Kooks Headers / O2 sensor issue?

[shagdrum]

From Sean Hylands book:

Most header manufacturers place the oxygen sensor bung into the collector...Unfortunately, the collector on a long-tube header takes forever to get up to operating temperature. the engine operates in open loop until the oxygen sensor is up to temp, and even then, the sensor is so far away from the engine, much like a long distance telephone call. We have taken to moving the oxygen sensor up into one of the primary tubes, as close to the cylinder head as possible. while it is true that we only see one cylinder, the respons of the engine is much better, and drivability is much improved. Ford used this technique in the Contour SVT.​

Has this been an issue with the Kooks headers? Has anyone who used these headers reported a drivability issue, or a loss of gas mileage (that wasn't just due to a lead foot)?

What has been the experience with the Kooks?

 

[MonsterMark]

What has been the experience with the Kooks?

I'm going to take a look at that issue.
Makes alot of sense to me.

I'm going to do an experiment over the next couple of days and get back to you.

 

[Joeychgo]

I havent noticed anything. But when I put my headers on I did a number of other things at the same time so it's possible that I wouldnt notice.

 

[Eagle1]

I just got my car back from a rebuild, and put the Kooks headers on. Unfortunately I also made some other upgrade changes at the same time, such as a dynomax exhaust, CAI, high flow cats, and chipped the motor, and I am still getting used to the change in the set up. Normally when doing modifications I prefer to do them one at a time and thus better sense what returns those mods do, or do not, give. But this time I was doing a remanufactured engine swap, and felt that as long as that was going to have to be done, I would do all the stuff I like at one time and save on the time and labor of a seriatim upgrade program. (As long as we have the motor pulled, what else can we do while we are in here!). I have not noticed the above issue so far, but I will look into it also and see what gives.

 

[shagdrum]

I'm going to take a look at that issue.
Makes alot of sense to me.

I'm going to do an experiment over the next couple of days and get back to you.

Thanks! I look forward to reading what you find.

 

[shagdrum]

I havent noticed anything. But when I put my headers on I did a number of other things at the same time so it's possible that I wouldnt notice.

Yeah, I figured that would be the case for most people.

 

[shagdrum]

I just got my car back from a rebuild, and put the Kooks headers on. Unfortunately I also made some other upgrade changes at the same time, such as a dynomax exhaust, CAI, high flow cats, and chipped the motor, and I am still getting used to the change in the set up. Normally when doing modifications I prefer to do them one at a time and thus better sense what returns those mods do, or do not, give. But this time I was doing a remanufactured engine swap, and felt that as long as that was going to have to be done, I would do all the stuff I like at one time and save on the time and labor of a seriatim upgrade program. (As long as we have the motor pulled, what else can we do while we are in here!). I have not noticed the above issue so far, but I will look into it also and see what gives.

Yeah, I am thinkin I might need a new engine in the next year or so...might as well add headers while I am at it. Just wanna make sure I am not gonna hurt performance, drivability, or gas mileage.

 

[MonsterMark]

I'd love to move the bung but I am going to be selling off the whole exhaust system anyway so why bastardize it.

But I will compare cold start up and the 'open loop' situation.

Be careful on mods if fuel economy, etc are at the top of the list.

Gears will hurt mileage, don't care what anyone says.
Converter will hurt mileage, don't care what anyone says.
Bigger injectors will affect driveability to a point.

Headers affect back pressure and will cost some low end to gain some middle and high end.

List goes on and on.

 

[shagdrum]

I'd love to move the bung but I am going to be selling off the whole exhaust system anyway so why bastardize it.

But I will compare cold start up and the 'open loop' situation.

Be careful on mods if fuel economy, etc are at the top of the list.

Gears will hurt mileage, don't care what anyone says.
Converter will hurt mileage, don't care what anyone says.
Bigger injectors will affect driveability to a point.

Headers affect back pressure and will cost some low end to gain some middle and high end.

List goes on and on.

