boost question.

[ronin]

yep, Lawrence. cut-off valve. only thing is though that when the valve goes, the car runs like hell under WOT. as if the ignition were cut and lots of smoke. Buck, exactly what happens under WOT at 35-3700 rpm?

[Lawrence Coppari]

At the track on my car I've had the vacuum line come off that valve. Car ran fine but did not produce boost beyond 1.2-1.3 bars. It did not miss, smoke or anything that I could see in the rear view mirror. I've seen it happen on cars that were stock as well. Same symptoms. Hopefully this is the problem because is it a cheap fix.

[ronin]

Lawrence. according to your prior experiences, then that sounds about right. I'll conclude then that the cut-off valve itself isn't malfunctioning but that it is a vacuum leak in the general area like you said. when my cut-off valve failed, it was quite noticeable. while making a pass and going to WOT, the engine began to hesitate and lose power as if the ignition was being cut. there was also a lot of black smoke probably due to the excess of unburnt fuel. I suppose it would be beneficial to check the manual to see what the effects are of a failed cut-off valve

[Lawrence Coppari]

If your vacuum is not what it should be, your fuel pressure will be off too. The valve is easy to check.

[RichMason]

While all the experts are assembled on one thread...I think I have a boost problem on my 87. The car surges on its way to full boost/full throttle - just as if the car were loosing boost momentarily. The stock dash gauge does go up to 1.8 but the car doesn't make any power under 3500 rpm. I haven't checked the bypass/diverter valve except to notice that the rubber elbow for the vacum line is a loose fit. Also the banjo bolt line to the hard pipe is visibly cracked on the outside (I assume it has an inner hose that is intact). My question though is if I have a vacumn leak, how can I still get full boost, albeit late?

[awilson40]

Originally posted by RichMason
While all the experts are assembled on one thread...I think I have a boost problem on my 87. The car surges on its way to full boost/full throttle - just as if the car were loosing boost momentarily.

For giggles, try disconnecting your O2 sensor and give it a drive. See if the surging goes away. I have never totally eliminated this same issue with mine so I'm running ROW fuel maps which ignore the O2 sensor and the car runs great.
With an A/F gauge I can see the car stays in closed loop as boost is building...thats when the surging occurs. As soon as it drops out of closed loop the car smooths out and away it goes. By running ROW maps the car never goes in closed loop and uses its fuel maps. I plan on pulling the intake over the holidays and replace every hose and leaky device I can find. If that doesnt solve it then heck with it. It runs too good on ROW maps to worry about it.

[Manute]

Very interesting the blink codes,didnīt knew them.
Yes,iīm ignorant,but where is the throttle position sensor located?

[Manute]

Damm! correct me if iīm wrong,but according a picture i took from my fuse box,i donīt have the terminal to test the blink codes.But maybe is not that.

Damm! nothing cheap and easy to test is present in my car!!

[robm-951]

Originally posted by Manute
Damm! correct me if iīm wrong,but according a picture i took from my fuse box,i donīt have the terminal to test the blink codes.But maybe is not that.

[ronin]

Originally posted by RichMason
While all the experts are assembled on one thread...I think I have a boost problem on my 87. The car surges on its way to full boost/full throttle - just as if the car were loosing boost momentarily. The stock dash gauge does go up to 1.8 but the car doesn't make any power under 3500 rpm. I haven't checked the bypass/diverter valve except to notice that the rubber elbow for the vacum line is a loose fit. Also the banjo bolt line to the hard pipe is visibly cracked on the outside (I assume it has an inner hose that is intact). My question though is if I have a vacumn leak, how can I still get full boost, albeit late?

wow Rich, I don't know why I didn't catch this earlier (perhaps I lost touch with the thread) but reading your post now I am forced to ask the question of what you mean when you say "no power." the turbo doesn't kick in until 3500rpm. so what you describe actually sounds normal. that's why I ask what you mean by no power. the car should actually feel comparable to an N/A until 3500 when the turbo comes online

[Manute]

Damm stinkinīRonin, help me too!!!!!!

[ronin]

but Rob already did!! just follow the arrow, you can't miss it. see the hose right at the tip of the arrow? it's a black cap about 4cm (or so) wide on the fenderwell under that hose. just flip up the cap and the plug is in there!

Feliz Navidad, cabronazo! este preparado para PG2!! Voy a visitar a mi hija hoy. Estare detras esta noche.

[Manute]

Oooops! Didīnt saw Rob response! Thank you Rob!!

Feliz Navidad to all!

Yo tambien estoy preparado para PG2....van a correr rios de sangre!!
Que lo pases bien con tu hija amigo Ronin!

[DannoXYZ]

Also the blink-codes are generated by the KLR box, not the DME computer. If you notice the list of codes on my site, they all pretty-much relate to boost-related functions which is what the KLR manages.

Another function that's related is watching the TPS. It uses the TPS position to look up a 3D duty-cycle curve for the CV-cycling valve which manages boost. Kinda like the 3D fuel-maps for the injectors. Depending upon TPS-opening velocity and amount, it will also send a binary on/off full-throttle signal to the DME (which is still expecting to see the 944NA's fully-open/fully-closed contact switches).

So... check out the blink-codes at the test-port. But first, verify that you have the LED hooked up correctly by yanking the TPS with the engine running. It should start spitting out blink codes like crazy!