16v ECU raised rev limiter - pics inside

Discussion in '16-valve' started by barny, Oct 14, 2006.

  1. Rusty Dan Forum Member

    Joined:
    Jul 23, 2007
    Likes Received:
    0
    Good point, does it raise the peak torque level of the engine for optimum shifting?
    I cant see me needing 7800rpm in 5th on a 1/4 mile...
     
  2. websifus New Member

    Joined:
    Aug 3, 2010
    Likes Received:
    0
    Is there any possibility for a tuner to modify the ignition-map itself and optimizing it to the AFR an the overall set-up of the engine?

    The opinions in the international forums are confusing and contrasting.

    - Many quote, that you can indeed only shift the rev-limit. The ignition-map itself is said to be stored in a non accessible eprom inside the processor.

    - Some tuners offer "optimized chips" for the KR-ECU
    http://www.bar-tek-tuning.de/Chiptuning+chip+VW+16V+KR.htm

    - Others offer complete sets as 268-Inlet-cam, mdodification of WUR and modification of VEZ and TSZ-h. WUR, VEZ and ZSZ-h have to send to the tuner for specific modification
    http://www.slstuning.de/f/vw/golf-ii/23467-1-8-gt-16v-102kw/stufe-1/

    How gets the engine adapted to for example a set of 268-Schrick-Cams?
    The injection should suit for this extra 10bhp just by setting idle and CO.
    Further optimization could get obtained by WUR-Mod.
    But the ignition? Only by turning a bit the ignition distributor?

    Cheers!
     
  3. alexkod22 New Member

    Joined:
    Oct 30, 2012
    Likes Received:
    0
    I read all your posts(apreciate very much your sustained effort), I tryed everything and no good results. Changed the crystal in my 16v KE-Jetronic Knock Box with a 4500 Hz one and the rev limit is the same(around 7000 RPM), only change: the interval when it cuts fuel is shorter and it sounds more like fully electronic injection when hitting te rev limit. I also changed the crystal in the Oxygen Control Unit. It has 6000 stock and I tried 6150, no changes and a 4134.327 and the rev limit drops to around 5000 RPM. It won't go past 7k. The Knock box board is the green one so the nr.4 pin that is cut in the first pictures is for diagnostic and there is ni logical reson for doing that. Any idea?
     
  4. Nm8932 New Member

    Joined:
    Oct 6, 2015
    Likes Received:
    0
    Hi,
    newbie here looking to resurrect this old thread to try to gain some info on the kr Rev limit.
    Looked at the pics and ordered a 4.608mhz crystal as reqd but am confused by the pic showing the wire and the cut pin.
    Is this necessary to gain the extra rpm??
    Is the frequency of the crystal that alexkod22 used ineffective because it's the wrong frequency(I.E. Will only the 4.608mhz actually work?)
    I'll explain what I'm trying to achieve.
    I've got a kr on r1 carbs running pretty much stock everything with Newman 16v championship control cams.
    This is a race engine in its 1st phase of development and for phase 2 I want to flow the head and add the wildest cams I can whilst retaining the hydraulics(for cost reasons). Piper and Kent advertise the cams I'm after and quote a usable Rev range upto 7500rpm. This would suit the gearing on my car ideally as currently on the gearing I'm running it drops too low between gear changes, I've already got a different diff ratio ready to fit and if I can get the revs up I'll change 5th gear too.
    Already done all my sums and worked out max speeds in relevant gears and shift points etc I just need to get to 7500rpm whilst producing useable power.
    So back to the question, anyone out there got a working ecu with just the crystal change or is the wire mod also reqd?
    I have both types of ecu too do if anyone wants to chip in wether grey/white or green is best feel free.
    Sorry if this is dragging up ancient threads but it's something I want sorted in the next few weeks so I can get back on the rollers and get busy prepping the car for next season(this season finished at the weekend)
    Cheers in advance guys.
     
