Jump to content
wastntim

What is going on with CMC?

Recommended Posts

Smike
Maybe if you unplug those O2 sensors. They trim the AFRs right back every time, the only thing the FPR is good for long term is adding tip-in fuel. Not only have I read this, I lived it on my Crown Victoria. I tried to cheat and add more fuel to my GT40P top end equipped 5.0HO and after a day or 2 of driving, fuel was back to too lean again. I was anticipating this though, and tip-in was awful until I cranked up the pressure.

 

I have a wideband O2 on my car and can watch the AFRs just in case something goes south I can back off before kaboom.

 

4.6l and 5.0 are different beasts and programmed a bit differently.

Share this post


Link to post
Share on other sites
blk96gt
We're there any issues with AFR after the throttle body install? That would be my main concern with allowing throttle bodies, since there is the potential that it could lean the AFR out and potentially cause more issues.

 

A/F controlled by fuel pressure regular - 7.22.2.

 

Yeah I understand that. I was wondering what the difference in AFR was before/after adding the throttle body without adjusting FP. The reason I'm wondering is because the 99+ can't adjust fuel pressure, and really have no way to control the AFR.

 

I also agree with Supercharged111 that the FPR is just a band aide, and doesn't offer a reliable solution for adjusting AFR. I went through two engines, and had an AFR of 13.5+ on the dyno after the second (stock) rebuild. To solve this, I ended up installing 24 lb injectors and upping the FP at idle to 46 PSI. I also have the BBK timing adjuster, which I adjusted to -4* of timing. It runs rich as hell at idle, and after 3-4 sessions it will throw a lean code. What I found is that I have to shut the master switch off after session in order to avoid running lean. Cutting power to the ECU clears the long term fuel trims and causes the car to re-learn everything every time I go out on track. Personally, I think this is a shit solution, but it's the only way I know how to do it at this point. At least the 96-98 can adjust fuel pressure, the only option for the 99+ is bigger injectors, which again is only a band aide solution to a bigger problem.

 

Supercharged111 brings up another interesting point. Would being able to eliminate the O2 sensors in the tune eliminate some of these issues? Are you talking about getting rid of the front or rear O2 sensors, or all of them?

 

My understanding was yes the programming is different between the 5.0 and 96-98 4.6 computers, but the logic which determines fuel trims, AFR, etc. was very similar between the two. I'll look through my bookmarks when I get home and see if I can find where I read that. I may be misremembering though, so please correct me if I'm wrong on this.

Share this post


Link to post
Share on other sites
Dustin M.

No need for programming, just leave them unplugged and find a sweet spot on the AFPR and it'll stay running that way. Of course it's global, but you could probably get it a lot less bad that way.

Share this post


Link to post
Share on other sites
blk96gt

Are you talking about the front, rear or both O2 sensors?

Share this post


Link to post
Share on other sites
Smike
Yeah I understand that. I was wondering what the difference in AFR was before/after adding the throttle body without adjusting FP. The reason I'm wondering is because the 99+ can't adjust fuel pressure, and really have no way to control the AFR.

 

I also agree with Supercharged111 that the FPR is just a band aide, and doesn't offer a reliable solution for adjusting AFR. I went through two engines, and had an AFR of 13.5+ on the dyno after the second (stock) rebuild. To solve this, I ended up installing 24 lb injectors and upping the FP at idle to 46 PSI. I also have the BBK timing adjuster, which I adjusted to -4* of timing. It runs rich as hell at idle, and after 3-4 sessions it will throw a lean code. What I found is that I have to shut the master switch off after session in order to avoid running lean. Cutting power to the ECU clears the long term fuel trims and causes the car to re-learn everything every time I go out on track. Personally, I think this is a shit solution, but it's the only way I know how to do it at this point. At least the 96-98 can adjust fuel pressure, the only option for the 99+ is bigger injectors, which again is only a band aide solution to a bigger problem.

 

Supercharged111 brings up another interesting point. Would being able to eliminate the O2 sensors in the tune eliminate some of these issues? Are you talking about getting rid of the front or rear O2 sensors, or all of them?

