98 saab 9k cse

[ks13]

I searched but couldnt find anything. Is fuel cut 15.5 psi on my cse. Im a newbie, dont flame me. I know nissans well not saabs. Anyways, today I borrowed my friends MBC and toyed with it a bit. I only hit fuel cut once in 4th, backed off on the controller and didnt have any problems, no pigging or anything. The needle spikes past red in 3rd and 4th, how much boost is top of red? I dont hold it fully boosted for more than 2-3 seconds at a time cause Im worried about fuel. Am I running on the ragged edge, or should I just keep on truckin. No mods by the way, bone stock.

[zeke]

You're running on the edge. It's hard to say what boost pressure you're getting without a calibrated boost gauge fitted. I know the MAP sensor can only read up to ~21 psi, so the fuel-cut has to be below that - maybe 18-19 psi. A stock B234R should boost to 15-16 psi, depending on the abient conditions (pres. & temp.). Just make sure you're running the highest octane you can find (Shell and Sunoco are pretty good gas) and don't try any extended WOT's. The stock downpipe isn't really that great a design and is a huge contributor to high EGT's, even without the MBC. Put a 3" downpipe on there and the EGT's will drop considerably and will give you a little more safety margin. Just remember this: by using the MBC, you've over-riden the APC system, so if you get a bad batch of gas and it starts to knock, there's likely to be a bang

[ks13]

by using the MBC, you've over-riden the APC system, so if you get a bad batch of gas and it starts to knock, there's likely to be a bang[/QUOTE]


So your saying that poor fuel octane could lead to detonation, or is knock something else entirely?

[saabkid37]

low octane can lead to knock and detonation at high boost. Stock fuel cut from my experiences is 20-21 psi...

[ks13]

fuel cut is just a single sudden jolt correct? What would detonation feel like? would I not hear pinging first warning me that detonation is more likely to occur?

[Robinb]

Knock is just another word for detonation, and if your hear a pinging (i.e. knocking) sound, detonation isn't about to begin, it's already happening.

Detonation is pre-ignition due to poor-quality (low octane) fuel being overheated by compression and exploding too early. Temperatures begin to rise, and major damage to the pistons will soon follow.

[ks13]

so with this MBC overriding my APC, would it affect the outside air temp gauge under my speedo? It seems to have been off by quite a bit the past few days. Today at one point it was telling me that it was like 50 degrees out when it was prolly 35 tops. Is this related to the boost controller or is it just coincidental. Also, while idling at stoplights, once in a while it feels almost like a misfire or something, hickup....i dont know how to explain. Over the past few days Ive noticed it occuring more, and dont know what to think. Ignition? No check engine lights are illuminated.

[ks13]

OK sounds good. I'll just keep 'er wooded till a bad case of the knocks sends her to saab heaven.