I have MY99 EJ25 boosted to 5.5 psi non-intercooled. O2 voltage reads .85 and up all the time. ITC has timing retarded 2 degrees at 2400 rpms, and 8 degrees from 4000 up.

But I still get a little hesitation, always at almost exactly 4000 rpms. If I decide to squash the throttle when I'm cruising around 3500, the car will pick up then buck once when it hit 4000 rpms and then start flying.

Do I need to pull back timing even more at 4000 rpms, I don't have this problem anywhere else in the rev range and I haven't heard any pinging for a long time. Should I add more fuel? How can I tell if my knock sensor is activing?

Whoo yeah, sounds like the knock sensor going into overtime. What octane gas are you running? What are you using to control fuel.

I only use premium gas which is 92 octane in SoCal. I have a Paxton rising rate fpr with the base pressure set at 50 psi. I also have an AFC giving extra fuel whenever throttle position is anything more than leisurely cruising.

Maybe if you go to the ISR grand opening, I'll help you tune it. But it does sound like you stock knock sensor.
www.wonderlan.com/~hksuupra (http://www.wonderlan.com/~hksuupra)

I have that exact problem with my '99 RS and I only have a cone filter!!! No Turbo. I took it back to my dealer and they cleared the computer so the car thinks it just got off the boat and bam! Cured! smooth and fast again....then a week later.....it returned! DAMNIT!

I am going back with the car and they are going to hook up the monitor thing and we will drive it with it hooked up. I will let you know what we find, if anything. But I'm not sure it is related as you have a turbo.

curtis

It just appears that timing is more advanced at 4000 rpms than anywhere else in the rev range. Before I had the ITC hooked up, I was getting more detonation at 4000 rpms than I was at the higher rpms which is not what I would have expected.

I'm going to try to make it to the ISR "10 year grand opening anniversary," but I'm not quite sure if I'll actually have the time to drive up there.

Tim - a couple things to look for:

1. MAS - is it dirty? wet? could cause the problem easily.

2. Too much fuel - you're using high fuel pressure and an AFC.....it's orta aplleas and oranges, but as a point of reference, I cannot use my AFc at all...if I do, I get bucks all over the place because its allowing too much fuel to get in to teh combustion chamber, thus "choking" the car. If I leave it at zero (which I do), it runs great. Also, what rising rate is your regulator per pound of boost? If it is a typical aftermarket of 5 or 7:1, this could also be a problem. again,as a point of reference, I run the stock regulator and the adjustbale fpr (Magnetti Marelli) which is a 2:1 regulator; at 1.1 bar, I am running arouns 82-83 psi.

3. Try resetting the ecu. I hada hesitation last week around 3500 that was consistent, no matter if it was on or off boost. I disconnected the battery for about an hour while I ate dinner at the shop, then hoked it up, let it idle for about 5-10 minutes, and all was fine.

4. Too much ignition retard. That is a lot of timing to back off considering the boost you are running. have you tied a colder plug, to allow less timing retard (colder plugs "reist" pingning better, and going 1 step colder won't impact the plug getting fouled at idle). You may also want to try getting your hands on a cheap used intercooler, like from an olde WRX (they are usually only $100-$150) if you are not into drpping the $1k or thereabout for the Minnam/Spearco one.

Let us know how you make out.

Adam,

Thanks for your help.

1)I haven't checked the MAS.

2)I have a Paxton fpr which gives 1:1 rising rate. I have the pressure set at 50 psi at idle. The AFC is set so that it only gives fuel at hi throttle, and hi throttle is set at 30% so that it kicks in at anything other than gentle cruising. I have AFC giving fuel at 5% at 3000, 11% at 4000, 15% at 5000, and 18% from 5500 and up. The first O2 sensor always registers voltages above .85 at WOT (but it never gets much higher than .88).

3)I haven't reset my ECU lately, but it has a habit of screwing up all my settings with the AFC, since the ECU likes to relearn itself to be lean again.

4)I know it's a lot of timing, but if I advance any I will hear occassional pinging/detonation. I am running plugs that are a step (two steps?) colder than stock (they are heat range 7, I thought stock was 5 but the auto parts store told me they were 6s). I want to put on an intercooler, but I definately don't want to spend $1000 for the Minnam one (considering my turbo "kit" cost less than that). I would consider a WRX intercooler, but I heard that they wouldn't fit. Do you know what year/model I should look for to make sure it fits?

I also heard that Rimmer could make me a pretty nice, affordable intercooler (they use Bell cores). ISR told me that they could get me a small Spearco for about $500. What I'm really waiting on is for one of the members to upgrade and so that I can snatch up a decent used one. I'm not looking to exceed 7-10 psi, so I don't think I need the greatest intercooler.

Tim, I believe the trouble with WRX intercoolers is not really the actual size of it( the Minnams are much larger) but the fact that the plumbing is underneath the intercooler, causing problems with it laying in the engine compartment. I would think you would have better luck with a 93-96 because for one, overall it is a bit smaller and it only has a single inlet intercooler pipe whereas the newer ones have a dual inlet( taking up even more space underneath). I run one on a Legacy turbo but that is not a real good comparison but I don't think you would have any major problems with it. And like Adam said, you can find them dirt cheap. Just make sure to get the intercooler pipe as well. Good luck.