 

My understanding was yes the programming is different between the 5.0 and 96-98 4.6 computers, but the logic which determines fuel trims, AFR, etc. was very similar between the two. I'll look through my bookmarks when I get home and see if I can find where I read that. I may be misremembering though, so please correct me if I'm wrong on this.

 

 

Sorry - didn't run without tuning A/F. Correct, 97-98 is a return style fuel rail. FPR has been reliable and repeatable and legal control of A/F.

 

99+ if those are your leavers, then those are the only rule friendly options to pull for 99+ cars given the current rules. Timing control and injector route (think of injectors like jets and needles to carbs) is legal for this series.

 

Tuning can remove rear O2 sensors.

 

Disconnecting the front O2:

When no signal is received from the O2 sensor, as is the case when a cold engine is first started (or the 02 sensor fails), the computer orders a fixed (unchanging) rich fuel mixture. This is referred to as "open loop" operation because no input is used from the O2 sensor to regulate the fuel mixture. If the engine fails to go into closed loop when the O2 sensor reaches operating temperature, or drops out of closed loop because the O2 sensor’s signal is lost, the engine will run too rich causing an increase in fuel consumption and emissions. A bad coolant sensor can also prevent the system from going into closed loop because the computer also considers engine coolant temperature when deciding whether or not to go into closed loop.

 

Having the front O2s is a good and needed item. We like to think we drive flatout at all times; reality is we use some level between 0-100 throttle.

Share this post


Link to post
Share on other sites
Dustin M.
Are you talking about the front, rear or both O2 sensors?

 

Fronts are the only ones that trim out the fuel, rears function is to alert you to a failing cat and also to notify the ECM of an overheating catalyst, at which point I know GM begins to dump more fuel (I assume this is universal).

Share this post


Link to post
Share on other sites
blk96gt

Maybe my understanding of how the ECU on these cars work is wrong, but wouldn't adjusting fuel pressure and adding bigger injectors be a temporary fix?

 

The way I understand it is that even though you increase the fuel flow by increasing fuel pressure and/or adding larger injectors, the computer will adjust the pulse of the injector to match the amount of fuel it thinks it should get. Whether the fuel volume delivered is based on predetermined fuel tables or calculated AFR, I'm not sure. I think it is determined by certain parameters that the computer sees? If this is the case, then adding larger injectors would not be a good solution for the 99+ guys. Yes, initially you would get more fuel delivered, but over time (I have no idea how long) the computer would default back to adjusting injector pulse to determine the amount of fuel delivered.

 

Smike,

 

What is your current FP at idle and under full throttle? What AFR do you typically see on the dyno and on the track?

Share this post


Link to post
Share on other sites
Smike
Maybe my understanding of how the ECU on these cars work is wrong, but wouldn't adjusting fuel pressure and adding bigger injectors be a temporary fix?

 

The way I understand it is that even though you increase the fuel flow by increasing fuel pressure and/or adding larger injectors, the computer will adjust the pulse of the injector to match the amount of fuel it thinks it should get. Whether the fuel volume delivered is based on predetermined fuel tables or calculated AFR, I'm not sure. I think it is determined by certain parameters that the computer sees? If this is the case, then adding larger injectors would not be a good solution for the 99+ guys. Yes, initially you would get more fuel delivered, but over time (I have no idea how long) the computer would default back to adjusting injector pulse to determine the amount of fuel delivered.

 

Smike,

 

What is your current FP at idle and under full throttle? What AFR do you typically see on the dyno and on the track?

 

To my understanding of this car. The ECUs are hard tables. Meaning they are not adaptive in these cars. (Note - newer cars have become smarter...ours are to cavemen as they are to NASA engineers). Our front O2s are not widebands with instant tuning. Timing and fuel tables will only do so much. And since the tables are hard coded, repeatable. Just like the BBK timing devise changes global timing.

 

Don't have that here. I've been pretty transparent overall, but my A/F is one that I wish to keep mine.

