Somebody with an upgraded cam suddenly complaining about fuel smell at idle, is it true that by playing with the EOIT or SOIT They can help clean up some of that smell?
Somebody with an upgraded cam suddenly complaining about fuel smell at idle, is it true that by playing with the EOIT or SOIT They can help clean up some of that smell?
Doesn't make much difference on a DI motor since fuels already injected straight into the combustion chamber. Best thing is to get idle timing up via the torque model to something around 20 degrees.
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So the factory injection timing isn't going to spray during an open exhaust valve event on any DI Engine?
Why do I find threads like this, these are wrong?
https://forum.hptuners.com/showthrea...l=1#post624400
https://forum.hptuners.com/showthrea...l=1#post717264You'd certainly be able to clean up the raw fuel smell by optimizing EOI on a modified engine
ave you looked into your injection timing tables? Mine was off after I put my cam in so bad i would get dizzy idling at a stop light. I'm slowly working on adjusting small increments at a time since i'm trying to street tune until i can get dyno time.
Sure it "might" help it a touch, but usually at idle you're spraying fuel solely on the compression stroke and it's high pressure fuel at that. Problem is most cammed motors will idle with low ignition timing after the mods are done and need the torque model reshaping. I've shifted soi up to 40some degrees each way to no avail with these. It's better to lower it a little, but timing will be where most of the cleanup is at.
2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80
~Greg Huggins~
Remote Tuning Available at gh[email protected]
Mobile Tuning Available for North Georgia and WNC
Okay thanks, GHuggins, I asked because I want to help other people with suggestions about DI engines but I don't tune DI engines. I Always assumed they sprayed more towards compression but during my research I found those threads which seemed to indicate the spray was occurring much earlier. Nevertheless I thought it would help because of my experience with traditional engines.
But I trust your input and I will tell people from now on that, EOIT and SOIT will make very little difference in fuel smell on DI engines. One day I will play with it myself but for now I will use your advice as golden rule so people don't waste time trying to adjust these things.
That one thread was where a guy was complaining about the smell on a stock engine with cat deletes just for reference and it still had a bad smell
I could be completely wrong and maybe shifting it WAY out there does make a difference and I just haven't discovered it yet.
2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80
~Greg Huggins~
Remote Tuning Available at gh[email protected]
Mobile Tuning Available for North Georgia and WNC
People parrot things on they heard on the internet all the time.. I've never saw a meaningful difference.Originally Posted by kingtal0n
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Is it safe to say that most (any mftr) factory tuned DI engines are sending fuel while intake valve is closed then? That is kinda what I always thought of them as doing for idle cruise stuff
and the window just opens up for wot as needed- right? and as the tuner has control over boundary for when this happens (it can overlap with evc if needed?)
Obviously it depends on the camshaft and how much overlap it has and when the overlap occurs in reference to TDC. Intake valve opening isn't what causes the smell, it's the exhaust valve close event which occurs just after TDC or around 360-320 SOI area. So if you have a camshaft with more overlap in that area you can delay start of injection so that the exhaust valve is closed prior to fuel injection which "should" help with any fuel smell.
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Hey thanks,
What I'm asking is, intake valve close is wayyyyy after EVC. And idle/cruise pulses are very very short. Therefore, if the default for most DI engines is to spray post IVC then it would be sooo far from EVC that the pulse would never 'reach' the EVC no matter how large a cam gets. And here is where I am sensing conflicting information- you are suggesting that some camshafts overlap with the DI injection because they have longer duration EVC events. This would imply that DI injection occurs just after EVC on a stock engine, and long duration cam can 'overlap' with the DI spray. And this is the source of my confusion in a general sense- It was my understanding (and implied by Ghuggins "during compression event") That the DI Injection occurs near or after the IVC (Intake valve close) which is what- roughly 180 degrees after EVC, and therefore has no chance of overlapping with the DI spray no matter how large the cam gets,
I have an LFX (V6 with the E39A ECU) and is the only thing I've ever tuned, and am still a total novice, but...
In the case of the E39A you control SOI, not EOI, and SOI is set via the SOI Base table (Engine > Fuel > General). The numbers in the table are when injection starts in degrees BTDC (before TDC of compression stroke). There are also two tables to adjust SOI based on engine coolant temp: SOI ECT Offset and SOI ECT Offset Mult which add to the SOI Base table. Believe the way they work is the ECT Offset is multiplied by the ECT Offset Mult table, and this number (negative) is subtracted from the base table, thus increasing (advancing) SOI.
When I installed the Mace cams I was getting a very lean cold start (WB showing ~1.10 with commanded of ~0.80) and also some popping out the exhaust, and by reducing the ECT Offset table (smaller negative numbers, closer to 0) the cold starts were less lean and no more popping. EVC with these cams is about 26 ATDC, so reducing the offset table put the overall SOI to after this (base - offset = ~334, right at/just after EVC). FYI also had to increase the injector pulse widths via the Offset > Temperature Adder table (General tab) to further richen my cold start.
I imagine with a big enough cam/late enough EVC you may have to adjust the base table, if even setting the offset table to 0 isn't enough (SOI before EVC even when engine is warm).
I also have a Boundary table which states "the latest possible crank angle that the injection pulse can finish for fuel to be delivered to the cylinder", which to me sounds like an EOI setting, although the stock values made no sense at all (like EOI BTDC of exhaust stroke, not compression, at high RPMs), and I tried setting all values to 512 which I believe is the highest you can go, but in either case I didn't notice and difference to fueling, AFR, etc. Thinking that table isn't even used, at least on the E39A.
There is a lot of misinformation on the internet.
Last edited by TriPinTaZ; 03-10-2023 at 09:12 AM.
