Changed intercooler, now she idles at 45kPa
 

Gentlemen,
I hope 2019 is treating everyone well.
I've been running the tiny 12" core intercooler supplied with my Kraftwerks Rotrex kit for the past three years. It was beat up pretty bad. I got a good deal on a Vibrant 18" core and set about replumbing the i/c piping. I took the opportunity to replace the Kraftwerks supplied 1.75" tubing from the Rotrex to the i/c with 2" tubing. I started her up yesterday to check for vacuum leaks and such and found she was idling at about 45kPa and would not come down to the 900 rpm idle in the target curve. She normally idled at about 32-34kPa. Unfortunately, my O2 sensor has shit the bed. The car runs smooth with EGO off, but was very rich. I pulled about 6.5 units from the VE table to get her to idle in the 13s (when it appeared the sensor was reading correctly). I did not find any vacuum leaks.
Would changing the intercooler and going to the larger ID tubing change the tune that much at idle or did I miss something? I know the rest of the fuel table will need some work, but will she need a complete dyno retune?
Current tune and a data log of her just idling attached.
Thanks,

Is the bypass valve working?

I dont see how IC piping affects idle vacuum even if it was fully unhooked unless somehow bypass wasnt working, which at some rpm would keep pushing air into intake reducing vac slightly

If its not that, almost certainly a vacuum leak somewhere or Idle valve (whats the idle pw at when this happens?)

Idle PW was between 1.863 and 1.876 or so, and the rpms were not as smooth as I had thought. She was idling between 1000 and 1100.

I meant idle pw % for the idle valve

You're doing 1000 rpm at 45 kpa. That means something is seriously bad. It should be >2000 rpm with 45 kpa, given normal AFRs. Is the engine still running on all 4 cylinders?

I did not check the barometer yesterday. We're at 30.42 today. I noticed in the log boost was showing -8something pounds. I usually see -10 or so at idle.

Your Idle valve is at 16%, I will assume thats the minimum value (its usually 18 on the NB2 one) which means you have a vacuum leak, make sure you plugged in all your vacuum lines (my bet is on bov/bypass valve vac line, since you replaced the stock 1.75" tube that connects to the BOV)

I don't think there is any other possible explanation. Did you also have some sort of catch can on PCV side?

The idle valves can go through an inversion, where a decrease in commanded DC results in an increase in effective valve opening area (and subsequent increase in manifold pressure/engine speed). In other words, they aren't monotonic. I don't have much experience with the NB valve, but 16 sounds really low to me. Have you appropriately configured the valve limits? The NA valve inverts in the mid-20s. The control system assumes (requires) a monotonic response. I suggest switching to open loop and characterizing the hot idle rpm vs valve DC over the entire range.

Just for reference:
on my MSM Idle valve minimum duty is 18% @511Hz,
also all seen basemaps for MSM from Reverant have 18% too.
Most likely MSM Idle valve is the same as NB2.

All of this conjecture is kinda useless until OP gets his WB fixed and makes sure the idle mix is right. May still be so rich it's drowning and will cause the MAP to read low due to incomplete combustion. I think it was mentioned but idle shouldn't be affected pre TB, if you had a vac leak post TB you would just have a high idle but not low map.......which circles us back to something causing the motor to run rough.

Last night I checked all the hose connections. Today, I replaced the O2 sensor and started her up. The cells I removed fuel from yesterday were wreaking havoc on the idle whilst she warmed up. When the rpms would move through those cells, the AFR would go up into the 19s, then drop as the tune went into different cells. I reviewed the log and made some mods to the VE table and started over. The second log is attached along with the current tune. I did end up with roughly the same numbers in the 40 and 50 load cells for 900 and 1200 rpms, so I suspect on cold start tomorrow she'll behave the same way.

When I pulled the fuel, I got almost zero change in load. I fanned the throttle a few times, but no change to rpms or load.

Towards the middle of the log I went to Open Loop and there was no noticeable change to how she ran or sounded. The Open Loop target curve looks pretty good, but changing to open Loop didn't get the rpms down to 900 or the load below 43.

I also ran the Idle Valve test starting at 1826 seconds. The numbers were pretty close to what I got the last time. The rpms stopped dropping at 17 and hovered around 1100 rpm unless I went all the way down to 2 on the valve. 19 gave 1200 rpm. 21, 1300. 25, 1400. 27, 1500. 29, 1600. 31, 1750, but the AFRs were dipping to the low 11s. At 38 she read 2150 rpms and 10.9 AFR. I stopped testing at that point and ended the log.

If you scroll to 1600 seconds, you can see she's very smooth, but still idling at 43kPa. I could have rested my beer on the cam cover.

