Rich Bog&Misfire During WOT

The car is a 1990 760 Turbo Wagon.-
Performance(engine related) Upgrades Are:
937 ECU TLAO chiped And Naturally Aspirated EZK? Also TLAO chipped. 19T Coldside 15G hotside to fit stock conical Flange downpipe @ 13.8-14.3 PSI w/ boost creep to 15 psi. NPR Intercooler, 550CC/50lb Injectors from deatschwerks, 3 Inch MAF, catless 2.5 inch Exhaust with single dynomax turbomuffler and curved piping over the rear axle, and stock autozone fuel pumps+ IPD intank pump(debating on switching).

Stage 0 Completed+CEL fixed

So its bogging when i stab the throttle, if i ease into it, its better. Only starts bogging during the high end when i reach 9 psi. Sometimes it will misfire too and go "putt, putt, pop" like on those World War I Era Planes and Cars. AFRs Are Rich Rich @ less than 10.0 because AEM widebands don't read any lower.

Now a little background. Before i just threw in the 550cc injectors to see how it would run with the stock 2.5 016 inch MAF. Man holy poop, I could barely get to 1-5 psi before "putt, putt, pop, even the boost gauge was popping around during this."
Then I replaced the 2.5 inch MAF with a 3 inch 012 MAF and its a lot better and I can reach Max boost with less "putt putt pop" until the top end."
Also interesting to note when I decel at max boost and 10 AFRs and let go of the gas, it does a putt putt pop too then goes lean on the wideband. I think the ECU doesn't react fast enough and decrease injector output, so it rich misfires due to lack of air(closing of the throttlebody) then cuts injectors to save fuel.

It is also important to note that my AFRs were less than 10 with (new) stock 330cc injectors. This was post-fixing the CEL but yeah I was running rich with stock stuff too .

So what should I do?
A. Switch to 440CC injectors? I realize that 50 lbs is too much, but man, I really want it to work without having to buy/switch new 440cc injectors. Plus they won't let me return it probably so im going to have to sell it classifieds or something. And what if i still get the rich bog on the 440ccc injectors. I'd be pretty depressed.
B. Give More time to relearn? I've used up about half a tank so far letting it learn, feels better but not quite there yet(Placebo effect).
C. GROW A PAIR AND CRANK UP DA BOOST !!!. I mean its rich so it should work out right? 20 PSI to lean it out maybe?
D. Big ass vacuum leak?

UPDATE FIXED: See Last few Post to see how !!!

Your afr was dipping richer than 10:1 on stock maf/stock injector? That seems like a problem that should've been adressed before upgrading.

C all the way to 25psi

Jack said:

C all the way to 25psi

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your not serious huh?

turbotankshane said:

Your afr was dipping richer than 10:1 on stock maf/stock injector? That seems like a problem that should've been adressed before upgrading.

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Well that could have been when I had the CEL. Now no more CEL. I could switch to stock stuff and see if its normal AFRs. Its not truly stock either. Got from this website. Same flow and impedance but probably made differently and stuff. Oh man, you don't want to see the condition of the original injectors when i first joined this site...

https://www.fiveomotorsport.com/

what's your cold start afr like? Does it start easily or does it take a bit of cranking?

Once its up to temp, do afrs stablize at ~14.7 at idle?

In cruise and light load, are your afrs steady at ~14.7 or do they seem a bit on the lean side?

turbotankshane said:

what's your cold start afr like? Does it start easily or does it take a bit of cranking?

Once its up to temp, do afrs stablize at ~14.7 at idle?

In cruise and light load, are your afrs steady at ~14.7 or do they seem a bit on the lean side?

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Ahaha you ask a good question. Cold start AFRS are rich but not so rich that it goes below 10. On super cold days, 10.5. Then it quickly gets to 14.7 when it warms up/the temp gauge gets to about 10%-15%. Idle 14.7~(goes up and down trying to maintain it) and cruise 14.7~. WOT is a whole different story as i mentioned in the beginning thread.

Yep, I read it. If your cold start, idle and cruise scenario afrs are spot on, why would you think that your injectors are too big, or that you have a large vacuum leak? And if as your boost goes up your afrs get so rich that is starts misfiring, what would make you think that on a maf system with a larger maf that more boost is going to make your efi system inject LESS fuel? I can assure you that 20 psi from any td04 framed turbo isn't going to max the 012 maf out, so as it registers more airflow, LH is only going to inject MORE fuel.

So, test for boost leaks, extensively. If you make 100% damn sure you have zero leaks, and give LH several gas tanks and quite a few temperature cycles to learn the setup, either talk to TLAO about it, or get smaller injectors.

turbotankshane said:

Yep, I read it. If your cold start, idle and cruise scenario afrs are spot on, why would you think that your injectors are too big, or that you have a large vacuum leak? And if as your boost goes up your afrs get so rich that is starts misfiring, what would make you think that on a maf system with a larger maf that more boost is going to make your efi system inject LESS fuel? I can assure you that 20 psi from any td04 framed turbo isn't going to max the 012 maf out, so as it registers more airflow, LH is only going to inject MORE fuel.

So, test for boost leaks, extensively. If you make 100% damn sure you have zero leaks, and give LH several gas tanks and quite a few temperature cycles to learn the setup, either talk to TLAO about it, or get smaller injectors.