  5. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    3,298
    Location:
    Bracknell
    pretty sure the wire is due to some other issue, maybe to bypass a cut trace or whatever. just swapping the crystal is all you need to raise the rev limiter.

    squinting at the picture and diagram it may correspond to the spark trigger pin 12 which fires the TCI unit, or it could be pin 5 which is the ignition live feed to power up the ecu
     
  6. Nm8932 New Member

    Joined:
    Oct 6, 2015
    Likes Received:
    0
    That's exactly what I had hoped.
    Thanks.
    The new crystal should be here soon but it'll be a few weeks before I can get the cams and head done but I will post again when have results.
    I may buy another ecu as well and back to back the modified one and 2 standard ones to get an answer if white or green ecus actually make a difference.
    Also be interesting to see from the power curves what effect the crystal has over the whole rev range too.
    Not sure if this is particularly relevant now given the cost of mega jolt and similar systems but I'm keen not to have an exposed crank sensor as I've seen cars cut out in wet races recently due to water getting on crank sensors. Ultimately I'm willing to sacrifice a few ponies for reliability.
     
  7. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    3,298
    Location:
    Bracknell
    I did try both a grey and green ecu in mine and couldnt feel any difference, a rolling road might have picked something up I guess!
     
  8. Erik Christiansen New Member

    Joined:
    Apr 23, 2020
    Likes Received:
    2
    I know this is an old thread, but I wanted to post up some information a friend and I have recently figured out relating to modifying the rev limiter. This is based on my experience with a USA spec 1.8l 16v “PL” Oxygen Control Unit (ECU) and knock box. I don’t know if the KR fuel and ignition management used in Europe are the same, but if they are different it might explain why US and UK 16v seem to respond differently to the crystal swap.

    For PL engines, there is a rev limiter built into both the ECU and the knock box. They both kick in at ~7,200 rpm. The ECU rev limiter sends negative current to the Differential Pressure Regulator (DPR). This cuts fuel to the injectors in the same manner used for deceleration fuel shut-off above 1600rpm when the throttle is closed. Meanwhile, the knock box rev limiter functions by opening the ground to the fuel pump relay.

    To raise the rev limiter you need to defeat or modify the rev limiters built into both the ECU and knock box. As previously described in this thread, you can swap the stock 4.194304 Mhz crystal in the knock box with a higher frequency crystal, in order to effectively trick the knock box into a new rev limit = 7,200 * [(new crystal) / 4.194304]. I have a 4.433618 Mhz crystal installed right now for a rev limit of 7,611 rpm. This will stretch out the ignition map, possibly leading to some loss of mid-range torque, but I haven’t felt any seat of the pants difference. When I get a chance I plan to dyno both stock and modified knock boxes back to back.

    The ECU rev limiter is a bit trickier to get around. I haven’t even attempted to modify the ECU itself so I don’t know if that is possible. But, a friend of mine built an add-on “Power Module” that over-rides the DPR current when the full throttle (WOT) switch is closed. It uses an Arduino to do closed loop feedback control of DPR current using the analog signal from an AFR meter (MTX-L Plus) connected to a wideband oxygen sensor. The primary purpose of the power module is to eliminate lean conditions at high rpm, but it also conveniently lets us raise the rev limiter by simply replacing the crystal in the knock box. The module only functions at WOT, so the rev limit is still 7,200rpm at part throttle, but I’m not concerned about part throttle operation between 7,200 – 7,600 rpm.

    I’m curious if anyone knows if the KR ECU also has a rev limiter built in?

    Also, I still do not understand what the jumper wire is for in the pics in the original post on this thread. Has anyone figured that out?

    I hope this information is helpful. I learned a lot from this thread!
     
    Toyotec and Sirguydo like this.
  9. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

    Joined:
    Jul 26, 2006
    Likes Received:
    3,320
    Location:
    Creating Pfredstarke
    Glad you were able to build on the information shared.

