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L28 54/MN47 

Short block is fresh for the most part. New bearings , rings 

rebuilt head 530 lift cam 

megasquirt 3 - NA 

 

It’s a long story but this is what I’ve done 

Compression test 220 + or - 5 all cylinders . 

Coolant pressure test - passed

leakdown - less than 5%

swapped coils , plugs, wires , injectors, injectors connectors . 

Checked valve lash - several times 

checked for vacuum leaks 

vacuum is about 9 at idle 

vacuum needle bounces badly - especially at idle . It’s hard to make out a reading. The MAP gauge on MS is not that erratic ,  but it isn’t smooth either .

 

Is it possible to have a bad HG and still get 225 on a compression tester?

Is it possible to have a broken ring and pass a leakdown ?

Is it possible for either of these tests be mute under running conditions ?

I am at a loss and ready to rip it’s head off but will take any last ditch efforts and thoughts .

 

 

 

Edited by madkaw

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I was chasing some AFR issues for years until I realized my intake manifold was not properly aligned with head. It was causing too lean condition on first 3 cylinders and too rich AFR on last 3 cylinders. Maybe worth a check? I found it while I was disassembling intake to port it. 

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Maybe the ECU is commanding #6 more than it should.  If you replaced everything and still have the same issue, look at what controls it all and that is the Megasquirt ECU.  Look into your files, see if your settings are the same.  I have no experience with mega, just being a technician and looking what controls it.

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5 hours ago, Lazeum said:

I was chasing some AFR issues for years until I realized my intake manifold was not properly aligned with head. It was causing too lean condition on first 3 cylinders and too rich AFR on last 3 cylinders. Maybe worth a check? I found it while I was disassembling intake to port it. 

 

So the intake was biased forward or backwards ? So are you saying this didn’t cause a vacuum leak but caused inconsistency in the runners ?

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3 hours ago, silverado22c said:

Maybe the ECU is commanding #6 more than it should.  If you replaced everything and still have the same issue, look at what controls it all and that is the Megasquirt ECU.  Look into your files, see if your settings are the same.  I have no experience with mega, just being a technician and looking what controls it.

Well it’s batch fire and I swapped the leads between 5&6 with no change . 

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20 hours ago, madkaw said:

So the intake was biased forward or backwards ? So are you saying this didn’t cause a vacuum leak but caused inconsistency in the runners ?

 

That's right. The intersection of intake runners and head port made flow section being inconsistent. Weird knowing intake (Cannon Manifold with 40 DCOE) were used in the past on different head with no problem. I'm talking about 2mm difference between #1 & #6.

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1 hour ago, Lazeum said:

 

That's right. The intersection of intake runners and head port made flow section being inconsistent. Weird knowing intake (Cannon Manifold with 40 DCOE) were used in the past on different head with no problem. I'm talking about 2mm difference between #1 & #6.

Running a stock n42

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17 hours ago, silverado22c said:

The vacuum seems low.  You can either smoke the system, to see smoke coming out, showing a vacuum leak.  Or you spray carb cleaner at items near number 6, trying to locate a vacuum leak.  The engine will some out when consuming the carb cleaner.

Sprayed it down and couldn’t find anything

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Sounds like a rich condition more than oil fouling. Can you run the injectors and rail off of the manifold and compare the spray patterns?

 

Vacuum does seem pretty low unless it's a radical cam. I get about 17-18 inHg at idle with a .540"/270° cam. It's all about the overlap and IVC point so you can also have poor vacuum if the cam is too far retarded. Doesn't necessarily explain a fouled plug but worth looking into.

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45 minutes ago, Leon said:

Sounds like a rich condition more than oil fouling. Can you run the injectors and rail off of the manifold and compare the spray patterns?

 

Vacuum does seem pretty low unless it's a radical cam. I get about 17-18 inHg at idle with a .540"/270° cam. It's all about the overlap and IVC point so you can also have poor vacuum if the cam is too far retarded. Doesn't necessarily explain a fouled plug but worth looking into.

Pretty sure I can the cam timing right , but maybe time to check. 

