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Thread: TBI stroker SBC tune

  1. #1
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    TBI stroker SBC tune

    Hi,
    Continued from Intro Post "learning curve".
    1992 K1500 Blazer 4x4, Vortec headed SBC 6.3 stroker, TBI 65# bored to 1.930", NV3500 5 speed.
    replaced ignition parts chasing misfire, cap, rotor, module. changed fp to 12 psi to bring the tune as close to stock as possible as a starting point. Hooked up the heat to the NB that is hooked to the ECM.

    Runs good at idle and cruise, stoc with crossovers, even a part throttle tip under a load and it lugging a little, ain't half bad. But when I lug it and dump it to WOT a get a single lean pop followed by what feels like a dead miss as RPMs come up.

    it's got to be a bad spark plug. if it was mixture distribution or lean mixture it should be popping out the intake.

    Is the stock tune that far off? 299 AWLD.

    I'm starting to dislike TBI and yearn for TPI or MPFI. Is anyone happy with TBI performance?

    Certainly I'll check the plugs and maybe compression, it better be good on a fresh build.

    Anyone running First Fuel Injection tuned port setup?

  2. #2
    Fuel Injected! BLG355's Avatar
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    It sounds to me like it is mega lean and you need more fuel. I'm running 22psi with 65# injectors on a 350 and I am maxing out IDC at 5600rpm.
    My Build: 95 K1500, 355ci w/ OEM roller setup - zero decked, Eagle steel crank, Scat bushed H-beam rods, Speed Pro 2V flat top pistons - Rotating assembly balanced. Dart 165cc Iron Eagle S/S heads - 72cc chambers - 1.94 / 1.50 valves. Isky roller cam - 204/209 dur @ .050 - .480/.496 lift with Comp Magnum 1.6 rockers, Edelbrock 3704 intake - Bored to 52mm - 454 throttle body, Delco EP381 fuel pump @ 18 psi running through 80# 454 injectors. Hedman Headers into 3" Dynomax exhaust.

  3. #3
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    Thanks,

    this test was stock chip, 12 PSI, 299 AWLD.

    The AFR was 12.5 on the WB on WOT and 14.6 at cruise, light tip-in and idle with crossovers, 12.3 AFR open loop fast idle.

    I'll try more pressure and even the Harris chip, I was running 20 Psi with it but the idle surge it causes pissed me off, when I had an auto trans it was gone in closed loop but now with stick it's there at every stop light.

    If it's a mixture distribution issue or cracked plug though all the tuning in the world won't fix it.
    Has GMPP 4BBL Vortec manifold with 1/2 thick Carb/TBI adapter and 1" TBI Closed "individual barrel" spacer!

    I want to make sure my tune up is strait before I get into logging.

  4. #4
    Fuel Injected! BLG355's Avatar
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    Quote Originally Posted by mtrhead View Post
    Thanks,

    I'll try more pressure and even the Harris chip, I was running 20 Psi with it but the idle surge it causes pissed me off, when I had an auto trans it was gone in closed loop but now with stick it's there at every stop light.
    I had the worst luck with a Harris chip. I seriously, like hardcore seriousness, swore I had an ignition problem with his chip. I went through half a dozen chips with him and he ended up telling me I had bad cylinder heads...but yet I could install the stock chip, advance the base timing 8-10 degrees, and the truck ran ok. I tired stock injectors are high pressure, larger injectors at lower pressure...same results. His chip was so bad, from 2000rpm and up it had a complete dead miss to it. I tried everything he wanted me to, he swore it was ignition, and it felt like it...but it what his tune. I got a starter chip from EagleMark and never looked back.

    My truck was surging at an idle because it was too lean. it would surge enough to enable AE which made it worse. I wanted to really fine tune so I bought everything I needed and started messing around and learning as much as I could from these guys, they are all great. From my limited experience, when the IAC counts are good and it surges, it needs some more fuel.

    Has GMPP 4BBL Vortec manifold with 1/2 thick Carb/TBI adapter and 1" TBI Closed "individual barrel" spacer!

    That's something I'd like to see a picture of! I have no personal experience with the adapters and spacers on EFI however I see on here often and other forums about the vacuum leaks people often miss with these. That could mess your idle up too I guess but I'd bet on more fuel first.

    BLG
    My Build: 95 K1500, 355ci w/ OEM roller setup - zero decked, Eagle steel crank, Scat bushed H-beam rods, Speed Pro 2V flat top pistons - Rotating assembly balanced. Dart 165cc Iron Eagle S/S heads - 72cc chambers - 1.94 / 1.50 valves. Isky roller cam - 204/209 dur @ .050 - .480/.496 lift with Comp Magnum 1.6 rockers, Edelbrock 3704 intake - Bored to 52mm - 454 throttle body, Delco EP381 fuel pump @ 18 psi running through 80# 454 injectors. Hedman Headers into 3" Dynomax exhaust.

