Magna Charger

**lyle8206** · 01-15-2010, 03:37 AM

Hello guys, i just picked up a 2003 Z06 with a Magna Charger, Meth injection and a cam. The car produces 558rwhp on a speed density tune. At 2200rpm the car stumbles, you can accelerate through 2200 or cruise at 2100 or 2300 with no problems, but stating at 2200 doesn't work. The guy I bought the car from claimed it was what people claim as the Magnuson stumble. Any of you guys hear about this. Thanks.

**DIRTY JERZY** · 01-15-2010, 04:47 AM

? Sounds like it needs a better tune

**c5z28** · 01-15-2010, 12:58 PM

Where did you buy it from? Problem with speed density is if the conditions are different then when it was tuned your screwed-like mountain driving for instance.

**lyle8206** · 01-15-2010, 06:48 PM

Yes, the car was tuned in Mass. and I have the car down in Texas, so that could easily be my problem. Thanks.

**c5z28** · 01-15-2010, 10:38 PM

Originally Posted by lyle8206

Yes, the car was tuned in Mass. and I have the car down in Texas, so that could easily be my problem. Thanks.

Show it by posting some pics of the ride

**Frost** · 01-16-2010, 05:29 AM

It IS the magnusson stumble... It happens between 1800-2200 RPMs from what I have seen. The lower intake must cause some turbulence around that area. When logging, one bank of fueling wanders lean while the other wanders rich. If the VE is fully tuned, having LTFTs disabled usually helps a bit. Some are worse than others about it. The higher your blower is pullied, the generally more pronounced it is. I have seen it on everyone of them. There is no tuning around something like that.

**Frost** · 01-16-2010, 05:31 AM

Originally Posted by c5z28

Where did you buy it from? Problem with speed density is if the conditions are different then when it was tuned your screwed-like mountain driving for instance.

That's an internet myth that NEEDS to die.

The car has a MAP sensor. MAP sensors measure the pressure of the atmosphere around them. Speed density is based around this sensor. I can tune a car here and drive it to the mountains and everything is still fine because I take the time to really calibrate.

**c5z28** · 01-16-2010, 11:43 AM

Originally Posted by Frost

That's an internet myth that NEEDS to die.

The car has a MAP sensor. MAP sensors measure the pressure of the atmosphere around them. Speed density is based around this sensor. I can tune a car here and drive it to the mountains and everything is still fine because I take the time to really calibrate.

Our tuners are lazy

**lyle8206** · 01-17-2010, 06:33 AM

Thanks Steve, the guy I bought the car from told me about the Magnuson stumble but I could not find anything about it online. You put my mind at ease.

**Frost** · 01-17-2010, 12:03 PM

I've never seen much discussion about it (though there is a little in one thread over at HPT) but it's real... One bank of fueling completely wanders off in that area. We don't have left/right bank control either, so there really is nothing that can be done as far as tuning.

**Night Move** · 01-27-2010, 04:11 PM

Mine doesn't do it, maybe lucky, speed density setup, tuned by MTI in Marietta, GA. 770-919-7774. I believe the guys name is Reece. After install,hauled it down there on role back left it for about 10 days. That was a year ago, still no problems.

**Wesman** · 01-27-2010, 07:06 PM

Originally Posted by Frost

That's an internet myth that NEEDS to die.

The car has a MAP sensor. MAP sensors measure the pressure of the atmosphere around them. Speed density is based around this sensor. I can tune a car here and drive it to the mountains and everything is still fine because I take the time to really calibrate.

Do the MAP sensors on our car recalibrate for the atmospheric pressure in real time??

I know on some older cars with MAP sensors, if you started the car in a low elevation and then drove up a mountain, the car would run like crap because it wouldn't adjust for the new baro reading until the next key cycle.

**Frost** · 01-27-2010, 09:21 PM

Originally Posted by Night Move

Mine doesn't do it, maybe lucky, speed density setup, tuned by MTI in Marietta, GA. 770-919-7774. I believe the guys name is Reece. After install,hauled it down there on role back left it for about 10 days. That was a year ago, still no problems.

I bet big money it happens, it just doesn't cause any rough feeling in many cars. Something happens and the fuel trims for one bank wander off in one direction and the other goes the other way. In fact, 5 out of 6 cars with these blowers experience nothing odd there that can be felt, but it is definitely there.

Originally Posted by Wesman

Do the MAP sensors on our car recalibrate for the atmospheric pressure in real time??

I know on some older cars with MAP sensors, if you started the car in a low elevation and then drove up a mountain, the car would run like crap because it wouldn't adjust for the new baro reading until the next key cycle.

Never seen or heard of a problem such as this with the GENIII cars.