Using Vacuum Advance With FiTech Controlled Timing
Hugger 1,
I'm trying to do the same right now. Just converted over to ignition control after 3 years running without.
During that time I ran full manifold vacuum and it worked wonderful. But I had to learn how to tune efi. It took a while.
So now after changing to full ignition timing I'm having problems. So I took your advice and have been running it without vacuum advance. Even though it's running pretty good now it's not as good as it was with mech. and vacuum advance. What I'm noticing is my engine runs hotter - 10* to 15*. Residual gas residue igniting keeps popping out of my sidepipes from 2000 on up when I shift. Plus it's popping worse now than before the change.
I need some help. Can you post your Spark Map Settings so I could compare. About Breakpoints - did you change those settings to match one of the curves for the MSD dizzy - could you post those as well.
I also need a bit more clarification on how to get the rotor properly phased with vacuum advance.
How's your engine been running - good or better with vacuum advance - or have you had any problems or hurdles.
Here's what I have. Engine: 427 ZL-1 - 550HP aluminum block from Chevrolet.
Comp Cams solid roller with a good amount of lift and duration. (ran real smooth before change-over).
MSD 6AL and MSD 8272 tach drive w/vacuum pod. 14* initial, 20* idle, rotor phased at the zero mark (dead center)-I'm surprised because I tried it in a number of positions but this is the best. I can use a regular rotor if I want but I'm not because I still want to play with it for a while.
Fitech 600 efi. 30002.
Also, the vacuum can I use is B-28. Comes in at 8" Hg and produces 16* at the crank similar to yours, I believe.
I really want to get this squared away or I'm going back to mech. and full vacuum advance. Any help greatly appreciated.
Thanks,
65-StingRay/Wayne
Today I went for a cruise to see how it's running after all the tuning I did yesterday. With vacuum disconnected it ran a little rough but seemed OK but not exactly right. So I pulled over and plugged in the manifold vacuum line and engine seemed to run a lot smoother. Went back in car and brought the idle timing in the spark map down from 18.8* to 14* to match my base timing. Drove it for a few minutes to observe how it ran. Improved throttle response and the incessant popping and backfire are now reduced to almost zero.
Came back to the garage and checked the rotor phasing. The rotor did move to the retard side of the of the number 1 cylinder post. A couple of adjustments to the phasing and I'm almost perfect on rotor alignment. Still may need a slight adjustment maybe 1* or 2* degrees. Rotor cap is now at the 7* mark - may end up at 8* or 9* on rotor when finished.
Still not sure of how much I'm going to make changes in the spark map. This is where I now need a little advice.
Going for a drive to see if I can sort any of this out.
65-StingRay/Wayne
Hi Wayne, I'll be happy to work with you on this. I'd like to start off with some questions/comments. Sorry for the long winded reply, but I'm also wanting help others that might read this.
- Could you please confirm that when you apply vacuum to the canister the plate the mag pickup is attached to rotates counterclockwise (Chevy) and that the rotor does not move? Given that others have said this will not work, I just want to make sure the dizzy you're using works the same as the one I'm using. The rotor is locked to the shaft that has the 8 blades and the plate moving counter to the rotor rotation means the spark is triggered sooner (advanced).
- Sorry to ask, but you did lock out the dizzy...correct?
- Are you having the issues with the vacuum advance hooked up or still running without? I mentioned in my earlier post making sure it was set up properly without vacuum because you want to make sure the base, initial and VR Drift setting are correct. These need to be set correctly to include the VR Drift at 4K . And you need to make sure you've followed the FiTech steps to ensure the handheld is reading exactly what the timing light is showing.
- Did you happen to write down the timing specifics for when you were running the mech. adv and vacuum? If it was running well, that's the curve we'll want to replicate using the FiTech to essentially replace the mech adv portion. You would have needed a degreed balancer and timing light and had someone hold specific RPMS with vacuum advance disconnected to see what the actual mech curve was. If unknown, what curve are you wanting to create?
- You mention 14* initial, 20* idle; are those the "base" and "idle" settings showing on the handheld? Are these the settings you're using with the vacuum hooked up? If so, I'm guessing you have too much advance at idle (20*+ 16* = 36*)
- What is the altitude where you live; I'm in Albuquerque, NM at over 5500' so my engine likes lots of timing. The 14* initial might be too much where you are, unless that's what you had just running the mech adv and vacuum.
