Front mount and duty cycle

[timloomis]

I logged the talon yesterday and it showed my 550s were above 80% from 4000rpm on.So I did a boost leak test,found one,fixed it,etc..Logged it again today and they maxed out at 105%.I cant see the 14b maxing out 550s like that,unless my stock sidemount is really gettting hot.Can a heatsoaked sidemount cause idc's to shoot up 15-20% like that,or do I have another leak I havent found yet?And my knock was no more than 4 during the run,o2 was at .87 the whole time.The idc's were 80% and kept climbing from 4000 on.

 

[CanadianTSi]

How much boost are you running?

I suspect another leak.

 

[timloomis]

18 psi.Could my blitz bov be blowing open?Its rated for 18psi,but it surges to 20 when it first spools.

 

[2gAWDTalon]

What did you pressure test the system to?

 

[timloomis]

My tank was kinda low,but I know it was between 10-20.I ran back to see the gauge just as it was falling.What else can cause high idc's like that?

 

[Steve93Talon]

It could be your fuel pump not being able to keep up with the flow requirements of the engine. What pump do you have? Is it rewired? Replaced your fuel filter lately? Did you use a clean fuel sock with you put the pump in?

As for the BOV, is it vented or recirculated? If it's vented, it could cause the MAF to see more airflow if its leaking.

 

[timloomis]

Im using a 3000gt vr-4 pump(180lph),not rewired yet.Its used so that could be it.My bov is vented,but Im using the maft.I was wondering about the pump,as far as how I could tell it wasnt keeping up.I mean my old 450's saw 92% at 16psi.I was also wondering if the bov could blow open when it spikes to 20psi right when I get on it.The spring in it can only hold 18.

 

[Dream On]

I'd say keep looking for boost leaks. I'm seeing about 100% duty cycle on my car with 450's, 14b, and 12 psi. I have a leak at the compressor housing and possibly at the boost gauge.

 

[2gAWDTalon]

My tank was kinda low,but I know it was between 10-20.I ran back to see the gauge just as it was falling.What else can cause high idc's like that?

You need to test the system to at least 20 psi.
If it was falling fast as you ran around to check the gauge you still have a big leak. The system should be able to hold pressure for a few seconds at least.

 

[timloomis]

Yea I should have re-tested it.It was getting dark so I didnt get a chance.But I found the pcv was leaking so I eliminated that,and ran a line into the air intake from the valve cover.Smoke under boost looks like it stopped with that.From reading up on this,wouldnt the o2 voltage show me running rich with a boost leak?Because my o2 shows .87 all the way.When I ran the test,I could hear the pcv leaking,but nothing else.I would think a another big hole would show up too.

 

[donmagicjuan]

Just to clarify, there isn't a way for insufficient fuel flow to affect your injector IDCs. As long as you're talking about WOT runs, injector pulse widths are determined from the fuel maps, which are unaffected by fuel flow.

Inflated IDCs are usually caused by leaks downstream of your airflow sensor. Because you have a GM MAF in a blow-through configuration, you can narrow your search to things between it and the cylinders. You are correct that boost leaks typically result in unusually rich AFRs, but I would be skeptical about trusting your narrowband voltages to reveal this to you. If you still can't find any leaks after pressing the system up to ~20 psi, let us know and we can brainstorm from there.

Good luck.

 

[timloomis]

Thanx man.Ill lean it out a few clicks before driving to work tomorrow to see if it is running rich.Ill of course keep an eye on knock.Its weird though,the torque hit from the turbo feels fine,its just after that.Just after 4000rpm the duty cycle shoots up.It goes up pretty steep,then gradually goes up after 4k.It hits ~80% right around 4k too.Before that its fine.
I dont think its a manifold gasket or anything,since my vacuum is ok.Hopefully its a coupler or something simple.

 

[abillabong2002]

At what RPM does your turbo spool up to. During this spike, your car is reading alot more air, and your injectors are trying to compensate for this, causing them to have to push alot more fuel, therefore causing your IDC % to raise

 

[2gAWDTalon]

Yea I should have re-tested it.It was getting dark so I didnt get a chance.But I found the pcv was leaking so I eliminated that,and ran a line into the air intake from the valve cover.Smoke under boost looks like it stopped with that.From reading up on this,wouldnt the o2 voltage show me running rich with a boost leak?Because my o2 shows .87 all the way.When I ran the test,I could hear the pcv leaking,but nothing else.I would think a another big hole would show up too.

A boost leak is going to take the path of least resistence... so if you have a big leak, the others that are smaller will not show up untill you fix the big leak. When I have a leak, I fix it and then retest and almost always find another leak. I repeat this process however many times it take until I test and there is NO leaks.

Just to clarify, there isn't a way for insufficient fuel flow to affect your injector IDCs. As long as you're talking about WOT runs, injector pulse widths are determined from the fuel maps, which are unaffected by fuel flow.

Inflated IDCs are usually caused by leaks downstream of your airflow sensor. Because you have a GM MAF in a blow-through configuration, you can narrow your search to things between it and the cylinders. You are correct that boost leaks typically result in unusually rich AFRs, but I would be skeptical about trusting your narrowband voltages to reveal this to you. If you still can't find any leaks after pressing the system up to ~20 psi, let us know and we can brainstorm from there.

Good luck.

You are correct in regards to the GM MAS, however I would like to put this out there for future searchers... Just because you have a GM MAS up stream in blow through mode doesn't mean you don't need to worry about boost leaks prior to the MAS. If you have a boost leak before the MAS it should not have a ill effect on you IDC's but the car will not preform as well because the turbo is working harder (against the leak) to make the same boost and maybe putting it out of its efficiency range (hotter air). This will make you lose performance and is harder on your turbo.

