rossman Posted January 22, 2019 Share Posted January 22, 2019 It looks like gaps on either side of the valve at 35%. At 0% there is a gap on the right but none on the left. It looks defective to me. Quote Link to comment Share on other sites More sharing options...
bradyzq Posted February 18, 2019 Share Posted February 18, 2019 I've often seen Bosch IACs closed at around 20%DC, not 35. Have you physically confirmed via idle speed that 35% gives the lowest? Quote Link to comment Share on other sites More sharing options...
nmehdikh Posted February 20, 2019 Author Share Posted February 20, 2019 I got in a new IAC, but haven't had a chance to mess with it yet. I'll try your suggestion this weekend, thanks for the input. My bigger issue is that I wasn't really getting any change in idle speed regardless of the position of the idle valve, which leads me to believe I may have a vacuum leak to hunt down as well. Quote Link to comment Share on other sites More sharing options...
Xander Posted February 20, 2019 Share Posted February 20, 2019 On 1/22/2019 at 12:29 PM, rossman said: It looks like gaps on either side of the valve at 35%. At 0% there is a gap on the right but none on the left. It looks defective to me. This is exactly how it should operate. The valve body is barrel shaped. at 0% the internal spring is relaxed. when the voltage goes up (duty cycle increases) the barrel will turn to the right. at first the right side is open, then it will close up, and then it will start to open on the left side. I use a similar air valve like this with a simple $15 chinese PWM power suply. works great. I can adjust the idle rpm with a small dashpot on the center console. Quote Link to comment Share on other sites More sharing options...
rossman Posted February 20, 2019 Share Posted February 20, 2019 Good to know! I had assumed that the valve is shut at 0% similar to my 90s Ford AIC valve behaves...at least that's how I remember it. Quote Link to comment Share on other sites More sharing options...
bradyzq Posted February 21, 2019 Share Posted February 21, 2019 What frequency are you operating it at? Quote Link to comment Share on other sites More sharing options...
nmehdikh Posted February 23, 2019 Author Share Posted February 23, 2019 99hz. The valve moves as expected, and responds to ECU commands. I just wasn't getting a change in RPM, which lead me to believe I had a vacuum leak. Which made me check the valve at "closed" and it was still pulling in air. Quote Link to comment Share on other sites More sharing options...
nmehdikh Posted February 26, 2019 Author Share Posted February 26, 2019 (edited) I'm really scratching my head over this. I swapped out the IAC with a new one. Car idles stable at 550 rpms, but regardless of what the IAC is doing, the RPMs don't change. The valve is physically opening and closing when commanded by the ECU. (click the pic for better quality) At fully closed, the valve is still moving air through it. At fully open, the valve is still moving the same amount of air through it. Blocking the valve with my hand kills airflow to the engine and stalls it. Car is warmed up to temp and idling stable in the log. The only possible thing I can think of is the plumbing from the IAC to the ITBs isn't large enough to move enough air, but I seriously doubt this is it. Any ideas? Edited February 26, 2019 by nmehdikh Quote Link to comment Share on other sites More sharing options...
madkaw Posted February 27, 2019 Share Posted February 27, 2019 What size hose runs to the IAC? 550 rpm is really low for an L motor and really low for a large cam engine . You should be closer to 900 rpm. Cold timing advance will help idle a lot . Tuning warm up idle is not easy and factors in a lot of things . What timing are you running at idle , should be at least 15-17 degrees . You could set in about. 7 degrees advance at cold start up . You could try setting your idle adjustment for engine to idle with IAC clamped off when at tempature , then try and tune in a fast idle at warm up Quote Link to comment Share on other sites More sharing options...
bradyzq Posted February 27, 2019 Share Posted February 27, 2019 (edited) First, I suggest setting the itbs so that you can achieve a warm idle of say 900 rpm as mentioned, WITH IAC BLOCKED OFF. That way, you know the absolute lowest rpm you can achieve with the IAC. Now unblock it. Try to incrementally increase duty cycle in 5% steps starting from zero. If the idle starts to drop towards 900, you are on the right track. Find the lowest point and make that your minimum DC. Edit: umm, basically, what madkaw said... Edited February 27, 2019 by bradyzq Department of redundancy department Quote Link to comment Share on other sites More sharing options...
nmehdikh Posted July 4, 2019 Author Share Posted July 4, 2019 Finally hit the dyno, made 190 horsepower to the wheels. Very happy with the results.https://photos.app.goo.gl/qB5vufWp9q44WQiA9 Quote Link to comment Share on other sites More sharing options...
madkaw Posted July 4, 2019 Share Posted July 4, 2019 You should post up your engine specs ! Not really sure from this thread what you did to achieve this. Stock cam? Did you use the L26 block? Quote Link to comment Share on other sites More sharing options...
nmehdikh Posted July 4, 2019 Author Share Posted July 4, 2019 I don't know anything about the bottom end of the engine, just that the block is stamped L26 and it has flat pistons. The head is a N42 that I only had rebuilt and got a Isky L-490 cam on, as well as new valve springs etc. Didn't do any head work. The header is a "Top end performance" 6-2-1, with mostly a straight section with followed by a relatively small magnaflow muffler. Besides that its just the whole EFI / ITB setup. I'm honestly very surprised how much power it made, I was expecting 160-170ish. Quote Link to comment Share on other sites More sharing options...
nmehdikh Posted July 20, 2019 Author Share Posted July 20, 2019 Bodywork and paint done by my dad. Paint code is NH0, Honda championship white Quote Link to comment Share on other sites More sharing options...
nmehdikh Posted August 12, 2019 Author Share Posted August 12, 2019 Had some time this weekend to buff the paint and start putting it back together. Still need to get the front end put together. Quote Link to comment Share on other sites More sharing options...
madkaw Posted August 12, 2019 Share Posted August 12, 2019 Looking great Quote Link to comment Share on other sites More sharing options...
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