The MFI Diaries: Correlation at LAST!

[304065]

Originally Posted by Eddyvdw

I'm using above mentioned method with the vacuum cleaner and synchro-meter. Working on the right throttle body. Fully cleaned. Noticed some wear. Air screws set at 1.5 turns (2.4E).

2 cylinders are fine at stop reading of 3 kg/hr. The other gives me a bit more trouble. Can get to 3 kg/hr only if I help it a bit. If I simulate WOT and let it flip back to idle, the reading is more close to 5kg/hr. If i push it in idle by hand the reading drops to 3 kg/hr.

So what to do? Adjust the other 2 also to 5kg/hr and accept a higher idle? Get a stronger spring for the troublemaker?

Thanks,
Ed

Ed,

In the intervening years since I wrote this, I have concluded that what you really want is the same exact angle on the plates. In other words, 3Kg/ hour is really a proxy for them all being open the same amount-- If, to get to that low reading, you end up having the plates actually closed, that's kind of a bad idea, because the edge of the plate will be contacting the bore of the throttle body.

You want the plate just SLIGHTLY open. . . maybe try a feeler gauge, bent slightly to conform to the plate, to set them all the same? The gauge will bridge any depression in the magnesium throttle bore.

In the alternative, go ahead and leave the one "offender" set as low as you can get it-- likely the car won't idle at 3Kg/Hr per cylinder anyway-- you will probably have to adjust the air bleed screws to get a rock-solid 900 or 1000 rpm.

Higher idle is not acceptable for a bunch of reasons, if you are in this deep, you shouldn't settle for anything less.

Good luck!

[Eddyvdw]

Thanks, the troublemaker sticks at idle so have to set it even a bit higher.

What I don't completely understand is the air bleed screws. According to CMA the stops are to set idle and the air bleed screws to align at 3000 rpm. Or did I get this wrong?

Also, I don't have a MFI protractor. Is that a serious issue? For what I read the opinions differ between the guru's.

Thanks,
Ed

[BSNMOE]

The Lee Rice method is after TB's are at stops, turn them open 3/4 turns and lock them down. Turn air screws out 2 1/2 turns, warm the car up and adjust air flow equal by turning the TB bolts in the direction of more air in the lower flowing stacks. Keeping air screws at 2 1/2 turns out.

I have removed my stacks, held a light up to the TB's and then used the shop vac method to get them equal at 3KG/H, however, when assembled with a warm(190/200 deg)engine everything changed anyway. I then used the Lee Rice method, but,because my car is a 2.4., I opened up air screws out 1 1/2 turns and adjusted the TB bolts for equal flow.

I also found that at 3000RPM they were off a little and found that my socket end caps were slighty worn. After replacing them the flow is near perfect at idle and 3000.

I believe heat effects everything, including rod lengths and thats why Lee Rice suggests to warm the car up, turn off to heat soak everything prior to making adjustments.

[Eddyvdw]

Thanks, so if I understand correctly you adjust idle with the bolts and at 3000RPM with the airscrews. But the airscrews will then impact idle as well so back to square one.
Ed

[tobluforu]

Right, kind of. Once you get it all set at idle, you rev it to 3000 rpm, and synch it there, once again. If the rods are ok, etc then it should not take much to get them all synched at this rpm, which should really not affect idle all that much. But if you are turning the screws a whole lot, then something else is wrong.

[BSNMOE]

To expand to what Tobluforu has said: once idle is set, check at 3000RPM. Write down what all six are pulling then get the average. It is here were I adjusted rod either shorter or longer achieve average air flow between all six. Now go back to idle then adjust the stop bolts so TB's are once again resting on stops. Now re-adjust idle flow via air screws.

I have also adjusted air flow at 3000 just by the air screws but found out that the air screws do not change as much as a fine turn(1/16/1/8) of the TB bolts.

After you get a good balance re-check TB's making sure they are resting on stops not on the soft mag bores. you'll feel them sticking. If you turned then open the 3/4 turn as Lee Rice suggests, you should be ok.