 

[timloomis]

20psi,no leaks after the mas.But the blitz bov was leaking at 15-16 psi,not the 18psi it supposed to max out at.I just turned the boost down untill I get the fmic and tial knockoff on.

 

[donmagicjuan]

You are correct in regards to the GM MAS, however I would like to put this out there for future searchers... Just because you have a GM MAS up stream in blow through mode doesn't mean you don't need to worry about boost leaks prior to the MAS. If you have a boost leak before the MAS it should not have a ill effect on you IDC's but the car will not preform as well because the turbo is working harder (against the leak) to make the same boost and maybe putting it out of its efficiency range (hotter air). This will make you lose performance and is harder on your turbo.

Of course. My advice was targeted at the OP's desire to isolate the source of his abnormally high IDCs, nothing more.

 

[timloomis]

What else can cause high idc's like that?I know the obvious high airflow/too small of an injector one,but what else.I was reading up on maft problems,maybe my calibration is screwed up or something.Since Im not maxing out the 550's,no knock,not running lean or rich,and no boost leaks.Any specific thing I should log to see if my maft is measuring airflow correctly?I swear Im about ready to sell the maft and get a safc/get my eprom socketed.

 

[donmagicjuan]

Depending on how much stock you're willing to put into your narrowband O2 voltage, I would say the signs are all telling you that you are indeed reaching the limit of your injectors. Granted, your current setup shouldn't be maxing out the 550s, but an out-of-cal MAF unit and/or bad tune would manifest itself through inappropriate AFRs, which you're apparently not seeing.

Before going any further, however, I'd like to get some more information regarding what you've done so far:

1) How is your MAF-T currently adjusted (i.e. what settings have you dialed in)? Specifically, how do the settings differ from when you were running with stock injectors?

2) Are you 100% sure that your current injectors are rated for 550 cc/min?

3) When performing the boost leak test at 20 psi, did you observe pressure in the system for 30 seconds (not leaking down to less than ~10 psi) with the source removed?

4) Does your EPROM ECU have any custom fuel mapping?

5) Are you still using the stock fuel pressure regulator?

I'm hoping that your answers to these will reveal something that we've somehow overlooked to this point. It's worth noting that while fuel supply issues (e.g. insufficient flow) won't directly affect your injector pulse widths as I mentioned earlier, it is possible to get higher IDCs as a result if you try to alter your tune to compensate for such a problem. I was assuming earlier that you were reporting the problem as emerging with no adjustments to the MAF-T.

 

[timloomis]

Im still on the stock fpr,I'm getting about 2-3 psi more because of my fuel pump(I think).My injectors say 550 right on the side of them,theyre rc's also.My eprom hasnt been socketed yet so its still on stock maps.Boost leak test was fine.I turned the boost down to 15-16psi,and my duty cycle is still 92% with knock maxing at around 8.Ill check my maft settings and have a look at the gm mas to see if anything obvious is wrong with it.The screen might be out of it,I cant remember.Would that make a difference?I have a spare gm mas that I can swap in to check if this one is bad.

Edit:just checked the maft settings.I have it set for 570's,that makes my o2 trim around 100% while cruising.

 

[timloomis]

I bypassed the fpr solenoid and changed the fpr with a n/t one, and dropped 20% on the idc's. Plus the maft was WAY off because of the bad fpr and solenoid. So far so good. I logged up to 5200 rpm or so today, no knock and idc's in the mid 70's.

 

[donmagicjuan]

Are you sure you haven't just stumbled on a band-aid fix for this? Base fuel pressure for a 1G N/T is about 8-10 psi higher than a turbo's, so I would expect a drop in IDCs after re-tuning with the MAF-T, even if you were replacing a perfectly healthy FPR. 70+% by 5000 RPM still seems a little on the high side for 550s at 18 psi with an extra boost in fuel pressure, but at least you're not burnin' 'em up anymore. What AFR (or O2 voltages) were you seeing on those runs?

 

[timloomis]

I turned the boost down to 15 psi for now. But I guess that bump in fuel pressure made my 550's into 640's or so. I went ahead and adjusted the maft for it too. I logged it again, and it was around 68-69% idc. My o2 was at .89 volts after 2 more clicks rich on the wot knob (10%). The car pulls a lot better now, Im sure it's just the stock sidemount holding me back now. Knock is gone too.

 

[timloomis]

Problem is back. Idc almost at 100% at 20psi on the frontmount and the "640cc" injectors.
I bought a new fuel filter that I'll install in the next day or two to see if that helps, it just has to be fuel related now. Car hauls major ass now, I compare it to hitting nitrous. It's a major difference with that fmic.

 

[Dream On]

For the above post...

Just to clarify, there isn't a way for insufficient fuel flow to affect your injector IDCs.

 

[donmagicjuan]

Well, it sounds like you're experiencing a boost leak that is showing up right before 20 psi. If you go from high 60s to 100% duty cycle when changing the boost only a few pounds, there is little else it could be. The only other thing that comes to mind is a departure from linearity in the MAF output signal. On my GM unit, I've had to really monkey with the tune to get the right AFRs. I've also done a satisfactory leak test, and I'm adding as much as 40% fuel under cruising conditions and taking out as much as 25% at WOT, all after globally scaling the injector size in ECU+ for my 650s. The only thing to which I've been able to attribute this behavior is the difference in response between the two air sensors. However, I'm not sure whether I subscribe to this theory in light of the overwhelming success others have had with nothing more than a MAF-T.

If you are confident that you don't have a major boost leak anywhere at your operating boost level, I suppose it's possible that your MAF-T isn't cutting it. If you have the means, you might try swapping out the MAF sensor itself as well as the MAF-T with known working units, just to rule them out as potential culprits.