Jump to content
Sign in to follow this  
Peter Giljevic

RX7 return to idle trouble

Recommended Posts

Hello, I am posting up here as a last resort. I have had a constant/persistent problem with my 13B-REW engine running Siemens 87lb/hr primary injectors. Outlined below. See linked video. http://www.youtube.com/watch?v=FWMbeOQhL2U ^ Now no matter how any cell is set or those surrounding them the car always wants to on return to idle go lean (as shown in video) then it will catch on and go to the tuned or set fuel mixture. This problem happens to such a degree that the only way it is solved is by doing a stupidly rich fuel setting like 10.5:1 to counter the temporary lean stage/spot. I cant emphasis enough that all cells are tuned 100% correctly and when the car transitions through any one of them it operates ok. Its only on a trailing throttle as shown in video where the car wants to stall. When decel fuel cut is enabled the problem is 100 times worse and the engine will not fall back to an idle at all when decelerating and the clutch is depressed when coming to a stop. I need to add, I have tried the Link supplied resistors, I have also tried a peak and hold injector driver box from FJO. Both have same problem. After much discussion with my local distributor he told me to play around with the injector lag time values and by increasing these to +30% over normal it slightly improved the situation but it is still unacceptable as in the video. All fundamentals have been checked and can be viewed in video supplied, EGT front and rear rotor, fuel pressure, AFR ratio, you name it and double checked against different equipment. I am at a loss and need some explanation of what can cause this to happen. Oh and to add, does not matter if idle stepper motor is disconnected and idle speed set to virtually ANY rpm manually (even 2500rpm) the ECU still exhibits the exact same problem of temporarily going lean when trying to sit on the idle speed set point when returning from higher rpm............ as you can imagine it is very frustrating and confusing. Best Regards. Peter www.riceracing.com.au

Share this post


Link to post
Share on other sites
http://www.youtube.com/watch?v=dvYkkS-07mc ^ This is video of the car idling normally, has G4 plug in ECU, CDI ignition system forgot to mention in my last post. I just need to reiterated again, every cell above and below all around the various targets all set to a ratio tested from 11.5 to 13.0 and all permutations in between over days of testing made no difference at all! in the return to idle from higher revs be it in gear or a free rev (as in previous video). I would love to hear from ANY RX7 users who run a Link G4 plug in ECU and low impedance primary injectors! (just one!) :) I have changed the fuel injectors now to injector dynamics ID1000 (Bosch high impedance) so no BS resistors or drivers needed and I hope this will solve the very irritating problem, but obviously would like to hear from someone, anyone? who has a set up that works and can tell me that I am just hopeless. Thanks.

Share this post


Link to post
Share on other sites

Hi Peter.

Did you manage to get David to look at the .PCL file?  I would also be keen to take a look if you would like to email it our way.

I assume you are using 'Closed Loop' ISC?  If so, one thing to consider using Closed Loop is that it uses the open loop values as a reference, then adjusts toward idle speed target RPM's in the table.

The G4 can make excessive corrections to meet the target idle and cause hunting if Open Loop isn't tuned first.  Although I am sure you have done so, the fuel/ignition tables in these zones must also have been completed in regards to the tune.

Let me know if this has been covered or how you get on, and if you still want to send your map through to us, you can send it to tech@linkecu.com.  As a reference, be sure to add this link in to your email for us (http://www.linkecu.com/forum/forums/G4Forum/617287098).

Jurgen

Share this post


Link to post
Share on other sites

I have worked it out *finally* after going away for a 3 day tuning trip to other side of country I worked up some new maps while waiting in various air ports! In my cars case I had to do a combination tweak of the injector lag value, primary fuel cell *return cells in heavy vacume on trailing throttle 3000rpm to 1000rpm*, also added a 6th dimension to do a more complex air temp table based off TPS and RPM (required have no correction at values higher than 20 deg C AIT and 0.0% throttle, 0.5% is normal figures), And finally injection angle start point had to be modified to suit the location of my primary injectors which are all mounted on the intake manifold. If I get a chance will try to take a video and post it up so people can see the difference, turned out it could be solved but in no means was it easy.

Share this post


Link to post
Share on other sites

Further to my reply and my other post on the ECU cutting out at hot ambient & ECU case temperature this problem also occurs (even despite all of the doctored settings to get the ECU to function on return to idle). I can only repeat all AFR, EGT, timing etc is correct, something decides to make the ECU not work and in combination want to stall the engine. I have repeated this dozens of times over E-Mails to various people, Australian dealers, Link office manager and fuck knows who else (I have lost count)!@ To say *I am sick of it* is an understatement (given all of the shit I have had to endure let alone monetary costs for broken parts and my labor in testing time, rebuilding my car etc) of this and last centuries combined. I would love to have just one fucking person to talk to at Link a technical person, and have responsive turn around to problems I have faced and high lighted .......... would be great too If they could keep me happy as a customer and just send me out another ECU so I can test the thing myself rather than make me jump through hoops and waste even more time and make me even more angry!!!! given all of the shit I have had to endure since this saga began.

Share this post


Link to post
Share on other sites

Are you 100% sure that your injectors are not shutting off during overrun?  Large injectors can get to a point where the required pulse width gets so small that no fuel is delivered.  Check your pulse widths during overrun in the log file and see how short they get just before the lean area.  What you can get in effect is an overrun fuel cut even though the overrun fuel cut function is actually disabled.  In part this comes down to correct injector dead times but is also to do with other fuel delivery effects at short opening times.

Do the extra tables and settings you added end up providing more fueling during the overrun?

Not saying this is the problem but an area worth checking.  We have a S6 RX7 here that does not exhibit this problem and have never heard of it, so I am sure it can be tuned out.

Share this post


Link to post
Share on other sites

I have been about a white paper published by Mazda that said that rotary engines can not be run on the secondary injectors alone as it can cause return to idle problems.  If you are running no primary injectors or have moved the injectors further away from the ports, I would urge you to spend some time looking for this paper and see if what I was told is correct...

Share this post


Link to post
Share on other sites

Hey Dave, I did not get anything form you? I have solved the stalling, but there is always a BUT. Idle AFR cannot be set leaner than 11.7 to 11.9:1, no AIT correction can be applied on closed throttle, preceding cells (lower vac) need to be set richer than is ideal, and the other thing that helps is setting up another fuel multiplier table that does a delta -rpm increase in fueling in this transient condition on a closed throttle engine decel condition, and also a fuel temperature table is mandatory on a heat soaked engine (increase fueling as fuel temp goes up). Injection angle must be set at 50 BTDC after much trial and error. With all of these things activated the engine behaves properly in all conditions and does not stall with a 875rpm idle speed setting. The engine will idle with a 13.0:1 AFR setting but will NOT work on a closed throttle return to idle test condition and will NEVER work on a fuel cut condition with a return to fuel delivery of 2500rpm. Its just a peculiarity of this ECU I need to learn to live with, its not bad, just not ideal if you are trying to optimize every last aspect of the tune up... and something I have not experienced on other ECU types running the exact same combination of parts (injectors, injector location, engine specification etc). Best Regards. Peter

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  

×
×
  • Create New...