09-12-2012, 11:31 AM #1Member
- Join Date
- Feb 2010
- Rep Points
- 17 Post(s)
- Rep Power
Some Cobb questions - methanol, boost oscillations, etc.
I finally have a Cobb installed. It doesn't seem to be running perfectly, but it does run better than I was expecting.
I would like to get some baselines before attempting some custom tuning with PTF, etc.
My first quesiton is: can I run the Cobb Beta Race map (4.02) with methanol (preferably 50/50 mix water/methanol by volume) ? I have a HFS-4 installed with 2x1.2mm nozzles, right now I am using it in on-off mode and about 60/40 water/meth because that is what my former GIAC seemed to be happy with. But I would like to switch it back to PWM mode, what knob settings should I use ?
The second question is, how do the boost oscillations feel ? Is there any sound associated with them, or only some jerking ?
09-12-2012, 11:50 AM #2
If i understand you, you're spraying meth on the OTS aggresive maps? You're probably losing some power if so.
Boost oscillations can be heard and felt. The car will pull hard, then back off and then pull again. If running a BOV you'll hear it discharging during the oscillations. Get some datalogs and we can confirm if you're having some oscillations.
MOTIV750, MOTIV P-1000 PI, MOTIV/FUEL-IT! low pressure fuel system, AEM EMS/COBB AP, Aquamist HFS-3, ETS FMIC, SPEC stage 3+ clutch/SS flywheel, BC Racing coilovers and VMR wheels wrapped in Hankook RS3s.
09-12-2012, 11:57 AM #3
@cstavaru, glad you got it working finally.
In terms of the OTS race/e30 map I wouldn't recommend using it blindly with methanol. Definitely try it but I suspect it may turn out to be a bit much on the timing front given meth distribution isn't nearly as perfect as direct injecting E85 or race gas into the cylinders and you may/may not encounter timing corrections indicating too hot of a timing map.
With the v402 maps you "shouldn't" have boost oscillations due to the reworked boost PID control. If you do get issues, as @rader1 pointed out, you will most likely be able to hear it as throttle will fluctuate due to boost overshoot/undershoot at WOT onset in the lower RPM range (3-4k range). Having said that, I don't expect to see issues on V402 as that has been solved.
In terms of the HFS-4 meth kit I'd suggest moving the nozzles down near the FMIC outlet. This will allow for more time for meth/water to atomize. Dual 1.2mm nozzles are a bit much for stock turbos and given a 60/40 mix you are injecting more water than you'd need and possibly losing some power. My advice would be not to go above dual 1.0mm nozzles on stock turbos. PWM mode will work just fine in default settings. On my car with RBs I do move the THRES knob a tiny bit counter clockwise to have it turn on a bit sooner than default.
Glad you decided to try out Cobb for yourself knowing you really did enjoy your GIAC tune. At least now you have the option of customizing the tune fully to your liking, modifications, octane etc. without a compromise.
09-12-2012, 12:17 PM #4
Im running the the Cobb beta Race maps with dual 1.0 mm nozzles and HFS-4. Just make sure you aren't running the E30 maps. I have it running the default PWM settings, but i believe i would benefit from setting this to engage a little sooner, as DZ stated. My car runs great on these maps, but i sometimes get some tip in timing corrections. Definately get your failsafe hooked up though, these maps run quite a bit more timing than GIAC, so having the DME as the only failsafe is ill advised.