a new and better use for EGR

[oldred95]

I'm once again running in lean open loop highway mode if you will and since I have vortec heads and a non EGR intake and really could give a damn less about EGR in general Fast305 had an idea and suggested I try using the EGR tables to add timing accordingly for open loop highway mode. What I'm doing is leaving all the EGR constants, flags and tables at the stock settings except the table EGR Spark Correction vs RPM vs Vacuum of which I doubled it. The leaner you run the engine the more timing it requires to ignite the mixture. Anyway so now at highway speeds I'm running around 16 to 16.5:1 AFR and an added 7.73 degrees timing advance all thanks to the EGR system. I will have fuel mileage results sunday. As of my last highway trip I was making 16 mpg in closed loop blowing within a few points of 128 in all cells.

[Tbi-MAX]

damn, both you and Fast305... what would TBI guys do without yall.. :mushy:
please keep us informed, as you know ill be tunning my stroker sometime this week...

[oldred95]

damn, both you and Fast305... what would TBI guys do without yall.. :mushy:
please keep us informed, as you know ill be tunning my stroker sometime this week...
Fast305 yes, me well thats debatable. I know a good amount from first hand experience but theres a lot of other BS in there too.

Will do.

[91chevZ71]

so what's your total timing in cruise mode? +7.75 is a lot. just curious

[HaulnA$$]

I'm once again running in lean open loop highway mode if you will and since I have vortec heads and a non EGR intake and really could give a damn less about EGR in general Fast305 had an idea and suggested I try using the EGR tables to add timing accordingly for open loop highway mode. What I'm doing is leaving all the EGR constants, flags and tables at the stock settings except the table EGR Spark Correction vs RPM vs Vacuum of which I doubled it. The leaner you run the engine the more timing it requires to ignite the mixture. Anyway so now at highway speeds I'm running around 16 to 16.5:1 AFR and an added 7.73 degrees timing advance all thanks to the EGR system. I will have fuel mileage results sunday. As of my last highway trip I was making 16 mpg in closed loop blowing within a few points of 128 in all cells.I am a firm believer in sharing information so we all learn. What I don't like is when someone claims someone else's ideas as their own. The idea of using the EGR spark table for lean cruise did not come from Fast305 but rather from me as have a lot of other things that other people claim credit for. This is from post #430 in the "EPROM Tuning Software " sticky dated 2/7/2007 and actually put into use by myself at least a year earlier.

The $0D mask does not have the ability for spark advance during lean cruise. however, there is a work around if you don't run an EGR valve. I'm going to reveal another one of my secrets here. This actually works very well. If you don't run an EGR valve, which I don't, you can leave the qualifiers set to enable EGR, disable error 32, and set the Desired EGR table and the Fuel Reduction % w/EGR on table to all zero's. By doing this you will have zero % EGR commanded as well as zero fuel reduction (remember you are doing this with lean cruise) but the EGR Spark Correction table will still apply. You can then set this table to add spark where you are removing fuel with lean cruise.

As for what you should do to tune open loop fuel safely. That is simple, remove your cat. Here's what I did, I took my old tired original cat and gutted it. I then bought a cheap universal Catco converter from Summit and fabbed up the pipes to be able to replace it when it is time to pass the sniff test, then I remove it after testing. Cost me like $60 total. This accomplishes two things. I am running a gutted cat for 51 weeks out of the year and when I do install a cat for testing, it is like new and a new cat can be very forgiving when getting sniffed. HTH

I am not one of those guys that likes to pound my chest and say look at what I've done which is why you almost never see me post about this wicked truck I have tuned or that one. I let my knowledge speak for me but I have to get this off my chest. It was me that first used the '7427 to control E-Fans. I was also the first control a N2O solenoid with a '7427. While I was not the first to make a '7427 run batch fire TPI, I perfected it. There are a number of other things I have done as well. If it been done with a TBI PCM, I either did it first or helped whoever did. I know I am ranting and I don't even know if it is warranted but I feel like I have to defend myself. BTW Kurt, look at the "EPROM Tuning Software " sticky and see what I postes about timing and engine braking three years ago. Give credit where credit is due. JMHO

[oldred95]

I'm sorry about that Tom. I guess I shouldn't be saying so and so had an idea, rather so and so remember that if you do such and such. Your an absolute genius when it comes to tuning and I didn't mean to steal your thunder like that, I guess I just didn't realize who had originally come up with the idea.


