Aux injectors activated by GPO possible?

[greasemonkee]

I hate the fact that these 750cc injectors have crap for atomization. I had been running stocks on the same system with the boost cut off. I was getting 36 mpg. Now I get about 30. This may not be possible but I was thinking of adding the stock injectors in the manifold and wired to a switching junction (relays in series) of some type. The GPO would activate the relays to switch from the 750's to the 240's and it would deactivate over x rpm/map. The injector settings would be way out, but would it possibly work just by altering the fuel values? The battery table would be out, but what other problems would I run into?

[calvin]

i did try something similar 2 sets of injectors and it didn't work good

[MADMAX]

Did you try messing with FV (final value)? I had my 750 RC's saturated injectors tucked away for awhile cause they sucked on Uberdata. I had to idle them at 12-13 AFR to get rid of the popping and studdering and pull a few degrees of timing at idle. With eCtune and the FV I start with a mostly stock map, input injector size and battery offset, and then keep adding to the FV until the cars idles and starts good. 750's idle better and start better than 450's did on CROME. I ended up at 35 I think.

[deluded]

i have boards that mount within the ecu adding 4 oem injector drivers slaved off the primary drivers. they are actived by any 5v GPO withing the ecu (transistor level). i used them for the edelbrock turbo kits that came with the extra fuel rail. we activated them with vtec so the vtec map had much lower values than usual. there was always a veryyyyy small hiccup at the x over, but it worked great. if you are interested we still have a few boards left. another idea is to make an obdI to obdI adapter with the inputs taken off for a second ecu that would be tuneable using only the injector outputs... this allows a tapering of the secondaries in with activation of the gpo. we are doing a similar set up right now for a secondary fuel system using methanol, but we're only using two additional injectors located near the IC outlet. there are a couple small hardware issues to deal with but it doesn't look too hard.

[HiProfile]

A real simple way to do this would be to use a 4PDT (4-pole relay, 2 position each). You can get mechanical units for $5-10 from digikey.com; I have a bunch, they are very nice. Mine in particular have a spec of 13 milliseconds to activate, 5A per contact. Deluded's boards no doubt work very fast, but I'm sure he wants more than $5 each. Anyways for the 4PDT, you would tie the coil in with the GPO, and connect the injectors in 2 different ways. Have the stockers always working, and the secondaries activate through the relay; or have the stockers working w/coil off & secondaries working w/coil on. I'd only do the latter if the activation point was in a low-power area, like 5 inHg or more. The only thing I'm unsure of is if you'd wire them in parallel or series if using both at the same time. With a cheap injector driver like the one for megasquirt (http://jbperf.com/p&h_board/index.html), I'd think series might be best. I will definately try this if I ever get a manifold with dual injectors.

[Bugermass]

on the RC750s I've found about 55 PSI of base fuel pressure seems to improve their performance..

[greasemonkee]

I would like to test the RC flow pattern in upwards of 55 psi. They (RC) claim they can handle up to 100 psi.

[Bugermass]

I usually run RC btween 55 and 60PSI, I did some testing with a couple N/A cars a while back with 40-45-50-55-60 PSI and the RC seemed to make best power at 55-60.. I'll look to see if I can find the dyno chart.