- What is your vacuum at idle? Is it enough to permit full vacuum advance at idle with the vac canister you're using?
- What is your cruise RPM?
- What are your current MAP and RPM breakpoints and do you have the latest software loaded on your handheld and ECU? I only ask the last question because I'll be looking at mine and want top make sure we're seeing the same thing. The RPM breakpoints are the important ones because the vacuum advance is adjusting for changing MAP/vacuum. If the system is running good, we don't really want to change the breakpoints because the same values are used in both the AFR and SPARK tables. You can see that if using the ProCal software.
- I also had great luck with the mech adv and vacuum, but wanted the idle smoothing the ECU controlled timing brings. The rapid ECU spark adjustments can manage the idle RPM better than just IAC/AFR adjustments; that's working well on mine. It's also nice being able to look at the handheld and see exactly how much spark advance the system is providing at a specific RPM (does not show what additional advance the vacuum is adding). The point of that rant was that if you weren't having idle issues, using the ECU to control timing may not have any real advantages. Others may know of other advantages.
- Did you read the paper the GM engineer wrote on SBC timing? Good read just to have the basic concepts understood as we're working through this. And did you watch the MSI YouTube on rotor phasing...also good refresher as to why the rotor needs to be phased.
- Are you using the ProCal software or just the handheld to make CAL changes? Are you comfortable making changes to the .inf files on the handheld so it reads the same as your breakpoint settings?
- Lastly, what is the airspeed velocity of an unladen European swallow? 🙂
Hopefully we can get this working for you...
Cheers,
Rick
Sorry, was writing when you were replying. Yep, you had way too much advance at idle...my base and idle are also at 14*. Glad to hear that one change helped...even without my help!
Are you using a cap with a hole cut in it, or a clear cap to check the phasing? As to the spark map, just forget the MAP and focus on the RPMs. So the low, med and high inputs will be the same no matter what the MAP is. Or, you can play some and have the advance come in a little sooner for the WOT lines. If your WOT RPMs are the stock 1100, 3000, 6000, I would use something like 20, 36, 36...because there will be no vacuum advance at WOT, my timing will be 20* at 1100 and 36* at 3000 and above. If you're using the base RPM breakpoints, I would use the same 20, 36,36 for 45kPA because I'm guessing that with the mech adv all your timing was in before 3000 RPM, especially with a light car like yours.
To get the advance in earlier, you need to shift the mid RPM breakpoint down. I'm using 1100, 2300, and 5800 and have 20, 34, 36 for mid kPA and 20, 36, 36 for WOT. I've checked my plugs and they look good.
Let me know if the above makes no sense and I'll try again.
Phoned Fitech after my last tuning run and asked them about full manifold with ignition timing. The tech at the end of the line had no info himself but after my lengthy explanation of why I did it he agreed that I should keep using full manifold vacuum. I mentioned to check out this thread on the fitech forum. I wish the company guru would get on here and post some sage advice - getting tired of being a beta tester.
So on my tuning run I did not go much over 4000 rpms to be safe because I still have the dist. cap with the big hole drilled in it. Shouldn't be driving around with it.
Conclusions: May have to increase the idle timing up a few degrees from 14* - 18* to make the cruise a little smoother with a touch more advance; the 45 kpa scales might need some small adjustments for a slightly better tune. Still learning and playing with it.
65-StingRay/Wayne
Wayne, I would leave the idle at 14* and focus on the 1100 RPM setting at all MAPs. What are your current values for all MAPS/RPMs? I've attached a couple of shots of my handheld to show what can be done by modifying the .inf files. No I don't have zeros for all settings...handheld was hooked to computer. Makes it easier for me to keep track of what I'm actually changing. At this altitude at 65 mph I'm cruising at 2000 RPMs and low 40s kPA . 200R4 trans and 3.42 rear.
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Rick, thanks for the quick replies. Let me start by answering your questions.
1.Yes my vacuum advance cannistor makes the plate move Counter-Clockwise. I checked this with a mini-vac when the distributor was on the bench.
2. Dizzy is definitely locked-out. The guy at Fitech asked me the same question after I had told him I had done it.
3. I followed your advice and disconnected the vacuum line and plugged it. Then proceeded to set everything without vacuum advance and tuned as best as I understood. It ran decent but not as good as now with the vacuum advance hooked up but it's still a work in progress. Initial timing and VR drift are set. I believe my VR is set at 7.5 and my rotor phase is set at 7* but still may need a very small tweak.
