Very slow spool up

[TSIkw]

I installed an EVOIII 16G, front mount, and GM Maf and translator running a blowthrough setup. I've calibrated the MAFT too.

The problem is the turbo will spool up to 10psi by around 3000rpm's and it stops there. Then around 4500rpm it will slowly start to build more pressure. It takes all the way to around 6000rpm to get it up to 16psi where is have it set.

I've done multiple boost leak tests and can't find any leaks. Even sprayed soapy water all over and I don't see any bubbles.

Any thoughts on how to fix this or what else to look for? I'm lost.

My Setup:
EvoIII 16G
FMIC
3" GM MAF and Translator
Denso 660's
DSM Link

 

[oldman]

I am venting at 1g BOV.

I'll hook it back up for recirculation tomorrow and see if it helps.

Correction, it your maft is setup in blow through mode, the open 1G BOV will not introduce unmetered air at idle.

At this point, you should be focusing on the following tasks in the following order.

1. Figure out why you're only pulling -14 inHG of vacuum at idle, this can be bad gauge, vacuum leaks, or timing.

2. Calibrate your MAFT, if this means forking out more money for a GAM 3bar sensor, so be it, such as the price to pay to properly run a MAFT setup.

3. Re-tune your global and deadtime as instructed using LTFT low and hi.

 

[TSIkw]

my base timing is good and my gauge seems to be functioning fine. When it is idling around 800rpm's it is pulling -15 inHG...if i rev it slightly to just over 1000rpm's and hold it there it will pull -18 inHG.

I checked over all my vacuum lines today and sprayed the potential problem areas with some carb cleaner to see if the RPM's would change but nothing happened.

 

[TSIkw]

What about the vacuum lines that are on top of the TB. I switched two of those wires around today because I noticed they were on wrong based on the color codes in a diagram. Switching those around helped my vacuum because it was pulling -13 in HG when they were on wrong and -15 inHG when I switched them.

I know alot of people just block those lines off...is this a smart thing to do?

 

[TSIkw]

In my efforts to research vacuum line removal and ways to find vacuum leaks i can across lots of threads on the pcv system.

This is a write up from another wiseman....
PCV 101: At idle, the IM is under vaccuum and the PCV valve (threaded into back-left of VC) opens up. The VC breather (side of VC) provides an inlet to the VC and crankcase (crankcase is connected to top of head by oil return passages). So at idle, air (which has been metered by the MAS if stock MAS is still used) is pulled through the VC breather into the VC/crankcase, and it flushes the fumes out which are pulled out the PCV valve into the IM and through the motor (burned). The PCV also flows differently at varying vaccuum conditions. The car is tuned to this and will not idle properly if the PCV is just replaced with a check valve.

Under boost, the PCV closes (it's a one-way valve). If it didn't, the boost in the IM would go into your VC and crankcase. That part of the motor isn't supposed to be pressurized. To relieve the pressure, the VC breather is needed again, but in the boosted case, the VC breather is a vent for the blowby. It gets blown into the intake pipe where it is then pulled through the motor (burned). Since the blowby was metered air, blowing it back into the intake pipe downstream of the MAS helps, but oil fumes can coat the intake pipe, compressor housing, IC, IC pipes, TB, and IM. That's why folks put a filter in their VC breather line.

There are baffles (metal plates) along the top of the valve cover to keep oil from splashing into the VC breather or PCV valve. This keeps the majority of the oil from going out the PCV (at idle) or VC breather (under boost). The PCV valve even has a snorkel on the end to keep the inlet away from the wall of the VC to help reduce the amount of oil it pulls through.

All of this keeps your crankcase from pressurizing too much under boost, and it also keeps fumes from blowby (these are fuel/air mix *and* exhaust fumes) during idle/vaccuum from hanging around and settling in your oil which would decrease its performance.

So think it through before you remove your PCV, VC breather hose, etc. This is a PCV system, and all of those functions have a purpose. There are many threads on ways to keep oil out of your intake, help with the short-lived OEM PCV valves, etc. that still preserve the PCV system functionality. Might want to check them out if for no other reason than to understand what this system does and what alternatives are good vs. bad ideas.
[End Quote]

The first paragraph which I've bolded got me thinking. I have the breather line off of the valve cover just put into a soda can to catch the oil. I don't have a filter on it or anything.

If that breather line at idle is sucking air into the system then it is going in as unmetered air with the breather hose hanging.

First question is...can that be the cause of my car running so lean at idle?

Second question is...if that does cause a lean condition at idle how can it be hooked up to eliminate that? If the breather hose is tapped into the UICP after the GM Maf it will just blow oil into the IC pipe and through the TB.

 

[oldman]

The first paragraph which I've bolded got me thinking. I have the breather line off of the valve cover just put into a soda can to catch the oil. I don't have a filter on it or anything.

If that breather line at idle is sucking air into the system then it is going in as unmetered air with the breather hose hanging.

First question is...can that be the cause of my car running so lean at idle?

