overboosting 25 psi

[spocks90talon]

ok guys this problim happend to me once before i thought i fixed it but its back, my evo316g powerd 91 gsx, has a bad over boosting problim, and i dont know why. in 3rd and 4th and 5th gear it will boost all the way up to 25 psi untill it fuel cuts, its happend twice so far so i havnt been boosting the car so i dont break anything. last week me and a dsm buddy reran the vacuum lines so there is no stock bcs and it doesnt have a mbc, he ran the line comming out the front of the crushed bov the the tee that the wastegate and the vacuum line off the lower intercooler pipe are connected to. all the emissions stuff is off or pluged up egr i got a block off plate. no boost leaks, good compresson. vac is at 19-20 psi at idle. last time it did this it only would boost 20 psi, i still had the stock bcs at that point though, but i fixed it, it ended up just being loos turbo and manifold bolts, i tighted them and it stoped over boosting. i dont know why its doing this, maybe we ran the vacuum lines wrong?

 

[selmerguy]

Check the wastegate itself and the flapper to see if it moves freely. The wastegate is a simple thing so it is either vacuum(I know you said you checked it but check again) or a mechanical problem with the wastegate itself.

 

[alex99gst]

I couldn't quite understand if you have a MBC or not, but the vacuum lines should be run as follows. The BOV line should be a single line running to the intake manifold (nothing T'ed off it). The top line of the MBC should run to the wastegate actuator and the bottom to a boost source preferably close to the turbo.

 

[delta448]

to add to the above post...

You should not have your BOV connected to anything before the throttle plate. When the throttle plate closes, the engine is still trying to suck air in behind it, creating a vacuum, which pulls open the BOV's diaphram. If your BOV never sees vacuum it never opens and your turbo keeps trying to increase pressure in front of the throttle plate.

 

[MyBeatGSX]

^ No it won't cause a huge boost spike. It will back up until it hits the turbo and takes it from 100,000rpm to 0rpm in about 0.001 seconds... which of course causes things to explode.

This could be normal boost creap, however you shouldn't be fuel cutting at 25psi on an E16G. Are you SURE you don't have a boost leak?

Do what everyone else said and reroute your lines. If possible, the BOV and the wastegate should have their own lines. Try not to tee anything off the wastegate line either, this will slow response time.

Does it go to a set boost and then work its way up to 25psi? If so, this is just severe boost creap. Or does it just shoot right up to 25psi? In this case you're wastegate is broken or the reference line is not properly hooked up.

 

[delta448]

^ No it won't cause a huge boost spike. It will back up until it hits the turbo and takes it from 100,000rpm to 0rpm in about 0.001 seconds... which of course causes things to explode.

Unless the pressure on the exhaust side is enough to overcome the pressure on the compressor side, and keep the turbo spinning in the correct rotation, -albeit slowing its rotational speed down considerably. -This would be a great way to create a big boost leak, by blowing intercooler couplers off in a few hundreths of a second.

This could be normal boost creap, however you shouldn't be fuel cutting at 25psi on an E16G. Are you SURE you don't have a boost leak?

Isn't fuel cutting caused by MAS overrun? If he doesn't have tuning hardware to allow more airflow... ? -Just not sure what the E16G has to do with fuel cutting. -?

 

[MyBeatGSX]

Its call surge. Regardless of what sequence it happens in, something will get broken if it happens under high boost.


Because 25psi on a small turbo isn't going to overrun the MAF. I've hit fuel cut once when my LICP blew off, the airflow was well over 2,500hz. You aren't going to see 2,500++hz of airflow with that turbo just boost creeping.

 

[GVR4592]

You need to be more specific in your description of the problem. When exactly did it start creeping? Do you have a large downpipe/exhaust? Is the turbo ported? If so who ported it? Does it go past 25 psi or does it stop at 25? Have you tried eliminating the manual boost controller and just running a line from a boost source to the wastegate?

 

[delta448]

Because 25psi on a small turbo isn't going to overrun the MAF. I've hit fuel cut once when my LICP blew off, the airflow was well over 2,500hz. You aren't going to see 2,500++hz of airflow with that turbo just boost creeping.

I'm not trying to dog you here or anything, -you are giving good info-, (so please keep posting, I'm hoping you can teach me something new) I'm just curious how you can run 25 psi on a turbo larger than the stock one, when he has nothing to offset the MAS signal and the stock setup fuel cuts at roughly 16-17psi.

I see that you have an * SAFC II, AFPR, 255lph, and 550's; when you hit the above mentioned fuel cut were any of these installed? -I'm just guessing, but did you get that 2,500hz number from your installed SAFC?

