do you need a chip when switching to 24lbs injectors.
 

I switched my 91 mustang over to 24lb injectors and 73mm mas air (because of nitrous kit I order to go on very soon) now when i turn the timming up to 15 dagrees and step on the gas lots of smoke comes out the tailpipes. It contuines to do this until i trun the timming down to 8 dagrees then the car wont accelarte at all? All i can think of is the computer needs to be update with a chip to match the injectors I don't know though my first EFI car. (I should have stuck with carbs).

Other mobs the car has is cobra intake, cold air, headers, o/r h-pipe and 2 1/2 inch flowmasters. It is an AOD car.

Thanks for the help.

the 73mm mass air has to be calibrated to the 24kbs injectors

the mass air is calibrated for the injectors or so i was told.:confused:

maybe a problem with the injectors did you buy them used.

did you do the swap yourself , how were the plastic nipples the injectors go into ?

what did you change just before the problem?

I changed the injectors and the mass air is when i got the problem. I got them used and they where in really good shape. I think the computer is makeing the air to fuel ratio to rich when i turn up the timming. Would going to an adjustbale fuel regulator help?

Actually, the computer still thinks you have 19lb injectors, with is normal. The reason for matching the mass-air meter to the injectors is to trick the computer. The mass-air basically tells the computer that its getting a lot less air, making the computer tell the injectors to decrease their pulse width (amount of time the injector is open). Even at the decreased pulse width, the 24lb injectors will shoot close to the same amount of fuel as your stockers, which makes it run correctly at idle and part throttle. This ends up being able to provide more fuel at WOT.

The problem is, its just a guess. Hoping that your mass-air will send the computer information that will allow the injectors to send exactly the right amount of fuel just doesn't work well compared to a custom chip & a little dyno time.

Dont get me wrong, a larger than stock mass-air is definately a plus :) Just saying that after you install a mass-air and injectors, you should head out to a dyno and have them tune it with a wideband.

Good luck
Jeff
www.stangonline.com - Mustang Auctions

I cant believe noone has said anything much about a regulator.
Of course you need a regulator when switching to bigger injectors, i talk to alot of guys at the track running mild cams and aluminum heads with 24's, they say they turn down the pressure.

True. I just assumed that he had one :( I usually do a regulator before anything else. Like he said - get an adjustable regulator and while you are at it, maybe an aftermarket fuel pump, as the stock pumps can barely keep up with the 19lb injectors :(

Even then, consider a chip to fine tune your setup. A few things about chips:

1 - Dont buy one of the out of the box, one fits all chips. They are guessing just like we are when we drop in a massair and injectors. Only get a custom chip tuned by a good shop while you are on the dyno.

2 - The downside is if you make even one little change to your engine, the chip is probably not optimal any longer and more dyno time is in order.

3 - Man this hobby is expensive!

Jeff
www.stangonline.com - Mustang Auctions

And a fuel pressure guage!! :) Its never ending - once you start, you just cant stop!

Jeff
www.stangonline.com - Mustang Auctions