"Heat Bog"?

[MtnHome]

I'm confused by a couple of recent threads:

"Rough idle / Stall / Misfire"
http://forums.s2kca.com/showthread.php?t=13916

and

"Running Rough!! Please Help
http://forums.s2kca.com/showthread.php?t=16758

At first, I thought the behaviors described in those threads might be at least related to the dreaded "heat bog" that I've read so much about. But then the discussion got way more technical than that subject would normally entail.

Given that this time of year many of us have some heat bog symptoms now and then, could you briefly explain any connection (or lack thereof), Dave? I know you've led a very good discussion of intake temperatures and how to lower them (with both insulation and a CAI) somewhere; what I'm after here is whether this latest stuff is connected to that or not. Thanks, HPH

[raymo19]

:bump:

I'd like to hear this too.

[medicalstudent]

When I installed the Mugen cooling mods (thermostat, fan switch) + Mugen N1 ECU, the heat bog was signficantly reduced (I can attest to this where it's very hot and humid during the scorching Texas summers. I have driven the car stock for 2 years before throwing on these mods. So far, I've been impressed 3 summers later after installing those mods.

I would still like to hear Dave's thoughts.

[desmo4]

I did the same thing with the same results. I can't understand how people can argue with success.

Jonathan

[repiv]

Initially, both those threads led me to believe it was heat bog related. However, some of the symptoms disclosed later in one of those threads would hence lead me to believe that, at least in the one instance, there was more to it than just a matter of heat issues. There may, in fact, be mechanical issues at work.
Having said this, it is extremely difficult to relay over the printed medium, exactly what's going on here. I still cannot determine the "EXACT" conditions (of operating conditions and driver input) at the time these symptoms arise. The posters themselves seem to post conflicting information at different times and therefore, it becomes even more difficult to come to a concrete assessment of the situation. My offer to do a test drive when I go to the Garden State meet was largely ignored. First hand experience with these cars has usually netted a fairly concrete conclusion. However, the answers are not always what the owners have wanted to hear.

Heat "bog" or similar related effects on performance is not a mechanical "problem" as such. It's merely a very high strung engine responding the best way it can to the environmental conditions that it's subjected to. In almost all such cases, the symptoms can be circumvented with mods (such as what Desmo and MedStudent did - cooling mods) or by an adjustment in driving technique (as what I and most other people do). We have a choice.
I've eluded to this driving technique before but I'll outline it here again. (BTW, this driving technique is not restricted to S2000 owners. Many other kinds of high performance manual cars behave like this in hot conditions.)
Heat bog is simply the accummulation of very hot air in the intake system. It moves so slowly during times of stop and go traffic (low engine speed) that the walls of the induction path can easily heat up the air as it goes through. As we know by now, hot air has much less oxygen and less oxygen makes for a less efficient combustion. Engine management systems are designed with this in mind and hence, responds to sensor input that tell of high intake temps and pulls timing. This, consequently, moves the powerband up the rpm curve just a wee bit.
We can then do one of 2 things to compensate:
1. Where we used to call upon XX ft/lbs of torque to get the car moving at say, 1500 to 2000 rpm, we must now go to 2500 to 3000 rpm to find that same XX ft/lbs. Moving off at the same rpm as before, there is insufficient torque and power to motivate the car and that's when you experience the lack luster performance and in some cases, the load when the torque suddenly becomes absent, sends the rpm very close to idle. This results in that surging up and down (bucking) that is very embarassing to witness. It will continue to buck till the rpm can climb enough to stabilize or until the operator pushes the clutch in and remove the load. Those who understand what's about to happen, can either stop it immediately by pushing the clutch in and starting over again with higher revs or by simply using higher revs to begin with. The mistaken use of more and more throttle to get the thing going smoothly and briskly, only fail in that now you are asking the engine to use more air and fuel than it can handle, given the close proximity to the lugging threshold. With timing pulled, the engine simply cannot deal with the extra air/fuel. Then the knock sensor comes into play and even more timing is pull. It becomes a "Catch 22" until the vicious cycle is stopped.
2. A few seconds before moving off, you can clear much of the hot air from the induction path by revving it up slightly. Blipping the throttle as many people do is NOT desireable as this induces too many sensor inputs to the ECU, thereby causing that brain fart and resulting in the drastically low idle slump that shakes the engines and sometimes causes a stall.

