odd behavior

[lucas]

i recently move to huntington beach after living in lake arrowhead, and there is about a 5000ft difference in altitude. I first started noticing my car wasnt reaching full boost about a week after moving down there. I thought it might be the cold weather or maybe a knock sensor. But the other day i can up the mountain and bout 3/4 the way up i started reaching full boost again??? odd is there some kind of altitude sensor in our cars? and it is considerably colder up here was 21 this morning? anyone have an idea?

[wfoote]

By low boost, I assume you mean 8-9psi and at 5,000 ft you are probably seeing 10-11psi. This is normal behavior. I live at 5.000 and see 11-12psi.

In the aviation world for turbocharged aircraft we use manifold pressure gauges instead of our boost/vacuum gauges. A MP gauge displays inches of mercury. This is much easier to read whether you are making boost or not. with the engine off, the instrument reads atmospheric pressure. We don't really try to overboost for performance, just boost to standard atmospheric conditions. This is called turbo normalizing.

In order to maintain sea level atmospheric pressure we will need to start increasing boost as soon as we start climbing. In your case at 5,000 you will loose ~1" of mercury / 1,000 feet. So to maintain sea level pressure you would need to increase the boost by 5" of mercury to maintain the 29.92 inches of mercury or ~2.5PSI. So if the stock boost is 8.7PSI at sea level and you add the 2.5PSI for the elevation difference you would see ~ 11.2PSI at 5,000 feet.

[lucas]

lol i like the aviation comparison and the laps rate equation, im a pilot as well and just finished ATP flying twin seminols. The weird thing about my car is this isnt a consistent symptom its done this in the past before i moved to huntington beach, just short jonts down the mountain. seems to be ok now and im seeing 11-12 psi down here, but im sure it will happen again. Im thinking the only way to solve this is MBC.

[wfoote]

Congrats on the ATP, that is quite an achievement for a pilot.

I was having erratic boost problems as well. I tried changing knock sensors and still had the problems then as a final act of desperation I relocated the knock sensor just above it's original location a little farther back on the engine. Haven't had a problem since.

[lucas]

relocate the knock sensor..... i dont really understand how you would do that. did you add spacers or im assuming there is enough play in the bracket to move it around some. Wouldnt a more simple solution be a MBC, i have done the TD04 and 06 TMIC mod so i am seeing 11-13 psi of boost. but sometimes it will only get a little over 5.

ATP if i had to do it again i wouldnt, for the money it would be way better to do it though a private FBO, ATP has a lot of flaws that if there is ever a problem or you dont complete a part of the course you wont get your money back. Especially the way the economy is they have screwed alot of people including me.[/b]

[evolutionmovement]

The knock sensor bolts to the block itself. How would you relocate it so that it would still be able to do its job?

[wfoote]

I had a bit of piston slap that it seemed to to be reading as a knock. I moved the sensor to a flat spot on the rear of the block just ahead of the bell housing. The sensor is bolted solidly to the block with no spacers. I have tried two sensors in the original location with the same result. The symptom I was fighting was the engine constantly pulling timing and limiting boost to 5PSI. If anyone is interested I can probably take a picture of the new location.

I realize this probably isn't an optimum location for the sensor, but I am willing to take the risk until I can address the piston slap. I don't really race the car. I live in the mountains and the dirt road I drive on to get home frequently would be the envy of a lot of the rally drivers. I just like having a capable car that is fun to drive.

I assumed from your message you just got your ATP. I did all my training part 61. I especially agree with the comment about part 141 schools, I know some people who lost a lot of money when silver state helicopter closed their doors. It was nice to finish up all my training through CFI and CFII with no debt.

[lucas]

yes ATP did screw alot of people and continue to do so, I opted not to do there CFI program on the grounds that only ATP would higher you, because the CFI training was such a joke. Given the economy i havent completed my CFI because well i just cant afford it, flying is still a rich mans sport and im just a poor kid that HAD a sugar mama to foot the bills. so unless i win the lotto or she comes back the flying biz is going to be a long hard road for me.

[evolutionmovement]

That sounds like the stock location for the sensor. Just asking in case it was limping because there was a knock issue previously.

[wfoote]

My understanding was the stock location was on the block under the left rear runner of the intake manifold. Here is a picture thanks Josh! http://www.main.experiencetherave.com:8 ... P_2481.JPG
My sensor is now on the block just behind the knock sensor connector in the picture. Since moving it there I haven't had any more issues.

I finished my CFI, CFII and AGI with American Flyers in Pompano. They have provisions for part 61 and an advertised price of ~$3k now. It was a good experience and they were a good group of people.

[Gerry]

Thank you for the pictures but could you find it in your heart to reduce the size of them because your server is very slow and it takes a painfully long time to load.

[Legacy777]

The pictures are mine.

I had issues with my connection the other day. Please try again. They are loading fast for me right now.

Thanks