too lean, glowing muffler, blown engine?

[NabilUofL]

We have just finished tuning our AFR with no load, and wanted to start tuning/data logging under load while driving. Our driver was instructed to drive it like he would on a course, and in doing so he turned the header glowing red, and melted the inside of the muffler. We stopped him when a perpetual 2 foot flame was shooting out of the pipe.

We let the car cool down, and since then have been unsuccessful in getting the car to restart. After analyzing the data our AFR was between 17 and 23 under any load.

We find this perplexing because at idle (0 degrees TPS) with 2ms injector pulse width we are running 12:1. at 90 degree TPS we are running 4ms, which gives us the 20:1. According to the AFR data the correct pulse should be 7ms. We tried the higher pulse width before we melted the muffler; this fouled the plugs and made starting impossible.

The setup of our vehicle is a Honda F4i with a PE ecu and stock injectors at 50 PSI with NGK plugs.

We were wondering if anyone with similar setups has had to run such high numbers at the top of their fuel map? We are also wondering if the three minute run (being lean) could severely damaged our engine? The last thing we were wondering is if a glowing header can be the cause of running it too rich (misfires deceiving the AFR unit) or too lean?

[NabilUofL]

We have just finished tuning our AFR with no load, and wanted to start tuning/data logging under load while driving. Our driver was instructed to drive it like he would on a course, and in doing so he turned the header glowing red, and melted the inside of the muffler. We stopped him when a perpetual 2 foot flame was shooting out of the pipe.

We let the car cool down, and since then have been unsuccessful in getting the car to restart. After analyzing the data our AFR was between 17 and 23 under any load.

We find this perplexing because at idle (0 degrees TPS) with 2ms injector pulse width we are running 12:1. at 90 degree TPS we are running 4ms, which gives us the 20:1. According to the AFR data the correct pulse should be 7ms. We tried the higher pulse width before we melted the muffler; this fouled the plugs and made starting impossible.

The setup of our vehicle is a Honda F4i with a PE ecu and stock injectors at 50 PSI with NGK plugs.

We were wondering if anyone with similar setups has had to run such high numbers at the top of their fuel map? We are also wondering if the three minute run (being lean) could severely damaged our engine? The last thing we were wondering is if a glowing header can be the cause of running it too rich (misfires deceiving the AFR unit) or too lean?

[Wesley]

I would suggest retarded timing, coupled with a rich condition.

Possible overly rich conditions could contaminate your O2 sensor and make it register lean, but more likely delayed burning due to retarded timing can cause a lot of oxygen to still be present in the exhaust stream (as it is still burning) generating a lean signal.

I would suggest actually leaning your map out a bit. What sort of timing map are you running? From our experience, it takes a lot of spark advance to properly ignite the thin mix (due to the restrictor killing mass flow into the cylinders)

We have run our headers cherry red before under similar circumstances, with no apparent damage to the engine. The muffler was titanium and did not melt.

[Pete M]

Firstly, you aren't just running the same pulse width at all engine speeds are you? I suppose that wouldn't be ridiculously bad as an initial guess before dyno tuning it, but just going driving with such a heavily guessed table is likely going to be difficult. Don't PE provide base maps to get you started? The best way is to put it on a dyno. If your team doesn't have one, are there any shops near you that could help? Failing that, try driving in regions of the map that are less guessed, like the very light throttle regions that you tuned unloaded, and slowly work up to higher throttle positions and tune.

With the turbo package, we've had our headers glowing (http://www.uow.edu.au/eng/racing/images/lil_left_picture.jpg) a few shades more yellow than red. I wouldn't assume that it's busted, at least not for that reason. You may have destroyed the engine a different way though, such as oil surge (very common).

What pulse width are you running at WOT at mid revs (say 7,000 rpm) and what was the resulting AFR? And what was the ignition advance at that site? You'll likely want to be up around 40 degrees.

Was the 2 foot flame a bright yellow colour? Did the engine sound smooth or did it sound like it was missing? If it's missing even slightly, ignore the AFR reading as it'll be wildly wrong due to the excess oxygen in the exhaust. If it's missing due to being overly rich, you can get afterburn as the unburnt mix is ignited in the exhaust.

