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Discussion Starter #1
I just replaced my stock turbo with a T3/T4 stage 2 and my question is the compressor on the new turbo did not have a hole for the APC solenoid so I connected the hose from the "C" on the solenoid to the inlet tube (from the intercooler to the throttle body) is that location OK?
Also do all the hoses on the solenoid have to be connected?
Thanks
 

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Yes you must have them connected properly for your APC to control your boost and fueling with minimum knock. The compressor APC solenoid hose measures boost, whilst the inlet hose measures ambient pressures. Must have both signals for the APC to determine boost levels and proper WG function.

pierre
 

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idiot_saabvant said:
Yes you must have them connected properly for your APC to control your boost and fueling with minimum knock. The compressor APC solenoid hose measures boost, whilst the inlet hose measures ambient pressures. Must have both signals for the APC to determine boost levels and proper WG function.

pierre
Not quite right. Agreed they all must be hooked up, but the boost measurement comes from a pressure transducer, telling the apc info. The apc in turn tells or sends a pulse width modulation signal to the solenoid redirecting the compressed air to the wastegate thus opening up the swing gate and lowering/ limiting the boost. If your compressor does not have a nipple you can add one a couples way. Drill and tap the housing, or ATP sells a tap where you punch a hole in an outlet hose coupler. The first suggestion is better, but takes a bit more work. Kinda always works that way.
Wmac after rereading your question I think that would work. There is a bit of pressure drop after the intercooler, but it still should open the wastegate. The word inlet might be a bit confusing. I/C to the throttle body is an okay place to tap for "C". Air filter to the turbo no good.
 

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wmac said:
So I need to drill and tap the compressor housing?
That is convention. Are you able to get a boost pressure to supply "c" input on the solenoid and are you getting boost control? If so, you are already setup.
 

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Discussion Starter #9
Squaab99t said:
That is convention. Are you able to get a boost pressure to supply "c" input on the solenoid and are you getting boost control? If so, you are already setup.
My problem seems to be that I don't get full boost, if under a load it will boost 3/4 into the red, if I start above 2500 rpm then it never gets into the red.
 

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Sounds to me like you have hooked your APC up the wron way, or you get knock... Installation of a knock-led will definetly be a great idea...
Daniel
 

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just to confirm ...

speaking of unmodified APC stup ... max boost is set at ~0,85 bar meaning that under normal conditions (ignition timing, fuel pressure, fuel rating) there should be no knock occuring?

It`s not like the turbo pressure is allowed to build untill the knock.
So, at corect settings I should not see any knock ...

Currently I`m getting my saab boost turbo gauge just uptill the yelow/red broder and my aftermarket gauge reading ~ 0,7 bar. Don`t know if ther`s any knock ever.

Time for my knock light to be hoked up.
I red that knock signal from APC would not power up those standard bulbs as in the instument cluster (SRS, ABS etc.). Is that correct and only diode will work?
Thank`s!
 

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Saab-Daniel said:
Sounds to me like you have hooked your APC up the wron way, or you get knock... Installation of a knock-led will definetly be a great idea...
Daniel
Or the wastegate actuator spring is getting tired
 

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Redbaron, true, but this is with a new turbo...
wmac, have you checked baseboost (disconnecting the plug on top of the solenoid and go driving up a slope in third, flooring it, and keep going to high revs)? It should be around 0.5 bar
Have you altered your APC? If not, you should only see 0.75 bar of boost, never higher! So that goes for you as well, Kurbads... Knock will cause the boost to drop to the set baseboost, given that the APC works as it should!
Daniel.
 

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Discussion Starter #15
Saab-Daniel said:
Redbaron, true, but this is with a new turbo...
wmac, have you checked baseboost (disconnecting the plug on top of the solenoid and go driving up a slope in third, flooring it, and keep going to high revs)? It should be around 0.5 bar
Have you altered your APC? If not, you should only see 0.75 bar of boost, never higher! So that goes for you as well, Kurbads... Knock will cause the boost to drop to the set baseboost, given that the APC works as it should!
Daniel.
Well now it looks like everything is somewhat back to normal except that in all gears boost does not stay in the orange after about 4200, 4300 rpm, it drops into the yellow. Sorry I do not have a boost guage yet.
 

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I think you get knock, and APC pulls boost. Get a calibrated boost-gauge and a knock-led fitted, it will provide you with so much info... :)
Other than that, how far into orange does it go?
AND, did you mess with the apc-ECU?
Daniel.
 

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wmac said:
Well now it looks like everything is somewhat back to normal except that in all gears boost does not stay in the orange after about 4200, 4300 rpm, it drops into the yellow. Sorry I do not have a boost guage yet.
You did install an up rated turbo (T3/T4). I think you might be going lean and the APC is doing its job. Did you revise the fueling? Larger injectors, higher fuel pressure, or ECU changes? A wideband lambda would be the only true way to tell. A datalog is very helpful if you are the only one in the car. Even with an observer it is tough to see the data via the gauges only.
 

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Discussion Starter #18
Squaab99t said:
You did install an up rated turbo (T3/T4). I think you might be going lean and the APC is doing its job. Did you revise the fueling? Larger injectors, higher fuel pressure, or ECU changes? A wideband lambda would be the only true way to tell. A datalog is very helpful if you are the only one in the car. Even with an observer it is tough to see the data via the gauges only.
I do have the 3.0 bar fpr and 30# injectors, but I do not think the apc is modified.
 

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wmac said:
I do have the 3.0 bar fpr and 30# injectors, but I do not think the apc is modified.
Without wide band, or even knock data you can't make an informed decision. Wide band is what you need. Knock is the last ditch being too late and not a measurement of how severe. With the stock ECU, 3 bar and 30#s I'm guessing it runs like a rich pig at idle up to 3k? You can fiddle with the apc, but make sure the fueling is correct at that type of engine load. Another way to give you an idea of your AFR is to read your plugs. Drive around normally maybe base boost a bit, idle and then pull your plugs. If they are black sooty looking, too rich. Now go for a hot lap high boost and RPMs. Shut it down quick (no idle) pull a plug see what you got. Get the engine idling again quickly so you don't coke that brand new turbo. These are all the things your fellow Saab modder and I went thru. The ultimate fix is at the ECU fuel map. This means a revised chip or standalone ECU, Megasquart...
 

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my turbo did not have the correct tap either, and i figured the best spot for it was as close to the original location as possible.

IronJoe beat me to posting the pic, by a few days ;)

seems to work well for me. i figure that so long as 5 of the 6 bolts holding the intake housing on are tight, all should seal well.
 
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