  5. #5
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    Ok, I have to look up AE to see what it is.
    the adapter is similar to the following, but mine is made better, custom not mass produced and centered not all the way to the back like the one I've referenced. http://www.ebay.com/itm/Trans-Dapt-P...89c0e0&vxp=mtr s

    the spacer is just 2 2" holes through a 1" plate aluminum. Idles too nice to have a vacuum leak but I'll spray the gaskets and see if RPM changes.

    I have not tried cranking up the timing it is at 0 base and I'll try some more before I bail on the stock chip and drop the Harris one back in. I should not need as much as your config did because I have fast burn heads and .035" quench which I think may help reduce timing requirements.

    when I flip the throttle body to change fuel pressure I'll take and post some pics.

    the harris chip actually works pretty good at WOT, but idle and very light throttle is no good.

    I don't know which table he took the fuel out of to try to get it to tolerate the higher fuel pressure at low RPM.

  6. #6
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    Take the Harris chip out and burn it!!! It will never run right with it. Then get to adding timing. Switching to Vortec heads REQUIRES 6-8* more timing nearly across the board compared to TBI heads. The big carb intake takes up to double the AE fuel which can only be tweaked in the chip. Then you need to look at BPWC and VE tables.

    You will also never get anywhere with 12 psi and 65# injectors. Try more like 26-30 psi.
    Last edited by Fast355; 09-06-2014 at 06:33 AM.

  7. #7
    Fuel Injected! BLG355's Avatar
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    Quote Originally Posted by mtrhead View Post

    I have not tried cranking up the timing it is at 0 base and I'll try some more before I bail on the stock chip and drop the Harris one back in. I should not need as much as your config did because I have fast burn heads and .035" quench which I think may help reduce timing requirements.

    the harris chip actually works pretty good at WOT, but idle and very light throttle is no good.

    I don't know which table he took the fuel out of to try to get it to tolerate the higher fuel pressure at low RPM.
    I would say since you have a surging idle, you need fuel across the board. If it is not getting enough fuel across the board, it will try to compensate. But there isn't enough at 12psi. I was running logs when I first got Marks chip, I had a rough surging acceleration. I had the "18 PSI" spring in, which was more like 14.5-15psi. I made my regulator adjustable, I used a smaller spring inside the normal spring and ended up with 16-30 adjustability. At 15psi on 65# injectors, I had a surging/missing feeling. It felt like a bad plug or something with the ignition. I kept upping the pressure a couple PSI at a time, it wasn't until I was just around 20psi that it was smoothed out, but Mark said I was too lean top end, so I kept going and 22psi was the point where it was ok, but just ok. Since then, I added headers and bored the intake out to 52mm, I am going to get a larger throttle body eventually and I am planning on settling in around 25PSI or so. I agree with Fast355, I think you need at least 25psi. And your should burn the Harris chip. I spent more money wasting my time with him and his garbage tune then I did in all my tuning stuff and my $430 headers combined.

    I actually made a BIN from my Harris chip to try to figure out what the heck he has so screwed up, mine ran good at WOT, but everything else was horrible.

    BLG
    My Build: 95 K1500, 355ci w/ OEM roller setup - zero decked, Eagle steel crank, Scat bushed H-beam rods, Speed Pro 2V flat top pistons - Rotating assembly balanced. Dart 165cc Iron Eagle S/S heads - 72cc chambers - 1.94 / 1.50 valves. Isky roller cam - 204/209 dur @ .050 - .480/.496 lift with Comp Magnum 1.6 rockers, Edelbrock 3704 intake - Bored to 52mm - 454 throttle body, Delco EP381 fuel pump @ 18 psi running through 80# 454 injectors. Hedman Headers into 3" Dynomax exhaust.

  8. #8
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    OK, I'll crank up the timing to 6 base, stay with the stock chip for now, more pressure later, one change at a time. I made my regulator adjustable, but have only taken it to 22 psi. at the extreme lowest end of the adjustment it gives 12.5 psi. I too have the 18 psi spring, I'll see how high I can get it go and still be stable, I'd prefer an external regulator because I need to remove the TB each time I want to change it. EGR is plugged right now.
    Harris was good about not taking more than initial money, answered a thousand emails, time to move on. I washed the cylinder walls on a 406 75# injectors back in 2003 with someone elses custom chip I forget who. Time to learn up.
    Yellow wire feeds electric fan relay signal, pink wire power to the heated NB o2 sensor. The brass shrader valve tapped into the pod is for checking fuel pressure.IMG_0370.jpgIMG_0371.jpgGOPR0019.jpg
    I'm looking at a used tuned port system tomorrow, if the price is right I may bail from TBI.

