How much boost is too much, and diff lock Q's (5kTQ)

[John Forbes]

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After completing the EFI setup on my car (going on a month and a half now) =
and getting the boost knob in, I've been slightly unsure how much is too mu=
ch. I've mostly been running at about 2.2bar (absolute of course), but ocas=
ionally have set it as high as 2.5 for some short runs. I always run 93 oct=
ane fuel, and when I plan on going fast for a while I top it off on 100 oct=
ane. I've noticed no knock, so I feel pretty much safe there. What I'm afra=
id of is piston rings and over revving the turbo. I remember a little while=
 ago a lister posted about the turbo on his car giving out at arround 2.7ba=
r after a wastegate diaphram failure (and with overboost limit set a bit hi=
gh). Also I wonder about damaging the factory pressure sensor inside the EC=
U at high boost levels like this (since the digital boost readout stops at =
1=2E9bar). Oh and yes of course I have an aftermarket boost gauge installed.

For those of you who haven't yet realised the glory of EFI, boy I'll tell y=
ou it makes a huge differance. Not only does the car now sound great on boo=
st with just a K&N filter stuck at the end of the pipe that used to go from=
 CIS airflow plate to the turbo intake, but deleting the CIS alone made a h=
uge performance differance. Also fun is my digital dash, which now says I a=
m getting 200.0mpg, and have 2000 miles to go until I need a fill-up ;-p.

Note for you DIY'ers, my entire conversion cost me a grand total of about $=
200, which I could probably make back by selling the old CIS junk (any buye=
rs? everything is in great condition, heh). ECU was most expensive part at =
$130, fuel rail made for another $15, then fuel pressure regulators were an=
other $15, electrical wire and fuel hose makes up the rest of the cost. I d=
id get the injectors for free with helped, but they could have been junkyar=
d picked for next to nothing.


My second round of questions involves the diff locks. With my crappy tires =
I now have severe traction problems in the front if I launch the car hard. =
I am wondering how safe it would be to turn on both diff locks (or even jus=
t the center) when I go to the strip. I accidentally murdered the vacuum co=
ntrol for the center diff locker last time I did the clutch, and the rear v=
acuum control hasn't worked since I got the car, so I would just set them o=
n manually before the run and turn them off manually right after (meaning t=
hey wouldn't automatically turn of at 45(?)mph or whatever the speed is tha=
t turns them off). I also noticed today when it started downpouring that I =
am breaking the front tires loose when the car comes on boost in the first =
2 gears, even in 3rd on the right roads. Would it be OK to turn on the cent=
er diff lock for when its raining. I plan on changing them to electric sole=
noid control when I get the chance, but I have other projects (like the mou=
ld for the fiberglass hood with venting louvers!) to finish first.

Check out www.craincorporated.com/q for the most recent updates on the car.=
 I try to keep the site up to date, but sometimes I'm out having too much f=
un with the car so I miss a fews days (or weeks).


Cody Forbes
'87 5KTQ - EFI done, now making header (which also involves adding the T3/T=
04E hybrid turbo)
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