Hi Gang,
I am working on completing performance mods on a 10AE I bought recently. Got a surprise today and now have a question. First background; the car has

Atkins rebuild with street port
Microtech LTX12s controller
Racing Beat Rev TII Exhaust
MSD Blaster Ign coils
SX Performance 15404 FPR
Walbro GSS341 Fuel Pump
RC Engineering SL4-750 Secondary Injectors
Stock Denso 550cc Primary Injectors

Since i got the car, it has run painfully rich, and is inconsistant in general performance. Sometimes it runs like a bat out of hell. Other times, it'll dog down on a slight hill. Sometimes it bucks while cruising, but the bucking quits soon as I step on the gas. After hard acceleration, there has been flame coming out the tailpipes.

The problem: today, I stumbled on this forum - http://www.srtforums.com/forums/f187...ectors-421841/ - which says, in summary, that my secondary injectors are the only model from RC which has a max fuel pressure of 43psi. Since the Walbro builds a lot more pressure than that, I have two questions;

If the regulator is set too high for these secondaries, would that explain some of the issues such as the super rich mix and the intermittant bucking and maybe the flames?

Second, if they have been over-pressure driven would that cause permanent damage and I should therefore replace them while I have the top of the engine apart?

Thanks, as always, for your opinions and input

- kel -

 

The only case where a walbro will change fuel pressure on its own is with a stock FPR. Since you list an aftermarket FPR in your mods, you're not in that boat. Assuming you have a 1:1 rising rate FPR, the max fuel pressure will be whatever you set it to + the boost pressure you're running. Depending on the boost level, you probably have 50-55 psi max at the injectors. So if those injectors really are not intended for forced induction applications, you could very well have damaged them. On the other hand, I think I would call RC to verify this info.

Since the secondaries are only used under load & above a preset RPM, they shouldn't affect cruising or other low throttle/low RPM operation (unless they're leaking). The stock ECU doesn't fire the secondaries until -2 inHg vacuum and 3800 RPM; I don't know how your microtech is set, so maybe it's wildly different.

If the injectors are firing improperly, there's potential for a lean mixture under boost, which could blow the engine. But your description mainly sounds like an overly rich mixture. You should have a wideband in the car to check.

 

thanks for the input, Steve. You're right, that a primary symptom is running extremely rich - 12-13mpg in town. I'm suspicious that they may be leaking which would explain some of the other squirrely stuff it does.

So, a call to RC is next up.

- kel -

 

You should really get a wideband anyways though.

 

Actually, I have an Innovate LC-1 in hand. Installing it was the main incentive that got me this far. While working on this, I decided to confirm what was modified before I bought the car.

After further reading on the site, this thread has given me some ideas to pursue before I complete the LC-1 install and re-assembly of all the other stuff.

https://www.rx7club.com/showthread.p...&highlight=plx

This looks really nice. Further study is ahead to see if it would do the job for me.

- kel -

 

Who's steve? Not me.