Fast90 Woes - Leanness

[TAQuickness]

Mostly a rant, but I'm open to y'alls opinions/suggestions.

This is a long outstanding problem of mine. Have a fast 90 and inconsistant AFR's between banks. Running a dual wideband setup, left and right bank in the primary O2 locations. I'm 99.999999999999999999999999999% sure this is a hardware problem. To date, here's what I've tried:

Swapped injectors from bank to bank, no change

Replaced injectors, no change

Swapped injectors again, no change

Found two exhuast leaks, fixed them, no change

Tightened intake manifold, no change

Double checked vacuum lines, no problems here

Found crack in #7 runner, JB weld, no change

Crack on #7 turned into broken chunk, replaced lower shell, made new gasket, slight improvement. From here, the left bank would run 2 points higher under 2k RPM. Above 2k RPM, both banks tracked within 0.5 AFR

Remade gasket, Right bank now running leaner than left

Tightened right side of manifold, right bank = commanded, left is off by 1 - 1.5 AFR

Tightened left side manifold, shit hits fan, both banks lean, left ~ 15.5:1, right, ~ 20:1

I'm not sure what's left to try.

[joecar]

Mate, that's gotta drive a person insane... :Eyecrazy: :bawl: :frown:

Sanity check using stock manifold (if you're feeling up to removing it yet again...)...?

[Black02SS]

Have you swaped WB Locations?

[TAQuickness]

crazy? insane? all of the above? yes! I've RR'd the manifold some 20 times in the last 2 months. I'm sure it's in the manifold becuase the leanness changes slightly each time.

Chad - thanks for the reminder. I've also tried:

swap right to left - no change
both WB's on right - AFR's within .05
Both WB on left - AFR's within .05
20 pt WB calibration - AFR's within 1 - went back to stock LC1 config
All new port gaskets (OEM & Comp)
New x2 upper/lower gasket per write up supplied by Arkay (found on LS1 tech)

Have not tried an OEM manifold. Sold them (LS1 and LS6) when I picked up the FAST. Anyone have a stocker I could borrow?

I'm seriously thinking to try that blingy PP manifold in the near future.

[Bruce Melton]

I know many disagree but I think FAST manifolds just suck (or suck where they are not meant to). I could never get my brand new one to seat properly and it kept losening up even with locktite. In the end I cracked the LS6 valley cover which I learned is not unusual. This says that the manifold was bottoming out. It could be that the FAST gaskets are thicker than GM?
I gave up and went back to LS6/Shaner with no problems.

[TAQuickness]

I know many disagree but I think FAST manifolds just suck (or suck where they are not meant to). I could never get my brand new one to seat properly and it kept losening up even with locktite. In the end I cracked the LS6 valley cover which I learned is not unusual. This says that the manifold was bottoming out. It could be that the FAST gaskets are thicker than GM?
I gave up and went back to LS6/Shaner with no problems.

I'm feeling much the same.

[redhardsupra]

yup, i also agree. they flow great, but damn, could you please make them out of a different material than my cheerios bowl?

[caver]

I Have seen them bottoming out on the valley cover bolt heads.

[TAQuickness]

I Have seen them bottoming out on the valley cover bolt heads.

Can you elaborate on this vision? I'm using the flat valley cover bolts supplied with the manifold, but I won't rule it out till I can.

[joecar]

Pics...?

[Bruce Melton]

Pics...?
I bottomed out on allen button heads and on raised portions of Valley cover.
I tried the perscribed torque and all the recommended install tips but kept losening and leaking. In the end I did apply more than recomended torque but only "short handed" 1/4" drive torque.
The result is below. These are not just casting flaws, they are real stress cracks that can be seen from bottom side. There are more than shown and BTW I do not have milled heads which can worsen the problem.
http://home.new.rr.com/meltn/valley.JPG

[joecar]

Hmmm...

seeing that I'm wondering if tightening the bolts any amount is distorting the intake manifold...
manifold hasn't got enough space beneath it...?
leaks if you tighten, leaks if you don't...

Maybe you have to glue it on using RTV and no bolts...?

[TAQuickness]

SHINOLA! I need to double check my valley cover when I pull manifold. Are your heads milled or just ported? Mine are milled 0.024" - might be the problem.

