I lost lowend power with the S&S Headers...

[jibbby]

I recently installed the S&S shorty headers on my 1992 SC400 and was very very pleased with the top end power gains...I had also deleted the two cat down pipes...I had mentioned in previous posts the lowend is not compromised with the S&S Headers and all the gains were made at the mid to high end rpm ranges...I was mistaken.....

The reason I say this is that I drive a 1/8 mile hill climb or good upgrade of hill that is a steady and consistant upgrade...I drive it daily and pre-header install I would cruise up this same hill in third gear at 1500rpms or so and make it the whole way everytime with the A/C on too...After the header install just yesterday I drove up the same hill and the car almost made it at that same 1500rpm cruising speed in third but near the top downshifted for more power...I turned around and tried it again with the A/C off and the same result happened the car downshifted.... This tells me lowend torque and power is compromised slightly, I was a little disappointed........

The car is not tuned yet but is running just fine to perform this test.... I am not complaining as I kind of had traction problems anyway, so a little reduced lowend is not a big deal for me....The difference is barely noticeable but there is a difference for sure and this is despite what almost everyone thinks including myself for awhile there......

Just sharing info......

 

[Toysrme]

Unless stock headers are just blah, you always loose low end on shorty headers.
The shorter the primary runners & collector length, the higher in the rpm band the gain comes. Not really the fault of the header, that's just something that is always gunna happen regardless.

For refferance, most good long tube headers are like 3'+ primary runner lengths.




Just as long as the header gives you the overall gain you want, you're good.

 

[jibbby]

Toys, I didn't say it was the fault of the headers. I always knew you usually lose some lowend power with header installs just from years past working on the older small block Chevy V8's..The results were always the same......Topend would kick hard but lowend would suffer just a bit..Rpm's would climb more rapidly as the engine breathes better...However, with exhaust restriction/back pressure torque is increased at lower rpms, and the flow suffers at higher rpms....No different with the 1uz-fe v8's as I was told different on the forums in the past.....However, I still love the headers and am still very impressed with the over all power gains regardless.....

Not complaining just informing on what to expect with N/A header installs.......

I must say I am not thrilled about losing any lowend power even if it a little...I just love that lowend grunt what can I say:dunno:

So what happens on the longer header designs? Is the flow increased even more and more lowend power is lost like with the Tex headers as apposed to the S&S shorty's?

 

[Toysrme]

The velocity stays higher, and the timing on the reflecting wave is different as it comes back from the collector<s> into the cylinders.

Without getting into & just being "in general". A shorty header would be like a header for a race engine with a ginormous powerband. The reason they normally have huge gains on most engines *past* the peak of most "stockish" cams, is that they're just then getting into the rpm where they work really well.

What most people do when they're setting up long tube headers is shoot to try to maxamize the potential at peak torque, peak horsepower, or in between.



Like ya said, u already know the results. Long tube headers give a broader powerband, short tube headers are all about some top end.
AFA what outgains what, it's really dependant on how good the guy making them is. You go doing great work on a header & then have some noob put a crappy collector on it & which ever one you have may no longer work to potential!


It sounds like yours are good tho.

 

[jibbby]

Thanks Toy, I figured that is how the different lengthed headers work...Thanks for the clarification...

Well, In conclusion my sc4 was all lowend to midend range power pre-header install, now it is more Low, Mid and Highend power now, which is good because now the car pulls hard at all rpms, with just a hint of reduced lowend power......The headers obviously help with the engines overall performance, but without an upgraded torque converter on the SC4 you could be in for some really painfully slow launches...

 

[Toysrme]

Don't worry about it. That's every automatic.