Rebuild Runs Rough

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nm9stheham said:
If the thing is not firing evenly, then I would not rely on the AFR to tell me where the mixture is. Unburned fuel is not seen at all by the O2 sensor, but unused oxygen WILL be registered, and, as a result, your AFR readings look lean.

Too much lifter piston compression would sure cause the symptoms...... seems worth investigating.

As for the ICA, I suspect it is in the low 60's due to ground-in cam advance; that gives you cranking pressures like what you have.

Any exhaust restrictions going on OP? Like something got dropped down the turbo outlet pipe? Is the turbo spinning freely? I know it won't likely be spooling at idle but it ought to be free. That is one more exhaust restriction that is going to effect back pressure and effect cylinder clearing and filling.
Click to expand...

Ya know, I did do a lot of oiling mods, opening up the ports and suction, reducing friction by blending the turns. That would deliver more local oil pressure at those lifters, especially the first in line. If all else fails I can reduce the preload by half and see what happens. Oil pressure with 10w30 is 75 cold idle, 30 hot idle.

No chance of exhaust restriction. When hooking up the down pipe, I needed to trim it by an inch to add firewall clearance so I pulled it, cut it, and welded it. It was clean, the muffler is also clean.

The turbo spins nicely at idle and you can really hear it draw in air, too. Even with the filter on. Sounds sinister (in a good way.) The average Joe must think my brakes are bad.
 
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I run my Hughes HD lifters at 1/2 turn,and rev her to 7000 and more. I did your oiling mods and a few others besides. I have no idea what the oil pressure might be; I only have the factory slow-po gauges.

I see your problem with the batch fire. I don't mess with EFI, so can't help you much.
But I can offer this;
Put a vacuum gauge on it and slowly rev it up in Park/Neutral. When the vacuum has risen to about it's highest level, that is when reversion in the intake has ceased, and all the air is more or less going in the same direction. From that rpm, your AFR is gonna tell you the truth, so long as the ignition is doing it's job. Between that rpm and idle your life is gonna be a bit miserable,lol. With that 68* ICA, I suspect that rpm will be about 2200 rpm . That's all I got.


do you know what your Quench distance is?
 
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AJ/FormS said:
I run my Hughes HD lifters at 1/2 turn,and rev her to 7000 and more. I did your oiling mods and a few others besides. I have no idea what the oil pressure might be; I only have the factory slow-po gauges.

I see your problem with the batch fire. I don't mess with EFI, so can't help you much.
But I can offer this;
Put a vacuum gauge on it and slowly rev it up in Park/Neutral. When the vacuum has risen to about it's highest level, that is when reversion in the intake has ceased, and all the air is more or less going in the same direction. From that rpm, your AFR is gonna tell you the truth, so long as the ignition is doing it's job. Between that rpm and idle your like is gonna be a bit miserable,lol. With that 68* ICA, I suspect that rpm will be about 2200 rpm . That's all I got.


do you know what your Quench distance is?
Click to expand...

What’s a rough idle between friends, right? That is some great info, I have been doing this as a hobby for a while now and was ignorant to the reversion, AFR, and IVC teamwork problem at idle. Sounds like I don’t have much of a choice instead of buying MS3, which can process sequential fuel injection. Hopefully I can work out the misfire in the higher rpms to a simple lean condition.

My quench is .085”, that’s from a .046” piston-deck and a .039” gasket. From my understanding, a boosted engine, unlike a NA engine, is more reliable while on boost, with little or no quench at all. I use OEM pistons that sit down deep. The anemic SBM we all love was almost designed for forced induction.
 
They say,and I don't know the truth of it, that Q from .050 to .080 can be more susceptible to detonation than any other Q. But that's for a gas-burner. At .085 and E-85 I imagine you should be fine, especially with smoothed chambers.

I think, think, that late closing intake might be a bit of stinker to tune in batch.I'll be watching to see how this plays out, so I can learn too. You might need a higher than normal idle speed to start off with,IDK.......

