do longtubes on a street car = surging?

rockin_rick · Dec 9, 2003

Does the distant placement of the oxygen sensor on long tubes, cause driveability problems on a 100% driven street car? I've searched around, and most people recommend long tubes over shorty's. But I've noticed a few saying that with long tubes you can experience surging because the O2 is too far away and cools off and gives bad data. Is this a big problem? Would shorty's be a better choice? Does ceramic (or other) coating help keep the O2 warm enough to read correctly? If you have long tubes, do you experience this? I plan on a custom burnt chip from a dyno, would this help with this potential problem?

Thanks,
Rick

GTJake · Dec 9, 2003

I have zero problems with my LT.

Jake

VibrantRedGT · Dec 9, 2003

They will lean the car up a bit due to the O2 location down stream. Turn up the fuel pressure 2-3 psi and your done. I've had zero problems with mine as well. Jake and I have the same exhaust.

SmokinGT50 · Dec 9, 2003

Rick, I have had of the problems that you have listed, due entirely to long tube headers, I haven't figured out exactly what differences in the headers that I have and the ones that these guys have, but I don't want these guys to mislead you into believe that a fuel pressure regulator is going to solve your problems if they do crop up. If you are insistent on getting LT headers, get which ever brand and model they got because they seem to have escaped the possible pitfalls of LT headers.

GTJake · Dec 9, 2003

I have MAC LT.

Smokin,

Did you fix any of the problems with the twECCer?

Jake

SmokinGT50 · Dec 9, 2003

I have spent many hours with the TwEECer to get the car to where it runs great now, but if I turn the TwEECer off, it surges and dies.

Short answer, yes

Pushrod · Dec 9, 2003

I thought LT's made you run RICH not LEAN, and to compensate you should drop the fuel psi.

VibrantRedGT · Dec 9, 2003

Pushrod said:
I thought LT's made you run RICH not LEAN, and to compensate you should drop the fuel psi.

I wrote Lean instead of rich, my bad. Yes you are correct.

final5-0 · Dec 9, 2003

Rick

My answer to you is maybe yes AND maybe no!

I have seen my O2's cool down slightly during a very long idle period while data logging realtime with my Tweecer.

The amount of cool down has not caused drivability problems for me and no special adjustments in my cal file were made because of this issue.

I have seen others report of idle gremlins after they went to lt's.

Explain this if you can. One guy I know of says he can watch his O2's cool off to the point that his idle starts to surge.

He has ceramic coated lt's and I have just regular HTS coated Mac lt's but don't have the idle bugs.

It would seem that the better coating would hold the heat and it would not vary as much.

Later
Grady

RIO5.0 · Dec 9, 2003

I run Mac Chrome LTs and have had no issues regarding surge....I'm bigtime anal about stuff like that...mine been on 3 years..
I did add a Kirban by consensus real quick though, as i was running way rich after the install, prolly due to the O/2s being further back??...the Kirban, and leaning it out to start, then dialing it up with some EEC learn time will cure that...2 weeks or so i had the F/P back at 38....no probs since..
i have no o/2 related codes stored..the o/2 downstream thing is an issue...but given time, the EEC re-learns...
i almost bought some o/2 bungs and moved my sensors closer to the heat stream, buy hey, it runs good, no codes, so forget it, didn't seem worth it...

i had read the ceramic would help the cool o/2 issue, seems that may not be true as stated...

DaveB · Dec 9, 2003

Mine will surge when the car is very cold. It just did it before when I drove to class real quick. FWIW its 33* outside and its the first time I started it all day. It also only does it between 1,000 and 2,000 rpm for litterally the first 30 seconds you drive. I can live with that. It never did it when the weather was warm. My idle is a little high when the engine is very cold 900-1,100, but goes down to 750-800 after about 90 seconds if I just sit there and let it idle.

Overall I think LTs are way worth it, but they are a pain in the ass to install when you have a convertible . But I remember the first time I started it up, I was

1105 · Dec 9, 2003

I have LT's on my car, stock fuel pressure gauge and I had some surging problems... It would surge bad if I started up the car shortly after its been ran, but on a cold start up it was fine. I also had a problem with my timing, it had to be at a certain degree or else it would surge at idle.

Once I get a fuel pressure reg. all my surging problems should go away

Rootus · Dec 9, 2003

I did have some surging problems when it got real cold out (~40 degrees or lower). I datalogged and noticed that within two minutes of coming to a stop my fuel trim had gone up 15%. I just run a tune now that has me in open loop below about 1500 RPM, and it's no longer an issue. Gotta love the TwEECer .

Dave

GTJake · Dec 10, 2003

Seems like all the people with MAC had no surging the the BBK long tubes had all the surging (don't know what SmokinGT50 has). I drove my car when I got back home on Thanksgiving and it was twenty degrees outside, I started the car and it stayed rock solid at 900 rpm and then settled to 650-700 rpms when it warmed up. Zero surging though...even in cold weather.

Jake

1105 · Dec 10, 2003

why would the two different brands of headers have one cause surging and the other one not are the o2 sensors on the MAC's located at a different place maybe further up on the header than the BBK's? It doesnt make any since but I have the BBK's and idle problems, and I guess everyone with MAC's doesnt

JonnySmooth · Dec 10, 2003

Ive got Mac LT's on mine. At first it ran like trash cause i just cut the 02 harness and lengthened it with random wires. So then i bought the wiring harness extensions. Car runs great now, although it is a little weak when its really cold (Canada). No big deal, once i run it through the gears it runs good and strong.

If its a huge concern, just get some shorties and be done with it. If its a mild street car, it wont make too much of a power difference. But if you are gonna go all wild, then get the LT's.

Thats my 2 cents.

-Jon

Black Stampede · Dec 10, 2003

I have BBK ceramic coated LTs and have never, even in cold weather, noticed any kind of surging or irregular idle at all.

rockin_rick · Dec 10, 2003

Thanks for all the input, guys. I am planning a AFR165, FTI, performer build. I think that I will go with the MAC LT's and see what happens.

1105 said:
why would the two different brands of headers have one cause surging and the other one not are the o2 sensors on the MAC's located at a different place maybe further up on the header than the BBK's? It doesnt make any since but I have the BBK's and idle problems, and I guess everyone with MAC's doesnt

Perhaps this is a coinencidence, but if not, maybe the fact that the MAC's are equal length, and the BBK's are not has something to do with it. Or maybe the MAC's have a thicker tube that holds heat better.

GTJake said:
Seems like all the people with MAC had no surging the the BBK long tubes had all the surging (don't know what SmokinGT50 has).
Jake

SmokinGT50, what kind do you have?

Thanks again,
Rick

SmokinGT50 · Dec 10, 2003

I have the Bassani 1 5/8-1 3/4 stepped.

FastGT94 · Dec 12, 2003

Anyone have any dyno data showing if the MAC vs BBK length issue affects horsepower at all? Also how is the fitment of MAC's vs BBK's? Do BBK's hang lower?

Thanks!
-Dale

do longtubes on a street car = surging?

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