs. Timing

Took a ride later on yesterday.........was definitly better but was not able to get to wot because of conditions........will probably leave it here......