Hi, I just sent out my ECU to be reflashed by technosquare, as part of the performance parts I had installed on my car I put Crawford High flow cats, I ordered them on monday and was hoping I would receive them before I received my ECU. unfortunaly the supplier who has them says they are currently on back order. heres my question, would running my reflashed ECU without the high flow cats hurt the car or do anything to damage it? at the most the car would only run this way for a week or 2. what do you think?
Thanks for the input, Jim

 

bump

 

I'm thinking, if anything, you would be running richer with the HFC flash w/o the HFC's on. I'm sure you will be fine. If you're worried though, just take it easy for those two weeks.

 

ok thanks!

 

I disagree. HFCs shouldn't make you run richer/leaner. CATs don't dictate your fueling. Your ECU dictates your fueling. If you were to remove the CATs and trigger the CEL, ECU can alter the fueling as a result of that change but since the OP is getting a reflash, I am pretty sure the rear O2 CEL code will be disabled.

I assume the OP will be running with stock CATs in place vs. HFC. Should be fine. Stockers will produce more backpressure in the exhaust which can raise the EGTs. If you're tuned on the bleeding edge, that can result in detonation but I doubt that will be the case here. These reflashes have some margins to accomodate variances like this and the ECU has safeguards to protect the engine. Just drive the car and when the CATs come in, drop them in. Should be fine.

 

[QUOTE=Ziggyrama]I disagree. HFCs shouldn't make you run richer/leaner. CATs don't dictate your fueling. Your ECU dictates your fueling. If you were to remove the CATs and trigger the CEL, ECU can alter the fueling as a result of that change but since the OP is getting a reflash, I am pretty sure the rear O2 CEL code will be disabled.
QUOTE]

Your AFR will most definantly change with the change of any breathing mod. And your right that the cats themselves wont dictate fuel, but the readings the sensors are telling your cars ecu WILL change thus causing the ECU to adjust. I have seen this first hand. Granted i did not have a reflash, i was running a UTEC with tuner wideband and when i went from stock cats to test pipes with non fouler plugs on the 02 sensors my afr went lean with no change in tune. About a month later I took the test pipes off and replaced them with crawford HFC's my AFR became slightly richer than with the test pipes but was still leaner than with stock cats.
I'm not really sure what you mean by disabling the CEL but a reflash wont make your ECU not throw a code. Also I do not believe any of the current aftermarket HFC's will throw a CEL, only test pipes not running nonfouler plugs will.

EDIT* for the OP, As long as your still N/A your going to be safe with the reflash and stock cats. you will just not be making the most of your tune. worst case senario is the ecu adjusts timing and you lose a little bit of power.

 

[QUOTE=armt350z]I guess I have to know more about your previous set up and how you measured your AFR, what sensor you used, where it was placed and what was used to interpret the sensor readings. I found that majority of people that do this themselves usually have something wrong in the whole equation. Enough people do this and the forum starts to believe in things that make no sense. Other people come along, read it and perpetuate the cycle. Accuracy is extremely important so getting it right is critical. If you don't, the results will be tainted and may suggest things that don't make sense.

Generally, breathing can alter your A/F calibration but it depends on many things. Usually, exhaust has little impact on the AFR because AFR adjustments are done on the intake side along with O2 feedback on the exhaust side, in closed loop. Changing intake can alter AFR readings if the diameter of the intake tube changes and you're using MAF for air metering. If you're tuning in open loop, and most people do, the O2 feedback is ignored. So, ask yourself, what dictates your fueling? It's the amount of air entering the engine. What tells the ECU that? In the case of stock Z, the MAF sensor. Based on the flow of air, ECU calculates the injector pulse width which basically specifies how much fuel to add. The calculation is based on a map stored inside the ECU, burnt in the ROM that tells it that based on load X and RPM Y, use IPW of Z. So, you take mroe air in, which produces more load, which will tell ECU to jump to another cell on the map and that's how the AFR 'magic' happens. So, where does the HFC come into this equation? It doesn't...at least not in normal operation. ECU doesn't magically adjust things for no reason. Why would it change the AFR if the CAT has no effect on the actual fueling? The only time that can happen is if the ECU has a CAT safeguard and decides that the state of the system may cause the CAT to fail. I've seen instances where if the rear O2 sensor is removed, the ECU goes into an auto enrichment mode for safety. That doesn't fall in line of what you saw but you're basing your statement on observation that involves lots of variables. So, you have to examine what changes you did, and how you were measuring the parameters:

1. Where was your wideband located?
2. How often was it calibrated?
3. What readings did it produce in closed loop?
4. How did you synch WBO2 output with your load readings?
5. If you used some kind of 3rd party integration tool to put all these together, how trustworthy is this tool?

