M20 ITB throttle plate question

[zaq123]

Ok finally got this ITB 2.9 M20 on the road and in the process of tunning with Haltech Nexus S2. If one needs ECU for Alpha-N, can't recommend Nexus high enough btw, super easy and straightforward. Also Alpha-N tunning is much more superior to MS2. Build in 4.9 WB makes it actually good buy for the price.

In any event. Those with ITBs...Have you had ITB throttle plates getting a little stuck after the car cools off overnight? It's not super cold in the garage, maybe 50s F, but that first throttle application is annoying as the throttle cable/linkage gets under some tension to free ITB plates up which results in a slight over rev. I guess one can get into to the habit to press on the gas pedal before starting the car but just wondering if it's gonna resolve itself or throttle plates need some adjustment (despite Rama's instructions not to touch them).

Thanks

[AWDBOB]

Are you running 100% alpha-n or blending it with speed density? I have a buddy with RHD ITBs whos been struggling with his cold start and idle for a while.

[zaq123]

pure alpha-N. MAP signal (from common for all runners vacuum block) is obviously being used for some AFR corrections as MAP can vary during some conditions with TPS being unchanged (e.g. up/down hill with fixed TPS)

[zaq123]

btw what ECU is he using? I did have idle issues but it was related to ITB throttle plate stop screw. I had it just touching when plates are fully closed (so I thought). Wasn't visible to the eye with ITB installed but plates were apparently open enough (not visible) for enough air for the idle to be way too high. Had to take ITB off and get that sucker dialed in so the screw is just barely barely touching. . I'm running ICV as well.

[digger]

what size feeler gauge can you fit (between the butterfly and the bore) with the throttles against the stop?
what is the idle ignition timing when the engine is fully upto temp?
what rpm does it idle at without the ICV when upto temp?

there will be some slight stiction with the throttles fully closed to allow for differential thermal expansion ( alloy bore expands more than brass butterfly) but depending how far the idle stop keeps the butterfly open at idle this can be managed/minimised plus it will somewhat bed in eventually.

[AWDBOB]

pure alpha-N. MAP signal (from common for all runners vacuum block) is obviously being used for some AFR corrections as MAP can vary during some conditions with TPS being unchanged (e.g. up/down hill with fixed TPS)

Good intel, I sent him this thread. He's using the ClassicDaily pnp. I was there when the ITBs were set up initially and it was difficult to set and sync the throttles- I've always questioned whether it was 100% correct.

[zaq123]

what size feeler gauge can you fit (between the butterfly and the bore) with the throttles against the stop?
what is the idle ignition timing when the engine is fully upto temp?
what rpm does it idle at without the ICV when upto temp?

there will be some slight stiction with the throttles fully closed to allow for differential thermal expansion ( alloy bore expands more than brass butterfly) but depending how far the idle stop keeps the butterfly open at idle this can be managed/minimised plus it will somewhat bed in eventually.

1.I didn't measure it. Rama's instructions were to fully close the throttle and have that screw just touching. I suspect it wasn't touching enough. I gave it 1/4 turn and ITBs are no longer sticking when the engine cools off
2. base set to 500-14.7 1000rpm- 19.2.. Haltech has idle ign correction table should idle be off target. So far fully warmed up it can go as low as 6-7 degrees to stabilize the idle.
3. Fully warmewd up car will not idle without ICV, will chock.

digger, what to do you think fully warm target idle should be set at for schrick 288 cam? I have it at 900, not sure if it's enough for 288. Idles ok but a little rough

[digger]

1.I didn't measure it. Rama's instructions were to fully close the throttle and have that screw just touching. I suspect it wasn't touching enough. I gave it 1/4 turn and ITBs are no longer sticking when the engine cools off
2. base set to 500-14.7 1000rpm- 19.2.. Haltech has idle ign correction table should idle be off target. So far fully warmed up it can go as low as 6-7 degrees to stabilize the idle.
3. Fully warmewd up car will not idle without ICV, will chock.

digger, what to do you think fully warm target idle should be set at for schrick 288 cam? I have it at 900, not sure if it's enough for 288. Idles ok but a little rough

You may have misunderstood Rama, On initial setup you set the 3 pairs so the throttle blades are fully closed/sealed (idle screw must be backed out far enough so it is not in play) so they all start from the same base position to minimize the time to balance them since they start fairly insync. But then you screw out the idle screw which moves all 6 butterflies together so there is a small slit for air to pass (analogous to the stock single throttle body stop being set with 0.x mm feeler gauge) that is large enough to allow enough air for the engine to idle at an rpm high enough for balancing (say 1200-1500 rpm) and then you adjust idle back down to the desired idle speed after balancing. This setup is done with no ICV or any closed loop idle control.

Idle speed depends where the engine is happy, i do the following (i don't have ignition control for idle, only closed loop ICV)

Hot idle 900-950 rpm with the ICV
Hot idle 700-800 rpm without the ICV (i.e., about 100-150 rpm lower than idle to give the ICV some range in either direction)

IMO The engine needs to be able to idle without the ICV (Some people don't even use an ICV). It sounds like the throttles are not open enough (this is why they were sticky and why it wont idle without the ICV) i would try screw them out ever so slightly more so it idles around 700-800 rpm (or as low as the engine can while still being somewhat happy which might be 600 on your engine) with the ICV isolated/blocked off and no closed loop idle control active. Once you crack it open slightly more it will need less ignition timing in order to bring the idle speed down.