Joe, I like your thinking.

[Bruce Melton]

Sorry, meant milled>Corrected

[TAQuickness]

how much milling, if you don't mind posting that.

[Bruce Melton]

how much milling, if you don't mind posting that.
My current heads are not milled and the problems I had with bottoming out and fit were with unmilled 5.3 heads. We milled a set of LS6 heads .030 and had a similar problem with stock manifold which we finally solved.
If you think about taking say .030 of each head and the effect it has on the angles and depth and width of the "V" the intake sits in, it is fairly major. With a stock manifold it drops the manifold enough cause problems. For the POS FAST it is almost assured it will bottom from the start, then what?

[ringram]

Id have a fast90/90 if they fit properly and wernt so expensive.
Hopefully a competitor enters the market with a decent composite intake.

[joecar]

Is there a way to locate the contact points on the bottom of the FAST and shave those down...?

[joecar]

Would it be possible to use coloured stuff (prussian blue, yellow ring/pinion paint, white lithium grease, etc...) as an indicator to see where the manifold is hitting the valley cover (or vice-versa)...?

[TAQuickness]

Would it be possible to use coloured stuff (prussian blue, yellow ring/pinion paint, white lithium grease, etc...) as an indicator to see where the manifold is hitting the valley cover (or vice-versa)...?

I was thinking about that today. Bruce's latest entry makes me think there is no hope. I have 5.3's milled 0.024":bash:

[Bruce Melton]

I was thinking about that today. Bruce's latest entry makes me think there is no hope. I have 5.3's milled 0.024":bash:

I still have my LS2 TB and and am looking for real alternatives for intake.

[TAQuickness]

I still have my LS2 TB and and am looking for real alternatives for intake.


let me know if you find anything. I pulled my fast this afternoon and started cleaning it up. not sure if i'm going to sell it or give it another whirl

[Bruce Melton]

let me know if you find anything. I pulled my fast this afternoon and started cleaning it up. not sure if i'm going to sell it or give it another whirl
I don't know if you are following this L92 head journey but that looks very promising if the Aussie intake is decent. The heads are incredible and cheap.

[TAQuickness]

link?

This has been a heck of a weekend. Laptop took a dump and will be 6-8 weeks before I get it back from warranty.

Pulled the manifold to inspect for leaks and bottoming out. No signs of hitting bottom, but appearantly Blue RTV is not worthy of making manifold gaskets (between shells). Started scraping the blue RTV out so I can make a new black RTV gasket.

Although I dont' see signs of bottoming out, the port gaskets appear to have a problem sealing near the valley cover. One of the side effects of a previous sealing atempt, I managed to increase the thickness of a port gasket a good bit (will put the mic on it later this week). I'm thinking I may as well make all the port gaskets a little thicker.

I hate this manifold.

[Bruce Melton]

link?

This has been a heck of a weekend. Laptop took a dump and will be 6-8 weeks before I get it back from warranty.

Pulled the manifold to inspect for leaks and bottoming out. No signs of hitting bottom, but appearantly Blue RTV is not worthy of making manifold gaskets (between shells). Started scraping the blue RTV out so I can make a new black RTV gasket.

Although I dont' see signs of bottoming out, the port gaskets appear to have a problem sealing near the valley cover. One of the side effects of a previous sealing atempt, I managed to increase the thickness of a port gasket a good bit (will put the mic on it later this week). I'm thinking I may as well make all the port gaskets a little thicker.

I hate this manifold.

I used the GM o-rings/gaskets but you might check to see if the FA$T ones are different?

http://www.ls1tech.com/forums/showthread.php?t=483486

[joecar]

I've used the black rtv and the blue rtv (on various non-intake related things) but I like the copper rtv the best, it seems to stick far better to everything (including your face and shirt and door knobs throughout your house).

[Blacky]

I've used the black rtv and the blue rtv (on various non-intake related things) but I like the copper rtv the best, it seems to stick far better to everything (including your face and shirt and door knobs throughout your house).

:D I can just picture it....

[TAQuickness]

:D I can just picture it....


I can picture my boy running up with a smoking trail behind him, "Daddy Daddy, guess what?!"