[BryanH]

Only retarded ign timing melts mufflers.
You must check base timing at idle and at high rpm (7-8K) You probably have trigger wiring reversed as the engine starts and idles and I assume the timing maps are about right because you seem to know what your on about, and a muffler meltdown needs about 20+ degrees of retard.
Cheers

[drivetrainUW-Platt]

Compression test the thing at least.

If you are running lean enough to cook the muffler then you were probably detonating the crap out of the pistons as well. Takes skill to get a continuous flame out of the muffler.

[Wesley]

I've seen cast-iron exhaust manifolds melted in half from retarded timing.

That would be my very first check.

I doubt the motor is hurt - unless it's a burned exhaust valve. Most times if you're having detonation, you won't have flames out the exhaust because it ignites before the spark gets to it, not after - so the burn completes early, not late. I doubt you're lean.

[james17]

We have a F4i that was run under similar conditions and in general horridly abused over the span of four years and it still ran well. My guess is the same as most everyone elses that it's a heavily timing related issue. I would also think that from what your describing a rich condition with retarded timing would cause an almost constant backfire in the pipe and melt the muffler more then a lean condition and too much timing would. If you wish I may be able to contact someone in our program and get you some info on timing for that motor?

[MrSwa]

I am also with Nabil at UofL. We torn down the motor a couple of nights ago and everything looked ok. Our timing dosen't seem to bee too off from what I've read to be typical for these cars. We start out around 12-13 then ramp up to around 35 at 7k. We're still trying to track down all the problems. If anyone has any sujestions, please let us know. Your help has been greayly appreciated. Thanks

[Poe]

Make sure that you are actually seeing that timing. I'm not sure what system you're using, but from my experience with Motec, you have to have the correct "crip" value to correctly sync the timing. If it's incorrect, the actual timing could be several degrees off from the table values. Check on how this is achieved with your particular engine computer and make sure it is correct (check with a timing light). 35 degrees total timing should be okay, but you could probably advance it even more once you get fueling sorted out.

[Erich Ohlde]

Ok, if I read everything right (it is a bit late) and you guys are mapping the thing right (no offense, but it is a huge assumption sometimes) I'd say that you don't have a fuel problem, but you have an ignition timing problem.

Next, Wesley, The overly rich condition won't register a lean condition. The strange readings from the O2 sensor are most likely due to the high temp of the o2 sensor (because of the retarded timing). Leaning out the map won't help the problem, but most likely make it worse.

drivetrainUW-Platt, good thoughts but I seriously doubt that the engine would actually run if the AFR was lean enough to melt the muffler and make the header glow cherry red. Also, if you were driving the car with detonation there would be case perforation...no question. Detonation will kill a motor in a couple of minutes especially at high rpms and loads from driving a race course.

Wesley again (i'm going down the list of posts) I'm guessing there was engine damage, any EGT's over ~1650F will cause damage, generally it'll be a fatigue failure though, so the exhaust valves will most likely just give out down the line (after the problem has been corrected).

Poe is dead on. I've run an F4i on the dyno up to 70 degrees ignition timing (thats what the ECU said it was) and still making power, when I checked with a timing light the 70 degrees turned out to be more like 45. The problem turned out to be a small sync problem with the ECU. I feel your problem lies with your ECU synchronization (sp?) of your engine.

[Chris Allbee]

So, if i'm not terribly mistaken the PE doesn't really have a timing sync variable to mess with. I know you can choose how many cylinders and what type of ignition (wasted or distributed) and you can then alter the timing advance to a maximum of 50deg. The only other way to affect the timing with the Pe is the trigger wheel installation on the crank, make sure it is installed correctly. The one that PE supplies has only one tooth on it that is supposed to key into a spline on the stock shaft. We have had problems during installation with stripping that one tooth off (not a very close fit) and it rotating the trigger wheel several degrees. Make sure the wheel is installed correctly and undamaged. Quadruple check that you wired in the sensor correctly. Double check the timing with a timing light. If you still have problems contact PE directly, they are very helpfull.

[Kirk Feldkamp]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by jayhawk_electrical:
Next, Wesley, The overly rich condition won't register a lean condition. The strange readings from the O2 sensor are most likely due to the high temp of the o2 sensor (because of the retarded timing). Leaning out the map won't help the problem, but most likely make it worse. </div></BLOCKQUOTE>

I have to strongly disagree with the assertion that WAY too rich can't show up as lean. I have tuned a few engines that have been WAY too rich on the first tuning session (building a base map) that the engine was misfiring, and thus causing a lean readout. An O2 sensor doesn't necessarily measure the "burned mixture ratio"... it's simply looking at how much unburnt oxygen is in the exhaust gas. During a misfire condition, the engine is not using up all the oxygen in the cylinder, and therefore your lambda readings will almost always read lean.

