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TBI Engine performance upgrades question

Discussion in 'The Garage' started by tch777, Sep 29, 2004.

  1. tch777

    tch777 1/2 ton status

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    I have seen the distributer re-curve kits from Accel and Flame thrower as well as the adjustable vaccum advance kits.
    These sound easy enough to install if you can just get wedged in the back of the engine compartment to get to the HEI do these make a noticeable difference for the time and effort?
    Next does upgrading the 4 pin ignition module really make much difference for a DD? Or is that more for a completely hopped up engine.
    Just wondering as I am going to put a little bigger cam in with lifters and flow matched injectors to replace the factory ones with 134,000 on them but keep the cam tame enough that the computer will be happy. Also going to throw in a hotter coil.
    I want to do headers too and a high flow cat into a 3 inch single exhaust with I think a Flowmaster muffler too.
    Anything else I can do on the cheap to wake up the engine a little but not brake the bank?
    I have a K&N air filter, a TBI spacer, a Turbo City velocity stack thingy on the factory air filter housing, and the injector pod spacer.

    I have some ideas right now but if anyone has specific parts that worked great for them let me know that too.

    Thanks

    Tim
     
  2. SUBFAN

    SUBFAN 1/2 ton status

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    Re: Engine performance upgrades question

    Forget about the timing upgrades, your engine's timing is controled by the computer.

    I wouldn't upgrade the coil unless the old one goes bad on you. You are looking at the wrong module also....

    The cam and exhaust upgrades will give a good deal of added performance. The next area to look at will be to upgrade the intake and heads.

    The most noticeable performance you can perform on this however, would probably be a gear swap. Lower gears with that OD trans = /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/woot.gif
     
  3. tch777

    tch777 1/2 ton status

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    Re: Engine performance upgrades question

    I already have 4.56 gears in it!
    Thanks for the info on the parts.

    Tim
     
  4. 91GMCSuburban

    91GMCSuburban 1/2 ton status

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    Re: Engine performance upgrades question

    fuel pressure regulator
     
  5. tch777

    tch777 1/2 ton status

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    Re: Engine performance upgrades question

    Okay which is best the adjustable or the vaccum controlable ones?
     
  6. tch777

    tch777 1/2 ton status

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    Re: Engine performance upgrades question

    okay I give up which aftermarket cams can I run in my 91 SUB with the stock TBI programing. I understand that a custom tuned chip will run everything better but it is not in the budget for awhile.

    Also where can I get headers for my SUB.
    No one lists anything for my 91, what's up with that! And I have to keep a cat for emmisions too.

    Thanks
    Tim
     
  7. 91GMCSuburban

    91GMCSuburban 1/2 ton status

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    Re: Engine performance upgrades question

    I understand the vacuum is better because it changes with the vacuum change.

    As far as Cam, I'm still struggling too. They say you need to get a cam that is computer friendly, but is that with an existing chip or does that include custom chips?

    Headers: I am going with thorley tri-Y's (PN 364Y3). Direct fit. I hear also that flowmasters, even though they sound nice, don't flow well. I have just puchased a Magnaflow cat and muffler (3") and after installed, will let you know how it works.
     
  8. 91GMCSuburban

    91GMCSuburban 1/2 ton status

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    Re: Engine performance upgrades question

    Also, if you are going to "upgrade" your injectors, get the 68# injectors instead and don't mess with buying the "flow matched" ones. This will give you much more for your money.

    The FPR will give you plenty with what you have and be cheaper. If you are worried about your existing injectors, get them tested and cleaned first, then go from there.
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Engine performance upgrades question

    The stock MAP systems have a hard time with camshafts that produce low vacuum. Lobe seperation of 112* or more is pretty typical of "computer friendly" camshafts.

    It's a lot of effort, but much cheaper than buying "custom" chips...you can buy the stuff to burn your own chips, and once you understand everything, you won't get any closer to "perfection" than that.

    You really are throwing away performance and economy by switching engine components on an EFI engine and not adjusting the PROM to match.
     
  10. wayne

    wayne 3/4 ton status

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    You don't need to upgrade the chip but after some decent mods it will help. One thing to consider is your Burb is no lightweight and low end grunt will be of more value to you then upper end horsepower. There are quite a few cams on the market that will work well. No matter what you do a head swap will really wake things up.
     
  11. camiswelding

    camiswelding 1/2 ton status

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    Re: Engine performance upgrades question

    I put a mangaflow 3 inch muffler on with a performance cat (which falls off between smogs)and am getting 1/2 mpg better (Im also going alot faster... maybe 5 mph at the same throttle)
    and have noticed seat of the pants improvement...
    lower engine temp by a couple degrees
    and its quiet...
    definately worth the money
    cost me 400 on my crewcab and it was super sano
    cam
     
  12. 91GMCSuburban

    91GMCSuburban 1/2 ton status

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    Re: Engine performance upgrades question

    [ QUOTE ]
    The stock MAP systems have a hard time with camshafts that produce low vacuum. Lobe seperation of 112* or more is pretty typical of "computer friendly" camshafts.

