Harvey Yancey

Somehow, with our on-going vacation lock-down at work, I was able to get today off and move forward with the installation of my DACH By-Pass Pipes and collecting empirical data regarding whether they effect performance (or not).

The plan was:

1) Base Dyno Runs (Dyno Jet)
2) Install DACH By-Pass Pipes
3) Final Dyno Runs

I did two baseline runs in the morning with the best results being 227HP and 217 ft/lbs torque. Now keep in mind that I have been having issues with my ECU since a top-end rebuild but since no other changes were being done to the car today the results should be applicable to other cars but the specific numbers could be different.

The installation was pretty smooth but read the instructions before the install, it will save you a few moments of panic. I used a lift but it would have went MUCH quicker with an extra pair of hands. It took me approx. 4 hours but that included going to Harbor Freight for some tools I did not have and some lunch. I could do it again in 1 1/2 hours. I did have to cut the metal straps around the cat with an air chisel. Those bolts did not want to move at all. Also I recommend spraying WD40 on all bolts the night before.

First impressions ... hmmmm ... not too loud ... actually at idle I can't really tell anything ... score! ... my wife won't get pissed off like she did with the Supercups. But once you get into the upper revs ... damn.

Ok ... now drive back to the dyno. This took a little longer because there was a supercharged Mustang there doing some runs ... the best was 590HP. Impressive but they break all the time.

We then did 4 runs ... the best being 247 HP and 220 ft/lbs torque. Air/Fuel was a bit leaner but nothing bad. I was surprised at the HP but had expected more torque.

I plan on having the ECU reflashed in the next few weeks because I think I am leaving power on the table ... but today's test shows that the pipes do help performance and they sound great as well.

red_wagen

Nice! Thanks for sharing
I guess it's safe to say it scores high on the WAF scale as well

TheOtherEric

Cool- thanks Harvey!

I guess my take-away is that you get about 20hp up near redline, but the torque stays pretty much unchanged across the rpm range. So it won't make your car any faster in street driving, but may give some little gain at the track.

p.s. this is exactly what I found when I tested stock vs. cup (open) airbox, except instead of 20hp up near redline it was more like 4-5 hp.

Caveman

Thanks for sharing! This is in line with the 20hp gains that I had heard through using split sports cats. I'm pleasantly surprised by your torque results as everyone always reports feeling like they may have lost a little low down though there is a slight dip I can see on your chart at 3k rpm.

Cheers,

David

993inNC

Keep in mind too that his ECU is still mixing the fuel for cats, not strait thru pipes. It will take time for the mix to richen and then his #'s should go up again. I'm hoping Harvey will have time and be gracious enough to take some more pulls in a month or so......see what the difference is.

Harvey, my thanks to you for the results and the write up

Bill Verburg

My '95, w/ fabspeed pipes 240hp@6018, 234ft-lbs @5332

small valve, nonvram

FlyYellow

harvey,

thanks for the post. really nice of you to share your results.

cheers,
boris

993inNC

So maybe my design isn't half bad after all eh Bill? 7 more horse with the X vs. individual pipes. I'm pleased, but I have an idea to try and get the torque up a bit.

Bill Verburg

I wasn't going to point this out but since you brought it up

7 more hp, 17 less ft-lbs of torque from as motor that should be putting out 13hp more and 7 ft-lb more

Harvey Yancey

One other observation after having the chance to drive the car about 200 miles or so today round trip to the EURO Auto Festival at the BMW Factory in Greer SC (blatant plug) ... the car is noticably smoother especially when coming off the throttle. Really, really nice.

Harvey Yancey

Hey Bill,

As I said I did not have any expectations of numbers from this test only to make sure that nothing was lost. I had a top-end rebuild done a while back and I have been chasing getting the HP back via the ECU for quite a while.

Pre-rebuild my HP was approx 242 and torque was something like 235. After the rebuild I was at 238HP and 207 ft/lbs and my A/F was really bad.

Autothority did one flash that corrected the A/F but the power dropped to 235 HP and 204 ft/lbs. Another flash resulted in correcting a stalling issue but resulting in the power that you saw in the current dyno numbers with the cat.

I spoke tp Peter Dawe a few weeks ago regarding what we should do (he did the head work and supplied the cams) and he suggested some 100 cell cats as he thought that 70K+ miles my cats were shot and we needed to open things up. I surmised that a cat-bypass would be better.

Currently I am working with Protomotive to get a new flash done (I may have to drive to Arkansas ... but that's another story) and I am hopeful that will get me to the power that I had expected.

Anyway ... the moral of the DACH story is that the power went up and not down on my car and at this stage of the game that's all I was looking for.

993inNC

Moral of the story (irrelavant of the condition of Harvey's motor) is that there was an increase right out of the box of 20hp/2ft.lbs torque. With a few minor changes I think we can get the torque up a bit, but considering we took and idea (as hobbiests not engineers) and made 20 hp with a relatively inexpensive bolt on (compared to internal costs to gain 20 hp), I'd say we did pretty damn good I'm quite pleased And I hope to see him get quite a bit more HP with the proper flash of the ECU.

Bill Verburg

Imagine what that non stock motor would do w/ a properly designed exhaust

Harvey Yancey

Hey Bill,

Feel free to post your suggestions regarding exhaust systems. I am always interested in what other people have done with their cars..

Bill Verburg

What i did? Who cares, I'm nobody.

If you want to merge the banks this is the way to do it


However you would do well to emulate what these guys do, A lot of time, money and thought went into these, they are not perfect, but the broad strokes are there for those with the eyes to see.