Ziad

Hi, I need so me help...

When I floor the accelerator the power from the Turbos builds and builds, but suddenly, and only for an instant, the power goes, the turbos feel like they are cutting out; and the power comes back in (all the way to the red line). The cut happens for a split second between 4.5k-5.5k RPM (not sure exactly), but it is not the same as when the waste gates open up - this is very different. I only remember it ever happening in 3rd gear and it happens occasionally, usually on the first hard run but not always.

It feels like the loss of power could be due to a wheel spin. It is very noticeable – in fact, last time Jean was with me, he noticed it as well, we weren’t sure what it was, but thought it was the clutch, however now, I don't think it is...

A friend of mine with a 993tt (430hp factory upgrade) had the very same thing just recently – can anyone shed some light on this?

Thanks

Basal Skull

Hi I'm not sure it's the same thing you're describing but I had something similar and adjusting the wastegates ast Kevin suggested improved things for my car. see https://rennlist.com/forums/showthre...ferrerid=28499

911/Q45

MAF sensor could do it too.

Kevin

MAF, plug and plug wires.. What is your octane.. You are going thru peak torque.. The ignition system has to be running perfect in high temps and high boost..

Stummel

I had this when I used lower octane fuel in winter and then went back for the better fuel.

Ziad

Guys, thank you all for your input, this has given me a few things to checkout

Basal
Thank you, I will look at the link and see if this could be the problem

911/Q45
I installed a new MAF in March

Kevin
All the components you mentioned were installed in March when I bought your Stage-1, inclu new MAF, ignition, wires, plugs... the works. The octane on the other hand is not so good. It is labelled as 95 Octane, but in reality it is more like 93. That is the highest octane available for sale here, apart from race fuel, which has to be bought in big contrainers and requires storage. And incidentally, it has never ever happened with race fuel!!!

Stummel
Sounds like that is what is probably causing it....

Thanks again for all your input!!!

Best regards,

Red rooster

Fault codes logged in the DME ? Could be simple ,boost level exceeded !!

Geoff

Kevin

Ziad, this programming is will allow for Motronic "overboost" when conditions permit.. One condition that is monitored is your inlet intake temp, the other is your #3 cylinder head temp sensor. If you are running poor fuel and any of your temps are high boost and timing will be "pulled"

Look if you are running in 100 degrees F outside, you need to run a higher grade fuel for maximum perfromance.. You should be extremely please that your ECU programming is "saving" you engine..

BTW you answered your own question with the statement that when you ran race fuel the problem went away.. I'd suggest running 3-5 gallons of 100 octane in your mid-grade fuel..

As Geoff mentioned, if your car is over-boosting due to a bad hose, or actuator you will get the shutter in this RPM band.. If you install a boost gauge in the car you will be able to monitor it..

If you have good fuel and good temps, you should see 1.2 and 1.25 bars...

Ziad

Thanks again guys

Geoff,
Not sure if the fault codes are logged Kevin?

Kevin, the problem I have happens occasionally and can't be reproduced at will, but when it does happen, it is very noticeable. I have never had the problem with race fuel cos I only use it on track day, + I could also go quite a while with poorer quality fuel without having the problem. My complaint is that I had no idea what could be causing it and the fact that a friend with a 430hp factory upgrade has also experienced the same thing suggests a common factor... What you have said about the fuel makes sense... I will see if I can drive for a couple of weeks or so on higer octane to see what happens.

Cheers

Jean

Kevin
The cutoff that is taking place is unlike an ECU pulling timing and boost due to knock, which would be more like a power loss, not such a noticeable cutoff. There is a clear hickup which makes me think of either "uncontrolled" overboost spike or some other fueling or electrical issue. What do you think?

Ziad, as Geoff mentioned, it would be a good idea to plug a hammer at the dealer and check out the codes.

BTW, your fuel in Bahrain is much better than what we have here, yet modded cars here are not having this problem. I run my car with pump fuel (90 octane at best) 95% of the times, yet at stock 0.7Bar boost that is.

Kevin

Ziad, have you replaced your wiring harness? I would at least check the wiring bundle and check the condition of the insulation.

If it is a uncontrolled boost spike Ziad you have to install a boost gauge to check the boost. Check to see if your N75 frequency valve is working. This valve controls your wastegate actuators. Are you running a oil K&N filter?

Ziad

Hi Jean,
I'll take the car down today so they can have a look at the ECU... Thanks Jean.

Kevin,
I'll have the wiring checked and the N75 frequency valve. I'm running stock oil filters. Thanks

Will let you know

TB993tt

It sounds to me like it is the boost spiking just that little bit too high and an ignition limiter cuts in, feels a bit like the rev limiter but cuts in until the boost drops then power returns. It happens around peak torque as the Motronic allows the boost to run up. My car does it now and did it before with my last set up. I think it just a slight flaw in the Motronic as it can't control the wastegate/boost quite as finely with the more aggressive mapping and sometimes the boost just overshoots the target and causes the cutout.

Like I said I get it occasionally and it is no big deal - just a sign that the programming is pushing it to the max.
As Kevin said other things like fuel will affect this and may make it happen more often as the limits are hit sooner.

Ziad

TB

Thanks for your input. I also get it occasionally and at least now I have a much better idea of what is going on...

I'll be taking my car in next week to check the wiring, ECU and other bits that may also contribute.

Cheers

Felix

Hi Ziad, did you ever get to the bottom of this?