Secondaries

[Ashaman]

OK, it comes up fairly often on Isuzone, but I wanted to gather opinions here also.  Apparantly, from what I know, the secondaries are open when the engine is off.  Once the engine is started, the ECM sends 12V to the solenoid, which allows vacuum to pass to the actuator, which then closes the secondaries.  They then stay closed until the engine reaches 4700 RPM, at which point they open.  Sound all good?<br><br>Anyway, I am wondering a couple things, firstly...  When the engine is idling  they are closed.  You can see the end of the actuator in between the valve cover and intake manifold....is it "UP" at this point or "Down?"  I think it should be down, which is closed, but wanted to confirm if anyone knows.  Revving the engine beyond 4700 RPM should cause them to open, which I think is then the "up" position.  Maybe I should go take pictures of mine to show what I mean...<br><br>Next, it seems like Isuzu/Lotus went through a lot of trouble to implement this system, so I suspect it makes a very real difference.  However, I wonder if changing other factors (Turbo/exhaust, etc) makes a difference where they are concerned as well...I would think that it would.<br><br>Right now, I think mine are open all the time.  However, I don't really notice a difference in the low end from before, which seems odd.  Anyway, I am adding an RPM activated switch to control these, which of course brings up the question of whether 4700RPM is still the best choice for me, or if it might be better to open them sooner or later.<br><br>Also, does anyone know where the connector for the solenoid is located right off?  I see it in the shop manual, but trying to interpret that into real-life isn't always easy

[Doug]

yeah,<br><br>higher boost,<br>open secondaries sooner,<br>get new longer duration cams,<br><br>= more POWER  ;D<br><br>(or so it goes something like that)<br><br>I expect you will be the one to find out if you put a switch in there as you could do dyno runs with it opening at different times and see the results!

[Ashaman]

Thanks, I think I am going to shoot for 4000 RPM.  I think the shop manual lists 4700 as the open point, while the Electrical manual lists 5200!  Strange.<br><br>At any rate, that should do it.   Dave, if you could confirm I would appreciate it.  I wired everything up earlier this week, and was very annoyed when it didn't work.  After beating my head against a wall, finally called Summit to ask what the deal was, he said, "Oh yeah, there are some notes here - apparently it is only for V-8 engines..."  I guess they didn't think that minor detail wasn't worth mentioning in the product description, technical specs, OR THE BLASTED MANUAL!<br><br>Ah well, I now have an MSD unit on the way so it should work well.  Regarding the VSV, it is indeed on the back but I never did catch sight of it.  However, I found that grounding (opposite of the schematic if I recall correctly) pin A4 on the harness causes it to move the actuator, so it was very simple to just do a lead off my adapter-harness for it.<br><br>So, once it gets here I should be set...provided I don't get it opening when it should be closing, and vice-versa  :P

[Dave M]

Anyway, I am wondering a couple things, firstly...  When the engine is idling  they are closed.  You can see the end of the actuator in between the valve cover and intake manifold....is it "UP" at this point or "Down?"  I think it should be down, which is closed, but wanted to confirm if anyone knows.  Revving the engine beyond 4700 RPM should cause them to open, which I think is then the "up" position.

Josh, sorry for the serious delay in getting this confirmation to you. As I was going through some things the other day for LOG, I found a note I had written myself to check on this for you. I believe I didn't check at that time as the engine shop had my intake. Anyway last night I pulled all my parts out to start reassembly, and lo and behold, there sits the injector housing with the secondaries. I can confirm that the "UP" position is open. This is where you can see the actuator end in between the runners. Must be it is open at idle, then closes under load before rpm-switched open again?

Thanks for determining the A4 lead as the "switch". Does the actuator move down when ground is applied?

[Ashaman]

Yeah, no problem...I knew you have a lot going.

It is up/open when everything is off. Once the engine is started, pin A4 is grounded it is then closed/down. If RPMs reach ~4-5K (never confirmed the actual point) the ground is lifted and they open again until RPMs drop below that point once more.

I can set my open/close point wherever I want, so it might be interesting to play with on a dyno.

[Dave M]

Excellent! I plan to do the same testing with opening at different rpm when dyno time comes.

[Doc Fizzix]

Do you guys have any new information on this? I have my intake apart and I have been reading some of the Isuzu boys remove the secondary valves, your results if any would be helpful.