Backfire only from a dig. Help!

[Rock-a-Lex]

Hello. I need some advice.

First, my engine setup so you all know what I have. SRT stage 3 SC W/intercooler, S&S headers, Walbro 255lph, NGK brk7e coppers (.030), old RC 440cc injectors, Synapse BOV (vta), AEM FIC8.

The car runs decent. Pulls nicely, no CELs, passes inspection. Fuel trims +/-4% while driving.

Lately, when I do a WOT launch, the car almost feels like a backfire or bogging combination. I'm looking at my AFRs and it reads 10.5 - 11. Kind of rich but not sure. If I'm driving a steady 40mph or so and punch it, boost climbs to 6-7psi without any bogging or backfiring; AFRs still at 11. I did find a boost leak near my BOV but haven't fixed it yet. It should be putting down closer to 9psi. The question is what could be causing this to happen only from a stop? Do you think this is tune related only? FYI my BOV is before my MAF so it's not like I'm releasing metered air. Is my map too lean or too rich early in my fuel map? FYI, I do not have my O2s running through my FIC, I decided to let the stock ECU control. Should I go a little tighter on the spark plug gap? There's an adjustment on my BOV for the preload spring to control how fast it opens and closes.

Let me know your thoughts. Thanks

 

[Zuffen]

The first thing I would do is repair the leak and then see how it performs.

No point in trying to sort out the issue when there's a leak in the system.

You could very easily make more issues for yourself.

 

[Rock-a-Lex]

Thank you. Will do.

Also, excuse my ignorance but when I'm doing a boost leak test I plan on putting my tester in place of my cone air filter; pre-supercharger. Since I want to check the entire system I take it that I wouldn't block anything off correct? Ie let the pressure build in the SC, past the BOV, through the IC, up past my MAF, into my TB and stay in the manifold? Is this right?

My previous boost leak test had the tester right after the SC where I then blocked off my IC piping right before the TB. I noticed it wasn't holding past 6psi when I tried to put 10psi in it. I did hear and see a lot of air coming from the BOV outlet (it's vta). I called Synapse and they said that's normal and it's different when the car is running with vacuum. I don't understand as I would think since vacuum keeps it open and lack of vacuum keeps it closed, wouldn't the car off (lack of vacuum) make the BOV stay closed and not leak during this test?

 

[Zuffen]

I think you will find Synapse are correct.

With a turbo (essentially the same configuration) the valve will open without any vacuum, The higher the pressure the sooner it will open.

With vacuum it won't vent or the engine couldn't get up boost to start performing.

I've test the whole system, whilst a leak pre-charger won't have any impact on the final boost figure it would be worth checking anyway.

 

[Rock-a-Lex]

Understood. Thank you.

Is it possible that my SC system is boost leak free but have boost leaking out of my injectors? I remember a year or so ago my friend stopped by with a boost leak tester before I had mine and we tested the whole system.

We found bubbling (soapy water) around every injector; the presssure introduced to the system would drop quickly. I take this isn't normal. We proceeded to take the fuel rail apart to inspect the injectors and to my surprise there were NO O-RINGS!!! We installed new O-rings but didn't know how to source ones that fit my RC injectors with my GS400; so it was trial and error at my local auto parts store. We found some that fit decent snug but they would still fall out if rail was held upside down. I figured it's better than nothing. Here we are today...same O-rings - which makes me wonder.

The shop that installed the kit years before did a shoddy job. The car was running like crap in the beginning but I knew the wiring to my FIC was wrong and tune also probably wasn't right because of it...I never looked into the mechanicals at the time until the wiring was fixed. Then, it was too late to go back to the shop and call BS.

Those RC injectors are very old, back from 2002! I did have them professionally cleaned before initial install though. I'm looking to get new Denso 545cc 12-hole injectors with. The correct O-rings.

Just wanted to share this as well and get your opinion. What would I be experiencing if the car did have leaky/Ill-fitting injectors? Again, the car runs good, idle is a bit bumpy at times but I assumed this might simply be from my copper plugs wearing down. My RPMs go real low sometimes when driving slow and turning slowly (say onto my driveway).

 

[Zuffen]

I think you need to sort out any potential problems, like the injector seals before moving on to trying to get it to run right.

Everything has to be functioning 100% and not "near enough" to get the results you want.

 

[gloverman]

I change injector o-rings on almost every 1uz I install and most that come in with issues need them. Ive seen low end mixtures out as far as 16:1 almost touching the 17s. The engines surge and stall. For little pieces of rubber they made a big difference.

I agree with Rod, fix the things you know are wrong first.

 

[melvinmelvin]

Are O-ring sets for the injectors readily available from Toyota dealers in NZ and/or AUS?
Or do you get them from ebay/amazon or the like?

 

[Rock-a-Lex]

Thank you for everyone that replied. I will work out the injector, seals and O-ring issues out.

FYI, a cool tidbit of info. The centrifugal SC kit I have runs off an oversized main engine crank; not the small power steering pulley that most other kits like the RMM or LMS run off of. This allows me to only need a 3" SC pulley and no need to go smaller to make low 400WHP. The custom billet crank pulley is about 2" larger in diameter than the stock crank pulley; it's bolted right to the stock crank pulley. Stock pulley has the serpentine running all accessories as normal and SC belt is only between SC pulley and custom crank pulley with a 180deg belt wrap. This helps prevent belt slippage. The car pulls very hard as-is. I can't wait to throw a nice new set of 12-hole injectors with the proper seal. Will eventually get some dyno runs in. I'll keep you all updated. Good night