Yeah I’m thinking the crank trigger may be at fault. It seemed a little eccentric on the pickup when setting the gap. Maybe play with the noise filter. Surely something is making it run poorly. With so many changes, I just pray it isn’t anything engine mechanical. From the compression test, I really don’t think so
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he magnetic pick up should not care about a few thousands runout, so long as the gap does not become excessive, so as to not be read at all or to be inconsistently read. The Moparmagnetic pick-ups that I have tested are good to at least .028 gap.

Because that cam has only a small amount of overlap(possibly as little as 40*), and because you are not running a tuned exhaust, it seems to me you could
install the cam at quite a bit advanced, to close that intake a lot sooner. You said in an early post that it was in on a 113 ICA, and I grossed your .050 specs up by 52* to get an idea of where the intake was actually closing, which got me an ICA og 68*. IMA thinking you could advance her up to 6 or 8 more degrees. This would increase your cylinder pressure as well.
From this;
Static compression ratio of 8.62:1.
Effective stroke is 2.47 inches.
Your dynamic compression ratio is 6.68:1 .
Your dynamic cranking pressure is 97.76 PSI.
V/P (Volume to Pressure Index) is 71

to this at 8 more degrees
Static compression ratio of 8.95:1.
Effective stroke is 2.66 inches.
Your dynamic compression ratio is 7.38:1 .
Your dynamic cranking pressure is 115.31 PSI.
V/P (Volume to Pressure Index) is 90

Don't look at the numbers as absolutes cuz we already know they don't match up to your engine. Rather look at the percent increase ; from 98 to 115 is about plus 17%, and changes the ICA from 113 to 105.
That might be excessive, IDK, but 4* would certainly be do-able: here it is at 4 more degrees, 109 ICL
Static compression ratio of 8.95:1.
Effective stroke is 2.57 inches.
Your dynamic compression ratio is 7.16:1 .
Your dynamic cranking pressure is 109.75 PSI.
V/P (Volume to Pressure Index) is 83
now an increase of 12% pressure, and an ICA of 64*

I am speculating that the earlier closing intake would help clean up the intake, increase your intake vacuum,stabilize the idle, and increase your off-boost torque. But there is no free lunch. To get the extra compression degrees, using the same cam,it has to be stolen from the power cycle; so losing 4,6 or 8 degrees from 108 is gonna cost you a bit of off-boost fuel economy.
 
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AJ, it looks like you're forgetting about any ground-in cam advance in your ICA numbers. I came up with an ICA in the same way you did, but added some ground-in cam advance. Add 4-5 degrees and the ICA is in the low 60's and the predicted cranking pressures come up close to his measured numbers.

FWIW, my Starion 2.6L turbo engines run a cam that is similar with perfectly smooth idle with throttle body injection. 264 advertised and 45 degrees overlap. ICA is 59 and cam advance is 2-3 degrees. SCR is a true 8.2 and runs without detonation to 15 psi boost, with open hemi-chambers. (BUT, it has and AL head.) So, based on that, if the OP's cam has the low 40's degrees of overlap, I don't think the issue is in reversion.

The op has the most important things in the cam as-is for a mild turbo use:
  • Limited overlap to keep the exhaust pulses sharp and peaky to help the turbo spool up a bit more quickly at low to mid RPM's
  • Not too much duration; let the turbo do the work. It could be a bit less IMHO.
His SCR also should stay in the 8's; high 8's SCR ought to be limited to around 8-10 psi boost as a guess, on gasoline. But then there is the E85 thing, which might allow a bunch more boost.

I see the batch fire thing; looks like the older MS unit is really set up for throttle body injection. But how come the prior engine build ran fine? Back to the EFI or programming as suspect #1.....
 
MS can do both run sequential and batch in case you want to run a second pair of injectors and just batch fire at higher rpms.
 
True ^^^ depending on what people buy. I'll be dealing with a MS3x set up on my car once I can finish the build and start tuning.
 