Yeah, I ruled out gears due to gas. I may still install an LSD. These cars can't really stand to lose low end torque unless you can get out of that low end quick with gears and/or a high stall TC; both of which I have ruled out. So...what do you recommend? Shorties? Cat back? There is no smog or emissions testing here in Kansas (unless you are moving into the state) So I can gut the cats. Gettin this car to produce a little over 300 hp and 300tq would be enough for me (300 is a nice, round number, right? )

Still need to get back that Lincoln ride (that I switched from when I sold my Town Car); havin issues there...

 

[MonsterMark]

Yeah, I ruled out gears due to gas.

What is your split City/Hwy driving?

I'd start there.

If mostly city, I'd do gears. Even without the posi. The car will just react better.

I think high stalls suck. They create too much slip and eat gas. Great for launching the car but that is about it. For everyday around town, they suck.

A chip is not a bad investment for a bit of a gain. Mostly comes in the form of a better trans shift. Not so slow and slippery.

A Cobra intake and exhaust will relaly help the middle and upper ranges. The black car pulls so hard on the top hard. The stock white '98 is not even close. But driveability is so much better on the stock white one.

You start doing lots of mods and you will change the character of the car for sure.

I'm ADDING weight to the black car with suspension and subframe reinforcements to stiffen it front to rear. Hope for a better weight distribution which should aid in handling.

 

[shagdrum]

What is your split City/Hwy driving?

I live just outside of the city. I also travel to surrounding cities pretty often. So I do a good amount of Highway driving. Couldn't tell ya the split, but it is a large amount. I still wanna put in a posi. I might consider a mild gear change then, say 3.27 (car is a base Mark VIII), or 3.55. I originally wanted to do 3.73.

A chip is not a bad investment for a bit of a gain. Mostly comes in the form of a better trans shift. Not so slow and slippery.

I've been thinkin about that...

A Cobra intake and exhaust will relaly help the middle and upper ranges. The black car pulls so hard on the top hard. The stock white '98 is not even close. But driveability is so much better on the stock white one.

Yeah, I was lookin into the intake, but it seems that it might be more trouble then its worth. This is for a 1996 Mark (Gen 1), and I haven't found too much info for swaps into Gen 1's. One post suggested there might be fitment issues (under the hood)? How much work is involved in putting that intake in? Does it hurt low end at all? Also, what do you recommend for exhaust? Gut the cats (for off road purposes only )? Don't wanna hurt low end torque here, as the car is an everyday driver.

I'm ADDING weight to the black car with suspension and subframe reinforcements to stiffen it front to rear. Hope for a better weight distribution which should aid in handling

I made a rear shock tower brace for the car, and have the front lower engine control brace on order. The front suspension has been completely rebuilt, and I have the parts to rebuild the rear suspension (just waitin for a good day or two). The car still seems rough to me, though replacing all the bushings in the rear may help that. How does sensor lowering the car affect it?

 

[MonsterMark]

I live just outside of the city. I also travel to surrounding cities pretty often. So I do a good amount of Highway driving. Couldn't tell ya the split, but it is a large amount. I still wanna put in a posi. I might consider a mild gear change then, say 3.27 (car is a base Mark VIII), or 3.55. I originally wanted to do 3.73.

If you do alot of highway, you'll miss the 3.07's with their long legs.

If you do do gears, go with the 3.73's or don't bother.

Do a chip 1st or a dyno tune before screwing around with the intake. For the cash, I would do a dyno tune. Plus you get a neato piece of paper that says hp and trq.


I'd leave the cats alone. I haven't seen anyone pick up power. If you wanted to pull the heads, you could port match the exhaust and polish them. That would certainly help.

The braces are a good idea. The more the merrier with this chassis.

Lowering the car involves putting LESS pressure into the bags. Less pressure, lower level. This also means that the car has less ability to support itself over bumps and the suspension will travel alot more, wearing out the suspension and steering components sooner. I would also recommend a 4 wheel realignment if you lower the car. Also, before lowering, I would loosen all the bushings connected to the UCA and LCA's, and re-tighten after lowering.

Btw, which engine cradle brace did you get?

