Cascade Crew

fiveoformula · Posted: Thu Jun 10, 2010 11:15 pm Post subject: Pop

I'm trying to diagnose a problem with the 'bird.
Last week I took it to the track, made about ten runs that were anywhere from 15.9-16.1 which upset me because my previous trip out there I was putting down 15.7's (I know, still no spectacular) but anyway, I really noticed a decrease in power at about 4k RPM and sometimes a slight pop at about the same time in the RPM range.
So the track is about ready to close and everybody is making there last run, I got a wild hair and decided to pull my air filter out to make a run. I then put down a 15.6 and my MPH went from 84ish to 87! and the really wierd thing was there was no pop, and no decrease in power. It was getting plenty of fuel every run, according to the wideband, about 11.0:1 so Im thinking maybe a timing problem?
Some of you guys might remember at Dyno I had a wierd dip in power at about that RPM too. So it has me brain storming... The car otherwise runs great with good fuel pressure, about 20-21' of vacuum.

aaron_sK · Posted: Fri Jun 11, 2010 12:51 am Post subject:

What does your TPS see when this "dip" happens?

fiveoformula · Posted: Fri Jun 11, 2010 12:58 am Post subject:

Hmm... good question. I hadn't thought about throttle position having something to do with it... But I will check!

Alphius · Posted: Fri Jun 11, 2010 5:34 am Post subject:

I would think that the TPS wouldn't make a difference. The throttle is already wide open and working fine before and after the "pop and dip". Maybe Aaron is right though, it is worth a look.

What are you running for air cleaner and filter? Drop base? Have a spacer? Filter size? Have you changed it or at least inspected it recently?

Seems to me that if removing the air filter fixed the problem, then the problem has to be with the air cleaner somehow. Do you still have the stock air cleaner you could put on for testing purposes? I'm really thinking that the aircleaner is causing a restriction under high airflow. Maybe it is deforming under load and vacuum (hence the pop) or just not flowing enough? Sometimes a drop base with a small size filter can cause a restriction.

Any way you can hook up a vacuum gauge or get vacuum readings during the loss of power?

aaron_sK · Posted: Fri Jun 11, 2010 9:44 am Post subject:

Bah. Pay no attention to posts I make at two in the morning. Razz

You are correct, Gabe, TPS signal should not change if his right foot doesn't.

The redneck test we always did was to tape a vacuum gauge to the windshield and run it WOT in third or fourth gear with the air cleaner on. If the gauge reads anything other than zero, buy a better cleaner.

Twilightoptics · Posted: Fri Jun 11, 2010 10:56 am Post subject:

Definitely an air restriction there somewhere.

fiveoformula · Posted: Fri Jun 11, 2010 11:00 am Post subject:

Well what I have for a filter is a 10" K&N open element, non-drop. Its kinda dirty... It doesn't seem like a big restriction.
If it has more than 0 vacuum at wide-open, doesn't that mean a restriction on exhaust side?

Twilightoptics · Posted: Fri Jun 11, 2010 11:55 am Post subject:

If taking the filter off made an improvement... thats inlet restriction.

An exhaust resitrction wont show a change in vacuum as far as I know. Cause the engine isn't really "sucking through too small a hole."

Alphius · Posted: Fri Jun 11, 2010 1:57 pm Post subject:

fiveoformula · Posted: Fri Jun 11, 2010 2:13 pm Post subject:

Well I'll clean it and see what happens. lol thats free.
I think im gonna run out at PIR again tonight, anyone else down?? Cool

blue89 · Posted: Fri Jun 11, 2010 7:08 pm Post subject:

Does it have a lean pop? My V6 did that a while ago. Any clue what your o2 sensor is reading at wot?

aaron_sK · Posted: Fri Jun 11, 2010 7:09 pm Post subject:

Alphius · Posted: Fri Jun 11, 2010 7:47 pm Post subject:

blue89 · Posted: Fri Jun 11, 2010 9:22 pm Post subject:

fiveoformula · Posted: Sat Jun 12, 2010 12:40 am Post subject:

Well I just got thru a crazy night... First run (with filter) it did it's wierd pop & power decrease at the end of each gear, and I ran a 16.1.
I pulled away after I got my slip then stopped to talk to someone for maybe a minute tops, THEN when I tried to pull away to get back in line, I feel this thump thump. Left rear tire flat. Mad

SO I called in a favor from a friend, he brought me 2 crosslace wheels he had, and I slapped them on the back of the bird.
Made another run with the filter on. kicked off a poppy 15.9.
THEN I took the filter out and made a new personal best of 15.5 @ 87.6 and kept climbing all the way to 5K RPM. WTF.

On top of all that.... Me, the woman, and Skyler went for some food afterwards, and when we tried to leave, Skyler's bastard of an audi wouldn't start.... No starter click or anything. We unsuccessfully tried to push start it, and I found out how out of shape I am.... So yep, long night.

fiveoformula · Posted: Sat Jun 12, 2010 12:42 am Post subject:

Dewey316 · Posted: Sat Jun 12, 2010 1:48 am Post subject:

If you are that rich, it could be unburnt fuel popping in the exaust.

rjmcgee · The Hammer Joined: 08 Jan 2004 Posts: 2320

Red Bird · Posted: Sat Jun 12, 2010 10:41 am Post subject:

maybe try usin one of those aircleaner lids that have a filter element so it can get some flow through the top.

fiveoformula · Posted: Sat Jun 12, 2010 11:14 am Post subject:

I just have a really hard time thinking that problem is the filter. I have had it on there for atleast 2 years.
It is getting alot of fuel WOT though.