LT Headers Low-Mid Range Power Loss

[spoole96]

What size are your primaries?

Long tube headers with large primaries could reduce the bottom end in a standard motor. For example, if your primaries are too big and straight, you will reduce the scavenging effect at low RPM and cause rough idle and a loss in bottom end. These headers would be more suited to a blown or worked engine.

In standard or mildly tuned motors it is better to have slightly smaller primaries, with some strategically placed mandrel bends to speed up the exhaust flow at low RPM where there is little gas flow from the motor, thus improving scavenging and allowing the motor to build power faster. There is some lower level physics which I will not go into, but that is the general idea.

I went with the Kooks 1-7/8" and high flow cats. I'm hoping the primaries are not too big like what your saying. I have been keeping up with the results and opinions of others on this site that have pretty much the same mods and they had been reporting good results.

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[bobc775]

I went with SW and also have 1-7/8" with high flow cats.

 

[spoole96]

How are you supposed to verify hp/torque loss without putting it on a dyno?

So your telling me that if you make changes to a car and the only way that you can tell if it's performing correctly is on a dyno? That's complete bullshit. I know a dyno is the best practice to get a tune dialed in. But when I live hours away from a reputable tuner, I can't just hop in the car and go. But what I can do is tell that my damn car is not perform like it should or has before this header/updated tune install. Up high yes. Down low to mid - hell no!

 

[bobc775]

I'm uncertain regarding how a dyno works. It seems that in the videos I've watched it's WOT from beginning to end. So I can see how it would give you a WOT power band. But how does that help normal daily driving where your only trying to give it a low throttle. When a tuner tunes using a dyno at WOT does it some how make partial throttles correct. After installing my headers I'm just trying to get the simple daily parts to work. I could care less about total HP at this point.

 

[Tommy V]

I am running my car with long tubes and no tune for themDiablo stalled BBK 1- 3/4 long tubes and put the rear 02's in the place wear my wide band would go with defoulers, then welded new bungs on the front cylinder tube on oneside and the rear cylinder #8 on the other for the wideband, and beat the tar out of it saturday night. even ran a buddy who is making 440rwhp with his 15 and either would stay door to door with him or he would pull me by a car in 4th. but he said that my car is probably running fat up top because its trying to cool the cats that are not their. with a tune i would probably stay with him in 4th. just a canned diablo tune in the car and thats it. no aftermarket CAI on the car.

Yes i know u can turn the cat overtemp protection off with the sct,not sure about the diablo.That would take care of running rich to cool off the cats,well the ones not their lol.But back on topic,my opinion is u may lose some torque or at least change the curve with the longtubes,especially with the 1-7/8 primarys when on basically on a stock car.

 

[350sexZ]

How do you know that I'm not using Lund already?

Got a tune revision after my kooks install and was able to feel a difference, turned beast mode. I'm running the 17/8 catted also.

 

[BlownStang15]

I went with the Kooks 1-7/8" and high flow cats. I'm hoping the primaries are not too big like what your saying. I have been keeping up with the results and opinions of others on this site that have pretty much the same mods and they had been reporting good results.

Rather than getting too caught up on worrying about if they are too big, you could try to fill them more. i.e. Larger throttle body and intake, then dyno tune.

The reason I say this is that you would assume Kooks did a fair amount of testing, but they would have assumed that most people changing headers (especially with large primaries) would do other mods. More air in (and fuel) with the right valve timing, should increase the exhaust flow at the bottom end, allowing the exhaust to work more efficiently, and yielding a better result right through the rev range.

Or whack on a blower.

 

[anotherneon]

But wait. I must be wrong about my car not running right. I haven't had it dyno'd so there for I can't tell if it's running smooth. :doh:

My car is definitely not running at optimal performance down low and in the mid. It's also VERY hesitant when I drive it the first time after its been sitting over night. Even if I let the car warm up to normal temps. It definitely didn't do this before the headers and new tune.

