Injectors

[Badvette87]

Are 30#Injectors to big for my 1987 l-98?my modifications are:
accel runners,ported plenum,58mm throttle body,fuel pressure regulator,1.6 roller rockers.
the idle is very bad with 30# injectors

 

[Edmond]

I'm willing to bet that it's that 58 mm throttle body. There's just no way a 350 cid motor can use that big of a throttle body. One of the members had a 58 on his LT1, switched down to 52 and noticed an improvement.

58 is really overkill while 52 should be enough.

 

[Edmond]

Forgot to mention

If you're not running a high flow air filter with that lid cut open, a 52 mm TB won't do you any good either. I've seen tests at the store where they tested a K&N against a paper filter. They had this clear, plastic tube that had a ping pong ball in it. You turned the fan on and put the K&N air filter in there, the ball went all the way to the top. Then you could put the paper filter in there, the ball went about halfway up.

 

[Badvette87]

i got an open airfilter lid and a k&n filter,i installed the 58mm throttle body befor i bought the injectors and there was no problem.

 

[Edmond]

The air/fuel ratio is something that is extremely important. It's something that takes very careful tuning and most likely will have to be done over and over many times to get right.

You'll be flooded with responses to this issue, I'm sure when everyone gets home and relaxed, they'll help you more than I can.

 

[Badvette87]

should i drop the fuel pressure?

 

[WhalePirot]

Check this: http://www.jimsperformance.com/tech.html

I think both your injectors and your TB are too big.

My 406 is about 550hp, and runs great with a 52mm BBK and 30#/hr. injectors. Injector size is a function of HP.

You can try dropping the fuel pressure, but your spray pattern may be unsat. Different tuners use differing techniques. Some go with sm,aller injectors and higher pressure; others the opposite. Who's right? Ask at the track (or here). Ask the guy who recommended those big sprayers what he'd do!

 

[Edmond]

Pirot,

I thought I was kind of right on those mods he had done. Wow, I've really learned a ton from everyone on this site!

I think it was UB2SLOW who had that 58 and went back to a 52 TB?

Badvette87,

Don't forget that the stock chip will impose serious limits on what those mods can do so you'd better address that issue as well.