Share this post


Link to post
Share on other sites
Spencer

I was under the impression that the throttle body & upper intake plenum would be a bolt on modification not requiring any fuel upgrades. Seems like its just like bolting on a CAI moving more air into the engine.

Share this post


Link to post
Share on other sites
Smike
I was under the impression that the throttle body & upper intake plenum would be a bolt on modification not requiring any fuel upgrades. Seems like its just like bolting on a CAI moving more air into the engine.

 

You are still correct. I think we are getting too far into the weeds here as well.

 

This is a bolt-on improvement.

 

As with any bolt-on, you can fine tune -- that is left up to the allowable rules and users skill-sets/preferences.

Share this post


Link to post
Share on other sites
blk96gt

Just to clarify, I'm not against allowing an aftermarket throttle body. I just don't want to add something with the potential to cause more problems. My whole point in bringing up AFR was that I thought there could be the potential for a throttle body to lean out the AFR, and that could potentially lessen the life of the engine.

 

Since this is amateur racing and I don't give a shit if everyone knows what I am running, be it engine or otherwise, I will list what I have done to my motor and the power I make.

 

Engine Specs:

- '96 block, crank and rods

- '96 ECU

- bored .020 over

- BBK FRP

- BBK Timing Adjuster

- 24 lb. injectors

- K&N CAI

- '04 FRPP PI heads

- 11 cc hypereutectic pistons

- A/C delete

- Underdrive pullies

- Stock headers

- Pypes off-road x-pipe, dumped right after the x-pipe, no mufflers

 

- AFR: 12.5

- [email protected]: 46-46.5psi

- [email protected]: 41-42psi

- Timing Adjuster: -4*

- Compression: Cyl#1=85-90psi; Cyl#2-8=175-185psi

 

HP/TQ:

- April 2014 - 253/296 (9 weekends on engine)

- January 2014 - 267/307 (6 weekends on engine)

- September 2013 - 266/303 (3 weekends on engine)

- April 2013 - 264/302 (This was just after the engine was rebuilt)

 

All were done on the same dyno except the January-14 run. Of the 9 weekends on the engine pre-April 2014 dyno, 3 were race weekends, the rest were DE's. I've done two more weekends since the dyno in April (1 race and 1 DE), and plan to head back to the dyno September 9 to make sure the engine hasn't shit the bed. The only things that has changed since the April 2013 dyno are gears and passenger side coil pack. Gears were swapped to 3.27's from 3.73's in August of 2013. I changed the coil pack just before doing the dyno in April this year to an AutoZone special thinking that was the cause of my misfire. I have a Motorcraft coil pack on there again, and will be interested to see if that makes any difference.

Share this post


Link to post
Share on other sites
t500hps

Man, you guys have me reading intently even though I'm not understanding everything I read. Reason.......Last year I bought a competitive built CMC car but have very limited mechanical ability. I never could have built a car to race even though I've done quite well as a driver. I THINK my car is legal, and it has passed all inspections and dyno pulls, but I really don't know if the previous owners put anything on it that isn't legal.

 

Without changing the direction of this conversation, I'm going to come back later and ask what (and how) I can check some of these items to make sure my car is legal for next years nationals at VIR. Guess I'm just nervous since I don't know what I have but my competitors raced against this car before and all seem to think it's good to go......except the guys I beat as a rookie and mumble that I must be cheating

 

96 GT

4.6/ PI heads

3.27 gears/cobra brakes

pulleys?

external timing adjuster (not even sure what it's set at)

260/298 (if I recall correctly)

Share this post


Link to post
Share on other sites
BADVENM

Maybe we can start a new thread on this since its kind of off topic about the state of CMC in general?

Share this post


Link to post
Share on other sites
Dustin M.

I think at page 6 it's about spent anyway. 96blkgt you need headers, then you'll see an improvement. With an AFR of 12.5:1 you're doing real good. The old 5.0 ECMs were very adaptive indeed, I watched with my own eyes on the wideband. Bump fuel pressure, WOT AFRs get richer. By the time I'm driving home from work, they've leaned out again. In those PCMs, it was a 2D table of ECT vs load that determined your long term fuel trims. Just like clockwork, the O2s would trim the WOT AFRs right back to where they were before you monkeyed with fuel pressure. Never tried on a 4.6, never saw myself if they'd upgraded to a 3D table for LTFTs.

