Will someone tell me if they see where and why this 1.4t is back firing on the let off. It may be there but I don't see it. I thought it might be the spark plugs but there isn't any miss fires under acceleration.
2019 off road buggy vats tcs.hpt
first tune new settings.Channels.xml
I new I had a real problem but I thought someone might be able to spot it.
Can't check your tune cause my laptop with the hpt software can't connect to internet right now, but DFCO is probably your problem. Disable clutch and decelleration fuel cut off and see if it solves this.
A solid tune shouldn't have a backfire. While I was tuning I had a real bad one. Disabling DFCO completely got rid of it.
Get your injectors, MAF and VVE tuning right and it shouldn't happen.
That sounds good, do I disable ECT, RPM, vehicle speed or just extreme cutoff. I'm not trying to sound stupid but I just don't know. I haven't touched injectors, MAF, or VVE yet and I am not sure how to without screwing something up. If you could push me in the right direction I can go ahead from there.
Last edited by carotene; 06-25-2022 at 05:07 PM.
Naw bro there are no stupid questions when it comes to this ECM lol. I am still learning too, but I do know about this issue, because my sonic had major backfire with the DFCO enabled too. The extreme cut off is fine to leave on to your liking, it's just a fail safe that I set higher then I think I will reach, so mine is at 7,300 where as I shift around 6,800. The cut off your after is mainly the clutch and deceleration. Just Disable them on all accounts (ECT, RMP, and speed) any one will do but I just do all of them for posterity. Should clear it right up. A lot of tuners disable these as a standard.
Thanks I will do that and give it a try in the AM. It's raining right now with lots of wind, I don't really want to get wet after all it is an off road buggy no windows.
Off subject a little have you set your throttle pressure drop to 0 across the table? I have tried it but mine doesn't run well at all at 0, throttle pressure drop min is 1.5 for me with 40 across the table. It screams at that setting all the way to 6500. If I take it higher or lower on TPD or the table it gradually slows to the point of no reaction at all when I push on the pedal. I can't figure out why.
Last edited by carotene; 06-25-2022 at 07:00 PM.
I really haven't messed with that yet, still getting my base tune down. It has to do with how fast the throttle opens to balance the pressure from the inlet air pressure to the manifold air pressure.
The help file says this.....
Turbocharger Boost
In this section we'll see how the turbocharger boost is controlled. The main control parameter for the turbocharger boost control is the Desired MAP which is calculated in the throttle control. This is the MAP that will achieve the desired torque. The thing to remember is that typically, the MAP is measured in the manifold, the boost is generated at the turbocharger and TIAP is measured at the throttle inlet after the intercooler.
The first step in the process is to work out a desired boost, in this case it's actually a desired TIAP becuase this is where the measurement takes place. Since the Desired MAP has already been calculated, the only parameter to adjust here is the Desired Throttle Pressure Drop. This value adds to the Desired MAP as a way of adding a boost reserve to provide a more sporty feel. Typically, it is calibrated to zero to give the best fuel economy.
I will be going thru that again. I'll just keep at it till it breaks or runs better.
Last edited by carotene; 06-26-2022 at 08:29 PM.
What kinds of mods does the engine have? And can you please supply a log file which contains the accelerator pedal position, the throttle actuator position, intake cam angle, exhaust cam angle, injector duration and spark values and possibly highlight regions where the bangs happened?
Looking at the tune file, the driver demand tables look a little off. As far as i am aware, the negative numbers are meant to represent engine braking of sorts. Here's a comparison between mine and yours.
I am assuming because your values are closer to 0, the throttle blade may not close completely when you let off the accelerator pedal and shift gears.
For pops and bangs there needs to be a certain percentage of air, besides fuel, in the cylinders to happen. You could try increasing the negative values. Maybe even limit the base and long term minimum spark values in the regions where the bangs happen.
mytable.png
yourtable.png
Whoa that's a huge difference! Haha. Mine is just the stock driver demand map with like 10% multiplied on the 90% and 100% rows. I think my table is adequate for my application as it's a daily driver and needs a high drivability factor so the negatives make it so I can use the engine to decell. In a nutshell my mods are cam/valve springs/ported heads/50% larger turbo/42 lb. Injectors. I'll update my profile with all my mods though. You do have me thinking about my DD map though now, I see the concept yours is after. Interesting
Simplyjesse; I disabled DFCO like you suggested and it worked great to eliminate the backfire on let off, Thanks. I checked out Goat Rope Garage concerning speed density and MAF cal.. I retarded my timing and eliminated some other things, man what a difference it made. I now have a serious problem on the let off. It smokes real bad after a hard pull. It is a short lived action but there is a lot of oil getting burned. I have already changed the BOV and the wastegate actuator. They were replaced with after market pieces. They seem to be operating fine but I can't figure why it acts this way. PCV has been done and manifold has been ported. It is building way to much pressure in the crankcase, any ideas anybody.