    It's a lot of effort, but much cheaper than buying "custom" chips...you can buy the stuff to burn your own chips, and once you understand everything, you won't get any closer to "perfection" than that.

    You really are throwing away performance and economy by switching engine components on an EFI engine and not adjusting the PROM to match.

    [/ QUOTE ]

    So are you saying that our only choice is to buy a cam that works well with a computer or just with the stock one?

    I plan to burn a new chip based on all my upcoming mods, and the only thing that is holding me back is this:
    Buy a cam to fit the computer (chip) or buy the chip to fit the cam and mods (regardless of whether it is computer friendly)?
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Engine performance upgrades question

    To my understanding, without some SERIOUS work to the chip, a rough idling cam is not going to work with a MAP system. More than what you would find from a custom chip burner.

    To get a burn actually correct, the data needs to be interpreted as the ECM sees it. You can try to work up a formula for what your engine mods might need (and most chip companies do this) but anyone that tunes engines will tell you that no engine is going to require exactly the same amount of X (say, fuel or spark) and thus, a formula (or what worked on one engine) will only get you so close.

    When you run the ragged edge of "streetability" with an EFI system, there is a LOT of tuning necessary with the PROM to keep from having issues.

    I say build your engine around the system it will be running on, and THEN get a new PROM.

    Heads, compression, exhaust, intake, all that causes no problems with the ECM, and is easy to factor into the PROM. Low vacuum ("big" cam) is not something you can easily work around.
     
  14. 91GMCSuburban

    91GMCSuburban 1/2 ton status

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    Re: Engine performance upgrades question

    Makes sense! Thanks for the info...
     
  15. tch777

    tch777 1/2 ton status

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    Re: Engine performance upgrades question

    Hi guys thanks for the information. But here is my pickle I have to pass emmissions. So I don't want to go really wild. And while I really like the idea of bigger injectors I think at this altitude they might hurt me more than help 6000 up to 10000 ft. I just need more air, I think the current size injectors can keep with what I want to do if I could just get more air thru the engine for them to push more fuel. Also this is a SUB so the cam I pick is going to be more of a torque cam, the biggest I would go is to one that shows great performance in the 1000 to 5000 RPM band instead of an idle to 4000 RPM band. Plus what if I run the Rhoads lifters? They are supposed to tame a bigger cam down at the lower RPMS to run like a smaller cam and produce more vaccuum too, but then they let your cam run full potential at a higher RPM. I found a couple cams that sound good to me the Edelbrock Performer Plus # 3702second to last in the Performer-Plus section. And the Comp Cams #12-304-4, RPM range 700-4700, or #12-388-4, rpm range 1000 to 5000, spec sheet scroll way down to computer controlled section.

    Also on the MAP deal Turbo city has a MAP adjuster to tweak the MAP so it is happy with a bigger cam and headers, it is 99 bucks. clicky And like I said before a custom chip will really make the add ons run to their best potential but with all I am doing an extra 250 to 300 bucks is not going to happen at the same time. Maybe later on but then I would still need to get an ADL recording to get everything right and how much would that cost me? So I really want to do add ons that work with the stock programming yet can turn up the HP and tq, realizing a little later on I can squeeze a little more with some better programming.

    So is that the general opinion that the flow matched injectors are not worth the money? I thought they were a good deal. A new injecotor is 60 bucks and an flow matched one is 73 bucks. Or should I just rebuild my own injectors I don't know of anyone in the area that can test them.


    Thanks for the part number on the headers, anyone try the headman torq step headers, looks like they have a part number for the Sub but the A/C bracket needs tweaking?
    Thanks guys
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Engine performance upgrades question

    I don't know about that "MAP adjuster". Looks like a hokey piece of equipment to me...you just trick the computer into thinking you have different manifold vacuum than you do. How does that exactly help things? Everything will be a lie at that point, since many sensors (TPS, RPM, O2) are looked at and compute against the MAP readings.

    Efficient components are going to be worth a lot on those stock TBI motors. The heads are garbage for one, and exhaust is typically an "easy" (for the price) 30-40HP on a 350 over manifolds.

    Small mods can be handled no problem by the ECM, but MAP is much less "adaptable" than MAF for you to just throw components on and hope for the best. Witness the people (on this board even) that have burned holes in their pistons from hot engines trying to run on stock components and programming.
     
  17. tch777

    tch777 1/2 ton status

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    Re: Engine performance upgrades question

    Dorian,
    I have to agree the MAP deal looks a little odd and I would probably discount it as junk, except it is coming from Turbo City. They have been around the TBI performance scene for sometime now and have been written up with good results by a few of the magazines out there. I guess the MAP deal would trick the computer maybe it is tricking it just enough to keep everything else happy so you don't burn up the engine. Not sure but the wife is getting close to green lighting more stuff since the Sub is her DD. I just have to make sure we can still pass emmissions when all is said and done.