To give you an analogy, I had beans for dinner and the next day I went down to a shop to get some dyno pulls. I recorded AFR X on my forst dyno pull. Between pulls, I started to fart up a storm. We did some more pulls and my AFR was Y now. Well, as far as I know, nothing changed except I farted between the pull. So, I guess I can say eating beans the night before dyno pulls will change your AFR. It SEEMS to make sense.....but in reality they are not related. From a stand point of an observer that has limited knowledge on the subject, that would be the conclusion I'm not implying you have limited knowledge since I don't know you....just generally speaking.

 

I'm not going to dispute what you have said but I'll just state what my experience was when upgrading to a TestPipe. I had Stock Cat for about 9 months with my Rear-Mount Turbo and after switching to a TestPipes, my tuner had to add at least 2% more fuel just to get me back to safety. Before the swap I only have added 7% correction on IAT 1-10C but when I went back to my map, my tuner had it to 9% plus he also added some more fuel on the 10%-50% column. This lead me to believe that the TestPipe did lean my A/F, just my .02. Oh, he also added an Oil Catch Can so maybe that was the culprit..J/K.

 

In response to your question my setup was this:
1. I was using a bosch sensor with the bung wielded in about an inch before my drivers side cat.
2. It's been in the car less than 8 months and has showed no degredation from its initial install when checked against a clip in sensor that i put on while I was dynoing during tuning. the clip in has constsistantly read slightly leaner. the last time its been on tjhe dyno was last month with the same difference.
3. Closed loop... you got me there i'm only running open loop with my UTEC with the exception of at idle.
4. I'm using the utec tuner to integrate the afr readings.
5. there has been no bean eatingat the time of any of the logging

 

Sounds like you had a good setup and you were measuring at the right place. I assume UTEC has been proven to be fairly reliable and accurate when interpreting the WBO2 signal so we can assume that is good. I mentioned closed loop readings because it's a good way to verify how accurate your WBO2 really is. At idle, you should record fairly steady 14.7:1 AFR because that's what the ECU will target as stoich mix. If your WBO2 is telling you 14.0:1, yeah, you may have to look into the accuracy of that sensor. I like to establish these checks before I get into tuning and start relying on instruments and bank the health of my engine on them. You know what I mean? UTEC, like all other software has bugs. It's just a matter of hwo severe they are and if you will see them.

I thought about what you posted and it didn't add up to me. How can ECU alter IPW in open loop if it doesn't even take measurements that could be remotely associated with presence of a CAT? After all, the ECU ditches O2 feedback altogether when in open loop and further more, rear O2 is not used for fueling anyways. So, what gives? You see it but it makes no sense. Well....I thought about it some more and concluded that there's something else in the equation that hasn't been considered. I can offer 2 things in that regard:

1. Valve overlap combined with improved scavenging effect is introducing extra oxygen in the exhaust. It actually makes sense. Think about how the valves are oriented in the engine. Exhaust and intake valves sit fairly close to eachother. on NA cars, cams are set up to overlap exhaust and intake valves to some extent to maximize the scavenging effect to improve VE during the intake stroke. That means that intake and exhaust valves are both open at for some time. Consider why test pipes make such a big improvement in the car. They greatly improve the flow of the exhaust which will effectively increase the scavenging effect in the chamber which is what gives you the HP increase because you're getting more air in the chamber now which is really that it comes down to when making power. It's possible that adding test pipes introduces more oxygen in the exhaust from the intake stream when the valves are both open. You get some more in the wash which would definitely record as leaner mix on your WBO2. And since they sit so close together, it probably always happened but but now that you improved that cycle, it happens more. Here's a question....after the test pipes went in, did you experience severe detonation because of the perceived lean-out?