The valvecover has been replaced too.
sbarisic; No engine mods but it does have a new intercooler and exhaust no cat and very short. It is an automatic not standard. I haven't touched the DD table it is stock. I won't be touching it either, did that once bad news not again.
Last edited by carotene; 06-27-2022 at 05:38 PM.
Well, mine is a stock driver demand map with the 90 and 100% throttle part increased by a certain percentage. It's a 2019 manual 6 speed M32 transmission Opel Corsa 1.4T, compared to the US 1.4T versions this seems to be a port injection variant without the fuel pump control module and fixed fuel pressure, besides some other minor tune differences.Originally Posted by Simplyjesse
I am actually looking for some sort of anti lag when i let off the throttle, but i can't seem to get it to work. I clamped all negative values in these tables to 1 and i'm going to test them soon, maybe it'll work.
that is what that pressure drop table is for, it keeps the turbo pressure up on the pre throttle side during shifts, or that is what its ment to be used for as mentioned in the other thread, post #13 https://forum.hptuners.com/showthrea...088#post691088 but keep it open too much and it may cause long term dramas by the sounds
Ok that's great that the backfire is gone. Sounds like you have the exact problem I have had with smoke on throttle let off. I'm tuning my VVE now hoping it has something to do with it, and I dialled back my boost until I figure it out. I am also concerned about the exact same thing, it's a grey smoke on let off after a WOT pull. It is worse if I lean the PE to .8 Eq or so, and not as bad if it's richer around .75 but still there. My VVE was way off though so I'm street running now to get it in line. I'll get some info up as soon as I get off work.
I did some testing today
a.png
b.png
Setting the minimal pressure drop to 14 kPa, and filling the rest of the table to 40 kPa just resulted in this. The throttle blade partially closed at wide open throttle. When letting go of the accelerator pedal, the results were identical.
The only thing that seems to make a difference is clamping the base and long term minimal spark to -30 deg, which results in a single pop when letting of the throttle and shifting into neutral at high revs.
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Figured out my smoke problem I believe. The one way check valve feeding the pcv system from my turbo intake was stuck open, causing a vacuum leak I believe. Ordered an air injection check valve to put inline with the hose as this is my 3rd OE valve to break, I'm going with something a little more resilient. Hopefully this fixes my issue. Unfortunately I now have to redo my VVE and MAF, explains a lot actually. Misfire, smoke, crazy VVE readings........ FML
Simplyjesse; I hope you got it fixed that way. I found out with mine that the excess pressure from the turbo is getting into my crankcase. I'm not sure how yet, I did a compression test 148 to 155. that is normal for my engine. The oil is coming back into the turbo from the crank drain. When I let off from a hard pull there is a slight time delay till it burns the oil being pushed back into the turbo and then the intake. It is very short but it is there, maybe 1/2 second or less. I pulled apart my intake from the turbo to the manifold. There was oil in the system maybe 1 or 2 oz.. I cleaned it and took it out for a run. When I got back there was oil in the tubing from the turbo to the intercooler, not much but I only did 1 pull to check it out.
I am going to reduce my settings for the boost so as not to destroy my engine. I will sometime in the future correct this but for now I don't need the extra boost.
Sounds like the same thing. Mine is still doing it to a small degree as well after I changed the check valve at the compressor. I also turned the boost down. Definately needs a PCV work around, the pcv v3 fix isn't working right. Keep us posted on what you find, I'll do the same.
I found my problem, the check valve at the turbo was stuck closed. I found another one and changed it out problem solved. I put my pcv at the original hole for the breather tube in the intake that ran to the turbo then ran that hose to the spacer plate behind the throttle body. I bought the adapter for the oil fill cap and ran it to a catch can then to the turbo. I think it works better this way. I hooked up a pressure gauge to the crankcase and got it down to 2 to 5 psi at full boost. I don't know what they should be but that is really good for a boosted 4 banger. I used to drag race and we used a BBC for power. We had a crank driven pump on it to reduce crank pressure. It worked well enough to get negative pressure, but it was a naturally asperated engine. It would be a waste of time to do the same to these little engines it would cost to much of a power loss for what little it would gain.
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