Bruce - I've been thru both OEM and Comp port gaskets - I prefer the OEM. I got a few ideas while I was sitting in the waiting room. When things start to normalize around here, I'll give them a shot.

I'm starting to believe a Fast90 that doesn't leak is the cure for baldness.

[Black02SS]

I'm starting to believe a Fast90 that doesn't leak is the cure for baldness.

I am interested then. :muahaha:

[TAQuickness]

I am interested then. :muahaha:

on the same note, I believe the leaking FAST is the source of baldness. http://www.myspace.com/taquickness

[Tordne]

This is a scary thread! I thought the FAST manifold is supposed to be the bees knees.

I just can't risk any more hair loss :)

[ringram]

Ive been reading a few horror stories with them on LS1tech as well, Id love one, but its too scary. If I was going to drop a whack of cash, Id be looking at Mr Harrops 8 orifice sex device http://www.harrop.com.au/root_folder/harrop_manifolds/amfd7022-00.html

[TAQuickness]

This is a scary thread! I thought the FAST manifold is supposed to be the bees knees.

I just can't risk any more hair loss :)

fo shizle

To ice this cake, I was recently informed it will be 6-8 weeks before I get my laptop back. Last time I buy an extended warranty......

[TAQuickness]

Ive been reading a few horror stories with them on LS1tech as well, Id love one, but its too scary. If I was going to drop a whack of cash, Id be looking at Mr Harrops 8 orifice sex device http://www.harrop.com.au/root_folder/harrop_manifolds/amfd7022-00.html

I can't seem to find the appropriate pornographic smiley for the harrop device. I'm to the point I will not put any more money into the FAST90. I'm giving it just a few more hours of my time, and if that don't work, I dunno.

[ringram]

I imagine you should be able to recover some cash on it. Maybe back to a "ported" LS6? Until something better comes along.

[TAQuickness]

For the money, I'm thinking i might try the blingy PP manifold. They seem to stand up well to the LS6 and Weiand, can be ported, and BLING

[TAQuickness]

well i've been thru 2 more itterations of gaskets and BS, and cannot seem to eliminate the problem. At this point, I have no reason to believe the FAST90 is leaking.

I did notice, however, that when the manifold is set in place, it appears to have a different (wider and angle) gap on the left side vs the right.

Anyone have any suggestions of how I can measure the angle of the intake port deck vs combustion chamber deck with out removing the heads?

[Bruce Melton]

I gave up before I got to it, but I considered making up a couple of mylar sheets that were cut to match the mating area of the intake /head with the idea of shimming the intake up a smidge so it would have room to wedge itself in without bottoming. Obviously a desperate measure but maybe you at that point?
Also, have you checked ( I am sure you have) the MAP gasket? I embedded mine in a big glob of silicone sealer. Real ugly but not visible.

[TAQuickness]

I gave up before I got to it, but I considered making up a couple of mylar sheets that were cut to match the mating area of the intake /head with the idea of shimming the intake up a smidge so it would have room to wedge itself in without bottoming. Obviously a desperate measure but maybe you at that point?
Also, have you checked ( I am sure you have) the MAP gasket? I embedded mine in a big glob of silicone sealer. Real ugly but not visible.


MAP sensor is nicely burried in a giant blob of black RTV. In the last month or so (not much free time), I pulled the manifold again, scrapped out the blue RTV gasket (homemade) and made a black high-temp RTV gasket. This had no effect on the problem, then pulled the manifold again yesterday and filled the left intake port gasket channels with Black RTV, replaced the gaskets, then loosley installed. I let this cure for 24 hours and it effectively made my intake port gaskets 1/16" thicker. I believe this is what you were trying to accomplish with the mylar idea?

I'm really starting to question the geometry of my heads. Perhaps if the left head were milled at a slight angle, it would change the intake flow characteristics enough to explain what i'm seeing.

I'm quite certain the intake manifold is not leaking this time. Passed the starter fluid test. Will be picking up some carb cleaner in the next day or so just to verify.

