greddy91

iTrader: (2)

Katech to Ls6 fit like a glove - had to remove the steering shaft and was unprepared for that - so another 15 minutes there. Plug change was planned. Didn't need to remove the oil filter.

Car never ran rough... double check your plugs and plug wires - specifically the wires - I burned through one after a bit and got cool socks to prevent that from occurring again.

The sound is dead on with what mine sounded like through the stock mufflers... and that is freshly raped *******... Change the muffs... but stay away from Bassani please. I like my car being the only one that sounds amazing.

The filter whistle is a gateway drug to a far more menacing whistle coming from the engine bay... embrace the calling.... Join us!

liqidvenom

iTrader: (2)

im still trying to see why the oil filter issue came into play, unless you have some sort of extremely long filter or something.

FuzzyLog1c

iTrader: (4)

Liquid, I use the K&N HP-1007. Pretty standard size. It's possible that I didn't need to take out the filter once I unhooked the steering linkage, but I did both simultaneously, and I'm not about to unbolt the headers just to test that theory.

By the way, I borrowed a friend's OBD2 scanner and found that I am indeed experiencing random misfires when demanding torque from the engine. I wonder if this 95% humidity that we've been experiencing on the coast is exacerbating the issue. When the engine is lightly loaded, it doesn't appear to miss at all.

By the way, I'm still getting a nearly 50/50 split from forum users and real life friends here (sample size: 15-20 people) in terms of opinions on whether I damaged the spark plug wires or simply need a tune and maybe new spark plugs to fix the issue. I'll keep you posted as I work my way through this challenge.

4doorvetteLV

iTrader: (1)

U can test the oil filter theory soon when u put the new clutch in. Everythings gotta come out again :-(

FuzzyLog1c

iTrader: (4)

According to this guide, you don't.

http://www.cadillacforums.com/forums...h-install.html

greddy91

iTrader: (2)

If you didn't do plugs at the same time of the install I'd start there... but from my experience the three "miss" issues I've had have all been wire related.

FuzzyLog1c

iTrader: (4)

To recap earlier this week: I pulled all of the wires and checked their impedance. They're all about ~75 ohms. So it must just need a tune and possibly a different spark plug gap.

meatyCTS-V

I hate for my first post to be like this, but unfortunately I guess this is how it's going to be.

I'm not sure what your history is on modding cars, but I have no idea how you came to the conclusion that modifying your exhaust and intake have in any way affected your engine timing.

Changing your intake and exhaust may/may not cause your motor to run either a little bit rich, or a little bit lean. I can only assume that the caddy should have an ECU that's more than capable of adjusting for that small of a change by either advancing or retarding timing when necessary. (I'm not very knowledgeable about domestics, but this can be true on newer imports).


To solve this problem you have to look at exactly what you did. Maybe your coolant sensor was not properly put back and/or plugged in. (this would not affect ignition).

Maybe somehow you didn't install the headers properly (this again would not affect ignition unless you somehow damaged an ignition component while doing this).

The only thing you really touched was the spark plug wires. Simple solution, replace all plug wires (not that expensive) and replace all plugs with recommended gap. Just because your plug wires have a specific resistance, doesnt mean that they aren't arcing to something in the bay, or grounding out somewhere. Maybe you somehow damaged the wire itself inside the plug wire and doesnt show until in the car, or installed, a bad connection. Double check your install, and make sure nothing is touching where it shouldn't, and that you somehow didn't damage a component of the ignition system, whether it be wiring or a sensor of some kind.

YOU DO NOT NEED A TUNE FOR BASIC HEADERS AND COLD AIR INTAKE. Seriously, stop saying that.

You obviously affected an ignition component somehow with your install that is causing misfires.

A TUNE WON'T FIX THAT.

A tune is for:

(a) major intake modifications, such as larger throttle bodies allowing more air into the intake, therefore needing to richen up the air/fuel mixture to compensate for the added air volume

(b) forced induction

(c) bored/stroked motor/ major motor overhaul

A tune is not going to fix your misfires. It's just a waste of money. A reputeable tuning shop would ask these questions before you even got a tune:

When was your last tune up?
Did you replace plugs/wires (if necessary cap and rotor)?
What size injectors are you running?
What is your target a/f ratio?
Have you advanced/retarded your timing?

If you try to tune a car that's not running properly, it's not going to get a good tune. Any good tuning shop wouldn't let a car that's not running properly and misfiring NEAR their dyno.

