Okay so recently my 91 N/A was totalled off (not my fault) and I now am the owner of a 87 N/A with a Tii swap. First off should my boost gauge read 5.5psi or 5? It's an S4 with an S5 turbo. It reads 5 and I was wondering if that's normal . Also on cold start ups the idle seems a bit shaky. The car does have the emissions stuff removed and runs extremely rich. Any tips on how to lean it out? I'm pretty sure my timing is good. Also again on cold start ups my exhaust seems to pulsate, is this normal? or partially because of the idle.. which fluctuates about 100rpm..maybe. I can feel it with my hand kinda like mini pulses. Once it's warm it seems to settle down. Thanks for any help.

 

is there a bigger downpipe or intake on it? or all stock? if stock that sounds about right.

what does the vacuum read on the vacuum/boost gauge at idle when warm?

also, checking the plugs on a newly purchased car is a must.

 

It does have a cold air intake..not really just a garbage filter on then end probably sucking hot air. If I remember correctly my vacuum is around 15..could be wrong though...will check again today.

 

the idle sucks when it's cold probably because the guy removed the cold idle system (thermowax/fast idle cam)

 

The stock wastegate spring is a 5.5psi spring, but you can see 5-6 psi normally. You'll probably see if fluctuate a little. More so if it has an open exhaust to go with the open intake (boost creep).

And as arghx said, poor cold start may be due to removal the the thermowax and/or the BAC.

Sounds like your next project should be a box or divider for the intake. Or just put the stock one on it. It's not much of a restriction if you're only running stock boost, and it's better than a hot air intake.

 

Thanks for the info. guys...i was just curious about the cold idle...you seem to know what it is. I'm definitely going to make a little plate for my intake. My boost stays steady at 5psi on the gauge and 15 for vacuum. I do know that I need a new alternator..but my dash lights have been cutting in and out..could this be cause of the alternator? I don't see why but friend had an explorer and his did the same thing when his alternator went.

 

All of the warning lights will light up if the voltage regulator in the alternator is bad, or if the voltage just drops too low for any reason. Grab a multimeter and measure voltage at the battery & at the alternator post while the car idles. Ideally, you'll have around 14.4 volts.

 

what happen when it runs rich?
would it damage you engine like when your running lean?
or nothing?

 

We are talking rotary here, rich is almost always better than lean. Especially in boost...
Do you guys have a Wideband?

I don't believe its possible to damage your engine running rich like you would if you were running lean...

 

thanks for the reply, I just did a full rb exhaust for a s5 t2, fcd, ported turbo and I got a fuel pump, I was hoping that would put the engine to the rich side.

 

You can run rich as long as you dont hit into the 9's afr. 10.5-11.5 is about right, it depends on what your using for tuning. When your using something sloppy like the "gameboy tune" then id run conservative (closer to 10.5) otherwise if your using a standalone and know what your doing id say 11.0-11.3

+1 ^^


As for the "mini pulses" id check compression first.