fabrication question

[jsgarage]

The results you get may depend on whether you make everything pretty with rigid lines, or use rubber. Rubber lines are compliant to pressure pulses while metal lines are rigid and are not compliant.

[modok]

Power brakes have a one way valve.
Once again THINK why are you connecting that to multiple runners?
If one isn't enough connect to two runners with TWO one way valves.

What I am trying to get across..... is you can put a balance tube between paired(180 apart) cylinders without tempting lope.
If you connect non-paired cylinders or connect all cylinders you make lope. What is lope? it's a hysteresis loop.

The map sensor is only a SENSOR so it does not require any significant FLOW, just a TINY passage. SO....Try connecting the paired cylinders with a reasonable diameter crossover, then connect the MAP sensor to each crossover through with a SMALL tee fitting. This should give fast response and minimal flow connection for maximum INDEPENDENCE. Rig it up with hoses and rubber bands until it works, THEN you can fabricate something permanent.

10 years ago, I figured by now we'd have a map sensor on each runner or at least each pair, and the computer would be programmed for what degrees to read the signal from each.
We DO have the technology to do that now, but the monkey brain isn't advancing fast enough to realize it.

[modok]

Wait....aren't you the guy with the oil burning v-8 with the strange intake?
What is this thing?

[Caprimaniac]

Basically what you want to do is run a IAC on a motor with IR TB's, right?

After what I figured, that should be straight forward- as long as...... You need a small plenum for the system and you also need all hoses running to the individual runners Equal length.

I know Borla offer a IAC for their IR setups, however- i could'nt figure out how they do it. I would look into those kits and get an idea.

[mk e]

the problem is that it is inconsistent. And the leanest cyls tend to misfire. It corrects, and then it runs fine for a while and it starts again. So this is something that I need to figure out.

If it's inconsistent then you probably can't fix it with a mechanical solution like vavles in the iac lines.

If it is consistent cables or trim tables would clear it right up....but if it's changing you either need to figure out why and correct it or you need an active solution from the way.

In a way carbs are much more forgiving because they meter fuel based on air flow, so while they work best when synced well, they will self correct a bit when out of sync....itb don't do that so they are more challenging to deal with and it sure doesn't help if thinks are changing on their own.

[Belgian1979]

.. For practical reasons map, IAC and brakes are on the same lines and vacuum chamber...

Apart from all the other issues and considerations, this will definitely confound the purity of the signal to the ECU. Flow through the IAC will cause a proportional rise in indicated MAP. Visualize a vacuum gauge connected via a small diameter hose to a steady vacuum source, lets say 30 kPa. Now start drilling holes in the line. Every one raises the gauge reading as the leakage increases. Suppose you drill 5 holes. The gauge MAP reading is now lets say 60 kPa. Finally, start blocking off various holes with you fingers, like playing a flute. The MAP reading now fluctuates erratically between 30 and 60 kPa even though the source signal is unchanged.

Reaching back in my memory. Yves, wasn't there an earlier issue with your gas tank acting as a cooling-radiator/heat-sink due to radiant heat from your exhaust heating the returning petrol? I am guessing this will also cyclically heat up your booster and thus would be a reason not to have it included in the system.

Fuel gets heated up by the engine while it passes in the fuel rails and gets returned to the tank. Not exhaust related.

[Belgian1979]

Basically what you want to do is run a IAC on a motor with IR TB's, right?

After what I figured, that should be straight forward- as long as...... You need a small plenum for the system and you also need all hoses running to the individual runners Equal length.

I know Borla offer a IAC for their IR setups, however- i could'nt figure out how they do it. I would look into those kits and get an idea.

There are several solutions that people employ. Not sure on the results. Jenvey has an electronic throttle control, but not controlled by the efi ecu.

[Belgian1979]

Power brakes have a one way valve.
Once again THINK why are you connecting that to multiple runners?
If one isn't enough connect to two runners with TWO one way valves.

What I am trying to get across..... is you can put a balance tube between paired(180 apart) cylinders without tempting lope.
If you connect non-paired cylinders or connect all cylinders you make lope. What is lope? it's a hysteresis loop.

