Wayne 993TT in France

Hi All,

being relatively new to the TT world, I have a question:
My 993TT, when accelerating hard in 2nd gear (for example), the pressure in the turbo's seems to be different everytime. ie on the way to work this morning it on got up to 0.6, but another times it gets to 0.8. My question is does the engine managment decide what the max boost is at a certain time, depending on conditions (ie how hot the engine is, air temp, pressure etc). or do you think its something more serious, that I should get the car looked at? Not owning a turbo before I don't really know what to expect from the boost, and how consistant it should be. Also should it be on full boost as soon as you floor it no matter what gear you're in?

Thanks,
Wayne

Ran

I get to 0.8 fairly easily when accelerating hard. BUT, if I hesitate while flooring due to traffic, etc., then it does not go all the way even if, after that initial hesitation, I continue to floor the pedal. Also, I have found (though this may be anecdotal as I have not looked at it empirically) that I may be able to achieve 0.8 bar boost more quickly after driving some time or maybe it is when driving during a certain time of the day.

BTW, are you referring to achieving only 0.6 just once or did you try it several times on this particular run and always got to only 0.6?? If I try to reach full boost a few times, I ALWAYS reach 0.8 atleast a couple of times so I CANNOT say that at times the max boost is only 0.6 So, if on a particular run, I found that I could NEVER achieve 0.8, it would be uncharacteristic of my car but I cant say that I have it for that long to know everything.

As regards how soon you reach full boost, I would say barely a second or so and at those speeds hardly easy to watch the boost gauge but I have seen it go up so I have had time enough to watch it climb from 0.0 through to 0.8. I have not measured the time though but it is pretty instantaneous.

In any event, I am merely relaying my limited experience with the 993 turbo. Others here know more and will chime in later in the day with better info.

Which part of France are you in btw?

Wayne 993TT in France

Hi there,

mine definitly takes longer than a second it only gets to 0.8 at around 5500/6000 at the quickest. At what revs does your boost get to 0.8?

I'm living in Antibes inbetween Nice and Cannes on the French Riveria

thanks,
Wayne

Ran

Sorry did not check revs.

BTW, subsequent to my above post, I tried flooring in 3rd, 4th and 5th gears on my morning drive and was able to get 0.8 bar very easily on all. It was about 7:30 am here and we had low humidity at 54 dewpoint and 62-72 F (~17 - 22 C). Traffic conditions did not allow for 2nd gear check though. 5th gear seemed especially easy since I was on a fast highway and it was at 0.8 in one second or less I think (not sure). 4th was the same. Tried several times and got to 0.8 every single time today.

Antibes!! You dont need to be at that kind of boost there. Enjoy the scenery on the Corniche. I need to get back there. Fun element wise, the drive west of Nice via St. Trop. on through towards Marseilles (not all the way) is even better for Porsche twisties, is it not? The Nice to Cannes drive should be a bit crowded I would think at this time of the year.

Will check revs later.

Wayne 993TT in France

Mmm,

maybe somethings afoot then. Mine definitly does'nt climb that quickly. Does anyone know if there's anything that could relate to this?

My fav roads around here, are the ones in the mountains, very twisty with some nice straights here and there, and v. quiet. I'm off to do the Col de Torin this weekend, just behind Monte-Carlo. You definitly right about the traffic at the moment , but I have a couple of 'fun' roads on the way to work, and as I'm always late they're v. quiet.

cheers

Ran

Wayne,

in 5th gear while cruising along, from 0.0 bar at ~3000/3100 rpm, flooring resulted in 0.8 at about 3700/3800. Did not check rpms in other gears when reaching 0.8 but that seemed pretty quick to me. I still did not have the kind of road needed today to test out 2nd gear boost though I could check rpm too in 3rd and 4th if interested. How about you check out your 5th gear response to compare. Earlier post gives 3rd and 4th gear boost but not rpm.

Hope this helps.

BTW, dont be too sure that " somethings afoot" based on my observations 'cause I think there are others on this board who may have a better understanding of things. I'm relatively new to the turbo.

SundayDriver

Wayne,

I had a problem, some time ago, where the passage between the manifold and pressure sensor got clogged. The ECU limited the boost. It was slow to come up and would not exceed .5 or .6 bar. You might have a look at that or the sensor could be bad. You should see .8 very quickly. .8 is the mas that the sensor will report, so no matter what you do, in terms of mods, you will not see higher than that. The ECU does limit the boost, based on temperatures and of course inputs from the knock sensors. When the engine is cold, I do not think you will get full boost.

Hope this helps.

Wayne 993TT in France

Thanks for that,

I took it into my specialist here, and descibed the observations that I had made, and the first thing he said was on highish milage cars (mine about 46K) is was quite a common problem. He said he'll have a look, so hopefully I know more tomorrow.

Thanks,
Wayne

Wayne 993TT in France

Just to let you know, everyting was fine it was just me being paranoid. So just got to get a new set of tyres now...

Rick in Portland

Hi Wayne,

Keep in mind that the turbos create faster boost levels under higher loads. In my previous 993TT, I would see .8 Bar above 4500 RPM in 2nd, but in 3rd or 4th, I would see it at a much lower RPM because there was a heavier load.

Or, if I went up a steep hill in 2nd, I could hit .8 Bar much lower than 4500 RPM. What you are seeing is normal.

Rick

Vreracing

In my TT, I found if I used 104 Octane racing fuel it seemed to shoot up to .8 boost much faster than with standard gas.

Rick in Portland

That would only happen if the ECU was retarding the ignition because of excessive heat. 92/93 octane will produce maximum power under normal conditions.

I bet you wouldn't see any difference on a cold day.

Rick