e-85 ignition timing

[adamsvega]

gentlemen i just finished a long and extensive course on engine tuning .we covered carbs ,injection ,boosted ,n/a ,and mostly fuels and ignitions ........here is a breif hit on this topic .

alcohol based e-85 fuel and timing maps need drastic changes v/s gasoline ...duhhhh

alcohol base needs up to 2x more idle and off idle ignition timing with a fast ramp from cranking speed to idle .........ok thats new

a very slight slow ramp/curve of advance is needed to max @mid rpm and a same slow retard curve with higher rpms ......hummm

as load increases alcohol base needs 3/4 less retard than Gas

in a nut shell it looks that optimal spark timing at a min. can be locked out for peak mph. with the use of a start retard.

optimally we can set distributor curves with less mechanical advance and more initial . for the same total ..what needed 18 btdc and 20 more advance on gas would be better served with 28 btdc and 10 more in advance

if programmable we can flatten out our curve just past off idle and trim back the same amount when acceleration rise in high gear is reached .

optimum pk tq. and h/p numbers are reached with the shifting and flattening of this curve .
where as gasoline wants a sharp bell curve we want a dinner plate upside down.


more to come on air bleeds and the aftermarkets throttle plates and blocks!

[rosco15]

If you don't have more timing at idle what happens?

I always thought you wanted more timing with E85. Your saying less total advance.

[adamsvega]

Less lead @ idle will cause a lazy climb in rpm comparatively. as it needs more time to develop more heat to get to max cyl psi at 14deg. past tdc ......not less total timing just more base and less advance .
basically it wants it early and more constant as a low afr stoich fuel . once it gets happy it does not need a fast rise in timng curve to accel .
the object of any engine tune up is to bring together a combination to have peak cyl. psi at 14deg. past tdc for any given rpm .....so with out variable time, lift,duration and overlap we have to set up a engine for a range of efficiency and maximize it in that band and band-aid it everwhere else .
if we build our psi early it will work harder and cause pumping losses as the piston is moving up has more resistance . so the faster the flame front can travel across the chamber the less lead required . read that as hemis and bbc open chambers are very inefficient at high compression do to the dome .and need lead.......... this is bad as it makes the tune up for max power very tight and disasterous when too much ...this atomosphere in the combustion chamber is very hot and high psi early and can cause detonation this spikes the cyl and causes it to be so hot so fast that it pre ignites causing it blow a hole in the piston ........lower power out put and small chambers can ping alot and last a long time in this condition .plus it can be heard as the audible sound is a warning to back off .....pre igniton will kill it asap . . the lower the angle of the valves and tighter the chamber the closer ideal is with flat to a small dish piston .....oops i'm rambling

[overdriv]

Jan 10, 2010 13:54:47 GMT -5 adamsvega said:

Less lead @ idle will cause a lazy climb in rpm comparatively. as it needs more time to develop more heat to get to max cyl psi at 14deg. past tdc ......not less total timing just more base and less advance .
basically it wants it early and more constant as a low afr stoich fuel . once it gets happy it does not need a fast rise in timng curve to accel .
the object of any engine tune up is to bring together a combination to have peak cyl. psi at 14deg. past tdc for any given rpm .....so with out variable time, lift,duration and overlap we have to set up a engine for a range of efficiency and maximize it in that band and band-aid it everwhere else .
if we build our psi early it will work harder and cause pumping losses as the piston is moving up has more resistance . so the faster the flame front can travel across the chamber the less lead required . read that as hemis and bbc open chambers are very inefficient at high compression do to the dome .and need lead.......... this is bad as it makes the tune up for max power very tight and disasterous when too much ...this atomosphere in the combustion chamber is very hot and high psi early and can cause detonation this spikes the cyl and causes it to be so hot so fast that it pre ignites causing it blow a hole in the piston ........lower power out put and small chambers can ping alot and last a long time in this condition .plus it can be heard as the audible sound is a warning to back off .....pre igniton will kill it asap . . the lower the angle of the valves and tighter the chamber the closer ideal is with flat to a small dish piston .....oops i'm rambling

I understand what you are saying but it seems you contradict yourself. In one paragraph you say the timing needs to come in early to build pressure and heat, then you say if pressure/heat comes to early it is bad. Are you talking about that fine line between ok and disaster?