    Thanks for your update.
     
  10. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    3,298
    Location:
    Bracknell
    the KR ecu is doing the same job as the PL knock box, handing the ignition side of things just without a knock sensor attached so this is why the solution is the same :)

    other than that there is no ecu for the fuel system as its purely mechanical but with the addition of a controller for the ISV instead of the AAV found in earlier 8v.

    dont think anyone figured out what that wire was for, certainly isnt there in the other modified ecu which was posted up so it may just be to fix some other issue inside that cropped up in the past
     
  11. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

    Joined:
    Jul 26, 2006
    Likes Received:
    3,320
    Location:
    Creating Pfredstarke
    PL has closed loop lambda control as was used in countries like Germany and North America. It is a pollution controlled engine, like a 9A, 6A and ACE.
    While it was produced alongside the KR, I am not sure what was carry over for electronics.
    UK did not get them.
     
  12. Martin 16v Forum Member

    Joined:
    Aug 19, 2018
    Likes Received:
    10
    Having recently had my mk2 on the rollers where it showed peak power at 6743rpm (172bhp and 146lbft)
    I was running through some advance timing checks before setting the cams up.

    I replaced the 4.608 crystal back to the OEM type after which i noted that the advance timing at 4000rpm was down by 5degrees.

    Thinking about it even though its great that there is a way to raise the limit if required but is it doing more harm than good?

    To trick the ecu to think the engine is at 7200 when in reality its next door to 8k will be having an effect on the whole timing map.

    It would be interesting but not really cost effective to have a raised rev limit ecu and a standard ecu run back to back on the same car same day same rollers situation, to see what actual effect it has on the remaining area of the timing map and not just the max limit.
     
  13. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

    Joined:
    Jul 26, 2006
    Likes Received:
    3,320
    Location:
    Creating Pfredstarke
    I saw your post on FB and commented.


    Thing is on that Stealth plot, irrespective of the numbers generated for a 1.9 16v, your cylinder fill ( as indicated by the torque) is dropping rapidly after 6600 rpm, so there is not point revving the engine to 8k. 7000 rpm is plenty.

    Trackcab16v had that done the crystal done on his cabby 16v back in the day. When I tested that car, it would become quite vocal at 7500 rpm. However he had big compression, his own ported head, cams and a 2.1 engine. So significantly different to yours.

    I asked the question about what a standard KR is tested at on that dyno to get a gauge where your car really stood in that database. I believe it is around 160 to 170 bhp at whatever rpm with WUR mod.
    Dyno's do not read the same and certainly not that one.
    I once had a Kjet ABF tuned by me put on that dyno and it read something like 186 bhp@ 6900 rpm! And that car was not anything as fast as the ABF MS cars I owned and tuned on this forum!
     
    Martin 16v likes this.
  14. Martin 16v Forum Member

    Joined:
    Aug 19, 2018
    Likes Received:
    10
    Agree with what your saying and I'll be getting it on another dyno as soon as i can out of pure inquisitiveness, i mean the car really shifts along which is the main thing.

    On the flip side does replacing the crystal alter the entire ignition advance and other respective ignition tables?

    Obviously this is very old technology compared to todays market but it would be good to know if it is just having the desired effect (rev limit)
     
    Toyotec likes this.
  15. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

    Joined:
    Jul 26, 2006
    Likes Received:
    3,320
    Location:
    Creating Pfredstarke
    When I used to tune stock KR K-Jet cars, I could accelerate to 60 mph in 7.2 secs when finished.
    ABF on KJet 6.6 secs, and my own MS ABF car at the time 6.2 secs.

    That for me and others was the real test and dyno stuff was really for entertainment, if we were not doing a study.
     
    Martin 16v likes this.
  16. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

    Joined:
    Jul 26, 2006
    Likes Received:
    3,320
    Location:
    Creating Pfredstarke
    The timing at the top end of the rev range and at 100kPa, which ends at the original rev limit of 6800 rpm, does not really change in the factory ECU.
    Hence why changing the clock frequency, does not have any unsafe effects on timing.

