Overboost Question

[skendrick]

Hi, can anyone help me with my turbo overboosting and cutting out my engine. I recently found that I have a 'Boost Enhancer' on my 944 turbo and during the summer I decided to turn it up a couple of notches to see the difference. [] Wow, manure and shovel sprang to mind when I pressed the loud peddle, until the engine cut out 30 seconds later []. Started the car back up, whent home sensibly and de-tuned the car back down.

I haven't been using my car reguarly for the last 6 weeks as my wife gave birth to our second child (well, through the sun roof), so I've been using her car. I took my car out the weekend and gave it a burst of power only to find the turbo overboosted and cut out the engine again. Maybe I need to turn it down one more notch but I was wandering do you get more pressure in hot weather or cold because if you get more pressure in the cold then this will need to be turned down anther notch for the winter and I don't want to miss out on that additional power.

Does anyone know the answer or have a similar problem?

Thanks for reading

Steve

 

[skendrick]

Thanks Andrew, it looks like I will need to drop the boost enhancer another notch for the time being while I save up for the PP1 (just had the cills done so no money for few months).

Steve

 

[Fen]

Do you use Optimax? When I had a BE (long ago, first step of that slippery slope []) I tweaked it to the point it was just OK on Optimax but overboost triggered all the time on normal unleaded. Please don't say you use supermarket cheap fuel...

 

[sawood12]

Steve,
This may sound a bit daft (and is probably a long shot) but are you sure you are getting overboost. I fitted a DPW but am running std chips and because the boost comes on so quickly I found the revs were rising so much quicker and I was hitting the rev limiter unexpectidly which gives a similar effect but not as severe. I feared overboost at the time until I happened to be looking at the rev counter when it happened once to find the needle in the red! I guess the boost enhancer will behave in a similar fashion as the DPW so you might just be getting caught out with the rev limiter.

I've since recalibrated myself but have experienced a couple of overboost's in cold weather as Andrew has suggested so am currenlty saving for the chip and 3b FPR. It's only been a problem on those cold crisp wintery mornings so you could re-fit your boost enhancer and drive less enthusiastically in cold weather until you get chipped up.

 

[Diver944]

Steve, I used to turn my BE up and down a notch depending on winter or summer when on the standard chips.

Just remember to get used to which way to turn it or you could make it even worse []

 

[skendrick]

Fen,

I normally fill up at Shell but I do not use Optimax.
How much better is Optimax, some say you get better mpg and performance?

Steve

 

[skendrick]

Scot,

I'm not hitting the rev limiter as this normally occurs when I'm in third ready to overtake one or two cars. I get 3/4 of the way past and then it happens, a split second of drop in power . Also the car would not cut out 1 mile up the road if I hit the rev limiter, would it?

All this started when I tweeked the Boost Enhancer.

Steve

 

[skendrick]

Paul,

I think once this problem is sorted I will not be touching it again.

Steve

 

[944turboS]

Steve,
Take a look at this page it has on page 11 of the PDF the adjustment instructions for the Accuboost device which I think works in the same way as the Boost Enhancers. It may help you by going right back & starting again.

http://www.speed-6.com/accuboost.pdf

Good luck
Graeme

 

[Fen]

Try Optimax for one fill - I bet the overboost goes away. I don't think it's triggered as Andrew suggested (by exceeding 0.82 bar absolute) but by the knock sensor and if you are only just getting it with 95RON you will not get it with 98RON.

I don't use Optimax in my 306 as it I don't see the benfit there but in an car that is in any way tweaked it is well worth the extra IMO. That includes BE equipped Turbos, chipped S2s or anything more extreme. My Turbo was mapped on Esso SUL as the worst fuel it will ever run so I now can't use regular unleaded for fear of knock. Even BP Ultimate is supposedly too poor according to the guy who mapped it.

 

[sawood12]

Steve, sounds strange - on the odd occasion that i've had overboost the car has never cut out. I just continue my journey, albeit a little more light footed, without further incident.