Share this post


Link to post
Share on other sites
blk96gt

Why do I need headers? I'm down on power because cylinder #1 has half the compression of the rest. I'm not going to add headers because I have a bad cylinder.

 

From what I've read, the Mustangs have had an adaptive ECU since 1986. The amount of learning/adaption that happens has increased over the years. Also, the front O2's may not be "wideband", but they do tell the computer whether it's seeing a rich or lean condition, and the computer attempts to adjust accordingly. The problem is it doesn't just use the O2 sensors. It uses TPS, IAT, FP, MAF, and a host of other sensors to make adjustments to fuel delivery. Which sensors it uses depends on if it's in open or closed loop mode, idle, WOT, part throttle, engine load, etc.

Share this post


Link to post
Share on other sites
Smike

My point for the TB/P is simple. How much did you spend on that motor to get power? Never-mind the outside of the box fine tuning.

 

I have a junkyard motor with 100k, underdrives, K/N cone filter, headers, FPR and TB/P. That's it. Keep it simple and cheap.

 

No blueprinted motors. Custom builds. Mechanic or engineering degrees required.

 

And bottom line - if you can make the power without the TB/P - GREAT! No additional parts or work needed. However, if you cannot and spending $3k for a blueprinted tweaked motor doesn't give you the warm and fuzzies, then its a viable and cost effective option.

 

Again, just because it (if it passes) becomes an allowed part - its does not mean you must have it.

Share this post


Link to post
Share on other sites
Spencer
Why do I need headers? I'm down on power because cylinder #1 has half the compression of the rest. I'm not going to add headers because I have a bad cylinder.

.

 

FYI - I went from cast manifolds to Longtubes and dynoed before and after with no change in my numbers. On my 4.6 headers did absolutely nothing for me.

Share this post


Link to post
Share on other sites
blk96gt

Just as an FYI, my motor is not some custom built super motor. It's a stock rebuild. Machine work cost $500. The pistons were somewhere well south of $500, and are just stock pistons .020" over stock size, and the stock crank and rods were re-used.

 

If others think (or better, yet, have proof) that adding a throttle body has a minimal effect on AFR, then I hope that's based on previous experience and not an assumption. I'm not trying to argue against this, even though it may seem like it. I'm trying to make sure all angles have been thought about before allowing another mod on cars that have historically had issues with AFR. If I was a director I would vote yes to allow it. I just worry about the 99+ cars, since they have no way to reliably adjust AFR.

 

After doing some more reading last night, from what I can find just swapping injectors on the car will initially increase the fuel delivered, but the computer will eventually adjust the injector pulse (how long this takes I have no idea) to allow the predetermined fuel to be delivered through the injector. Also remember that for a 96-98, you're taking a car that had 215 crank HP stock and adding ~75 hp to it. The 99+ are adding ~40 hp over stock.

Share this post


Link to post
Share on other sites
blk96gt

FYI - I went from cast manifolds to Longtubes and dynoed before and after with no change in my numbers. On my 4.6 headers did absolutely nothing for me.

 

That's interesting. What other 4.6's have longtubes? Anyone else have a before/after dyno? I know Jerry and Jeremy have them (both 99+ cars), but I'm not sure about Aaron. Maybe he'll chime in?

 

Spencer,

I know it's a pain in the ass, but would you be willing to check your compression again, unless you happen to remember the numbers you got?

 

Dave B,

Would you be willing to check your compression? You've got pretty much the same motor I have (except for the .020" over on the cylinders), so I'd be interested to know how yours compares.

Share this post


Link to post
Share on other sites
Smike
Just as an FYI, my motor is not some custom built super motor. It's a stock rebuild. Machine work cost $500. The pistons were somewhere well south of $500, and are just stock pistons .020" over stock size, and the stock crank and rods were re-used.

