Ketchmi

The mixture was great which further confuses me. The car exibits all the traits of a properly running car with everything operating as it should, just missing some hp. I haven't had the time to dig too deep as I just finished dyno'ing it yesterday. It did not respond well to the piggyback computer either which could lead me to believe the LH but with the SMT6 removed, it operates perfectly.

The exhaust components are new which rules them out. It did dyno at 293 rear without cats and our "second best" X-over. It is stock from the cats back and annoyingly quiet.

bigs

David - you and your "annoyingly quiet!"

That's cuz it's a refined grand touring car. Not a hotrod. Well, not completely a hotrod!

"...with the SMT6 removed it operates perfectly." Well, except for them lost ponies!

What do you think about the hall sensor/knock sensor ideas?

SharkSkin

I'm not convinced there's a problem there... what am I missing?

345 HP - 15% drivetrain loss = 293 HP.

293 HP - 10% loss due to altitude = 263 HP.

A conservative estimate for HP loss at altitude is 3% per 1000 feet. That would work out to a 13.5% loss. Sounds to me like your car is doing great considering the altitude...

Bill Ball

Ah, so the Hall sensor connection is different on the GTS, as Dave C dscribes in detail. It's part of the same plug as the rear knock sensor on my S4. Since you guys just replaced the injectors it is possible the rear knock sensor plug was not completely seated, as I discovered. That will retard the spark.

mark kibort

Guys, im surprised you having addressed the altitude thing more seriously. 4500ft is a HUGE power killer. its not a fixed rate per 1000ft, but thats a good rule of thumb. 6000feet is over 20%.
Now, were those dyno numbers with SAE adjusted values. I ALWAYS like to get both. you learn a lot about what is going on by looking at both each time. the conversions are not alwasys right. recently, i did a dyno actual value of 322hp on a 82 degree day and higher than 29.90 pressure. yet, i had a .99 correction factor bringing it down to 320.

Dave have you done other dynos at altitude? if so, how did they stack up with this one?

Ketchmi

Both knock sensors and the hall sensor are connected, the hall sensor is new, the knock sensors appeared to be in ok condition when I had the intake off.

All the hp numbers are corrected for altitude. Our 86.5' did 273rwhp with our catless X-over and no fuel tuning. I would think that the GTS should have a bit more ummmph than the 86.5'. It did do 293rwhp without cats but I think it's still a bit shy. The GTS is rated at 57hp more than the 86.5', even considering that the GTS is an auto, I think we are still missing some power. The GTS is dyno'ing at the same level as almost every S4 I have dyno'd at this altitude.

There is one abnormality in the dyno runs with mid range power flucuating between runs but only between 4500 and 5200 rpm. Everything before and after is the same with the same hp & torque peaks. It seems to happen just after the flappy opens, sometimes it's 15 hp more than others with less than 3 hp variation during the rest of the runs. I will try to post a dyno sheet showing this later.

Thanks for the ideas all, maybe we will get Bigs the power he deserves.

bigs

Hmmm... Maybe the altitude is indeed more of a killer than I realized. Maybe the best test would be a road trip down to CA!

But yeah, I'd like to see the dyno sheets posted and let you guys check 'em out.

Could a flappy have a problem that only shows up intermittently?

cfc928gt

Altitude is indeed a power killer. Several years ago we did a dyno run in Evergreen, CO which is right around 7500 ft. My '89 GT, which dynoed at Wichita at 283 rwhp only put down 190 rwhp at 6000 rpm. The S4s were putting down 155 rwhp and a '85 euro auto did 158 rwhp. Temp was 64 degrees, baro 30.16 and humidity was 60%. It wasn't a dynojet either. We also did a run up to the top of Mt Evans, which is the highest paved road in the world at 14,264 feet. The sharks were gasping for air and hardly responded to throttle input, absolutely anemic. We parked them at the summit for a group picture and we could barely get them started again. Sharks out of their element for sure...

Bill Ball

Dave:

Have you run a Hammer/Spanner on it? I thought my knock and Hall sensors were connected, but the Spanner told me otherwise. I mean, you're probably right, it's something else, but the Spanner may help spot it.

Ketchmi

We have a Hammer, I'll try it the next time Bigs is in the area. From looking at the dyno graph, I suppose the knock sensors could be failing as it really flattens out about 5k rpm. I'm just stumped about the differences between the runs at midrange.

SharkSkin

Sure, there are electrical and vacuum lines that control it; there could be issues with either or both.

mark kibort

so thats the SAE adjusted run, how does the actual look? (what was the correction)

usually, our cars have the same torque as HP (in footlbs) I wonder why the curve falls off so fast.

definitely could be knocksensors doing their thing.

mk

bigs

Thanks to all for the ideas and input.

I just love a good mystery. Well, as long as it gets solved!

Is that rather abrupt drop-off in HP and torque at about 3800 rpm commonly seen? And isn't that about the rpm that the flappy starts flappin'?

worf928

Looks to me like the flappy only operated correctly on one of the three dyno runs (assuming nothing else was futzing with the lump.) Dyno run two is the only one that looks healthy. Yet, the rwhp and torque numbers are low by a bit still. I'm still betting on something retarding the timing.

Tom. M

from the looks of the A/F..it appears you start to go rich at the suspect rpm range...between 4500 and 5500... Wonder if the a/f is reading excess oil as fuel (HC) and it's trying to lean out-- causing knocking..which in turn of course then retards timing..and drops power...and after it's all cleared out..(oil that is)..then power comes back up?


More random thoughts..

Later,
Tom
midlman@rennlist.net

89GT