Fen, I didn't think that our ECU's could handle anything more than 95 RON fuel so those extra RONS you get with Optimax are wasted as the ECU cannot unlock the extra power or fuel economy you could get with Optimax?

 

[Diver944]

Scott, both the S2 and Turbo have knock sensors and the ECU will automatically advance the ignition right until the point of knock and then reign it back in a bit.

They can both take advantage of a higher RON value fuel in both economy and performance (albeit very minor). Perhaps we should do a back to back test at next years Dyno Day, because until then its really only theory amongst us internet forum 'experts' []

 

[Hilux]

on the odd occasion that i've had overboost the car has never cut out

Good point,

Steve, do you mean the engine `cuts back` severely but can be driven gently until it resets itself or do you mean it actually stops running?

 

[eastendr]

DME will only retard timing by 6 degrees for duration of knock.

(assuming that the knock sensor is working correctly - a lot have probably long since failed if my 944T and 944S were anything to go by ...)

edited for spilling !

 

[944turboS]

When I lived in New Zealand I was fortunate in having access to 100RON aviation fuel (avgas) which I ran my 220hp Turbo on. If I was more than a tank full away from home & had to fill up with "ordinery 95RON" fuel I'm sure the car was less responsive on pickup almost to the point of feeling restricted.

 

[skendrick]

Hilux,

You are correct but when I slow down it cuts out on me. I just start it back up again and it's fine. I have spoken to the guy that services my car and he said it sound like the wastegate it sticking.[] Ouch, that's gonna cost.

Looking for a company that refurbs wastegates anyone know?

Steven

 

[Hilux]

when I slow down it cuts out on me.

Dont quote me on this but when mine did this the first couple of times I pulled over and the car cut out but only at idle. I started it up and it was fine (reset) I understand that the ECU resets itself after 1) a period of slower driving 2) if stopped and started (I`m looking to others to confirm)

I cant see that my issues were waste gate related as I adjusted the Promax boost adjuster as instructed and the symptoms disappeared completely.

 

[Diver944]

ORIGINAL: skendrick


Looking for a company that refurbs wastegates anyone know?

www.speedforceracing.com sell a 38mm TiAL wastegate and adaptor plates for 944 fitment for circa $370 plus shipping and import. A few of us bought these as part of a group buy on Rennlist for considerably less. Make sure the bolts on the adaptor plates are done up tightly before installation []

Another user on Rennlist called MySwiss also sells the TiAL wastegate with his own adaptor plates. Quite often he and Speedforce get into a bit of a price war if you can time it right []

You can then sell your old Porsche wastegate for up to £100 (like I did). Also, I think Andrew at www.Promaxmotorsport.co.uk will often buy them for refurbishment in to a Lindsey dual port wastegate

 

[Fen]

Mine reset itself after 20 to 30 seconds of taking it really easy. I never stopped to find out if it would cut out but I doubt it would have; it was just running a safety setting but still running properly. I take it your service guy means sticking closed? That doesn't sound at all likely to me because if it sticks fully closed you'd hit overboost all the time and if it is stuck part open you'd struggle to make boost. I guess it could be cracked open or leaking just enough to give similar symptoms but I doubt you'd make boost very quickly like that, boost enhancer or not. Standard wastegates crack. Personally I wouldn't pay even £100 for a used one and I wasn't comfortable buying a modified one even though it had been crack tested. If it is the wastegate I'd do what Paul suggests and get a TiAL. I think MySwiss fell foul of the Rennlist ban on selling without being a sponsor though so the days of the price war may well be over.

 

[skendrick]

I have decided to take the BE off the car this weekend and see what happens. What I have noticed is that my BAR pressure goes straight to 2 and doesn't drop at all, is this normal?

Promax do a duel port waste gate with manual boost controller for £400 and I will check out the other two websites as well.

Steve