-meaty

wcryan

iTrader: (2)

Just wondering. U say a tune is not needed for a normal CAI and header install. But on a car that is running perfect and not misfiring. A tune after headers can still get you higher gains correct?

meatyCTS-V

When a car comes from the factory, it's timing/fuel/spark is set to accomodate for any/all conditions the car may run in. That's the reason why you can take your car and drive from Canada all the way down here to me in Florida. Keep in mind when you go from north to south, there are all kinds of elevation changes in your altitude, there are changes in air temperature, and air density. To keep cars from blowing up, and to save the expense on having cars "tuned" to specific climates, the car is given a general "tune" called your "basemap." This tune is basically there to have the car running reliably in all conditions and environments without it pinging and knocking due to running lean.

When you get a tune, whether it be on a stock car or one that has bolt-on upgrades, or major forced induction upgrades, you put the car on a dyno, and use a programmer to adjust your tune. The dyno allows you to isolate a specific "load" on the drivetrain, to simulate acceleration, cruising, uphill/downhill and other conditions you would experience on the road.

Lets take for example the headers. Depending on the diameter of the runners, when you increase their diameter, it also reduces the amount of backpressure in the system, which in turn reduces the amount of low-end torque you have on tap, but in return, the motor will breathe easier in the higher RPM bands. You can effectively "tune" your torque/hp curve with different header/exhaust designs, moving the torque/hp curve up and down for more topend power or more lowend power.

http://www.superchevy.com/technical/...exh/index.html

When you tune, you can advance the timing at the low end, to help negate the decreased back pressure to try and regain some of the torque loss, and then in the upper end, you can retard the timing to prevent the motor from knocking and pinging from the advanced timing.

Depending on how conservative the "tune" is from the factory, depends on how much of an increase in power/torque you can tune out of your stock motor and ECU.

On the Miata, with just the stand-alone Megasquirt plug and play ECU, people have been able to tune an extra ~20hp out of a stock motor. People have also said that there is a night and day difference in a "stock" car and one that has been tuned with a fully programmable Megasquirt ECU on a dyno.


On classic FB Mazda RX-7's (first gen) Just changing out the exhaust would net you on average a ~22% HP increase at about 7000 RPM. But that's comparing apples to oranges (rotary to V8). The new RX-8's, while being a Rensis rotary, are so finely tuned from the factory, that the usual bolt on upgrades for it don't net nearly as much of a power increase as the classic RX-7's, despite still being a rotary motor.

Hope that helps somehow?

-meaty

wcryan

iTrader: (2)

yessir. Thanks. So my answer is yes. Correct me if I am wrong

-T-

iTrader: (2)

One strand internal of your entire plug wire cable can give you your 75 ohms of resistance. That however does not indicate that it is capable of handling the current and higher voltage. Your meter is 9 volts and measuring 75 ohms. Your ignition charge is far greater and could pose for an increase in resistance when attempting to fire. Change the wires and plugs man. 150 bucks is cheaper than a dyno tune.

JNR_Design

iTrader: (3)

While I agree that an oem's ECU "program" is "tuned" to a wide array of what the manufacturer deems will be the entire car's range of scenarios (read: generic), every engine and every car varies just enough to deem a fine "tune" a benefit. Change the characteristics (i.e. more efficiency in the exhaust) and this becomes even more true. The MAF system is good for 'learning' to a degree (vs. SD), but if you can hone everything in optimum to the environment and conditions (i.e. DD, 91 octane only like here ) you will mostly be doing, then it could be worth it...Do you *have to*, no, but if you want 100% (so to speak) efficiency in your setup, then start with making sure it's 100% up to "tune" (not talking the ECU, mechanically speaking) with things such as plugs, wires, fuel and air filter, oil and so on...don't forget to clean out the combustion chamber from time to time, as well, plus the other maintenance items like drivetrain fluids, coolant and so on.

OP - you said you dropped a plug...replace it to be sure. It may *look* OK, but may be damaged, not allowing the current...At night, start your engine and let it run; look for arcing to start with...However, plugs are not that hard to change on this car (with good tools and some common sense) so do that. Doesn't hurt to change the wires if it's within budget and you have some miles on the car...

also, being they are chinese (headers), are you sure the gaskets are good and the flanges flat and straight? thinking if there is a leak somewhere near the comb. chamber or pre-O2, could cause issues...Did you double check the torque on all the hardware? You should also retorque after a few heating and cooling cycles, as there are different rates of expansion (alum more than steel for instance) and so on...

meatyCTS-V

JNR touched on something I didn't, which is also good information. Every car IS different. Especially when you add electronic components.

