I've searched on this topic with marginal results. A couple of weeks ago I installed a Turbohoses SMIC, Vibrant exhaust and Injen CAI. Since then, I've been getting an occasional really nasty hesitation at part throttle and less than full boost. It seems to be occurring between 3-4k rpms, but I can't ever seem to get my eyes on the tach right when it happens to know for sure. I'm aware that people have experienced problems in this rpm range and I've had some minor issues even before the mods, but nothing like this. It's almost violent, like someone just yanked 3 of my plug wires. The car will clear its throat after a second or two, then it seems o.k. It also seems to be most likely to do it when I'm going uphill in second gear, and when it's below 40 deg. F.
Tonight it did it going up the hill into my neighborhood on the way home, so I when I got to the house I grabbed my trusty vacuum/fuel pressure gauge that I've used to check boost before (I don't have a boost gauge yet, next on the list), ran a line into the car, and had my girlfriend ride with me and watch it to track the boost for a few minutes. I was surprised to find that my boost is now spiking to 8.5 psi and settling at 8 psi under WOT rather than the 6.5/6 psi I had before the mods. The SMIC and exhaust really made a difference. At first I couldn't get the problem to happen again. Apparently, at WOT and 7+ psi, it won't happen. Finally I got the car pointed uphill at about 2k in 2nd gear, rolled into the throttle slowly up to around 1/3 to 1/2, then wham, it did it. I can't remember for sure, but it seems like I might have lifted just a hair and that may have been what triggered it. I asked my g/f what the boost was doing, and she said it had steadily climbed to 6 psi and leveled off there before it did it. (Then it bounced around while the engine tried to sort itself out). This would tell me that it's not fuel cut (which was my initial suspicion), or else it would happen at higher boost as well.
FWIW, I've been over all my IC piping and checked most of the vac. lines that I can see. My factory hot and cold pipes are clamped with t-bar clamps, and they're really cranked down. I cleaned the EGR a couple of weeks ago. New IK20 Iridiums are installed. I really don't know what's happening, but I have to wonder if it's not seriously leaning out at part throttle and medium boost. When I dynoed last week, I was shocked to see how lean it is below 3,750 rpm. My dyno is attached. Disregard the A/F from my pull before the mods...their tailpipe wideband setup sucks. The new pull was with the wideband in the extra bung in the Vibrant, and the A/F results were similar over the next two pulls. I'm seriously considering DSM Convert's AFC, but wanted to see if there were any other ideas on this first. I may try another dyno session later in the week, as I'd like to try some part throttle pulls with the boost gauge hooked up and logging A/F. If could get the problem to replicate on the dyno, I'm sure it would help with resolving it.
Tonight it did it going up the hill into my neighborhood on the way home, so I when I got to the house I grabbed my trusty vacuum/fuel pressure gauge that I've used to check boost before (I don't have a boost gauge yet, next on the list), ran a line into the car, and had my girlfriend ride with me and watch it to track the boost for a few minutes. I was surprised to find that my boost is now spiking to 8.5 psi and settling at 8 psi under WOT rather than the 6.5/6 psi I had before the mods. The SMIC and exhaust really made a difference. At first I couldn't get the problem to happen again. Apparently, at WOT and 7+ psi, it won't happen. Finally I got the car pointed uphill at about 2k in 2nd gear, rolled into the throttle slowly up to around 1/3 to 1/2, then wham, it did it. I can't remember for sure, but it seems like I might have lifted just a hair and that may have been what triggered it. I asked my g/f what the boost was doing, and she said it had steadily climbed to 6 psi and leveled off there before it did it. (Then it bounced around while the engine tried to sort itself out). This would tell me that it's not fuel cut (which was my initial suspicion), or else it would happen at higher boost as well.
FWIW, I've been over all my IC piping and checked most of the vac. lines that I can see. My factory hot and cold pipes are clamped with t-bar clamps, and they're really cranked down. I cleaned the EGR a couple of weeks ago. New IK20 Iridiums are installed. I really don't know what's happening, but I have to wonder if it's not seriously leaning out at part throttle and medium boost. When I dynoed last week, I was shocked to see how lean it is below 3,750 rpm. My dyno is attached. Disregard the A/F from my pull before the mods...their tailpipe wideband setup sucks. The new pull was with the wideband in the extra bung in the Vibrant, and the A/F results were similar over the next two pulls. I'm seriously considering DSM Convert's AFC, but wanted to see if there were any other ideas on this first. I may try another dyno session later in the week, as I'd like to try some part throttle pulls with the boost gauge hooked up and logging A/F. If could get the problem to replicate on the dyno, I'm sure it would help with resolving it.
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