chrisc

Alright, so in order to clear up some of the speculations on true duals, I decided to do this little test.

For the last few night, I went out and did two different things. I testes g forces on a dead stop and run, and g forces on a 35 roll. (Using my super cool D-PIC). I tried to make the conditions exactly the same. I basically took the car for a little spin on the same road to warm up, then I went back to the same place and did the same tests. As you can see, the numbers were pretty firggen similar. The only issue was Night 2, which was a little tiny bit moist, and I was getting a tad less traction. For me, the Pre-Duals numbers were pretty regular, I can get 0.01-0.03 higher if I really get a good launch on the Digs, and the rolls are always basically the same situation.

Also, the Post-Duals tests were both done tonight.


Pre Duals:
Night 1:
From a Dig G-Force Max: 0.56
35 roll G-Force Max: 0.34

Night 2:
Dig: 0.54
35 roll: 0.32

Night 3:
Dig: 0.55
35 roll: 0.33

Post Duals:
Test 1:
Dig: 0.58
35 roll: 0.46

Test 2:
Dig: 0.59
35 roll: 0.48


These last two things are things that I just noticed during the tests and decided to keep track of, but did not include them on the initial tests runs, so I do not have hard data for Pre-Duals:

When I saw that the roll seemed to be pretty powerful, I decided to try my 45 roll, which to me is my weakest point. Normally, I will hit around 0.24-0.28. This time I got 0.35 (only tested it once, it was not on my list).

I also noted that during shifts on my dig sprints, I usually dropped down to about 0.18 during shifts, however, on all these tests, I dropped down to 0.24 & 0.23. Once again, I do not have exact Pre-Duals numbers for this, but that is 0.18 is generally what I get.


Lastly, I felt that when I pulled off the gas from a slightly high rev, it seemed like the car did not quickly rev back down. It felt way more natural...I dont really know how to explain it. Previously, I always felt that my car did not feel very normal, and just blamed it on the supercharger. It still does not feel normal, but it feels more normal now lol. Later, I saw my uncle who is pretty into cars, and told him about this. He said that it was because now I dont have as much back pressure on the engine. Because it is not building pressure, things will feel more natural.

To me, that is pretty friggen amazing. I really did not expect to see any differences in the car, but I am very gladly surprised. If I didnt have this D-PIC, I would have said that it is all in my head. Now, I know some people will bust out technical stuff that will go over my head, telling me that this is impossible and say that I just had a really good night or something...but trust me, there is a difference. If you have not changed your exhaust to something more free flowing, and you are running F/I, you should really consider it.

SOHCman

That is the second thing I noticed when I put my duals on... I can actually COAST now! (The first thing was my "hesitation after long cruise" was gone.)

Still, 7-8 seconds after you take your foot off the gas, the car does still decellerate automatically... but only ONCE!

Used to do that EVERY 7-8 seconds after you take your foot off the gas.

My average mileage went up by about 2 MPG because of this.

On one hill near my place, keeping the throttle steady, I actually gained 20 MPH on the downgrade and was able to take my foot off the gas and maintain that speed for the entire 2 mile grade!

You can get great mileage coasting at high speeds.

F/I or not.

SOHC

p51mstg

SOHC, do you think your experience was a result of a tune, or the dual exhaust? Or both?

nonstopred

well, i got my true duals, but i honestly dont see a difference (w/e they sound sick), I think they only helped you with power is because with your supercharger, your blowing more steam out the back that was restricted with 1 pipe, but without FI I think that its not detrimental/beneficial to the engine's performance

Sancho805

nice test. now i wonder what the results would be on a N/A stang. much has been said about loss in torq and gain in horsepower with true duals for a N/A engine but i haven't seen any numbers from users yet, including myself, to make any definate statements.

chrisc

There are two people who have actually dynoed the pre and post duals on an n/a car, and they both lost like 5rwtq

Sancho805

oh ok. well there it is. do you know their horspower numbers?

chrisc

one i remember because he had sweet numbers for a n/a car. the other guy i forgot. he had 210/235 (I could be 1 or 2 off, but it was something like that). he sold his car or something though

chrisc

**repost

p51mstg

I remember a post by Justin from VMP, where he said they tested both single and dual exhaust (on a n/a 4.0 engine) on the dyno and found no advantage to duals.

I recall that he did find an improvment by changing to a more free-flowing axle-back (such as a GT takeoff), and they actually sell a "25HP" kit, which includes a CAI, GT axle-back and a tune.

Not sure where I saw that post, or how long ago, but foundit interesting. He didn't say whether there was a loss of torque, etc. from duals - only that there was no benefit. That's what sticks in my mind, and it could be different than other's dyno experience.