do longtubes on a street car = surging?

final5-0 · Dec 12, 2003

FastGT94 said:
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

Dale

I don't think the brand of header or coating makes that much difference with driveability issues.

The O2's being farther away from the stock location a big contributing factor to these problems but IMHO, not the only thing that is at work here.

Most likely, lt's get the blaim when it is something else causing the trouble a lot of the times.

Without going into a lot of details, there are many things that can be changed in the pcm that helps with driveability gremlins.

I think that the difference in peoples combos, pcms, and how their cal files have been configured have a good bit to do with why some with lt's have issues and some don't.

Later
Grady

Rootus · Dec 12, 2003

final5-0 said:
Most likely, lt's get the blaim when it is something else causing the trouble a lot of the times.

I think it's safe to say that LT's definitely cause a rich condition at idle, but that not everyone experiences surging as a result. It depends on how severe the rich condition is, and a few other factors.

Personally, I didn't see much surging at idle until the KAMRF got above 1.15 (15% rich), and really I never did see it at warm idle. But what would happen is that the computer would get the 1.15 stuck in its head, and when I started it back up cold, the combination of the normal richening for cold startup, combined with the 15% fuel trim adjustment, caused it to surge.

Dave

final5-0 · Dec 12, 2003

HairyCanary said:
I think it's safe to say that LT's definitely cause a rich condition at idle, but that not everyone experiences surging as a result. It depends on how severe the rich condition is, and a few other factors.

Personally, I didn't see much surging at idle until the KAMRF got above 1.15 (15% rich), and really I never did see it at warm idle. But what would happen is that the computer would get the 1.15 stuck in its head, and when I started it back up cold, the combination of the normal richening for cold startup, combined with the 15% fuel trim adjustment, caused it to surge.

Dave

Hi Dave

I've had a little of what you are talking about but just not as severe of a case as you and others I have seen with their lt's.

Later
Grady

FastGT94 · Dec 15, 2003

final5-0 said:
Dale
I don't think the brand of header or coating makes that much difference with driveability issues.
The O2's being farther away from the stock location a big contributing factor to these problems but IMHO, not the only thing that is at work here.
Most likely, lt's get the blaim when it is something else causing the trouble a lot of the times.
Without going into a lot of details, there are many things that can be changed in the pcm that helps with driveability gremlins.
I think that the difference in peoples combos, pcms, and how their cal files have been configured have a good bit to do with why some with lt's have issues and some don't.

Later
Grady

Was wondering more about Overall HP not drivability. Do the truely equal tube lengths of MAC headers give more power? How much difference is there in tube length of the BBK's? I'm just seeing if there is enough power difference to justify the loss of the single flange BBK's if I got MAC's. And I'm still wondering about the ground clearance issues with either brand. (They seem to be comparable but I'm unsure at this point)

Thanks!
-Dale

Rootus · Dec 15, 2003

I gained 3.5 mph when I put on my BBK longtubes, so even if they are not truly equal length they do seem to have good flow . For ground clearance, I have no issues -- the lowest part of my exhaust system is the cats, and I never hit those either. My car is lowered about 1.5 inches from stock.

Dave

FastGT94 said:
Was wondering more about Overall HP not drivability. Do the truely equal tube lengths of MAC headers give more power? How much difference is there in tube length of the BBK's? I'm just seeing if there is enough power difference to justify the loss of the single flange BBK's if I got MAC's. And I'm still wondering about the ground clearance issues with either brand. (They seem to be comparable but I'm unsure at this point)

Thanks!
-Dale

GTJake · Dec 15, 2003

I don't think there is going to be a big difference between BBK and MAC. Just pick whatever you like better or whatever is cheaper...

Jake

zenboy99 · Dec 15, 2003

HairyCanary, you have cats with long tubes? What kind of H-pipe do you have? How much HP do you think you're loosing with the cats on?

final5-0 · Dec 15, 2003

FastGT94 said:
Was wondering more about Overall HP not drivability. Do the truely equal tube lengths of MAC headers give more power? How much difference is there in tube length of the BBK's? I'm just seeing if there is enough power difference to justify the loss of the single flange BBK's if I got MAC's. And I'm still wondering about the ground clearance issues with either brand. (They seem to be comparable but I'm unsure at this point)

Thanks!
-Dale

Dale

I could not say anything about the H P gain cause I put them on with several other parts at the same time.

I don't know the difference about equal length or tube length between the two brands of lt's.

My Mac's fit tight to the floorboards so I don't have any ground clearance issues.

Later
Grady

Rootus · Dec 15, 2003

zenboy99 said:
HairyCanary, you have cats with long tubes? What kind of H-pipe do you have? How much HP do you think you're loosing with the cats on?

I have a Magnaflow catted H-pipe (~$235) that was originally for shorty headers, and I had it cut down to fit the longtubes when I installed them.

I consistently lose about 2 mph of trap speed when I'm running the cats, so I figure I give up 15-20 hp with them on. It's quite noticable in the higher RPM's, it definitely pulls much harder from 5500-6250 when I'm running the offroad pipe. Heck, sometimes I break 'em loose on a 2nd gear pull as it passes 5000 RPM . Only with the offroad pipe, though.

Dave

zenboy99 · Dec 16, 2003

Thanks for the info, just trying to guess how much HP I'm loosing with my catted H-pipe. How the heck did you cut that thing down? That must have been a pretty intense project.

FastGT94 · Dec 16, 2003

Do the BBk's fit tight to the floorboards like MAC's?

rockin_rick · Dec 17, 2003

FastGT94 said:
Do the BBk's fit tight to the floorboards like MAC's?

I got the impression that BBK's were a bit lower than the MAC's. BUT, I have never actually seen either installed. Can anyone shed some light on this?

Rick

FastGT94 · Dec 18, 2003

Rootus · Dec 18, 2003

zenboy99 said:
Thanks for the info, just trying to guess how much HP I'm loosing with my catted H-pipe. How the heck did you cut that thing down? That must have been a pretty intense project.

Not too bad.... $40 to the local muffler shop .

Dave

Rootus · Dec 18, 2003

rockin_rick said:
I got the impression that BBKs were a bit lower than the MAC's. BUT, I have never actually seen either installed. Can anyone shed some light on this?

Rick

I can tell you that my BBK's don't come closer than an inch to anything on the car, with the exception of the A/C line on the passenger side strut tower -- one of the primaries touches a bracked that holds the line to the strut tower. Haven't had any problems as a result. No clearance problems at all with the K-member or floorpan, and it's not the lowest part of my exhaust, and I've never hit the collectors on anything.

Dave

Slow5.0 · Dec 18, 2003

I have no problems with my LTs

do longtubes on a street car = surging?

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