    You can confirm what the torque shape looks like, by testing the car in gear on a flat surface with an accelerometer in say 3rd gear. That is one of the first checks to know if dyno is picking up and displaying the vehicle's wheel force correctly or has the inertia/ramp rate set incorrectly.
    This post is a good read. It will give enlightenment what to look for, when you test the car next.
    Some of the tests you can repeat yourself, without a dyno.

    https://clubgti.com/forums/index.ph...-plots-parts-1-and-2-von-toyotecwerke.235714/
     
    Martin 16v likes this.
  17. Martin 16v Forum Member

    Joined:
    Aug 19, 2018
    Likes Received:
    10
    Good info but i think were missing the point, its not the rolling road side of things to be focusing on its confirming what the crystal is actually doing to the entire ignition advance.

    If the crystal from what i have found by testing is adding 5 degrees advance BTDC what effect is that having on how the given engine set up works.

    We know its a given that having a extra 5 degree BTDC will shift the point of combustion away from where we want it.
     
    Last edited: Jan 17, 2022
  18. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

    Joined:
    Jul 26, 2006
    Likes Received:
    3,320
    Location:
    Creating Pfredstarke
    Yes I am guilty of drumming on. Sorry!

    I am using the rolling trace at that specific facility to understand what is going on with engine torque profile, if that torque profile is what I expect and how is it is affected by cylinder fill, lambda set point and spark energy. Assuming the latter is the only change, via ECU clock frequency.
    I am also trying to match that up with a known vehicle characteristic I am used to, hence wanting to see the plot from a stock KR car on that same dyno.

    Because I have reservations how the the acceleration or performance of the vehicle was captured, it is difficult to know, what benefits there are from hardware modifications, or if your spark setpoint because of the clock change, is achieving MBT everywhere, which it would not be.

    How am I so confident? Because I also know the map settings in a KR ignition ECU, and I know where I would change to benefit engine torque.
    Problem is I can get a global 5 deg shift just by turning the dizzy. I just will be limited to 6800 rpm or so. This is not a problem on an engine that does not need to rev past that.
    With the ignition ECU modification you did, if the dizzy is referenced at factory settings, at full load and 6800 rpm, you will be at 26 deg adv + 5 from stretching the cpu clock and around 29 degs in the areas where maximum torque is made, which on a dizzy KR car from experience, does wake it up at those loads. But it is not an ideal spark profile.
    There are no breakpoints after 6800 rpm which is your soft cut. So by having no rev limit, your ignition remains fixed at 31 deg Adv, to the 7800+ rpm.
    Again, while it might will be safe, pending a det can check, is not ideal if the engine had high cylinder fill past 6800 rpm, which yours, even with that test, suggests cylinder fill is rapidly falling off and the operator lifted.

    Unfortunately, the timing table is just for a factory KR, not a modified 1.9 16v. I have used the Kjet ignition system on a ABF engine and it is a compromise to set the low speed right without kick back from the starter when starting, and the top end performance optimum as there is more limitations due to knock.
    Being able to tune the settings for the entire operating engine envelope is what you want for a really responsive engine any where. That is the sort of task achieved when we fitted SEMs to ABF engines and unlocked all the performance from stock hardware.

    KR ECU ignition map below.

    [​IMG]
     
  19. Martin 16v Forum Member

    Joined:
    Aug 19, 2018
    Likes Received:
    10
    Interesting, so what ever the set advance is at 6800rpm say 30deg for the next 1000rpm or so it stays at 30deg which like you say isnt ideal.
     
  20. Martin 16v Forum Member

    Joined:
    Aug 19, 2018
    Likes Received:
    10
    Heres a plot of a standard KR vs mine
     

    Attached Files:

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice