E-55

Well I finally got my CAI LTFT issues settled with a conservative tune..now LTFT's are about -2 and WOT A/F ratio is 12.6. However this is with a screened MAF...I could not get nearly the above numbers with my descreened MAF...and no I don't have a clue why. My dual nozzle set up is mounted about 3''s from MAF (Blackwing ala Robert)and are straight shooters aimed to mid plenum ( a point that is 5''s in front of MAF)..my nitrous A/F start at 12.2 but go quickly to 11.5.

Am I Ok to stay screened or should I start over with another tune which I must admit I dread! I'm running a 100 shot. I can see that if nozzles were pointed in the direction of the MAF that the screen would ice but I can't see how it would pointed mid plenum.

Please advise...Robert, Beer, et al thanks in advance..this forum has been a godsend.

Beer99C5

iTrader: (21)

I descreened with no issues to the stock tune and started to spray soon after. Therefore I cannot say if your going to freeze up or not.

Give it a try (ala Mythbusters style!). I agree shooting in the middle of the air cleaner should be far enough for it to blend with the air temp and probably get through the screeen with no trouble.

From looking at a 100 shot log with a Blackwing (my nozzles are 90's that collide at the opening) IAT was 63 before spray and got down to 37 during (Probably a 40 -50 degree day outside in Oct)...

E-55

Beer, you got me thinking. So I made an experiment....I took the stock C6 airbridge and placed the screen from my descreened MAF in the neck...I then connected two hair dryers to the air filter intake ports and taped them tight. Now to the results.....if the nozzle is 90 degrees and points to the screen even a bit (3 in from screen) it frosts , ice particles get caught and restriction is guaranteed. However if the nozzles are straight shooter and point to the mid plenum of the air bridge (5'' from Maf) then there is very minor frost around rim but the air passages in the honeycomb remain completely open and only a fleck or to of ice is caught...certainly not enough to cause restriction.

It is my opinion that with an open design filter such as the Blackwing and spraying into the airbridge plenum will not ice the screen. Myth ? busted.

I'd love to hear opinions on this....

E-55

The more I think about this whole descreened MAF issue the more confusion I have. I have done literally hours of internet searches on this issue but have come up with only "you just do it with dry"...undoubtedly if you are pointing the nozzles anywhere near the MAF screen it would/might freeze,however, I can't for the life of me see how spraying into the airbridge plenum in the opposite direction of the MAF could cause issues with shots on the order of 100 hp. How could it freeze up once mixed with ambient air? I wonder under the above described circumstances that this may be an urban legend.

Robert56

iTrader: (2)

Well if it freezes up on ya and you have problems, then you can blame your Myth Buster's busted. I don't think your test is an end all for leaving screen in place. I also have taken mine out with no issues. Your test may be more flawed than we think; isn't the hair dryers pretty damn hot? and hardly comparable to the amount of air moving on a cold humid day.

Quetions: What MAF is it that you can't get your LTFT in line?
What MAF can you get your ltft in line with screen?

You should be able to tune your screened MAF the same, with or with out a screen. get rid of that restriction anyway.
Robert

E-55

Robert, I would agree...however I went back and hooked up on dryer on each air filter location set on cool so heat was not an issue and as intake air is only going about 45mph I don't think it was much different with two hair dryers at max. I agree that under certain atmospheric conditions there would be a more likely issue. However what did you see for IAT drop when you were spraying mid plenum rather than at MAF? I would think that if IAT is monitored and it did not drop below 28 degrees the chances of freezing would be small. Do you know where the info is on how this descreening issue got started? Was it generated from shot towards the MAF? It just doesn't make sense to me that it would freeze under normal atmospheric conditions.

Robert56

iTrader: (2)

It got started because guys were freezing up the screen. If ya want to take the chance, that's your option. the screen has no use what so ever on our motors, period. The Z06 came without because GM found it to be a restriction when going for additional HP in '02. You may be allright, and you may not, only you can make that call.
Robert

E-55

OK...I'll defer to a mentor....descreened it will be.....

Beer99C5

iTrader: (21)

Did you recalibrate the MAF that was descreened? Its not any harder than redoing the VE tables.

Enable the MAF and log MAF Freq vs {Actual AFR}/{GM.AFR} through the RPM range. Then apply the correction. Log again and keep going til its nailed down.