You never WANT to spray through an exhaust open event but it does happen sometimes under full throttle where you start spraying as the exhaust valve is almost closed. With the velocity in the chamber this isn't much of an issue at high speeds. It is not wanted or desired at idle and low speeds.
I Just want to give good information for people modding their engines. If somebody installs a cam and has some issue with respect to fuel smell or engine behavior, the answer seems like it could be SOI or EOI related at this point, based on the variety of responses and limited reading, it seems like something that needs attention.
If I understand, your engine had some difficult until you retarded the SOI by pushing it a bit later.
Does that sound right?
I had a moment to read this paper
https://www.jstor.org/stable/44730720
The variability of chamber design is apparently a large part of the subsequent tuning efforts. In their attempts to reduce soot production and improve cylinder cooling and fuel economy, earlier injection was desirable but it needed to be directed towards the piston while the intake valve is open and the shape of the chamber needs to prevent high density fuel from occluding the spark plug while still allowing the spray to vaporize. I am unfamiliar with the design of Chevrolet DI engines so I cannot draw any similitude. I look forward to any more experience as this is not my job or field, it is merely a hobby and I use whatever I learn to help whoever I can in my spare time. I'd like to provide accurate information, thanks.
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In my case, due to the extra duration of the new cams the injection started while the exhaust valve was still open, creating pops/bangs and a lean AFR on a cold start. So yes, retarding the SOI (via the ECT Offset table, since it was only an issue when cold) so that injection started at/after EVC fixed my issue. With that said, I didn't notice a fuel smell in my case, but the injection was only too early for the first few minutes, after which the offset tables were no longer interfering. Once you know when EVC is you can compare that to the SOI base and offset tables and make sure you're not injecting while the exhaust valve is still open.
When is your EVC (completely closed, 0.000" lift)? If it's 30 degrees ATDC, for example, you'll need to make sure SOI is 330 at the earliest. If the SOI Base table is greater than 330 anywhere you'll want to cap it at 330.
Another consideration is VVT if you have it. In my case (LFX) the exhaust cam starts at the home position and any adjustment made retards the cam, so wherever it's set to 10 degrees retard, for example, the SOI cap would then become 320 (in this example).
Another thing to note is injector dwell time (how long it takes the injector to open completely). I'm assuming the SOI Base table does not take into account dwell time, and if that's the case you could advance the SOI in any given cell by the dwell time. I bring this up mainly because at higher RPM's, if your SOI is limited to 320, for example, at say 6000 RPM that might not give you much time to inject, but if the dwell time is, say, 0.3 ms (I believe that's what the LFX is), that's 10.8 degrees at 6000 RPM, so you could then set SOI to 320 + 10.8 = 330.8.
And if that's still not enough time, you can possibly increase the fuel pressure some to inject the fuel quicker. Just be aware of the max pressure/pressure relief of the fuel pump/system. In the case of the LFX, the highest commanded pressure is 15 MPa (2175 PSI) but the scanner sees up to nearly 16 MPa, and the relief is at 17.5 MPa, so in my case I wouldn't want to increase pressure much, maybe 0.5 MPa at most.
I also found this while edumucating myself on the subject: https://www.frontiersin.org/articles...22.823386/full. Perhaps not relevant to this particular subject, but interesting nonetheless.
Thank you this is very helpful. So the aspect of injection phase is just as important if not more important in the DI engines as it is in a port application. In port you may have an injector duty of 100% for example and phase goes right out the window, but I see that in a DI engine this may not be possible or feasible so the timing is critical with respect to window of opportunity and desired outcome.
It sounds like from what you are telling me from your experience is that the DI Injection for idle while cold (low pulse supply) is very close to exhaust valve close event, and that by simply installing a slightly longer duration camshaft you can overstep the boundary of EVC and wind up with a poor running engine while cold. I wonder how far it moves when the engine is fully warm? I did not see your comment with that respect. I never looked at a file but I suppose one of these days I'll need to out of curiosity. It is merely curiosity and the goal is only feed good information back into the machine. Thanks for your hints and discussion I think I can figure it out based on what you said so far.
Here's a good discussion that I just read yesterday: https://forum.hptuners.com/showthrea...tting-EOI-drop. Long story short: set SOI such that EOI is no later than (or very minimally after) 180 degrees BTDC (i.e. piston at BDC, starting compression stroke). So you want to start injection no earlier than EVC, and have injection finish no later than 180 BTDC.
As for when to start injection, not sure if I've found anything definitive yet, but in theory I believe you'd want the injection happening when piston velocity is at its greatest, which I imagine is when air velocity is at its greatest, to give the most optimal atomization. Assuming this is the case, I would figure out when your pistons are moving the fastest (see my thread here for more details as well, particularly post #4: https://forum.hptuners.com/showthrea...tor-Dwell-Time - thanks to tunerpro for their input!) and then adjust SOI around this, taking into account pulse width, VVT, dwell time, etc. With all this said, I haven't adjusted my SOI yet from stock except where needed (to start at/after EVC) as I'm still playing with the VVT settings, but once I'm done there I'll play with the SOI and see if I notice anything different (although I'm guessing I'll need a dyno to really see anything as my theorized numbers aren't too far off the factory base table).
And yes, it seems that when the engine is cold the SOI needs to be early, closer to EVC, at least in my minimal experience (also discussed this a bit in my thread).
thats what i did and it worked great,i just makes sense if you delay your soi until overlap is complete in the idle area it will get rid of the eye burning fuel smell.///// 2021 ss1le btr 220 cam ,catless SS exhaust,msd intake,k&n blackhawk cai,speed engineering LTH
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