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Thread: What efi system is best for a 4.5 pfi cadillac engine7

  1. #46
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    From what I'm reading, are you "only" adjusting the BPW up and down to arrive at these blm results? I seem to recall a thread that tuning with BPW will tend to be rich for lower MAP values and lean for higher MAP values, so it's not a linear curve. If you have ve cells that are 96 and you're showing blms of 135ish, it's a safe bet the 5.0 injectors will do you good.

  2. #47
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    Thanks Stew.I had globally lean.was trying ve table adjustment with each number I increased bpw.I just never had a bpw starting point since I have so much mismatched parts.the 148 stock setting I started with never worked because my timing was out due to spark latency being incorrect. So when I corrected it I never tried just starting over at 148 bpw.I'm at 153 now and running decent accept for a stumble I get if I don't roll on the the throttle.I also tried one burn with bpw at 154 and changed injector bias to .37 from .4.it didn't run well at all on that one.a lot more stumble. Once I get a nice day I plan to try the 5.0 injectors that I just gave an ultrasonic bath to.change bpw and see what I get.
    Last edited by S.O.B.B.; 01-31-2018 at 07:41 AM.
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  3. #48
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    Found some info on threads here about injector bias and how bpw adjustments make it rich or lean at one end or the other.it would seem I've been adjusting the wrong things.did one burn with injector bias at .41 from .4 and that made a difference.no log yet but more reading to do.think I'm going to start again.gonna remove 4.5 injectors and clean them and try it.once weather permits.had an accident at work last week and dislocated my shoulder so I'm a little limited for mechanical work right now till this heals some.more time for reading
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  4. #49
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    Can anyone verify flow ratings for tbi injectors.I'm reading the 3 conflicting flow rates.gm5235279 are 5.0L and flow I've read 40 50 54lbs/hr.gm 5233203 are 4.3L and flow I've read 37 40 45lbs/hr.that's the two sets I have but knowing what flow rating to use to calculate a starting point for bpw is what I'm after. Thanks
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  5. #50
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    That's funny ran into that issue couple of months ago with conflicting internet hits. I leaned on gearhead-efi being more accurate than the others, however if you still don't believe the posted numbers, download some 4.3 and 5.0 bins, reverse the bpw math calculations and that would be your definitive answer.

  6. #51
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    I did do that and to get the tunerpro bin stock bpw numbers to match with Dave w's bpw calculator I get 46lbs/hr in 4.3L injectors and 49lbs/hr on 5.0L injectors. That gives me a starting point.I'm guessing I'll have to increase the injector bias a little more.I have a log but haven't checked it yet.but it drives better with a lot less stumble.
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  7. #52
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    Hello Dave w.can u or anyone else confirm something. I am using an older $42 xdf and have min temp for egr to max.do I have it backwards. Should I have it set to minimum to keep egr from being comanded on.I used the bpw calculator to come up with 144 and I've gone from .4 to .49 on injector bias and still using the 45lb/hr injectors at 11psi. My logs got better but I'm still lean at above 50 kpa map.raising injector bias has gotten my blms very close to 128 at 30 and 40 kpa.but my ve above 60 is higher numbers than desired. 96 and still 150 blm in some areas.how much can injector bias be raised b4 it causes a problem.I haven't had the time or weather to change to the 49lb/hr injectors yet.any pointers are appreciated. Thanks.I've been ok reading and figuring out most of the issues I'm having but it's awesome that so many good folks on this site are willing to help.I'm hooked for good
    Last edited by S.O.B.B.; 02-16-2018 at 06:41 AM.
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  8. #53
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    Quote Originally Posted by stew86MCSS396 View Post
    From what I'm reading, are you "only" adjusting the BPW up and down to arrive at these blm results? I seem to recall a thread that tuning with BPW will tend to be rich for lower MAP values and lean for higher MAP values, so it's not a linear curve. If you have ve cells that are 96 and you're showing blms of 135ish, it's a safe bet the 5.0 injectors will do you good.
    Yes I'm quoting myself...you can adjust bpw up and down all day long. No matter which direction you go, lower MAP numbers will tend to be richer than higher MAP numbers. If you continue to tune this way, I think I would pursue 126-128 blms in the higher MAP numbers, then crunch the math for the rich idle/low MAP cells.

    IIRC...EGR off is controlled by 3 scalars. Just download the latest xdf, apply the patch and be done with it.
    Last edited by stew86MCSS396; 02-16-2018 at 11:35 AM.