[Bruce Melton]

MAP sensor is nicely burried in a giant blob of black RTV. In the last month or so (not much free time), I pulled the manifold again, scrapped out the blue RTV gasket (homemade) and made a black high-temp RTV gasket. This had no effect on the problem, then pulled the manifold again yesterday and filled the left intake port gasket channels with Black RTV, replaced the gaskets, then loosley installed. I let this cure for 24 hours and it effectively made my intake port gaskets 1/16" thicker. I believe this is what you were trying to accomplish with the mylar idea? Yes, at least on a Vette it is very hard to get the manifold back far enough with draging it and messing up the RTV.

I'm really starting to question the geometry of my heads. Perhaps if the left head were milled at a slight angle, it would change the intake flow characteristics enough to explain what i'm seeing. Or more likely the stinking FAST is warped which is not that unususal.

I'm quite certain the intake manifold is not leaking this time. Passed the starter fluid test. Will be picking up some carb cleaner in the next day or so just to verify.

Does the stock one fit ok?

[TAQuickness]

I don't have a stocker on hand to try it. Although I should be able to dig one up with relative ease

[TAQuickness]

What do you think the chances of two bottom shells being warped is? I'm on my second one and there appeared to be no difference with just the swap

[Bruce Melton]

Really hard to guess.

There sure are alot of slighly used FAST intakes for sale on the forums..
I suspect there are two reasons:

People install them and are unhappy with the gains, particularly on stock displacement engines.
They have the same problems we have/had and want to bail out without condemning the intake.I was in both the above catagories and the guy who bought it from me sold it for the second reason -he said.

I had a LS6/Shaner before and after my FAST times and it just works. I just put the same LS6 setup on all new engine with same heads and it just still works. This is with some pretty smashed gaskets. Granted, my heads are only skimmed.
What is it that the happy FAST advocates are doing or not doing?

[TAQuickness]

guess all that's left to do is try and ls1/6 manifold.

[Tordne]

DOH!!! Can't believe that it has gone to shit again :bawl:

[joecar]

What does FAST the company have to say...?

[BowlingSS]

I was thinking of getting a 90/90 setup but after reading this thread I might have to think about. This tread causes me to :beer: .

Bill

[TAQuickness]

What does FAST the company have to say...?

Haven't spoken directly to them yet. Indirectly, I've over torqued the manifold :wtf1:

[TAQuickness]

I was thinking of getting a 90/90 setup but after reading this thread I might have to think about. This tread causes me to :beer: .

Bill


I might have one for sale cheap in the near future ;)

I'm not sure I can write it off as the manifold yet. I wouldn't surprise me given the QC issues with the FAST 90tb.

[TAQuickness]

haven't figured out how to get the angle off the heads yet, but the manifold decks are off by .5* left to right

Edit:
and the heads are spot on.

[TAQuickness]

Seems to get deeper.

Manifold no longer leaks, but the left bank is still lean. While installing the fuel pressure sender I was messing around with BIDI and came up with this log.

[TAQuickness]

Another log that might be of use

[joecar]

Interesting, actual AFR's across banks diverge a little when commanded AFR is greater than 14.17, otherwise they are very close...
Could this be due to differences in sensors and/or controllers (check programming...)...?

Why is the timing jumping 10 degrees...?

Why is EGR at 88% during idle, shouldn't it be off at idle...?

http://img147.imageshack.us/img147/7366/taqyv2.png

[joecar]

Let me revise what I said... diverges above 13.65 rather than 14.17...

What is that lean spike on bank 2...?

http://img87.imageshack.us/img87/4877/taq2ey2.png

[TAQuickness]

Interesting, actual AFR's across banks diverge a little when commanded AFR is greater than 14.17, otherwise they are very close...
Could this be due to differences in sensors and/or controllers (check programming...)...?

If I install both WB's on the same bank, they track tighter than frogs hair.


Why is the timing jumping 10 degrees...?
Likely due to the PCM trying to maintain idle


Why is EGR at 88% during idle, shouldn't it be off at idle...?
Good eye... I brought my fuel pressure sending unit in thru the EGR. Working on the tutorial for that now.

[joecar]

You said your manifold no longer leaks (good job... :cheers:)...

TOL (thinking out lound):

So now what can account for the divergence between banks...?

Injector differences...?

Does the divergence follow the injectors if they are swapped across banks...?

Can the injectors be mixed around to cancel out the divergence...?

Edit: can you rule out exhaust leaks...?

