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TBI to TPI harness questions

POORBOYK5

POORBOYK5

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So my 91 K5 is TBI (obvioulsy) and the plan is to put a 454 and convert it to tbi which is taking more money and time than I have right now. SO, I'll be pulling the big block back out until its complete and ready to go. I have a 91 long block 350 to stuff back in there. I also have a complete TPI set up kicking around...

The TPI is batch fired IIRC. 4 and 4 correct? A tbi has 2 injector leads....
My question is... Could a TBI harness be slightly modified to control a TPI injection set up? Or would it have to have a mass air etc to run right. The TPI set up is an 87 out of an IROC.

Thanks in advance for any help!
 
The simple answer is yes, you can convert from TBI to TPI. There are several different way$ to convert TBI to TPI. If I were to convert a 91 TBI pickup to TPI I'd start with changing the ECM from a '7747 to a '7730. I did something similar in this post ( http://coloradok5.com/forums/showthread.php?t=270253 ) I would use the MAP sensor TPI, or convert a MAF TPI system to MAP TPI.

If you go the '7730 route, then when the budget allows for the 454 you can do like I did for a port fuel injected 454. http://coloradok5.com/forums/showthread.php?t=253871&highlight=454+mpfi

http://coloradok5.com/forums/showthread.php?t=254023&highlight=454+mpfi

Anyway, that's what I'd do / did:D

dave w
 
I have another low cost option to convert from TBI to TPI. The '427 ECM converted to Port Fuel Injection is a $$$ money saving option. Modify the '427 Memcal, and it's ready for Port Fuel Injection. The '427 can even operate a 4L80E / 4L60E.:D

I don't think very many / if any readers are going to convert to '427 ECM, but then again ... how else can the conversion cost less than $100 when converting a TBI to TPI???

dave w

PFI Memcal Mod.JPG
 
dave do you burn chips? Do you burn chips for CK5 Brothers?? I saw the thread on thirdgen on converting the 747 to the 730 via repinning, dropping the MAF, etc... Looks like that'll be the route I take. But the info on the Port inj for the 454 is very exciting! We'll be in touch about that a little later, Gots lots a questions about that one!!!
 
Sure, I can burn chips. I can't be 100% accurate with the first chip. I need data logged information to be 100% accurate.

I think the upgrade I did on '427 PCM ( http://coloradok5.com/forums/showthread.php?t=270253 ) is the best way go if you if you even thing there is a slight chance of having future plans for a 4L80E / 4L60E? The '427 PCM is more affordable, mostly because finding a '7730 / ' 7727 V8 Memcal is $$$.

dave w
 
ahh I see. No plans that I can see for a 4l60/80e. I'm running a TCI 700r4. Its a couple years old and I'm liking it so far. as for memcal are you referring to the "prom"? I'm new to the computer modification world. is there a inexpensive program I can use to log data with?
 
NEWENGLANDK5 said:
as for memcal are you referring to the "prom"? I'm new to the computer modification world. is there a inexpensive program I can use to log data with?
Click to expand...

The '7730 use a Memcal, which has the PROM, Knock Circuity, and Limp Home Mode all in one package. Back in the day ... about 5 years ago, TPI MAF sensors were becoming very expensive. The "Budget" fix was to convert the MAF TPI to a MAP TPI. V6 cars used the same '7730 ECM as the V8 TPI cars, so the price for used '7730 ECM were modest. Back in the day, getting new V8 TPI MAP memcals from GM was about $60. Well fast forward to now, and new V8 TPI are not available from GM, and the "Budget" fix a few years ago is not the "Budget" fix anymore.:mad: Finding a good price for a V8 TPI memcal is anybody guess. V8 TPI memcals can be found on eBay, and I seen some sell for more than $200.:confused: There are ways to convert the V6 MPFI memcal to run the V8, but I think the Knock Circuity, and Limp Home Mode will be incorrect.

The new "Budget" fix for a TPI is the modified '427 PCM.:wink1: eBay and local auto recyclers sell V8 '427 PCM's for about $50 sometimes less. A few mods with a soldering iron, and new options and features for a TPI are available that the older '7730 never had.:D

I personally like TTS DataMaster data logging $oftware. TunerPro RT has data logging software / freeware.

dave w
 
so there is there a Memcal out of another car that would work? something I could find at salvage or is this a custom deal? Sorry for the stupid ?? And Dave, if there is no memcal I could just "grab" do you have a simplified pin out guide that would relate more directly to my 747->427. I'm pretty good at understanding wiring diagrams, But I get confused with your notes. What would a 427 be found in? would tunerpro's freeware work well enough to log what you would need for a chip?
 
I'll be heading to the salvage yard this weekend to get another truck harness (to modify) the pcm. All other necessary harnesses, pigtails, fuel lines, relays etc.... I'll be adding electric fans at the same time, I can pin these in to the pcm to work on their own right?

Edit: this is working out perfect. I bought a 91 G30 box van for the engine (which tpi will be going on) that has 5,000 on the motor. It also has a 4l80e, and I just took a look to see that it has the 427 PCM in it! woo hoo! Not bad for a $200 truck.
 
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The first thing to make sure of with the '427 upgrade is the Vehicle Speed Sensor (VSS). I've only done one '427 conversion, 1987 C3500 / 454 TBI / TH400. The VSS from the 1987 C3500 is working correctly, when wired like my notes. If I remember correctly, the vehicle the 350 is going into has a factory VSS? If your going to use the 4L80E then the Digital Ratio Adapter Converter (DRAC) will need to be used and calibrated.

I'll clean up my notes on the '427 conversion, and post back in a few days. I get my wring diagrams from my local public library ... maybe the library near by can help out with wiring diagrams?

dave w
 
I won't be using the 4l80e in this application. I 'll be using the 700R4 with a np241 case which does have a vss. So I shouldn't need the DRAC?
 
NEWENGLANDK5 said:
I 'll be using the 700R4 with a np241 case which does have a vss. So I shouldn't need the DRAC?
Click to expand...

I think all that is required for 91 Blazer '427 conversion is to wire the VSS like the notes show. Vehicle Speed Signal the wire from ECM '7747 pin A10, will be installed into PCM '427 pin F13.

dave w
 
One of the internal mods to the '427 is to remove the stock resistors and install jumper wires.

dave w


clip_image002.jpg
 
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