AJ/FormS said:
They say,and I don't know the truth of it, that Q from .050 to .080 can be more susceptible to detonation than any other Q. But that's for a gas-burner. At .085 and E-85 I imagine you should be fine, especially with smoothed chambers.

I think, think, that late closing intake might be a bit of stinker to tune in batch.I'll be watching to see how this plays out, so I can learn too. You might need a higher than normal idle speed to start off with,IDK.......


he magnetic pick up should not care about a few thousands runout, so long as the gap does not become excessive, so as to not be read at all or to be inconsistently read. The Moparmagnetic pick-ups that I have tested are good to at least .028 gap.

Because that cam has only a small amount of overlap(possibly as little as 40*), and because you are not running a tuned exhaust, it seems to me you could
install the cam at quite a bit advanced, to close that intake a lot sooner. You said in an early post that it was in on a 113 ICA, and I grossed your .050 specs up by 52* to get an idea of where the intake was actually closing, which got me an ICA og 68*. IMA thinking you could advance her up to 6 or 8 more degrees. This would increase your cylinder pressure as well.
From this;
Static compression ratio of 8.62:1.
Effective stroke is 2.47 inches.
Your dynamic compression ratio is 6.68:1 .
Your dynamic cranking pressure is 97.76 PSI.
V/P (Volume to Pressure Index) is 71

to this at 8 more degrees
Static compression ratio of 8.95:1.
Effective stroke is 2.66 inches.
Your dynamic compression ratio is 7.38:1 .
Your dynamic cranking pressure is 115.31 PSI.
V/P (Volume to Pressure Index) is 90

Don't look at the numbers as absolutes cuz we already know they don't match up to your engine. Rather look at the percent increase ; from 98 to 115 is about plus 17%, and changes the ICA from 113 to 105.
That might be excessive, IDK, but 4* would certainly be do-able: here it is at 4 more degrees, 109 ICL
Static compression ratio of 8.95:1.
Effective stroke is 2.57 inches.
Your dynamic compression ratio is 7.16:1 .
Your dynamic cranking pressure is 109.75 PSI.
V/P (Volume to Pressure Index) is 83
now an increase of 12% pressure, and an ICA of 64*

I am speculating that the earlier closing intake would help clean up the intake, increase your intake vacuum,stabilize the idle, and increase your off-boost torque. But there is no free lunch. To get the extra compression degrees, using the same cam,it has to be stolen from the power cycle; so losing 4,6 or 8 degrees from 108 is gonna cost you a bit of off-boost fuel economy.
Click to expand...

I use a Ford Hall effect crank sensor. Which is said to be even more forgiving to eccentricity.

You read my mind, I was about to ask your opinion in advancing the cam. If I crack it open, I have a 4* +/- option in the chain cogs. I could also just swap the cam or even run an oem roller cam, probably get one for free. I will likely just advance it and call it a day. Thank you for your detailed analysis.

I only have a couple hours a week to work on this, so it is very slow going. I will report back, though. Hopefully with a good video, when I figure that out.
 
nm9stheham said:
AJ, it looks like you're forgetting about any ground-in cam advance in your ICA numbers. I came up with an ICA in the same way you did, but added some ground-in cam advance. Add 4-5 degrees and the ICA is in the low 60's and the predicted cranking pressures come up close to his measured numbers.

FWIW, my Starion 2.6L turbo engines run a cam that is similar with perfectly smooth idle with throttle body injection. 264 advertised and 45 degrees overlap. ICA is 59 and cam advance is 2-3 degrees. SCR is a true 8.2 and runs without detonation to 15 psi boost, with open hemi-chambers. (BUT, it has and AL head.) So, based on that, if the OP's cam has the low 40's degrees of overlap, I don't think the issue is in reversion.

The op has the most important things in the cam as-is for a mild turbo use:
  • Limited overlap to keep the exhaust pulses sharp and peaky to help the turbo spool up a bit more quickly at low to mid RPM's
  • Not too much duration; let the turbo do the work. It could be a bit less IMHO.
His SCR also should stay in the 8's; high 8's SCR ought to be limited to around 8-10 psi boost as a guess, on gasoline. But then there is the E85 thing, which might allow a bunch more boost.