The map sensor is only a SENSOR so it does not require any significant FLOW, just a TINY passage. SO....Try connecting the paired cylinders with a reasonable diameter crossover, then connect the MAP sensor to each crossover through with a SMALL tee fitting. This should give fast response and minimal flow connection for maximum INDEPENDENCE. Rig it up with hoses and rubber bands until it works, THEN you can fabricate something permanent.

10 years ago, I figured by now we'd have a map sensor on each runner or at least each pair, and the computer would be programmed for what degrees to read the signal from each.
We DO have the technology to do that now, but the monkey brain isn't advancing fast enough to realize it.

I must admit I haven't tried to hook up the brakes to one or 2 runners. However the brake booster has a one way valve in it, so somehow I doubt it will let a lot of air in.

[Belgian1979]

Wait....aren't you the guy with the oil burning v-8 with the strange intake?
What is this thing?

Correct, you may not have followed other threads but the problem was the vacuum chamber of which the plate bent towards the lifter valley letting oil in which then got sucked in the runners.

[Belgian1979]

the problem is that it is inconsistent. And the leanest cyls tend to misfire. It corrects, and then it runs fine for a while and it starts again. So this is something that I need to figure out.

If it's inconsistent then you probably can't fix it with a mechanical solution like vavles in the iac lines.

If it is consistent cables or trim tables would clear it right up....but if it's changing you either need to figure out why and correct it or you need an active solution from the way.

In a way carbs are much more forgiving because they meter fuel based on air flow, so while they work best when synced well, they will self correct a bit when out of sync....itb don't do that so they are more challenging to deal with and it sure doesn't help if thinks are changing on their own.

Throttles and runners are never perfect so some degree of variation is understandable. Plugging iac improved the imbalances.

[mk e]

Throttles and runners are never perfect so some degree of variation is understandable. Plugging iac improved the imbalances.

More parts means more variables, there is no way around that.

With the iac system, the bigger the lines and the less they flow, the more likely they'll be matched......which is why you probably want to set the throttles open as much as possible before opening the iac. So set hot idle with iac off, then iac will add for load and cold only. I think that's your best shot.

[Newold1]

Belgian1979

Curious about something else here. Have you previously listed the specs. on your camshaft and installed timing on the camshaft?

I have had a lot of experience with EFI systems and some ITB's and I can tell you that for tuning, operating and idle stability, transition and decel tuning the camshaft design and install has a huge affect on those factors. Just an added thought as you might be chasing two separate problems here as it does not sound like you have ever had this ITB system working nicely as you wish from the get go.

Also what ECM, program tuning and sensor systems are you using on the engine ?

[Caprimaniac]

Throttles and runners are never perfect so some degree of variation is understandable. Plugging iac improved the imbalances.

Then the problem is somewhere in Your IAC system. Leak, enequal lengths, wrong IAC setting....

I am not sure if I figured out what you said about Your vacuum lines. Only Connected to one runner? It should go into all 8.

[naukkis79]

Cruise is within limits (<5% difference overall in VE, in a lot of places it's around 1%). At idle and transition areas I have up to 20% difference in VE, with the cylinders close to the iac supply running at 15-20% VE difference. The result is uneven running and an engine that tries to hunt.

And that VE difference is measured with what? You still use closed-loop and believe blindly what lambda tells?

Have you balanced you itb setup with manometer? With itb it's always first thing to do.

[Belgian1979]

Belgian1979

Curious about something else here. Have you previously listed the specs. on your camshaft and installed timing on the camshaft?

I have had a lot of experience with EFI systems and some ITB's and I can tell you that for tuning, operating and idle stability, transition and decel tuning the camshaft design and install has a huge affect on those factors. Just an added thought as you might be chasing two separate problems here as it does not sound like you have ever had this ITB system working nicely as you wish from the get go.

Also what ECM, program tuning and sensor systems are you using on the engine ?

Camshaft is a Mike Jones unit : mech. roller, 248°/250° @ .050, total lift around .600 and a 106°lsa
ECU : MS3 sequential with LS1 coils.