When it does this after sitting over night what are the ambient temps? I noticed that in the morning when its fairly cold out, mid 30s, my car feels the same way. However, on days where its warmer I have no issue. I think its something with the PCM. Even when I was stock there were days that the car "felt" faster or slower than others depending on the weather. Now before someone says "no shit" let me state that I have had this car since Oct and temps from Oct to now, EXCLUDING the harsh winter single digits, the temps have been roughly the same. Perhaps the PCM is seeing something it doesnt like and is pulling timing? Have you made any logs to send in?

 

[Livernois Motorsports]

Well that sucks for me lol. I thought you guys are out of Houston.

No, but we probably do more custom remote tuning in Texas than anywhere else. There are a bunch of guys that have LTH, CAI's and exhausts IN TEXAS that run our remote custom tuning on the board! Look up I believe his SN is 350sexZ, he runs our CAI, tune, 160° tstat AND LTH! Car runs like a champ...I think he even started a thread about his car and mods. He runs out remote custom tuning on his S550 and his XSport!

 

[Livernois Motorsports]

How do you know that I'm not using Lund already?

I guess that means run our tuning then

 

[Livernois Motorsports]

I'm uncertain regarding how a dyno works. It seems that in the videos I've watched it's WOT from beginning to end. So I can see how it would give you a WOT power band. But how does that help normal daily driving where your only trying to give it a low throttle. When a tuner tunes using a dyno at WOT does it some how make partial throttles correct. After installing my headers I'm just trying to get the simple daily parts to work. I could care less about total HP at this point.

I will answer to the best of my ability, as I cannot speak for how other establishments handle tuning.

For us, dyno tuning starts long before you see that WOT run. We test at low (2-3000ish), then again at around 3700-4000, 5000 and then WOT. After we test and tune all of those we then have our calibrator go out onto the streets and test and tune live under real driving conditions until he is happy with how the tuning responds. AFTER ALL OF THAT, our shop supervisor will then go out on a longer and more diverse test drive to test all around performance, reliability and driveability. If everything is aces, we release a car. If not, we take it back to square one.

That is why we are able to supply you guys with such accurate and reliable custom remote tuning as well. We spend countless hours validating what we test on ourselves before we release any product.

“Champions keep practicing until they get it right.”
-Billie Jean King

 

[B-52 Jetman]

LT Headers always move the power up higher in the power band. They're designed more for drag racing, where the motor is going to need to breathe more. You won't get that mid range back...doesn't matter what you do.

 

[09jsw]

LT Headers always move the power up higher in the power band. They're designed more for drag racing, where the motor is going to need to breathe more. You won't get that mid range back...doesn't matter what you do.

Very true but that does depend on header design and tune.

 

[B-52 Jetman]

Very true but that does depend on header design and tune.

They're might be slight difference depending on primary size. But, the whole point of LT Headers is to increase flow. Once you do that, the HP curve will always nice higher in the RPM band...it's just what they're intended to do. Some folks don't know this & wonder why they're around driving characteristics just went to crap...because we don't drive around in the upper 3/4's if the RPM band on a daily basis...well maybe some here do.

 

[bobc775]

I will answer to the best of my ability, as I cannot speak for how other establishments handle tuning.

For us, dyno tuning starts long before you see that WOT run. We test at low (2-3000ish), then again at around 3700-4000, 5000 and then WOT. After we test and tune all of those we then have our calibrator go out onto the streets and test and tune live under real driving conditions until he is happy with how the tuning responds. AFTER ALL OF THAT, our shop supervisor will then go out on a longer and more diverse test drive to test all around performance, reliability and driveability. If everything is aces, we release a car. If not, we take it back to square one.

That is why we are able to supply you guys with such accurate and reliable custom remote tuning as well. We spend countless hours validating what we test on ourselves before we release any product.

“Champions keep practicing until they get it right.”
-Billie Jean King

Thanks for your comments. So I think what you're telling me is by getting a dyno and finding out that I made a total of 440HP isn't going to tell me that the mapping/tune is good for my car during normal daily driving. Thanks Again

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