I think my 24 lb accel injectors are dropping out. I picked up some 50 lb SVO a while back for a steal. I have been tuning the car by burning chips. I made changes for the 24 lbs injectors when I put them in. Can I install the 50 lbs injectors and do the same thing? Thanks, BranZ

 

Steal?, then I'd have them flowed to make sure they are as advertised.

Depending on the injector, shouldn't be a problem. If they're some of the *punched out* ones, then maybe. What matters on the larger injectors, is how well they work at shorter pulse widths. If they go to dodo, there is just no way to compensate for an injector that gets erratic at short pulse widths.
FWIW, there's lots of Turbo V6s running large injectors, and have a 800 RPM idle in gear.

 

It takes aprox 1 ms for an injector to open. That can be a problem when you go to lean out idle and the PW starts to drop around 1ms. IMO, 50lbers are WAY to big if your 24lbers was not maxed. Even if the duty cycle was maxed you would have to make alot of power n/a to require 50lb injectors...

 

Shh, don't tell my 60 PPH, that tick away at .7msec at idle that they can't be doing that <g>.

Peak and Holds go down to .5msec just fine (usually).

More to life then WOT. The bigger the injector the *less* commanded AE you need. Not to mention the manifold type plays a huge role on how much AE you need.

 

You talking about low impedence injectors? Too bad they dont work with the factory MPFI puters...

 

TBIs are Peak and hold.
The Quad 4 wiring of the 749 is for P+Hs.

The conversion to run 8 P+Hs with the 749 has been public domained, the 1227148s are commercially available in P+H versions.

And with 60 PPH Saturated ones, commonly available, and while expensive there are even 90 and 105 (?) versions out there.

 

Grumpy,
when you say .7msec, are you talking .7msec commanded PW (neglecting the battery voltage offset, quasi-mode stuff, whatever) or .7 msec as scoped with an Oscope. If that's as scoped, I'm impressed - especially if it's saturated, and also in closed loop, and in park/nuetral, and actually achieving stoichiometric, and not leaking fuel in somehow else (to cover up for when the injectors don't fire). Are they normal injectors (big fat body) or are they new delphi picos (which have a huge dynamic range).

50's are big, especially when running 8 of them on a stock ish engine, but quasi-async will bring em right back down to 25s. You could also reduce the fuel pressure which will have the benefit of actually increasing it's flow rate (pressure/flow curve says so).

I wouldn't do it, unless that big is needed, but that's me.

Later,
Jeremy

 

I have a feeling if that IF it was me running a .7 PW, you would tell me why I shouldn't do that. So I'll flip it and as how/why you are doing that.(If you don't mind)....

Good stuff bout the quad 4, guess I've been sleeping

 

The 60 pph'ers he's using are from MotoTron, and are built into the narrow Siemens body. They're actually a product of Mercury Marine's offshore racing program.

Here's a pic (some vendors like to call 'em 65#'s)

http://www.precisionturbo.net/produc...oc=101&dealer=

It's been stated that these injectors perform especially well at shorter pulsewidths, compared to typical high-Z injectors.

I have a set sitting on my desk. Now, I just need to get my TTA reassembled....

 

Aha!
Knew there was a catch in there somewhere. I actually used a 11 pph version of the mercury injectors on the Iowa State Formula SAE car a few years back ('02 I believe). Never did get that engine running well though - crank reluctor problem, etc. on a DTA engine management system. They were free though. I wish I knew then what I know now about efi.

Speaking of too much injector - maybe - I just sent out a calibration to Mooneyes for a 16 injector setup on a 392 hemi. But, it's getting 16 19#/hr injectors, so that's about like 38 pph injectors. I just hope our ECU doesn't fry trying to pass 16 amps through it.

 

As read on the ALDL.
I've run 30s, 40s, 55s, and 60s on dat lil v6. The 55s were P+H, and run in batch fire as well as SEFI.

72s take running a 1,000 RPM because of PW issues, even in SEFI.

I run all I can cause of AE.

 

I was quoting a particular car, tuned a particular way. Up until I tried it, I wouldn't have suggested that short of PW being possible. It might not be universally true that they'll do that in every application. I was just stating it as an example, to point out the 1 msec to open statement.

 

Nice to see you are still learning!!!
Do you think there is anything that could happen running sub 1ms PW, like injector damage?