Overall timing is 25.31 + 7.73 = about 33 degrees.

Hey Tom? One thing I forgot to do was set the fuel reduction with EGR on table to zero and after looking I don't even have that table in my XDF. Could you point me in the direction of the address and some columns and rows so I could setup the table? Please? And one last thing I noticed. Chris told me to set the Desired EGR vs RPM vs Load to one which tunerpro changes to 1.17 when you hit save. Anyway after datalogging I found that this did not add any timing. I switched it to what my stock bin shows as 99.61 throughout the table and got instant timing advance changing nothing but that. Chris thought that was odd I had to do that so I thought I'd ask the man why it might be doing this. Thank you in advance.

[Fast305]

I am a firm believer in sharing information so we all learn. What I don't like is when someone claims someone else's ideas as their own. The idea of using the EGR spark table for lean cruise did not come from Fast305 but rather from me as have a lot of other things that other people claim credit for. This is from post #430 in the "EPROM Tuning Software " sticky dated 2/7/2007 and actually put into use by myself at least a year earlier.



I am not one of those guys that likes to pound my chest and say look at what I've done which is why you almost never see me post about this wicked truck I have tuned or that one. I let my knowledge speak for me but I have to get this off my chest. It was me that first used the '7427 to control E-Fans. I was also the first control a N2O solenoid with a '7427. While I was not the first to make a '7427 run batch fire TPI, I perfected it. There are a number of other things I have done as well. If it been done with a TBI PCM, I either did it first or helped whoever did. I know I am ranting and I don't even know if it is warranted but I feel like I have to defend myself. BTW Kurt, look at the "EPROM Tuning Software " sticky and see what I postes about timing and engine braking three years ago. Give credit where credit is due. JMHO

Tom,

That is all good and great. I cannot defend using the 427 in that manner since I had barely switched to it when you posted that. I can however tell you that I started using EGR timing advance tables for "Lean cruise highway mode SA" on the 299 over 3 years ago. I even created a TunerproRT XDF from a commented hack that I found on the internet. I shared the idea of using the lean cruise mode and advancing the timing by using the EGR logic with Kurt to help him break his 16 mpg.

I was controlling the cooling fans with the 299 as well, using the AIR logic with some re-written code.

I haven't gotten into real depth with the MPFI running on the 427 or nitrous for that matter.

[oldred95]

Still interested in the EGR fuel reduction table if anyone knows anything about it.

[oldred95]

Haven't filled up yet but here's the latest as of today. Left Enid with 55 miles on this tank of pure city driving and the way it was going it was averaging 13 or so city. Took the long way to my parents house going through a stretch or hills for probably 50 miles total and running without cruise (it doesn't work) I kept my foot in the same spot and hauled arse down the back side of the hills and then climbed the next hill just barely dipping down to my cruising speed. Anyway its sitting a little over half a tank which would take about 11-12 gallons to fill it at this point and its showing 185 miles. I have just been driving normally too, not hard and not babying it. Power is superb to what its ever been and I had the AC on. Typically pure highway with the foot of an infant I'd be doing damn good to make 180 miles before dipping below half a tank but usually it was more like 160 to 170 miles. Now I'm shooting for a solid 200 miles before half a tank. At this point I'm not sure what kind of gas mileage I'm getting but going by the gauge reading and the miles its never made it this far on that amount of fuel. I'll know more tomorrow evening.

[91chevZ71]

sounds cool. You know, I read a big thread over at thirdgen about how (believe it or not) less timing on the highway yielded MORE mpg. I'm gonna see if I can find it

[oldred95]

sounds cool. You know, I read a big thread over at thirdgen about how (believe it or not) less timing on the highway yielded MORE mpg. I'm gonna see if I can find it
Yea too much timing is just as bad as too little timing. Gas mileage wasn't what I was hoping for. According to the gas gauge it was doing pretty good but it only worked out to 15 mpg.

