driveability after IC
Did the intercooler a couple months back and ever since then my part throttle inputs have really suffered.
The first thing I noticed was when approaching 0 vac/boost onset, my wb would read 10:1. The second and I believe related thing is, let's say I'm on the freeway and I punch it in 5th gear, car goes into boost, hits 10 psi and if I gently back off the gas I get a horrible stutter. I end up having to take my foot completely off the pedal to avoid this stuttering. The rich condition is right at 4k rpm, 25-30%tps signal. I have tried unsuccessfully to tune out of it but it makes no difference. I even pulled 40% from my airflow map on the emb right at that cell and it made no difference whatsoever. I have the greddy sensor installed and on that map, I am adding 0 fuel in those cells. I have 305cc injectors installed. Besides this issue, the car runs great. I have really had to change my driving style do to this. I am used to smooth throttle inputs, now it's more or less wot, off, wot, off. Help!:facepalm: |
I highly doubt it has anything with you adding an fmic. Sounds more like a tuning issue and bov setting too stiff.
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Ya think? I was going to try removing the bov vac line and plugging the mani to see if it made any difference.
If I understand this correctly, the bov should be held pretty tightly shut at zero vacuum, why would that cause a 10-1 afr? |
I dunno much about the emb, but on ms there are "overrun fuel cut" settings which cut fuel as soon as you let off the throttle and dip into vacuum. As for the surging, what bov do you have? Is it adjustable?
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Just a cheap ebay one, it has washers for adjustment. I had to cut a lot of the spring to get rid of comp surge already. Come to think of it, I still hear a very slight fluttering when shifting below like 3k. Maybe you're on to something?
Again, why do you think too stiff of a spring would cause me to run rich entering boost? I could see if it was too loose a spring and I was sucking in unmetered air. |
I think the two problems are independent of one another. You're still running the maf? Is the bov recirculated?
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Yes on the maf, I was thinking about that too. I already had issues with that originally because it was to close to the compressor and I was having droopy idle problems. I extended the intake pipe by about a foot and that problem went away completely. Maybe with the compressor spooling up, the maf is still picking up airflow from that and going rich?
The bov is vta right now, which I know is not the best idea on a maf car, but when I had my bpv with a check valve installed I had the same issue. |
Well for one, I wouldn't use the airflow adjustment map. Use the injector map and the timing maps, that's all you really need. The airflow adjustment map will fuck with timing, FYI. Injector map won't. Sounds like you need to spend time tuning.
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I only tried using the airflow map today to lean it out around the problem area. Normally I use just the injector and ignition maps with the greddy sensor.
It was weird because regardless of how much I attempted to remove fuel with the airflow map, I still saw 10.1 on my wideband at between 25-30%throttle at 4k. |
There's a possibility of your bov to be partially open in that range, or at least leaking due to low pressure on the diaphragm and bleeding off some metered air.
Sounds like it anyway |
sounds like you have a boost leak, take a pvc end cap and drill n tap it for a compressor fitting, hook it to a compressor turn the pressure down to about 15 psi and start spraying all the joints with soapy water, spray the bov too, im sure you will ifnd alot of leaks. the computer is putting in ful for the measured amount of air, when some gets out its still putting in fuel for the amount of air that went through the maf, so it feeds it fuel for air that isnt there.
i just saw that you cut ur bov spring, what that has done is allowed the car to push air out of the bov when entering boost, as the boost level raises the pressure on the back of the diaphragm starts helping out and it stays closed. Put a tial q on there and never worry about it again. |
Originally Posted by 1slowna
(Post 721611)
sounds like you have a boost leak, take a pvc end cap and drill n tap it for a compressor fitting, hook it to a compressor turn the pressure down to about 15 psi and start spraying all the joints with soapy water, spray the bov too, im sure you will ifnd alot of leaks. the computer is putting in ful for the measured amount of air, when some gets out its still putting in fuel for the amount of air that went through the maf, so it feeds it fuel for air that isnt there.
i just saw that you cut ur bov spring, what that has done is allowed the car to push air out of the bov when entering boost, as the boost level raises the pressure on the back of the diaphragm starts helping out and it stays closed. Put a tial q on there and never worry about it again. From what I understand about bov's, vacuum is what tries to open it. If it stays closed at idle, why would it want to open approaching 0 vac? I've been paying more attention to my boost gauge and does flutter a bit under boost. That would indicate a leak right? My mbc is sourced from the cold side of the IC. Can I use the compressor wga source to do the leak test? It's capped off right now, but I still have the nipple. Thanks for all the help! |
Originally Posted by flounder
(Post 721631)
From what I understand about bov's, vacuum is what tries to open it. If it stays closed at idle, why would it want to open approaching 0 vac?
Honestly, I think it is time you moved on to a programmable ECU and deleted the MAF. The MAF is a restriction anyway. And the advice to look for leaks is a win no matter what else you do. |
If the bov leak is the cause, recirculating should solve the problem right?
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Originally Posted by flounder
(Post 721641)
If the bov leak is the cause, recirculating should solve the problem right?
However, what puzzles me is that it occured in conjunction with the IC install. If it was only BOV, then I would not expect to see this connection (i.e., you should have seen the issue before). I think you should look hard for other leaks as well. |
Originally Posted by hornetball
(Post 721657)
Yes. Recirculate to post-MAF.
However, what puzzles me is that it occured in conjunction with the IC install. If it was only BOV, then I would not expect to see this connection (i.e., you should have seen the issue before). I think you should look hard for other leaks as well. |
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