Second question is...if that does cause a lean condition at idle how can it be hooked up to eliminate that? If the breather hose is tapped into the UICP after the GM Maf it will just blow oil into the IC pipe and through the TB.

I have already told you this in one of my previous posts.

Vacuum only exit between your throttle plate and your intake valves, nothing to do with the type of maf you're using. Possible places for vacuum leaks are, going from TB to head, BISS o-ring, TB shaft seals, TB inner gasket, BOV line, brake booster line/check valve, FPR line/boost gauge, IM gasket, intake valve seals. PCV valve will also introduce unmetered air since you're running GM maf even if your breather is re-routed back to the intake pipe like you're suppose to. Lastly, have you calibrated your maft using either WB O2 sensor or MAP sensor?

There is no fix for you on this because you're running maft, tapping into the UICP after the sensor will result in pressurizing the crankcase when you're under boot. Your breather line shouldn't just be connected to a catch can that is vented, connect it back to the intake pipe with an inline Husky catch can so you can take advantage of the vacuum in the intake pipe during boosting to help ventilate the crankcase.

As for running lean at idle, there are ways to fix this via DSMLink but I didn't want to tell you because I really want you to find out the cause of your -15 inHG issue and fix the mechanical problem first. I will show you now.

1. What is your global/deadtime?

2. What are your LTFT lo and hi?

 

[TSIkw]

I can't hook the breather hose to the intake pipe as is cause I have a dejon intake pipe. I could tap another nipple into that if it will help.

I know you can make adjustments in DSM Link but I wanted to fix the problem not tune around it.

Injectors are Denso 660's
Global= -31
Deadtime = 180

LTFT LO = +10, out of range for the ecu to compensate
LTFT Hi = -2

Aside from my fuel setting I've been using the Airflow sliders to try and get the Lo and Hi fuel trims in check. Right now I have to have the 50hz airflow slider at +60 and and my Lo trim is still at +10. If I have it lower I can't get the Front O2 to cycle.

 

[oldman]

I can't hook the breather hose to the intake pipe as is cause I have a dejon intake pipe. I could tap another nipple into that if it will help.

That is exactly what everyone does, myself included.

I know you can make adjustments in DSM Link but I wanted to fix the problem not tune around it.

And I'm all for that, the answers to your question lies in finding out why you're pulling low vacuum as well as proper maft calibration, I mentioned tuning around it because you don't seem to grasp that concept. Yes, you're pulling some unmetered air through your PCV valve due to your maft setup but it should not make the kind of difference that are reflected by your LTFT lo and with the amount of adjustments already made on the maf sliders.

 

[TSIkw]

Yeah I am having a tough time grasping all this. I'm trying to get the vacuum problem figured out but can't find the leak(s).

Is it a good idea to remove the 4 vacuum lines on the TB and block off the nipples? I know alot of people do that. Also if I do that do I have to remove the hoses entirely or can i just unhook them from the TB to see if it helps the vacuum?

 

[oldman]

Is it a good idea to remove the 4 vacuum lines on the TB and block off the nipples? I know alot of people do that. Also if I do that do I have to remove the hoses entirely or can i just unhook them from the TB to see if it helps the vacuum?

You can't just leave them open because they will become boost and vacuum leaks. I'm not familiar with the 91'+ TB's but I believe you can loop the 2 outside ones and 2 inside ones together.

 

[TSIkw]

I wasn't going to leave the nipples on the TB open...i'm thinking of getting caps for those to seal them up. I was questioning the other ends of the vacuum lines that go to the egr and charcoal canister.

I think I have to install an egr block off plate if i do that though.

 

[oldman]

I think I have to install an egr block off plate if i do that though.

That is correct, you can leave the canister line open.

 

[TSIkw]

I'm going to replace all the vacuum lines first. If that doesn't help I am going to block off the egr and do the removal.

I had a question about the 4 nipples on the back of the IM that go into that bracket. I only have vacuum lines going to the 2 nipples closest to the firewall and the 2 closest to the IM have nothing on them. Is there supposed to be any lines going to those 2? I can't find a diagram that shows what those are supposed to be.

 

[oldman]

That's normal, that's how mine was.

 

[TSIkw]

Another question....is the thing under the battery tray the Purge control valve? Anyway, there is two vacuum lines to it and one large hose that i think was hooked up to stock boost controller. Does the larger hose need to be capped off or hooked to something since I still have all the vacuum lines in place.

 

[oldman]

That hose goes to the intake pipe, you can just leave it vented.

 

[TSIkw]

ok...i replaced all the vacuum lines off of the TB that go to the egr, purge contol valve, bracket on the back of IM, and over to the thermostat housing. BOV line is new and i installed a husky inline filter on the VC breather hose and tapped it to my intake and its still only pulling -15 in HG at idle.

I used the ground timing function in DSM Link to check the timing and it was at 4.9 which i believe is good.

If i just touch the gas a little bit and hold it the vacuum goes to -18 in HG and stays there.

I guess i am down to the IM gasket? Is there a way to check that before i go pulling it apart to relace it?

 

[TSIkw]

Also, could the egr cause the lo vacuum if its not functioning properly?