[DefEddie]

Speaking of using EGR for other thing's,maybe i'll mention this even though I was going to do it on an OBDII vortec.
I was going to use the EGR function to regulate the VGT on a powerstroke turbo,they use the same voltage reference signal and the EGR has many tuneable function's such as timing,etc..
Figured I could use the EGR to regulate the boost which would regulate the timing automatically.
Seemed like a safe way to use LOTS of boost maybe.
Decided not to go into it much more when I got stumped on the problem of getting the high oil pressure that actuate's the VGT.
I didn't want to spend the money on HP oil pump's.
I would love to see someone do it though,I just decided to not use a VGT turbo.
Still thinking of looking into regulating a boost control with the EGR function though,in the back of my head.
(Oh and it's not with a vortec "black box",i'm using the LS6 ECM on the vortec)

[90C350]

Just wondering what you guys consider good fuel mileage?? I got 18mpg In my pu, on my last trip up country. THats highway though. With about 1100lbs in the box and averaging about 70to80mph. It was a little rich going up the hills and Im currently working on that. Its a mild 350 with a 700r4 trans. Just out of curiosity How do you control electric fans with the 7747?? Thanks guys.

[93ChevyTBI]

I've been thinking about this for a while....I'm getting no better than 14 mpg on highway. How lean can I make my AFR at lean cruise without any danger of blowing things up/causing damage? I don't know what I'm running right now but I do know BLM's are 128 on the money (14.7 then, right?) Can I go to 32 on the BLM's? higher? I'm not gonna change anything right now but will when I swap in my Voodoo cam. thanx

[DefEddie]

How lean you can go depend's on to many variable's to really calculate I think.
Some rally car's run 15.1+ from what I understand.
Lean CRUISE isn't a big issue though I don't think cause your not generating heat and stress(load) on the motor.
For instance your running 16.1 AFR during light cruise at about 25% tps and 30% load. That more than likely won't cause undue heat or stress in the cylinders.
Now stomp your foot to the floor,your at 90% load and WOT. The motor's filling every cylinder as full as it can and the temp is just rising cause the hotter burn(lean) is bigger(more air) and coming on quicker with the higher RPM.
It doesn't take long to melt something.
Fuel will cool down the combustion process more efficiently,not to mention there is more available energy the closer you get to stoich.
That's my take on it,i'm not a pro tuner though.
Somebody plz post up a more non confusing explanation.

[discostu]

The way I understand it (which maybe be wrong) is this:
When you are cruising, say at stoich, you are generating a certain amount of heat.
Now say you go to lean cruise, same rpm, same throttle, you need more timing to generate the same power (because there's less fuel, slower burn time). This increase in timing is (from what I understand) the main reason for the increase in cylinder temp. There's also less fuel cooling.

The way I learned it was that timing was the most influential factor in cylinder temps because with more advanced timing, the heated gases spend more time in the cylinder, and less time in the exhaust manifold.
Does a lean mixture physically burn "hotter"? Or is it just a function of more fuel cooling with a rich mixture?

[Fast305]

The way I understand it (which maybe be wrong) is this:
When you are cruising, say at stoich, you are generating a certain amount of heat.
Now say you go to lean cruise, same rpm, same throttle, you need more timing to generate the same power (because there's less fuel, slower burn time). This increase in timing is (from what I understand) the main reason for the increase in cylinder temp. There's also less fuel cooling.

The way I learned it was that timing was the most influential factor in cylinder temps because with more advanced timing, the heated gases spend more time in the cylinder, and less time in the exhaust manifold.
Does a lean mixture physically burn "hotter"? Or is it just a function of more fuel cooling with a rich mixture?

Actually the mixture will burn hottest at stoich, not at lean cruise. All the fuel and all the air is used in theory at 14.7:1 afr. I have recorded decreases in EGT as the engine is leaned above 15.5:1. I typically find the best fuel mileage at about 16.5:1 afr.

[DefEddie]

I was under the impression it would burn hotter the leaner it got due to the excess oxygen.