I see the batch fire thing; looks like the older MS unit is really set up for throttle body injection. But how come the prior engine build ran fine? Back to the EFI or programming as suspect #1.....
Click to expand...

On the the previous build, with E85 I ran it to a max of 11 psi, corrected. Double my thin atmosphere. I do remember it ran great at-power but the idle was similarly choppy. I must have some mapping issues, and maybe a hidden vacuum leak. Maybe MS2 has a newer software update or a newer card I can purchase for sequential injection. I honestly haven’t even looked into it yet.

Thank you for everyone’s help in this. After I get a half decent tune, I need to measure my trans line and cooler pressures to ensure I don’t have change torque converters or smoke my new crank. then it’s off to do some body work.
 
I was able to spend some time on tuning. I enriched fuel over the entire spectrum and it ran much better in the problematic upper/lower rpm areas from before. Only when when I significantly retarded the timing to no greater than 28 is when it began to act normal - crisp throttle response, no misfires, stable upper/lower rpm. Idle is sitting at 12 degrees, 2000 rpm is sitting at 18 degrees.


I keep asking myself why it is craving such lower ignition timing than before. Could it be from the lowered compression ratio? Higher alcohol content in the fuel? Or did I unknowingly upload a tune that I had for gasoline? I may never know on that one, it last ran well almost 2 years ago before the crank swap. I may have just made that simple mistake.


I did find out that with MS2, I can buy a processor upgrade that will allow fully sequential timed injection for 8 cylinders. Which may be very beneficial, not only for a better quality idle. When servicing the heads after the last tear down, I noticed some intake valves had heavy carbon deposits (relative for an engine that only ran 10 hours) compared to others that had a near polished appearance.


All in all it runs much better. I thank you guys. I took it out for a ride and ran it up to 13 psi boost. A little on the rich side, but runs very healthy indeed. I need to choke it down to 10 psi next.


I’ll have to post a video link once I can safely take one and have my wife upload it to Insta-face.
 
You do not have excessive timing; OOps , that's not what you said,lol
You said
I keep asking myself why it is craving such lower ignition timing than before.
Click to expand...
12 looks good at idle
18 looks a lil low at 2000 (altho I don't run much more @22*)
So that's about 6* per thousand; 6 tenths/100.. If the curve is linear, One could expect 24* at 3000, and 30* at 4000, and your
28 at around 3600. So the rate looks sorta normal.
With High compression,Tight-Q, and aluminum heads, like I have, this would only be 4 to 6 degrees short.
Ok hang on, here are some thoughts;
Why does a gas engine need advance? Well, because the gas molecules, under compression need TIME to find oxygen molecules to react with. The combustion chamber is shrinking, and the pressure is rising, and with the fire started early, the pressure spike is gonna occur at the right TIME, at about 15* ATDC, hopefully, cuz that is where the crank is about ready to receive the maximum transfer of energy.To make this happen we have to start the fire earlier. And as the rpm goes up,we need more and more time (advance) to end up at that 15* ATDC. But there comes a time,lol, when the chamber starts becoming more efficient, and then the timing advancement can be put on hold.
But in your case, the new chamber is hit with a triple whammy.
1) the compression is now lower
2) The turbo is doing what is normally done by the Tight-Q, namely homogenizing the mixture, and
3) the fuel already has a large portion of oxygen, already attached to it.
So
I'm wondering if your chambers are now "normalized",
and the earlier one was the freaky one!
Now remember, I'm just tossing out thoughts,...I freely admit I know nothing about turbos,or E85,or even low-compression engines. And I still really hope it's not a valve-timing issue.
Ima thinking fatten it up some more, but IDK.
 
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From my understanding, a boosted engine, unlike a NA engine, is more reliable while on boost, with little or no quench at all. I use OEM pistons that sit down deep. The anemic SBM we all love was almost designed for forced induction.