 

[shagdrum]

Btw, which engine cradle brace did you get?

super coupe performance

...didn't know there were others available

 

[shagdrum]

Lowering the car involves putting LESS pressure into the bags. Less pressure, lower level. This also means that the car has less ability to support itself over bumps and the suspension will travel alot more, wearing out the suspension and steering components sooner.

Wouldn't that also mean a smoother ride?

 

[MonsterMark]

Wouldn't that also mean a smoother ride?

IMHO, no. Some guys like the lower ride characteristics but understand that their is less pressure in the bag. It would be like putting a thinner or lighter spring on. The shock has to work that much harder.

I guess you could call floatier = smoother but the car and the suspension was engineered to perform optimally at the original factory ride height.

 

[Roadboss]

The headers Kooks offers for our cars are mid-length and they perform very well on my car. I do not have a start problem. If you note they are about 4" from the collector flange, which gets them pretty close to the tube.

 

[shagdrum]

The headers Kooks offers for our cars are mid-length and they perform very well on my car. I do not have a start problem. If you note they are about 4" from the collector flange, which gets them pretty close to the tube.

What about over all drivability? Low end torque? how are those affected?

Super coupe performance sells these, and this is what they say in the item discription:

The 3/4 length design will augment low end torque...​

Also...

Because these headers are significantly longer length than the factory manifolds, they require Oxygen sensors with longer leads​

 

[Eagle1]

I did a little digging on some other forums, and found a nice write up by a lad that had modified his Miata with some headers and found all manner of frustration with bogging and lurching, especially when running cold. When he switched his sensor to a heated four wire unit, joy and performance both returned. Here is part of his write up. I am not sure if this is going to help you, but I can tell you that my header set up uses a heated sensor and it runs just fine.

_________________________________________________________________




Platinum/Zirconium dioxide oxygen sensors (1, 3, or 4-wire) require that they be heated to a minimum of 662°F before they will produce any output signal (below this critical temperature they behave as a fairly large value resistor), and need to be in the range of 975°F to 1200°F to be operating optimally. This creates a problem when the sensor is located too far from the exhaust ports, or relocated further "downstream" from the exhaust ports as is common with most if not all aftermarket headers designed for the early Miata. Heated O2 sensors (requiring 3-wires) were designed to keep the sensing element heated to it's optimal temperature--the 4-wire sensor adds the benefit of a dedicated output signal ground wire (1 and 3-wire sensors use the exhaust system as the signal ground path).

With my 4-2-1 OBX header (an unashamed clone of the Racing Beat 4-2-1 design) the O2 sensor is located over 18" further from the exhaust ports than with the OEM header. This means that at times of low engine output such as idling and low power acceleration the sensor's temperature can drop out of the optimal range, and even below the functional range--this results in the ECU thinking that the engine is running lean. The ECU then compensates for what it thinks is a lean mixture by making the air/fuel mixture richer (more fuel) to what is really an overly rich mix; causing bogging and at times an actual "flame out" as the over-rich mixture won't ignite.

Heated (4-Wire) O2 sensors overcome this problem by including a 12V electric heating element (#8 in this diagram) within the sensor. These heating elements (typically 25W or so) keep the sensor heated to 1100°F or and therefore smack in the middle of it's optimal operating range.
_______________________________________________________________

I hope this is useful to you in your searching for a solution.

 

[shagdrum]

I did a little digging on some other forums, and found a nice write up by a lad that had modified his Miata with some headers and found all manner of frustration with bogging and lurching, especially when running cold. When he switched his sensor to a heated four wire unit, joy and performance both returned. Here is part of his write up. I am not sure if this is going to help you, but I can tell you that my header set up uses a heated sensor and it runs just fine.


...I hope this is useful to you in your searching for a solution.

Thanks! That is helpful! If I remember correctly, the from to sensors on our car (before the cats) are the 4-wire ones, so we should be good.