Found this on Wiki.
Lean mixtures produce cooler combustion gases than does a stoichiometric mixture, primarily due to the excessive dilution by unconsumed oxygen and its associated nitrogen. Rich mixtures also produce cooler combustion gases than does a stoichiometric mixture, primarily due to the excessive amount of carbon which oxidises to form carbon monoxide, rather than carbon dioxide. The chemical reaction oxidising carbon to form carbon monoxide releases significantly less heat than the similar reaction to form carbon dioxide. (Carbon monoxide retains significant potential chemical energy. It is itself a fuel whereas carbon dioxide is not.) Lean mixtures and rich mixtures, when consumed in an internal combustion engine, both produce less power than does the stoichiometric mixture. Similarly, lean mixtures and rich mixtures return poorer fuel efficiency than the best mixture. (The mixture for the best fuel efficiency is slightly different to the stoichiometric mixture.)

Debunked what I thought.
It also had some interesting info I had forgotten,that additives and stuff added to gas will alter the stoich ratio.
You think this could a small part of the reason's no AFR is perfect for every vehicle?
In theory a stoich AFR on a perfectly running 100% efficient engine will consume all oxy/fuel right?
So what does excess fuel or air really do for you if the above underlined sentence were true,other than carbon deposit's. I assume it's due to all the inefficiency of the engine and fuel used,since few are more than 85% or so VE usually right?

[Fast305]

I was under the impression it would burn hotter the leaner it got due to the excess oxygen.

Found this on Wiki.


Debunked what I thought.
It also had some interesting info I had forgotten,that additives and stuff added to gas will alter the stoich ratio.
You think this could a small part of the reason's no AFR is perfect for every vehicle?
In theory a stoich AFR on a perfectly running 100% efficient engine will consume all oxy/fuel right?
So what does excess fuel or air really do for you if the above underlined sentence were true,other than carbon deposit's. I assume it's due to all the inefficiency of the engine and fuel used,since few are more than 85% or so VE usually right?

Slightly richer than stoich AFR ratios are desired (especially on wet flow manifolds) because it consumes ALL the available oxygen, creating more cylinder pressure and more torque. This creates more HP across the board. I have a feeling that direct injection engines WILL run near 14.6:1 for peak power, maybe slightly richer for the slight cooling effect given.

[DefEddie]

Okay,I think I get it now.
If we can't get a perfect burn of all the gas,then at least get enough excess fuel to burn all the oxygen.
I forget that fuel will only burn off the surface of a droplet,and that a more complete burn just isn't possible with the current tech due to atomization constraint's.
Direct injection would be awesome,i've been keeping my eye out for injector's that will stand 100psi+ without locking them up.
The diesel's at Ford have DI,but it use's insane amount's of oil pressure to actuate the injector(20,000psi+)
Can't wait for DI on gas engine's to become standard.

[oldred95]

Most diesels are direct injection. The 6.5 is supposed to be indirect injection I guess. Not sure exactly how that works.

Direct injection eliminates octane requirements too since the fuel is not entered into the mix until DTC.

[davo727]

Well you guys im a begginer at pcm tuning and appreciate any and all info and help shared here by the experienced members . So I hope you all with more experience will continue to help out me and the other newbietuners :) So thanks for your efforts.

[93ChevyTBI]

One more thing here before this thread is forgotten...when tuning for lean cruise, do you tune by BLM's or your 02 voltage? I can find 02 voltage to correspond to 16.5 AFR but what BLM would that equal? around 134 or so?

thanx

[oldred95]

One more thing here before this thread is forgotten...when tuning for lean cruise, do you tune by BLM's or your 02 voltage? I can find 02 voltage to correspond to 16.5 AFR but what BLM would that equal? around 134 or so?

thanx
You tune it to run as close to 128 in all cells in closed loop as you can. Then you check flag L400D Bit 0 which keeps it in open loop until the max temp for open loop is reached. You need to set this temperature to around 150 celcius so that it always stays in open loop. Once this is done you can log it and last time I did it the BLM's did show slightly lean throughout.