 

[MyBeatGSX]

There's something wrong with your car if your stock setup fuel cuts at 17psi. I ran a small 16G for 2 years at 18psi (with creep to 20psi) with no SAFC and never hit fuel cut once.

I know 1G MAF's max out and fuel cut much lower, so this may be the difference.

Yes the SAFC was installed. I know its not exactly pocketlogger accurate, but its what the ECU is seeing. Even with my MAF singal offset from the SAFC, I still think he would have a hard time pushing numbers high enough to fuel cut.

 

[Dream On]

Sounds like if you don't have a MBC or the stock BCS that you should just connect a line from the j-pipe to the wastegate and leave the BOV alone with no T's in it.

 

[spocks90talon]

ok sorry for taking so long to reply, my internets been down. i have no mbc or stock bcs, it stops at 25psi it creeps up from 11psi to 25 at about 4500 rpms. im gonna run my j pipe to my wastegate for now ill post back in a little bit

 

[spocks90talon]

okkk, just reran the lines, j pipe to wastegate. no more over boost from what i can tell but i didnt really dog it to see. vac is at about 18-19 at idle which is preatty good, but its only boosting about 8-9 psi now which is so slow. so my question is if i hook the stock bcs back up will its boost 11-12 psi again? will it still hold 20 psi vac at idle? can i run one line from the wastegate to the bcs and the other line from the j-pipe? i blocked off the line that is supposed to come out of the mas. oh and i just put a full 3inch turbo back dejon tool exhaust on last week to answer that question. thanks guys

 

[GVR4592]

Where was the line running before? Do you have a mbc?

 

[delta448]

Keep the j-pipe to WG actuator setup and buy a MBC. Overboosting is usually due to WG issues, probably the T-ing off of the actuator line in this case. Get a MBC and boost gauge, then you can run 15-16psi safely.

 

[Dream On]

Man, I kick ass at solving simple problems.

 

[GVR4592]

How did you solve the problem?

 

[spocks90talon]

ok, ill buy a mbc with my next check, does anyone have any suggestions on which boost controller i should buy? im happy with my dejon tool exhaust, has anybody have any experence with dejons boost controllers? what about my blow-off valve line, my buddy said i should run that to the intake mani. would that be ok?

 

[alex99gst]

You will want to run a singe line from the BOV to the intake manifold with nothing T'ed off of it. As for experience with the dejon boost controllers, I purchased one from them when I got my intake and I was very pleased with it. It is the same as any other type of ball and spring MBC though.

 

[kraka]

Im sorry, but if your not familar with a evoIII, then your not expecting bad boost creep...

I guarantee you this is a bad case of it...If you cut the divider on the exhaust side of the turbo tho, you can eliminate it...

Watch your boost gauge...Does your boost shoot up to the psi you set it to then start moving up to 25psi, or does it right away spike up to 25psi
?

 

[GVR4592]

Im sorry, but if your not familar with a evoIII, then your not expecting bad boost creep...

I guarantee you this is a bad case of it...If you cut the divider on the exhaust side of the turbo tho, you can eliminate it...

Watch your boost gauge...Does your boost shoot up to the psi you set it to then start moving up to 25psi, or does it right away spike up to 25psi
?

You must've missed the part where he said he doesn't have an overboosting problem now that he correctly routed his vacuum lines.

 

[alex99gst]

You must've missed the part where he said he doesn't have an overboosting problem now that he correctly routed his vacuum lines.

That, and the fact that cutting the divider in the housing is the "easy way out," which is not always the best way. The best way to eliminate boost creep is through porting the turbo.

 

[oldman]

Something isn't right here, changing your boost source will not cause or solve boost creep. I suspect this isn't boost creep (probably out of control boost) to begin with or something else is at play. How did you have it hooked up before you switched to the J-pipe? If you were creeping before, you will be creeping now!

 

[GVR4592]

It's not boost creep, which is why I asked where he had the lines routed. I don't think he had it hooked up to anything.

 

[spocks90talon]

thanks for all the help guys one more question then we can kill this thread, in about a week ive decided im gonna buy a gen2 mas setup for my car, as well as a mbc. still have stock injectors, but i do have a walbro 255 in my tank, if i set my boost to like 16-17 do you think ill hit fuel cut? i was talking to the guy at dejon when i bought my exhaust and he said the i could run that boost without a fpr as long as i upgrade to the gen2 mas setup. i dont know much about the gen2 mas system except that it flows a great deal more air than the gen1. my gen1 mas that i have on the car now is hacked, would it be worth it to do the gen2 upgrade? i know the masf translaters are the best option but i dont have that kinda money right now and i have a buddy that will sell me a gen2 setup for like $125-$150 bucks so if you guys think this is worth it...i want a street/strip car for now, maybe a 12 or 13 second car that i can "daily drive" for a little while