4. In the MSD manual that shows the curves. I used the curve with the one blue and silver springs which had me all in at 3600. But for now I think I will go with what you say by replicating the curve where the 2 blue springs are used (I believe this is the one you use if I'm correct in assuming).
5. Your right those were the settings on the handheld I used initially but after hooking up vacuum I reduced the idle advance from 20* back to 14*.
6. Altitude - 2350 ft. in the great white north of Edmonton. I was running 14* with the mech. so I thought I would stay with it. If I was to make any changes in timing it would be to drop the initial to 12*.
7. Vacuum at idle with no vacuum hooked up is 7"-8". With vacuum can hooked up 12"-13" at idle. It's the B-28 can I believe the same one your running.
8. Depending on which gear: 1800-3rd but I like to go 2500-3000 in 3rd for fun.
9. Breakpoints are the same as stock 1100, 3000, 6000 in both 45 kpa and 95 kpa. MAP should be the same.
10. Idle issue definitely without vacuum advance. Much smoother in every category now with vacuum advance functioning.
11. Not just that one but many others as well. There's a fellow on the Corvette Forum who has a lot of first hand knowledge and experience (forgot his name for the moment) but his articles are just like Jeff Smith's.
12. I have not updated any files since I bought my efi. Do not have the pro cal software. Don't even know if I can download to my software. So inf. files - new to me. Using my handheld to make all changes. I'm pretty good with it and I make changes anywhere I can.
13. Terminal - hope that's the answer.
Great exchanging info. I have to get this done before the snow flies. Today 15* C - 60* F. Could be any day now but hopefully not.
65-StingRay/Wayne
OK, just saw your other posts. Thanks for the pics and the breakpoint info. Got something good to go on. So am heading back out to the garage with those numbers. So with the Pro-Cal software you can make a lot changes to your files. Are the new files much better?
Which efi unit do you have? Mine was one of the first ones they sold. I believe they were in business for about 3 months when I bought mine. I knew carbs when I started but learning efi from scratch was difficult with no answers.
Wayne
Rick, thanks for all the good advice. Did more tuning following what you said about breakpoints and timing settings. This is what I ended up with. 14.3* base; 14.3* idle; 1100@45kpa - 19.9* ; 3000@45kpa - 34.4*; 6000@45kpa-34.1*;1100@95kpa-18.8*;3000@95kpa-32*;6000@95kpa-31.9*. I put your settings in but these are the settings that the efi changed them to after driving a while. So for now I'll stick with them.
At idle spark reads around 15*, vacuum @ -12.5" steady; 1500rpm @ -15" steady cruise; 2000rpm cruise @ -17". Without the vacuum advance I would not see numbers this high. My idle without vacuum advance is -7". So by just connecting the vacuum line I've gone from -7" to -12".
Changed to my new cap from the old one with the hole - instant small difference in idle and start for the better with new cap.
There's no more popping or backfiring. I did have one problem a little earlier in the day when I first started tuning. I went to 3000 rpms through 3 gears and in 3rd at 3000 she backfired loud one time. Took my foot off gas and everything seemed good but my IAC motor was stuck at 32 and not moving. Pulled over turned it off, waited a minute re-started all well. Tried again through 3 gears to 3000 and pop again IAC motor stuck at 32. I was close to home so drove back slowly. Did some internet checking and what I found out was my fuel pressure regulator vacuum hose was hooked up to ported vacuum. Teed the fuel press. reg. with the advance can back to manifold vacuum . Went out for another test tune "voila" no more backfires. So this time since the new cap was on I stomped it to 4500 rpms and all is perfect.
There's one more thing I should mention. When I first converted to efi I wanted to go return-less. Remember the Fitech can be plumbed to that force feed tank. No I don't use this. I bought a Tanks Inc. gas tank and plumbed it into C5 corvette filter/regulator that pushes at 58 psi same as the Fitech pressure reg. on the throttle body. So my return line, about 5 ft. long, is at the back right by my gas tank. I used my original 3/8" steel fuel line from back to front. In essence no return line and no hot gas coming back to the gas tank. I have run it like this for 3 years - no issues. A lot of guys are now going this route. I'm not saying you can't have some problems but in general it's pretty straight forward.
65-StingRay
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