THis is good stuff - found it in a vette magazine in '01.

Note the reference to intake flow being based on the LB9 305 TPI intake flow. The author knows his stuff (never mind my highlights - I DON'T make any claim to know his stuff).

Print it out, and put it in the 'Library', where the seat has a BIG hole in the middle.

Some parts you might not understand. Re-read over and over, and it will all come to you - guaranteed.

 

page 4, 5...

edit:
Note page 4, column 3, top, Ray does not say that you HAVE TO HAVE A STEADY RPM FIRST, when doing vac leak detection!!!

As noted in my post here, that is CRITICAL!!!

 

and pages 6, 7...

 

+1

 

Once you get past all the errors

That would be obvious

 

Nice info. Thanks!

 

Great article.

 

Like I said
once you get past the simple errors like the statement that your fuel pump will turn off if you have low oil pressure to save your engine

 

Don't tell us on the boards here that he's wrong. Tell the author that he's wrong.

Then get him to post here that he's wrong.




ed,:
Here's his web page:
http://www.raytbohacz.com/

Most links on his page defer to HEMMING'S web servers.

Looks like Hemmings stands behind him. But Hemming's doesn't know cars either ... do they?

 

Don't need to .

You are the one presenting it to this forum as the holy grail of TPI info and taking as gospel a 3rd parties information which is erroneous and misleading.
People who own a TPI /TBI engine ( do you ?) know better .

In this case ,all it is doing is perpetuating a long held myth held by newbies and the ignorant that the OP switch will save their engine.

PS.
Loving the "us" from the man who has been here a week

 

oz if you waiting for someone to ask you where the article went wrong ok I'm asking.

Otherwise the drama.....

 

Idk, my 89 tpi has fuel pump relay tied into the oil pressure switch/sender. I always thought if it didnt have pressure it wouldnt trigger the relay

 

OP switch triggers the relay to run the pump so that when engine stalls, pump will quit.

 

The myth I was talking about


Think again
the ECM runs the pump relay .KO and anytime the ECM is receiving a ref signal from the dist to indicate engine is turning over.
OP switch closes @ 4 psi to run the pump direct from the battery.
If you can read a circuit diagram you will see each is mutually exclusive.if the OP drops and the OP switch opens the pump will still receive power
from the relay.
(The OP switch is in place as a backup ,so that if you loose the pump relay you can still start the engine (albeit with extended cranking )
with the pump powered from the OP switch)

3rd Gen wiring.




Easier to read Vette pump diagram

 

FWIW.

There are a multitude of ancient tech articles from the same time frame as this one where a established tech writer has made fundamental errors
when transitioning from their carb experience to EFI.

In this case the only experience the writer probably had with a oil pressure operated fuel pump switch would have been as a safety cutout on a carb car.

Just a shame the OP choose to highlight that comment so it sticks out like a proverbial

 

the interesting part is how similar the TPI model is to the newer LS1 computers. and.. for that matter.. how similar the TPI way of doing things is to the LS1 generation. all the LSx did was take both the MAP and MAF models above and turned them into a hybrid and nicely redundant system.

Model a buddy figured out:
CAM1 (Cylinder Airmass Model)= 20*(A*MAFhz^3+B*MAFhz^2+C*MAFhz+D)/(CYL*RPM)
CAM2= IPW*IFR*AFRwb
CAM3= GMVE*MAP/TEMP (GMVE is just a GM term for a general physics term.. ill find it later)
GMVE= CYLVOL*VE/R
TEMP= IAT+(ECT-IAT)*BIAS

seems like in the early EFI days, gm used CAM2 and 3 or CAM1 and 2 depending on the year/model then later went to the 3 airmass model. neat.

 

So, is that the only error you're complaining about? If so, that's pretty trivial and you're doing a disservice to people by suggesting everything in the article is questionable. Strikes me as a lot of great info in here. I'm saving a copy.

 

I also see many glaring errors. Such as stock fuel pressure often varied widely. The stock 350 injectors were 22 lb/hr, not 24. Along with numerous other errors along the way. I also love how they claim a stock 305 does not respond to a runner upgrade, they most certainly DO.

 

You're doing the same thing VetteOz did - making vague accusations of many glaring errors but only mentioning a couple of not so glaring errors. I know the stock 350 injectors were 22lb /hour but I'm pretty skeptical that fuel pressure "often varied widely". Instead of making blanket unsupported assertions, how about mentioning only specific examples so readers like me know what to (perhaps) believe?

 

good post..