  9. #9
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    mtrhead,

    I wouldnt bail on the TBI setup just yet unless youre dead set on a different look. Either system you use is going to require tuning anytime you modify an engine. If you have dealt with Harris chips your obviously patient, which is a virtue in this trade lol. You shoud also step up to a wideband O2 especially for tuning WOT as the NB isn't sufficient beyond stock applications(even then falls it short). One thing to take into account is just because you set to afr to 12.5 doesn't mean it actually achieves it. Also, if you are in an area that runs at least 10 percent ethanol in the fuel, you should account for that as well as it takes more ethanol to have the same btu as 100% gas. Just my 2cents worth.

    Buddrow
    If it don't fit force it, if it don't force fit f&%@ it!

  10. #10
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    I bumped the base timing from 0 to 6 degrees and the truck liked it, much better manners. No more does it feel like it's misfiring. the WB is reading is now generally leaner since the timing change, perhaps the vacuum improved and the MAP pulled it lean. I was able to run for 15 seconds at WOT between 2500 and 5000 RPM in 3rd gear, and it took while to get rich but it went to 10.1:1 AFR as RPM passed I guess about 4000, I was doing 80 so I had to get off it. I couldn't even achieve 5000 with 0 base timing. Next I'll start raising FP until it feels ready to start logging, I guess once that lean reading on the WB is better on idle, cruise and tip-in. Someone mentioned going richer with 10% ethanol, Hmm I hadn't thought of that.

    I feel much better about future prospects of this build, thanks to the contributors, it's greatly appreciated. I'm looking at an after market tuned port setup tomorrow and will much less generous with offers due to recent events.

  11. #11
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    Is your fuel pump adequate to provide higher fuel pressure? I run a TPI pump at 20 lbs FP with 75 lb injectors. as stated you need more AE fuel. A WB would be helpfull.

  12. #12
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    Quote Originally Posted by Ronny View Post
    Is your fuel pump adequate to provide higher fuel pressure? I run a TPI pump at 20 lbs FP with 75 lb injectors. as stated you need more AE fuel. A WB would be helpfull.
    I'm running a TPI pump already and have WB with dash display, 2 sensors total.

    I spoke too soon on my last post, I drove the truck 120 miles to pickup the First TPI setup Sunday and the truck runs Rich on Cruise, 13.5-14.2 on the WB, CEL came on, probably because no cross overs or other O2 sensor issue. I saw some lean readings on the trip during throttle changes. The WOT test last week showed 10:1 afr at 5000 RPM, which shows good fuel delivery for 12.5 psi. I either need to change from Cop car to stock 5.7 injectors or lower fuel pressure even more, 12.5psi is the lowest it can go with the current spring. I have to check the pressure again and codes.
    Maybe the NB quit and pushed AFR rich. I don't think fuel flow would be controlled well at a lower pressure.

    if the nb is good, it may be time for a custom starter chip to take fuel out. It's time to log and start learning to make sense out of logs or get help with analysis.

    I picked up a first fuel injection TPI setup, with all the wiring, regulator, relays and 7730 computer with a label on it saying it was a custom chip. it was all in an 85 Monte, 5.7 so wiring removal was pretty easy.

    I think I'll stick with TBI for now, it will be good to learn on before adding the added complexity of TPI. I'm switch the accessory brackets to TPI to be ready.

  13. #13
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    Are you using a heated NB?

    top down solutions sells a 12-20 lb spring...

  14. #14
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    NB is heated, it was running for years without the heat, but it is hooked up now. I'm going to look into seeing if one of my outputs from the WB can be wired into the ECM for a NB adapted reading and ditch the actual NB.

    I'm able to achieve 20 psi with my setup, I'll check them out though, if it's external I'll block the internal one off and use it.

  15. #15
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    I pulled the codes, 32 and 42 both indicate electrical faults, open/short to ground on the EGR solenoid circuit and est circuit. they live close to each other so I know where to look. neither of those indicate why the mixture was rich on the WB. this Rich while cruising stuff started after I hooked up the power for the heat on the NB, I'm going to look at grounds VERY carefully and get the NB, WB and ECM on the same and confirmed good grounds, same for EST and EGR solenoid circuits.

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