  9. #54
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    Thanks.I do have xdf that has the patches available. I just haven't had the time to fully read all the things the xdf I have doesn't. Been wanting to use the newest xdf but the names of some things being different from one to the other xdf kinda confused me.after checking location to verify it's the same setting I'm playing with I figure I should take the time to verify each item so I understand just what I change.the bpw I have left alone at 144 last 4 logs and been raising injector bias.went from .45 and now at .49.. and that's gotten it better so far than raising bpw.had been up to 153.but 144 is what the calculator comes up with.thanks for the help.it's very much. appreciated.
    Last edited by S.O.B.B.; 02-16-2018 at 02:56 PM.
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  10. #55
    Super Moderator dave w's Avatar
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    I don't change the injector bias for factory stock injectors.

    Correcting the VE Table is a good option to correct BLM's. Increasing the VE Table numbers will lower the BLM, meaning increasing the VE Table numbers will program more fuel spray out of the injectors. More fuel out of the injectors should lower the BLM.

    dave w

  11. #56
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    I started messing with injector bias because I went from stock bpw of 148 for 305cid to 142 for my 273cid and all numbers up to 153 and still have lean at higher kpa map so after reading some about injector bias I figured I try it and it definitely improved throttle response and got rid of most of the off the line stumble it had and it gave me some rich blm numbers for once so it thought I was going the right direction.I just have no way to copy a starting point because my set up never came factory in anything the way I have it set up.ie tbi on a pfi engine.from what it read the heads on the tbi are not the same as pfi and I don't know but doubt cam would be exactly the same.but if I use the calculator for bpw I get 144 for 45bl/hr injectors. So thats what I started at with the bias at the stock .4.it ran lean and like a miss and not near enough fuel.I'm hoping to get the 49lb/hr injectors in it as soon as weather permits and put bpw at 133 for those and not sure if I should put the bias back at stock setting. It's st least been a lot better on fuel snd more fun to drive.thanks for the tips.I'll keep playing till I get it.I got a zif socket and ten more chips and laptop car charger so at least now I can get 45 min logs on my drives to and from work.and I have a fairly large hill with a good incline that's about a mile or more long so that gave me more data collection range i couldn't get on flat driving.I don't know where the power curve is or should be on this engine.the stock ve table didn't give good results.the 273 may be close in hp and torque to a 305 but the power comes way earlier in the rpm range.I doubt I'll ever Rev this engine to 5000 rpm.its rated at 180hp at 4400rpm and 245 lbs at 3200rpm.so it's all been guess work for me and getting help on here has been great.
    Last edited by S.O.B.B.; 02-17-2018 at 07:31 PM.
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  12. #57
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    Dave w I had also changed injector bias because the tbi calculator from Eagle Mark does change injector bias with fuel pressure changes. I have 11 psi fp.all the ratings for injector flow I'm guessing are at 13psi fp.I know I went the opposite of what it calculated but that came from reading Eagle Marks posts in bpw and injector math where it said more fuel will come from raising injector bias. Anyway I put the injector bias back at .4 and bpw to 155.it feels less responsive and has the bog back but the blm numbers in my log are better.I added to ve where it showed lean and took away where it was rich.using your blm correction.I go a little less than it says.so I'm guessing I'm still off on my bpw a bit due to not knowing exact flow.next burn I'll try raising bpw a few numbers and see what that gets me.if i seem clueless please correct me.thanks.
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  13. #58
    Super Moderator dave w's Avatar
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    I don't change injector bias. That doesn't mean changing injector bias is the wrong thing to do. If the "tune" responds positively to a change of the injector bias, that's a good clue that the injector size is not optimal. Maybe there is not an optimal injector? Usually there is stock injector and stock fuel pressure option that works without an injector bias change, but not 100% of the time. Possibly a 502 TBI engine would need the help of an injector bias change to get a working "tune"? Using stock 454 injectors and stock fuel pressure on a 502 is very marginal! Using stock 454 injectors and stock fuel pressure on a TBI 383 is near optimal. Keeping BPW + / - 5% of 135 is a good tuning plan. A BPW above or below + / - 135 will be a challenging "tune".

    dave w

  14. #59
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    Makes sense to me.I burned a chip for my drive home.bpw 157 and injector bias at .4 and that gave blms in 115 to 132 so I'm just playing with the ve table taking away from most areas so i'll see on my drive to work in the morning how close I can get it now that I have room for fine tuning.it is running better than it has under heavy load.so thanks for all the info to all.got me pointed in the right direction. Thanks again Dave w.
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  15. #60
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    Finally had some time to do more than read logs and make changes.made a blm history table.that works great.not done but running much better.is there any correction table like this for spark advance.
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