Now, the only question I have is, how do these headers effect low end torque? As noted in my previous post (#17), they are supposed to "augment" low end torque. However, MonsterMark said in post # 8 of this thread:

Headers affect back pressure and will cost some low end to gain some middle and high end​

Is that just his experience with these specific headers, or have others had this same issue?

If I am not gonna lose low end, I will get headers, otherwise, probably not.

 

[MonsterMark]

Headers affect back pressure and will cost some low end to gain some middle and high end​

Shag,

I haven't been able to find the dyno sheets where my opinion came from.
They definitely do make power. I just thought they moved the curve higher and farther down the revs.

Anything above 3000 rpms and you will be ahead of the game for sure. It was under 3000 that I was talking about.

For torque on the low end, you need scavaging. Headers are designed to create less back-pressure. And especially with cat deletes I can't see how that could help low end torque.

If anybody can post up something definitive, I'll concede the point but from memory and driving around, you definitely won't gain low end. Maybe at best keep it the same. Mid-range and upper end you will most certainly feel the motor pull harder, just like when you remove the stock mufflers for straight pipes or flows.

 

[shagdrum]

Shag,

I haven't been able to find the dyno sheets where my opinion came from.
They definitely do make power. I just thought they moved the curve higher and farther down the revs.

Anything above 3000 rpms and you will be ahead of the game for sure. It was under 3000 that I was talking about.

For torque on the low end, you need scavaging. Headers are designed to create less back-pressure. And especially with cat deletes I can't see how that could help low end torque.

If anybody can post up something definitive, I'll concede the point but from memory and driving around, you definitely won't gain low end. Maybe at best keep it the same. Mid-range and upper end you will most certainly feel the motor pull harder, just like when you remove the stock mufflers for straight pipes or flows.

Was is a definite lose of low end torque, or mainly a large increase in the "above 3000 RPM" range that made the low end seem to lose some?

I trust your judgement, but I wanna make damn sure there is a big negative in an area I am concerned with (low end torque), before I rule headers out.

also, do you know of any mods to increase low end torque (besides a whole custom rebuild from the ground up)?

Thanks for all the inpt too, MonsterMark...

 

[MonsterMark]

also, do you know of any mods to increase low end torque (besides a whole custom rebuild from the ground up)QUOTE]

Well 4.6 4V aren't exactly torque monsters to begin with.

I know you were worried aboutgas mileage but some gears might be the answer. Even without a posi rear end. Some 3.73's will help the car feel peppier by getting it up into the powerband sooner. City mpg might actually get a bit better. Hwy will probably drop 2-3 mpg.

You can get a chip or do a jmod for some more tranny response.

Replacing the stock mufflers with some magnaflows or similar will make the car sound faster.

 

[shagdrum]

Well 4.6 4V aren't exactly torque monsters to begin with.

I know you were worried aboutgas mileage but some gears might be the answer. Even without a posi rear end. Some 3.73's will help the car feel peppier by getting it up into the powerband sooner. City mpg might actually get a bit better. Hwy will probably drop 2-3 mpg.

You can get a chip or do a jmod for some more tranny response.

Replacing the stock mufflers with some magnaflows or similar will make the car sound faster.

Not too concerned with sounding faster.
I know OHC multi valve designs are notorious for bad low end torque. I just wanna maintain the low end I have or improve on it, as well as improve the mid and upper range RPM performance, and maintain drivability. Gears seem kinda like a half-ass solution; "get out of the low end as quick as possible to get to where the power is focused".

Either way, with the Mark being my only vehicle and a daily driver, mixed with my current financial situation (college student) i can't afford to get gears and lose the MPG's (thanks to the enviromental lobby).

 

[Roadboss]

There is no real benefit to go with headers unless you plan on doing some additional mods that reap the benefit of headers. True dual exhaust along with a quality chip and tune will yeild more results and be easier on the wallet and "greener".

 

[shagdrum]

There is no real benefit to go with headers unless you plan on doing some additional mods that reap the benefit of headers. True dual exhaust along with a quality chip and tune will yeild more results and be easier on the wallet and "greener".

I would be combining the headers with a new exhaust setup, and probably a chip.