 

If others think (or better, yet, have proof) that adding a throttle body has a minimal effect on AFR, then I hope that's based on previous experience and not an assumption. I'm not trying to argue against this, even though it may seem like it. I'm trying to make sure all angles have been thought about before allowing another mod on cars that have historically had issues with AFR. If I was a director I would vote yes to allow it. I just worry about the 99+ cars, since they have no way to reliably adjust AFR.

 

After doing some more reading last night, from what I can find just swapping injectors on the car will initially increase the fuel delivered, but the computer will eventually adjust the injector pulse (how long this takes I have no idea) to allow the predetermined fuel to be delivered through the injector. Also remember that for a 96-98, you're taking a car that had 215 crank HP stock and adding ~75 hp to it. The 99+ are adding ~40 hp over stock.

 

Historically had AFR issues? Not to be confused with you have had AFR issues - right? Not looking to be an asshole about this. We cannot afford to base singular/few examples as "whole world issues".

 

TB/P is a very very very very very popular modification for the 4.6L. Why? Works. Simple.

 

Added costs - do you do the work or have a mechanic or shop do it? Cost to re-assemble motor? Who pulled it out of the car? Etc. Those are often scary and daunting items for a person that wants to get into this racing. Put yourself in the "I have a hunk of metal that when I add gas it goes" level of mechanical understanding camp. You just made the driver shart out a bit of brown with $$$$ signs.

 

Or are we telling all hopeful CMC drivers that you better have an advanced degree in mechanics and engineering, spent time in Formula SAE, oh - and you should be a a test driver?

 

All angles do not need to be thought this far out. Again, every modification needs to be holistically evaluated to your situation and car. That goes for any modification. You add and have to mitigate risks. If you see AFR as your risk; it is your responsibility to mitigate that risk with the appropriate (aka legal) corrective actions.

Share this post


Link to post
Share on other sites
Spencer

FYI - I went from cast manifolds to Longtubes and dynoed before and after with no change in my numbers. On my 4.6 headers did absolutely nothing for me.

 

That's interesting. What other 4.6's have longtubes? Anyone else have a before/after dyno? I know Jerry and Jeremy have them (both 99+ cars), but I'm not sure about Aaron. Maybe he'll chime in?

 

Spencer,

I know it's a pain in the ass, but would you be willing to check your compression again, unless you happen to remember the numbers you got?

 

.

 

Sorry I really dont remember the exact numbers, just that everything was within spec and none of the cylinders were low. I rented the tester so its not something I am going to do again unless I am trying to diagnose a problem.

Share this post


Link to post
Share on other sites
Dustin M.
Why do I need headers? I'm down on power because cylinder #1 has half the compression of the rest. I'm not going to add headers because I have a bad cylinder.

.

 

FYI - I went from cast manifolds to Longtubes and dynoed before and after with no change in my numbers. On my 4.6 headers did absolutely nothing for me.

 

That's insane! Did it lean the motor out? Longtubes are known to make more torque, that's where they really shine. I felt a noticeable difference in my Z06 going from cast manifolds to longtubes, and the stockers are a bit of a tri-y design at that. Truck was the same way, ditched logs for longtubes and it held OD up a hill noticeably better.

Share this post


Link to post
Share on other sites
Spencer
Why do I need headers? I'm down on power because cylinder #1 has half the compression of the rest. I'm not going to add headers because I have a bad cylinder.

.

 

FYI - I went from cast manifolds to Longtubes and dynoed before and after with no change in my numbers. On my 4.6 headers did absolutely nothing for me.

 

That's insane! Did it lean the motor out? Longtubes are known to make more torque, that's where they really shine. I felt a noticeable difference in my Z06 going from cast manifolds to longtubes, and the stockers are a bit of a tri-y design at that. Truck was the same way, ditched logs for longtubes and it held OD up a hill noticeably better.

 

I think the stock manifolds on a 4.6 flow well enough to support our power levels.

Share this post


Link to post
Share on other sites
blk96gt

Historically had AFR issues? Not to be confused with you have had AFR issues - right? Not looking to be an asshole about this. We cannot afford to base singular/few examples as "whole world issues".

