Help with injector, maf and t/b sizing

DarkProphet · Jul 31, 2005

can anyone help me?

a50sn95 · Jul 31, 2005

36's should be ok for stock heads. If you ever upgrade, though, you'll need bigger.
That said, if you go bigger than 36's you'll also likely have startup and drivability issues. 42's are notorious for this.
The Cobra intake will have to be matched to a 75mm TB, maybe even a 70. This change will also bring idling issues, as it will have more airflow at idle and maybe enough to get out of the range that the computer can compensate for.
I think I'd get the 36's for now.
If you have a 73mm MAF, and a 75mm TB, then the MAF becomes a bottleneck.
A free MAF is nothing to sneeze at, so I think I would use it.
Also, do you have a way to control timing, as you'll likely see some detonation, if you don't already. 9lbs is where Powerdyne started adding stuff to their kits.
Dennis

DarkProphet · Aug 1, 2005

well i have the bypass kit and a 255 lph fuel pump. I have no way of changing the timing now, but it will go up for a custom chip and dyno tune soon after being completed.

Which would you suggest as far as the throttle body? the 70 or 75?

Black95GTS · Aug 1, 2005

75mm TB. Seems to me, in general, that the more air in = more air out = more horsepower, especially with a poweradder when you're trying to stuff air in as fast as possible.

just my two cents, I don't have a power adder, just seems to make sense to this guy.

- adam

Green 94 5.0 · Aug 1, 2005

bigger is not always better. 36's and a 70mm t/b will work just fine. with the bd11a and the 9lb pulley, i was not able to see more than 7psi. i had 42's, a 255lph in tank pump, and the stock mass air meter (compensation for injectors was done with a tweecer) at the time and was running pig rich. even still though, an msd btm would be a good choice to help prevent any boost/timing related problems.

final5-0 · Aug 1, 2005

Green 94 5.0 said:
bigger is not always better. 36's and a 70mm t/b will work just fine. with the bd11a and the 9lb pulley, i was not able to see more than 7psi. i had 42's, a 255lph in tank pump, and the stock mass air meter (compensation for injectors was done with a tweecer) at the time and was running pig rich. even still though, an msd btm would be a good choice to help prevent any boost/timing related problems.

With the blower, how did you keep from pegging the stock maf???????????

Later
Grady

DarkProphet · Aug 1, 2005

would i need the MSD BTM if im going to get a custom chip burned? that should take care of all the timing correct?

a50sn95 · Aug 1, 2005

No, just don't get on it. You will detonate....

94opalgt · Aug 2, 2005

is it just me or doesnt this guy need a blow through,or whatever its called,maf?and,correct me if i am wrong,but i thought i read somewhere that the general rule of thumb was to keep the maf 5-10mm bigger than the tb?i think george klass,the guy that runs accufab,said that.as stated by a50sn95 the maf becomes the bottle neck and you do not want that,so if it was me i would get a bigger maf,maybe 80mm pro-m.but thats just my .02.the cobra intake will take a 70mm tb,inlet on all cobra intakes is 70mm.if you use a 75mm tb you will have to match the inlet to the tb.i think the only intake made with a 75mm inlet is the tfs intakes.

Green 94 5.0 · Aug 2, 2005

since the mass air meter is before the blower and sees no boost, a blow through is not necessary. as far as the meter needing to be 5-10mm bigger than the throttle body, i havent heard that before. hopefully someone that knows for certain chimes in soon since im about to pick up my meter, throttle body, and a few other odds and ends.

94opalgt · Aug 2, 2005

http://bbs.hardcore50.com/vbulletin/showthread.php?t=26335&highlight=size+throttle+body
i dont know if i did that right,but that is the thread i think i got the info about the maf being bigger than the tb at.anyways,read it before you buy your tb.i got alot of use full info from this thread.i hope it helps some other people out also.if its not in this thread,i know i read about it on that site

DarkProphet · Aug 2, 2005

thanks for the link! it helped out alot as far as TB sizing. It didnt mention anything about a maf that I saw, but i could have missed it. I am just going ot be going with a 70mm TB. The 73mm maf should be an 80 i know, but it was free.... so i wont complain for now...

94opalgt · Aug 2, 2005

i wouldnt complain either.the 70mm is what i ended up going with.man i know i read that on that site,now im going to have to search it and if i find it i'll post the link.good luck

Help with injector, maf and t/b sizing

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