So do you have any starting recommendation for a ignition curve for a 14:1 BBC? I will have a programmable MSD 6AL-2.

[timwilliams]

Adam, I love reading your posts.

I have a programmable 6AL-2 and a normal 7AL-2. 13:1 406...

So what shape would you expect a good curve to be for me?

With the converter I am only running 5500-7200 RPM.

[adamsvega]

believe it or not this all stemmed from a symposium on h/p that i have on tape most of the ethanol stuff was done by nissan and banks they were quoting alot of college and corporate engineers and they all came to the same conclusion .
the higher the ethanol content the higher the curve starts and the less ramp it needs and the less retard with load was required .....this as they put it was a dinner plate upsidedown in 2d and wave with out crest in 3d for the whole map ..... ideal is to flatten your curve you have and raise initial back to your old total . then raise lower first (rasie second)the total and see if mph goes up then shift the peak forward (then back) and see if et goes down then lastly shrink (then lenthen) the platue to min. et

[madmax404]

I have tried timing from 28-45 degrees with no difference in ET(sbc). I would pick up 60ft but slow down finish line and vice versa depending on which way altered the timing. The problem I had was very bad kick back when we had the timing advanced at 40degrees and above. Kick back only happened when we initially fired for the first time in the day(after sitting a week between races), and when I tried to start the car if the temp was above 160degrees.

Now on Dyno, I showed these same gains and drops. Low end hp would take away high end hp and high end hp would take away low end hp more so than when we tested with gas/alky. There is a very very fine line with Tuning E85 as far as timing goes. I have a dyno session coming up in 3-4 weeks and we hope to mess with timing events in a little more detail.

Anyone running a sbc I found at 38degrees(locked down) was when we had our best(well most even between low and high end) performance.

[timwilliams]

Jan 11, 2010 6:52:24 GMT -5 adamsvega said:

believe it or not this all stemmed from a symposium on h/p that i have on tape most of the ethanol stuff was done by nissan and banks they were quoting alot of college and corporate engineers and they all came to the same conclusion .
the higher the ethanol content the higher the curve starts and the less ramp it needs and the less retard with load was required .....this as they put it was a dinner plate upsidedown in 2d and wave with out crest in 3d for the whole map ..... ideal is to flatten your curve you have and raise initial back to your old total . then raise lower first (rasie second)the total and see if mph goes up then shift the peak forward (then back) and see if et goes down then lastly shrink (then lenthen) the platue to min. et

OK, let's pretend I am some dumass who can't read this...

What about: Say I have 26 degrees running around the pits... flat until 3500 where it ramps to .. 32 with 36 in by 5500 (my stall speed) maxxed out to 42 by 7200 (my top RPM)??

ok, there's your clay... mold me a nice one! ;D

13:1 no power-adders!

[adamsvega]

overdriv---- that is the problem with hemi,s and big open chambers /bbc and domes you see a great advantage to adding total time and a drastic ramp at pk numbers when you get close it adds alot of power but the top is a pin head and it falls off fast into distruction . most motors on e-85 need more time down low but very little extra total is required at wide open over gas . also the gains people see by retarding timing on gas under load/top end will not require as much . hope this clears up my ramblings ........Baily's will do that

[adamsvega]

move your whole curve down in 500 rpm first this will get your timing at stall up about 2-4 deg. . if no change in snap up on trans brake and 60 ft. keep going bringing in curve early . when it runs its best et then add some -2 retard after 1000ft rpm with your high stall you are almost out of the need for any curve except for leave and pits drivebility .


all in by 6000 _____________________same total ___ -4 retard
_+4_____/

[timwilliams]

-2 at 1000? I'd be in the corn field We race 660 feet! 1/8th mile!
haha

I was going 36 total most of the time last year... you think 42 is likely closer with these Dart Iron Eagle heads?

[adamsvega]

ya got me !!!! timming at stall is 36 deg @5500 and you cross the traps at that rpm/time ? huh
you running a circle track one speed? or not enough gear to get back and lock up converter by 1/8th