Hi,
I have a stock 944 turbo S to which I just recently installed a manual boost enhancer (LBE).
Apart from the expected change in boost behaviour, I experienced some increased engine temperature during testing of this mod (15 mins of hard start, stop kinda driving) to the point where the warning light lit up. <img src="graemlins/cussing.gif" border="0" alt="[grrrrrrr]" />
Prior to this mod my engine temp has pretty much sat quitely on the 1st marker, even during track driving.

ANyone else experienced similiar?
I wonder is the turbo itself dumping in the excess heat, or could this be due to the engine possibly running leaner in the mid-range with the earlier boost etc.
Any ideas as to the cause?
cheers.

 

Do you have an aftermarket boost gauge? Most likely you are running too much boost and running lean in the high rpm's!

 

Hi Tom,
I have a stock boost gauge which gets up to the 2 bar (14.5 psi boost) reading which roughly equates to the stock 15psi max boost for the turbo S right?
The LBE is supposedly set to 10psi.
So does an engine running lean generate more heat than when the air-fuel mix is on the mark?
Also I am wondering where the engine temperature gauge is located - if near the turbo could I be seeing a temperary hot-spot in the cooling-system, as the gauge readings are quite jumpy. Another novice question - Does the temperature sensor measure the cooling fluid temp or the engine housing temp?
cheers.

 

my LBE was supposedly set at 10psi, when i got a real boost gauge installed i was actually running 19PSI of boost! if you're going to run that thing i'd suggest getting a boost gauge before you blow up your engine.

 

[quote] I have a stock boost gauge which gets up to the 2 bar (14.5 psi boost) <hr></blockquote>

The stock gauge does not register anything over 1 bar of boost. The stop stick for the needle is at the 2 bar mark. It will not go past it. I did the same as noted above, and tuned a MBC off the stock gauge and fuel off an ARM 1. When I put in a VDO the next day, 24psi.

Luckily I had the fuel to go with it.

 

First off the factory gauge is verry inacurate. Stock boost is somewhere around 13psi I think. It sounds like your car has ben chipped in which case you might have a jetted banjo bolt, which was increasing your boost before you put the LBE on. You should use the factory banjo bolt with the LBE. A little hint about most chips for these cars, they run rich in the middle and lean in the upper rpm's.

The car will run hotter if it is running lean which will cause your car to knock and blow your head gasket. To the best of my knowledge the temp sensor is somewhere near the front of the engine and I think it reads the coolant temp.

 

Hally

if you still have the stock chips and you raise
boost you could have a problem. Depending on the octane rating of the fuel you're using you could be getting slight detonation (normally around peak torque 3250 - 3500 rpm) the knock sensor picks this up and retards timing. The retarded timing causes egt's to go up and the engine runs hotter than normal. remember most of the post's you read talk about 92 octane but thats in the US where they use (RON + MON)/2. The rest of the world use RON only so these guys are talking at least 97 RON.
The stock chips have more agressive timing compared to aftermarket chips as the are only expecting about 10.5 psi boost in the manifold in a stock car.
I speak from experience, I'm running 13 psi in the manifold (both boost and fuelling checked very accurately on the dyno). The highest RON available to me is 93 and the car did run noticeably hotter than at std boost. In my latest tank of gas I am running 93 Leaded plus a 12.5%
toluene/xylene mix (from a local subaru tuner)and with the ambient temp being much the same as before the car is running signifigantly cooler.
Obviously all the comments about checking exactly how much boost you are running are extremely important
<img src="graemlins/yltype.gif" border="0" alt="[typing]" />

 

Some quick clarifications:

- stock boost on both Turbo & TurboS is 0.75-bar (11psi). There's a +/- range that's allowable, so anywhere from 9.5-12psi is considered 'stock'. The TurboS just holds it longer into the high-RPMs without dropping

- the stock guage can be accurate. You have to make sure that the presure line going to the KLR isn't clogged with oil. This is actually pretty common. Disconnect both ends of the hard plastic line going to the KLR and squirt some carb-cleaner through. Aftermarket guage is best though.

"The LBE is supposedly set to 10psi."

- the pressure that a manual boost-controller starts to open, is not the same boost-pressure that will develop inside your intake manifold. Please refer to these threads on wastegate control:
<a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic&f=15&t=010253" target="_blank">Topic: LBE intalled, getting weird readings </a>
<a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=18&t=002698" target="_blank">Topic: Europroducts chip set with LBE. Are shims required? </a>

"The stock chips have more agressive timing compared to aftermarket chips as the are only expecting about 10.5 psi boost in the manifold in a stock car."

Actually it depends upon the chip. AutoThority tends to be sluggish in the mid-range due to their retarded ignition and overly-rich mixture. However, they have more igntion advance under full-throttle. We've seen other chips that are so aggressive in their ignition advance that it's scary (+10 degrees ignition advance over stock everywhere!). Our chips tend to have more advance than stock, yet we can run 40% more boost because the fuel-supply is increased to match.