I used some starting fluid to check for vacuum leaks and didn't find any, again.

I'm completely at a loss for what to do next. Air screw? The only changes to the engine are the larger intercooler--3.25 x 6.5 x 18 vice 2.5 x 6.25 x 12 inches, and the 2" tubing from the Rotrex to the intercooler vice the 1.75" tubing. That's a lot more volume.

Thanks for taking a look.

The valve obviously works differently than an NA, and as another poster mentioned, your fuel is jacked. It appears as if you may have more than 1 issue here.

I'm okay with the fuel being jacked. I just want to know and understand why. If I should have expected this after enhugificating the intercooler, I just want to know what the theory is. Or if reducing the restriction out of the Rotrex caused it, I would have thought things would go lean, not rich. I need some schooling if there's a routine explanation. If this isn't routine, I still need help.

Thanks,

Based on the numbers you quote up there, you have a significant reduction in perceived VE, which is indicative of a fundamental issue in the fueling process. I rarely open logs or tunes from the forum anymore, but if the car ran well with good fuel control prior to installing the IC, AND you didn't make any changes to the tune, then it is highly likely something not directly related the the IC is your problem.

Do I really have a problem, or do I just have a pressure drop from the larger intercooler and pre-intercooler piping? The research I've done indicates that's a yes, but I had no idea it would be so much. Unfortunately, I'm not smart enough about this to connect a pressure drop to the 45kPa idle, or why it doesn't drop all the way down to 900 rpm as in the Closed Loop Idle Curve when she's fully warmed up.

The engine is a part-out pull that had about 62k on it. I dropped in an MSM intake cam and bolted all my stuff back on for my last two events in Nov '18. I checked base timing. It was spot on. The motor was strong. I did my best lap ever at VIR, a 2:15.27. Nothing has changed but the intercooler and pre-cooler piping sizes. The post cooler piping is different, but the same size, 2.5". I would say there's more tubing length post intercooler than there was before.

The Kraftwerks supplied intercooler was pretty beat up, but it also wasn't up to the task when ambient temps got near 100 degrees. I'd see 165 degree IATs on track on hot summer days, so I decided to go bigger rather than just replace it.

Is there a better way of searching for vacuum leaks than using starter fluid?

Thanks,

Again, it is almost impossible for whatever is before your TB to cause this issue. You can easily test this, remove the tubing at the TB and just put in an air filter (or just run it open, good enough to idle for a few minutes)

I recently installed a rotrex system using a bigger core than you, 2.5" hose (re-used 1.75 tubing with bung for bypass valve on hotside) and my vacuum is the same as stock (28-29kpa when hot at 850rpm), didnt touch anything else in the car besides installing the whole thing.

Your Idle valve is at minimum (although if you have a squaretop like me you should set the minimum to 18%, but that doesnt matter, i've tried it as low as 0% and makes no difference).
Its almost certain you have a vacuum leak somewhere

Do these steps:
1: Unplug intercooler piping from TB, install just a filter or leave it open, doesn't matter for few minutes of idle testing with plate closed.
2: Route PCV valve like OEM into top of manifold, leave exhaust side open to atmosphere with a filter or something. If you want, you can just plug the hole in the manifold to rule this out completely and leave both sides of the cam cover open.
3: reset your tune to whatever it was before you changed anything, even with this issue the fueling should still be perfect, even with broken O2
4: Plug all the holes in the intake manifold except the MAP signal to your ECU (if your ECU is easily accessible, run a new temporary tube into it to rule out some leak there) this includes any tubing for the bypass valve vac, boost gauge etc..

Also you can take some pictures of stuff I guess, we might spot something.

Report back how it works. Things have to be done methodically

Alrighty then... I pulled and plugged the Recirc Valve vacuum line and started her up. The car was already warm. She idled at about 31kPa and slid all the way down to 900 rpm. She even wanted more fuel. I'm still using the Kraftwerks supplied valve which looks very similar to the Turbosmart Kompact. I had taken the valve apart to lube the piston, but had done that a few times in the past without issue. At least I know where to start.

Thanks much!

Just to follow up... I could not locate the vacuum leak at the recirc valve externally. The Kraftwerks supplied valve has six o-rings, plus the banjo bolt must seal against the banjo for the vacuum line. I could not source replacement o-rings locally, so I tried Sylglide on all the o-rings, and replaced the o-ring beneath the banjo with a fiber washer without any luck. Instead of futzing with it any longer, I replaced the valve with the Type 10 from Silicone Intakes. The vacuum leak is gone and she's idling around 30kPa. That's lower by a couple than I have been able to reach in the past. She also needed more fuel across the entire VE table.

Thanks again,