As Toblufru pointed out, if you have to turn your TB bolts too much you'll either hit the mag and wear or if you open them too much you have a high idle.

[Eddyvdw]

One step further.

I cleaned both throttle bodies almost to perfection.

My house has a sauna room which is at around 180F. I put the throttle bodies in there (without me :-) and adjusted the stops after the throttle bodies were warmed up. I get now all stacks at just over 4kg/hr (air screws at 3 x half turn). The worst one is just not sticking + 3/4 turn. The best with a few extra turns of the stop bolt.

Next I adjusted the links. This is easy to do when the throttle body is still at my work bench.

Tomorrow I will put it all back together again.

Ed

[Eddyvdw]

Put every back together. All clean and good.

Car fired up and runs fine and strong throughout the RPM range.

Back home I set the stops at just not sticking. Removed the rods.

Still can't get idle lower then 1200 rpm. Air meter shows for 5 cylinders around 4.5kg/hr. 1 cylinder is at 6 kg/hr and can't get any lower without sticking of the throttle plate.

Any tips how to get to 1000 rpm?

Thanks,
Ed

[304065]

Originally Posted by Eddyvdw

Put every back together. All clean and good.

Car fired up and runs fine and strong throughout the RPM range.

Back home I set the stops at just not sticking. Removed the rods.

Still can't get idle lower then 1200 rpm. Air meter shows for 5 cylinders around 4.5kg/hr. 1 cylinder is at 6 kg/hr and can't get any lower without sticking of the throttle plate.

Any tips how to get to 1000 rpm?

Thanks,
Ed

Ed, what is your ignition advance? Static and idle? Probably what is happening is you have too much advance and that is kicking the idle up.

[Eddyvdw]

Damn, this is a whole new chapter for me, setting the advance. Have to dig into the details to understand what I should do.

I take it one at the time. When I got the car, my uncle (a very experienced mechanic) set all the timing etc right. This was okay until now and I excepted the high idle and rough running around 3500 rpm. I restored everything else and finally got to the engine.

I went through CMA step by step and got to the throttle body so no need to change the advance yet...

Can you educate me a bit?

Thanks,
Ed

[BSNMOE]

Ed, do you have your vacuum retard connected? Your idle timing is 5 deg ATDC (vacuum connected)which will pull your idle down. If connected, remove it and idle should increase even further. Or,(prior to starting) remove dist cap, suck on the line and see if the plate moves. do you have a timing light? when you had the TB's off, did you notice excessive wear on #1, such as lose shaft or more light around TB?

[BSNMOE]

Ed, I forgot to mention. Make sure your RPM tranducer(speed switch) is disconnected

[Eddyvdw]

Thanks. I have a timing light. # 1 is definitely the worst TB.
I'll start playing with timing a bit and see what happens.
Ed

[Eddyvdw]

Thanks guys.

First test. With vacuum line disconnected and plugged (with my finger) the mark on the pulley is spot on. When I connect the vacuum lines, the RPM drops but also the mark on the pulley moves to the right. The light is set on 5 degrees.

Will the RPM drop even more if I get the timing right?

Ed

[Grady Clay]

Whatever adjustments you make, always last check the timing at 6000 rpm.
Too much advance here can damage a piston.

Best,
Grady

[Eddyvdw]

Thanks Grady for the advice.
Still studying a bit how timing exactly works before touching it.

Ed

[BSNMOE]

Ed, you may want to set the timing light to 35deg at 6000RPM(vac disconnected). Then connect vac line and the idle should fall around 4 to 5 deg ATDC. Your light may not show retard, but you'll see the light pointing to the left of Z-1 mark. See if that pulls your idle down.

[Eddyvdw]

VICTORY!

Timing was way of. Now spot on at idle (with vacuum) and 35 at 6000RPM.

THANKS FOR ALL THE HELP.

Ed