My guess is still along the lines of what you guys are saying... sync issues.

It also can't hurt to get an EGT sensor on there. While not a great direct tuning tool (too many variables have an effect your gas temp), it can be a great indicator that something is wrong - so you can stop and figure out the problem. Had an EGT sensor been on this engine, it would be a lot easier to assess if it was necessary to tear down the motor like they did.

-Kirk

[Erich Ohlde]

good point. but i've been on the dyno with the car running at 8:1 afr (on 100oct gasoline) the o2 was reading correctly and there was a 3 foot fireball exiting the muffler.... this was on the dyno at detroit in 05. the problem was sync issues on the ECU

[Kirk Feldkamp]

That's all well and good... but I wasn't saying that being super rich will absolutely cause a misfire condition, and thus read as lean. Rather, I was taking issue with your assertion that "an overly rich issue won't register a lean condition". I basically wanted to point out that being overly rich CAN cause that, so I wouldn't discount it if you're having those sorts of problems in the future.

[VFR750R]

I can attest that hot O2 sensors will read lean. A hot LSU4 sensor can shift 2.5 points lean almost instaneously if too hot. Remember that the sensor doesn't need to be buried in the exhaust flow, just the tip needs to be into the exhaust. Spacing the sensor out and blowing on the headers/O2 sensor with a fan does wonders for the accuracy. Also, if you are using just one sensor well downstream, say in a collector, you need to watch for exhaust leaks at pipe connections, even downstream.


I don't have evidence to support or not support overly rich showing lean.

[murpia]

Overly rich could still show lean using a standard O2 sensor if:

Sensor hasn't warmed up yet, or is overcooled by the rich mixture.
Air leak into the exhaust.
Unburnt charge in the exhaust (incomplete burns, drastically retarded timing, misfires).

Of course, stoich or lean mixture will show lean under the same circumstances...

Reading the above problems, I also suspect a crank sensor timing issue. The timing light is your friend!

Regards, Ian

[B Lewis @ PE Engine Management]

Hi Guys. I'm getting on this thread a little late, but I would agree that the problem is likely timing related. Give me a call if you continue to have problems.

[Wesley]

Lambda just measures the amount of O2 in the exhaust gas. Thus - if timing is retarded, and fuel burn continues until the end of the tailpipe - as he indicated - you will still have a disproportionate amount of O2 in the exhaust compared to a complete burn in the cylinder - the burn is not only late, but when it suddenly expands at EVO, it slows down considerably.

A lambda sensor doesn't know how much unburned fuel is in there, just free oxygen. (And I know you know this, but just for reference.)

I'll answer your second contention with a quote of myself: "I doubt the motor is hurt - unless it's a burned exhaust valve."

[MrSwa]

We put the engine back together the other night and it seemed to run fine. As for the trigger wheel, we have always had issues with it. We're pretty sure it's on there now correctly. As for the timming issue, how can we "fix" it. I only say "fix" because, we're not even sure that's an issue. How can we check this? Just a timming light? If we do use a timming light, what do we read it on? These may be noob questions, but I'm trying to completly understand the issue before moving to a fix. Thanks for all you guys help so far.

[Erich Ohlde]

we set our timing up light it says in the f4i engine manual. I think it says 13.7degrees at idle, then we checked with a timing light against the stock trigger wheel. i'm not sure how you do it on the PE ecu.

[VFR750R]

It would be really good to find 'true' TDC for the engine. This can be done by making a 'stop' for the piston. You can brake the bottom out of a sparkplug and weld a short bolt to it. Screw it in, with piston at bdc. Now come up with a degree wheel, which you can get for a V8 at many peformance locations or off the internet...or make your own with a plotter, graphing software, matlab ect.