This is not an automatic car. Automatics have that great big torque converter to absorb a lot of the up and down surges of engine output. It can mask a lot of inefficiencies of driver technique. This also a very high output engine. Engine management and engine design is the way it must be to get that output and still have a street driveable car. Timing and valve settings (even before VTEC) must be aggressive and on the edge of streetability. Any dramatic changes in operating conditions, such as extreme heat, makes the little Pixies inside the ECU scramble around trying to keep the engine running as best it can. Then you add in a ham-fisted (or footed) operator and things can get quite difficult. Some people have always said that for this kind of money, the car should not do these things. Sorry, but we own a car with an power train that is very close to a race car. They say that their "Brand X" car never does this. Well, does their "Brand X" car put out 120 bhp/liter AND rev to such high rpms? Does your 3L V6 NA engine put out 360 bhp? Not likely. Even the mightly Elise can't boast this. It is what it is.
The happy owners are those who understand this and adapt. This is not a car that was made to adapt to the owner. It is one that the owner must take some responsibility to adapt to it.

[MtnHome]

Thank you! I confirms what I was thinking and clears up my confusion. And, indeed, diagnosis via this rather clunky print medium must be an equally clunky process.

I'm interested in this topic because, here in the South Florida summer, I've experienced this problem with hot intake temperatures while accelerating away from stoplights, particularly in traffic. It finally got bad enough that I decided to do something, and I took the first, and obviously easiest, step. I put in a K&N air filter.

Now, the OEM filter I replaced had 13K miles, all on paved roads, mostly down here where the air is pretty clean. Still, I suppose it may have been mucked up. Maybe, just maybe, a genuine, new Honda air filter would have had the same effect.

In any case, I've yet been able to reproduce the irritating symptoms with this new filter. This isn't to say that all is fine, and I certainly wouldn't claim I've got more power. But the car sure revs better and doesn't hesitate at all even on smooth, low-RPM starts. I'm sure I haven't really solved the air-intake problem, but the car seems to be breathing easier.

(I considered the K&N filter/intake combo, but the installation instructions had too many steps for me to want to deal with. Like I said elsewhere, I'm just too lazy.) I do have a cabin filter coming by UPS soon, and when I replace that I'll look at taking off that rubber rear hood thing that's been talked about to let the hot air out more easily. HPH

[desmo4]

Perhaps the Mugen ECU also has an influence to avoid this heat bog. As it starts with significantly more initial timing advance the the stock one. And has a much smoother acceleration from a stop in general as well.

Jonathan

[Geo02s2k]

Thank you for the excellent write-up. I have experienced this a couple of times after driving my son to school (highway for a couple minutes warming up the engine followed by sitting in line at the school). My idle would occasionally drop dangerously low after pulling forward a car length or so and I did the bucking routine once or twice as I tried to leave the school. (Not really a place that you want to rev the engine too much.) I think I have learned a lot about what to do in these situations and how to prevent future recurrances.

[repiv]

Perhaps the Mugen ECU also has an influence to avoid this heat bog. As it starts with significantly more initial timing advance the the stock one. And has a much smoother acceleration from a stop in general as well.

Jonathan

This may indeed be the case, however, it would be very interesting to see the hp and torque dynos for both side by side. Where there are improvements in one area, it makes you wonder if there has been a sacrifice made in another. To have that much more timing to begin with, it may have to close the safety margin that the OEM mapping has when knock approaches - a safety margin that Honda may not have wanted to erode for reasons that only Honda would know for sure. I'm only citing this one hypothetical point. It may not bear any relevence to the current discussion and there may be other points that do. I would have to be a tuning expert to discuss it in a more meaningful way and I'm not such an expert.

[repiv]

I think I have learned a lot about what to do in these situations and how to prevent future recurrances.

I sincerely mean it when I say, "Bravo!" It is so gratifying to see that the light has dawned for others and not just me. I can't quite believe sometimes that I'm the only one who has figured this out. Many people drive a certain way and they never have such issues. Those people may not think it's anything special and just go about their day.

[IMPETUS]

Is this 'problem' associated with the '05 and earlier models? Ive yet to notice anything of this sort with my '07.
However, I just installed my Fujita F5 last night and perhaps its just me, but when the underhood temps rise, it does seem to have a smoother throttle response and a slight increase in power at about 3/4 throttle. Never had any 'issues' before this though.

[repiv]

Is this 'problem' associated with the '05 and earlier models? Ive yet to notice anything of this sort with my '07.
However, I just installed my Fujita F5 last night and perhaps its just me, but when the underhood temps rise, it does seem to have a smoother throttle response and a slight increase in power at about 3/4 throttle. Never had any 'issues' before this though.