If you ever watch those racing SPEC series (I.E. spec miata, spec e30 bmw, etc) you will notice that even though there are rules that very tightly regulate the cars, basically making them all the "same," there are some cars that seem to be faster. (as long as they're not cheating, but we wont get into that...)

When you build a spec car, typically the builder of the car has a bin of every part that can be used to affect ignition/timing, airflow, ECU, etc.

For example, he will swap out ECU's while the car is on the dyno, and see which one puts out just that little bit of extra power, or which one has a better power curve. He will then go to the MAF meter, and begin the process all over again, and find which MAF produces more power with that ECU, coil packs, and on and on and on, until he finds all the electronic parts that produces the most power in that car. And while one part might not make a difference in *that* car, it could make a difference in another.

Amazingly enough, even though all these parts are theoretically "the same," they can be vastly different, giving someone an edge. This is "old school" tuning when you can't use a programmable ECU for your application, like in SPEC racing.

Will someone benefit from a tune? Sure, but is it necessary? No. Especially not when your car runs like crap.

My buddy runs a speed shop, and he said probly 7 times out of every 10 dyno's, he finds himself doing a complete tune-up on the car before even putting it on the rollers.

Stuff has changed a lot since the days when you adjust your distributor and tweak your jets on your carb...

Hope some of this stuff helps.

-meaty

98cobra

iTrader: (32)

Actually putting headers and an intake can affect the timing. Different airflows will move the timing into different spark cells in the tune. I rally doubt it would be enough to cause a misfire.

meatyCTS-V

People have been doing Intake/headers/exhaust on cars for many, many years and have never really "needed" a tune. But would a tune have been beneficial to squeak even more power out of those mods? Of course. Necessary? No.

I think the Caddy would have an ECU that would automatically be able to advance/retard timing to accomodate any changes that these bolt ons would cause (preventing the car from knocking/pinging or running excessively rich). I haven't bothered to look into it, but I know after 2000 on Miata's, adjusting the Cam Angle Sensor went out the window as far as a budget "mod" for a few extra HP, due to the ECU controlling timing advance/retard.

-meaty

JNR_Design

iTrader: (3)

Yeah Meaty, I agree with most everything you're saying and guess I should be clear in that while it can be most beneficial, is it worth the $$$ the 'shops' charge on a pretty close to stock car? Probably not...But, if you had say HPTuners and knew what you were doing and could do some realworld testing, it would probably be worth the effort.

In my experiences, I've found that keeping a car in tiptop shape (mostly with maintenance and not abusing it), along with the 'details' part [like taking the time to maybe clean up some restrictions (although this car doesn't have a whole lot)], while avoiding the 'names' (just to have them 'cause everybody else does and throwing parts on a car without doing anything else) it has made most all of the cars I've owned run their best, get good mileage (for what they are) and very reliable...Of course, I would love headers and maybe heads and all the other goodies that go with it, but I am finding to be pretty content with the car stock. Someday I may dive into it with mods, but nothing too crazy as for some reason, I have a hard time justifying the $$$ at this point (but have spent plenty of cash on plenty of mods before )...the most important thing though, to me, on this car is just getting the shortcomings taken care of...things like the mounts and so on...Wouldn't mind getting some SS brake lines soon and a few other not so much for the performance, but upgrading stuff...I just hope it stays as good as it has been so far, for a DD...If this were my only car, I think things would be different, as far as spending more time and money, but for now...

I think it's cool to modify them though (so long as it's not a hack job) and the potential is there...Just take it one step at a time and do a lot of research (beyond the forums; although this one is pretty good) and shop around and it makes it really enjoyable.

vmapper

iTrader: (8)

Correct. Even just changing to a K&N filter changes airflow characteristics and tuning is available on the table... Greg Banish clearly demonstrates that ANY airflow modification (intake, engine to exhaust) changes LTFT on his GM dvd or books.

Though this has nothing to do with the misfire discussion in this thread, I wanted to point this out.

FuzzyLog1c

iTrader: (4)

Just a quick update: I've talked to three tuners, and they all think that the engine is sporadically misfiring under low RPM, torque demanding situations because the fuel/air mixture is being driven extremely lean due to the lack of cats (the ECU is trying to compensate).

JJSimon904

iTrader: (8)

^ Impossible. The rear O2 sensors only sense that the cats exist. They do not affect how the car runs so not having cats has zero to do with misfires. Yes it can run a little lean but not enough to cause that problem. It will throw lean codes long before having that problem. You are getting a lot of GREAT advice here but keep ignoring it. Why even ask?