Not sure how I could get 225psi on retarded timing 

Edited by madkaw

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So I pulled the intake and found and oily residue lining the intake runner of 4-6 . Looks like # 6 could have a bad oil seal . Maybe bad enough to foul the mixture . The plug always looked more like carbon fouling and brushed off pretty well with a wire brush so I didn’t suspect oil . Not sure if a bad oil seal would cause my bouncy vacuum readings unless I’m seeing this as a misfire . Hopefully the guide itself is not bad . I tried a different type oil seal instead of the Ford seal and I guess I didn’t get one right . I’m assuming the color in the plugs on 4&5 is from a small amount is containment from #6 oil getting sucked over from the plenum . 

The pic is brand new plugs ran in a warm up cycle- I know , not the best, but car is on lift . 1-3 looks clean and is running 13-14 AFR. 4-6 get progressively worse. 

Valve pic is #6 . 

D4955712-2200-486F-BF87-EBE2AD0B87FF.jpeg

C51E5488-0D05-48F2-AC43-6C7D636876AD.jpeg

2A89E586-4589-4F66-A4F2-285E02D22CB7.jpeg

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Banned from Fascistbook for a Homer Simpson Meme I DOWNLOADED from Fascistbook...

 

Back three look rich compared to front three.

 

Where is your FPR? I agree with JeffP that firing all injectors at once is a TERRIBLE idea! This will cause a serious drop in fuel rail pressure which will screw with the mix. Load sensing enrichment is better with manifold referenced FPR than static. He’s incorrect in terminology, that’s not a “rising rate”, that’s simply “manifold referenced 1:1”... a “rising rate” would increase it 1:2 or 1:3 etc meaning static is X pressure, 5# of boost is then X+10 or X+15 psi whereas a standard manifold reference would be X+5 psi, and at idle with 18”hg it would be X-9psi making your injectors variable capacity. Idle benefits by lower pressure because you use longer pw which makes resolution better for adjustability, and on WOT you run as a non-referenced unless you get to the point where the engine bottlenecks through the throat and it slightly leans out (like L-Series need past peaktorque anyway...)

 

Mine ran like poop until I switched to alternating two pulses per cycle instead of single pulse simultaneous.

 

Who says? MS Megamanual. Good enough creds there?

 

I think that’s enough for a start, but something is grouped 123-456.

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FPR is after the the tail . I could split the batch. I have the hot running to the fuse box , just got lazy because MS said it was okay to run all 6 with one hot. Need to get sequential going , but this should work unless the demand can’t be met with a bigger engine . I do have some kind of oil issue from a seal or something . Maybe get away with swapping intake valve guide seal on #6 will help

C5AA3210-BA7C-4D9C-97A5-D1C557E8103F.jpeg

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Well after trying about everything I could think of I pulled the head . I definitely have an oil control problem . Since this is a fresh assembly I must of got something wrong or something failed. I tried different valve guide seals on this build, but examining one of them I couldn’t say if it failed . Removing the head revealed a oil film on 4,5,6 with 5&6 being the worst. Maybe oil control rings broke, failed ? 

Im going back to the Ford valve seals, but really should pull a piston - ugh. 

Just weird it happened on the last three . Or is possible it’s just #6 and engine vacuum is dispersing it between the closer runners ? 

Learning a lot in this build - the hard way

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Just going back to injector wiring for a moment. Yes it's fine to run all injectors off of one Power Lead. But that goes through a Relay direct from the battery. But the ECU triggers injectors by grounding. And you should be using BOTH injector driver banks with that. Even if using Multi Point ( all injectors fire at once ). 

 

 Batch fire requires one bank of cylinders ( usually 1,2,3, )  firing from Bank A and the other Bank ( 3,4,5 ) firing from Bank B. But remember it's the ground side of the injector drivers that does the triggering. 

 

Once you have the injector wiring corrected, choose 2 squirts alternating as Tony mentioned. . That will enable batch fire. 

 

Multi-point is the least desirable method, particularly with larger injectors. The " Water Hammer " effect gets pretty bad. will cause spikes in actual Fuel Rail pressure. Batch fire is much better and of course true sequential injection is best for emissions quality and smooth idle.

 

Negligible difference in power output at WOT between Batch Fire and Sequential at high RPM though. Everything is just happening so fast.

 

Sequential does reduce available time to inject fuel over a 720 degree combustion event because it is Timed injection. By about 30% if memory serves me correct. If IDC are getting high, you can reduce them by switching to Batch Fire. Just an interesting but possibly irrelevant point in your situation. 

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