I installed the mac longtubes and am running them with an O/R prochamber and mac axlebacks. After installing them I was using my bama/AM 91 race tune waiting for my LT specific tune. Got it about two weeks later. Installed the LT tune but didn't notice any performance gains. Both tunes seemed to pull longer but lacked a little low end torque, possibly due to the lack of cats. Any reason for this? Is a LT specific tune that much different than a standard race tune? Love the sound, but running LTs in CA with not much gain in HP is just not worth the risk.

 

Running longtubes without cats will net 20-25 rwhp with a 93 octane tune. About 10-12 of that is just from removing the cats. If you were already running an off road set up then you would only pick up maybe another 10-12 and that is going to be at WOT and peak rpm only. As far as the tune goes there is no longtube specfic tune out there that I know of. Brenspeed told me when they did my longtube tune is they turn off the rear O2 sensor only. No A/F adjustment needed.

 

I went from 91 oct tune with stock manifolds/cats and prochamber to LTs with O/R prochamber and doesn't seem like a 20-25 hp gain, unless most of it is 4k and up. Might put in some hi flow cats and hopefully get the low end back without loosing to much on the top.

 

Most of the gain will be 5,000/5,500 rpm and above. I am sure the extra power is there but it will take a dyno or a better ET at the track to show up. Just enjoy the great new sound they provide!!

 

Whos tune are you running? I was running bama 91 perf tune with stock cats/manifolds. When I loaded my brenspeed longtube specific 91 tune my car ran much better. Smoother idle, rpm's dropped a lot faster when shifting, and I also felt a little more umph up top and a torque increase. It fells a lot more "crisp" now

 

Adaaam is correct!!
I feel the same love. Been loving my Brenspeed custom tune for 2 1/2 years and just got my tuner back from them today with the updated tune for the 4:10's going in on Wed!!!.

Scoot

 

Running BAMA/AM tune with predator, didnt think Brenspeed does diablo.

 

That I am not at all sure of. Worth a call to find out.

 

see now I thought most of the gain would be in lower rpm's say under the 5000 mark and short tube would make more power in the upper rpm range.

 

Nope. Works the same as changing intake manifolds. Most of any gain with them is also on the top end. Personally the biggest reason I did longtubes was for the sound change over any power gain.

 

Scoot is correct!

 

Brenspeed doesn't tune for diablo. Just ask Bama/Am for an updated tune. Ask for the updated race tune. I had Chris Tilman, write that tune for me. Also Eric Brooks www.brooksspeed.com writes tunes for both SCT and diablo. I also use his tune.

 

When I had my prochamber, I had Pierre weld in a pair of magnaflow cats. When it was an o/r set-up, I felt it lacked low end tq. When I had the cats installed, I got the low end tq back and it gave it a deeper and smoother tone without taking away too much volume.

 

I've gone that route and the tunes keep coming back half assed, o2s not turned off, axle ratio wrong, revs wrong, labeled differant but performed the same, taking forever for updates. Tired of messing with them, think they are swamped right now and just pounding the tunes out instead of making the quality tunes they did before. Put in an old tune from original Bama and felt like it had a lot more low end power. Waiting for trick tuners to be up and running then I will do a bunch of runs and see what the different tunes make and maybe before and after with cats.


I feel the same way, O/R pulls longer but not as hard at first. I have some cats but they are to long to go before the midpipe so I might just bolt them in after to see the difference in power/sound. If I like it I will have some one weld them in.

 

I have good luck with the bama tunes. Why not just adjust gear ratio and tire revs using the diablo. Also, I think trick tuners only tunes for SCT. Before getting the dyno tune, try Eric Brooks. He runs the website over at www.modularfords.com. He is one of the best tuners out there.

 

I specifically asked for an updated tune after the 4.10 install because the race tune was to touchy. Came back and those things being wrong makes me question the whole tune. Joe is trying to get the diablo software, if not I will just check numbers and A/F.

 

The previous race tune was touchy, espcially with the 4.10s. I got an updated race tune from Chris Rose and the throttle is not as touchy but it pulls just as hard throught the entire RPM range. I don't have the A/F ratio for the updated race tune but for the previous one it was right around 12.8:1