Since i don't have ignition control for idle i set the timing higher at lower rpm so it tends to bring the engine rpm back up to reduce chance of stalling.

[zaq123]

Thank you digger, since everything is assembled, no filler gauge but I was able to adjust the screw to idle with ICV plugged in and in open loop at about 700, engine idled steady although not exactly happy. Should I keep opening those TB plates more till I get it happy?

[digger]

Thank you digger, since everything is assembled, no filler gauge but I was able to adjust the screw to idle with ICV plugged in and in open loop at about 700, engine idled steady although not exactly happy. Should I keep opening those TB plates more till I get it happy?

700 seems ok

[zaq123]

700 seems ok

not related to this subjet but I recall years ago you've been searching for a valve cover gasket that doesn't leak.. Have you found one? Or you use some sort of gasket dressing with good results? I can new Goetze gasket (my old stock of M20 things) is sweating with oil and it only has been 50 miles on it. The same was with Elring I had on it before the first heat cycle/valve clearance check.

[digger]

not related to this subjet but I recall years ago you've been searching for a valve cover gasket that doesn't leak.. Have you found one? Or you use some sort of gasket dressing with good results? I can new Goetze gasket (my old stock of M20 things) is sweating with oil and it only has been 50 miles on it. The same was with Elring I had on it before the first heat cycle/valve clearance check.

These days i like to use the OE gasket with the embossed face and a very thin coat of non hardening aviation cement loctite or permatex brown sticky stuff. the rubber bungs seal with a bit of rtv type product. surfaces need to be very clean. make sure the valve cover isnt getting hung up on the rocker shaft locking bar. Also i think the key is to periodically retorque a couple times after heat soaking and cooling it off as the gaskets "relax" and the preload / clamp reduces initially after the first half dozen heat cycles

[zaq123]

You may have misunderstood Rama, On initial setup you set the 3 pairs so the throttle blades are fully closed/sealed (idle screw must be backed out far enough so it is not in play) so they all start from the same base position to minimize the time to balance them since they start fairly insync. But then you screw out the idle screw which moves all 6 butterflies together so there is a small slit for air to pass (analogous to the stock single throttle body stop being set with 0.x mm feeler gauge) that is large enough to allow enough air for the engine to idle at an rpm high enough for balancing (say 1200-1500 rpm) and then you adjust idle back down to the desired idle speed after balancing. This setup is done with no ICV or any closed loop idle control.

Idle speed depends where the engine is happy, i do the following (i don't have ignition control for idle, only closed loop ICV)

Hot idle 900-950 rpm with the ICV
Hot idle 700-800 rpm without the ICV (i.e., about 100-150 rpm lower than idle to give the ICV some range in either direction)

IMO The engine needs to be able to idle without the ICV (Some people don't even use an ICV). It sounds like the throttles are not open enough (this is why they were sticky and why it wont idle without the ICV) i would try screw them out ever so slightly more so it idles around 700-800 rpm (or as low as the engine can while still being somewhat happy which might be 600 on your engine) with the ICV isolated/blocked off and no closed loop idle control active. Once you crack it open slightly more it will need less ignition timing in order to bring the idle speed down.

Since i don't have ignition control for idle i set the timing higher at lower rpm so it tends to bring the engine rpm back up to reduce chance of stalling.

ok I must report that the above greatly improved things, both idling and driving. ICV now has very short range to correct and the engine idles extremely steady at 900 rpm target even with AC compressor going on/off

digger, what is your average MAP vacuum at warm idle? Hot idle I see -6.5 inHg as an average with AC on or around -8inHg no AC (atmospheric pressure is counted as zero 0inHg base line). Car has under 100 mile on the engine so rings are probably still are setting. Just was wondering if it's a typical vacuum numbers with ITBs and 288 Schrick cam

[digger]

ok I must report that the above greatly improved things, both idling and driving. ICV now has very short range to correct and the engine idles extremely steady at 900 rpm target even with AC compressor going on/off

digger, what is your average MAP vacuum at warm idle? Hot idle I see -6.5 inHg as an average with AC on or around -8inHg no AC (atmospheric pressure is counted as zero 0inHg base line). Car has under 100 mile on the engine so rings are probably still are setting. Just was wondering if it's a typical vacuum numbers with ITBs and 288 Schrick cam

my MAP is working as an ambient/barometric pressure device only with the Alpha-N. i did have it setup as a MAP at one point way back, and so 8-10 sounds about right tbh. thats a big cam for a small inline 6. The only issue with low vacuum is the booster potentially but if the brakes are ok then all good. I am using the E90 booster

[zaq123]

my MAP is working as an ambient/barometric pressure device only with the Alpha-N. i did have it setup as a MAP at one point way back, and so 8-10 sounds about right tbh. thats a big cam for a small inline 6. The only issue with low vacuum is the booster potentially but if the brakes are ok then all good. I am using the E90 booster

don't tell me 288 is tooooo big haha. You recommended it for my 2.9 and ITBs , the only reason I got it. Still breaking in the engine before I dyno it but I gotta say it pulls extremely nice after 2.5-3k rpm. 3.64 ration rear btw. I have baro in addition to my map, just in case i go up in the elevation.