HJK

Just to make sure we keep adding oil to the fire, here's my story. Received the DachX with cats from Chris last Friday in Bangkok, 7 days by mail. The thing looks great.

Did a dyno run before install, installed the xpipe and did another run. Simple as that.

Result; @3000 rpm 20Nm more torque, tapering of over 4500 rpm to an additional 11 Nm all the way to 5500. Horsepower up by 5. The HP lines nicely parallel all the way.

Few considerations, fuel is 95 ron, ambient temp around 31C / 88F.

The run was done directly after install so I don't know if the dme will adjust later on. Anyway, 274 RWHP with the tip ain't too bad.

Sound is just great, idle is perfect gruff, accelaration is a delight. I do have RSR's.

Thats about it for now,
Greetings from a warm Bangkok

Mark in Baltimore

Henk,

Thanks for the info! I'm glad to hear that you didn't lose performance. Can you do the board and the archives a favor and add "with cats" to the title? Chris makes DACH X's with and without, and it would be good to prevent any confusion.

Thanks for taking the time to do a dyno run and to post the results!

Harvey Yancey

Pretty impressive ...

RallyJon

Questions:
- Original chip, or a tuner chip?
- Did you disconnect the battery or otherwise allow the ECU to reset between runs? (the reason I ask is that the change in power everywhere looks like there was more advance on the second run)

HJK

Tuner chip, last month dyno 267, yesterday 269. No disconnects, before install 3 runs and the third one taken, then install of the dach and another 3 runs and the sixth one taken. Install time around 1 1/2 hr. Nothing disconnected in the meantime. Given the low quality fuel and ambient temps there's not much more advance to be gained on the chip. But anyway, nothin's been touched or disconnected.

TheOtherEric

Thanks for posting Henk!

Looks like approx. +5 hp across the entire rpm range. The number sounds reasonable, but it's surprising that the gains cover the entire range! Very nice. I expected little gains at low rpm, and most gains at high rpm, but it's exactly the opposite. You learn something every day.

TheOtherEric

Actually Jon raises a good point. If the sport cats were installed then immediately dyno'd (which it was) then if the ECU hasn't had time to adapt, it would run a little leaner, perhaps making more power. If that happened, the gains would get reduced once the ECU fully adapts. I'm not sure how likely this is; anyone?

993inNC

Thanks for the update Henk, that certainly great to see Would love to put to rest the question of ECU adjustment after having put some miles on them.......another dyno run maybe

Stealth 993

Oh yea! I can't wait to get mine on! I will be doing the same thing, hitting the Dyno after.

jscott82

In regards to disconnecting the battery to reset the ECU:
Maybe someone with more knowledge can set me straight, but I understood the 993 ECU uses two maps (actually many more) but essentially there is the wide open throttle(WOT) map that does not use feedback (it does not use the o2 sensor and does not "learn") this map(s) is hard coded from the factory for optimum performance, but since there are many variables (fuel, barometric pressure, etc) it can be fairly conservative. This is where tuners can get in there and push the limits further than the factory warranty would allow. Then there is the partial throttle map, it does use the o2 sensor and learns to provide best efficiency and fuel economy. On a dyno pull only the former is used, day to day driving the latter would be used.

Again someone set me straight if I am wrong. But I have a new set of Chris' cats on the way, and was planning on doing the same test.

One caveat to the whole thing: What kind of shape were the stock cats in for the first test, I know mine are shot, I would expect to pickup 5-10hp even if I went with new factory cats.

RallyJon

Forgot the knock sensor, which still comes in to play on WOT runs.

jscott82

yep... forgot about that step.....

lets try this version....
In regards to disconnecting the battery to reset the ECU:
Maybe someone with more knowledge can set me straight, but I understood the 993 ECU uses two maps (actually many more) but essentially there is:
Wide open throttle(WOT) that does not use feedback (it does not use the o2 sensor and does not "learn") this map(s) is hard coded from the factory for optimum performance, but since there are many variables (fuel, barometric pressure, etc) it can be fairly conservative. It will provide predetermined fuel/ ignition advance curves unless it senses knock, then it dynamically flattens the ignition curve. This is where tuners can get in there and push the limits further than the factory warranty would allow.
Then there is the partial throttle map, it does use the o2 sensor and learns to provide best efficiency and fuel economy. On a dyno pull only the former is used, day to day driving the latter would be used. Tuning here is useless/pointless.

Again someone set me straight if I am wrong. But I have a new set of Chris' cats on the way, and was planning on doing the same test. The other thing that needs to be monitored externally is air/fuel mix. If the new cats do indeed flow better (questionable) you will need more fuel to go with the additional air, otherwise you are running lean and not realizing the potential gain, even risking knock, which would reduce hp.

One caveat to the whole thing: What kind of shape were the stock cats in for the first test, I know mine are shot, I would expect to pickup 5-10hp even if I went with new factory cats.

Stealth 993

Resetting the ECU, just clears the "learned" maps. The maps are all 3d, based on load, temp, airflow, knock, etc..

The MAF monitors airflow, it can adjust fuel to match the airflow, so less exhaust resistance = more airflow= more fuel.

Usually at WOT, you go from closed loop (reading O2's & adjusting) to open loop, where the O2's are not used, & these maps are rich, & again, the MAF is still in the picture to adjust A/F.

This is not specific Porsche, but just what I know about mapping Bosh ECU's on BMW & Audi.

HJK

What I will do is another run on the dyno a few weeks down the road, have some trips (with the car) planned and trackdays. So in a few weeks i will give it another go and post the results. For now I'm very happy with the dach x and that is not related to the dyno graph, but simply to the sound and the way the engine revs up when hitting it. Will keep you all posted!
Henk

993inNC

Cool, do let us know Did you get any pics while the car was in the air?