I can't comment on this. Perhaps Honda did modify the ECU programming to address this issue. Maybe they took a few hints from Mugen.
You must also consider that your 2.2L motor has a bit more "grunt" (torque) to start with. So this, in conjunction to something that Honda may have done to the programming, has minimized the situation.

[Hondassport]

I suggest you guys try this,it worked great for me.Reduced my intake temp 30°. Hi Dave...Pete http://www.s2ki.com/forums/index.php?showtopic=315015&st=0

[desmo4]

Shortly I will be installing an air temp. sensor in the airbox. Once I have some data I will post it. I also have the stock ECU so as time permits (ambient air temp high) I will see if it makes any difference.

Jonathan

[alvanderp]

While I dont mean to poo-poo your idea, I think an Air Temp Sensor would do better closer to the intake ports on the head. You would get a much better representation of acual IAT's. The air is going to be much cooler at the airbox inlet than it is at the head. Of course, this means drilling your intake manifold, which most wouldn't want to do ;)

But maybe put the sensor closer to the TB inlet?

[Hondassport]

The S2k comes with a Intake Air Temp sensor installed all you need to access it is a OBD2 reader...Pete

[desmo4]

No offense taken. I was actually going to put it on the aluminum airhorn of the Mugen airbox first. And then move it around to get a profile at several points. It's not going to be a permanent installation. Just an experiment.

Jonathan

[Hondassport]

Sorry I didn't understand......Pete

[S2KAP2]

Garage Defend radiator plate and a K&N.......works for me, i have an 04

[medicalstudent]

This may indeed be the case, however, it would be very interesting to see the hp and torque dynos for both side by side. Where there are improvements in one area, it makes you wonder if there has been a sacrifice made in another. To have that much more timing to begin with, it may have to close the safety margin that the OEM mapping has when knock approaches - a safety margin that Honda may not have wanted to erode for reasons that only Honda would know for sure. I'm only citing this one hypothetical point. It may not bear any relevence to the current discussion and there may be other points that do. I would have to be a tuning expert to discuss it in a more meaningful way and I'm not such an expert.

Thanks for the excellent reply! The 2 sacrifices that you alluded to I think are: 1) increased requirement in octane 2) fuel efficiency. (there may be more...)

Some owners will scream until blue that fuel efficiency is unchanged, but I have found that fuel efficiency is reduced. With OEM ECU, City/Hwy was ~20/25. With Mugen ECU, City/Hwy is ~18/23.

If I am not mistaken, the Mugen ECU requires at least 92 octane. While some Californians have ran it ok with their 91 premium, this does not pose a problem for areas like mine that has 93 octane or Japan that probably has higher octane fuels.

I would not recommend this ECU unless you live in hot and humid climates like in Texas. Otherwise, Dave's recommendations on adaptation should suffice.

[desmo4]

I lived i CA and the Mugan ECU will not work on 91 octane, it will knock under the slightest throttle pressure from a stop.. Scott at King told 93 minimum and the folks I met who had them were either buying drums of Elf or driving to Sears Pt., like me, and buying 100 octane unleaded and blend it with 91.

Jonathan

[medicalstudent]

I lived i CA and the Mugan ECU will not work on 91 octane, it will knock under the slightest throttle pressure from a stop.. Scott at King told 93 minimum and the folks I met who had them were either buying drums of Elf or driving to Sears Pt., like me, and buying 100 octane unleaded and blend it with 91.

Jonathan

Does the car run signficantly better at octane ratings>93? I've always debated about running higher octane at the track, but the car seems to run smoothly at 93 though.

[desmo4]

Thanks for the excellent reply! The 2 sacrifices that you alluded to I think are: 1) increased requirement in octane 2) fuel efficiency. (there may be more...)

Some owners will scream until blue that fuel efficiency is unchanged, but I have found that fuel efficiency is reduced. With OEM ECU, City/Hwy was ~20/25. With Mugen ECU, City/Hwy is ~18/23.

If I am not mistaken, the Mugen ECU requires at least 92 octane. While some Californians have ran it ok with their 91 premium, this does not pose a problem for areas like mine that has 93 octane or Japan that probably has higher octane fuels.

I would not recommend this ECU unless you live in hot and humid climates like in Texas. Otherwise, Dave's recommendations on adaptation should suffice.

I agree mostly about the efficiency. I just measured 26 mpg on a 200 mile trip of freeway and traffic jamb mix. I was surprised. But is normally 20-23. But I didn't get the Mugen ECU to improve gas mileage. I bought for the noticeable power gains. The two mods I have done where I don't need a dyno to confirm power gains are the mugen headers and ECU.

Jonathan