"I experienced some increased engine temperature during testing of this mod"

Most likely the cause of the extra heat is due to running lean. Very, very easy to burn up a headgasket that way. What kind of chips are you using? Check out this thread: <a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic&f=18&t=002522" target="_blank">Topic: Engine running hotter after installing LBE </a>

BTW, there are bizarre cases of stock 951s, like Luke's top-secret-agent car that can run 17psi on stock chips with no overboost-protection... <img src="confused.gif" border="0">

 

Best bet is to get your car on the dyno, it may seem expensive at first but it's money well spent.
On the dyno I discovered 2 things, at 13 psi my fuelling is safe and that between 1.5 bar and 1.9 bar my stock boost guage under reads consistently by 0.1 bar. Once you know where your guage is you can use it to check any boost mods upto 2 bar (where it pegs). I don't know how expensive dyno time is in Australia, but here the dyno time to find out the above was about 1/4 of the cost of an imported autometer boost guage. <img src="graemlins/yltype.gif" border="0" alt="[typing]" />

 

Thanks for all the quality feedback - this site is awesome.

 

MildMAx, you are only running 13 psi and have to run 12% toloune with 93 octane???? You should be able to run about 16-18psi with that fuel set up. You might want to get your air/fuel checked again. <img src="confused.gif" border="0">

 

Todd

thanks for the concern, but it's that old octane rating system that's confusing the issue. I use 93 RON (that's the best I can get) translating that via rule of thumb to anti knock index or pump octane number, which is what you lucky guys in the USA use, at best I am running 87 Octane (measured by your standards). To make matters worse I live at 5500 ft of altitude, at 13psi of boost I have a pressure ratio of 2.2 vs one of 1.9
(what it would be at sea level), the turbo has to work harder and the charge is hotter and hence more prone to knock.
I am running stock chips with an LBE as my boost adjuster. Based on Danno's original post's on his first mod (13 psi plus a 3bar fpr) this is the config I am trying to optimise. At 10 psi I had no problems, at 13 psi on the dyno the operator picks up a slight rattle (knock)at +- 3300 rpm and the ignition retards (you can see it on the torque curve).
The A/F ratio varies from 12.5 to 11.2 so is OK.
The toluene is to compensate for the crappy gas we get here (you want to hear the Audi S3 boys whining). I don't know if it works yet as I have to get back to the dyno, but giving it boost in stop start conditions, the car is definitely running cooler. The LBE has a much more aggressive boost profile than the gentle roll on of a stock car so this isn't helping, but there's no way I'm going back to that really lazy boost arrival. <img src="graemlins/yltype.gif" border="0" alt="[typing]" />

 

Hey MildMax951, I would also recommend setting your FQS switch position to #3 +6.3% more fuel (stock is #0 full counterclockwise). A 3-bar FPR will only give you 9% more fuel, yet your boost is about 20% higher than stock.

 

Danno

I don't want to get a reputation as yet another owner of a top-secret-agent car. I don't know just how stock my car is. I believe the chips are stock (I haven't looked), but when I first got the car I had a totally non operational bypass valve and could summon up the factory overboost fuel cut at will (fast change from 4th to 5th @ 4500 rpm on the highway). It was the real thing, any further boost limited to about 1.3 bar and cleared by turning ignition off. Replaced the bypass valve with the 993. part no (thanks to rennlist!) problem solved.

The fuel consumption was awful, 16.5 l/ 100 km
(manual quotes 12.7 for urban cycle).
had it checked by a porsche shop, fuel pressure, boost etc was all within in spec. They took it to the dyno operator I now use. It was running hugely rich even at cruise (our cars have no catalyst and no 02 sensor). The air flow meter was very new (you could tell just by looking at it). the Dyno operator adjusted the afm to get reasonable a/f ratios on the dyno. The fuel consumption improved dramatically.

I don't know whether I have a non std afm or perhaps bigger injectors ( porsche parts here are incredibly expensive and I think sometimes some bush mechanic tactics might have been employed by the previous owners).

The end result is with the std 2.5 bar fpr ( I'm not running the 3 bar fpr) I have a car which is running 13 psi in the manifold and goes from around 12.5:1 @ 3000 rpm to about 11.2:1 at 6000
rpm.

Is this feasible or should I be doubting the operators ability to measure a/f ratios accurately
all comments would be much appreciated <img src="graemlins/yltype.gif" border="0" alt="[typing]" />

 

Hmm, interesting. So you've got the opposite problem that most people have (going from too rich to too lean). Yours does the opposite, so it may actually be a blessing. Install the 3-bar FPR and turn up the boost !!!