MPGs run, Aspire SE

[getnpsi]

No you want to have ecu contolling idle timing but it will be close like that

[TominMO]

Note to above: the fact that 0 degrees cam timing is the middle of the sweet spot is further testament to Matt's design. Also, what this says is that an adjustable cam gear is unnecessary. Now to go for a run and see what happens.....

[TominMO]

Didn't go for a drive today after all. I realized that my time would be better spent dialing in higher vacuum.

What I did was set vacuum based on the base timing (i.e., when you use the jumper wire to take the ECU out of the pic). I varied the cam timing and attempted to get the vacuum to 22 inches on the gauge. That turned out to be no problem: I could do it at any reasonable cam setting. So I decided to use a cam setting that got me to 22" of vacuum with a minimum of base ignition timing. I figured that would be defined as "most efficient".

Here are the results:
Cam timing........+2....0....-2....-4....+4....+1....+2
Ignition timing....14....15..15....25....20....18....15
Bear in mind that my ignition timing numbers are visual estimates, since the pulley only goes from 0 to 10 BTDC.

I ended up putting it back to +2. It looks like 0 cam timing is right in the middle of the sweet spot. In some cases I could get the vacuum to above 22 (like 23 or 24), but only at rather extreme ignition timing settings. Don't want to have to run race gas! I'll run premium and back off ignition timing a little if I hear pinging.

BTW, when I took the jumper wire off and re-started the car, at normal idle the vacuum was at 21. So this brings up a question: should I set it at base timing or when the ECU is engaged? Either way, it is significantly better than the 19.5 I had before.

I'll probably go for a drive tmw.

[TominMO]

power = efficiency Tom, so yes, both. every engine has a sweet spot and that's what you're trying to find. Using the vac gauge will help you get there faster (another tuning tool to use along with your timing light and test drives.

Scrappy has the 23" of idle vac. He has a full exhaust, head work, stock cam for the moment, head shaved .020" and is a B6, so the compression should be close to that of a factory B3 (9.4:1). the head was from a manual 323 (9.2:1), the autos had higher compression to compensate for the parasitic loss of the trans (only reason i can think of for the change). also, a compression test is as follows: 184, 165, 185, 184. i haven't pulled the head to investigate cyl #2 yet.

OK, thanks, that clarifies things.

Now I have another issue, a noisy pulley bearing apparently. Have to look into that.

[FestYboy]

So I would probably go about it by adjusting cam timing to a given setting, then rotate the disty to get the optimum vac, and note the disty's position.

Again, what is the point/advantage? Max power, max fuel efficiency? I guess what I am asking is, Can I tune for highest idle vacuum instead of going on 100+ mile runs?

Edit: here's a nice little page on interpreting vacuum readings:
http://www.secondchancegarage.com/public/186.cfm

power = efficiency Tom, so yes, both. every engine has a sweet spot and that's what you're trying to find. Using the vac gauge will help you get there faster (another tuning tool to use along with your timing light and test drives.

Arty, you mentioned that Skippy had a vac reading of 22, and that he also had head work. Does Skippy have higher compression than stock? That might be why he reads 22 vac.

Scrappy has the 23" of idle vac. He has a full exhaust, head work, stock cam for the moment, head shaved .020" and is a B6, so the compression should be close to that of a factory B3 (9.4:1). the head was from a manual 323 (9.2:1), the autos had higher compression to compensate for the parasidic loss of the trans (only reason i can think of for the change). also, a compression test is as follows: 184, 165, 185, 184. i havn't pulled the head to investigate cyl #2 yet.

[TominMO]

Arty, you mentioned that Skippy had a vac reading of 22, and that he also had head work. Does Skippy have higher compression than stock? That might be why he reads 22 vac.

[TominMO]

So I would probably go about it by adjusting cam timing to a given setting, then rotate the disty to get the optimum vac, and note the disty's position.

Again, what is the point/advantage? Max power, max fuel efficiency? I guess what I am asking is, Can I tune for highest idle vacuum instead of going on 100+ mile runs?

Edit: here's a nice little page on interpreting vacuum readings:
http://www.secondchancegarage.com/public/186.cfm

[FestYboy]

a combination of cam and ignition timing (at a given idle speed) will vary the vacuum signal. typicaly the old schoolers would set the ignition timing with the vacuum gauge (setting it when the signal is greatest) and then test driving for ping. if the engine pinged, they'd pull 2* out and retest, or put in better fuel. the same thingcan be done with the cam (to a point). Just keep in mind that the cam timing has more effect on where in the rpm band the power comes in verses the lobe timing (grind) which affects how the cam makes power (as well as where, but like i said before, that part can be moved).

[zoom zoom]

I think arty should do a nice little how to video of how to set and adjust base idle with regards to vacuum at idle! I would like to be in on the secret too! No matter what I've done I can't get it above 19..

[TominMO]

another thing to experiment with is the vacuum itself... see if you can get it into the 21-22" range.

And how would I go about doing that? Do you mean checking it when I adjust the cam, for instance? And what does this mean? An indication of best efficiency?

[FestYboy]

another thing to experiment with is the vacuum itself... see if you can get it into the 21-22" range.

[TominMO]

!!!!!!!!

How did you know I had soft rubber aftermarket caps on like 5 unused ports and a high idle issue! I'm gonna swap out those little things as soon as I find a good replacement.. Any ideas for something new to use?

Even stock JY ones are better.

[zoom zoom]

!!!!!!!!

How did you know I had soft rubber aftermarket caps on like 5 unused ports and a high idle issue! I'm gonna swap out those little things as soon as I find a good replacement.. Any ideas for something new to use?

[rmoltis]

Sounds promising.

[TominMO]

Been a busy day. Snagged another Aspire seat for my Festy at the JY; painted the seat frame feet, which were rusty; installed seats, and the mudflaps Greg sent me; and checked for vacuum leaks on the Aspire.

Went to HF and got the vacuum tester, $15+tax. Started the car and let it warm up. The idle would not stay constant. First I replaced the PCV hose, which had a crack which I had "fixed" by covering it with electrical tape at the split. Replacing it with a good hose helped a little. Then I put the vac gauge on the vac port next to the one for the FPR. That vac port also had an issue; there was a rubber plug on it that was one of the soft rubber aftermarket ones, that will decay easily with heat. I had tried to fix it w/duct tape. That apparently wasn't good enough, because once I put the gauge on in its place, the idle settled down to even and the gauge read a constant 19.0 - 19.5; very little variation. When I took the gauge off I put on a better OEM rubber plug, which I had just snagged at the JY. All other vac hoses looked in good shape. Started car and it idles fine now.

So tmw, another run! FP @ 40, cam +2, ignition 13. I will keep FP and ignition constant and change only the cam timing, retarding it to -2 the next time, to try to bracket what it likes.

Thanks to everyone who is offering suggestions; this now seems more like a group effort, with me at the tip of the spear. I was getting kinda bummed about no results; maybe that will start to change now.