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Hmm I was thinking that the 3 inch MAF would scale the injectors properly. Kind've like how 30% airflow reading on a 2.5 inch MAF would be a 20% reading on a 3 inch MAF. I think when it just goes based on the 3 inch MAFs reading at WOT, the Injectors are injecting pulses at a percentile based input. So if the ECU is saying, "Inject 70% capacity," the capacity would be with a 550CC injector instead of lets say a 440cc injectors(less fuel) or 330cc. I think there is a misconception that running a bigger maf will just increase fuel delivery, it actually delivers less at lower throttle and "scales" larger injectors properly. So i guess your right, but man, how do people do it then?

Im pretty sure i've read of some people setups where they would have oversized injectors and run pretty standard afrs, even on small turbos like the TD04 series. They would have like 60-75 lb injectors instead of my tiny 50 lb ones. You don't think I can make it work? 249$ down the drain unless i sell it basically...

Plus TLAO probably has had enough of my questions lol. I guess I could poke him a little more. Im so close to my performance goal for this car. Just need the final piece of this puzzle, then im going to move to trying to cool the engine bay with shielding the intake from exhaust and heat wraps for the downpipe.

update: now that i think about it a little more. I guess the bigger maf diameter is the only reason why it would read differently. I don't think that just replacing the housing of the 2.5 inch maf would get you the same benefits as a original 3 inch maf though.

You reset the ecu each time you swap the injectors or amm right?

Have you done a pressure test and checked for leaks yet?

What are afrs at idle and cruise?

thelostartof said:

You reset the ecu each time you swap the injectors or amm right?

Have you done a pressure test and checked for leaks yet?

What are afrs at idle and cruise?

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Ahhh thank you for your assistance. I owe you.


1. Yes. ECU reset multiple times with any modifications. Half tank of gas worth of learning done on current setup.

2. No pressure test yet. But I did empty two cans of carb cleaner+brake cleaner into all areas, if that helps . Making a impromptu contraption will be much pain for my feeble mind.

I think someone should make a sticky on how to do a pressure test to test for leaks. Noobs like myself have not enough common sense to build their own contraption. I bet someone could make tons of $$ selling prebuilt high quality ones lol.

3. Idle: 14.7~ more or less
Cruise: 14.7~ More or less.
5 psi: 13-12
7PSI: 11
10PSI: 10
WOT: Rich like the starch glycogen concentration in potatoes, especially when boost stabilizes. "Putt Putt, pop" like WWI Planes+vehicles.

Told you in your last thread, give it a full tank to learn before you start doing anything else. Mine would finally start acting somewhat normal about the time I was down to 1/4 tank, halfway into the next tank it was fully learned.

That said, mine still has issues on pump gas but we get crap gas here. Anything over about 10psi mine will go pig rich depending on fuel source, as it is going into knock enrichment mode. There's a simple test to see if that's the issue, but jeezus man, let it finish learning first.

gsellstr said:

Told you in your last thread, give it a full tank to learn before you start doing anything else. Mine would finally start acting somewhat normal about the time I was down to 1/4 tank, halfway into the next tank it was fully learned.

That said, mine still has issues on pump gas but we get crap gas here. Anything over about 10psi mine will go pig rich depending on fuel source, as it is going into knock enrichment mode. There's a simple test to see if that's the issue, but jeezus man, let it finish learning first.

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Yeah sorry, I wanted to consolidate a thread on just this issue. Man that will be kickass if i just need to let it learn more. No money spent or anything ahhaha. I'll take your suggestion and give it a try before changing anything up.

Knock enrichment? I sure hope thats not the issue...

The fact that I may be starting to leak air past 10 psi would make sense why it is running rich at boost. Meaning the connections are only stable up to 10 psi. O I woe the idea of building a custom contraption to test boost leaks . Leave Oil filler cap on or off? I heard im supposed to take the oil filler cap off, block off the exhaust and intake of turbo. i have a big compressor storage of air so thats a plus.

thelostartof said:

https://m.youtube.com/watch?v=AA-p_Bd5DKQ

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AHHH Genius. So I leave my manifold intercooler tube connected to the manifold and listen for any leaks at the vacuum lines going to multiple places? Like the AC, CBV, PCV, and many others? Take off the Idle air controller hose and plug it? Take off the oil cap for safety?

I'll head to home depot sometime this week to do this. Seems really easy to do. if this doesn't work ill let you guys know.

What plugs you running and what gap?

sbabbs said:

What plugs you running and what gap?

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Im curious to this and what parts were used on stage 0

pictures of engine bay would help

sbabbs said:

What plugs you running and what gap?

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First Tried NGK coppers -ES @ .028 . Then tried Gapped at .024 Platinum NGK same result .

Jack said:

Im curious to this and what parts were used on stage 0

pictures of engine bay would help

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Here is a youtube video: https://youtu.be/0Vpn_G4Dmvw

Note: all problems except possible vacuum leaks fixed in the video oh and that strange tach stuff.

Here is it while i was installing the 3 inch mafs CBV vacuum line is not like that atm. dw.:

Did you use the colder 8 NGK plugs? I used the 8's gapped about 25 to fix spark blow out.

sbabbs said:

Did you use the colder 8 NGK plugs? I used the 8's gapped about 25 to fix spark blow out.

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There aren't any available here i think. Could you send me a link? I don't think spark could make that much of a difference but I could try lol.