Hi Gang,
Looks like I'm going to have to replace the primary injectors. I have a pair of 550cc that are good (but unknown mileage) I could put in, but while the LIM 'nstuff is off, I wonder if I should just replace them with new and possibly larger.
Here's my setup now:

Atkins Street Port
Racing Beat TurboII 3"
Stock Turbo
550cc Primary
RC Engineering 750cc Secondary
Walbro pump
Aeromotive FPR
Microtech LTX12s
Innovate LC-1 wideband

So my question: what would you do?

New RCEng 750cc?
New RCEng 550cc?
New RCEng something larger?
New somebody else's something else?
Something else?

Going for 300+ HP goal.

- kel -

 

300+ at the flywheel or rear wheels?

550 + 720+ for 300 flywheel
720 + 720+ for 300 wheel

 

At wheel. So would you go with RC 720s? Or another mfg?


- kel -

 

I don't really care about who makes them as long as they flow what they are rated for.

 

Thanks! I appreciate your input

- kel -

 

If you're sticking with the stock turbo, you'll only need 720 or 750cc secondaries. The 720s I use are a pair of Greddy/Denso injectors. They're a little expensive, but they're quality parts. I just switched out my injectors in preparation for a hybrid turbo, but the 550/720cc setup was operating at 73% duty cycle max & 11.5 AFR with the stock turbo giving it all it had.

 

Actually, I already have 750cc secondaries. It's the primary injectors I'm going to replace and was contemplating replacing them with 750s instead of 550 as they are now.

With stock turbo, you say I won't gain by increasing the primary size? A turbo upgrade could be in the future, but for now, I need to stay with the stock unit.

THX


- kel -

 

As long as you're staging the secondaries at about 3500 RPM or lower, 550cc primaries will not max out before the secondaries come online. If using the stock 3800 RPM switch point, they will hit max duty cycle and cause a small lean spot with elevated boost levels. And as far as total fuel delivery, 550/750 will be more than the stock turbo needs.

If you're wanting to go bigger for later upgrades, you'll probably be better off just using larger secondaries with the 550cc primaries. If you leave the primaries alone, you won't have to adjust as much of the fuel map. Idle, start up and the vacuum parts of the map will be affected by increasing primary size.

 

Thanks,000,000 for all that. It makes good sense, and I will order new 550s today. It really isn't *that* hard to pull the UIM, so I'll just upgrade the secondaries when the time comes. Could be when I get this thing tuned correctly and all the gremlins banished it may be as fast a car as I'll want anyways.

Thanks again for your thoughtful replies.


- kel -