Attach degree wheel to crank and select a point that doesn't move as the pointer (could be case parting line). Rotate engine back and forth against the stop and move degree wheel until stop is same number of degrees before and aft of zero on wheel. Lock down wheel. Take out plug, rotate crank to zero on locked down degree wheel...TDC. Now permenately mark crank, and you have a TDC mark. you also could put marks for say 30deg BTC with the degree wheel or 25 or whatever you want it to be, then with the timing light you can dial in your ECM to get you your 'true' 30 deg and whatever your ecm says is the offset or you could attempt to move your trigger wheel so that 30 in fact is 30.

[Logan S.]

Hello, I am also with some of the guys here at University of Louisville. Just wanted to thank all you guys for the help. We're in the process of trying out some of the timing light ideas. I'm really inclined to believe that our trigger wheel is not where its supposed to be because the same timing map is in a 3 year old car and it runs great.

[Wesley]

It seems like the only way you'd have timing that retarded if you have the map set up correctly - which I believe you do. It sounds like you're on the right track.

Even if the fuel injectors inject 180 degrees off, it'll still run, you'll just give up a few horsepower.

I would agree with VFR's suggestion of a degree wheel. I've been thinking about blueprinting a motor for this years competition (money allowing) and it's always a good thing to have to verify all sorts of things. You could make a tiny one that would fit on the stock trigger wheel if you wanted, it'd just be hard to read.

If the ECU indicates proper timing, it almost has to be a trigger wheel issue. Good luck!

[BryanH]

Logan, I'm not a betting man but after new info in your post will put $2 on the mag trigger wires being reversed, Idle timing will be OK, (which is why it starts and idles) but timing will progressivly retard with speed as the trigger pulse stretches out and the ECU triggers on the sloping edge.
cheers
RMIT fan club

[Korey Morris]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Logan S.:
because the same timing map is in a 3 year old car and it runs great. </div></BLOCKQUOTE>

I was going to ask about your old map, because I know that we (kentucky) have autocrossed against that car a few times. It seemed ok (actually pretty rich when I saw it at fort knox). I second checking your crank pos wiring and trigger wheel installation. I assume that you guys have called brian lewis???

[MrSwa]

The map loaded into our old car is now tuned with the wideband so it's much stronger than it used to be. That being said, we also tried reversing the wires on the crank trigger sensor. The car tried to start, but backfired like crazy and wouldn't ever run. On a "positive" note, we have discovered a fuel problem. The pressure is a 50psi at idle but falls to 35psi when we just rev the motor, not even load it. This has to contribute to lean condition. While it may not be our only problem, it is worth fixing for sure. On that note, has anyone ever used fuel cell foam? It's in our tank and we keep cleaning it out of our fuel filter. This is most likely what's clogging our pump. Anyone know how to get is out without cutting open the tank? Once agian I want to thank everyone for their comments/suggestions.

[Kirk Feldkamp]

Are you guys running e85?

-Kirk

[MrSwa]

No. Just 93 from the local station. We can't get 94 around here.

[Kurt Bilinski]

93?, 94? Pffft, we can't get better than 91 in SoCal.

[rjwoods77]

Mrswa,

I just started my job at Delphi and read through huge mounds or papers and documentation on systems we make. One that really shocked me was the pulsation damper for fuel rails. They showed test data of what the injectors will actually see pressure wise when they are firing with and without a damper. I dont know if this is curable with a large fuel rail volume but that was suggested to me by someone. Every fuel rail we sell to OEM's has a damper on it. I dont know if this applicable to performance engines but my hunch is that it does. Maybe this has something to do with you pressure loss. I cant give you the paper because it is internal stuff but I figured I would mention it as something to research. Good quality fuel foam shouldnt clog up anything. I have found fuelsafe foam to work very well.

[Kirk Feldkamp]

What fuel pressure regulator and fuel pump are you using?

On another note, if you're PUMP is getting clogged, then your pre filter isn't doing its job. Is this a one pump or two pump system? Either way, check/clean/replace your filters. Have you cleaned/flow balanced your injectors lately? RC Engineering in Torrance, CA has a great FSAE discount, and they do 1 day turnaround on injector cleaning. Investigate your filters first, but it might be worth a try in this case if you've found fuel cell foam clogged your pump.

It sounds like you've got more going on than just a trigger wheel problem (if that is even a problem!). Any drop in fuel system capacity/capability can certainly have an effect on your AFR's.

-Kirk

[rjwoods77]

Found this.

http://delphi.com/manufacturers/auto/powertrain/gas/injsys/mpfi/