 

TB/P is a very very very very very popular modification for the 4.6L. Why? Works. Simple.

 

Added costs - do you do the work or have a mechanic or shop do it? Cost to re-assemble motor? Who pulled it out of the car? Etc. Those are often scary and daunting items for a person that wants to get into this racing. Put yourself in the "I have a hunk of metal that when I add gas it goes" level of mechanical understanding camp. You just made the driver shart out a bit of brown with $$$$ signs.

 

Or are we telling all hopeful CMC drivers that you better have an advanced degree in mechanics and engineering, spent time in Formula SAE, oh - and you should be a a test driver?

 

All angles do not need to be thought this far out. Again, every modification needs to be holistically evaluated to your situation and car. That goes for any modification. You add and have to mitigate risks. If you see AFR as your risk; it is your responsibility to mitigate that risk with the appropriate (aka legal) corrective actions.

 

I had an AFR issue early on due to a chip being installed in the computer when I first got the car. I had no idea it was in the car, and appeared to have been in the car since before it was a race car. Since that fiasco was figured out, I have had no major issues. I do have to shut the master switch off after every session, but that's not that big of a deal. I thought I was pretty clear that I have not had major issues (after the chip was discovered), and my concern was for others, mainly the 99+ cars, which have no reliable way to adjust AFR.

 

Again, I have no issues with allowing this mod, but I think it would be good to have at least one or two people who add a throttle body to get a before/after AFR. It's a pretty quick install and could easily be done while doing an annual dyno. Do I think it's necessary? Not really, but I think it would be a decent data point to have to help others decide whether they want to do this or not.

 

I had someone else do my engine work. I dropped the car off, they pulled the motor, sent the parts to the machine shop, assembled it, and put it back in the car. I think it cost ~$3500, but I don't really remember as that was almost two years ago. I am in the "I have a hunk of metal that when I add gas it goes" camp. Before I bought this car (it was already built for CMC) the only thing I had ever done to a car was change oil and I put a cat-back on a couple times. I have no desire to work on my own car, but sometimes it's a necessity if I want to be able to afford this hobby. Other times I'm willing to pay someone to hopefully have it done right the first time (ie engine work). Pretty much everything I've learned about this car has been due to something breaking. The last thing I want to do is break more shit.

Share this post


Link to post
Share on other sites
Smike

I had an AFR issue early on due to a chip being installed in the computer when I first got the car. I had no idea it was in the car, and appeared to have been in the car since before it was a race car. Since that fiasco was figured out, I have had no major issues. I do have to shut the master switch off after every session, but that's not that big of a deal. I thought I was pretty clear that I have not had major issues (after the chip was discovered), and my concern was for others, mainly the 99+ cars, which have no reliable way to adjust AFR.

 

Again, I have no issues with allowing this mod, but I think it would be good to have at least one or two people who add a throttle body to get a before/after AFR. It's a pretty quick install and could easily be done while doing an annual dyno. Do I think it's necessary? Not really, but I think it would be a decent data point to have to help others decide whether they want to do this or not.

 

I had someone else do my engine work. I dropped the car off, they pulled the motor, sent the parts to the machine shop, assembled it, and put it back in the car. I think it cost ~$3500, but I don't really remember as that was almost two years ago. I am in the "I have a hunk of metal that when I add gas it goes" camp. Before I bought this car (it was already built for CMC) the only thing I had ever done to a car was change oil and I put a cat-back on a couple times. I have no desire to work on my own car, but sometimes it's a necessity if I want to be able to afford this hobby. Other times I'm willing to pay someone to hopefully have it done right the first time (ie engine work). Pretty much everything I've learned about this car has been due to something breaking. The last thing I want to do is break more shit.

 

I understand you are in favor. And the $3500 is the true costs here v. $300.

 

My point is that it appears you are muddling your cars "needs" verses the needs of a platform.

 

I am not in favor of requiring this RCR to have an AFR test. That goes back to the user needing to do all their own homework and evaluations for what is their best needs.

Share this post


Link to post
Share on other sites

×
×
  • Create New...