21.5lb or 24lb injectors??

[rmani]

Looking for some feedback. I plan on upgrading my car with a 540HFM, CAI, Full SS Headers/Resonator/Catback, injectors, and a chip. What size injectors would you recommend as well as chip for this setup. I saw that Turner Motorsports only offers a chip for 24lb injectors, but what chip and injectors setup should I get? Thank you for any input provided. :wave

[andylv]

Many people run 17lb injectors with 540 HFM with no problem provided the correct chip is used and the 17lb injectors are in good shape. BMW when they bumped the displacement on the M3 engines from 3.0L to 3.2L increased the injector size from 17lb to 21lb. Based on that fact I figure the 17lb injectors are close to being at capacity in the a 540 HFM 3.0L setup anything wrong with the injectors may cause lean AF condtions.

Before I moneyshifted my 3.0L I added a 540 HFM, chip, and 24lb injectors. My car had 73,000m miles on it at the time and I figured the injectors probably needed cleaning by then. It cost less to buy the 24lb injectors new than to get my 17lb injectors cleaned so I went with the 24lb injectors.

I bought the injectors off this forum from GQ_Style and bought my chip from Chuck Stickley http://www.cssmotorsports.com/contact.htm. When I switched over to a 3.2L I upgraded my chip through Chuck Stickley for $150 everything else was reused.

I paid:
$150 injectors
$175 540 HFM
$250 chip
$150 for CAI from cosmosm3 on this forum.

[Armo95]

17lbs are sufficient provided the correct software for the setup you're looking into now.

The only reason you would need to upgrade to 21.5# or 24# injectors is if you decide to do cams.

[rmani]

Hmm thanks for the input guys. I searched over some old posts and a lot of people seem to recommend upgrading the injectors when you go with the 3.5 HFM and intake. Figured better safe than sorry; I don't wanna risk running lean and ruining the engine. Any more recommendations and input? :help

[rmani]

hey andylv thanks for the link to CSS motorsports I didn't realize they were close to where I live. Do they make custom chips or are they just pre-programmed for different car setups? Also do they offer any dyno tuning?

[Armo95]

hey andylv thanks for the link to CSS motorsports I didn't realize they were close to where I live. Do they make custom chips or are they just pre-programmed for different car setups? Also do they offer any dyno tuning?

Chuck Stickley does EVERYTHING!!!! Call them or email them. He's the best tuner in the country for our cars:)

See my sig...

[rmani]

just emailed him Armo, thanks.

[rmani]

O yeah forgot to add is it safe to drive the car if I install the HFM and CAI and then drive to CSS to get the chip put in?

[Armo95]

I'm not sure if the car will even run and if it does, it will run horribly...as in it won't be driveable.

[RRSperry]

The stock injestors are fine untill you get to about 270 BHp (crank) adding the headers, TP, and exhaust, along with the intake and HFM will be over that. Get the 24# injectors, you will need them for the cams later anyway.

You could install the injectors, and drive carefully to Chucks place. Install the HFM and intake, and then tune away. The bigger injectors will not hurt the engine with stock software. It will run rich, and your cats may get hot, but drive like a sane man and it should be ok.

[rmani]

Hmm I don't mind taking everything to CSS to have them do the install, it's just that I know the HFM and CAI are easy installs so if they're gonna want a lot of money for the install I might as well save some money and install them myself. We'll see I'm still waiting for them to write me back.

[slcook54]

Take into consideration currently that AA tunes for the 21.5 and conforti for the 24 lb'ers. I don't have any experience with stickley.

[rmani]

yeah I realize the 24lb would be better if I do decide to upgrade to cams, but for the meantime i'm not planning on it. i might give AA a call after I talk to Stickley. I'd rather go with someone nearby in case I have any problems, but I'm also looking for more conservative tuning since I want my engine to last.

[GQ_Style]

17lbs are sufficient provided the correct software for the setup you're looking into now.

The only reason you would need to upgrade to 21.5# or 24# injectors is if you decide to do cams.

I would agree with this with caveats.

If you have access to 93 octane or higher gas, by all mean the 17# injectors are fine. If you run donkey piss 91 octane MTBE ethamethahol here in California, you can benefit from the added buffer of being able to run slightly rich near the higher RPM's.

I personally had pinging issues with the 17# injectors that was corrected with the 24# injectors. I think just the fact that I put in new injectors helps a lot versus 70k mile old injectors.

[Armo95]

I would agree with this with caveats.

If you have access to 93 octane or higher gas, by all mean the 17# injectors are fine. If you run donkey piss 91 octane MTBE ethamethahol here in California, you can benefit from the added buffer of being able to run slightly rich near the higher RPM's.

I personally had pinging issues with the 17# injectors that was corrected with the 24# injectors. I think just the fact that I put in new injectors helps a lot versus 70k mile old injectors.