Not true
we ran 60 pounds of boost- on Meth at first we had too much squish area on the side away from the plugs- blowing out the fire Fordgetrue D Dish pistons with BBC pins
cut it down but still tight quench- about .040 with Carrillo Rods and Chrysler Hemi Pins - Bob Brooks Pistons
"The turbo is doing what is normally done by the Tight-Q, namely homogenizing the mixture," that's squish turbulence - covered above- you have to tune it
I do not like your quench- quench has two cold surfaces coming close which prevents detonation, also not enough volume between the surfaces to detonate
valuable IMHO
I do not think your problem here but when you get it running might come up
how much spark plug ground distance do you have between plug and piston
you might try some warmer longer reach spark plugs for testing only after ruling out all sources of vacuum leaks, etc
 
AJ - that’s a great way of looking at it! It makes a lot of sense.

wyrmrider - I was hoping I’d have a better quench combo but it didn’t work out. I’m pushing twice the air and fuel through this engine than a NA 318 could, plus more volume of fuel compared to gasoline, does that offer any forgiveness with a less than optimal quench? The E85 is comparable to 105 octane. I may not see benefits of a tight quench but I’m also able to raise/lower the power peak by adding/reducing boost. As of now I’ve lowered the boost to make it more friendly as to what my current tires and suspension can handle.
 
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e-85 you are much better off than with gasoline
we found quench did help with methanol
check your plugs heat range
next time U have it apart check the burn on the piston top
good choice- don't kill yourself
if you are driving this thing on the street get some BIG torsion bars in there
add a leaf to the rear
Cordoba rear sway fits B and C body once you have the front stiffened up DO NOT DO IT WITH STOCK TORSION BARS
but the biggest sway bar on the front that fits but you need less with big torsion bars
driveshaft loop new OEM or Dana Spicer U Joints- nothing else
AJ is very helpful- I learn things
keep in touch
 
Wyrmrider said:
From my understanding, a boosted engine, unlike a NA engine, is more reliable while on boost, with little or no quench at all. I use OEM pistons that sit down deep. The anemic SBM we all love was almost designed for forced induction.
Click to expand...
Because the pressure boost in the intake charge slows the combustion speed in the initial part of the burn process. Later in the burn, the final temps rise higher due to the larger amount of heat released, and speeds up the final burn process. The net effect is to lower the peak combustion pressure (not lower overall, but below what it would be with a non-pressurized burn rate) and spread it out in time. So you get a 'less peaky', wider pressure curve versus time in the cylinder..... at least 'til you overboost it.

Here is a pretty decent summary of this type of thing for those who want spend some time to digging into it:

http://web.itu.edu.tr/~sorusbay/ICE/index_files/LN07.pdf
 
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IT stuff, I CAN'T answer LOL.

Works in my browser (Chrome) .... maybe try cutting and pasting the link into a new browser window.
 
Worked for me. On iPhone. Pretty cool stuff! A lot to digest.

Thanks, Kim. I’ll have to reduce the litter preload and see what happens. Hughes instructions say they become noisy with less preload, so that’s a good sign if I go too far.
 
worked for me but came up in Adobe so I had to click on Adobe to bring it up- still have to read it
thanks (I think)
 
Wyrmrider said:
worked for me but came up in Adobe so I had to click on Adobe to bring it up- still have to read it
thanks (I think)
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"I think"... LOL...understood. This presentation seems like a good summary of a lot of combustion factors, so I think it is a good introductory read to that level of detail for many hot-rodders, without all of the math.

If you really want some headaches, I can find links to papers on modern mathematical modeling of the combustion process. I checked one of them out and went through some of the formulas and the modeling says/is-based-on the same thinking: higher intake tract pressures slows the initial combustion process.

I always wondered why pressurized engines can run and survive with higher peak cylinder pressures and not detonate; the lower initial temps from the slower initial combustion explains that.
 
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