Since we are designing an intake coupler similar to the AEM, we obviously need to make sure that it doesn't have any collapse issues. I set up an AEM coupler to test to see how much vacuum it takes to collapse. It took more than 8" of vacuum and then collapsed at the large section of the tube, where vacuum would be the lowest under actual conditions. The small section of the tubing did not start to collapse until more than 12" of vacuum. At these levels of restriction, there would be 50-100hp to be gained by simply running a better flowing intake setup, which we know is not the case. My question is- Has anyone actually witnessed the AEM tube collapsing? Or is this just a theory that was developed based on compressor surge taking place?

 

Could the temperature of the elbow cause it to fold earlier in a hot engine bay?

I've never measured vacuum on an intake, but I cant imagine we pull 8-12"... or even anything too close.

 

Higher temp causing more flexibility is a possibility, so that's a good point.
Yeah, vacuum pre-turbo should be less than 2", or there are gains to be had by running a better flowing intake.

 

I'm excited! The aftermarket segment is really turning for the BETTER for the cobalts! Peoples eyes will be wide-eyed with the potent lnf engines... well more so than they are already. Been talking them up

 

I know for certain something about its design causes compressor choke (indicated by radid BPV flutter) on cold start up. It will do this on the stock tune or any tune for that matter. I have tried everything I can think of to stop the fluttering to no avail tuning wise. The issues completely disappear though if you run the AEM intake hooked to the stock intake pipe that goes to the turbo. That makes me think the silicone coupler has to be the culprit. The AEM dry flow filter may be part of the problem though. It may be causing just enough restriction to cause the silicone tube to pulse like a heart beat. I am going to remove the filter later tonight to see if it hepls the issue or not. If it does I found a big ole K&N filter that will definately flow better than that dryflow. It has never fully collapsed to my knowledge. No other intake on the market causes this cold start compressor choke and no other intakes on the market have this design with a gigantic silicone reducer elbow though. I had a dejon SRI with a smaller AEM dry flow filter and never had any compressor choke with that intake.

 

This is very odd. I'm not saying there isn't a problem of some sort, but I can't see how there could possibly be a restriction at idle, regardless of the design. It just doesn't make sense to me. Either way, I'm interested to hear about your results. Hopefully we can come up with a design that flows better and does not have any side effects.

 

It is strange and it does it only in cat heating warm up mode. It is sucking in a lot of air during cat heating cold start considering it is at only 1400 rpms. Cat heating fueling strategy, combined with -16 to -19* of spark advance and the cat heating cam tables puts a relatively heavy load on the motor to produce those instantly hot EGTs. If we had access to the cat heating spark tables and the cold start lambda tables I believe I could tune the flutter out but we do not currently.

 

One time under 30 lbs boost, I feel the silicone coupler collapsed completly choking off the engine for a brief second. I cannot prove this but it never happened again after reducing boost. No CEL's or overboost/underboost flags either. Scared the hell out of me when it happened.

Other issue I cannot prove but went away with the intake was a lurch when coming out of DFCO like the coupler was flexing causing flow issues. Sorry I can't document it better. If the silicone coupler was stiffer it may not be an issue.

 

what about some type of spacer placed inside between tubes and then covered by the cylicone? even create a spyral effect??

 

My only issue with the elbow installed was a slight hesitation/stumble just off idle. This was with stock filter and sans snorkle mod so completing airbox mod might help. I was also untuned so I can't comment on higher boost levels.
Don't know if it's feasible but I'll throw this out there: Can you wrap a silicone elbow with carbon fiber? Might help to stiffen things up-would look better as well.

 

will this help, maybe? http://nipponpower.com/view.phtml?f_...e+Hose+Coupler

 

I have the results and it seems that with the filter removed the issue is gone. The gauge went from reading 6 inches of vacuum to 10 inches of vacuum with no changes other than yanking the filter. So that tells me it is definately taking a load off the engine. It is that dryflow filter they use! Even though it is sizeable it apparently causes quite a bit of restriction. Use a big K&N or similar type filter and you should have no issues. I am going to order a 3.25"inlet 8" long Part # RU-5122 on my car. That should help airflow.

 

Pics, and Part No.!!!

 

Part No. Is there. Link to K&N store. http://store.knfilters.com/search/pr...x?Prod=RU-5122

 

Holy ****! That's pretty long for a filter....

 

Was this the A pillar gauge reading in cat warmup mode or an external gauge connected elsewhere?

 

I have Iambrokes old aem filter and have been running it since I got it. I have a dash hawk so I can also monitor anything you guys need if you would like to compare results on a different car my only mods are that intake gm stage 1 catless dp and a muff delete.
Let me know
Josh

 

That sounds like compressor surge, but not necessarily a collapsed intake tube.

Interesting, good find!

 

One big surge that choked off the engine? There was no pulsing at all like compressor surge. It acted like someone covered the intake blocking all air (or the tube collapsed). Sorry, no vid camera under the hood at the time. You guys know a lot more than I do.

I hope your intake performs as good as your DP that I have. Looking forward to it!

 

Yes, compressor surge on spool up is a situation where the turbo basically stalls and in most cases the motor misfires and stumbles as a result. It can still be caused by a collapsing or restrictive intake tube, but it's different than surging when coming off throttle.

 

I have some surge on cold startup, but I had that with the stock intake too. The stock intake just did a much better job of muffling the issue. I attribute most of this to cat warmup strategy, and the fact DI cars run some funky injection strategy during warmup too. Lots of fuel + retarded ignition = an unintended sort of cold idle anti-lag in addition to getting the cats lit.

I'm sure that rapid heating of the manifold + turbine housing is doing great wonders on them too.

No boost to get the wg open, so all of that has to go through the turbine wheel... thus the surge. Thus you have the BPV opening constantly to try and meet DAL. This is my theory anyway

Honestly, if HPT would get off their ass we'd have cold start issues licked.

 

The issue seems to disappear completely if you remove the filter from the end of the AEM intake. It is so loud when you have an open intake pipe. My car went from 5-6 inches of vacuum on cold start to 10 inches of vacuum with tells me that dry low filter is causing 4-5 inches of vacuum on cold start according to my testing procedure. Better flowing filter shoud help a lot. I am ordering that new K&N filter this morning.

Thanks just trying to help get this thing figured out. I am going to try that massive and less restrictive K&N on there. It should have way less restriction than that dry flow. I just ordered it, should be here in a couple days.

 

Interesting, that was my next step. I was going to try another filter in the spring as I never really liked those dry flow filters to begin with.

 

Yes the A pillar guage was where I got the readings. I know it is not the most accurate but taking the difference between the two readings still makes of a difference 4-5 lbs of vacuum. That is a pretty big difference if you ask me.

It is bigger than the dryflow fiter that is on there. It will fit though. I might have to shave the coupler end down though it looks a tad long but it was the best size overall I could find.

I think you might have experienced compressor stall.

 

Term, are you planning on trying the new K&N filter with the AEM elbow and stock elbow setups?