    Tim
     
  18. Thunder

    Thunder 3/4 ton status

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    First thing to do is exhaust. 3" with flowmaster will be fine.
    You cant build power with a cam and bolt ons to increase air flow if you cant get the gasses out the pipe.
    Recurve kits are not available for TBI. Computer controls everything.
    However some Ignition mods will help TBI. A module with more dwell will help build more low end. The MSD blaster or Screamin Demon coil are also a good add on. Good wires also. Taylor/MSD.

    For a good computer frendly cam just get a Edelbrock perfomer TBI cam and the intake manifold that come as matched set. They are good low end cams

    I would not do much more than that. You are limited by your heads.
    Dont need an adjustable MAP sensor. They do work but you dont need one if you run a mild computer cam.
    dont need a custom chip if you run a mild cam. If you want a little more power set the timing up 4* higher than stock and run 89 or better octaine.
    Dont need bigger injectors the stock 55 lbhr are fine for what you want to do, unless you go with bigger heads.
    Get an adjustable fuel pressure regulator. Set between 14-15 lbs.
    Thes mods have worked good for me on more than one TBI truck.
    You will end up with a good running truck and should be able to pass emissions no problem.
     
  19. hawkeye649

    hawkeye649 1/2 ton status

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    Re: Engine performance upgrades question

    [ QUOTE ]
    Hi guys thanks for the information. But here is my pickle I have to pass emmissions. So I don't want to go really wild. And while I really like the idea of bigger injectors I think at this altitude they might hurt me more than help 6000 up to 10000 ft. I just need more air, I think the current size injectors can keep with what I want to do if I could just get more air thru the engine for them to push more fuel. Also this is a SUB so the cam I pick is going to be more of a torque cam, the biggest I would go is to one that shows great performance in the 1000 to 5000 RPM band instead of an idle to 4000 RPM band. Plus what if I run the Rhoads lifters? They are supposed to tame a bigger cam down at the lower RPMS to run like a smaller cam and produce more vaccuum too, but then they let your cam run full potential at a higher RPM. I found a couple cams that sound good to me the Edelbrock Performer Plus # 3702second to last in the Performer-Plus section. And the Comp Cams #12-304-4, RPM range 700-4700, or #12-388-4, rpm range 1000 to 5000, spec sheet scroll way down to computer controlled section.

    Also on the MAP deal Turbo city has a MAP adjuster to tweak the MAP so it is happy with a bigger cam and headers, it is 99 bucks. clicky And like I said before a custom chip will really make the add ons run to their best potential but with all I am doing an extra 250 to 300 bucks is not going to happen at the same time. Maybe later on but then I would still need to get an ADL recording to get everything right and how much would that cost me? So I really want to do add ons that work with the stock programming yet can turn up the HP and tq, realizing a little later on I can squeeze a little more with some better programming.

    So is that the general opinion that the flow matched injectors are not worth the money? I thought they were a good deal. A new injecotor is 60 bucks and an flow matched one is 73 bucks. Or should I just rebuild my own injectors I don't know of anyone in the area that can test them.


    Thanks for the part number on the headers, anyone try the headman torq step headers, looks like they have a part number for the Sub but the A/C bracket needs tweaking?
    Thanks guys

    [/ QUOTE ]

    ADL reading = Free

    Search for "Win ALDL"
    The cable is easy to make too.
     
  20. hawkeye649

    hawkeye649 1/2 ton status

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    [ QUOTE ]
    First thing to do is exhaust. 3" with flowmaster will be fine.
    You cant build power with a cam and bolt ons to increase air flow if you cant get the gasses out the pipe.
    Recurve kits are not available for TBI. Computer controls everything.
    However some Ignition mods will help TBI. A module with more dwell will help build more low end. The MSD blaster or Screamin Demon coil are also a good add on. Good wires also. Taylor/MSD.

    For a good computer frendly cam just get a Edelbrock perfomer TBI cam and the intake manifold that come as matched set. They are good low end cams

    I would not do much more than that. You are limited by your heads.
    Dont need an adjustable MAP sensor. They do work but you dont need one if you run a mild computer cam.
    dont need a custom chip if you run a mild cam. If you want a little more power set the timing up 4* higher than stock and run 89 or better octaine.
    Dont need bigger injectors the stock 55 lbhr are fine for what you want to do, unless you go with bigger heads.
    Get an adjustable fuel pressure regulator. Set between 14-15 lbs.
    Thes mods have worked good for me on more than one TBI truck.
    You will end up with a good running truck and should be able to pass emissions no problem.


    [/ QUOTE ]

    TBI engines run best on 89 o-tang (the fruity drink with a kick) even stock. I run mine at maximum vacuum with no pings (don't know the advance, I have no timing light) and on 89 with no problems. When it was 0* it ran crappy (even dieing once) on 87.
    Just honest oppinion.................. /forums/images/graemlins/thumb.gif /forums/images/graemlins/k5.gif
     

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