2. This falls back on #1 concept. Because of the improved scavenging effect, you actually alter the volumetric efficiency of the engine. The ECU code is calibrated with some particular efficiency in mind. That comes from testing when the engine is first designed. All fueling is set up with that in mind. You just changed this variable which now changes fueling. Since ECU has no way of knowing that, it just continues to do it's thing....business as usual. Remember, in open loop, ECU reads how much air it takes in an calculates IPW based on that. No feedback loop is involved to check and see if that calculation was correct. It's flying blind in OL. So, you change the VE with test pipes, you change the fueling. Interesting.

These are just my theories. I certainly don't have all the answers. Feel free to elaborate.

 

IMO i do think that the valve overlap and flow efficiency of test pipes and HFC's do have an effect on AFR's like you were saying. I have an 03 model so i didnt start out with the HFCs in the later year models so the jump in the ability of the engine to flow was largely increased . I remember seeing flowbench results of stock cats vs test pipes vs HFC's and the difference was night and day. heres a cutout from the other post:
03-06 OEM Cat: 145 CFM
07 OEM Cat: 180 CFM
07 name-brand HFC: 196 CFM
2.25" test pipe: 225 CFM

With that much change in flow the movement of air through the engine will no doubt change. ok gotta jet, ill get more into this at a later time.

EDIT*
ok got more time.
Ok onto VE,100% VE is the amount of air that would fill the cylinder when its at bottom dead center minus the combustion chamber volume while the engine is at rest, agreed? The 100% VE of this engine will never change with the addition of bolt ons, or even forced induction. The only way to alter an engines 100% VE is to increase its displacement. Now what we can do with bolt ons is affect the efficiency that the engine operates at, for example a stock motor operates at 75% of its VE, now we add breathing mods and now we operate at 80% VE. Now if we add forced induction and operate at 100% of or above VE.

now onto movement of air . Moving air takes time. so if the exhaust air flow is limited its going to take it longer to expell the exhaust which limits how much fresh air can fill the cylinder effecting the VE of the engine. The MAF is sending a voltage to the ecu which the ecu then puts into the fuel table and then applys the amount of fuel a stock motor would need based on stock fuel maps. Since we have changed the speed at which the exhaust air exits, now there is more room for good air. The ecu though has no way of reading this open loop and has dumped the fuel which is not enough for the larger amount of fresh air that has flowed into the chamber thus changing the AFR.

As for your question, I recorded no knock events after installation of the test pipes. But this is most likely due to the car being N/A, had i been F/I then I would have expected some knock.

 

Wow, fantastic data on the flow bench results. Apparently, the 07 cats are pretty good. It really makes me want to slap some test pipes on my 03.

Some good thoughts above. I thought about what you said. I agree with what you said. Here's some additional food for thought. Going with what you said, if the engine is taking in more air during the intake stroke, the ECU should be able to recognize most of it even in open loop. If we take in more air, where does it come from? There's only one place that it can and that is from the intake. The point of entry is measured with the MAF sensor so if you get more in on each stroke, all of the extra air going in has to go by the MAF and should be accounted for, right? Otherwise, you'd have empty, pure vacum in your intake and we know atmospheric pressure won't allow that. Since, like you said, the engine is not 100% efficient, the ECU must take a correction when actually calculating how much air is really going in based on the real life efficiency. I suspect that that's where the lean out could be coming from. The ECU knows it's getting more air during the intake, it just makes a bad calculation when it figures out how much of that air actually entered the engine based on calibrated efficiency. What do you think?

 

Hmmm... it makes sense. Heres a thought for you, and this is just a theory of mine and have no way to back this up. I'm thinking that since the exhaust air exits faster due to better flow it literally sucks more of the plenum air by resonation and vacuum. I'm thinking that the amount of air comming past the MAF sensor isnt increasing but the air going into the cylinder is,the excess thats left by the pulsing velocity of the air that is left after another cylinder closes is whats being used. Since we all know the plenum we have on our cars leaves room for improvement there will always be a surplus of air in the plenum and maybe its this surplus thats being drawn from. Now of course more air would have to come in at some point but its hypothetical that the air is comming at a slightly different time which could cause the AFR to get lean or rich at different points. All of this would be reflected in a dyno run as a wavy torque/HP curve. how does that sound?