[TAQuickness]

I used seafoam to identify exhaust leaks several months ago (car has been parked since then), found 2 leaks and fixed them up.

I have swapped injectors from side to side, random drawing, and replaced all 8.

Only think I can think of at the moment is the small pulse width. You can see in log 63, I had to step the AFR down quite a bit to get the banks to line out (13ish to 1). In log 68, I merely had to get to the lower 14's to line out.

The difference is some mild minimum pulse width tweaking.

Another interesting note. While comanding 15, if i hit the air filter with a shot of starter fluid, the left bank will drop down to the right.

[joecar]

Another interesting note. While comanding 15, if i hit the air filter with a shot of starter fluid, the left bank will drop down to the right.This definitely confirms that [the left] bank 1 is running leaner;

I'm wondering if your bank 1 injector subharness is having some high resistance or other problem....

I would check that each injector connector is getting the correct voltage waveform;
do you have access to a scopemeter (Sears used to sell a $200 DMM/scopemeter suitable for car work)...?
maybe could try an RMS DMM set to AC V and compare all 8...?

[TAQuickness]

I should be able to get my hands on a scope at work. Will take a tank to get there if I have to command 13.8:1, but well worth it.

[joecar]

Have you measured the resistance of each injector (do any stand out)...?

TOL (thinking ot loud)...
We know so far:
a. no intake leaks
b. no exhaust leaks
c. swapped around and/or replaced injectors
d. verified identical behaviour of both LC-1's

That leaves:
1. electrical behaviour of bank 1 injector harness
2. flow behaviour of bank 1 fuel rail (could #7 be full of crud...?)
3. what else can we think of relating to bank 1 (nothing fell into any of the ports...)...?

I don't really think it is 2; if it is, then the fuel rail needs cleaning (but I think you already have a new one, IIRC)...

While engine is running, use intrusive probes (very fine needles that non-destructively poke thru insulation to wire conductor) to read waveform as AFR is manipulated using bidir control; do waveforms show same pulsewidths as is being commanded by PCM, and do all 8 waveforms look identical...?

TOLA (again)...
Possible causes:
a. PCM quad driver is broken/stressed and is not driving the pulse waveform correctly;
b. higher resistance in inkector circuits will reduce the driving current and so the injector will open slightly late and close slightly early (a reduction in pulse width); the reduction is a bigger percentage for narrow widths (lean AFR), and is a smaller percentage for wide widths (rich AFR);

Either way it has come down to: what do the voltage waveforms look like as you command the AFR using the bidir controls.

[joecar]

I like the intrusive probes over the back probes; the back probes can damage the terminal and/or the connector back seal.

Intrusive/piercing probe example (http://us.fluke.com/usen/products/AccessoryDetail.htm?cs_id=34636%28FlukeProducts%29&catalog_name=FlukeUnitedStates&Category=LEAD%28FlukeProducts%29)

Back probe example (http://us.fluke.com/usen/products/AccessoryDetail.htm?cs_id=34638%28FlukeProducts%29&catalog_name=FlukeUnitedStates&Category=LEAD%28FlukeProducts%29)

[redhardsupra]

I like the intrusive probes over the back probes; the back probes can damage the terminal and/or the connector back seal.

Intrusive/piercing probe example (http://us.fluke.com/usen/products/AccessoryDetail.htm?cs_id=34636%28FlukeProducts%29&catalog_name=FlukeUnitedStates&Category=LEAD%28FlukeProducts%29)

Back probe example (http://us.fluke.com/usen/products/AccessoryDetail.htm?cs_id=34638%28FlukeProducts%29&catalog_name=FlukeUnitedStates&Category=LEAD%28FlukeProducts%29)

these sounds really painful...:eek:

[TAQuickness]

They even look kinky

I should have access to these at work.

RHS - I've been meaning to catch up with you and get your take on the logs posted yesterday.

[redhardsupra]

TAQuickness: i only haven't looked at it because i've been sick the past few days. you know where to find me anyway ;)

[joecar]

these sounds really painful...:eek:

They even look kinky...
lol, that's funny... :D I never thought about what I was writing... :muahaha:

[TAQuickness]

I ordered a new PCM from Jes. This should eliminate the injector drivers as part of the problem.

I'll post a log when I get home from my drive to work today.