Very true...I didn't take into consideration the octane rating Cali people have. I pump 94 all the time, so it's a little different for the Cali folks who pump 91.

[rmani]

I always pump 93. I do have 94 available too but do you really think it's worth the extra money? BTW I just got an email back from CSS...he recommends 24lb injectors, but how about some real world experience what are others on here running with basic bolt-ons??

[95cosmom3]

once again, cali is gay, i run 91 craptane... :rolleyes

[slcook54]

I running 24lb'ers with the Euro HFM and JC chip.

[rmani]

I running 24lb'ers with the Euro HFM and JC chip.

How's your fuel economy? Why did you choose the 24lb injectors? Custom tuning is gonna run a ton of money but if I can find a pre-programmed chip that works well I'd rather do that. Also did you install the JC chip yourself?

[RRSperry]

Of course you can find a preprogramed chip that runs well. JC's chip. I got the Conforti intake, HFM, and chip, (I still have the stock 17# injectors) for about $1100. Yea it was a lot of money, but it came quickly, was packaged well, had great instructions, and is proven to work. You just never know about a used HFM... Yes you can get the HFM (used), make an intake, and just buy the chip (about $250), I just didn't have the time.

If I do any more mods to the engine (cams, or the 96+ exhaust manifold), I will have to install 24# injectors and a matching chip.

[95DinanM3]

When I upgraded to the Euro HFM, I also installed a set a of 21.5 injectors for piece of mind. I only have access to 91 octane here and it seems that with all the extra air flowing through the larger HFM and throttle body, that the 17 were at pretty much their max duty cycle. In addition, the AA s/w I am using is tuned for them.

[RRSperry]

When I upgraded to the Euro HFM, I also installed a set a of 21.5 injectors for piece of mind. I only have access to 91 octane here and it seems that with all the extra air flowing through the larger HFM and throttle body, that the 17 were at pretty much their max duty cycle. In addition, the AA s/w I am using is tuned for them.


It wasn't for peace of mind, it was because the software was written for it. AA never wrote S/W for the 95. They did it for the 96+ with the 21.5# injectors. Then then burned a chip with that software, and said you had to use the other injectors.

Again, unless you track your car a lot, you don't need the bigger injectors unless/untill you add a trackpipe, headers, or cams. An intake, HFM and exhaust are fine.

[rmani]

It wasn't for peace of mind, it was because the software was written for it. AA never wrote S/W for the 95. They did it for the 96+ with the 21.5# injectors. Then then burned a chip with that software, and said you had to use the other injectors.

Again, unless you track your car a lot, you don't need the bigger injectors unless/untill you add a trackpipe, headers, or cams. An intake, HFM and exhaust are fine.

I do plan to add headers and a track pipe so maybe i'll go with the AA chip. How aggressive is their software compared to the Turner software?

[rmani]

Just talked to AA today and they said they can make me a custom chip for $350 but it's not upgradeable. Also they said their chip requires 21.5lb injectors (which I can get for relatively cheap) and it doesn't matter if you add headers, track pipe, and catback exhaust. What does everyone think? :help

[RRSperry]

I would think that installing headers, and a rack pipe would require another chip to get max performance out of them.

[Matt P.]

i dont think you need anything nlarger than 21.5lb unless your car is cammed, and even then you might not need em...

[rmani]

I thought 24 might be overkill unless the car got new cams as well, but I was suprised that the AA rep i spoke with said a full exhaust setup wouldn't affect what kind of chip they'd send me. I've heard conflicting info just hoping more people can chime in to give their real-world experiences.

[Balthazarr]

I bought an AA chip and I was told it was optimized for exhaust and intake...nothing about injectors was ever mentioned for my 95.

I have 98K on these so with larger HFM I should get the 21 lbs?

[rmani]

I bought an AA chip and I was told it was optimized for exhaust and intake...nothing about injectors was ever mentioned for my 95.

I have 98K on these so with larger HFM I should get the 21 lbs?


There seems to be a lot of discrepancy as to what's the optimal setup. Having done a good amount of research I think it's better to be safe than sorry and you should upgrade your injectors from the stock 17lbs if you're running the larger HFM and CAI.

[Balthazarr]

Don't have the HFM yet, just thinking about it.
Might ditch my URI cp.

[RRSperry]

In Balthazarr's case, he should get the # from the chip and then call AA. They can tell him is the chip needs the 21.5# injectors.

[Armo95]

I would think that installing headers, and a rack pipe would require another chip to get max performance out of them.

Exactly.

If AA told you that it's not necessary to get a reprogrammed chip for changing the exhaust, they are sorely mistaken. You're changing the VE of the car and anytime you do that, the mixture and optimal performance is hindered.

Headers and a track pipe WILL throw off your AF and in order for you to get the maximum benefit from these, you will need a chip programmed to operate with them. Especially the track pipe where you're ridding the cats and the car running very rich, specifically on the top end.